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Self-Guided WheelchairMAY07-15Design Report

Version 2.0

Client: Andrew Dove

Faculty Advisors: Dr. Nicola Elia

Team Members: Tara SpodenBrian YaukMargaret ShangleVee ShinatrakoolJohn Volkens

DISCLAIMER: This document was developed as a part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.

Submitted: Wednesday, December 6, 2006

http://www.ni.com/

DESIGN REPORT SELF-GUIDED WHEELCHAIR

Table of Contents1 List of Figures........................................................................................................................................................iii

2 List of Tables.........................................................................................................................................................iv

3 List of Definitions..................................................................................................................................................vi

4 Executive Summary................................................................................................................................................1

5 Introductory Materials............................................................................................................................................2

5.1 Acknowledgement..........................................................................................................................................25.2 Problem Statement..........................................................................................................................................2

5.2.1 General Problem Statement....................................................................................................................25.2.2 General Solution Approach.....................................................................................................................2

5.3 Operating Environment...................................................................................................................................35.4 Intended Users and Uses.................................................................................................................................3

5.4.1 Users.......................................................................................................................................................35.4.2 Uses.........................................................................................................................................................4

5.5 Assumptions and Limitations.........................................................................................................................45.5.1 Assumptions............................................................................................................................................45.5.2 Limitations..............................................................................................................................................5

5.6 Expected End Product and Other Deliverables...............................................................................................6

6 Proposed Approach.................................................................................................................................................8

6.1 Design Objectives...........................................................................................................................................86.2 Functional Requirements................................................................................................................................96.3 Constraint Considerations...............................................................................................................................96.4 Technology Considerations............................................................................................................................9

6.4.1 Selection Criteria..................................................................................................................................116.4.2 Microprocessor Hardware.....................................................................................................................11

6.4.2.1 Technology Considerations................................................................................................................................126.4.2.2 Selected Approach..............................................................................................................................................16

6.4.3 Microprocessor Software......................................................................................................................166.4.4 Ranging Modules..................................................................................................................................16

6.4.4.1 Technology Considerations................................................................................................................................166.4.4.2 Selected Approach..............................................................................................................................................20

6.4.5 Orientation Sensors...............................................................................................................................216.4.5.1 Technology Considerations................................................................................................................................216.4.5.2 Selected Approach..............................................................................................................................................22

6.4.6 Distance Tracking Sensors....................................................................................................................226.4.6.1 Technology Considerations................................................................................................................................236.4.6.2 Selected Approach..............................................................................................................................................23

6.4.7 Localization...........................................................................................................................................236.4.7.1 Technology Considerations................................................................................................................................246.4.7.2 Selected Approach..............................................................................................................................................28

6.4.8 Motor Control.......................................................................................................................................286.4.8.1 Technology Considerations................................................................................................................................296.4.8.2 Selected Approach..............................................................................................................................................31

6.4.9 Power Management..............................................................................................................................326.4.9.1 Technology Considerations................................................................................................................................326.4.9.2 Selected Approach..............................................................................................................................................33

6.4.10 User Interface........................................................................................................................................336.4.10.1 Technology Considerations............................................................................................................................33

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6.4.10.2 Selected Approach.........................................................................................................................................376.5 Testing Requirements...................................................................................................................................38

6.5.1 Microprocessor.....................................................................................................................................386.5.1.1 Hardware............................................................................................................................................................386.5.1.2 Software..............................................................................................................................................................38

6.5.2 Sensors..................................................................................................................................................386.5.2.1 Ranging Module.................................................................................................................................................396.5.2.2 Orientation..........................................................................................................................................................39

6.5.3 Localization...........................................................................................................................................396.5.4 Motor Control.......................................................................................................................................406.5.5 Power Management..............................................................................................................................406.5.6 User Interface........................................................................................................................................416.5.7 System Integration................................................................................................................................41

6.6 Project Continuation.....................................................................................................................................426.7 Detailed Design.............................................................................................................................................42

6.7.1 General Overview.................................................................................................................................426.7.2 Microprocessor.....................................................................................................................................44

6.7.2.1 Hardware............................................................................................................................................................446.7.2.2 Software..............................................................................................................................................................45

6.7.3 Sensors..................................................................................................................................................486.7.3.1 Ranging Module.................................................................................................................................................486.7.3.2 Orientation..........................................................................................................................................................51

6.7.4 Localization...........................................................................................................................................536.7.5 Motor Control.......................................................................................................................................566.7.6 Power Management..............................................................................................................................586.7.7 User Interface........................................................................................................................................606.7.8 Design Summary...................................................................................................................................61

7 Estimated Resource Requirement.........................................................................................................................62

7.1 Personnel Requirements................................................................................................................................627.2 Other Resources............................................................................................................................................647.3 Financial Requirements................................................................................................................................64

8 Schedules..............................................................................................................................................................66

9 Project Team Information.....................................................................................................................................69

10 Closing Summary..............................................................................................................................................70

11 Appendix A.......................................................................................................................................................71

12 Appendix B.......................................................................................................................................................73

13 Appendix C.......................................................................................................................................................74

14 Appendix D.......................................................................................................................................................76

15 References.........................................................................................................................................................78

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List of Figures

1 List of Figures

Figure 5.1 – Basic System Block Diagram.....................................................................................................................3Figure 6.1 – Technology Selection Process..................................................................................................................10Figure 6.2 – System Flow Diagram..............................................................................................................................43Figure 6.3 – Wheelchair System Diagram....................................................................................................................43Figure 6.4 – System Mounting Diagram.......................................................................................................................44Figure 6.5 – Controller Connection Block Diagram.....................................................................................................44Figure 6.6 – General Program Flow.............................................................................................................................46Figure 6.7 – SRF04 Timing Diagram ..........................................................................................................................49Figure 6.8 – SRF04 Beam Pattern ...............................................................................................................................49Figure 6.9 – Ranging Module Mounting Arrangement................................................................................................50Figure 6.10 – Ranging Module Mapping in a Hallway................................................................................................51Figure 6.11 – R117 Compass Timing Diagram ...........................................................................................................52Figure 6.12 – RFID Tag Placement..............................................................................................................................53Figure 6.13 – APSX RW-310 RFID Reader/Writer Module and Transponders..........................................................54Figure 6.14 – Computer to RFID Reader......................................................................................................................55Figure 6.15 – Invacare Arrow Joystick Schematic.......................................................................................................56Figure 6.16 – Controller to Joystick Connection Diagram...........................................................................................57Figure 6.17 – 5VDC System.........................................................................................................................................58Figure 6.18 – 9VDC System.........................................................................................................................................58Figure 6.19 – 6VDC to 5VDC......................................................................................................................................59Figure 6.20 – LCD Character Displays ........................................................................................................................61Figure 8.1 – Fall 2006 Task Schedule (Original).........................................................................................................66Figure 8.2 – Fall 2006 Task Schedule (Revised)..........................................................................................................66Figure 8.3 – Spring 2007 Task Schedule (Original).....................................................................................................67Figure 8.4 – Spring 2007 Task Schedule (Revised).....................................................................................................67Figure 8.5 – Full Project Reporting and Deliverables Schedule (Original)..................................................................67Figure 8.6 – Full Project Reporting and Deliverables Schedule (Revised)..................................................................68

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List of Tables

2 List of Tables

Table 5.1 – Project Assumptions....................................................................................................................................4Table 5.2 – Prototype Assumptions................................................................................................................................5Table 5.3 – Project Limitations.......................................................................................................................................6Table 6.1 – CMD565 Evaluation Board ......................................................................................................................12Table 6.2 – Handy Board .............................................................................................................................................13Table 6.3 – EPIC AMD Gode GX2 .............................................................................................................................14Table 6.4 – VIA EPIA-EN12000EG Mini-ITX ...........................................................................................................15Table 6.5 – Controller Technology Comparison..........................................................................................................16Table 6.6 – SRF04 Sonar Sensor .................................................................................................................................17Table 6.7 – SRF235 Sonar Sensor ...............................................................................................................................17Table 6.8 – SensComp 6500 Sonar Sensor ..................................................................................................................18Table 6.9 – Sharp GP2D05 IR Ranger .........................................................................................................................18Table 6.10 – Sharp GP2Y0A02YK IR Sensor .............................................................................................................19Table 6.11 – R283-HOKUYO Laser Sensor ...............................................................................................................20Table 6.12 – Ranging Module Technology Comparison..............................................................................................20Table 6.13 – Devantech R117 Magnetic Compass ......................................................................................................21Table 6.14 – ADXRS150 Angular Rate Sensor ...........................................................................................................22Table 6.15 – Orientation Technology Comparison.......................................................................................................22Table 6.16 – MA2 Miniature Absolute Magnetic Shaft Encoder ................................................................................23Table 6.17 – Distance Tracking Technology Comparison...........................................................................................23Table 6.18 – Off-board Track Localization..................................................................................................................24Table 6.19 – Dead Reckoning Localization..................................................................................................................26Table 6.20 – Tactile Detection Localization.................................................................................................................26Table 6.21 – RFID Localizatoin...................................................................................................................................27Table 6.22 – Sonar Imaging Localization.....................................................................................................................27Table 6.23 – Localization Technology Comparison.....................................................................................................28Table 6.24 – ADAC0808 8-Bit D/A Converter ...........................................................................................................30Table 6.25 – Custom D/A Converters...........................................................................................................................30Table 6.26 – Control Box Connection..........................................................................................................................31Table 6.27 – Joystick Connection.................................................................................................................................31Table 6.28 – Motor Control Technology Comparison..................................................................................................32Table 6.29 – Trident GPA 400 PIN Keypad ................................................................................................................34Table 6.30 – Targus USB Numeric 19-Key Mini Kepad ............................................................................................34Table 6.31 – Kensington Pocket Keypad .....................................................................................................................35Table 6.32 – Phidget Text LCD ...................................................................................................................................36Table 6.33 – Mini-Box picoLCD .................................................................................................................................36Table 6.34 – Optrex TM1B5BW Touchscreen ............................................................................................................37Table 6.35 – User Interface Technology Comparison..................................................................................................37Table 6.36 – Wheelchair Testing Form........................................................................................................................40Table 6.37 – EPIA-EN12000EG Mini-ITX Features...................................................................................................45Table 6.38 – SRF04 Technical Specifications .............................................................................................................48Table 6.39 – SRF04 Pin Connections ..........................................................................................................................48Table 6.40 – R117 Compass Technical Specifications.................................................................................................51Table 6.41 – R117 Compass Pin Connections .............................................................................................................52Table 6.42 – ADXRS150 Gyroscope Technical Specifications ..................................................................................53Table 6.43 – RW-310 RFID Reader/Write Module Features.......................................................................................55Table 6.44 – Digital Output Mapping to Motor Control (Forward/Reverse)...............................................................57Table 6.45 – Digital Output Mapping to Motor Control (Left/Right)..........................................................................58

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Table 6.46 – 9V Energizer Battery Specifications........................................................................................................59Table 6.47 – AA Energizer Battery Specifications.......................................................................................................60Table 6.48 – Evaluation of Design Functionality.........................................................................................................61Table 7.1 – Estimated Person Hours (Original)............................................................................................................62Table 7.2 – Estimated Person Hours (Revised)............................................................................................................63Table 7.3 – Other Resource Requirements...................................................................................................................64Table 7.4 – Material and Labor Costs (Original)..........................................................................................................64Table 7.5 – Material and Labor Costs (Revised)..........................................................................................................65

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List of Definitions

3 List of Definitions

CPU.........................................................(central processing unit) programmable logic device that performs all the instruction, logic, and mathematical processing in a computer

DAC or D/A............................................(digital to analog converter) electronic device that is used to convert digital signals into analog signals

DC...........................................................(direct current) unlike alternating current (AC), the flow of current is constant in one direction

EEPROM................................................(electrically erasable programmable read only memory) rewriteable form of memory that is non-volatile, meaning that the device does not need a supply of power in order to retain the memory

Infrared...................................................electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum, from 760 nanometers to 1000 microns

LabVIEW Embedded..............................graphical programming language developed by National Instruments for implementation on OEM hardware

LCD........................................................(liquid crystal display) display that consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between

Microprocessor.......................................silicon chip with thousands of electronic components that serves as the CPU in microcomputers

OEM.......................................................(original equipment manufacturer) original manufacturer of a hardware component or sub-component

PWM.......................................................(pulse width modulator) type of circuit that holds the frequency constant while the width of power pulse is varied, and controls both line and load changes without major dissipation

RF...........................................................(radio frequency) frequency that lies in the range within which radio waves may be transmitted, from about 10 kilohertz per second to about 300,000 megahertz.

Sonar.......................................................(sound navigation and ranging) distances to objects are determined by bouncing sound waves off them and measuring the time it takes for the echo to return

Transponder............................................radio transmitter-receiver activated for transmission by reception of a predetermined signal. An RF reader/transmitter sends a signal via radio waves in order to detect transponders designed to read that reader’s particular frequency signal.

USB.........................................................(universal serial bus) external peripheral interface standard for communication between a computer and external peripherals over a cable using bi-serial transmission

VI............................................................(virtual instrument) file containing subroutines or subfunctions created in LabVIEW

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Executive Summary

4 Executive Summary

The system designed in this project is a wheelchair that has the ability to navigate autonomously through a hospital environment while avoiding obstacles incurred along the desired route. Certain limitations, constraints outside of the control of the team, and assumptions, constraints defined by the team, have been identified in order to ensure a manageable project. These considerations include constraints on the operating environment such as floor surface, the physical and mental capabilities of the user, budget, physical dimensions, power requirements, and overall scope of the project. Functional requirements further define the autonomous navigation and obstacle avoidance in terms of navigation from and to predefined locations, recalculating routes in instances of impassible obstacles, continuing navigation on reasonably shallow ramps.

A floorplan map modeled after the actual environment will be programmed into the Mini-itx controller prior to operation. Within this map, several predetermined coordinates will be selected as the possible waypoints to be used as the start and destination points. Also included in this map, will the location of waypoints intended for localization purposes. The MPC565 will be programmed using LabVIEW Embedded 8.2 as requested by the client, National Instruments.

Operation will begin with user input of the wheelchair’s current location as the starting point and the desired destination as the ending point. Using a keypad with unique keys for each of the possible waypoints and an LCD display, the user will select the start and end point of the wheelchair navigation. A keypad and LCD were chosen as the best options for user interface because they are inexpensive and easily interfaced with the evaluation board.

An algorithm for path calculation will begin upon receipt of the starting and ending point of navigation. The path will be generated from the initial floorplan, assuming only preprogrammed obstacles. During travel, additional obstacles may be added into the map when detected. Using multiple ultrasonic sensors positioned around the perimeter of the wheelchair, the distance from the wheelchair to physical objects in the environment will be calculated from the sensor feedback. The distances will be used in the microprocessor to decide which directions are safe for travel and free of obstructions. This method for object detection was chosen because the ultrasonic sensors offer the necessary range of obstacle detection for a reasonable price.

In addition to the information from the ultrasonic sensors, the microprocessor will receive data from a compass and gyroscope in order to track the trajectory of the wheelchair. As data from the ultrasonic sensors arrive and the initial path is determined to be obstructed, the additional sensors will allow for calculating the deviation from the original path. An educated estimate of the current location can then be constructed for use during path recalculation. This collection of sensors was decided upon based on their ability to provide the necessary accuracy for this project and due to the fact that a gyroscope was incompatible with the operation of system, specifically wheel slippage.

The localization technology to be implemented in the system is a fixed beacon method based on RFID. A reader will be connected into the system which will identify RFID tags that have been strategically placed through the operating environment. This method of localization was chosen because of its cost-effectiveness compared to other localization technologies.

The motor control of the wheelchair will be realized by converting the digital output of the controller into an analog signal which can be sent into the existing joystick. This method for was deemed acceptable for the prototype design as technical information on the motor control box was unavailable from the manufacturer.

The end-product of this project will be a physical prototype which will demonstrate basic navigational capabilities. Due to the complexity and scale of this project, the tasks have been divided into smaller, manageable sections of planning, development, testing and documentation. A schedule has been constructed with milestones signifying the conclusion of each section to ensure successful completion within the two semester timeframe of senior design. The resource requirements and expected team member hourly contributions were included in the development of this schedule.

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Introduction5 Introductory Materials

The following material gives an overall summary of current problematic situation, as well as an overview of the proposed system solution, complete with expected deliverables of the project.

5.1 Acknowledgement

The May07-15 Design Team would like to thank several resources for information and materials in relation to this project: National Instruments for their donation of LabVIEW Embedded 8.2 software, the CMD565 evaluation board and microprocessor, as well as, advanced technical support; Invacare for their donation of a joystick and wheelchair control box; and Iowa State University for the use of a motorized wheelchair for the duration of the project.

5.2 Problem Statement

The section addresses and outlines the general solution approach.

5.2.1 General Problem Statement

Many people encounter an instance in their life where a disability causes them to be confined to a wheelchair. When transport is required, the wheelchair is often physically manned, either by the person in the wheelchair or someone behind it. When someone is needed to push the wheelchair, the independence of the person confined to the wheelchair is limited to the schedule and convenience of an outside source.

Especially in hospital environments, these persons confined to wheelchairs need to move frequently, for appointments in multiple departments and general relocation from room to room. In the absence of family and friends, the assistance required for persons in wheelchairs creates a burden on the already confined schedules of the staff. As a result, patients are subject to waiting until aid is of convenience.

5.2.2 General Solution Approach

The system proposed for this project is a wheelchair that has the ability to navigate autonomously through a hospital while avoiding obstacles. Using a microprocessor programmed with LabVIEW Embedded 8.2 and interfaced with user input devices, the wheelchair user will be able to select, from one of several locations, their starting and ending point.

Travel of a motorized wheelchair will be initiated and controlled by the microprocessor. Positioning sensors will interface with the microprocessor to indicate location and distance traveled. During travel, additional sensors mounted on the wheelchair will transmit environmental data such as distance to surround objects to the microprocessor. Incurred obstacles will prompt an obstacle avoidance algorithm to attempt to navigate around the obstacle and recalculate paths.

The block diagram in Figure 5.1 demonstrates the basic system solution interface.

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Figure 5.1 – Basic System Block Diagram

5.3 Operating Environment

The system will be designed for use in an indoor medical hospital setting. The prototype to be designed during the project will be designed only for operation on a single floor level, free of stairs or similar large drop-offs. The floor surface should be a common hospital floor type, such as tile, hardwood, or short carpet. The environment should be typically for motorized wheelchair operation and yield itself to a mobile wheelchair system.

5.4 Intended Users and Uses

The system is designed to accommodate the users and uses outlined in the following sections.

5.4.1 Users

There are two possible classes of users for this wheelchair: a primary user (operator), and a secondary user (passenger).

Primary UserThe primary user must be able to interact with the system to provide the appropriate location information for the system input. At a minimum, the primary user must have the mental and physical capability to provide the current location and desired destination of the wheelchair via a simple keypad, which will require shape recognition and basic literacy. In instances where the passenger lacks this mental or physical capacity, they become the secondary user, and the primary user is regarded as the medical staff or guardian providing the input.

Secondary UserThe secondary user, as mentioned, is regarded as the passenger that will be transported via the wheelchair to the specified destination. At a minimum, this user must be able to maintain a seated position within the confines of the chair dimensions, but no further physical or mental functions are specifically required. It is assumed that the

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secondary user will primarily be a patient who is unable to maintain proper control of a wheelchair due to mental of physical disabilities.

(Note: There may be one person who qualifies as both the primary and secondary user if the wheelchair passenger is capable of providing the location input.)

5.4.2 Uses

The system is designed for use in an indoor medical hospital or nursing home setting on one floor level. Other locations similar to an indoor medical hospital may provide an adequate for system operation, such as a residential home or office building, but are not explicitly covered by the system.

The system will navigate from one of any number of pre-selected locations to one of any number of pre-selected destinations, as specified by the primary user, if a reasonable path exists. The wheelchair will attempt to traverse an initial path calculated by the system while avoiding any incurred obstacles (both moving and stationary). If the current path is deemed impassable due to obstacles, the system shall attempt to navigate alternate. If all reasonable paths are judged impassable, the system will discontinue movement and signal that it is unable to proceed.

The system will be able to traverse reasonably shallow ramps or other such gradual changes in plain elevation, in the absence of large drop-offs. In order to obtain operation on another floor level, an outside user shall be required manually relocate the system.

5.5 Assumptions and Limitations

The operation of the system is constrained by the assumptions and limitations described in the following sections.

5.5.1 Assumptions

Certain elements were defined by members of the design team which attempt to further quantify the scope of the project. The list contained in Table 5.1 summarizes the general assumptions used during the system conceptualization and the justification for each.

Table 5.1 – Project AssumptionsAssumption Justification

The floor shall be a common floor type, typical to electronic wheelchair navigation.

Operational Requirement

The navigation shall be applicable to hospital environments.

Design Requirement

The primary user shall have the physical and mental capabilities to interact with the input system.

Design Requirement

The team shall have administrative access to load software/hardware on senior design workstations.

Testing Requirement

The complexity of this project warrants assumptions for the prototype as well as the overall design. In order to ensure a manageable prototype to be implemented within the timeframe of senior design, the additional assumptions in Table 5.2 have been specified by the team.

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Table 5.2 – Prototype AssumptionsAssumption Justification

The environment shall consist of a single floor level and no open drop-offs, such as stairs.

Design Requirement

The navigation shall be applicable to hallway environments, such as those on third floor Town Engineering.

Design Requirement

The team shall be provided with a motorized wheelchair in working condition.

Design Requirement

The system shall travel and detect obstacles, at least, in the forward direction during autonomous navigation.

Design Requirement

The system shall travel to one and only one destination at a time without intermediate waypoints.

Design Requirement

The localization technology of the wheelchair shall be attainable within the existing project budget.

Design Requirement

5.5.2 Limitations

Additional elements of the project were identified as design restrictions which are beyond the control of the team members. The list contained in Table 5.3 summarizes the limitations acknowledged during the system conceptualization and the justification for each.

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Table 5.3 – Project LimitationsLimitation Justification

The budget for the development the project shall not exceed $1150.

Design Requirement

The placement of the components shall not interfere with the mobility or passenger accommodation of the wheelchair.

Operational Requirement

All hardware shall be secured to the existing wheelchair frame or remain stationary within the operational environment.

Design Requirement

The hardware shall interface to the microprocessor through the use of LabVIEW Embedded 8.2.

Client Requirement

The system shall only be required to navigate between predefined locations.

Design Requirement

The localization technology of the wheelchair shall be attainable within the existing project budget.

Design Requirement

5.6 Expected End Product and Other Deliverables

There are two expected end products of this project. The first is a complete design report, and the second is a prototype of this design implementing the most pertinent components. In addition to the end products, there are two additionally required deliverables, the project plan and final report.

Project PlanThe project plan is a document that defines that project and the plan for the completion of the project. It describes how design decisions were made for the project and defines the overall problem domain. This document was delivered in October of 2006.

Design ReportThe design report is a document describing the full design of the system. As this project will not require outside funding, it will specify the details of the complete system: the schematic designs, component layouts, software design, and hardware specifications. It is intended to provide all the details necessary for replication of the project by an independent team. This document will be delivered in November of 2006.

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PrototypeThe prototype of the self-guided wheelchair system specified by the design documentation will be assembled and presented to the client. Since a complete system would require extensive funding, the prototype will be limited to the components of the design which demonstrate the basic, required navigational capabilities in a controlled environment and suggest further capabilities with the additional improvements and hardware. The team will assemble and test the equipment to verify proper autonomous navigation. This system will be delivered in May of 2007.

Final ReportThe final report will be a document that provides the most complete description of the project along with a detailed record of its development. All aspects of the project, including the background development, testing, and end product description, will be covered in this document. This document will also provide suggestions for future work on the project. This document will be delivered in May of 2007.

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Proposed Approach

6 Proposed Approach

The following material reiterates the requirements of the project and discusses the considerations included in the design of the system. This will include the functional requirements, constraints, technical considerations, testing and overall objectives. The purpose of this material is to clearly describe the components which will lead to a successful end product.

6.1 Design Objectives

The objective of this design is to solve transportation issues of a person confined to a wheelchair within a hospital environment. In order to successfully address the issues of concern with this problem, the project will be designed such that it meets the design objectives described in this section.

Autonomous navigationThe navigation of the wheelchair should be independent of user input, other than the starting and destination point. Turning corners, traversing straight and diagonal paths should all be controlled by the onboard processing unit with the aid of distance sensors, a compass, and a gyroscope.

Obstacle avoidanceThe navigation of the wheelchair shall attempt to avoid any obstacle incurred in the intended path. In situations where it is easily possible to navigate around the obstacle, the wheelchair should attempt to continue towards its destination. In situations where continuation is not easily possible, the wheelchair should terminate navigation and signal an alarm to notify the user that path is blocked.

User interfaceThe user interface should be a visual, intuitive design which allows the selection of a starting point and destination point. The interface should also offer options for commencing and terminating operation. If time permits, visual indicators for direction of travel or detected obstacles may be implemented.

Reliable operationThe system should be designed to operate reliably for a few hours of operation in order to insure project feasibility. The navigation must be able to traverse a fairly smooth path free of sudden changes in direction or erratic movements. Smooth navigation will help ensure the safety and comfort of the passenger.

Ease of useSimplicity of the system is an important factor in the marketability of the end product. The system must be easy to use with a small learning curve to ensure that hospital staff is not overwhelmed by implementation of the system, especially as the solution is meant to reduce their workload.

Low costComparable autonomous navigations systems can be implemented for thousands, to tens and hundreds of thousands, of dollars. The system designed in this project should be attainable with components whose total purchase price is less than $1150, the project budget.

6.2 Functional Requirements

The complete system has the following functional requirements:

Basic function

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The system shall autonomously traverse from one of several predetermined locations to one of several predetermined destinations, indicated by the primary user, if a reasonable path exists.

NavigationThe following list quantifies the requirements for the traversal of the system:

The system shall calculate a path from the specified starting point to the specified ending point which is considered to be a direct route, although not constrained to be the absolute shortest route.

The system shall attempt to travel on this predetermined path while avoiding both moving and stationary obstacles presiding in the path.

If the current path is deemed impassable, due to an obstacle or closed door, etc, the system shall attempt to calculate alternate routes.

If all reasonable paths seem impassable, the system shall indicate that it is unable to continue navigation. The system shall not attempt to traverse any stairwell, escalator, or other surface or area that is seemingly

non-adjoining surface to the plain that the system is currently on. The system will be able to traverse reasonably shallow ramps or other such gradual changes in plain

elevation.

6.3 Constraint Considerations

The following list specifies the restrictions on the complete system as deemed appropriate by team consensus or the laws of physics:

The floor shall be a common floor type, typical to electronic wheelchair navigation. The environment shall consist of a single floor level and no large drop-offs. The primary user shall have the physical and mental capabilities to interact with the input system. The secondary user shall be of physical dimensions accommodated by wheelchair and be capable of

maintaining a seated position during travel. The team shall be provided with a motorized wheelchair in working condition. The system shall only be required to navigate between predefined locations. The system shall travel to one and only one destination at a time without intermediate waypoints. The budget for the development the project shall not exceed $1150. The placement of the components shall not interfere with the mobility or passenger accommodation of the

wheelchair. All hardware shall be secured to the existing wheelchair frame or remain stationary within the environment. The hardware shall interface to the microprocessor through the use of LabVIEW Embedded 8.2. The prototype design shall be limited to that which is accomplishable based on budget and time.

6.4 Technology Considerations

This section contains a very detailed description of the methods used to identify, evaluate and select the technology used for the design of this system. The scope of this project demands that the technical details be divided into manageable parts; therefore, this section, as well as the remaining sections of this document, will describe details as they pertain to the following categories: processing, obstacle detection, localization, power management, and user interface. Using the process outlined in Figure 6.2, the solution alternatives addressed in this section were identified, evaluated and selected. While the testing phase has begun, final verification is still in progress.

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Figure 6.2 – Technology Selection Process

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6.4.1 Selection Criteria

The selection of each component was based on the following criterion:

CapabilityThis takes into account how well the system can handle the tasks demanded of it according to its functional requirements. This will also take into account physical dimensions as space is limited for mounting on the wheelchair. This category has the most weight as the technology must be capable of handling the necessary tasks.

Ease of implementationThis takes into account how much effort would be needed to coordinate interfacing with the other components in the system and the ease of running all required tasks. This category has the second highest amount of weight as the technology must be able to be implemented in the given time frame, with readily available knowledge.

CostThis takes into account how much the component will actually cost to purchase, set up, and the associated labor. This category has the third highest amount of weight as the technology must be able to be implemented within the cost constraints of the project.

DurabilityThis takes into account how well the component will withstand vibrations on the wheelchair or possible abuses from the operator.

Ease of useThis takes into account how feasibly the component can be implemented into a commercial product where a learning curve may be associated with the programming and/or maintenance.

6.4.2 Microprocessor Hardware

The functionality requirements for the microprocessor include the ability to:

Receive data from the selected sensors and localization technology Interpret data from sensors into an area mapping Receive input from the user interface Transmit commands to the motor control Transmit status indicators to the user interface Perform path calculation and obstacle detection Operate on LabVIEW Embedded 8.2

Since a solitary microprocessor would not be sufficient, considerations of microprocessors were done in the form of a microcontroller starter kit. The client offered two alternatives for consideration, both of which were suitable for LabVIEW Embedded 8.2 environment:

1.) Motorola MPC565 microprocessor with Axiom CMD565 evaluation board2.) Motorola 68HC11 microprocessor with Handy Board

However, in order to do the complex calculations and mapping required for an onboard map and obstacle avoidance, significant memory must be available. Neither of the microcontroller kit alternatives offers a large memory option, therefore the capability of the prototype is severely limited. The suggestion of this team for commercialization of this project is to design a custom board with sufficient external memory interfaced to the microprocessor, as well as, serial connection, digital, and ADC ports. Therefore, two further possibilities were considered for solving issues with the proposed microprocessors:

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3.) PC104 form factor EPIC AMD™ Geode GX2 Low Power Single Board Computer4.) VIA EPIA-EN12000EG Mini-ITX Motherboard

6.4.2.1 Technology Considerations

The functionality requirements of the microprocessor dictate that technology considerations include the types and number of available I/O ports, available memory types and size, software usage, as well as power specifications for power management considerations.

Table 6.4 highlights the important features of the CMD565 evaluation board. A full list of the CMD565 specifications can be found in Appendix A.

Table 6.4 – CMD565 Evaluation Board [1]Axiom CMD565 Evaluation Board

Pros On board memory in additional to internal memory

Ports for external LCD and Keypad Multiple I/Os for ADC, digital inputs, etc Low cost (provided by NI) 32-bit microprocessor Compatibility with LabVIEW Embedded 8.2

Cons Large size (8 x 9.5 in) Non-expandable, limited memoryo 4MB (onboard) + 1032KB (internal) Flasho 2MB (onboard) + 36KB (internal) RAM

Micro attached via springs/compression

Cost $0 (Donated by NI)

Table 6.5 highlights the important features of the Handy Board. A full list of the Handy Board specifications can be found in Appendix B.

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Table 6.5 – Handy Board [2]Handy Board


Built in 2-line LCD display Analog, digital and DC motor I/Os Compatibility with LabVIEW Embedded 8.2 Many support sites and examples of use

available Soldered-on micro Compact size

Cons Limited memory o 512 KB (internal) Flash o 32 KB (onboard) + 512 KB (internal) RAM

8-bit microprocessor Higher cost

Cost $299 [3]

Table 6.6 highlights the important features of the EPIC AMD Gode GX2. A full list of the EPIC AMD Gode GX2 specifications can be found in Appendix C.

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Table 6.6 – EPIC AMD Gode GX2 [4]EPIC AMD Gode GX2


Ports for external LCD and Keypad Multiple I/Os for ADC, digital inputs, etc 32-bit microprocessor Compatibility with LabVIEW Embedded 8.2 Compact size (90 mm by 96 mm) Component architecture is adaptable

Cons Highest cost No software backbone Higher level of integration using the PC104 form

factor

Cost $675

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Table 6.7 highlights the important features of the VIA EPIA-EN12000EG Mini-ITX. A full list of the VIA EPIA-EN12000EG Mini-ITX specifications can be found in Appendix D.

Table 6.7 – VIA EPIA-EN12000EG Mini-ITX [5]VIA EPIA-EN12000EG Mini-ITX

Pros Multiple Peripheral I/O Large amount of memory and computing power Small power usage (12W to 15W max) Fully supports PC software Small size (170mm by 170mm) Compatibility with LabVIEW Embedded 8.2 Low cost for a Single Board Computer Efficient and stable Expandable Runs on ATX power supply which integrates into

system design well

Cons Not as many general I/O ports for sensor interface

Cost $226.95

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6.4.2.2 Selected Approach

Based on the criterion described in the previous section, Table 6.8 summarizes the controller evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.8 – Controller Technology Comparison

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TotalCMD565 Eval Board 3 4 5 3 3 10

Handy Board 2 2 2 4 4 15

Geode GX2 4 2 1 4 2 15

Mini-ITX 5 5 3 5 5 22

The VIA EPIA-EN12000EG Mini-ITX board was chosen as the best controller for the project as it scored at 22 out of a possible 25 points. This hardware best fits the criteria requirements as it offers the most functionality with best use of development time, though it is still limited with general I/O connections. The cost associated with option comparatively small due to the current project needs. Although larger in size than the Geode GX2 and the Handy Board, it is still relatively small enough to fit on the chair. The VIA EPIA-EN12000EG is a member of a newly-used embedded form factor specification called Mini-ITX, as it combines the usability and extensibility of a PC architecture into an embedded system, and is finding its place nicely amongst more aged options.

6.4.3 Microprocessor Software

A requirement of this project is that the software be developed using LabVIEW Embedded 8.2. The client, National Instruments, is supporting this project and wishes to exhibit the functionality of the software and target VIs in a robotics application. Therefore, no other considerations were made as to the software selection.

6.4.4 Ranging Modules

A ranging module is needed to see how far away various objects are in the immediate surroundings. They will be used to create a map of the surrounding environment and are critical for obstacle avoidance. The functionality requirements for the ranging modules include:

A maximum range of at least 6 feet Price within the project budget Ability to interface with the controller Small enough in size to mount on the wheelchair Low power requirements are preferred since the power available is limited


Ultrasonic sonar sensorsUltrasonic sensors are a type of ranging module that sends a sound pulse out and measures the time it takes for the pulse to return, like sonar devices. Ultrasonic sensors are cheap but are less accurate than laser sensors and slow because the pulse sent out moves at the speed of sound. The ultrasonic sensors considered for this project are summarized in Table 6.9 through Table 6.11.

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Table 6.9 – SRF04 Sonar Sensor [6]SRF04 Sonar Sensor

Pros Low cost compared to other models Widely available Signal scatters diffusely off of most

objects Unit available for testing from ISU

Robotics ClubCons Wide beam width angle of 55˚ (can only

detect doorways within ~4.8 ft.)

Cost $ 27.72

Ultimately, this ranging module has been selected for use in the project because it is the cheapest module that meets the needs of the project.

Table 6.10 – SRF235 Sonar Sensor [7]SRF235 Sonar Sensor

Pros 15˚ beam-width (high resolution) 100 measurements per second Detects hard, round objects well

Cons Expensive Short maximum range (120 cm or 3.94

ft) Singe transducer (minimum range 10

cm) Must be less than 9˚ angle to surface of

object or beam will reflect awayCost $141

This ranging module would be nice to use in the project but its cost is simply too high to be seriously considered.

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Table 6.11 – SensComp 6500 Sonar Sensor [8]SensComp 6500 Sonar Sensor

Pros Widely available Easy to use a variety of transducers Possible to read multiple echoes Angle of 30˚ to 34˚

Cons Transducer sold separately from module

Expensive compared to other types High Power Requirements Min Range too far (6 in)

Cost $49

This ranging module was not selected for use in the project because its power requirements were higher than necessary and power conservation is an important consideration since there are only two batteries to power the entire system.

Infrared sensorsInfrared (IR) proximity sensors work by sending out a beam of IR light, and then computing the distance to any nearby objects from characteristics of the returned, or reflected, signal. The infrared sensors considered for this project are summarized in Table 6.12 and Table 6.13.

Table 6.12 – Sharp GP2D05 IR Ranger [9]Sharp GP2D05 IR Ranger

Pros Cheaper than sonar sensors Low current consumption (25mA) Fires on clock cycle to save power

(0.3µA off current)

Cons Only tells if obstacle is detected — does not give distance to obstacle

Cost $19

This ranging module is not useful for the project because it does not indicate how far away a detected obstacle is from the sensor, and distance information is critical to the project.

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Table 6.13 – Sharp GP2Y0A02YK IR Sensor [10]Sharp GP2Y0A02YK IR Sensor

Pros Low cost 38ms between readings Max range 60”

Cons Outputs analog signal (0-3V) to give distance to obstacle (A/D needed)

Continuous reading — always on (33mA) Erroneous readings for obstacles closer

than min. range (8”)

Cost $12.50

Although this ranging module has a very low cost, an analog-to-digital converter would be needed for each sensor used, which will greatly complicate the design. Using this sensor would also result in a blind spot of 8 inches around the wheelchair.

Laser sensorsLaser sensors work similarly to IR sensors by sending out a laser signal, and then computing the distance to any nearby objects from characteristics of the returned, or reflected, signal. Laser sensors will have a higher resolution and are faster than ultrasonic sensors, but the price is not within the budget for the project. The laser sensor considered for this project is summarized in Table 6.14.

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Table 6.14 – R283-HOKUYO Laser Sensor [11]R283-HOKUYO Laser Sensor

Pros High resolution (0.36 degrees) 10 readings per second Max range 4 meters Low power consumption (500mA and

5V)Cons Very expensive

Requires serial or USB connection

Cost $2695

A laser sensor would provide much more detailed information than a sonar sensor because of the high resolution, but the cost of the sensor is not within the budget of the project.


Based on the criterion described in the previous section, Table 6.15 summarizes the ranging module evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.15 – Ranging Module Technology Comparison

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TotalSRF04 Ultrasonic Sensor 3 3 4 3 3 16SRF235 Ultrasonic Sensor 4 4 2 3 2 15SensComp 6500 Ultrasonic Sensor 2 3 4 2 1 12GP2D05 IR Sensor 1 2 5 1 3 12GP2Y0A02YK IR Sensor 2 3 5 1 4 15

R283 Laser Sensor 4 4 1 5 5 19

The laser sensor would clearly be the best choice if the project had a larger budget. However, for the purposes of the project, a laser sensor is not necessary to complete the project, and given how much more expensive it is compared to the other alternatives, it is not a good choice. The next highest ranked sensor is the ultrasonic SRF04 sensor, which is thte best overall sensor. It meets the needs of the project better than any other sensor and is very affordable, so it takes preference over all other ranging sensors.

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6.4.5 Orientation Sensors

The functionality requirements for the orientation sensors include the ability to: Indicate the direction with an accuracy of about 5˚ Be mountable on the wheelchair Be powered by the battery Be able to interface with the controller


Magnetic compassA magnetic compass can determine which direction is north based on the earth’s magnetic field. Unfortunately, any source of magnetic flux near the compass can result in false readings by the compass. Table 6.16 summarizes the magnetic compass considered for this project.

Table 6.16 – Devantech R117 Magnetic Compass [12]Devantech R117 Magnetic Compass

Pros Only needs to be calibrated once (stored in EEPROM)

Low power consumption Affordable

Cons Must be mounted parallel to ground for accurate readings

Affected by flux in surrounding environment Proximity to metal can affect accuracy of

readingsCost $52

This compass was chosen for use in the project because it meets the project requirements while still having a low cost.

GyroscopeA gyroscope is needed to know the rate at which the wheelchair is turning so that the location of the wheelchair can be determined while making a turn. Unfortunately the wheels of the wheelchair do occasionally slip, which will result in a slight amount of inaccuracy in determining the present location. Table 6.17 summarizes the gyroscope considered for this project.

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Table 6.17 – ADXRS150 Angular Rate Sensor [13] ADXRS150 Angular Rate Sensor

Pros Affordable Measures up to 150˚/sec

Cons Can be easily damaged if dropped (2000 g)

Cost $64.95 [14]

This gyroscope will be used for the project because it meets the needs of the project and is fairly inexpensive.


Based on the criterion described in the previous section, Table 6.18 summarizes the orientation sensor evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.18 – Orientation Technology Comparison

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TotalR117 Magnetic Compass 4 4 5 3 3 19

ADXRS150 Angular Rate Sensor 3 3 4 3 3 16

The R117 magnetic compass has been selected for use in the project because it performs the necessary requirements and is at the same time very affordable. The only concerns with using it are that when mounted it must be parallel to the ground to provide accurate measurements. This would olny be an issue when traveling up or down ramps, which would be a necessary consideration in a commercial product but is beyond the scope of the project. When it is mounted on the wheelchair, it will be necessary to ensure that it is mounted far enough away from the wheel motors to not have problems with magnetic interference.

The ADXRS150 angular rate sensor is also affordable and will meet the need to keep track of how fast the wheelchair is turning. It is limited to measuring 150˚ per second, but that is nowhere near the turning rate of the wheelchair and thus will not be a problem.

6.4.6 Distance Tracking Sensors

The functionality requirements for the distance tracking sensors include the ability to: Be mounted on the wheelchair Work with the rear wheels of the chair

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High accuracy is not important because of wheel slip Needs a resolution of at least 15˚


OdometerAn odometer calculates the distance that the wheelchair has traveled by measuring the rotation of the wheels. Like the gyroscope, the readings will not be completely reliable due to the slipping that occurs in the wheels when coming to a stop. Therefore it will not be possible to make highly precise measurements. Table 6.19 summarizes the odometer considered for this project.

Table 6.19 – MA2 Miniature Absolute Magnetic Shaft Encoder [15]MA2 Miniature Absolute Magnetic Shaft Encoder

Pros Affordable Accurate to 0.5˚

Cons Inaccuracy from wheel slip

Cost $29

Using an odometer is not necessary for the project, and because of the wheel slip issue, an odometer will not be very useful in the case that it is implemented. Therefore an odometer will not be used for the project.


Based on the criterion described in the previous section, Table 6.20 summarizes the distance tracking evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.20 – Distance Tracking Technology Comparison

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TotalMA2 Miniature Absolute Magnetic Shaft Encoder 4 3 3 3 4 17

The MA2 shaft encoder meets the needs of the project and is one of the least expensive odometers available. However, since having an odometer is not necessary in the implementation of the project and since there will be inaccuracy in the measurements due to wheel slippage, no odometer will be used for the project.

6.4.7 Localization

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A localization technology is needed to indicate where the wheelchair is positioned relative to known points in the environment. The localization will be incorporated into the map of the environment and offer a means of zeroing out cumulative errors at moderately regular intervals, depending on the placement. The functional requirements of a localization system for this project include:

Local detection within a building Does not interfere with normal activities previously in the building Accurate within inches Simple to repair Inexpensive


Off-board trackThe off-board track considered for this project would use a painted line. Using either visible or fluorescent dye, a fixed-width line would be painted on the floor of the operating environment. Two sensors designed to detect either the dye or absence of the dye, would be used to travel along the track. Indicators, such as RFID tags or magnetic plates, would be fixed to the ground at junctions and before sharp bends to signal a need for appropriate speed reduction.

This option would require several pieces of equipment, fluorescent paint, light source, RFID tags or magnetic plates, and a fluorescent light detector. The most important piece of equipment, the light detector, is shown in Table 6.21.

Table 6.21 – Off-board Track LocalizationCZ-H52 UV Sensor, Fluorescence Detection

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Pros Simple. This idea has been used elsewhere with success. Localization and navigation is greatly simplified.

No need for obstacle avoidance. With a track, it would simply be marked and designated as an area that needs to remain obstacle-free.

Cons Not innovative. Basically a glorified train, this option leaves little up to creative development.

Obstacles. Since obstacle avoidance will be disregarded, in the event of a blockage in the path, the wheelchair will have to cease traversing until the obstacle is cleared.

Cost Unavailable

Dead reckoningThis option will implement an odometer. At a designated beginning location, the primary user will input the desired final location into the on-board computer via a keypad. With the computer’s on-board map it will command the wheelchair to travel a certain distance and at certain points turn a specific number of degrees. The odometer and computer together will record the remaining distance until the destination is reached. The Dead Reckoning method does not allow a means of zeroing out cumulative errors.

Table 6.22 discusses the pros and cons to this type of technology. It also contains a picture and price of the main element in this technique, an odometer.

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Table 6.22 – Dead Reckoning LocalizationMA2 Miniature Absolute Magnetic Shaft Encoder

Pros Low Cost. Very few parts are necessary.

Simple. The computer algorithms are simple. No off-board preparation is necessary.

Cons Accumulated errors. Even traveling a short distance can accumulate direction and distance errors. Slippage may be an issue. Also, as little as 1-2 degrees in directional error could be problematic.

Initial position. This method of localization and navigation requires the wheelchair to be initially positioned in a specific location.

Cost $29

Tactile detectionThis option implies physical contact with obstacles. When the wheelchair met a wall or obstacle it would bump into it to determine it impassable. It would then turn and try again. This option does not have any specific destination in mind but records all places it’s been and then uploads a map of possible routes. Table 6.23 summarizes considerations for this option of localization.

Table 6.23 – Tactile Detection LocalizationPros Simple operation

Low Cost Technique already in use with other

mapping robots such as vacuums

Cons Dangerous when the device carries a person.

Impractical for traversing a path. Not easy to implement. In a constantly

changing environment, this device is not accurate enough.

Fixed beaconsThese beacons are fixed at appropriate locations in the environment. The precise locations of these beacons are known to the wheelchair’s onboard computer. As it moves, it uses the on-board device to measure its exact distance and direction from any one beacon. Hence the wheelchair can calculate its own precise position in the environment.

Radio Frequency Technology – The RFID technology uses readers and transponders in close range. The reader would be mounted to the wheelchair and its antenna can read small transponders it passes (within foot). These transponders, each with a unique ID number, would be neatly attached across the ceiling or floor width wise. As the

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wheel chair’s antenna crosses these transponders it will register the closest one and return the corresponding ID number to the computer. The computer which contains an on-board map with a record of all transponders and their precise location will update the wheelchairs current position and alter course as necessary.

Table 6.24 – RFID LocalizationAPSX RW-310 RFID

Reader/Writer Module and Transponders

Pros Low cost. Transponders have already been donated and the RFID device is reasonably priced.

Simple. The concept is easy to understand. Innovative. Using RFID sensors as localization is

not very common. This will provide the group with a well-rounded project.

Compatible. Easy to apply to environment with little interference on previous activities. It is also easy to physically set up a course.

Accurate within inches

Cons Performance. The tags are not completely reliable. They will only work under specific conditions.

Initial position. The wheelchair will need to be initially positioned so that it will eventually encounter a transponder to being its navigation.

Needs to be in close range of transponders.

Cost $173.92

Optical/ultrasonic imagingThis method involves using ultrasonic sensors mounted on the wheelchair. The sensors send out a pulse that is then reflected off nearby surfaces. The reflection is picked up by the sensors and recorded in the on-board computer. The pulse can “view” objects within a certain range of the chair. By recording the position of walls, doors, obstacles, etc. an image of the surroundings can be developed. A clear path can then be navigated.

Table 6.25 – Sonar Imaging LocalizationSRF04 Sonar Sensor

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Pros Precise within inches. The reflected pulse will give the exact distance of an obstacle from the wheelchair.

Low cost. Several would be needed but they are low price compared to other methods.

Durable. These devices are not fragile. Commercializable. Sensors are widely

available and this technique is already in use.

Cons Incompatible. Sonar sensors are already being used for obstacle avoidance. Using this for mapping would interfere.

Difficult implementation. The algorithms involved in using ultrasonic mapping are difficult and waypoints would still be required.

Cost $ 27.72


Based on the criterion described in the previous section, Table 6.26 summarizes localization technology evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.26 – Localization Technology Comparison

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TotalOff-board Track 3 4 3 2 5 17Dead Reckoning 2 2 5 4 4 17Tactile Detection 1 3 3 1 1 9

Proximity Detection 4 4 4 3 4 19

The design team has chosen to use the fixed beacon technology, RFID technology. This option meets the majority of the selection criteria, the cons are significantly less risky than the other two options, and it has been at the forefront of the team’s localization/navigation plans and research.

6.4.8 Motor Control

The motor control is the part of the system that allows us to give driving commands to the wheel chair. The wheel chair itself has a control unit installed that controls the right and left motor. This control unit is a fairly complex system that serves as a central hub for programming and controlling the wheelchair.

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The functionality requirements for the motor control include the ability to:

Receive data from the microprocessor Interpret this data and convert it to a usable form for the wheelchair motor control box

The motor control is the component that takes the user information and sends it to the primary motor control unit on the wheel chair. This wheelchair motor control box interprets this information and then sends the correct, corresponding signals to each wheel motor. The wheelchair and joystick use an analog signal to produce the correct motor control signals, so a digital-to-analog converter (DAC) is required to convert the digital signal from the microprocessor to a correct analog signal.


The functionality requirements of the microprocessor dictate that the motor control must be able to correctly translate or recreate the signal into the motor control. Due to the age of the wheelchair, the company that produced the components for the wheelchair motor control system had very little documentation. The documentation that was retrieved from the company was found to be ineffective in providing useful information upon the signal specifications, schematics, or technical information. Since proper documentation was missing, two possibilities were conceived in controlling the wheelchair:

5.) Control the wheelchair directly through a direct serial port connection to the wheelchair control box6.) Control the wheelchair through the means of high-jacking the joystick signals.

Through testing procedures and analysis steps, the signal from the joystick to the microcontroller was found to be a complex signal that would be nearly impossible for us to directly reproduce without the aid of any documentation and schematic files. Controlling the wheelchair by means of manipulating the joystick was found to be the only feasible possibility.

The motor control is driven by two specific sets of signals, one signal set controlling the forward and backward, and one signal set controlling the right and left movement. Two possible DAC options are available:

1.) Create a DAC circuit through the use of op-amps2.) Purchase a general-use DAC

Creating the DAC circuit would allow the circuit to be tailored to the specific circuit requirements, and would be readily available to the wheelchair project team. Purchasing a general-use DAC would require modifying it to meet the specifications. Table 6.27and Table 6.28 summarize these options.

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Table 6.27 – ADAC0808 8-Bit D/A Converter [16]ADC0808 8-bit D/A Converter

Pros Simple to integrate “stand alone” converter Fairly inexpensive Precise and preconfigured/tested

Cons Requires time for delivery, so testing will be stalled until it arrives

Cost $1.74

Table 6.28 – Custom D/A ConvertersCustom D/A Converters

Pros Ready to use Easily modified

Cons Components will still need to be ordered

Control box connection – The most desired way to connect the controller and A/D converter is to connect it to the controller directly. There are two pins that control the motor control: pin 4 and pin 6. The signal provided by the joystick through these pins is a varying 200mV Peak-Peak AC signal that provides 5.9V ± 900mV DC offset. Table6.29 summarizes the considerations for a control box connection.

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Table 6.29 – Control Box ConnectionControl Box Connection

Pros Direct route to the controller Ideal connection for commercial

production

Cons Damaging the control box would be costly

Control box is nearly impossible to replace due to its very old design

Joystick connection – Directly tapping into the joystick to manipulate the voltages allows for the ability to let the joystick handle all of the output and the interface with the controller but does not worry about the more complex issues in dealing with the controller. Table 6.30 summarizes the considerations for a joystick connection.

Table 6.30 – Joystick ConnectionJoystick Connection

Pros Simple, DC voltage inputs required The joystick will produce the same AC

signal as the control box was originally designed to handle

Cons Not an ideal design for commercial production

Technical documentation on the joystick is unavailable


Based on the criterion described in the previous section, Table 6.31 summarizes motor control technology evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

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Table 6.31 – Motor Control Technology Comparison

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TotalDC0808 8-bit D/A Converter 4 4 5 4 5 21Custom D/A Converter 4 2 4 2 2 14Joystick Connection 4 1 5 2 2 14

Control Box Connection 3 3 5 3 3 17

After comparing all options and discussing them with the client. The design team has chosen to use the DC0808 8-bit D/A Converter and the Control Box Connection. These options meet the majority of the selection criteria and offer the best combination of compatibility and ease of implementation.

6.4.9 Power Management

The prototype being built will need to operate freely. This means that all devices on-board will need to be powered wirelessly. The following will discuss power considerations for elements in need of an electrical hookup. These elements include the wheelchair motors and control, the microprocessor, ultrasonic sensor system, RFID system, compass, gyroscope, and on-board computer.

Overview of power requirements for each:

Wheelchair motors and control 24V Currently runs off of two dual 12V batteries in seriesMicroprocessor 9VDC, 300mA Currently runs off of a 9V wall adaptorUltrasonic sensor system (x13) 5VDC each, 30-50mA Currently has no power supplyRFID system 6-9VDC, 80mA Currently has a 6-9V wall adaptor or battery poweredCompass 5VDC, 20mA Currently has no power supplyGyroscope 5VDC, 6mA Currently has no power supplyComputer 15V, 4A Currently has a wall adaptor or battery powered


There are several approaches which can be used for power management. The following discussion explores these options:

Individual power supplies – This option would be the easiest to handle but lacks elegance. In a commercial situation the power supplies for all devices would be more integrated. It is unpractical to have more than a couple of batteries since the life of the battery would then differ for all and constant changing would be necessary. This option would be fairly low risk since only simple circuits are used. To make this option more practical it is a good idea to take a few of the elements with similar voltage requirements such as the gyroscope, compass, and ultrasonic sensors and combine them for a more efficient design.

Integrated power supplies – This entails in-depth and potentially difficult circuitry involving transformers, voltage dividers, and voltage regulators. Although a successful design would be the most elegant, circuitry like this is a project in itself. This is also a high risk project most likely resulting in the loss and repurchase of equipment. In a

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commercial situation this option would definitely be used. As for a senior design project required to be done in two semesters this option is not practical.

Extension cord – Although this option is the most inelegant, an extension cord would simplify the power supply issues and give infinite power supply. Along with being inelegant the dragging of the cord could potentially hinder the purpose of the project. If the chair’s transversal is prevented by a defect in power design the project has failed. This option is too high risk and unaesthetic.


It has been decided that the best option to implement and test is individual power supply. The team’s design, however, will be a more integrated version. The two 12V batteries will not be used except to power the wheelchair motors and control. The idea is to combine the devices with similar voltage requirements.

6.4.10 User Interface

If this system is to be design for commercial use, the team would consider more sophisticated products for the user interface which would have the ability to display a map of the environment, provide the current location of the wheelchair on the map, provide user with more starting and destination locations, and possibly offer the functionality of a touchscreen.

Since this project will design a prototype, the functionality requirements for the user interface include the ability to: Select a starting and destination location Display the current selection Update and display the latest position Indicate that the path is obstructed


KeypadA keypad will allow the user to provide the current location of the wheelchair and indicate the desired destination of the wheelchair with simple keystrokes. Table 6.32 and Table 6.34 summarize the keypads considered for this project.

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Table 6.32 – Trident GPA 400 PIN Keypad [17]Trident - GPA 400 PIN Pad

Pros 4x4 keypad with 3 function keys 2x16 character display Backlight 8 General Purpose Output Pins

Cons Cable sold separately More power consumption w/ backlight

Cost $ N/A

Table 6.33 – Targus USB Numeric 19-Key Mini Keypad [18]Targus USB Numeric 19-Key Mini Keypad

Pros 19 keypad Inexpensive USB interface Inexpensive

Cons Less functionality Limited, 90 day warranty

Cost $ 9.99

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Table 6.34 – Kensington Pocket Keypad [19]Kensington Pocket Keypad w/2-Port USB Hub

Pros 17-key pad 2-Port USB Hub More functionality Cable included 5-year warranty

Cons Expensive Fewer keys

Cost $ 24.99

LCDAn LCD will allow the microprocessor to display what inputs are received and display information about the current position or operational indicators. Table 6.35 and Table 6.36 summarize the LCDs considered for this project.

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Table 6.35 – Phidget Text LCD [20]Phidget - PhidgetTextLCD 20x2 Character LCD

Pros Compatible design with the Mini-ITX 2x20 character display 8 Digital Inputs 8 Analog Inputs 8 Digital Outputs USB cable included Backlight

Cons 2-line display Expensive More power consumption w/ backlight

Cost $109.13

Table 6.36 – Mini-Box picoLCD [21]Mini-Box - picoLCD 20x2 Character LCD

Pros Compatible design with the Mini-ITX 2x20 character display Inexpensive Backlight 8 General Purpose Output Pins

Cons 2-line display Cable sold separately More power consumption w/ backlight

Cost $ 39.95

TouchscreenA touchscreen will allow the user to input data with a customizable interface. The touchscreen will operate both as an input device and display. Table 6.35 summarizes the touchscreen considered for this project.

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Table 6.37 – Optrex TM1B5BW Touchscreen [22]Optrex TM1B5BW Touchscreen

Pros Large 2.8" diagonal active area Selectable serial or 8-bit parallel

interface 5V supply voltage

Cons More complex integration with eval board

High price

Cost $137 [23]


Based on the criterion described in the previous section, Table 6.38 summarizes the distance tracking evaluation process as the technology options were rated on a scale of 1 to 5, 5 being the best..

Table 6.38 – User Interface Technology Comparison

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ty

Ease

of

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emen

tatio

n

Cos

t

Dur

abili

ty

Ease

of U

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TotalTrident - GPA 400 PIN Pad 3 4 2 2 4 15Targus USB Numeric 19-Key Mini Keypad 3 4 4 2 4 17Kensington Pocket Keypad 3 2 2 4 4 15PhidgetTextLCD 2x20 Character LCD 4 3 2 2 4 15Mini-box picoLCD 2x20 Character LCD 3 3 4 2 4 16

Optrex TM1B5BW Touchscreen 3 2 2 2 4 13

The products are very similar in terms of selection criteria. For the prototype of this system, the technologies offered by Mini-Box for the LCD (Model picoLCD) and ComputerGeeks for keypad (Model Targus USB) were chosen. The reasons for the LCD selections are the cost and the fact that they are offered by the same company that provided the mini-itx board. The keypad selection was also influenced by the cost factor and simplicity.

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6.5 Testing Requirements

The testing component of this project can be viewed from two distinct objectives. The first objective is unit testing which will verify the functionality of a single component. The second objective is integration testing which will verify the functionality of the single component in conjunction with the extended system to insure the component is functioning as expected within the context of the overall design.

Furthermore, non-team members will be brought in to test the complete system. These persons will be monitored by the team members and any unanticipated operation or error in the system will be documented. The team will then address the issues of concern as soon as possible.

The unit testing has been broken down in the nest section. Each team member is responsible for being a primary ‘black box’ tester of the component integration, while the member most familiar with the component will be responsible for the unit testing. The software will be tested in the same manner, with a ‘black box’ tester for each module, in addition to the programmer’s unit testing.

6.5.1 Microprocessor

The microcontroller at the heart of the complete system will be tested as a unit in the procedure outline in this section. The integration testing will be done with all the peripherals connected after the unit testing has verified that the microprocessor operates as expected.

6.5.1.1 Hardware

The sensor to microcontroller communication, including communication between the ultrasonic sensors, compass, gyroscope, and localization hardware, will be tested by verifying the integrity of command strings sent from the microcontroller to the sensor and vice versa.

The testing procedure will begin with the microcontroller sending a command to the sensor module. The contents of the transmitted signal will be observed on an oscilloscope and compared to the sensor module response which will also be observed on a second channel on the oscilloscope. Additionally, the response received at the microcontroller’s communication port will be stored in digital form and compared to the signal contents. The test will be considered successful if the integrity of the data sent up/downstream is maintained.

6.5.1.2 Software

The software designed with LabVIEW Embedded 8.2 will use the debug functions available in LabVIEW to test the following components of the software: motor control, sensor stimulus, sensor response recognition, path calculation, and obstacle avoidance calculation.

Since all of the software will be built with individual modules, or VIs, for the motor control, sensor stimulus, etc, each VI will be given an input for which the expected output is known. The variables will be monitored using the LabVIEW probes and the output verified. The test will be considered successful if the actual output matches the expected output.

6.5.2 Sensors

Various tests will need to be performed on each of the sensors used for the project to ensure accurate measurements are being made and that the sensors are performing as expected. Tests should be done first on the sensors themselves and second on the entire system once mounted on the wheelchair and interfaced with the microcontroller.

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6.5.2.1 Ranging Module

Testing will need to be done on the sensors themselves to ensure that they operate as intended and that the distance readings are accurate. This can be done by connecting one of the sensors to the microcontroller and running a program that continuously triggers the sensor every 50 ms and returns the distance to the nearest obstacle. This value can then be compared to a known distance to the obstacle at increments of 6”, 12”, 18”, 24” etc. until it is no longer detected. This also should be done at varying angles from the sensor in 5˚ increments. These measurements should match approximately the beam pattern from the specifications.

Testing will also need to be done once the sensors are mounted on the wheelchair to ensure that the echo from one sensor is not picked up by another sensor. This can be accomplished by first setting up one sensor to detect no obstacles and then putting an abject in front of each of the other sensors individually and angling the object in such a way as to bounce the signal back to the first sensor. As long as the first sensor does not detect anything, the test can be considered successful. The test will be considered successful if each sensor does not pick up the echo pulse of any other sensor.

6.5.2.2 Orientation

CompassThe compass will need to first be tested to ensure it is not affected adversely by surrounding magnetic fields or metal objects. Possible magnetic flux created by the motors in the wheels and metal frame of the wheelchair are the biggest concerns. This test can be performed first by seeing if bringing the compass near the wheelchair has any affect on the reading. Then, after mounting the compass on the wheelchair, it can be seen if activating the motors has any affect on the compass. For this test, the wheelchair can be propped up so that it does not move when the motors are activated.

A second set of tests will need to be performed to ensure that the compass is giving accurate measurements. This can be done simply by riding around in the wheelchair while comparing the values given by the compass to the known heading. The test will be considered successful if the measured headings match the known headings to within 5˚.

GyroscopeThe gyroscope can be tested by having someone riding in the wheelchair manually follow a curved track along the floor so that the path of the wheelchair is known. The time it takes to reach the end of the path will be timed, and then the rate at which the wheelchair turned can be calculated and compared to the result given by the gyroscope. The test will be considered successful if the measured position of the wheelchair after a turn does not deviate from the known position by more than 5 feet.

6.5.3 Localization

Testing will need to be done on the localization technology to ensure that the RFID reader operates as advertised. This can be done by installing the necessary RFID software on a computer system and connecting the RFID reader to the computer using a USB to RS232 cable. If the computer recognizes the RFID board once it is connected, the connection will be verified.

In addition to the reader’s connection, its ability to read the RFID tags will be tested. First, the reader and antenna will be positioned away from the wheelchair. The RFID tags will be tested starting at the closest distance to the reader then slowly backed away. If the reader is able to detect and identify the tag at the required minimum distance, normal operation will be verified. However, the same process will be repeated with the reader and antenna positioned on the wheelchair. If the reader is able to detect and identify the tag at the required minimum distance, the operation necessary for this project will be verified.

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6.5.4 Motor Control

As the motor control is the primary purpose for the wheel chair system, it will need to be vigorously tested early to verify that the correct design implementation is affecting the circuit in the desired way. The circuit interface will need to be tested independently as a system by itself, before it is interfaced with the rest of the system. A digital voltage signal will be required to test the voltage level control. By creating the circuit and applying a 5V signal to each of the pins, they should proportionally step up the wheelchair direction. A sample test case scenario is shown below in Table 6.39.

Table 6.39 – Wheelchair Testing FormForward / Backward Test Result Pass or Fail5V to digital input pin D0 forward movement at about 1/16 max speed5V to digital input pin D1 forward movement at about 1/8 max speed5V to digital input pin D2 forward movement at about 1/4 max speed5V to digital input pin D3 forward movement at about 1/2 max speed5V to all forward digital input pins D0-D3

forward movement at max speed

Forward / Backward Test Result Pass or Fail5V to digital input pin D4 backward movement at about 1/16 max speed5V to digital input pin D5 backward movement at about 1/8 max speed5V to digital input pin D6 backward movement at about 1/4 max speed5V to digital input pin D7 backward movement at about 1/2 max speed5V to all backward digital input pins D4-D7

backward movement at max speed

As the speed of the wheelchair may be too fast for the system to handle appropriately and safely, the speed of the wheelchair may need to be toned down to resolve this concern.


The following will cover the testing requirements for the power systems being used. Several systems have different options to consider if the initial testing fails. This section will first discuss testing for the simple power systems of the wheelchair, RFID reader, and computer then move on to the testing of the designed circuits.

WheelchairTesting plan –

Team will test the dual 12V batteries by checking the drop across the two leads for each battery separate from the wheel chair.

Team will test the wheelchair with batteries in place by running the wheelchair along a course and during time duration similar to the final demonstration.

Pass criteria – The wheelchair does not quit operation before trial is completed. The drop across the two leads each read a 12V drop.

ComputerTesting plan –

Team will test the computer’s fully charged battery with the RFID software and a few other applications running. This will be done for the expected duration of the final demonstration.

Pass criteria – The battery lasts for the duration of the demonstration without needing to be recharged.

RFID readerTesting plan –

Team will test the reader’s fully charged battery running for the expected duration of the final demonstration.

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Pass criteria – The battery lasts for the duration of the demonstration without needing to be recharged.

9VDC Power SystemTesting plan –

System will be built with wire that will be used in final prototype. All leads will be connected properly and tested with 9VDC battery.

If first test fails, battery does not have enough power to supply device, two 9V batteries will be tested in series with a proper resistor to drop the voltage accordingly. This may provide more current to work with.

Pass criteria – Devices in 9VDC system operate correctly and for the amount of time necessary to finish a demonstration.

5VDC Power System Testing plan –

System will be built with wire that will be used in final prototype. All leads will be connected properly and tested with four 1.5VDC batteries and resistor/s that are equivalent to 1.83 ohms.

If first test fails, battery does not have enough power to supply device, different battery types will be tested (AAA, C, D, etc.)

Pass criteria – Devices in 5VDC system operate correctly and for the amount of time necessary to finish a demonstration.


This section describes how the team will conduct the testing on the keypad and the LCD as part of the user interface for the system. In order to be able to test the functionality and accuracy of the keypad and the LCD, the team will need to configure the setting of both the keypad and the LCD so they are compatible with the microcontroller.

KeypadThe team will provide different inputs where each number represents different locations for either the starting or destination area. The microcontroller will be pre-programmed to receive and understand the number from the keypad and associate it with a specified location to perform different actions depending on the location.

The testing will be to validate the user input and see if it sent the same number as what the microcontroller received. In addition, the testing will verify that a series of keystrokes provides the input in the correct mode, either the starting or destination mode. The test will be considered successful if the microprocessor receives the expected character as associated with the pressed key.

LCDThe team will provide different messages as the outputs from the microcontroller and see if the LCD received and displayed the message on the screen correctly. Also, the team will be testing other functionality on the LCD such as deleting the message, clearing the screen, and inserting a new line to print the message. The test will be considered successful if the display shows the expected characters.

6.5.7 System Integration

The integration testing is divided into phases. Similar to the concept of unit testing, the integration will be tested in modules concentrated on examining a specific group of components.

Phase I: Wheelchair controlThe first phase of modular testing will test the microcontroller’s ability to predictably control the movement of the wheelchair. Basic movements such as forward, reverse, a 45 degree turn, a 90 degree turn, and varying speeds will be tested and verified.

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Phase II: Wheelchair control with mappingThe second phase will be a continuation of the first where a map will be programmed into the microcontroller with a specific, short path of travel. The path will be constructed of the basic movements tested in the first phase. The compass and gyroscope data will be used to track the movements of the chair and determine the current and expected orientations. The objective will be to verify that the wheelchair follows the intended path and satisfactorily executes the basic movements.

Phase III: Wheelchair control with interactive mappingThe third phase will add a component of interactive mapping to the preprogrammed map. The microcontroller will use the data received from the range modules to add obstacles into the map. This will cause the intended path to be altered and recalculated around obstacles. The objective is to verify that the wheelchair avoids the obstacles while still traveling to the intended destination.

Phase IV: Wheelchair control with interactive mapping and localizationThe fourth phase will add a component of localization to the mapping algorithm. Using waypoints strategically positioned about the environment, the microcontroller will receive data from the RFID reader indicating the nearest waypoint. The path will be extended for a longer duration where errors in tracking movements and orientation could occur. At each waypoint, the errors will be zeroed out and position within the onboard map verified. The objective is to verify that the wheelchair continues to avoid obstacles while still arriving at the intended destination.

Phase V: Wheelchair control with interactive mapping and localization and user interfaceThe fifth and final phase will add a user interface component. The same testing as described in phase four will be performed with the addition of customizable starting and ending points. This phase will also include adding informative messages to an LCD display while in route. The objective is to verify that the system will convert user input into a workable map/path and maintain performance.

6.6 Project Continuation

At this point in the development process, the project shall continue on as it was originally envisioned. This recommendation is made by the team as the design requirements have be specified, a practical approach to a working solution has been developed, and the design team consists of competent members who are committed to accomplishing the project goal.

However, the team suggests that additional phases of the project could further refine the design into a commercializable product. These phases could focus in more detail on a) the indoor localization system to be used for positioning, b) the obstacle avoidance algorithm, and c) a more sophisticated system of Simultaneous Localization and Mapping (SLAM). Additional improvements could also be made to the user interface and visual appeal of the complete system.

6.7 Detailed Design

The follow material will detail the design aspect of the autonomous wheelchair system. A general overview section describing the basic system integration will be followed by additional sections describing the main functional units.

6.7.1 General Overview

The overall design of the wheelchair system is an intricate interfacing of multiple inputs and outputs. Inputs from the environment are interpreted and used to calculate the path and location of the wheelchair. Figure 6.3 summarizes the inputs, processing and outputs of the system.

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Figure 6.3 – System Flow Diagram

The entire wheelchair system is connected via serial, USB, and other standard ports in addition to custom-designed analog and digital interfacing. Figure 6.4 depicts the system connections and power distribution.

Figure 6.4 – Wheelchair System Diagram

Each of the components in the wheelchair system will be mounted directly on the chair, with the exception of RFID tags to be placed through the environment. The diagram in Figure 6.5 identifies the mounting position of each component. These positions have been chosen to accommodate the operation of the components, to allow for easy access, and to avoid interference with the wheelchair control.

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Inputs Processing Outputs

Starting position/final destination

Current location

Distance to obstacles

Magnetic orientation

Gyroscope orientation

Calculate path from start to end

Determine critical obstacles

Recalculate path from current location

Left/right wheel control for intendedspeed/turn

Left/right wheel control

Sensor stimuli

Input information (interfacing)

Location information (debugging)

[0:7]

12Vreg

24V Battery

Joystick

Left/Right5.9V ± 1V

5.9V ± 1VForward/Reverse

[0:7]ADC

ADC

DB15

Motor Control

Box

RS232

Controller

RFIDReader

Gyroscope

Compass

Sonar Array(x13)

Echo[0:12]

9Vreg5Vreg

Trigger[0:12]

LCDDisplay

USB

USB Keypad

ADC

ADC


Figure 6.5 – System Mounting Diagram

6.7.2 Microprocessor

The controller and board are the center of the overall design. All external sensors and controls will connect directly to the controller as indicated in Figure 6.6, and all mapping and calculations will be performed with the controller using LabVIEW Embedded 8.2.

Figure 6.6 – Controller Connection Block Diagram

6.7.2.1 Hardware

The controller used in this project is an EPIA-EN12000EG Mini-ITX from VIA. The main features are summarized in Table 6.40.

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1 Controller2 LCD3 Keypad4 Compass5 Gyroscope6 Modified joystick7 Motor Control Box8 Batteries9 Sonar10 RFID Reader

12

3

4

59

7

8

10

6

Keypad

HC-KP

Compass

R117

Gyroscope

ADXRS150

WheelchairJoystick

RFID Reader

RW-310

9VDC Power Supply

RS 232

USB

LCD Display

HC-LCD

Ultrasonic Sensors

S4F04

DC Jack

Controller

Mini-ITX

USB

ADCDAC PWM


Table 6.40 – EPIA-EN12000EG Mini-ITX Features [Error: Reference source not found]Main Features

Processor 1.2GHz VIA Eden nanoBGA2 FanlessCable/Connection (x2) RS232Power Consumption 12W – 15W (12-13W typical)

MemoryOn Board

DDR2 533 SDRAM 1 DDR2 400/533 DIMM socket (Up to 1 GB)Internal

Flash 1024 KByteRAM 36 KByte

PortsIDE (x2) UltraDMA 133/100/66 40-pin ATA133Serial ATA (x2) SATAUSB (x6) (x4) Back Panel USB v2.0

(x2) Onboard USB 2.0 (via 1 pin header)Firewire (x1) Onboard IEEE 1394Video (x2) (x1) VT1625M HDTV Encoder

(x1) S-Video OutLAN (x1) VT6122 GLAN Controller (Gigabit)PS/2 (x2) PS/2 keyboard/mouseSerial (x2) (x1) Back Panel COM

(x1) Onboard COMPCI (x1) PCI Slot

Dimensions 170mm x 170mm

The output of the controller to each of the onboard sensors – compass, gyroscope, and ultrasonic sensors – and the wheelchair control box will be transmitted through the serial ports. The input received from these sensors will be received through the Analog to Digital Converter (ADC). Communication with the RFID reader will be made through the second RS232 serial port. The evaluation board is equipped to handle a KEYPAD and LCD through either a USB or a video port. Operation of the board requires up to 15W.

6.7.2.2 Software

The basic program flow of the software to be developed in LabVIEW for operation on the controller is summarized on the left side of Figure 6.7. The flow has been further modulated on the right side of this figure to indicate six main states of operation. These main states are idle, setup navigation, calibrate sensors, scan environment, obstacle avoidance, and navigation.

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Figure 6.7 – General Program Flow

Idle stateThe idle state is the first state entered upon program execution. In this state the controller polls the keypad waiting for user input. No wheelchair movement is performed in this state.

checkKeypad – this function/VI polls the keypad port in a continuous loop and exit when a response is received indicating that a key has been pressed.

Setup navigationThe setup state is entered as soon as a key has been pressed on the keypad. The LCD display then presents the user will simple instructions for entering the starting and destination points. Once these inputs are received the controller

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calculates a path from the starting to destination point within the preprogrammed map. No wheelchair movement is performed in this state.

getInputs – this function/VI prompts the user for the starting point, wait for confirmation, prompt the user for the destination point, wait for confirmation, then output the coordinates of the two points.

calPath – this function/VI receives the starting and ending point and calculates a path from the starting point to the destination from within a preprogrammed map. The path consists of blocks containing distances and maneuvers to be executed in order to reach the destination.

Calibrate sensorsThe calibration state is entered as soon as the path has been calculated. The controller then sends stimulus signals to the ranging modules and orientation sensors for calibration. No wheelchair movement is performed in this state.

calSensors – this function/VI sends a stimulus signal to the ranging modules preparing them for operation.calOrient – this function/V sends a stimulus signal to the compass and gyroscope preparing them for operation.

It also stores the current values in memory for reference.

Scan environmentThe scan environment state is entered either directly after calibration of sensors or after a movement has been performed. In this state, the controller sends stimulus signals all of the sensors and RFID reader then stores the returned data. The data is recalled and used to determine if an obstacle is within critical distance and to determine the orientation of the wheelchair and position within the map. The wheelchair may be in motion during this state.

scanEnviro – this function/VI sends a stimulus signal to all of the sensors and RFID reader then stores the returned data.

checkPos – this function/VI recalls the gyroscope, compass, and RFID data to determine the orientation of the wheelchair and the location relative to waypoints programmed into the map. This information is then stored.

checkObs – this function/VI recalls the ranging module data to determine if an obstacle is detected within a critical distance relative to current operation.

recalcPath – this function/VI recalls the position and obstacle data. If the position is not within tolerance of the expected position, the remainder of the path is recalculated with the current position as the new starting point. If an obstacle is detected as an upcoming, but not immediate threat, the path is recalculated around the expected perimeter of the obstacle.

Obstacle avoidanceThe obstacle avoidance state is entered if an obstacle is detected within a critical distance relative to the current operation. In this state, the controller issues a command to halt navigation, recalls the ranging module data, determines an unobstructed direction, and issues a command to turn right or left in the clear direction.

stopChair – this function/VI sends a stimulus signal to the wheelchair control box that discontinues movement.avoidObs – this function/VI recalls the ranging module data and determines whether or not an unobstructed

direction exists. In the instance where a clear direction can be determined, a stimulus signal is sent to the wheelchair control box to rotate in that direction. However, if it cannot be determined that there is a clear alternate route, a warning is issued to the user.

General navigationThe general navigation state is entered when the current path is free of obstacles. In this state, the controller issues navigational commands to the wheelchair control box based on the position determined in the scan environment state.

moveFwdRvs – this function/VI sends a stimulus signal to the wheelchair control box that rotates both chair wheels, simultaneously, at the same speed.

rotLeftRight – this function/VI recalls the ranging module data and determines whether or not the intended direction of travel is unobstructed. In the instance where the direction is clear, a stimulus signal is sent to the wheelchair control box to rotate the appropriate amount in that direction. However, if it cannot be determined that the intended direction is clear, a warning is issued to the user, and the obstruction will be treated as an obstacle.

adjSpeed – this function/VI recalls the position and obstacle data and sends a stimulus signal to the wheelchair control box either increasing speed, if the path is clear, or decreasing speed, if the path is beginning to detect obstacles or will change direction shortly.

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6.7.3 Sensors

The following sensors will be used in the design for the project. Included are the technical sepcifications for each sensor, how they are interfaced with the controller, and how they are used.

6.7.3.1 Ranging Module

The technical specifications for the SRF04 ultrasonic sonar sensor are shown below. Also shown are the pin connections and how they are used.

Ranging Module: SRF04 Ultrasonic Sonar Sensor

Table 6.41 – SRF04 Technical Specifications [24]Beam Width ~55˚Power

Voltage 5 VoltsCurrent 30 mA Typical, 50 mA max

Frequency 40 kHzClock 625 kHz (1.6 µs)Range

Maximum 3 mMinimum 3 cm

Sensitivity Detect 3 cm diameter stick at > 2 mWeight 0.4 ozSize 1.75” w x 0.625” h x 0.5” d

Table 6.42 – SRF04 Pin Connections [25]5V Supply Needs 5 volts DC to power the

device

Echo Pulse Output This pin creates a pulse proportional in width to the distance of the nearest object detected.

Trigger Pulse Input A 10µs pulse is used in this pin to trigger the device and send the echo pulse.

Do Not Connect This pin is not used.

0V Ground This is the pin for the connection to ground.

The timing diagram in Figure 6.8 shows that to trigger the sensor, a 10µs pulse must be sent on the trigger input pin. There must be at least 10ms between the end of the echo pulse and the beginning of a new trigger pulse. The sonic burst sent out by the sensor is a set of 8 bursts at 40 kHz. Once the return of the sound wave is detected, an echo pulse will be sent on the echo output pin that is proportional in width to the distance of the nearest detected object. The width of that pulse ranges from 100µs to 18ms, or is 36ms if the pulse does not return (nothing detected). The maximum range of the sensor is 118 inches (9m), or 236 inches round trip. With sound traveling 1 inch every 73.746µs, it will take at most 17.4 ms for the pulse to return. Therefore, the maximum time between triggers of the device is about 64ms (18ms + 36ms + 10ms).

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Figure 6.8 – SRF04 Timing Diagram [Error: Reference source not found]

The beam pattern pictured in Figure 6.9 gives the effective detection range for the sensor. The angular beam width is about 55˚, which will detect a 30” doorway at a distance of about 2.4 feet or less. (Calculation: 15 / tan(27.5˚))

Figure 6.9 – SRF04 Beam Pattern [Error: Reference source not found]

MountingAn arrangement of 13 sonar sensors will be used as pictured in Figure 6.10. The two sensors mounted on each side of the wheelchair facing the walls can be used to measure the distance to the walls. This will make it easier to travel in a direction parallel to them. The sensors on each side mounted at a 60˚ angle will help for the detection of doorways. In order to detect a 30” doorway, the wheelchair will need to be less than 19.6” away from the wall (Calculation: 30tan(2.5˚)/[(tan57.5˚-tan2.5˚)*tan2.5˚]). The remaining sensors mounted on the front will be used primarily for obstacle detection and avoidance. A mounting diagram is shown in Figure 6.10.

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Figure 6.10 – Ranging Module Mounting Arrangement

The image in Figure 6.11 shows what the sensors, mounted as described, might see in a typical hallway. Red is an area free from obstacles as detected by the sensors, dark blue shows blind-spots, and light blue is halls and rooms. The wheelchair is depicted by the grey square. The picture shows that the resolution of the sensors will be fairly low and that it will not be easy to distinguish walls from obstacles.

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Figure 6.11 – Ranging Module Mapping in a Hallway

6.7.3.2 Orientation

Shown below are the technical specifications for the R117 magnetic compass. Also shown are the pin connections and their uses.

Compass: Devantech R117 Magnetic Compass

Table 6.43 – R117 Compass Technical Specifications [Error: Reference source not found]Power

Voltage 5 VoltsCurrent 20 mA

Resolution 0.1˚Accuracy ~3-4˚ after calibrationOutputs

Primary Timing Pulse 1-37 ms (0.1 ms increments)Secondary I2C Interface, 0-255 and 0-3599

SCL Speed Up to 1 MHzWeight 0.03 ozSize 32 mm x 35 mm

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Table 6.44 – R117 Compass Pin Connections [26]1 Needs supply voltage of 5 volts

to power the device.2 Used for I2C interface

3 Used for I2C interface.

4 Pulse width modulator.

5 No connect.

6 Used for initial calibration. The pin has a pull-up resistor and can therefore be left unconnected after the calibration. The calibration only needs to be done once because the data is stored to EEPROM. By default, the calibration is set for use at 67˚ latitude.

7 Used to select 50Hz (low) or 60Hz (high) operation.

8 No connect.9 Connection to ground.

The heading of the compass can be given as a pulse width modulated signal that varies from 1ms to 36.99 ms, where each 100µs represents 1˚. The time between pulses is 65ms, where the signal will have a negative voltage. In order to use the PMW mode of operation, the I2C pins (2 & 3) must be connected to the 5V power supply using 47 kΩ resistors.

The timing diagram in Figure 6.12 shows how the alternative I2C interface can be used to obtain compass measurements. However, this method will not be used for the project since the PMW method will be better suited to the needs of the project.

Figure 6.12 – R117 Compass Timing Diagram [Error: Reference source not found]

MountingThe device must be mounted parallel to the ground to function properly and cannot be used near magnetic fields, such as the ones created by some motors. Proximity to metal can also interfere with the accuracy of the device. The best place to mount it will be behind the chair, out of sight and near the controller and batteries.

Gyroscope: ADXRS150 Angular Rate Sensor ADXRS150

Shown below are the technical specifications for the ADXRS150 angular rate sensor.

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Table 6.45 – ADXRS150 Gyroscope Technical Specifications [27]Power

Voltage 4.75 to 5.25 VCurrent 6 mA

Range +/- 150˚/sSensitivity 12.5 mV/˚/sTypical Bandwidth 0.04 kHzNoise Density 0.05 ˚/s/rtHzNonlinearity 0.1% of FSTemp Sensor YesVoltage Reference YesTemp Range -40 to 85˚ CPackage 32-BGA

MountingThe gyroscope can also be mounted on the back of the wheelchair, just above the compass. This will keep it out of sight and safe from damage if the wheelchair collides with anything.

6.7.4 Localization

Following is the detailed plan for localization design. How the technology will operate and the research will be covered. Next, this section will describe the specifications of the chosen device as well as connections and other devices needed for this technology to be implemented.

OperationTo traverse from one point to another using this technology, the wheelchair will need to initially be placed by the primary user in a location facing towards the final destination along a clean route to the first row of RFID tags as shown in Figure 6.13. The wheelchair will begin its motion in a straight forward path. As it passes over the row of transponders the onboard computer will recognize the relayed ID number of the closest one and update it’s location into the computer’s on-board map. The wheelchair will then adjust its direction accordingly. When the antenna passes over any of the transponders in the last row before the intended destination the chair will be programmed to stop.

Figure 6.13 – RFID Tag Placement

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Path of traversal

Row of identical RFID tags

Row of unique RFID tags

Wheelchair

Doorway


Each path will be programmed into the computer. For example, if the chair starts at point B and is commanded to travel to point D the computer will have a preprogrammed sequence of transponder rows to follow. From point A to point B, the computer has a different sequence.

ResearchThe team researched the use of two different types of RFID readers, low frequency which reads solid plastic and glass transponders at 134.2 kHz and high frequency which reads solid transponders as well as convenient, thin, tags at 13.56 MHz. The team was initially provided with a low frequency reader kit as well as high frequency tags. Although the team had the option of using the provided reader, the team would prefer to use a high-frequency reader with an antenna that has a larger reading area. The RFID sensor device the team has considered implementing is an APSX RW-310 Reader/Writer Module found via the internet. Following are the specifications of this device.

Images of the transponders provided in the kit are shown in Figure 6.14 . On the left is an image of the reader itself equipped with a serial port. The device below the RF reader is shown a C-100 converter that can be purchased as well. This device boosts the signal levels to the RS232 so that it can communicate with the computer. If this device passes the initial tests the team will choose to purchase the C-100.

Figure 6.14 – APSX RW-310 RFID Reader/Writer Module and Transponders

Table 6.46 describes the main features and specifications of the selected RFID reader/writer module.

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Table 6.46 – RW-310 RFID Reader/Write Module FeaturesRead/Write Frequency 13.56MHzData Rate 19200 bpsRange

Credit card size tags 11”CD/DVD size labels 5”24mm circular labels 4”Mini tags 6”

Read Area 9" x 8"Other Features On-board antenna

Built-in TTL. Need to use level converter to connect directly to PC (max232) or use APSX C-100 converter board.

DC or Battery power for mobile operations. Power consumption 20mA at stand by, 80mA in fast mode (20 reads per sec.)

Powerful firmware enables read and write any type of 13.56 MHz RFID tag (ISO15693)

Shorter transaction time than 125 kHz systems

Two programmable LEDs are available for visual feedback

Power standard 6VDC wall adaptor or 6-9 VDCDimensions 9" x 6” x 0.25”

This RF device the team will use operates at 13.56 MHz and will pick up reflected signals from 1in2 flat, sticky back, read/write transponders. The reader and antenna will be attached to the wheelchair to the base near the ground. The transponders will be laid in a straight line the width of the hallway or room. These transponders have been provided by senior design, will not need to be purchased, and will not hinder the project budget. They are 13.56/914 MHz tags.

PowerThis device is equipped with DC or battery power option. It needs 6-9V at 80mA to run. The team will rely on the battery power option for this device and mention, but not discuss, the power requirements for this device in the on-board power section of this design report.

ConnectionsThe RFID reader has a male serial cable port to communicate with the computer. Included with the reader is software to be loaded onto a computer that will then send read or write commands to the reader. The design team would have preferred to connect the RFID reader directly to the microprocessor but are still waiting for a reply from the manufacturer. Currently, it is unknown whether the software will be able to be loaded onto the provided microprocessor. Due to the difficulty with integrating the RFID reader and controller the reader will be directly connected into the computer through a serial port as shown in Figure 6.15 . This will meet out needs and is the current plan. Specific software considerations will need to be reviewed concerning this after the device is purchased.

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Figure 6.15 – Computer to RFID Reader

6.7.5 Motor Control

The motor control design is created to mimic or simulate the signals created in the joystick. This circuit is based of a 5.9V signal that is used within the joystick to provide the necessary mapped output to the wheelchair motor control box. The joystick itself is a two-dimensional potentiometer that manipulates the voltage level of the forward and backward, as well as right and left movements when the user moves the joystick in one direction or another. A signal level of 5.9V on both the forward and back, and right and left signals is interpreted by the joystick control as centered, and thus not moving. The voltage level of both signals is than raised or lowered by a value up to +/- 900 mV. The joystick circuit then translates the 5.9V +/- 900 mV analog signal to a complex signal which is sent to the wheelchair motor control box. The important operation of the joystick is shown in Figure 6.16.

Figure 6.16 – Invacare Arrow Joystick Schematic

As the voltage level rises for the forward and backward direction from 5.9V, the wheel chair moves forward, virtually similarly proportional to the rise in voltage. When the voltage reaches 6.8V (5.9V + 900mV), the wheelchair will be moving forward at top speed. As the voltage level decreases from 5.9V, the wheel chair starts moving backward until the voltage level reaches 5.0V, which is fully backward. A connection diagram which will output these desired signals is shown in Figure 6.17.

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Figure 6.17 – Controller to Joystick Connection Diagram

There are two sets of op-amps that convert the digital signal into an analog signal. The top-left four op-amps are used to create the forward move signal. The bottom-left four op-amps then convert the backward move signal. These two signals are then summed together, and converted to a +/- 900 mV signal, which is then summed with the 5.9V stationary signal. This output will be fed into pin 4 of the DB15 connector to the motor control box. Table 6.47 summarizes the digital output mapping necessary for forward and reverse motor control.

Table 6.47 – Digital Output Mapping to Motor Control (Forward/Reverse)Digital Output From

Controller Wheelchair Movement Direction D/A Output Voltage

00000000 Stationary 5.9V

00001111 Full Forward 6.8V

11110000 Full Reverse 5.0V

The signal for the right and left control is the same signal and circuit that is used as the forward and backward control; with the right turn signal being the same as the forward movement signal, and the left turn signal being the same as the backward movement signal. This output will be fed into pin 6 of the DB15 connector to the motor control box. Table 6.48 summarizes the digital output mapping necessary for left and right motor control.

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Table 6.48 – Digital Output Mapping to Motor Control (Left/Right)Digital Output From

Controller Wheelchair Movement Direction D/A Output Voltage

00000000 Stationary 5.9V

00001111 Full Right 6.8V

11110000 Full Left 5.0V


Following is a description of the power design that will be implemented. This will include configurations as well as specifications for the circuitry required.

The systems will be combined as follows:

5VDC Battery 9VDC Battery Portable Power Already Supplied Compass Controller WheelchairGyroscope ComputerUltrasonic Sensors RFID Reader*

*The RFID reader could also be supplied by the 9VDC battery system and therefore be combined with the Controller.

This grouping would require 5 or 4* separate power sources. Figure 6.18 and Figure 6.19 are diagrams of the circuits for the 5VDC and 9VDC systems. The 9VDC circuit includes the reader.

Figure 6.18 – 5VDC System

Figure 6.19 – 9VDC System

The 9VDC system in Figure 6.18 should work well with a regular 9VDC battery. The specifications in Table 6.49 are of the battery that should serve the purpose.

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Table 6.49 – 9V Energizer Battery SpecificationsClassification AlkalineChemical System Zinc-Manganese Dioxide (Zn/MnO 2)Designation ANSI-1604A, IEC-6LR61Nominal Voltage 9.0 voltsOperating Temp -18°C to 55°C (0°F to 130°F)Typical Weight 45.6 grams (1.6 oz.)Typical Volume 21.1 cubic centimeters (1.3 cubic inch)Jacket MetalShelf Life 5 years at 21°C (80% of initial capacity)Terminal Miniature SnapCapacity 625 mAh

With this capacity, 625 mAh, this circuit should be able to run the 9VDC circuit (as shown with RFID reader attached) for at least an hour and a half non-stop. This will satisfy the time requirement

The 5VDC system in Figure 6.19 will need to be constructed differently. It is unnecessary to find a 5VDC battery. Instead, four 1.5VDC batteries can be used and a resistor in line with the battery will drop the voltage so about 5V will be delivered to the devices.

A major factor to take into consideration with this set up is that when the ultrasonic sensors are not sending a pulse the current they draw would be 20mA. Therefore the current range this circuit will run at is 416 mA (when all 13 sensors are 20mA) to 676 mA (when all 13 sensors are 50mA). Accordingly, the voltage drop across the resistor will increase or decrease. Since all devices can operate between 4.5V to 5.5V (optimum at 5V) this should not cause a problem as long as a proper resistor value is found. Figure 6.20 shows how this circuit would be constructed.

Figure 6.20 – 6VDC to 5VDC

After figuring a median current draw of 546 mA the resistance with the extreme values furthest from the voltage limit was found. A resistance of 1.83 mA gives a voltage range of 4.76V – 5.24V to the devices. This will not put any of the devices at great risk.

There are several 1.5V batteries that can be used for this circuit. Regular AA, AAA, C, and D can all be used. For the team’s purpose four AA batteries will work. The specifications in Table 6.50 are for an Energizer AA battery.

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Table 6.50 – AA Energizer Battery SpecificationsClassification AlkalineChemical System Zinc-Manganese Dioxide (Zn/MnO 2)Designation ANSI-15A, IEC-LR6Nominal Voltage 1.5 voltsNominal IR 150 to 300 milliohms (fresh)*Operating Temp -18°C to 55°C (0°F to 130°F)Typical Weight 23.0 grams (0.8 oz.)Typical Volume 8.1 cubic centimeters (0.5 cubic inch)Jacket Plastic LabelShelf Life 7 years at 21°C (80% of initial capacity)Terminal Flat ContactCapacity 2850 mAh

The capacity rating for this battery will allow the system to run long enough to serve its purpose. This system should last at least 4 hours of non-stop operation.

All-in-all the time-limit for portable, non-stop operation will be approximately 1 ½ hrs. This will be plenty of time for demonstration and testing of the team’s prototype. After that amount of time (limited by the 9V battery) this element can be cheaply replaced.


This section provides more in-depth detail about the keypad and the LCD. It includes information regarding the schematics, basic operations, the connection, and the pin assignment. Neither the keypad nor the LCD will need an individual power supply as power will be supplied via the connector.

KeypadThe keypad will be connected directly to the controller through a USB port. The controller will continuously poll the keypad during idle operation and while obtaining the starting/ending positions.

LCDThe LCD will be connected directly to the controller through a USB port, similar to the keypad. Control Codes are used for LCD panel setup and control of character or cursor position. All control codes are contained in a software library provided with the LCD hardware (PHIDGET.msi). The characters displayed on the LCD will resemble the characters shown in Figure 6.21.

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Figure 6.21 – LCD Character Displays [28]

MountingThe LCD and keypad will be mounted behind the seat of the wheelchair at approximately waist height. Mounted at this position allows the user interface to be at easy access for a standing user, such a member of the hospital staff, and also keeps the components from interfering with the wheelchair operation.

6.7.8 Design Summary

The design described attempts to address the main functionality requirements as shown in Table 6.51. Each functionality is ranked according to its relative importance to the overall design. The design presented in this document is then given an evaluation score which measures how well the design meets the functionality requirement. The resultant score for this design is 91.75%.

Table 6.51 – Evaluation of Design Functionality

Functionality Relative Importance

Evaluation Score

Resultant Score

LabVIEW Embedded controlled operation 35% 100% 35%User-selectable starting and ending points 5% 95% 4.75%Path calculation 10% 90% 9%Obstacle detection 10% 90% 9%Obstacle avoidance 5% 80% 4%Location recognition 10% 50% 5%Speed control (forward, reverse, stop) 15% 100% 15%Turn control with 5% accuracy 10% 100% 10%

Total 100% 91.75%

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Estimated Resources

7 Estimated Resource Requirement

The following material specifies the estimated hourly, financial, and other resource requirements for the project.

7.1 Personnel Requirements

The information in Table 7.52 reiterates the initial estimates of hours per task for each team member as stated in the Project Plan.

Table 7.52 – Estimated Person Hours (Original)

Name Task

1D

efin

ition

Task

2Te

chno

logy

Task

3D

esig

n

Task

4P

roto

type

Task

5Te

stin

g

Task

6D

emon

stra

tion

Task

7D

ocum

enta

tion

TotalTara Spoden 15 45 45 25 55 10 45 240Brian Yauk 15 60 55 30 35 10 30 235Margaret Shangle 10 45 35 55 25 10 40 220Vee Shinatrakool 10 30 45 20 35 10 55 205John Volkens 15 40 55 55 30 10 45 250

Group Total 65 220 235 185 180 50 215 1150

Upon closer inspection, it was deemed necessary to further break down these sections into subtasks for a more accurate representation. Table 7.53 shows a revised representation of personnel hours per subtask. The discrepancy between the estimated number of hours devoted to technology research and the actual hours is due to recategorizing the technology research during the design phase to the appropriate subtask within “Design”. The actual personnel hours already logged on project definition technology considerations, Project Plan, and Design Report are shown as italicized values.

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Table 7.53 – Estimated Person Hours (Revised)

Vee

Shi

natra

kool

Mar

gare

t Sha

ngle

Tara

Spo

den

John

Vol

kens

Bria

n Y

auk

TotalTask 1: Definition 5 4 5.5 5.5 5 25Task 2: Technology 25 16 17.5 9.5 17 85Task 3: Design

Hardware: Interface 4.5 4.5 6.75 11.25 18 45Hardware: Sonar -- 4 -- -- 36 40Hardware: Orientation -- 1.5 3 -- 25.5 30Hardware: Motor Control -- -- 11.25 33.75 -- 45Hardware: Localization 6 51 3 -- -- 60Software: Interface 8.75 -- 11.25 5 -- 25Software: Mapping 2 -- 13 5 -- 20Software: Obstacle Avoidance 2.5 -- 16.25 6.25 -- 25

Task 4: Prototype Hardware: Interface -- 4.5 1.5 0.75 8.25 15Hardware: Sonar -- 1.25 3.75 -- 20 25Hardware: Orientation -- 1 3 -- 16 20Hardware: Motor Control -- 1.5 8.5 -- -- 10Hardware: Localization 4 36 -- -- -- 40Software: Interface 9 -- 1 10 -- 20Software: Mapping 24.75 -- 2.75 27.5 -- 55Software: Obstacle Avoidance 27 -- 3 30 -- 60

Task 5: Testing Hardware: Interface -- 16 4 2 18 40Hardware: Sonar -- 1 3 -- 16 20Hardware: Orientation -- 2.25 6.75 -- 36 45Hardware: Motor Control -- 3.75 21.25 -- -- 25Hardware: Localization 7.5 67.5 -- -- -- 75Software: Interface 13.5 -- 1.5 15 -- 30Software: Mapping 27 -- 3 30 -- 60Software: Obstacle Avoidance 40.5 -- 4.5 45 -- 90

Task 6: Demonstration 6 15 27 6 6 60Task 7: Documentation

Weekly Status Reports 16 -- -- -- -- 16Website Maintenance -- -- 16 -- -- 16Project Plan 12 13 21 19 16 81Design Report 12 18 24 14 27 95Poster 1.5 3 22.5 1.5 1.5 30Final Report 12.75 17 25.5 12.75 17 85

Group Total 267.25 281.75 291 289.75 283.25 1413

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7.2 Other Resources

Table 7.54 is breakdown of equipment and associated cost required to complete the project. The resource requirements reflect the choice of technology. The cost of the technologies remains an estimate from industry prices on the internet and is subject to change. This is a recategorization of some of the costs originally reported as Material and Labor Costs in the Project Plan. There were no original estimates categorized as “Other Resource Requirements”.

Table 7.54 – Other Resource RequirementsItem Cost Estimate

Devantech R117 Magnetic Compass (x1) $52.00ADXRS150 Angular Rate Sensor (x1) $64.95SRF04 Sonar Sensor (x13) $360.36RFID Reader & Eval Kit (x1) $200.00RFID Tags * ~(x250) --EPIA-EN12000EG Mini-ITX (x1) $226.95LabVIEW Embedded 8.2 ** (x1) --

Total $904.26* Previously donated to Senior Design by MetalCraft** Provided by National Instruments

7.3 Financial Requirements

The financial requirements are a breakdown of the cost of the project. This will represent the total cost associated with other resources, project deliverables, and labor at $10.50 per hour. The original financial requirements estimates in Table 7.55 have been updated as shown in Table 7.56, reflecting the changes mentioned in the Other Resources section and revised labor estimates.

Table 7.55 – Material and Labor Costs (Original)Materials Cost Estimate Poster $50.00 Sensors $500.00 Wheel Chair * -- RFID equipment * -- CMD500 series board ** -- EPIA-EN12000EG Mini-ITX $226.95 Mounting Equipment $100.00 Wiring and Misc. Equipment $50.00

Subtotal $926.95

Labor Hours Labor ($10.50 per hour) Tara Spoden 240 $2,520.00 Brian Yauk 235 $2,467.50 Margaret Shangle 220 $2,310.00 Vee Shinatrakool 205 $2,152.50 John Volkens 250 $2,625.00

Subtotal $12,075.00Total $13,001.95

* Provided by Senior Design** Provided by National Instruments

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Table 7.56 – Material and Labor Costs (Revised)Materials Cost Estimate

Poster $50.00Other Resources $904.26Mounting Equipment $100.00Wiring and Misc. Equipment $50.00

Subtotal $1104.26Labor Hours Labor ($10.50 per hour)

Tara Spoden 291 $3,055.50Brian Yauk 283.25 $2.974.16Margaret Shangle 281.75 $2,958.38Vee Shinatrakool 267.25 $2,806.16John Volkens 289.75 $3,042.38

Subtotal $14,836.58Total $15,940.84

* Previously donated to Senior Design by Invacare

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Schedules

8 Schedules

The figures in this section illustrate the project task schedules and deliverable timelines in the form of Gantt charts. A comparison of the original and updated schedules for the fall semester of 2006, shown in Figure 8.22 and Figure8.23 respectively, indicates that the group has had to deviate from the original projections under certain phases of the project.

Figure 8.22 – Fall 2006 Task Schedule (Original)

Figure 8.23 – Fall 2006 Task Schedule (Revised)

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Furthermore, the original task schedule for the spring semester of 2007 in Figure 8.27 has been updated and revised as shown in Figure 8.25.

Figure 8.24 – Spring 2007 Task Schedule (Original)

Figure 8.25 – Spring 2007 Task Schedule (Revised)

Additionally, the original timetables for the deliverables schedule shown in Figure 8.26, have been updated to reflect an extension in the Design Report submission date in Figure 8.27.

Figure 8.26 – Full Project Reporting and Deliverables Schedule (Original)

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Figure 8.27 – Full Project Reporting and Deliverables Schedule (Revised)

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Project Team Information

9 Project Team Information

This section contains contact information about the client, faculty advisor, and team members involved in the project.

Client:

Company: National InstrumentsContact: Andrew DoveEmail: [email protected] (office): (512) 683-8409Phone (fax): (512) 683-6837Mailing Address:

National Instruments 11500 N Mopac Expwy Austin, TX 78759-3504

Faculty Advisor:

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Name: Dr. Nicola EliaEmail: [email protected]: 3131 CooverPhone (office): (515) 294-3579

Phone (fax): (515) 294-8432Mailing Address:

Iowa State University 3131 CooverAmes, IA 50011-3060

Team Members:

Name: Margaret ShangleMajor: Electrical EngineeringEmail: [email protected] (cell): (515) 450-4812Phone (home): (515) 292-4872Mailing Address:

2239 Knapp St.Ames, IA 50014

Name: Vee ShinatrakoolMajor: Computer EngineeringEmail: [email protected] (cell): (515) 708-0720Mailing Address:

4212 Westbrook Dr #22Ames, IA 50014

Name: Tara SpodenMajor: Electrical EngineeringEmail: [email protected] (cell): (563) 581-7454Mailing Address:

4532 Steinbeck St #110Ames, IA 50010

Name: John VolkensMajors: Computer EngineeringEmail: [email protected] (cell): (515) 290-6204Phone (home): (515) 572-5324Mailing Address:

Iowa State University1265 Friley Dodds Ames, IA 50012

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Name: Brian YaukMajor: Electrical EngineeringEmail: [email protected] (home): (515) 572-0499Mailing Address:

Iowa State University4225 Willow Lancaster Ames, IA 50013

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Closing Summary

10 Closing Summary

The design proposed for this project is a complex integration of several major components. Since multiple inputs must be analyzed and used to perform detailed calculations, a central processing unit in the form of a Mini-Itx board will be used. This device will receive input from the ultrasonic ranging modules which will indicate distances to obstacles in the environment. The controller will also receive input from the gyroscope and compass indicating the orientation of the wheelchair. The importance of localization and the ability to determine the wheelchair’s present location at any given time during travel requires the use of a technology such as RFID to identify the environment. The controller will receive identification information about RFID tags in the area of its current location.

Processing the inputs will require a complex obstacle avoidance and path calculation algorithm to be programmed and computed within the controller using LabVIEW Embedded. There will also be an onboard map stored in memory which the controller will use for reference incoming data. The calculations indicating direction of travel of the wheelchair will be output from the controller and converted into an analog signal recognizable by the motor control box.

This system has been designed to meet the functionality requirements of the project and demonstrate the ability of LabVIEW Embedded to communicate through target VIs with multiple forms of hardware. The implications of this project in the medical world which should be sufficient to resolve staffing issues that arise from transport of wheelchair-confined patients.

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Appendix A

11 Appendix A

Axiom CMD565 Evaluation Board Specifications

The CMD-565 system provides the CMD-5xx Motherboard and the PM-565 Personality Module to provide a MPC565 development environment. The system is Plug and Play with the supplied Axiom Monitor in the on-board EPROM. Board features 2MByte (512K x 32) Synchronous SRAM, 4MByte (1M x 32) Burst Flash EEPROM, Communication Interfaces, Port Replacement Logic Unit, Keypad and LCD Module support, Serial Cable, Wall Plug power source, printed hardware manual and the MPC5xx support CD with programming utilities, support and sample software, and technical manuals.

Standard Features:

Global Wall-Plug Power Supply (CE certified) Processor in socket on PM-5xx board with ZIF socket Mictor Logic Connectors for Address, data, and control signals AMD AM29BL160 type synchronous flash

PM-565 Features:

4Mhz reference Crystal Oscillator with large landing pads for easy value change BDM and Nexus 50 pin Development port connectors POR and Hard Reset buttons Voltage Indicators Reset Indicator Reset Configuration Switch for clocking options, enabling external configuration of operating mode or

programming Stack connectors mapped for signal functionality

CMD-5XX Motherboard Features:

Standard fixed memory (buffered): 512K x 32 Sync. SRAM (100MHz), 1M x 32 Burst Flash EEPROM Two Configurable 32pin memory sockets for 32K to 2MByte EPROM with 8 or 16 bit wide data bus,

Axiom Monitor installed standard PRU - Port Replacement Unit provided for MPC555 ports A, C, and D allow simulation of single chip port

operation when expanded bus is operating MAP Switch - provides easy assignment of chip selects to ram and flash memory banks MODE Switches - 4 DIP switches to fully support Hard Reset Word Configuration options COM Switch - provide easy method of applying or isolating serial connections to RS232 transceiver COM1 - SCIA1 w/ RS232 type DB9-S Connection COM2 - SCIA2 w/ RS232 type DB9-S Connection COM3, 4 - Not applied on MPC555 CAN Ports - 2 CAN transceiver (PCA82C250) interfaced ports, 1 x 4 headers LCD Port - LCD Module Interface Connector w/ Contrast Adjust, Buffered and Memory Mapped KEYPAD and KEY Port - 16 Key or 20 Key interface, Debounced, Buffered, and Memory Mapped BUS Port - provides 32 data and 24 address or MPC555 ports A and D on 60 pin header CONTROL Port - Bus Controls for MPC555 ports on a 44 pin header

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QSM Ports - 2 Serial I/O ports with 16 pin socket headers MIOS Port - MDA, PWM, and MGP timer or I/O interface with 34 pin socket header TPU Ports - 2 Timing Processor I/O ports with 20 pin socket headers QADC Ports - 2 Analog I/O ports, one 20 pin and one 24 pin socket header INT Port - Interrupt or MPC555 SGP port I/O with 10 pin header POWER Port - Primary and standby power supply access port I/O Connectors in .1 grid, pin headers for bus and control provide easy ribbon cable connection for external

connections. Socket headers provide easy wire connection to breadboard prototype area or with pin headers installed, will allow ribbon cable or wire wrap connections

Mictor Logic Probe connectors for Bus and Control signals Large Prototyping Area (5 x 1.75 inch) with +5V and ground connection grids Breadboard Prototyping area (2.5 x 1.5 inch) for easy installation of test connections Power Indicators - Supply voltage indications for 5, 3.3, and 2.6V supplies Reset Switches - POR, Hard, Soft reset buttons User Indicators - 4 user indicators to provide user conceived visual response during testing CE certified class A as shipped with universal power supply

Other Specifications: Power Supply - 6 to 20VDC Input, 300ma typical @ 9VDC 5.0V @ 2.5A output with 3.3V, and 2.6V regulated supplies Board Size - 8 x 9.5 inch

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Appendix B

12 Appendix B

Handy Board Specifications

Features:

52–pin Motorola 6811 microprocessor with system clock at 2 MHz 32K of battery-backed CMOS static RAM Two L293D chips capable of driving four DC motors 16 _ 2 character LCD screen Two user-programmable buttons, one knob, and piezo beeper Powered header inputs for 7 analog sensors and 9 digital sensors Hardware 38 kHz oscillator and drive transistor for IR output and on-board 38 kHz IR receiver 8-pin powered connector to 6811 SPI circuit (1Mbaud serial peripheral interface) Expansion bus with chip selects allows easy expansion using inexpensive digital I/O latches

Other Specifications: Power Supply - 12 volt, 500 mA DC outputInternal 9.6V NiCad battery with built-in recharging circuitBoard Size - 4.25 x 3.15 inch

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Appendix C

13 Appendix C

EPIC AMD™ Geode GX2 Low Power SBC - EPX-GX

Features:

AMD Geode™ [email protected] processor EPIC-compliant board 128 to 512MB of system PC2700DDR SDRAM supported in a 200-pin SODIMM socket Type I and II CompactFlash (CF) cards supported PC-compatible supports Linux, Windows® CE and XP embedded, plus other x86-compatible RTOS High-resolution video controller supports • Color panels supported with up to 18-bits/pixel • Panel resolutions up to 1280 x 1024 • Backlight power supported • CRT supports 1600 x 1200 pixels 10/100 Mbps Intel PCI Ethernet controller 4 RS-232 serial ports with FIFO, COM1 & COM2 with optional RS-422/485 support Bi-directional LPT port supports EPP/ECP 24 bi-directional TTL digital I/O lines (WS16C48) Two USB 1.1 ports onboard MiniPCI connector for 802.11 a/b/g wireless module Floppy disk controller supports up to 2 drives Ultra DMA 66 EIDE hard disk controller Optional 12-bit A/D with up to 8 SE or 4 DI channels, with independent software programmable input

ranges of ±5V, ±10V, 0-5V, and 0-10V AC97 Audio supports 6 channels (5.1 surround) PC/104 and PC/104- Plus expansion connectors AT keyboard controller and PS/2 mouse support GPS support via external serial module Activity LEDs onboard for visual status Two interrupt controllers and 7 DMA channels Three, 16-bit counter/timers -40°C to +85°C operating temperature range +5 volt only operation and low power Up to 2 minute reset on watchdog timer Real time clock, and power fail reset Small size: 4.5 " x 6.5" (115 mm x 165 mm)

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Overview:

The EPX-GX is an AMD Geode [email protected], EPIC-compatible single board computer (SBC). AMD Geode processors have extremely low power dissipation which allows fanless operation.

The EPX-GX supports 9 different functions providing a processor and I/O-intensive solution for demanding applications. Applications include test equipment, medical instruments, communications devices, transportation systems, military/COTS, data loggers, security,robotics, semiconductor manufacturing instruments, and industrial control systems.

The board is configured with up to 512MB of PC2700 DDR SDRAM plus a CompactFlash (CF) memory socket. Also, a 10/100 Ethernet controller, video with CRT and flat panel interfaces, four serial COM channels, 24 digital I/O lines, 6 channels of AC97 audio, and the standard AT peripheral feature set are included.

The EPX-GX measures 4.5 x 6.5-inches (115mmx165mm) and is compliant with the EPIC (Embedded Platform for Industrial Computing) standard. It offers additional I/O expansion with PC/104 and PC/104-Plus connectors or with two high-speed USB 1.1 channels.It also supports 2 floppy disk drives and two Ultra-DMA 33/66 IDE drives.

There is a socket for bootable Type I and II Compact-Flash cards. The EPX-GX2 also includes a socket for a miniPCI wireless 802.11 a/b/g card. Plus a connector is included to support a remote GPS receiver.

The board will operate from - 40° to +85°C without a requiring a fan, for rugged embedded applications. It is ideal for low-power, high-performance, battery-powered and portable applications.

Software Support:

Software - The EPX-GX is an x86-compatible SBC. It is designed to run both 16-bit and 32-bit x86 instruction set software and is compatible with Microsoft's Windows® CE and XP operating systems as well as the applications that run on them. It also supports Linux and other operating systems such as QNX or VxWorks. Its x86-PC software compatibility assures a wide range of tools to aid in developing and checkout of your application’s program.

Software Developers Kit - WinSystems offers the SDK4 software developers kit to provide the necessary hardware, software and cables to begin program development with the EPX-GX board. The configuration consists of an operating system, CD-ROM drive, a 20 GB or larger hard disk, a 1.44 MB high density 3.5-inch floppy disk, plus required cables and triple output power supply housed in an enclosure. This packaging permits easy access to the board, PC/104 modules and peripherals during program development.

Specifications:

Electrical EPX-GX CPU AMD Geode [email protected] PC/104 Interface: 16-bit, non-stackthrough PC/104- Plus Interface: 32-bit PCI, non-stackthrough Ethernet data rate: 10/100 megabits per second USB Interface: Two USB 1.1-compliant ports Serial Interface: 4 Serial channels with RS-232 levels plus RS-422/485 on COM1 and COM2 LPT Interface: Bi-directional LPT with ECP/EPP Parallel Interface: 24 I/O lines, TTL compatible UDMA66/33 EIDE interface: Supports 2 drives Floppy Disk Interface: BIOS supports one or two 360K/720K/1.2M/1.44M drives Vcc = +5V ±5% at 1.5 Amps typ.System Memory: Addressing: Up to 512 Megabytes 200-pin SODIMM DDR memorySolid State Disk: Device: One Type I or II CompactFlash cardMechanical: Dimensions: 4.5" x 6.5" (115mm x 165mm)Environmental: Operating Temperature: - 40°C to +85°C

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Appendix D

14 Appendix D

VIA EPIA-EN12000EG Mini-ITX Motherboard with VIA C7 1.2GHz Specifications

Features:

52–pin Motorola 6811 microprocessor with system clock at 2 MHz VIA EPIA EN12000G 1.2GHz VIA C7 nanoBGA2 Fanless Processor 1.2GHz VIA Eden nanoBGA2 Fanless Processor Onboard VIA CN700 Chipset with Integrated VIA UniChrome Pro AGP Graphics with MPEG-2 Decoding

Acceleration DDR2 533 SDRAM 1 PCI slot ATA 100/133 & 2 SATA ports Support VIA Vinyl 8 Channel Audio VIA IEEE 1394, 6 USB 2.0 ports & 2 COM ports VIA Gigabit Ethernet VIA TV Out (HDTV Resolution) LVDS/DVI (an add-on card is required) Mini-ITX Form Factor (170mm X 170mm) RoHS Compliant

Specifications:

Processor 1.2GHz VIA Eden nanoBGA2 Processor

Chipset VIA CN700 North Bridge VIA VT8237R Plus South Bridge

System Memory 1 DDR2 400/533 DIMM socket Up to 1 GB memory size

VGA Integrated VIA Unichrome Pro AGP graphics with MPEG-2 decoding acceleration

Expansion Slots 1 PCI

Onboard IDE 2 X UltraDMA 133/100/66 Connectors

Onboard LAN VIA VT6122 GLAN Controller

Onboard Audio VIA VT1618 8-channel AC'97 Codec

Onboard TV Out VIA VT1625M HDTV Encoder

Onboard 1394 VIA VT6307S IEEE 1394 Firewire

Back Panel I/O

1 PS2 mouse port 1 PS2 keyboard port 1 VGA Port 1 Serial port 1 RJ-45 port 4 USB 2.0 ports 1 RCA port (S/PDIF or TV out) 1 S-Video port 3 Audio jacks: line-out, line-in and mic-in (Horizontal, Smart 5.1 Support)

Onboard I/O Connectors 1 USB connector for 2 additional USB 2.0 ports 1 1394 connector for 1 1394 port 2 SATA Connectors 1 Front-panel audio connector (Mic-in and Line Out) 1 Serial port connector for a second com port

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1 LPT connector 1 CIR connector (Switchable for KB/MS) 1 SIR pin header (IrDA 1.0) 2 Fan connectors: CPU/Sys FAN 1 SMBUS connector 1 S/PDIF in connector 1 S/PDIF out connector 1 LVDS/TTL/DVI module connector (an add-on card is required) 1 Component (YPbPr) video pin header ATX Power connector

Operating System Windows 2000/XP, Linux, Win CE/XPe

Software Application VIA FliteDeck Utility MissionControl-H/W Monitoring, Remote SNMP Management FlashPort-Live BIOS Flash

23 [?] TVI Electronics Online Store. Touch Screen LCD Module TM1B5BW. 15 November 2006. http://shop-on-line.tvielectronics.com/product_info.php?pName=touch-screen-lcd-module&cName=touch-screen-lcd-modules

1 [?] Axiom Manufacturing. CMD-565 Motorola Oak Series Development Board Features. 4 November 2006. http://www.axman.com/Pages/neuroprod8_cmd565.html

2 [?] Margin, Fred G. The Handy Board Technical Reference. 4 November 2006. http://www.handyboard.com/techdocs/hbmanual.pdf

3 [?] Gleason Research. The Handy Board System. 4 November 2006. http://www.gleasonresearch.com/products.phtml

4 [?] WinSystems. EPIC AMD™ Geode GX2. 29 November 2006. http://sbc.winsystems.com/products/sbcs/epxgx2.html

5 [?] Mini-Box. VIA EPIA-EN12000EG Mini-ITX Motherboard. 4 November 2006. http://www.mini-box.com/VIA-EPIA-EN12000EG?sc=8&category=99

6 [?] Active Robots. Devantech SRF04 Ultra Sonic Ranger Module. 8 November 2006. http://www.active-robots.com/products/sensors/sensors-devantech.shtml

7 [?] Acroname, Inc. Devantech SRF235. 10 November 2006. http://www.acroname.com/robotics/parts/R254-SRF235.html

8 [?] Acroname, Inc. SensComp Instrument Package. 10 November 2006. http://www.acroname.com/robotics/parts/R14-SONAR1.html

9 [?] Acroname, Inc. Sharp GP2D05 IR Ranger. 10 November 2006. http://www.acroname.com/robotics/parts/R21-IR05.html

10 [?] Acroname, Inc. Sharp GP2Y0A02YK IR Sensor. 10 November 2006. http://www.acroname.com/robotics/parts/R144-GP2Y0A02YK.html

11 [?] Acroname, Inc. Hokuyo URG-04LX Laser Sensor. 10 November 2006. http://www.acroname.com/robotics/parts/R283-HOKUYO-LASER1.html

12 [?] Acroname, Inc. Devantech Compass. 10 November 2006. http://www.acroname.com/robotics/parts/R117-COMPASS.html

13 [?] Bartolini, Daniel. Analog Devices ADXRS150 Angular Rate Sensing Gyroscope. 8 November 2006. http://itp.nyu.edu/physcomp/sensors/Reports/ADXRS150

14 [?] Spark Fun Electronics. Gyro Breakout Board - ADXRS150. 10 November 2006. http://www.sparkfun.com/commerce/product_info.php?products_id=396

15 [?] US Digital, Inc. MA2 Miniature Absolute Magnetic Shaft Encoder. 8 November 2006. http://www.usdigital.com/products/ma2/

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SysProbe-Live DMI Browser

System Monitoring & Management

CPU temperature reading, CPU voltage monitoring Wake-on-LAN, Keyboard-Power-on, Timer-Power-on Watch Dog Timer, FAN control System power management, AC power failure recovery

16[?] Digi-key. IC CONVERTER D/A 8BIT 16-DIP. 3 December 2006. http://www.digikey.com/

81


References

15 References

17 [?] Trident. POS Keypad GPA 400 PIN Pad. 12 November 2006. http://www.trident-uk.co.uk/point_sale/epos_keypad.html

18 [?] ComputerGeeks.com. Targus USB Numeric 19-Key Mini Keypad (Silver). 12 November 2006. http://www.geeks.com/details.asp?invtid=PAUK10U-PB&cat=KYB

19 [?] ComputerGeeks.com. Kensington Pocket KeyPad w/2-Port USB Hub. 12 November 2006. http://www.geeks.com/details.asp?invtid=33006-DT&cat=KYB

20 [?] Phidgets. PhidgetTextLCD 20X2 : Blue : Integrated 8/8/8 InterfaceKit. 12 November 2006. http://www.phidgets.com/index.php?module=pncommerce&func=itemview&KID= 1165288346205.241.141.184&IID=116

21 [?] Ituner Networks Corp. picoLCD 20x2 (OEM). 12 November 2006. http://www.mini-box.com/picoLCD-20x2-OEM

22 [?] TVI Electronics Online Store. Optrex Monochrome Graphic Series Displays. 12 November 2006. http://www.tvielectronics.com/Optrex_F-51553_LCD.html

24 [?] Acroname, Inc. Devantech SRF04 Ranger. 10 November 2006. http://www.acroname.com/robotics/parts/R93-SRF04.html

25 [?] Robot Electronics, Inc. SRF04 - Ultra-Sonic Ranger Technical Specification. 8 November 2006. http://www.robot-electronics.co.uk/htm/srf04tech.htm

26 [?] Robot Electronics, Inc. CMPS03 - Robot Compass Module. 8 November 2006. http://www.robot-electronics.co.uk/htm/cmps3doc.shtml

27 [?] Analog Devices, Inc. ADXRS150 - Angular Rate Sensor ADXRS150. 8 November 2006. http://www.analog.com/en/prod/0%2C2877%2CADXRS150%2C00.html

28 [?] Crystalfontz America, Inc. CFAH2004A Standard LCD Modules. 12 November 2006. http://www.crystalfontz.com/products/2004a/CFAH2004AYYHJPE.pdf

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