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Robotic Arm & Dexterous Hand Senior Design 05911 04013

Robotic Arm & Dexterous Hand Senior Design

Critical Design Report

Project 05911David Parrett

Wen Jia WangJustin Tubiolo

Jeremy AmidonKen Peters

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Executive Summary

The purpose of this report is to describe the design process of an interactive robotic arm and hand to be placed in a museum environment for the enjoyment of children. It was the intention of the Rochester Museum and Science Center (RMSC) for the team to propose various exhibit ideas that utilize robotics and then to develop one of these ideas into a working exhibit for actual display and use in the museum. With a large emphasis on the word "fun," the team set about to find a creative and inspiring idea that would not only appeal to children but also serve to enhance their creativity and learning. The end result was the concept of a robotic arm and dexterous hand which the children can control through use of a wearable glove that tracks the movements of their hand, arm, and fingers. The robotic arm and dexterous hand are used inside of an enclosed area to move, lift, and otherwise interact with various objects inside of the display area. The main goal for the team has been to allow children to successfully transfer their movements to the movements of the robotic arm and hand while keeping it fun and exciting for the children.

By using the Engineering Design PlannerTM methodology, the team was able to design the Robotic Arm and Dexterous Hand through five different facets.

The first facet of the design is called Recognizing the Need and Defining the Problem. The team has spent a large part of this past design period conferring with the RMSC to establish the needs for this project. Issues such as safety, repair, interaction, and learning have all been discussed along with the usual issues of normal operation. In order to choose the project, a list of project proposals was created and submitted to the sponsor. Once the project was decided and key issues and objectives had been defined, it was important that the team propose many different concepts for the museum to choose from and then to further develop the final project idea into a list of necessary components and activities. This Concept Development is included as the second facet of this report. The third facet, Feasibility Assessment, is concerned with analyzing the different design alternatives to meet a specific need in the design. Choices such as whether to design and manufacture a specific component or to buy one pre-manufactured are considered while weighing the costs and benefits of each decision. The resulting design choices then allowed the team to generate the fourth facet, Specifications for how exactly the robotics will mechanically and electrically work. Using these decisions and specifications, the team then took the final step in the design process, Analyses and Synthesis, to finalize and fill in the design details including technical drawings and algorithms.

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Executive Summary.......................................................................................................21.0 RECOGNIZE AND QUANTIFY NEEDS................................................................6

1.1 Mission Statement......................................................................................................61.2 Project Description.....................................................................................................61.3 Scope Limitations.......................................................................................................81.4 Stakeholders................................................................................................................81.5 Key Business Goals....................................................................................................91.6 Top Level Critical Financial Parameters..................................................................101.7 Financial Analysis....................................................................................................101.8 Market.......................................................................................................................111.9 Order Qualifiers........................................................................................................111.10 Order Winners..........................................................................................................11

2.0 PROJECT PROPOSALS....................................................................................122.1 Robotic Arm and Dexterous Hand...........................................................................122.2 Robotic Squirt Gun and Targets...............................................................................132.3 Remote Racing and Track........................................................................................152.4 Robotic Arm Wrestling.............................................................................................162.5 Remote Soccer Players.............................................................................................182.6 Robotic Basketball Shooter......................................................................................192.7 Interactive Maneuverable 3-D Maze........................................................................202.8 Conclusion................................................................................................................22

3.0 Concept Development.......................................................................................233.1 Controls.....................................................................................................................23

3.1.1 Sensor Laced Glove & Fighter Style Joystick..........................................................233.1.2 Sensor Glove with Motion Track..............................................................................24

3.2 Arm Types................................................................................................................253.2.1 Wrist, Elbow, & Shoulder Joints..............................................................................253.2.2 Wrist, Elbow & Rotating Cylinder Joints.................................................................26

3.3 Source of Mechanical Power....................................................................................263.3.1 Pneumatics................................................................................................................263.3.2 Electric Motors.........................................................................................................273.3.3 Hybrid System...........................................................................................................28

3.4 Electronic Data and Control System.........................................................................293.4.1 PC with an output board...........................................................................................293.4.2 Microcontroller Development Board Alone.............................................................293.4.3 PC with a Microcontroller Development Board......................................................30

4.0 Feasibility...........................................................................................................314.1 Project Feasibility...............................................................................................................314.2 Controller Feasibility................................................................................................324.3 Arm Feasibility.........................................................................................................334.4 Electronic Control Feasibility...................................................................................34

5.0 OBJECTIVES & SPECIFICATIONS......................................................................355.2 Design Objectives.....................................................................................................355.2 Performance Specifications......................................................................................365.3 Design Practices........................................................................................................365.4 Safety Issues.............................................................................................................37

6.0 DESIGN ANALYSIS & SYNTHESIS...................................................................38

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6.1 Display Analysis & Synthesis..................................................................................386.2 Hand Design Analysis and Synthesis.......................................................................396.3 Forearm Design Analysis and Synthesis..................................................................416.4 Upper Arm Design Analysis and Synthesis..............................................................426.5 Equations Used for Mechanical Design Analysis and Synthesis.............................436.6 Electrical Control......................................................................................................446.6.1 Electrical Input and Output.......................................................................................446.6.2 Electrical Control Algorithm....................................................................................446.6.3 PC Program in C++..................................................................................................456.6.4 Microcontroller Program for 8051 MCU.................................................................45

7.0 DELIVERABLES.................................................................................................467.1 The Robotic Arm and Hand Display.......................................................................467.2 The Robotic Arm and Hand User’s Guide..............................................................467.3 The Complete Parts List with Vendors....................................................................46

8.0 PROJECT TIMELINE..........................................................................................479.0 PROJECT BUDGET...........................................................................................48

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1.0 RECOGNIZE AND QUANTIFY NEEDS

1.1 Mission Statement

The purpose of this senior design team is to create a robotics display for the

RMSC which is fun, inviting, accessible, and easy to understand and use. The new

display will be a robotic arm and dexterous hand which will copy the movements of the

user's hand in a glove controller. The robotics display will be suitable for placement and

use on the museum floor as a working exhibit to be used especially by children ages 8-14.

1.2 Project Description

Robotics is a field of technology in which there is a great demand and natural

curiosity to explore what intelligent machines can do to help people. A robot can be

either very intelligent and responsive to its natural environment, or it can perform a set

task without any intelligent response. In this project it is important for the safe and

normal operation of the robot, that it respond to its environment by detecting when it has

reached its fullest extent of motion or has collided with an immovable object to cease

movement in that direction. It is also important for the robot to maintain a smooth, steady

motion which corresponds to how the user desires the robot to move.

Besides simply moving around and mimicking the motion of the human hand and

arm, the robot will also be capable of performing three or four tasks which will present a

small challenge and add interest to the display. It was mentioned by the RMSC that the

arm should perform activities that could not easily be done by the children with their own

hands. One possible example of this is to allow the robot to pick up a basketball with one

hand and place it in a basket. Another possibility is to have the robot pick up a

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Fig 1-1: Robotic Arm and Dexterous Hand Basic Setup

recognizably heavy object such as a construction brick and be able to stack several of

them together. Other possible activities could be placing odd-shaped objects through

corresponding holes, and touching the robotic hand to a target where the hand will

conduct electricity to turn on a light.

The basic shape and layout of the exhibit is demonstrated in Figure 1-1. The arm

is shown supported from above the display table where the various objects for interaction

will be located. The arm features rotational movement at the mounting point to allow it to

swivel from side to side. Just below this rotational motor is located a cylinder which

allows the arm to extend and retract give the arm variable reach. Below the extension

cylinder is the elbow joint for the arm allowing it to bend in various life-like postures. On

the forearm section below the elbow joint will be placed air muscles which will allow the

wrist and individual fingers of the hand to bend.

The control area is located in front of the display case and houses the glove

controller. In order to save wear and tear on the controller and allow the glove to operate

properly with the sensor, it is necessary to surround the glove on all but one side to limit

the user's freedom of movement. The limitation allows the user enough freedom to move

the glove in all directions for between one to two feet from center and keeps the glove on

a restraining leash to make sure it remains with the exhibit.

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1.3 Scope Limitations

One major idea which the team is striving for is to avoid reinventing and

remanufacturing pre-existing design components. It is necessary for the team to purchase

working components in nearly all cases to keep the cost low and provide the working

prototype by the established deadline. Though it would be possible to completely design

and manufacture the project from scratch, especially the glove controller, this would

require much more design, manufacture, and test time than is available for this project.

The team is limited, to a degree, by the $5000 budget but the team does not

believe that the project will need to cost more than this. Responsible spending and good

component choices are important to staying within this budget constraint. The RMSC

has been very supportive in promising facilities such as a compressed air line for

pneumatics components and has showed a desire to avoid placing creative limits on the

project in general wherever possible.

The major constraint of the project is the schedule which is set to a strict timeline

with two main deadlines. At the end of the fall quarter, 20041, the team must deliver the

detailed design package, quotes for vendors, and the proposed budget. By the end of the

winter quarter, 20042, the team will provide the working prototype, the final report, and

test results of both the operational specifications and human interactive requirements.

1.4 Stakeholders

The main stakeholders in this project are the project sponsor, Rochester Museum

and Science Center, and the senior design team members. The Museum has a large stake

because of the possibly huge attraction and technologically-advanced image that this

project could bring to the RMSC should it be integrated successfully as an exhibit there.

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The senior design team members also have stake in this project as a demonstration of

their ability to solve engineering problems and gain invaluable experience in the

expanding field of Robotics. The team's faculty advisors and the college of engineering

also has stake in the project because of the potential for future sponsorship of senior

design projects by the RMSC. Outside vendors are also stakeholders which the team shall

be purchasing many of the commonly manufactured parts for integration in the design.

More stakeholders include the members of future RIT robotics senior design teams, other

schools doing research on miniature turbines that could benefit from our results, any

other designers and users of publicly exhibited robotics, and the future employers of the

team members.

1.5 Key Business Goals

A successful project will be defined by the evidence of a working robotic arm and

dexterous hand prototype achieving full dexterity, range of motion, and control by the

user to manipulate the objects inside the display. If the design team is capable of

completing such a task, then much will have been accomplished. Not only will the core

objectives of the project be achieved, the students on the team will have also gained a

valuable experience in working within a multidisciplinary team. The results of this

project will serve as a tangible incentive for further development by museums in robotics

displays. Success of this project will bring future opportunities for attracting a wide group

of interested young people into the museum, and possibly eventually into the study of

engineering and the field of robotics.

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1.6 Top Level Critical Financial Parameters

The financial needs of this project are driven primarily by the purchase of the

individual components that will be assembled for the mechanical robotic function. The

major electrical system contributors to the overall cost include a personal computer and

microcontroller development board. The major mechanical cost contributors include the

pneumatic system, including air muscles, air lines, and valves, along with the mechanical

joints, motors, and extension cylinder. There may also be small fees due to persons

external to the team, who are responsible to manufacture various mechanical components

but these will be relatively small in comparison to off-the-shelf mechanical purchases.

1.7 Financial Analysis

The team is working with a $5000 dollar budget cap in mind. The RMSC will work

with the team to determine which possible budget items can be donated and which will

need to be purchased. The plan for spending is to purchase the major components of the

design that are absolutely necessary by the Preliminary Design Review and at an early

stage of assembly in the following quarter to ensure that they will be properly integrated

and to allow for a fallback period if necessary. The $5000 dollar limit is deemed by the

team to be sufficient for this project; however there are several design options which, if

chosen, would add to the cost significantly. The electrical components will require an

estimated five hundred to seven hundred dollars and the majority of funds will go to the

mechanical side of the project including, but not limited to:

Pneumatic component cost: air muscles, valves, and lines

Mechanical control components: extension cylinder and electric motors

Material and machining cost: hand and finger joints

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1.8 Market

The Robotic Arm and Dexterous Hand Display is intended to be used exclusively

by the RMSC. Though the design and concepts used throughout this project will be

available to the RIT community and could prove useful to similar projects in the future, it

is not intended that this project be reproduced for public marketing and distribution.

1.9 Order Qualifiers

The purpose of this research design is to provide a fun and interactive display for

use in a museum exhibit by children. The robot needs to satisfy this requirement by

allowing the user to control it simply and easily which will translate to an efficient and

pleasing operation of the robotic mechanism. The operation must involve the ability to

move fingers, hand, and arm throughout the display unhindered, and it must allow the

user to interact with the objects inside the display in an intuitive manner.

1.10 Order Winners

If time and money permit the team will work to complete the following goals:

Design and build to ensure maximum exhibit life span and durability.

Provide for intuitive navigation and operation by users.

Allow the robotics theme to be an exceptionally inviting "attractor factor."

Provide for accessibility to many users of different age and physical ability.

Provide maintenance information such as drawings and replacement parts.

Make the user feel as though the robotics exhibit is an extension of them self.

Test the display in its target museum environment to ensure its success.

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2.0 PROJECT PROPOSALSThe RMSC requested that the team brainstorm and propose various robotics

display ideas to be considered for this project. The ideas were in many different

directions but always centered on being interactive and inviting to children. The

following are the seven project ideas which were proposed.

2.1 Robotic Arm and Dexterous Hand

2.1.1 Overview

This design concept incorporates a robotic arm with a fully functional robotic

hand. The arm and hand could be used to complete various tasks like stacking

blocks or lifting and moving heavy objects. The robot would be contained in a

display case that would be easily viewed by the operator as well as spectators.

2.1.2 The "Attractor Factor"

The sight of the robotic arm and hand should be a significant draw. Also, the

controls will draw people to try the glove and joysticks.

2.1.3 Method of Interaction

The arm and hand would be controlled by sensor-laced glove and one to two

joysticks. Patrons would put the glove on and the robotic hand would mimic the

movements of their hand. The joysticks would be used to control the motion of

the robotic arm. We would explore the possibilities of incorporating different size

gloves like a small, medium, and large to increase the range of ages allowed to

operate the robot.

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2.1.4 Scientific LearningWe would like to look into the possibility of smaller display cases around the

outside of the robot case that would contain various parts and equipment used in

the robot with explanations as to what they are for. These display cases would

allow people observing the robot to see what types of technologies went into

making the robot and hopefully learn a little about robotics.

2.1.5 Intuitive OperationThis display would not require elaborate instructions before using because you

would learn to operate it by playing with it.

2.1.6 MaterialsThe mechanics of the robot would most likely be comprised of steel and

aluminum components to ensure durability. There would be a multitude of

electronic sensors, circuitry and motors to control the robot. We are looking into

the different methods of creating the motion of the robot including electric,

hydraulic and pneumatic.

2.2 Robotic Squirt Gun and Targets

2.2.1 OverviewThe squirting hand is an idea which incorporates a robotic hand with a squirt gun.

The squirting part would be built into one of the fingers. In the display would be

several targets and other things that kids could shoot water at. One idea was to

put a turbine which they can shoot at and light a light bulb. They could then

experiment with shooting the turbine in different places and seeing which spins it

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faster, lighting the bulb brighter. This idea is also a possibility to combine with

the sensor/glove idea. Basically, I envision a display case with the hand on one

side. The controls will be behind the hand and in front will be a “shooting range”

with whatever targets we would choose.

2.2.2 The "Attractor Factor"The attractor factor of this project lies in the fact that kids can shoot things. All

kids love squirt guns and would find this enjoyable. Adding things like light bulb

to light up would help draw kids to this display.

2.2.3 Method of InteractionThrough controlling the hand, and squirting device, either through joystick or

glove allows the kids to interact with the display.

2.2.4 Scientific LearningThis project includes scientific learning through the turbine, teaching them about

circular motion. Other possibilities are linking an electricity lesson to the light

bulb or a lesson on fluids to the squirting mechanism.

2.2.5 Intuitive OperationThis particular display would require little to no instruction.

2.2.6 MaterialsMaterials would include the robotic hand and whatever controls are associated

with it. We would also have to build the “shooting range” and whatever targets

we desire. The display would have to funnel the water back to some sort of pump

to be reused.

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2.3 Remote Racing and Track

2.3.1 OverviewThe race track idea is pretty much a high-tech racing game. Picture a regular

electric racing game but add some intelligence. Some cars could be computer

controlled allowing from 1-8 players. Players would be penalized for bumping

another car, running into the wall, etc. Built in could be noises, fires, and smoke,

associated with certain occurrences. Here we would have a large oval racetrack.

With eight control stations set up around the circumference, each with its own

wheel and pedals. Brightly painted cars would sit on the track along with other

effects like spectators in bleachers, making it look like a real racetrack.

2.3.2 The "Attractor Factor"The attractor factor is that a big race track would be there, with sounds, smoke,

etc. Kids would see the cool racecars and want to try it out. Controls could be

separate stations with gas and brake pedals and a steering wheel.

2.3.3 Method of InteractionThrough controlling the cars, and being involved with a race, kids would interact

with the display.

2.3.4 Scientific LearningThis project includes a little scientific learning but lots more fun for kids.

2.3.5 Intuitive OperationThis display would require a little instruction in using the remote car controls.

2.3.6 MaterialsMaterials would include the track, the cars and the control devices.

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2.4 Robotic Arm Wrestling

2.4.1 OverviewThe Robotic Arm Wrestling Project will focus on the physical capabilities of

robotics. There will be two robotic arms placed in a display. These arms will be

positioned such that they look like two people arm wrestling. The arms will be

hinged at the bottom, or the elbow, with joints at the wrist and fingers. Each arm

will be controlled by a different operator at opposite ends of the display. In order

to make your arm push down on the opposing arm, the operator must alternate

pushing two buttons as fast as possible. The faster the buttons are pushed, the

harder the operators arm pushes down on the opposing arm.

2.4.2 The "Attractor Factor"Robotic Arm Wrestling would be an extremely attractive display for several

reasons. First, the mere aspect of a robotics display would attract a child.

Robotics is very unique and very enticing for children. Second, arm wrestling is

something that many children do with their friends all the time. After seeing a

display that involves arm wrestling a child would be more likely to come and try

this display. Another reason Robotic Arm Wrestling has the “attractor factor” is

that it involves two operators. A child won’t just be playing this game by

him/herself. Children can actually compete with one another, which is always

attractive to children.

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2.4.3 Method of InteractionChildren will get to physically control the robotic arms in order to generate

movement by pushing down repeatedly on alternating buttons. As they press these

buttons they can see the movement of the arms in a real time atmosphere.

2.4.4 Scientific LearningWe would like to look into the possibility of smaller display cases around the

outside of the robot case that would contain various parts and equipment used in

the robot with explanations as to what they are for. These display cases would

allow people observing the robot to see what types of technologies went into

making the robot and hopefully learn a little about robotics.

2.4.5 Intuitive OperationThe Robotic Arm Wrestling display will require some direction. As with almost

any hands on display, there will need to be a description of what the operator

needs to do in order to accomplish the objective. The ideas of this project are

very simple, which will require minimal direction and supervision. It does not

take much to explain that the operator will need to alternate pressing two buttons

in rapid succession in order to control the arm.

2.4.6 MaterialsThe materials would include metal for arms and fingers, joint systems, electrical

system, and display case and buttons.

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2.5 Remote Soccer Players

2.5.1 OverviewIn this project we will design at least two small robots. Each autonomous robot

will have a remote control, four wheels to drive, and two “tools” to play soccer

with. The first tool is a “leg” which can pass the ball to other team members. The

second tool is an “eye.” Each robot will have an eye and a small light bubble.

When a robot's sensor detects a light, it will stop a while to give a chance to the

other team to get the ball. Each robot would be as small as possible for

maneuvering and have as long a battery life as possible. There will also be a

miniature soccer field and goals at each end to simulate the soccer environment.

2.5.2 The "Attractor Factor"Kids always enjoy remote control cars and this will give them an opportunity to

control robotic soccer-kicking miniature vehicles.

2.5.3 Method of InteractionThe user would press a particular button to kick the ball and would control the

vehicles with a remote control. It might be necessary to have separate stations for

different vehicles similar to the remote racing.

2.5.4 Scientific LearningThe soccer robots will teach children about intelligent robots today that

sometimes will act without human control. This is to let them know that modern

robots can “feel” and that they are not just machines. In the future they will

respond more and more like humans.

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2.5.5 Intuitive OperationThis display would require a little instruction in using the remote car controls.

2.5.6 MaterialsEach robotic vehicle would require a light bubble, light sensors, motors, program

chip, mechanical foot, and a vehicle frame and wheels. The display would require

materials for a goal, playing field, and protective boundary.

2.6 Robotic Basketball Shooter

2.6.1 OverviewThe robotic basketball shooter will mimic the action of the human arm while

throwing a basketball into a basket. The control would be three simple levers

which turn the shoulder, elbow, and wrist of the robotic arm. The challenge is to

properly time how the wrist and elbow move so that the robot will correctly throw

the ball. It would also be possible to change skill levels. The display will involve

an enclosed area in which to throw the basketball and allow it to be retrieved

automatically and replaced in the robotic hand. When the user moves a lever, the

change is immediately translated to a movement in the robotic arm. One possible

alternative is to use an arm like this to throw a smaller ball through a target that

will light up or react when the toss is successful.

2.6.2 The "Attractor Factor"The simple controls and robotic arm will definitely draw spectators. The

basketball theme would also help to draw people when they see the basket.

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2.6.3 Method of InteractionThe control would be three simple levers as mentioned above. The shoulder lever

would be used to line up the shot and the other two would be used to throw the

ball.

2.6.4 Scientific LearningThere are a broad range of opportunities for children to learn how their arm

moves when they throw a ball and how robots can try to reproduce that motion.

2.6.5 Intuitive OperationThis display might require a little explanation but even without any, a child will

quickly learn how it works by playing with the levers and watching the arm move.

2.6.6 MaterialsThe arm itself would include metal and other sturdy construction components to

allow for the stress placed by throwing a ball. Three motors for the joints and

control circuitry for each from the input levers would be necessary along with

additional mechanics to automatically retrieve and place the ball in the robotic

hand. The display would involve a sturdy, transparent barrier for safety, a

basketball backboard and rim, and a control table where the levers would be

mounted.

2.7 Interactive Maneuverable 3-D Maze

2.7.1 OverviewThe Maneuverable Maze is a concept similar to common, smaller versions of a

maze which tilts in all directions to allow a ball to roll through from the starting

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place to the end (sometimes called a "labyrinth"). The maze would be mounted on

a robotics base to allow it to tilt in all directions. The actual maze would be quite

large and the motion control system would be a small version of the maze

mounted on a similar support structure. When someone moves the miniature maze

controller, the large maze would copy that motion and the ball would move

around inside the maze. It would be possible to include different obstacles and

interaction within the maze to increase or decrease the challenge of finishing the

puzzle. The control device would be located on an elevated platform to allow easy

viewing of the large maze below which would be surrounded by a protective

display case. There could also be the addition of moveable "doors" or obstructions

inside the maze that would be controlled by the user to increase their interaction

with the maze.

2.7.2 The "Attractor Factor"The large maze would certainly attract attention and the opportunity to turn and

tilt such a large maze with a smaller version would help to hold their attention.

This project also has the benefit of allowing modification to the average patron

"dwell time" by changing the difficulty.

2.7.3 Method of InteractionThe controller would be a moveable smaller version of the larger maze on a

robotic/hydraulic pedestal. The large maze would immediately copy how the user

changes the position of the controller.

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2.7.4 Scientific LearningThe maze is more of a fun puzzle-solving experience which utilizes robotics than

a learning experience. A basic understanding of gravity is certainly necessary to

predict how the ball will roll through the maze, but the emphasis here is mostly on

fun and challenging interaction with the robotics.

2.7.5 Intuitive OperationThis display would require very little explanation to tell users to move the small

maze and watch the large one move the same way.

2.7.6 MaterialsAn elevated platform, display case, control device/pedestal, robotic support

equipment for both the control device and large maze, control electronics, the

large maze made of metal/plastic/wood, and the ball.

2.8 Conclusion

All of the project proposals were presented to the Rochester Museum and Science Center

to obtain their feedback on what they saw as the best fit for their facility. After multiple

meetings with Museum staff the projects were narrowed down to three, the basketball

shooter, the interactive maze and the robotic arm and dexterous hand. In the end the

robotic arm and dexterous hand was selected because it was the best example of robotics

and the most interactive for museum patrons.

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Fig 3-1: Basic Flex Sensor and Circuit

3.0 Concept Development

The concept development for the project considered the areas of control mechanism, the

orientation and operation of the robotic arm, the mechanical power source to move the arm,

and the electrical system controlling the movement.

3.1 Controls

3.1.1 Sensor Laced Glove & Fighter Style Joystick

One concept for controlling the arm and hand is to utilize a glove laced with flex

sensors on one hand and operating a fighter style joystick with the other hand.

The glove would have seven flex sensors embedded in it to sense the position of

the operator’s fingers, thumb and wrist. The sensors work by changing their

resistance the more they are bent. This change in resistance could be calibrated to

represent the position of the finger.

Courtesy of http://devices.sapp.org/component/flex/

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http://devices.sapp.org/component/flex/


Fig 3-2: Possible Joystick with Push Buttons for Additional Control

The data obtained from the glove would be used to control the fingers and wrist

so the robot would in a sense mimic the operator’s movement. The joystick

would be used to control the other parameters of the arm. Most likely moving the

joystick left and right would control the swivel and moving it forward and

backward would control the elbow joint. The cylinder would be controlled by the

trigger and thumb buttons on the joystick.

Courtesy of Radio Shack

3.1.2 Sensor Glove with Motion Track

This concept would utilize a similar glove as concept 3.2.1 but the glove’s motion

would also be used to control the rest of the arm. Basically the robotic arm would

mimic all the operator’s movements. Initially this was our ideal way of

controlling the robot but we didn’t think it was feasible for our budget and

resources. That was of course until we found a glove on the market that we could

purchase to accomplish this. The glove is called P5 and is made by Essential

Reality.

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Courtesy of Essential Reality

This glove was designed for gaming and features flex sensors in the fingers and

an infrared receptor that senses the movement of the glove. The device plugs into

a USB port and has software to assist in programming it for your application.

Best of all we were able to find an online retailer selling them for approximately

$30 with shipping and handling. If we are unable to program this glove to control

all the movements of the robot we will at least be able to use it for our glove to

sense the finger motion.

3.2 Arm Types

3.2.1 Wrist, Elbow, & Shoulder Joints

Our first concept for the robotic arm was made up of the major joints in the

human arm. There would be a shoulder joint that would have three degrees of

freedom in the x and y directions and a rotation. Further down would be the

elbow joint that would have one degree of freedom and then the wrist joint with

two degrees of freedom to move up and down as well as rotate. This design

would give us motion that is most like the human arm but the problem is that

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there are too many degrees of freedom to control with our controller designs. We

believed that trying to incorporate all these degrees of freedom would make the

robot to difficult to operate for the target age group.

3.2.2 Wrist, Elbow & Rotating Cylinder Joints

Our second design basically eliminated the shoulder joint except for the rotation

part. This design utilizes a pneumatic or electric cylinder to give the arm reach.

The cylinder would be mounted so that it could be rotated enabling the arm to

reach a circular area. At the end of the cylinder would be the elbow joint that

would be able to move up and down like a human elbow. At this elbow joint we

are also looking into the possibility of adding a rotation to increase the agility of

the arm and hand. It is our belief that by moving this rotating joint from the wrist

up to the elbow would reduce the problem of twisting wires and cables that run

from the forearm to the hand. The wrist joint would be able to move up and down

only.

3.3 Source of Mechanical Power

3.3.1 Pneumatics

Air muscles produced by the Shadow Robot Company could be utilized to power

the fingers and various joints in the arm. One of the great benefits of air muscles

is they have a power-to-weight ratio as high as 400:1 where electric motors only

go as high as about 16:1. The air muscles can apply a force of up to 140 lbs each

and are flexible enough to be bent around corners or twisted axially. The general

25


Fig 3-4: An Air Muscle showing how it increases length with applied pressure

make-up of an air muscle is a rubber bladder covered by plastic woven sheath as

shown below.

Photo courtesy of Shadow Robot Company

The normal operating pressure of the air muscles is 0-60 psi. The air muscles

would flex and bulge similar to the human muscle creating a more life like robot.

In addition to the air muscles one of our concepts involves a pneumatic cylinder

for the bicep area of the arm that would allow the arms reach to be increased or

decreased as desired. A pneumatic system such as this will incorporate various

regulators, manifolds and valves to control the flow to the components. The team

was concerned with the noise issues associated with utilizing an air compressor if

we would have to enclose it within our display. We have however worked it out

with the museum to have them supply an air compressor located away from the

display and have the air supply piped to the display.

3.3.2 Electric Motors

Controlling the joints by electric motors is another option our group has

investigated. There are two main types of motors that could be employed in our

project. The first are stepper motors. Stepper motors can be controlled by turning

coils on and off; therefore they are easy to control using digital computers. The

computer simply energizes the coils in a certain pattern and the motor will move

26


accordingly. An encoder could be attached to the motor to verify its position.

The second type of motor is servos. Servo motors are widely used in RC

applications like cars and planes. They are a very good match for a robotics

project like ours because they are available in a large range of torques and they

are relatively small. Inside the small case is a system consisting of a motor,

gearbox, feedback device, servo control circuitry, and drive circuit. These motors

are extremely easy to control with a digital controller and require about 5-6 volts

and draw 100-500ma depending on size.

3.3.3 Hybrid System

The third and probably most likely system is a hybrid or mix of pneumatic and

electric devices. It is our belief that the air muscles are the best method for

actuating the fingers and the wrist joint but the elbow flex and shoulder rotation

would be best controlled using servo motors because of their more precise control

and positioning. The cylinder could be either pneumatic or electric, at the present

time the team is leaning towards electric simply because it would be easier to

control the amount of advancement with a worm drive type cylinder for instance.

Another reason to use an electric cylinder over a pneumatic one is the amount of

air supply needed would be much less since the cylinder would run around 100

psi. Further research must be done into the availability and cost of an electric

cylinder before a definite decision is made.

27


3.4 Electronic Data and Control System

The electrical control system to be used for this project presented several

possibilities which were based on both the controller data input and input and

output lines to and from the robotic arm. The possible components were a

personal computer (PC) and a microcontroller development board.

3.4.1 PC with an output board

The option to use a PC without a microcontroller simplifies the design and the

programming necessary. However, this option would require that the PC drive the

many input and output lines needed to control the robot. The number of control

lines would be between twenty and forty, depending on design decisions such as

which kind of valves are used and whether air muscles are used at the elbow joint

instead of a servo. For this option there is the issue of sending these lines over

long distances and the potential communications trouble that could result.

3.4.2 Microcontroller Development Board Alone

The microcontroller development board (MDB) without a PC would certainly

consolidate the electrical design to one device and lower the necessary budget.

The issue that arises with this approach is that the USB drivers necessary to read

the signals from the glove controller would need to be written specifically for the

selected microcontroller. This would be a lengthy software undertaking and

would require that much of the work and testing of the drivers be redone when the

drivers are already written and tested for a PC with the Windows OS.

28


PCUSB RS-232

Micro-controller


3.4.3 PC with a Microcontroller Development Board

The use of a PC in the design will not be the least expensive method of

implementation but it would solve problems with device drivers, required inputs

and outputs to the robotic arm, and lengthy communication lines. The PC in this

situation would receive the USB signals from the glove controller and a program

running on the PC would convert these to an RS-232 serial output from the PC.

An RS-232 cable would then take this serial data to the microcontroller which

would be located close to the robotic arm. The microcontroller would then

convert the serial input to a set of output signals on the many output lines.

29


4.0 FeasibilityFeasibility assessments were conducted to help the team in their selection of the

project, controllers, and arm types. We utilized a weighted measurement system

to ensure that our key objectives would be met properly.

4.1 Project Feasibility

We used a feasibility chart to prove that the dexterous hand was the right selection

for our project. In the chart below the Dexterous hand is set as the baseline

project and then the remaining 6 projects are scored on a scale of 1 to 5 on wether

they are better or worse than the dexterous hand. The chart show that the hand is

the best choice at 100% followed by the labyrinth at 89.3%.

Dexterous Hand Is the Baseline Project 1 = much worse than

baseline concept 2 = worse than baseline 3 = same as baseline 4 =

better than baseline 5= much better than baseline D

exte

rous

Han

dD

exte

rous

Han

d

Laby

rinth

Laby

rinth

Bas

ketb

all S

hoot

erB

aske

tbal

l Sho

oter

Arm

Wre

stlin

gA

rm W

rest

ling

Rob

otic

Soc

cer

Rob

otic

Soc

cer

Rob

otic

Squ

irter

Rob

otic

Squ

irter

Rac

e Tr

ack

Rac

e Tr

ack

Rel

ativ

e W

eigh

tR

elat

ive

Wei

ght

Sufficient Student Skills?Sufficient Student Skills? 3.0 3 2 3 2 3 3 21%

Sufficient Financial Resources?Sufficient Financial Resources? 3.0 3 2 3 3 3 3 14%

Sufficient Time to Complete?Sufficient Time to Complete? 3.0 4 1 2 3 3 2 14%

Cost of Materials?Cost of Materials? 3.0 4 2 3 3 2 2 7%

Has "Attractor Factor"Has "Attractor Factor" 3.0 1 4 3 2 2 2 24%

Interactive For Guests?Interactive For Guests? 3.0 2 3 2 3 3 3 10%

Does Not Require Much Instruction?Does Not Require Much Instruction? 3.0 4 2 2 1 3 2 7%

Promotes Scientific Learning?Promotes Scientific Learning? 3.0 2 2 1 1 1 1 3%

Weighted ScoreWeighted Score 3.0 2.7 2.4 2.6 2.3 2.6 2.4

Normalized ScoreNormalized Score 100.0% 89.3% 82.1% 89.3% 79.8% 89.3% 82.1%

30


4.2 Controller Feasibility

The following chart shows the feasibility results for the different controller

options. This chart proves that using the glove for all the control is the best

option.

Glove and Joystick is the Baseline Option 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better than baseline G

love

and

Glo

ve a

nd

Joys

tick

Joys

tick

Glo

ve A

lone

Glo

ve A

lone

Rel

ativ

e W

eigh

tR

elat

ive

Wei

ght

Sufficient Student Skills?Sufficient Student Skills? 3.0 2 21%

Sufficient Financial Resources?Sufficient Financial Resources? 3.0 5 14%

Sufficient Time to Complete?Sufficient Time to Complete? 3.0 3 14%

Cost of Materials?Cost of Materials? 3.0 5 7%

Has "Attractor Factor"Has "Attractor Factor" 3.0 4 24%

Interactive For Guests?Interactive For Guests? 3.0 3 10%

Does Not Require Much Instruction?Does Not Require Much Instruction? 3.0 4 7%

Promotes Scientific Learning?Promotes Scientific Learning? 3.0 4 3%

Weighted ScoreWeighted Score 3.0 3.6

Normalized ScoreNormalized Score 84.5% 100.0%

31


4.3 Arm Feasibility

The arm concepts were placed into the feasibility chart and as shown below the

wrist, elbow and rotating cylinder concept is the best design.

Wrist, Elbow & Rotating Cylinder is the Baseline 1 = much worse than baseline concept 2 = worse than

baseline 3 = same as baseline 4 = better than baseline 5= much better than baseline

Wris

t Elb

ow &

Rot

atin

gW

rist E

lbow

& R

otat

ing

Cyl

inde

rC

ylin

der

Wris

t Elb

ow &

Sho

ulde

rW

rist E

lbow

& S

houl

der

Rel

ativ

e W

eigh

tR

elat

ive

Wei

ght

Sufficient Team Skills?Sufficient Team Skills? 3.0 2 21%

Sufficient Financial Resources?Sufficient Financial Resources? 3.0 2 14%

Sufficient Time to Complete?Sufficient Time to Complete? 3.0 2 14%

Cost of Materials?Cost of Materials? 3.0 1 7%

Has "Attractor Factor"Has "Attractor Factor" 3.0 3 24%

Interactive For Guests?Interactive For Guests? 3.0 3 10%

Does Not Require Much Instruction?Does Not Require Much Instruction? 3.0 3 7%

Promotes Scientific Learning?Promotes Scientific Learning? 3.0 2 3%

Weighted ScoreWeighted Score 3.0 2.3

Normalized ScoreNormalized Score 100.0% 78.2%

32


4.4 Electronic Control Feasibility

The electronic system can involve either a Microcontroller with a PC, or a PC with an output board, or a Microcontroller only. The aspects of choosing each are shown in the feasibility assessment below. The team is in favor of the Microcontroller with PC because of the existing USB drivers and better communication properties. The major drawback is the cost and complexity of design but the savings is in software development time.

14%133.0Replaceable Parts?

83.3%

2.5

4

421411

Microcontroller

Microcontroller

AloneAlone

76.6%100.0%Normalized ScoreNormalized Score

2.33.0Weighted ScoreWeighted Score

3%23.0Processing Speed?Processing Speed?

7%33.0Easy to Maintain?Easy to Maintain?10%13.0Reliable Communication?Reliable Communication?24%33.0Complexity in Programming?Complexity in Programming?7%23.0Cost of Materials?Cost of Materials?

14%33.0Suffi cient Time to Complete?Suffi cient Time to Complete?21%33.0Suffi cient Team Skills?Suffi cient Team Skills?

Relative Weight

Relative Weight

PC with Output PC with Output

boardboard

Microcontroller

Microcontroller

and PCand PC

PC and output board is the Baseline 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline

5= much better than baseline

14%133.0Replaceable Parts?

83.3%

2.5

4

421411

Microcontroller

Microcontroller

AloneAlone

76.6%100.0%Normalized ScoreNormalized Score

2.33.0Weighted ScoreWeighted Score

3%23.0Processing Speed?Processing Speed?

7%33.0Easy to Maintain?Easy to Maintain?10%13.0Reliable Communication?Reliable Communication?24%33.0Complexity in Programming?Complexity in Programming?7%23.0Cost of Materials?Cost of Materials?

14%33.0Suffi cient Time to Complete?Suffi cient Time to Complete?21%33.0Suffi cient Team Skills?Suffi cient Team Skills?

Relative Weight

Relative Weight

PC with Output PC with Output

boardboard

Microcontroller

Microcontroller

and PCand PC

PC and output board is the Baseline 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline

5= much better than baseline

33


5.0 OBJECTIVES & SPECIFICATIONS

A set a guidelines, design objectives, and performance specifications was

established to assist the team in properly assessing on how successful the outcome of the

project is. The following sections of the chapter will go through the different objectives,

specifications, and guidelines that the team agreed upon.

5.2 Design Objectives

There are a number of design objectives that required the attention of the team.

These objectives have to be specified in order for the team to have a list of goals and aims

to achieve. These objectives are listed below:

1. Provide a robotics display with a strong “attractor factor.”

2. Provide a display that will stimulate a child’s interest in learning about robotics and

engineering.

3. Produce aforementioned display at a cost less than $5,000.

4. Enhance the learning experience at the RMSC for all that visit the facilities.

5. Design a robot that can perform tasks that the normal human being may not be able to

do (palm a basketball).

5.2 Performance Specifications

It is inevitable that as the project continues, the team will face numerous obstacles

and problems. However due to time constraints, not every issue will be addressed. By

having a list of performance specifications, it will aid the team in prioritizing what is

crucial. This will help manage time more wisely into what problems must be fixed and

which obstacles the team can overlook.

34


1) Robotic Display Shall be intuitive and require little to no instruction prior to operation.

2) Robotic Display Shall be easily maintained and repaired.

3) Robotic Display Shall have a strong “attractor factor,” drawing children to want to

come play with it.

4) Robotic Display Shall rest on a table which is 28” in height.

5) Robotic Display Shall fit through a 4’ door opening.

6) Robotic Display Shall be moveable by two people.

5.3 Design Practices

To help the team achieve the objectives and specifications that was established, a

list of design practices were kept in mind when team members were developing designs.

A list of these practices is as follows:

1. Design for Manufacturability and Minimum Cost – When possible, we tried to

purchase parts off the shelf for this project. While designing the custom components of

the robot we took care to design it so that it can be most easily manufactured. We did

this by simplifying our design as much as possible and calling for standard sizes and

materials whenever we could. We kept tolerances as loose as possible and made custom

parts easily machinable.

2. Design for Assembly - We produced this display so that each component can be built

separately. That way each of us can focus on a separate part, making the group more

efficient. However, when the parts are brought together they can be easily assembled.

3. Design for Optimum Alignment

35


5.4 Safety Issues

To ensure the safety of all members on the team, a set of safety precautions were

established. Since the testing of the design will undergo high pressures and components

will be spinning at high speeds, it is imperative that the members of the team follow these

guidelines.

1) Since this display will be targeting a young audience we designed it to be enclosed,

thus eliminating most safety issues.

2) All proper precautions will be made in order to safely run air and electricity through

the system.

3) Health concerns from the repeated use of a glove were the only other issue that arose.

We chose an open glove which eliminated this problem.

6.0 DESIGN ANALYSIS & SYNTHESIS

6.1 Display Analysis & Synthesis

The Display unit for the Robotic Arm is designed according to RMSC

specifications. The base of the unit is 28” above the ground, which makes the display

low enough for children and the handicapped. It has been built out of steel and painted

aluminum color. We planned most of our calculations around that specification. It also

fits through a 4ft door opening so that it can be easily transported to the museum. The

display is approximately 6ft tall in order to achieve our goal of having a robotic arm that

36


is twice the size of a human arm. The sides of the display will be of a glass/plastic nature

and will be taken care of by the RSMC display builders. They will be made from a

material that will not break or shatter on impact. The display will be used by many

children and will have a design such that it cannot be broken easily.

37


6.2 Hand Design Analysis and Synthesis

The hand is designed to be twice the size of a human hand and is made out of

Aluminum. The hand has several different components, which include a palm, 5 fingers

(four fingers with three “bones” and one thumb with two “bones,” and a wrist joint).

Each portion of the hand is connected together using pins purchased from McMaster-

Carr. These pins allow for free motion of the joints, which mimics human movement.

The four main fingers are comprised of three different sections each of equation

dimension. The dimensions of each section are approximately 2” x .75” x .5”. The

thumb will have the same dimensions but is only sectioned into two “bones.” The

maximum pressure allowed on each finger is limited to approximately 15lb (Fmax=15lb).

Using simple moment equations such as M=Fd we found the maximum moment in the

fingers to equal 75lb-in. This moment can be found at the base of the fingers where they

connect to the palm.

38


While this is a maximum moment, it is not large enough to cause fracture in the

connecting pin. The pins used have a Shear Strength of 5,400 lbs/in. We are not worried

about the aluminum fingers fracturing due to their size and the minimal loads applied.

The palm is also made using aluminum. It is designed to have the same hinged

joints with pins to connect each of the fingers. It also has a joint on the opposite end of

the fingers to act as an elbow. The palm is hollow to allow for a smooth passageway for

the strings or wires that will control the movement of the fingers. The strings stretch

from the forearm to the palm through holes drilled into the back of the palm. The string

then goes through the finders by small holes cut into the joints. This string then pulls on

the finger in order to bend each joint.

The hinge on the back of the palm for the wrist movement has been analyzed for

several different joint movements. In order to perform calculations on this joint we first

needed to find the weight that it would support. This joint will support 10lb at most.

This weight includes the weight of the aluminum hand plus the object that the hand is

lifting. The lifting action of the hand will create a moment at the wrist. The maximum

calculated moment at this joint was found to be 50lb-in which can be seen when it is at a

90 degree angle with the vertical axis. Again, this moment will not cause a large enough

stress to create a fracture in the joint and/or pin. The hand is shown below. Each

individual portion of the finger is also displayed.

39


Palm Finger Tip

Finger Joint

40


6.3 Forearm Design Analysis and Synthesis

The forearm is a very simple design. It is a galvanized steel pipe that was

purchased from Home Depot. It is 1.5” in diameter and approximately 15” in length.

The pipe is great for our design because it allowed us to drill holes in it to attach the

upper arm cylinder, the palm, and several eyehooks for the air muscle attachments.

Again, this portion of the assembly will not fail because of the strength of the

galvanized steel. Steel is used in many applications and can bear an extremely high load.

The stress that can be expected on the forearm is approximately 6 psi while the yield of

the steel is 50-75 ksi. Clearly, this will not incur any failure.

6.4 Upper Arm Design Analysis and Synthesis

The upper arm is an electric cylinder purchased from ebay. It was originally a

product from IDC Motion. The base is approximately 20” in length and has a cylinder

that protrudes an additional 18” upon activation.

The upper arm is connected to the top of the display using a mounting bracket and

a Lazy Suzan. This allows the cylinder to rotate about the vertical axis, much like the

human shoulder joint. This is the only movement of the cylinder besides the actual in/out

movement of the rod inside the cylinder. The cylinder is forced to rotate by user inputs

that control a motor. The motor turn a belt that drives the Lazy Suzan to turn.

41


Material Design.

Our project consists of many different materials. For our machined parts we chose aluminum for

its ease of machining and relatively low cost in comparison to other options such as composite.

As an issue of cost, we also machined a steel tube to make the forearm. For strength we chose

steel for our display case. We also used wood in some of the parts we manufactured. The

display contains a 2 X 4 as a mounting bracket and plywood as the base of the display.

Everything is to be painted for aesthetic purposes prior to the display being put on the museum

floor.

Parts.

Our project consists of many different parts, both purchased and machined. On the purchased

side are air muscles which came from a specialty company in London called the Shadow Robot

42

Robotic Arm & Dexterous Hand Senior Design 05911 04013Company, Valves, regulators and other pneumatic accessories came from a local company called

Numatics, we purchased an electric cylinder with a 19.5 in (495 mm) stroke made by IDC

Motion which was used, saving us substantially on cost, two servo motors which were purchased

as used parts, and an aluminum turntable, or “Lazy Susan Bearing” which came from McMaster-

Carr. We also purchased torsional springs, pins, and clevis joints from McMaster - Carr. The

necessary steel and aluminum came from a place in Rochester called the Steel Supermarket on

Mt. Read Blvd.

As far as machining is concerned, we machined the hand, fingers, forearm, top plate, frame, and

several other specialty parts. The hand was machined from a solid block of aluminum using the

CNC lathes on RIT. We then had to drill many holes into it, fit a clevis-type joint to it and put a

Plexiglas cover on the bottom. The fingers were machined from bar stock and milling and

drilling were required to form them how we needed. We also had to fit torsional springs between

the joints to cause the finger to return to its original position after being bent. Homemade joints

hold the fingers to the hand and all joints are pinned together to allow them to curl smoothly.

The forearm is made from a piece of steel tubing; we machined joints into the end so that they

could be pinned on both sides. We also had to mill a clearance gap in the upper side to allow

rotation of the elbow joint. Furthermore, the tube has holes drilled and threaded rods inserting to

allow us to mount the air muscles. The tube is attached on the upper end by a clevis joint which

screws on to the electric cylinder. The clevis joint is also machined. We built a pulley into it

and also drilled a hole into it to allow function of the air muscles.

Next is the electric cylinder. First of all, the cylinder contains a mount for the motor which we

machined. This was necessary because we replaced the stepper motor it came with with a servo

43

Robotic Arm & Dexterous Hand Senior Design 05911 04013motor which we purchased. The cylinder is held in place by an aluminum plate we machined.

The plate has holes drilled into it and screws go straight down into the electric cylinder, holding

it in place.

The plate is drilled into a “Lazy Susan Bearing” which is mounted on top of 2 X 4’s, which are

in turn mounted to the display case. On top of our mounting plate we secured a timing pulley

which works in conjunction with a servo motor. The servo motor hangs upside down from the

display by a custom mount which we machined ourselves.

Operation.

There are many aspects to the mechanical operation of this project. The entire arm assembly has

the ability to rotate. This is achieved by a servo motor, which is mounted to the top of the

display case. The motor turns a timing belt, which is attached to the mounting plate, which is

attached to the “Lazy Susan Bearing.” By turning the motor we can rotate the electric cylinder

and therefore, the entire system. We have allowed for the arm to rotate 180 degrees. This allows

access everything in the display, without making the display so big that it cannot fit through the

museum doors.

For extension of the arm, the electric cylinder contains it’s own motor. That motor turns a worm

gear within the cylinder and causes it to extend. This particular cylinder allows for 19.5 in (495

mm) of extension. In our display case, this allows the hand to reach to the floor when the hand

and forearm are parallel to the floor of the display.

All joints (fingers, wrist and elbow) are controlled by either one or two air muscles. The muscles

are pneumatic and linked to our valves, flow controls, regulator, filter etc. One valve controls

each finger joint, with the exception of the middle and ring finger. The middle and ring finger

44

Robotic Arm & Dexterous Hand Senior Design 05911 04013are controlled by a single valve and thus, their motion will be tied together. This was a

precaution made so that kids at the museum will not be able to use the hand to give the middle

finger. The wrist has an air muscle on both the top and bottom, both of which are supplied by

the same valve. This is a different valve, however and as one side charges, the other discharges,

allowing the wrist to flex in both directions.

We have two sizes of air muscles, the small, which produces 6 lb (27N) of force and the large,

which produce 40 lb (178N) of force. The air muscles are attached to the forearm. One side of

the muscle is tied off and cannot move. A string runs from the other end of the muscle to what it

moves. So the small muscles run through the finger to the fingertips and the large muscles run to

a place just below or above either the wrist or elbow joint. The muscles’ natural positions are in

tension, however, when they are inflated with 60 psi (4 atm) of pressure, they contract, working

much like “finger handcuffs.” The pressure causes the muscles to contract, pulling the string on

the non-stationary end. That string then pulls the fingers or other joints and causes them to bend.

By pulsating the valves, you can precisely control the position of the fingers, elbow or wrist.

The returning force is provided by torsional springs in the fingers, a second air muscle in the

wrist and merely by gravity in the elbow.

The entire mechanical system is linked to the electrical system through a microcontroller and a

PC.

Lifespan.

The pneumatic valves are the only component that provided a tested lifespan. The Numatics

Incorporated rates the valves we purchased for 200 million cycles. The museum gave us data

that the museum operates 8 hours a day 363 days a year. In the tables section of this picture is a

45

Robotic Arm & Dexterous Hand Senior Design 05911 04013chart showing the projected lifespan of the valves for various cycles per minute assuming display

will be under constant use for the full 8 hours a day. We are estimating the average use to be 70

cycles per minute which would equate to a lifespan of 16.4 years.

Valve Lifespan

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0 50 100 150 200 250

Cycles Per Minute

Year

s

Figure 7: Lifespan of Air Muscles [4]

Stresses.

We designed our entire assembly so that there would not be any structural failure due to

stresses. However, stresses are still a consideration in any design project. The area of most

concern in the arm assembly is the elbow joint. This is the joint that will encounter the most

stress because it will be supporting approximately 15 lbs of material. One portion of the joint

that could encounter relatively high stress concentrations is the clevis joint and the connector pin.

The connector pin and the clevis joint each have a shear strength of 5,400 lbs (McMaster-Carr).

There can be a calculation for the axial stress that will be felt by the pneumatic cylinder.

With the cylinder bearing a maximum force of 15 lbs with an area of 1.327 square inches we can

calculate the axial stress. This stress is equivalent to the force divided by the area. The axial

stress on the cylinder is found to be 11.3 psi. The Ultimate Tensile Strength of this steel cylinder

is 74.5 ksi. Clearly, this cylinder will not fail under axial loading.

46


The forearm can also have a stress calculation completed on it. The shear stress on the

forearm can be found using the following formula:

Using this formula we calculate the stress to be 5.97 psi. Given the Yield Strength for the

galvanized steel pipe, 50ksi, we get a factor of safety much greater than one.

The stress throughout the assembly will never exceed the maximum allowable stresses

for the materials given. After many calculations we can see that our assembly will not fail as a

result of stress failure.

6.5 Equations Used for Mechanical Design Analysis and Synthesis

6.6 Electrical Control

The electrical control consists of three main parts, the personal computer, the

microcontroller, and the output power circuit.

Design Overview. The electrical design problem consisted of designing an

interface that detects the movements of the human hand and translates them into control

47


signals for the robotic arm. The user input device was chosen for its apparent usefulness

for our project, for its ease of replacement, and for its low cost. It was decided early on

that there might be a need for many input and output signals because of the many

mechanical devices that needed to be connected. This led to a possible design including a

microcontroller with many input/output pins or a special input/output card attached to a

personal computer. The end design decision to allow for the greatest flexibility includes

both a personal computer and a microcontroller. The microcontroller does not supply the

necessary voltages and currents to drive the mechanical and pneumatic devices so a

complex circuit design was implemented involving power supplies, relays, and

transistors.

User Input. In order to best accomplish a feasible solution in terms of time and

money, the input device was purchased commercially. The P5 Glove Controller includes

five bend sensors, one per finger, mounted on a sturdy plastic frame. Each sensor

provides a 0.5 degree resolution independent finger measurement. In addition to the

unique finger bend measurements, the glove provides detailed position tracking of six

different positional axes through the use of a remote infrared sensor. The glove worn on

the right hand of the user has eight infrared lights on its plastic shell. The infrared sensor

tracks six axes which include x, y, z, yaw, pitch, and roll.

Personal Computer Software Design

The PC design included the use of the drivers and free software development kit supplied

by the manufacturer of the P5 glove. The software also included the use of serial

communication via an RS-232 serial link with the microcontroller. The data coming from

48


X motionY motionZ motionPitch

Rotation of the entire armMotion of the elbowMotion of the cylinder (up/down)Motion of the wristMotion of the corresponding robotic fingers

Finger bend

Glove Input

Output Control

the P5 glove was made available through the provided functions of the software

development kit and then converted into 8-bit bytes for transmission over the serial link.

Figure 2: Simple Diagram of the PC software

The P5 data was in terms of absolute position with respect to the glove’s starting

position and thus was not useful in terms of absolute positional control. The output data

would wander and never return to a reference location. Thus the decision was made to

simply use the change in position (velocity) to control the robotic arm. When a certain

threshold voltage is reached, the program responds by enabling the motion of the

corresponding robotic arm component. The arm components with their corresponding

control signals from the glove are given in Table 2.1.

Initialize P5

Set up Serial Comm

Get current glove data

Convert Data to Byte MessagesTransmit Data via Serial Link

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Thumb Finger Contract/ReleaseIndex Finger Contract/ReleaseMiddle OR Ring Finger Contract/ReleasePinky Finger Contract/ReleaseMove Wrist UpMove Wrist DownMove Elbow UpMove Elbow DownRotate Arm RightRotate Arm Left

Extend Arm Down (Cylinder Actuator)

Extend Arm Up (Cylinder Actuator)

P4.1

P4.0

P4.2P4.3P4.4P4.5P4.6P4.7P5.0P5.1P5.2P5.3

OutputPort

Robotic Arm and Hand Action

Microcontroller Design.

The function of the microcontroller is primarily to take the serial data in and to send

the digital output signals to the individual control lines for each robotic component. The

output control lines are given in Table 2.2.

Table 2: Microcontroller Outputs

The microcontroller operates at 3.3 digital high voltage and has a limit of 25 mA

on the outputs of the ports. The microcontroller chosen for the design is the C8051F020

which contains multiple analog to digital converters, 64KB of programmable FLASH

memory, 2 UART serial interfaces, five general purpose 16-bit timers, and a

programmable counter/timer array.

The serial communication is performed via the UART0 with a set baud rate at both

the PC and the 8051 of 4800 bps. This baud rate is slow compared to the capability of the

system but there is no need for higher resolution because of the high frequency filtering

of the input signals in the PC software.

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Circuit DesignFirst we use a 3V power supply and NPN Bipolar Junction Transistor to amplify

the signal output from the microcontroller. For the amplifier we chose the 2N3904 shown below in Figure 3.

Figure 3: BJT used for Output Current [2]

The 2N3904 has:

IC=200 mA IC = 0.1 mA, VCE = 1.0 V

Each output will control one relay.

Figure 4: Low signal relays G6K-2P-Y [3]

All relays will get the amplified signal from the microcontroller. Relays will

perform a simple on and off function to supply 24V power.

We chose Omron’s S8TS 24V power supply pictured in Figure 5.

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Figure 5: Project Power Supply [3]

One power supply will only connect to the cylinder motor which allows the hand

to elevate up and down. The motor is 24V 1 Amp so that the reason for having one power

supply for this motor is that this DC motor has a very high start up current. When the

motor is on the power supply will drop so a large amount of current is drawn and the

voltage drops down. After a short interval of approximately a tenth of a second, the motor

will return to the desired operational current draw 0.98 Amp.

The additional power supply will serve all the other power on the board.

Considering the high start current through the cylinder motor, the power supply

will be hot. We added a fan on the side of the power supply. The fan is 12V 0.08Amp.

The LED is the output from the relays output(24V) which is for simulation and

program debugging.

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Figure 6: Simple Circuit Block Diagram

6.6.1 Electrical Input and Output

The input to the PC is the P5 Glove controller. It sends data via its USB cable.

The PC output is the RS-232 serial link which is attached to the PC’s com port. The

control inputs and outputs from the robotic arm and hand go to output-configured ports of

the microcontroller. The input-configured ports receive the limiting sensors for the

extension cylinder, arm rotation, and floor pressure.

6.6.2 Electrical Control Algorithm

The control algorithm is quite simple and depends only on the motion and not

position of the glove controller. When the glove controller is moved, the robotic arm will

also move. The position of the arm will be adjusted by the person who is controlling the

arm.

The arm moves its individual components based on these signals from the glove:‘x’ Axis controls rotional motor‘y’ Axis controls elbow motion

Microcontroller output (3.3V 25mA)

BJT 2N3904 offer more current

Low signal relays G6K-2P-Y

Power supply

Motors and air muscles

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‘z’ Axis controls extension cylinder‘pitch’ Axis controls the wrist motion

Finger Motion Control:Motion control theory for the fingers is same as for the armEach robotic finger is controlled by each finger sensor on the glove

6.6.3 PC Program in C++

The C++ program written for the PC performs 3 continuous operations. It reads

the new user input data from the glove, filters and translates it into output serial

communication bytes, and sends it out to the serial port.

Initialize the P5 Glove Initialize the Serial Port Begin Main Loop Update Glove Variables with current data Filter Incoming Data to detect motion above a certain threshold Convert Filtered Data to an 8-bit serial output Send output byte to the serial port Loop (forever)

6.6.4 Microcontroller Program for 8051 MCU

The assembly language program written for the 8051 performs 3 continuous

operations. The main loop polls the serial port flags to see if new data has arrived. When

a new byte arrives the first 3 bits are processed to determine which motion should be

acted upon. The input from the limiting sensors is checked to make sure this motion is

allowed and then the corresponding port pins for this motion device are updated.

Setup the UART for serial transmission Setup the port pins for sensor inputs and signal outputs Begin Main Loop Look at the most recent incoming serial data Check the first 3 bits for motion ID Check the last 2 bits for desired motion If the sensor feedback allows this motion, execute this motion and send output to port Loop forever

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7.0 DELIVERABLES

The important deliverable is a functional display to be delivered to the RMSC, but

there are a few additional deliverables due to the nature of the project and the

requirements of the RIT Senior Design class. These deliverables are to be turned in to

the RMSC and thus do include the deliverables for RIT Senior Design.

7.1 The Robotic Arm and Hand Display

The functional display deliverables include the P5 Glove, the personal computer

with functioning glove code, the USB connection to the 8051 microcontroller, the fully

programmed 8051 microcontroller with port connections to power transfer circuit, the

power transfer circuitry connected to the motors and valves, the display case with the

mounted arm and hand.

7.2 The Robotic Arm and Hand User’s Guide

The user’s guide for this project is necessary because the project will be delivered

to the RMSC upon completion of Senior Design by the project team members. The user’s

guide will include information concerning the normal operation of the mechanical and

electrical components. It will also provide a resource for maintenance and

troubleshooting, should the arm cease to function normally.

7.3 The Complete Parts List with Vendors

The parts list will include all the parts used in this project and will provide

replacement parts for each with the vendor name and price.

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8.0 PROJECT TIMELINE

The following is the timeline for our Senior Design Project. There was a need to

have additional time for design which is shown during the first part of the Winter

Quarter because of the few short weeks available before PDR that the team had

for design. The team was not able to test the project at the RMSC until after CDR

due to the scope and difficulty of the project.

Senior Design Fall Quarter:

Senior Design Winter Quarter:

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9.0 PROJECT BUDGET

The estimated cost on some items corresponds to the actual component price from

a known vendor. However other items either need to be chosen for the design, or

a vendor may still need to be chosen. Further design analysis needs to be done on

items such as the microcontroller and valve type and the budget will change if

some components are donated.

part Quantity Unit cost Estmated

CostActual Cost

Sensor Gloves 1 $80 $80 $30 Air Muscles large 5 $50 $250 $250 Air Muscles small 6 $26 $26 $156 Valve Manifold 1 $160 $160 $160 Valves 4 $70 $280 $280 Regulator 2 $50 $100 $100 Air Line 3 $15 $45 $45 High Tensile String 1 $12 $12 $12 Ait Filter 1 $75 $75 $75 Hand and Forearm 1 $500 $500 $383 Electric Cylinder 1 $200 $200 $65 Enclosure/Display 1 $1,000 $1,000 $450 Microcontroller 1 $200 $200 $180 PC 1 $400 $400 $0 Electric circlts 1 $400 $400 $559.09 　　　　Total 　 $3,238 $3,728 $2,745

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