L OW A LT I T U D E BA L L O O N E X P E R I M E N T S I N T E C H N O L O G Y

( L A B E T ) VERSION IV

DEC09-14/LABETIV_SP09

P RO J E C T P L A N

FACULTY ADVISOR S AND CLIENT:

MATTHEW NELSON, DR. JOHN BASART

SPACE SY STEMS AND CONTROLS LAB

TEAM MEMBERS:

HENRI BAI

STEVE BECKERT

NATE GRINVALDS

IAN MOODIE

MIKE RAU

FEBRUARY 21 , 2009

DISCLAIMER: This document was developed as part of the requirements of a multi-discipline design course at Iowa State University, Ames, Iowa. The 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. Document users shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. Such 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 the document and the associated faculty advisors. No part may be reproduced without the written permission of the

senior design course coordinator.

LABET IV PAGE 2

Table of Contents Executive Summary ............................................................................................................................................. 3

Problem Statement ............................................................................................................................................... 3

General Problem Statement ........................................................................................................................... 3

General Solution Approach ........................................................................................................................... 3

Intended Use ......................................................................................................................................................... 4

Intended User ................................................................................................................................................... 4

Intended Use .................................................................................................................................................... 4

Operating Environment ................................................................................................................................. 4

Requirements ........................................................................................................................................................ 4

Functional Requirements ................................................................................................................................ 4

Non-Functional Requirements ...................................................................................................................... 4

Concept Sketch ..................................................................................................................................................... 5

Deliverables ........................................................................................................................................................... 5

Market Survey ....................................................................................................................................................... 6

LABET I ........................................................................................................................................................... 7

LABET II .......................................................................................................................................................... 8

LABET III ........................................................................................................................................................ 9

Other Markets ................................................................................................................................................10

System Description ............................................................................................................................................12

System Diagram .............................................................................................................................................12

Chassis Materials ............................................................................................................................................12

Structural Design ...........................................................................................................................................13

Motors .............................................................................................................................................................17

Servos ...............................................................................................................................................................17

Sensors .............................................................................................................................................................17

Wireless Control .............................................................................................................................................17

Power ...............................................................................................................................................................18

Miscellaneous Hardware ...............................................................................................................................18

Microcontroller ..............................................................................................................................................19

Software ...........................................................................................................................................................20

Project Management ..........................................................................................................................................20

Risk Management ...........................................................................................................................................20

Work Breakdown ...........................................................................................................................................22

Resource Requirements ................................................................................................................................23

Project Schedule .............................................................................................................................................25

LABET IV PAGE 3

Executive Summary The Low Altitude Balloon Experiments in Technology (LABET) project has had a strong history in the Space Systems and Controls Lab (SSCL) on the campus of Iowa State University. LABET was formed as a way to demonstrate the SSCL's work with helium balloons without the necessary setup time associated with High Altitude Balloon Experiments in Technology (HABET). The LABET setup consists of an aircraft equipped with electronic hardware and an attachment point for a helium balloon. The balloon provides roughly 90% of the aircraft’s lift and allows the aircraft to be wirelessly controlled throughout Howe Hall atrium or other indoor open areas. To date, three successful LABETs (LABET I, II, and III) have been built, all with unique qualities which will be addressed later in this document. A project team consisting of five students from Iowa State University has been established to design, test and build LABET IV. The team is comprised of students from the classes EE 491 and Engr 466. This team is made up of students in the disciplines of electrical engineering, computer engineering, mechanical engineering, and materials engineering. The team is under the direction of advisors Matthew Nelson, Chief Design and Operations Engineer of the SSCL and Dr. John Basart, retired professor in Electrical and Computer Engineering. In the following document, the project team will outline the overall design of LABET IV. This document will discuss the general problem statement, intended use, system requirements, market survey, system description, and project management.

Problem Statement

General Problem Statement

Iowa State University’s Space Systems and Controls Lab builds and tests various platforms for both academic and scientific missions. One of these platforms is the LABET. LABET is a platform for testing controls and other equipments using smaller and cheaper latex balloons. Three previous incarnations of the LABET project have already been constructed. Prior LABETs have lacked quality in flight control and maneuverability, solid construction, or an efficient user interface. Previous aircrafts lacked any ability to fly autonomously, limiting the knowledge that can be gained from their flight. LABET is also used as a demonstration tool for the SSCL lab and the college of engineering.

General Solution Approach

A new aircraft will be planned, designed, and constructed by the LABET IV project team. The team will use a completely new design for the aircraft. The new design will utilize new power, control, sensor, and flight systems. This design will include fewer fans with the ability to rotate axes. This will allow for greater in-flight maneuverability and superior control for the user. The new aircraft will also employ increased sensor feedback to improve in-flight control and create a platform for design of an autonomous landing feature. The project will also have a more professional appearance with a streamlined user interface.

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Intended Use

Intended User

The intended user for this product is the Space Systems and Controls Lab, located in 2362 Howe Hall. The aircraft will be operated by a single user from a base station. The base station will have complete control over the aircraft via wireless communication.

Intended Use

The SSCL has multiple intended uses for this product. The main use for LABET IV is as a promotional tool to be displayed during tours or events taking place in the Howe Hall atrium. A second use for LABET IV is as a test bed for future electronics. The SSCL will use LABET IV as a learning tool where students from a variety of engineering disciplines such as aerospace, materials, mechanical, computer, and electrical can work together to improve upon a single design.

Operating Environment

LABET IV will be operated in a controlled environment. Specifically, the aircraft will primarily be flown in the atrium of Howe Hall on the campus of Iowa State University. The aircraft will not be operated in high winds, but will encounter slight turbulence due to the building’s HVAC system. The aircraft will be operated in a confined space and will be subjected to walls, ceilings, railings, and sharp corners, all of which could damage both the aircraft and the balloon.

Requirements

Functional Requirements

FR-01: LABET IV must weigh less than 1.5 pounds FR-02: LABET IV must have minimum fly time of 20 minutes FR-03: LABET IV must have yaw control FR-04: LABET IV must have altitude control FR-05: LABET IV must have ability to traverse forward and backward FR-06: LABET IV must have ability to be controlled wirelessly FR-07: LABET IV must have ability to land autonomously on a table from 4 meters above FR-08: LABET IV must have attachment point for 100 gram balloon

Non-Functional Requirements

NFR-01: LABET IV design should be aesthetically pleasing NFR-02: LABET IV design should be innovative NFR-03: LABET IV should be easy to control NFR-04: LABET IV should be completed with thorough documentation

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Concept Sketch

Figure 1 – Concept Sketch

Deliverables The deliverables for LABET IV are a combination of class-specific and project-specific requirements. Website The project website will be constantly updated throughout the project duration. This website will be used to display the current status of the project and to host all documentation. Weekly Reports Weekly reports are a requirement for both classes (491 and 466). They will consist of two components – hour tracking and project status. Each week, an individual’s hours will be accounted for and added to a running total. The hours will be classified into general categories such as classroom, meetings, research, documentation, and other categories as the project progresses. Weekly reports will also consist of a short summary of the previous week on a group and individual level.

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Project Plan The project plan will be a document outlining the project. The project plan discusses the need of the project, requirements, market research, design strategies, and project management. Project Plan Presentation The project plan presentation will be a PowerPoint presentation given in class summarizing the project plan document. Design Document The design document will be a report outlining the complete design process for the project. This document will discuss the project on a component level and detail how each component will be incorporated into the system. More details on the design document will be available at the end of the spring semester. Design Presentation The design presentation will be a PowerPoint presentation given in class summarizing the design document. Bound Reports The bound report will be a document summarizing the entire semester’s work. More details will be available at the end of the spring semester. Functional LABET IV A functional LABET IV will be delivered in December 2009 in accordance to the requirements outlined in this document. In addition to a functional aircraft, the necessary firmware, software, wireless control, base station, and any necessary documentation to operate the LABET IV will also be delivered.

Market Survey The LABET project was conceived by Dr. Mani Mina, Professor in the Electronic and Computer Engineering Department at Iowa State University, as a smaller version of the High Altitude Balloon Experiments in Technology (HABET) project. Ultimately, the LABET would be easier to demonstrate, as the HABET requires a considerable amount of preparation as well as good weather conditions. In addition, LABET (as well as HABET) provides a platform in which engineers of different backgrounds can solve problems.

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LABET I

LABET I was the original version of the Low Altitude Balloon Experiments in Technology project completed at Iowa State. LABET I featured a single vertically mounted propeller, fit within a Styrofoam chassis. Two rudders, controlled by a servo, allowed for directional control. The landing supports are simply thin pieces of fiberglass bent with a string (analogous to a hunting bow). The user-interface was a simple joystick controller.

Figure 2 – LABET I

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LABET II

LABET II followed LABET I by a year, and represented vast improvements in design and functionality. LABET II uses a carbon fiber triangular chassis with two fixed, vertically mounted motors. As a whole, the device weighs less than one pound. Yaw control is provided by a horizontally mounted propeller. Pitch control is achieved by a servo that is attached by strings to the balloon. The aircraft is controlled wirelessly by custom software. The software displays the battery status, speeds of both the motors and the propeller, and shows the status of the gyro. LABET II is presently the LABET version showcased at various ISU events (such as First Lego League).

Figure 3 – LABET II

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LABET III

The LABET III team was tasked with finding an indoor as well as outdoor solution for a low altitude balloon. To satisfy this requirement, the design needed to be heavy enough to withstand outdoor conditions (namely, wind). The device weighs approximately six pounds, and uses four motors: two mounted vertically and two mounted horizontally. Each of these motors provides about three pounds of thrust, enough power to lift the device without a balloon. LABET III has been tested without a microcontroller, meaning that the motors were controlled manually. This made controlling the aircraft difficult, and LABET III has never successfully flown. Presently, LABET III is still an active project, but has taken a secondary priority to other projects.

Figure 4 – LABET III

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Other Markets

Commercial/Recreation Market Presently, most applications for low altitude balloons are for advertising in the form of a blimp inside sports arenas, concerts, etc. Most of these blimps have a very small, lightweight chassis that is directly attached or integrated into the blimp. Blimps can range from 10 feet long to 20+ feet long (by comparison, the balloon used for the LABET project is about 3 feet in diameter).

Figure 5 – Commercial Blimp

A sizeable market also exists for the use of low altitude balloons as toys. Remote control blimps are typically much smaller in size (3 foot long blimp) and are much less expensive. Where a commercial blimp used in advertising may cost $400 to $500, a toy remote control blimp may cost $50 to $100. Manufacturers such as Dragonfly Innovation, Inc. have product lines designed for commercial, military, education, and recreation markets. Aside from advertising, low altitude balloons and blimps are used for various photography purposes. Sky Reel Aerial Imaging (http://www.skyreel.com/) employs Dragonfly Innovations, Inc. products to capture aerial view images and videos.

Figure 6 - Image of Caesars Palace taken with Skyreel equipment

(http://www.skyreel.com/images/stories/easygallery/resized/15/1199658921_caesars_palace_pool.jpg)

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Military Market Many companies such as Mobile Airships and Blimps, Dragonfly Innovations, Inc, and Aerostar International manufacture blimps for commercial use and also military use. Aerostar International in particular is the maker of the Aerostat product line, which uses a tethered blimp/balloon as a platform for communications relaying, surveillance, search and rescue, etc. (http://www.aerostar.com/aerostat.htm). Dragonfly Innovations, Inc. manufactures various unmanned aerial vehicles (UAVs) for reconnaissance, target acquisition, and security purposes. Research Market A potential use for low altitude balloons is the study of the atmosphere of Venus. In 1994, a paper published in Advances in Space Research, detailed the feasibility of using a balloon that could withstand atmospheric pressures as high as 40 atm. and temperatures as high as 400°C. The balloon itself would need to be fabricated from robust materials such as titanium alloys. The balloon would also be required to carry electronics and other equipment that could weigh several kilograms. Education Market In addition to commercial uses, many low altitude balloons have been used for educational purposes. Several different programs exist that use blimps, low altitude balloons, and high altitude balloons to further education and learning. MIT, for example, uses a Dragonfly Innovations platform to develop a “swarm” of balloons to perform a collaborative task (http://www.draganfly.com/our-customers/education.php). Other programs, like the LABET project at ISU, use a low altitude balloon as a platform for problem solving.

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System Description

System Diagram

Microcontroller

Motor Drivers

Motors

Battery

Chassis

Sensors

Wireless Receiver

Servos

Roll

Yaw

Throttle

Gyro

Accelerometer

Sonar

Software Motion

Control

Autonomous

Landing

Control

Wireless Control

Wireless Transmitter

Figure 7 – System Diagram

Chassis Materials

Several factors must be considered when choosing a material for a given application. Material weight, strength, ability to process, and cost are some of those factors. When choosing a chassis material for the LABET, perhaps the largest factor is material availability. The second largest factor is weight. As required, LABET IV cannot weigh more than 1.5 pounds, thus, a tight weight

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restriction exists for the weight of the chassis alone. It was determined that the weight of the chassis should not be more than approximately 1/3 the total weight. Knowing the weight restrictions again reduces the list of materials to choose from. The initial list of materials included: aluminum, pine wood, foam, carbon fiber, various polymers, fiberglass, tubular plastic, balsa wood, etc. From this list, fiberglass, carbon fiber, and pine wood became the top choices. Carbon fiber, which was used in LABET II, was deemed inferior than fiberglass because it is not only a denser material, but also harder to fabricate. The extra strength of carbon fiber is not needed for this application. Other materials, such as balsa wood, are far superior to fiberglass or carbon fiber concerning weight, but lack the strength and durability needed. Although the project is in its early stages, it can be seen that fiberglass represents the best option. Using SolidWorks, several different chassis concepts were designed. For each design, the volume can be determined, and combined with the density of prospective materials, a rough weight can be calculated. Shown below are various materials along with theoretical weight of the chassis. It should be noted that 1.5 pounds is equivalent to 680 grams and 24 ounces. As mentioned above, it was determined by the team that the chassis should weigh no more than 250 grams and would ideally weight less than 200 grams.

Vol = 120 cm3

Material Density (g/cm3) Weight (g)

Fiberglass 1.500 180.0

Aluminum 2.700 324.0

Polycarbonate 1.200 144.0

PMMA (Plexiglas) 1.200 144.0

PET 1.400 168.0

Styofoam 0.100 12.0

Balsa wood 0.140 16.8

HDPE 0.955 114.6

Kevlar 1.470 176.4

urethane 1.000 120.0

Carbon Fiber 1.750 210.0

PCB material 2.150 258.0

Rubber 1.500 180.0

Pine wood 0.500 60.0

Table 1 - Chassis Materials

Structural Design

Designing a light weight and economical frame for an aircraft can be an arduous task. Combining the proper application of a composite material and a thin member frame, keeps the structure rigid and its weight low. The concept chosen for the LABET IV design will utilize this thin member concept with each component being only one eighth of an inch thick or less. The composite material chosen will determine the final component geometry.

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Figure 8 – LABET IV Frame Design

As shown in figure 8, two long beams span from fan to fan. Three cross members provide stiffness to prevent the chassis from twisting under loads from the fans and landing. Two cross beams on the top of the structure provide easy attachment for a balloon harness. Two additional cross beams on the bottom side of the frame will be notched for leaf spring-like landing pads. Additional tabs will be attached as needed to mount the hardware.

Figure 9 – LABET IV Frame Design With Balloon

The fans are mounted on a swivel ring, as shown in figure 10 below, allowing the fan to rotate about two axes. This rotation allows the fans to produce thrust in the fore and aft directions as well as strafing abilities. This pivot ring will need to be machined to provide a servo mount as well as pin attachment points. Mounting blocks will be glued to the fan duct to give flat surface for pin and servo attachment.

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Figure 10 – LABET IV Fan Design

Other Design Concepts and Tradeoffs

Chassis Design Advantages Disadvantages

Two motor Balloon

Cradle

-Lighter weight -Uses less power -May provide greater stability than

two motor with prop

-Less control than Three Motor -Less powerful lift

Three motor Balloon

Cradle -Most stable design -Most powerful

-Heaviest design -Three motors mean more battery

power

Two motor, one prop -Lighter weight -More control than other two motor

design

-Less powerful than three motor

design

One motor, two

props -Lightest design -Will require less battery power

-Least amount of stability

Table 2 – Design Tradeoffs One fan two props Building a single fan structure presents several issues in stability and maneuverability. The issue of counteracting the torque of the fan is necessary in almost any concept, more so for this design. The fan must be perfectly centered about the structure’s center of gravity. Any off balance can cause the aircraft to go into an uncontrollable spin. The use of two props would be required to effectively stabilize the aircraft. These props can prevent any gyro effect from the fan motor and can produce fore and aft thrust to easily maneuver the craft. The downside to using two props is the extra power consumption.

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Two fans one prop This design is a combination of the LABET II design and the chosen concept using two ducted fans with one stabilizing prop. This design requires a larger chassis, thus a slightly heavier design. The LABET II design has a simple triangular frame held together with large amounts of hot glue. Three fans The most stable flying platform utilizes three ducted fans, two mounted solid to the frame and one to rotate on an axis for yaw control. Another three fan design mounts all three fans on a rotatable axis for greater maneuverability and stability control. The downside to this design is the considerable amount of extra weight. Not only does a third fan add weight, but the necessary additional servos and battery capacity adds even more weight.

Chassis Requirements

Weights

2 Motor

Chassis

(Balloo

n

Cradle)

3 Motor

Chassis

(Balloo

n

Cradle)

2

Motor

Chassis

with

one

prop

1

Motor

Chassis

with 2

props

Scoring Range: 1 to 5 1, 3, 5, or 7

1.5 lb total weight limit 5 5 1 5 7

Easy Balloon Attachment point 3 5 5 5 5

Easy mounting of electronics 4 5 5 5 3

Fly time (20+ minutes) 5 5 1 5 7

Stability 4 5 7 5 3

Traverse Forward and Reverse 3 5 5 3 1

Altitude Control 3 7 7 7 5

Autonomous landing from 4 meter

altitude 5 7 7 5 5

Final Scores: 176 144 165 152

Table 3 – Decision Matrix

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Motors

Proper electric motor selections for ducted fans rely on several factors: application, environment, and cost. For LABET IV, environment will not be an issue as it is operated indoors only. The chosen design requires two motors to create a stable platform. The motors require variable speed controllers to provide maximum thrust for takeoff and maintain a minimum thrust for deceleration in autonomous landing. Two types of DC motors exist for hobby type aircraft - brushed and brushless motors. Brushless motors were chosen for LABET IV, though each type has advantages and disadvantages. Brushless motors are more efficient due to the lack of friction and electrical losses from the brushes in brushed motors. Longer life, reduced noise, and greater power are also advantages of brushless motors over brushed. Brushless motors are more expensive though and require a more complex speed controller.

Servos

LABET IV employs two fans to provide the lift and direction of flight. In order for the aircraft to employ both forward/backward and strafing movement, the fans must be able to tilt on two axes. Providing the power to tilt the fans on these axes will be several servomotors. Four servos will be employed in total, one for each axis of each fan. The aircraft has a strict weight requirement so the servos must be as light as possible while still providing enough torque to adjust the fan direction. These servos will be 15 grams or less in weight while providing 1 to 3 kg cm in torque. They will also run on a voltage of 4 to 7 V. These specifications should allow the aircraft to meet all other functional requirements while providing the multidirectional movement that is desired.

Sensors

LABET IV will employ several types of sensors to help in-flight control, maintain stability, and assist in autonomous landing. The sensors used during in-flight manual control will be an accelerometer and a gyro. The accelerometer will be used to maintain altitude. As the balloon only provides 90% of the lift, the aircraft will need to provide the remaining 10% of lift to maintain a constant height. The accelerometer will be able to detect any deviation in vertical position and allow for a correction in thrust. A gyro will be used to maintain the stability of the aircraft when it is in flight. The aircraft design employs two fans. Because of this design, a two axis gyro will be needed to measure both the roll and the yaw. Two single axis gyros may be employed to save on costs, as single axis gyros are less expensive then gyros with multiple axis capability. The accelerometer and an additional sonar sensor will be employed when the aircraft enters its autonomous landing mode. The sonar sensor will be used to detect the distance between the aircraft and the table that it is landing on. The decision to employ a sonar sensor over an infrared sensor was made because the aircraft must be able to land autonomously from a minimum of four meters and this range cannot be achieved with a typical infrared sensor. When the range to the table is determined the accelerometer will be employed to control the rate of descent to the table. These two sensors should ensure that the aircraft will land autonomously without damaging any of the hardware.

Wireless Control

In accordance with FR-06, the aircraft will be controlled wirelessly. Previous LABETs have accomplished this by using a dedicated hand-held controller, or by the use of a laptop computer. In both cases, the radio frequency 433 MHz was used. Before wireless control can be implemented, the

LABET IV PAGE 18

project team must decide whether data will be transmitted both ways or only be sent from the base station to the aircraft. The benefit of single direction transmission is obviously simplicity. However, if the aircraft is able to transmit data back to the base station, the operator can maintain real-time feedback such as battery life, fan speeds, and sensor data. Regardless of the method chosen, the receiver located on the aircraft will be connected to the microcontroller. The controller will then translate the desired movement into fan speed and servo angles. The biggest obstacle in any communication system is electronic noise. Noise exists naturally as temperature changes and current-carrying electrons randomly move. Noise can be a difficult problem when large currents are present in tight spaces. The project team will need to take caution when routing the circuit board to ensure that communication lines are not being crossed by a clock signal or any high-power lines.

Power

Battery power is a major constraint for LABET IV. There exists a strict tradeoff between battery capacity and weight. To overcome this issue, the aircraft will be powered by lithium-ion polymer (LiPo) batteries. Research into the battery market has shown that LiPo batteries have an unmatched combination of small size, light weight, and high capacity. All previous LABETs have been equipped with LiPo power supplies. When selecting the appropriate battery, the project team needs to consider a few factors – voltage, maximum discharge current, and capacity. The necessary voltage of the aircraft’s power supply will be dependent on specific components. With that in mind, it is safe to say the necessary voltage will be determined by the motor selection. The motors in question have voltage requirements ranging between 6 and 12 Volts. In order to achieve this voltage, multiple 3.7 Volt LiPo batteries will be placed in series. The aircraft will require 2 or 3 cells in series for a combined voltage of 7.4 Volts to 11.1 Volts. The maximum discharge current will be determined by the specific components selected. Again, the motors will be the primary draw on the batteries and require anywhere between 3 and 8 Amps each. Adding together the total draw among all components, the aircraft will require a maximum current discharge range of 10 to 25 Amps. The capacity of a battery determines how long the aircraft can fly on a single charge. Ideally, the batteries chosen would have a very large capacity to maximize flight time however, capacity is directly proportional to weight. A battery’s capacity is measured in milliamp hours. That is, a battery with a capacity of 2500 mAh could supply a constant 2.5 Amps for one hour. To determine the necessary capacity, an average current draw must be estimated. In order for the aircraft to reach its requirement of a 20 minute flight time, a battery with a capacity between 1800 and 2500 mAh will be needed. In summary, the aircraft will require a power supply capable of providing 7.4 to 11.1 Volts, have a maximum discharge current of 10 to 25 Amps, and have a capacity of 1800 to 2500 mAh. Such a power supply will be constructed with a parallel combination of LiPo batteries in series, likely totaling 4 individual batteries. Such a scheme will cost roughly $60 and weigh a total of 200 grams.

Miscellaneous Hardware

In addition to the hardware previously mentioned, LABET IV will need other hardware components to tie everything together.

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Passive Components Passive components are often the most common item on a completed circuit board. Resistors and capacitors will be needed in order to link important hardware together and to the appropriate power supply. Specifically, bypass capacitors will be used to filter the input power signal before each component. This filtering decreases the ripple voltage and supplies a reliable power signal to a component. Voltage Regulators Not all components on a circuit board can be powered by the same voltage as the battery outputs. For this reason, a voltage regulator stands between the battery and most hardware. Regulators output a steady and reliable voltage. The hardware found in the aircraft will likely need supply voltages of 1.8, 3.3 and 5 Volts. Regulators will be needed to supply each of these voltages. Motor Drivers Motors require a large current to rotate at such high speeds. The motor also needs to be controlled by the microcontroller in order to operate autonomously. However, the motor would permanently damage the microcontroller if it were hooked up directly. A motor driver acts as an interface between the microcontroller and the motor. A motor driver can either be a dedicated integrated circuit or as simple as a single transistor. In either case, the driver will take an input signal from the microcontroller and supply a certain current to the motor.

Microcontroller

The microcontroller chosen will need to have the following desired features: 1. Must be fast enough to perform automatic landing of the aircraft 2. Must be energy efficient 3. Must have low cost

Previous LABET projects have utilized PIC controllers. LABET IV will also employ a PIC controller, as the SSCL highly recommends continuing with this selection. These controllers feature a fast clock speed that can reach up to 1 MHz. They also include various instructions regarding signal processing. This includes finite impulse response filters, numeric integrators and various bit operations. The controllers contain instructions that power down the processor into a low power state, throttle the processor speed, and lower the voltage used. These characteristics translate into increased energy savings. An algorithm will be designed to incorporate these features. These microcontrollers range from $1 to $10, depending on the model and quantity purchased. The PIC microcontroller has analog to digital signal conversion features. This enables to poll sensors and directly use these values as a digital value. The precision of the analog to digital conversion sensors usually range from 10 bits to 12 bits. The input voltage will have to be regulated in order to get the correct voltage for the analog to digital conversion to work. The PIC microcontroller’s input voltage will range from 3.3 to 5.5 Volts. The PIC controllers include numerical integrators and differentiators, which are useful in PID controllers. There are also many free tools to compile and upload software to the PIC microcontroller. Other microcontrollers require licenses and proprietary software in order to do so. This will reduce the cost of the aircraft. The PIC microcontroller also has constant time interrupts. This will enable faster and more responsive stability algorithms to be used. Diagnostic probing will also not intrude in the operation of the aircraft. Depending on the sensors used, the PIC microcontroller’s I2C capability may be used. This would allow the sensor and motor data to be multiplexed on one date line and not have to deal with complicated wire management.

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Software

The software will serve two main purposes. First, it will translate sensor data and the desired movement from the base station into motor speed and servo angles. On top of this, the software will need to constantly alter these outputs in order to maintain stability of the aircraft. Secondly, the software will need to make decisions in order for the aircraft to land on a table autonomously. There are many methodologies for developing the software. One such method is known as event-driven programming. The event-driven method is based on a data queue which is updated each time something is requested. When the queue is populated, the CPU is interrupted and the queue is processed. The flaw in this methodology however is instructions in the queue are not necessarily processed instantly. Another possible methodology would be thread or process management. This would require the creation of an operating system, which may be more work than necessary for the project team. The basic approach to the software would be to run all tasks in an infinite loop. These tasks in no specific order would include reading each sensor, receiving communication from the base station, determining what is necessary to maintain stability, and positioning the fans in order to achieve the movement desired by the pilot. Overall, the software will require much trial and error in order to make the aircraft's movement as efficient as possible.

Project Management

Risk Management

Risk: 491/466 Coordination Management: Since the LABET IV project team is comprised of students in multiple classes, there may be future issues involving requirement coordination. This risk will be managed by maintaining constant communication between team members in both classes. Each class schedule will be examined weeks in advance to foresee coordination issues. In the event of scheduling conflicts, both class instructors will be informed of the issue. Risk: Unfamiliarity with technology Management: While working on LABET IV, the project team may be unfamiliar with technology being used in the design process. This risk will be managed by taking advantage of all knowledge resources available. In the event of unfamiliarity with a certain technology, the project team will seek out individuals who have had experience with the technology in question. These individuals can include the project team’s advisors, team members from previous LABET projects, members of the SSCL, other professors within Iowa State University, or other students within Iowa State University. Risk: Damage to sensitive hardware components Management: Many of the components to be used on LABET IV can be damaged by electrostatic shock. This risk will be managed by thoroughly reading the appropriate datasheets for each component in order to understand the individual component’s risk.

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Risk: Design delays due to component shipping delays Management: Some components used in LABET IV may need to be purchased by a third party and be delivered through the mail. Delays in shipping will be avoided by purchasing components at least two weeks in advance of when the component is needed. In the event of an extended delay, the project team will attempt to locate temporary replacement parts or work on a different portion of design while the component is being shipped. Risk: Damage to LABET IV while in flight Management: Since LABET IV will be tested in closed environment, there is a risk of damage if the unit hits a solid object. This risk will be managed by selecting open areas for flight tests and by keeping the unit at low altitudes until familiarity is gained with the controls. Risk: Injury to team during fabrication Management: In order to fabricate structural components of LABET IV, the project team will risk injury with the use of potentially dangerous tools. This risk will be managed by attending the required training sessions over the use of specific tools.

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Work Breakdown

LABET IV

AircraftBase Station Documentation

Website Project Plan

Design

DocumentBound Reports

Structure Motors Servos

Structure Design

Composite

Selection

Composite

Testing

Structure

Fabrication

Structure Testing

Motor Research

Motor Selection

Motor Testing

SensorsPowerMicrocontroller Wireless Control

Servo ResearchMicrocontroller

Research

Wireless

ResearchBattery Research Sensor Research

Servo SelectionMicrocontroller

Selection

Transmitter/

Receiver

Selection

Battery Selection

Gyro,

Accelerometer,

Sonar Selected

Servo TestingSoftware

Development

Transmit/Receive

TestingBattery Selection

Gyro,

Accelerometer,

Sonar Testing

Component

Integration

Printed Circuit

Board

System Testing

Hardware

Selection

Wireless

Control Testing

Figure 11 – Work Breakdown

LABET IV PAGE 23

Resource Requirements

The LABET IV project requires several resources for successful completion. These include the labor of the team members, hardware for the aircraft, and a computer for the control system.

Component Cost Number Total Cost

Motors/Fans $12.00 2 $24.00

Servos $18.00 4 $72.00

Chassis Material $0.00 1 $0.00

Balloon $0.00 1 $0.00

Sonar Sensor $13.00 1 $13.00

Accelerometer $18.00 1 $18.00

Gyro Sensor $20.00 1 $20.00

Wireless Transmitter $14.00 1 $14.00

PIC $8.00 1 $8.00

Batteries $14.00 4 $56.00

Ground Station $0.00 1 $0.00

Total Aircraft Cost $225.00 Table 4 – System Cost

LABET IV PAGE 24

Task Name Cost

Steve Beckert Ian Moodie Mike Rau Nate Grinvalds Henry Bai

Totals, @ $20/hour $23,620.00 262 262 262 133 262

Documentation $3,800.00 38 38 38 38 38

Project Presentation 4 4 4 4 4

Project Plan 9 9 9 9 9

Design Document 12 12 12 12 12

Website 1 1 1 1 5

Poster 5 5 5 5 1

Final Report 7 7 7 7 7

Research $6,600.00 72 72 71 43 72

Chassis Design 4 4 22 18 2

Fans/Motors 4 4 18 2 4

Servos 4 14 16 2 2

Control 8 8 1 1 24

Wireless Transmission 16 4 1 1 18

Sensors 10 22 3 2 10

Power 24 14 2 2 10

Chassis Material 2 2 8 15 2

Design $5,420.00 57 57 56 44 57

Aircraft Design 30 30 36 36 30

Controller Design 27 27 20 8 27

Development $2,760.00 34 34 36 0 34

Aircraft Development 20 20 24 0 14

Controller Development 14 14 12 0 20

Testing $5,040.00 61 61 61 8 61

Component Testing 25 25 25 8 25

Controller Testing 12 12 12 0 12

Aircraft Testing 12 12 12 0 12

Project Testing 12 12 12 0 12

Hours

Table 5 – Projected Engineering Costs

LABET IV PAGE 25

Project Schedule

Table 6 – Spring Semester Gantt Chart

Table 7 - Fall Semester Gantt Chart