SWAT Reconnaissance Vehicle
Final Proposal
Group member names:
Richard Walloch1
Scott Zenier2
Chris Johnston3
Travis Arnzen
Vincent Zhao
2008/09
Project Sponsor: Salem Police Department
ME 418
Project Number: 53
Faculty Advisor: Dr Hurst, Dr. Tumer
Sponsor Mentor: William Wiltse
1
Lead editor #1, responsible for editing chapters 1 and 2
Lead editor #2, responsible for editing chapters 4 and 5
3
Lead editor #3, responsible for editing chapters 3 and 6
2
DISCLAIMER
This report was prepared by students as part of a college course requirement. While considerable effort has
been put into the project, it is not the work of a licensed engineer and has not undergone the extensive
verification that is common in the profession. The information, data, conclusions, and content of this report
should not be relied on or utilized without thorough, independent testing and verification. University faculty
members may have been associated with this project as advisors, sponsors, or course instructors, but as such
they are not responsible for the accuracy of results or conclusions.
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EXECUTIVE SUMMARY
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TABLE OF CONTENTS
ACKNOWLEDGEMENTS .................................................................................................................................... 6
1. PROJECT DESCRIPTION ............................................................................................................................. 7
1.1.
Background ............................................................................................................................................. 7
1.2.
Requirements .......................................................................................................................................... 7
1.2.1.
Statements of Need ......................................................................................................................... 7
1.2.2.
Customer Requirements (CRs) ....................................................................................................... 8
1.2.3.
Engineering Requirements (ERs) ................................................................................................... 8
1.2.4.
Testing Procedures .......................................................................................................................... 9
1.2.5.
House of Quality (HoQ)................................................................................................................ 13
2. EXISTING DESIGNS, DEVICES, AND METHODS ................................................................................ 15
2.1.
General Discussion ............................................................................................................................... 15
2.2.
Descriptions .......................................................................................................................................... 15
2.2.1.
iRobot PackBot ............................................................................................................................. 15
2.2.2.
RHex ............................................................................................................................................. 16
2.2.3.
Dragon Runner .............................................................................................................................. 17
2.2.4.
iRobot Negotiator.......................................................................................................................... 17
2.2.5.
Recon Scout IR ............................................................................................................................. 17
2.2.6.
BullDog ......................................................................................................................................... 18
2.2.7.
TALON ......................................................................................................................................... 18
2.2.8.
Whegs ........................................................................................................................................... 19
2.2.9.
MATILDA II ................................................................................................................................ 19
2.2.10. The Crusher ................................................................................................................................... 20
2.2.11. robuROC 6 .................................................................................................................................... 20
3. DESIGNS CONSIDERED ........................................................................................................................... 22
3.1.
Drive Train ............................................................................................................................................ 22
3.1.1.
Fixed Tracks.................................................................................................................................. 22
3.1.2.
Articulating Tracks ....................................................................................................................... 23
3.1.3.
Six-Wheeled Vehicle .................................................................................................................... 24
3.1.4.
Spoked Wheels.............................................................................................................................. 24
3.2.
Vehicle Control ..................................................................................................................................... 25
3.2.1.
Wireless Router............................................................................................................................. 25
3.2.2.
Hobby Remote Control ................................................................................................................. 25
3.2.3.
Video Game Controller ................................................................................................................. 26
3.3.
Audio and Video Feedback ................................................................................................................... 26
3.3.1.
Integrated Audio/Video System .................................................................................................... 26
3.3.2.
Baby Monitor ................................................................................................................................ 27
3.3.3.
High Power Tx/Rx Component System ........................................................................................ 27
3.4.
Power Systems ...................................................................................................................................... 28
3.4.1.
Isolation vs. Decoupling ............................................................................................................... 28
3.4.2.
Cell Types ..................................................................................................................................... 28
3.4.2.1. NiMH ............................................................................................................................................ 28
3.4.2.2. Sealed Lead Acid (SLA) ............................................................................................................... 29
3.4.2.3. Lithium-Ion Polymer (LiPo) ......................................................................................................... 29
3.4.3.
Voltage Regulators........................................................................................................................ 29
3.4.3.1. Linear Regulators .......................................................................................................................... 29
3.4.3.2. Switching Regulators .................................................................................................................... 30
4. DESIGN SELECTED ................................................................................................................................... 30
4
4.1.
Rationale for Design Selection ............................................................................................................. 30
4.1.1.
Drivetrain: Fixed Track................................................................................................................. 30
4.1.2.
Vehicle Control: Hobby Remote Control ..................................................................................... 31
4.1.3.
Audio/Video: High Power Transmitter ......................................................................................... 32
4.1.4.
Battery Cell Type .......................................................................................................................... 32
4.1.5.
Voltage Regulators........................................................................................................................ 32
4.2.
Design Description................................................................................................................................ 33
4.2.1.
Drivetrain ...................................................................................................................................... 33
4.2.1.1. Track – Link Based ....................................................................................................................... 33
4.2.1.2. Motors ........................................................................................................................................... 34
4.2.1.3. Chain Drive ................................................................................................................................... 35
4.2.1.4. Tensioning..................................................................................................................................... 35
4.2.2.
Chassis .......................................................................................................................................... 35
4.2.2.1. Material – Aluminum Sheet Metal ............................................................................................... 35
4.2.2.2. Track Profiles ................................................................................................................................ 35
4.2.2.3. Center Structure ............................................................................................................................ 36
4.2.3.
Control .......................................................................................................................................... 37
4.2.3.1. Controller – RC Controller ........................................................................................................... 37
4.2.4.
Audio/Video.................................................................................................................................. 37
4.2.5.
Power ............................................................................................................................................ 38
4.2.5.1. Battery ........................................................................................................................................... 38
4.2.5.2. Voltage Regulation ....................................................................................................................... 38
5. IMPLEMENTATION ................................................................................................................................... 40
5.1.
Chassis .................................................................................................................................................. 40
5.2.
Drivetrain .............................................................................................................................................. 40
5.3.
Power .................................................................................................................................................... 40
5.4.
Control .................................................................................................................................................. 40
5.5.
Audio/video........................................................................................................................................... 40
6. TESTING ...................................................................................................................................................... 41
7. PROJECT ETHICS ....................................................................................................................................... 41
8. PROJECT SUMMARY ................................................................................................................................ 41
9. BIBLIOGRAPHY ......................................................................................................................................... 42
10.
APPENDIX A: BILL OF MATERIALS .................................................................................................. 44
11.
APPENDIX B: PART DRAWINGS .........................................................Error! Bookmark not defined.
12.
APPENDIX C: PART DRAWINGS ........................................................................................................ 48
5
ACKNOWLEDGEMENTS
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1. PROJECT DESCRIPTION
1.1. Background
Police officers sometimes find themselves in situations that are beyond the level of training or equipment
and may involve heavily armed and dangerous persons who pose considerable danger to hostages and
bystanders. To handle these dangerous situations, elite SWAT (Special Weapons and Tactics) teams have
been created in most large cities. SWAT teams are trained and equipped to deal with hostage situations,
terrorism, high-risk arrests and other dangerous scenarios. Their equipment includes powerful weapons,
tactical devices and other technology to help them resolve situations safely.
These high-tech devices include fiber optic cameras, night vision goggles, throwable cameras and remote
control reconnaissance vehicles. All of these devices help collect real time information such as locations of
suspects and bystanders, suspect activity and building layouts. This knowledge is crucial to making the right
decisions and minimizing risks in potentially deadly situations.
The Salem Police Department has commissioned mechanical and electrical engineering students at Oregon
State University to design and build a remotely controlled SWAT reconnaissance vehicle that can enter
potentially dangerous situations and provide a live audio and video feed, allowing the SWAT team to assess
a given situation from a safe distance. The focal points of this design, established in collaboration with the
Salem Police Department, include: the abilities to ascend and descend stairs, to send and receive live audio
and video and to wirelessly control the vehicle. This vehicle will be used as a measure to preserve the safety
and increase survivability of SWAT team members. In addition, this device should have a much lower price
tag than the $20,000 purchase price of commercially available SWAT vehicles. The budget for this project
has been capped at $3400.
1.2. Requirements
1.2.1. Statements of Need
The following statements of need were received from the Salem Police Department. A primary
designation indicates requirements for minimum acceptable vehicle functionality while a secondary
designation indicates vehicle functionality which is desired but not required. A designation of “other”
indicates requirements which may be waived, provided that the underlying functionality is provided by
other systems.
Primary:
1. Navigate stairs or debris inside a building
2. Broadcast audio/video back to a (forward) base station
3. Wireless operation with extended battery life
4. Low-light, no light video
5. Articulating camera
6. Water resistance / waterproof
7. Two-way (one-way) audio capability
8. Sustainable design
9. Intuitive user interface
Secondary:
10. Deliver/carry items
11. External lighting
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Other:
12. Right itself if knocked over (Nullify with stable design?)
13. Multiple cameras / camera views
1.2.2. Customer Requirements (CRs)
The following list of customer requirements (CRs) was derived directly from the given statements of
need as well as from conversations with the sponsor. These requirements fully define the desired
performance of the vehicle and are prioritized based on the needs expressed by the sponsor. The sponsor
has stated that the highest priority is to have a basic vehicle that can get to locations and relay audio and
video information back to officers. The medium and low priority items are optional extras that would be
nice to have but would not prevent the vehicle from being functional if they were not included.
Primary
1.
Ascend and descend household stairs
2.
Navigate debris on household surfaces
3.
Stream live video with a pan and tilt capable camera
4.
Functionality not impaired by low-light or no light conditions
5.
Control robot wirelessly
6.
Operate in Oregon rainfall for short durations
7.
Extensive training not required to operate robot
8.
Stream audio from robot to base
9.
Vehicle is easily deployable by two individuals
10.
Sustainable design
11.
Operate on self-supplied power for duration of mission
Secondary
12.
Carry and deliver light items (cell phone or a pack of cigarettes)
13.
Transmit audio from base to robot
Other
14.
Right itself when knocked over
1.2.3. Engineering Requirements (ERs)
Team members of the project created measurable and quantifiable engineering requirements (ERs) to
meet all of the established customer requirements. These ERs will serve as design parameters that the
vehicle can be tested against to determine how well it meets the customer’s needs.
The Salem Police Department has expressed mobility as a top priority. One of the biggest obstacles to
navigating in an urban environment is stairs. ERs were specified that corresponded to the riser height
and angle of a standard home staircase. Household stairs represent some of the steepest that may be
encountered in a mission. Basic vehicle handling and maneuverability has been quantified by the time it
takes to negotiate a common room. Debris of at least 4 inches tall must be negotiable by the vehicle so
that it can move through cluttered areas. While crossing obstacles the vehicle must be able to lean at
least 25 degrees in any direction without falling over. Angles this steep will probably only be seen while
ascending or descending stairs.
The vehicle must retain mobility at a distance and for the duration of a mission. The vehicle control
system must have at least 250 feet line of sight range. The onboard battery systems must be able to
power the vehicle for at least 1 hour driving 20% of the time. This runtime represents driving into a
building to locate suspects and then maintaining surveillance. The vehicle must also be able to operate
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for at least 2 minutes in rainfall so that it can travel from its deployed location to a building on a rainy
day.
Multiple ERs have been created to address the CRs pertaining to wirelessly streaming audio and video.
Minimum range requirements for audio and video transmission of 250 feet line of sight were set so that
personnel can be kept at a safe distance. For the transmitted video to be useful, a resolution of 200
horizontal lines and maximum delay of 300 milliseconds have been specified. In order to view all of the
vehicle’s surroundings a camera pan and tilt of at least 270 degrees and 45 degrees respectively will be
required. Objects must be identifiable at a minimum of 10 feet even in no-light conditions so that they
can be avoided. Audio sent to the robot should be audible from a minimum of 10 feet away so that
instruction can be heard across a room.
The officers using this vehicle are not robotics experts nor will they have excess time to devote to
training. For these reasons ease of operation and a sustainable design are important. It should take no
more than 2 hours to get an operator sufficiently trained to navigate a standard room. The vehicle needs
to be easy to deploy and transport. It should weigh no more than 80 pounds and have no dimension
(length, width or height) longer than 45 inches. These ERs will allow it to be deployed by two officers.
To be a sustainable design a majority of the parts (>75%) must be orderable from vendors and require
only simple installation without modification. Staying within the funding limits of the project (currently
$3400) will ensure that replacement parts are affordable.
1.2.4. Testing Procedures
1. Stair Height
Vehicle must be able climb from a flat surface over a vertical edge that is greater than 7” in height
onto another flat surface. Once the vehicle has done this it must be able to continue to move forward.
2. Angled Climb
Vehicle must be able to climb a surface which has an incline of 35°, which is measured from the
horizontal ground surface.
3. Ascend Stairs
Vehicle must be able to ascend 5 consecutive stairs with a tread height of greater than 7 inches and
an incline of greater than 35°. Vehicle must start on flat, level ground at a distance of 5 feet from the
base of the stairs. Vehicle must climb unaided onto stairs and ascend with no operator intervention
until rear axle passes and is no longer in contact with the 5th stair. Test is passed if vehicle
successfully climbs 5 stairs in this manner in 3 out of 5 attempts. The attempt is failed if any
operator intervention is required.
4. Descend Stairs
Vehicle must be able to descend 5 consecutive stairs with a tread height of greater than 7 inches and
an incline of greater than 35°. Vehicle must start on flat, level ground at a distance of 2 feet from the
top of the stairs. Vehicle must descent stairs with no operator intervention until rear axle passes and
is no longer in contact with the 5th stair. Test is passed if vehicle successfully descends 5 stairs in
this manner in 3 out of 5 attempts. The attempt is failed if any operator intervention is required.
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5. Debris Navigation
Vehicle must navigate through a hallway filled with household debris. Hallway width must be
between 30” and 36”, hallway length will be 5’. Debris for the course will be a size 10 shoe, a large
size pizza box, a phone book and a sweatshirt. Debris will be laid out according to Figure 1-1.
SHOE
PIZZA BOX
SWEAT SHIRT
PHONE BOOK
Figure 1-1 Vehicle Navigation Course
6. Video Range
Create a distance of 250 feet between the vehicle and the operator. There must be an unobstructed
line of sight between the controller and the vehicle. The image that the camera is viewing must be
displayed on the output device located 250 feet from the robot.
7. Video Quality
The number of horizontal video lines will be counted and cannot be lower than 200.
8. Video Delay
To measure the video delay, a stopwatch which measures in milliseconds will be placed above the
LCD monitor. The camera for the vehicle will then be pointed at the stopwatch so that it will appear
on the LCD monitor. Another camera will be used to take a picture of the LCD monitor and
stopwatch while the stopwatch is running. This picture will display the real time, on the stop watch,
and the delayed time, on the stopwatch on the LCD monitor. The delayed stopwatch reading time
will be subtracted from the real time stopwatch reading. This different cannot exceed 300
milliseconds.
9. Camera Pan
Vehicle must be placed on a flat surface and in a stationary position. The camera will be rotated a
range of 270° in the horizontal direction.
10. Camera Tilt
Vehicle must be placed on a flat surface and in a stationary position. The camera will be tilted a
range of 45° in the vertical direction.
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11. Identify Objects in Dark
The vehicle will be placed in a room with no light. A shoe, a phone book and a pizza box will be
placed approximately 10 feet in front of the camera. Using the camera, the operator of the vehicle
must be able to identify each of the objects.
12. Control Range
Create a distance of 250 feet between the vehicle and the operator. There must be an unobstructed
line of sight between the controller and the vehicle. Sufficient control signals must be verified at the
vehicle.
13. Operate in Rainfall
Vehicle will be exposed to simulated rainfall at the rate of .04 inches per hour for two minutes. The
vehicle must demonstrate the same level of operability as it had prior to the simulated rainfall. This
includes basic mobility, camera vision, camera pan and tilt capability and audio.
14. Operator training
A person who is unfamiliar with the functioning of the robot must be able to learn/be instructed how
to use the vehicle in under two hours. Throughout the training, the operator must be able to
demonstrate the basic ability to the move forward and backward, turn left and right and pan and tilt
the camera. The operator must also be able to complete the maneuverability procedure at some point
during the training session. However, the operator will not be required to complete the
maneuverability test if the maneuverability test was failed by the team.
15. Audio Range
Create a distance of 250 feet between the vehicle and the operator. There must be an unobstructed
line of sight between the controller and the vehicle. A team member will be located in front of the
robot and will talk. The words being spoken must be clearly audible by the person holding the
controller.
16. Weight
The vehicle will be placed on a scale and must weigh less than 80 pounds.
17. Dimension
The distance using a straight line between any two points on the vehicle must not exceed 45”. This
will be measure with a tape measure.
18. Unmodified Components
At least 75% of the total number parts on the vehicle must be unmodified by the operator to make
the vehicle work. The total number of parts which are unmodified will be counted and divided by the
total number of parts. The part count does not include hardware.
19. Cargo Weight
The vehicle must demonstrate mobility by moving forward a distance of ten feet while carrying a
weight of four pounds. The weight must be within the specified dimensions of the cargo volume.
20. Cargo Volume
A box which has the approximate dimensions of 4”x4”x6” must be able to fit on the robot and not
fall off of the robot while moving forward or backward.
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21. Audibility
A person will stand in front of the vehicle at a distance of 10 feet. This person must be able to hear
what the operator of the vehicle is saying through the speaker that is mounted on the vehicle. The
operator of the vehicle must have a clear line of sight between him and the vehicle. However, the
person near the vehicle must not be able to hear the operator without the aid of the speaker. The
environment of the vehicle must be one that is relatively free of background noise.
22. Run Time
Vehicle must be able to drive for 12 minutes and idle for 48 minutes on a single battery life. The
vehicle will drive approximately 50 feet, turn around and drive back the same distance. The vehicle
will do this for 12 minutes. It will they idle for 48 minutes. The vehicle must remain on for the 60
minutes.
23. Tip Angle
Vehicle will be placed on a flat and moveable surface which is wider and longer than the vehicle.
The must not flip over when the surface is tilted 25° in any direction. This angle will be measure
from the ground which will be horizontal.
24. Cost to Build
The entire cost to build the vehicle should not exceed $3300. The cost to build includes the
following: part costs, shipping costs, material costs and machining costs that are associated with the
initial build. All of these costs will be added together and cannot exceed $3300.
25. Cost to Test
The cost to test refers to the costs associated with performing each of the tests specified. An example
of this would be the platform which will be used in the Tip Angle test. These costs will be added
together and the total cannot exceed $100.
26. Cost to Revise
The cost to revise refers to the costs associated with any revisions that are made after the initial
build. An example of this would be if a circuit board goes out and a new one needs to be purchased.
These costs will be added together and the total cannot exceed $600.
27. Total Cost of Project
Cost to build, cost to test and cost to revise will be added together and will not exceed the total
budget.
28. Maneuverability
Vehicle must be able to navigate a prescribed course which is defined by red Dixie cups. The course
is shown in Figure 1-1. To complete this task the vehicle must be able to successfully navigate the
course one out of two times. A successful attempt is defined as navigating through the course and
hitting two or less cups in under five minutes.
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82.40
48.00
48.00
R 41
Figure 1-2 Maneuverability Course
1.2.5. House of Quality (HoQ)
The House of Quality developed for this project maps customer requirements to testable and quantifiable
engineering requirements. Each of these ERs carries an associated weight which signifies the importance
to the project. The House of Quality is shown in Figure 1-3.
13
Figure 1-3 House of Quality
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2. EXISTING DESIGNS, DEVICES, AND METHODS
2.1. General Discussion
As the field of robotics advances the products available to SWAT teams become more capable and more
obtainable. The use of technology to improve SWAT team response is becoming commonplace. Remote
controlled vehicles for bomb disposal have been around since the early 1970s. There are many products
currently available that could fulfill the requirements of the Salem SWAT Team but none that fit their
budget. The current products offer a large range of designs each using particular methods to accomplish
specific tasks. The majority of the designs which are currently being used tend to utilize a track or wheel
based drive train. However, the means of transportation can get extremely complex. With added complexity
comes increased precision and ability to accomplish certain tasks. Therefore attention will be directed at the
drive train of the vehicle, especially if it has the ability to navigate over stairs and debris. Drive train designs
which are capable of these tasks, and represent the current state-of-the-art, include tank style tracks,
articulating track systems and wheeled vehicles. In addition, focus will be given to off-the-shelf solutions
which are commercially available.
2.2. Descriptions
Many designs have been created to fulfill a range of requirements similar to the ones presented in this
project. The robots range in size as well as complexity. While none of the designs offer a complete solution
in the budget range of this project, elements from these designs can serve as a starting point for a new
design.
2.2.1. iRobot PackBot
The iRobot PackBot, shown in Error! Reference source not found., is the most combat-ready
econnaissance vehicle available on the market today. This robot is available in many different
configurations from the manufacturer. The Explorer configuration fulfills all of the customer
requirements outlined by the project sponsor. The only disadvantage on this vehicle is its substantial
price at over $80,000.
Figure 2-1 iRobot PackBot Explorer (1)
Two critical customer requirements are the ability to ascend and descend stairs and to navigate
household debris. The drive train design of the PackBot is under special consideration due to the fact
15
that it excels in these areas. The PackBot has an articulating tread design which allows it to adapt its
shape to address the task to be performed. The treads on the front of the vehicle can be raised, enabling
it to very effectively crawl over obstacles or initiate stair climbing. The front treads can be lowered once
the vehicle has climbed onto the first stair, allowing it to span three full steps for a quick and smooth
ascent along the stair noseline.
In its Explorer configuration, the PackBot comes with an articulating camera capable of 360 degree pan
and 270 degree tilt. This addresses a customer requirement and is another point of interest on the
PackBot. The camera is mounted on an elevated arm which provides an improved viewing angle,
allowing it to see over obstacles. The camera also comes equipped with near-infrared light emitting
diodes and a camera that supports this technology. The end result is a camera which is not impaired in
low light and no light conditions. This is another customer requirement that is fulfilled by this robot.
A third feature of the PackBot which brings it under consideration for this project is the ability to
survive submersion in water up to 6 feet. The customer requirement for this project is much more
lenient, but careful analysis of the PackBot design may yield valuable insight. (1)
2.2.2. RHex
RHex, shown in Figure 2-2, was first created as a DARPA research project. The concept was to emulate
the movement of a cockroach. The mechanism behind the motion is the timed sequence of rotations of
three sets of leaf spring legs. This concept makes for a very robust robot which can easily travel up and
down stairs. It also has a great ability to traverse rough terrain such as a swamp or a rock mound. RHex
can be controlled at up to 600 meters. Front and rear view cameras are mounted on this robot for
visibility. (2), (3) While RHex meets most of the customer requirements for this project, it lacks in one
particular area. The cameras on RHex are not articulating. This problem could be solved by simply
mounting an articulating camera, however this would present a difficulty due to the inherently bumpy
motion of RHex. This type of design utilizes six independent drive motors with a complex control
system which may be beyond the scope of this project.
Figure 2-2 RHex (4)
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2.2.3. Dragon Runner
The Dragon Runner, shown in Figure 2-3, by Foster-Miller was created for military use. It is part of a
class of military robots called SUGVs (small unmanned ground vehicles). It offers a configurable drive
system using wheels or tracks. This vehicle can traverse variety of terrain including urban environments
with debris and stairs. This robot has a range of accessories available including manipulator arms,
cameras and various sensors. Overall, this design offers a very refined and complete design but its
military spec and price are beyond the needs and budget of the Salem Police Department. (5)
Figure 2-3 Dragon Runner (5)
2.2.4. iRobot Negotiator
The Negotiator, shown in Figure 2-4, is a lighter, cheaper sibling of the PackBot. The Negotiator is one
of the most capable and affordable options currently available. Its articulating tracks allow it to excel at
negotiating stairs or debris. iRobot has used its experience to create a rugged robot that has shock
absorbing treads that can stand lots of abuse. The Negotiator has a 3-6 hour battery life and a control
range of 800 feet which is sufficient for most SWAT missions. At an approximate price of $20,000 the
negotiator is cheaper than the competition but still outside of the available funds. (6)
Figure 2-4 iRobot Negotiator (7)
2.2.5. Recon Scout IR
The Recon Scout IR, shown in Figure 2-5, has a unique capability to be thrown through the window of a
building, land, and maintain operability. The drive train uses a simple two wheel mechanism. These
wheels are attached to a simplistic tube-like body which acts as a counterweight and is dragged behind
the drive wheels. The Recon Scout is outfitted with an infrared camera, allowing for low light and no
light use. The most apparent benefits of this design are the robustness and simplicity of its body.
However it fails to meet a few of the design requirements. The Recon Scout IR does not have the ability
to ascend stairs, which is one of the projects core requirements. (8), (9)
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Figure 2-5 Recon Scout IR (9)
2.2.6. BullDog
The BullDog, shown in Figure 2-6, was designed for use by the West Covina SWAT Team. It should be
considered for this project because it satisfies many customer requirements. This robot has a camera
which is mounted on a small scissor lift and streams live audio and video to a remote location. An item
of particular interest on this robot is the articulating arm, which has the ability of lifting objects that
weigh up to 50 pounds. This robots shortfall is its inability to ascend or descend stairs. The drive train
consists of four wheels which are not suspended, severely limiting its mobility in a hostile environment.
(10)
Figure 2-6 BullDog (10)
2.2.7. TALON
The Foster-Miller TALON, shown in Figure 2-7, is a reconnaissance vehicle which can be transported
by a single operator. The ruggedness was characterized when it was blown off a Humvee into a river in
Iraq and still survived. It can climb stairs and navigate over rough and extreme terrain. The TALON’s
camera capabilities are unmatched, with the ability to hold four color cameras, each capable of include
18
night vision, thermal imaging, and auto-zoom. The TALON also features two-way audio
communication and other optional accessories such as a shotgun mount or chemical sensors.
One of the biggest shortcomings of the TALON is the complexity. Two-and-a-half days of training in
Massachusetts are needed to operate this vehicle, limiting the number of people who can be trained and
greatly increasing the initial investment cost. Although advertised as being portable by a single person, it
weighs between 115 and 156 pounds. (11) The cost of a TALON is over $60,000. (12)
Figure 2-7 TALON (13)
2.2.8. Whegs
Case Western Reserve University developed a series biologically inspired robots, one of which is
referred to as Whegs, shown in Figure 2-8. The name is a combination of wheels and legs, this name
accurately describes the robots movement. Whegs has the ability to navigate over obstacles which are
located above the center of its wheels. The downfall of this robot for SWAT reconnaissance vehicle
application is that it has not been shown to ascend and descend stairs reliably. (14)
Figure 2-8 Whegs (14)
2.2.9. MATILDA II
The Mesa Robotics MATILDA, shown in Figure 2-9, features an angled track design, allowing it to
navigate stairs and debris in its path. This vehicle weighs 61 pounds and is able to operate in all weather
and has a pan and tilt camera assembly. The MATILDA II has cameras in the front and rear with twoway audio. It can be controlled via a complex briefcase unit or a more simple and intuitive handheld
19
unit. MATILDA II fits the needs of the Salem Police Department. The only disadvantage is that the
price for the MATILDA is not listed. It is not unreasonable to assume a price that is well beyond the
budget of this project. (15)
Figure 2-9 MATILDA II (15)
2.2.10.
The Crusher
The Crusher, shown in Figure 2-10, is an extremely sophisticated and complex autonomous vehicle. It
weighs 6.5 tons and is modeled after a Humvee and the Abrams tank. While having the capability to
carry a payload of 4 tons, the Crusher navigates with a series of sophisticated sensors. It finds its way
from one point to another with only a few simple GPS coordinates. When an obstacle exceeds a height
of two meters the vehicle plans a path around it. Otherwise, the vehicle relies on its 30 inch clearance
and extreme independent suspension. The size and magnitude of this vehicle are beyond the scope of
this project. However, the unique use of six wheels with a large amount of travel may offer a viable
solution for ascending and descending stairs. The basic concept of this robot meets many of the core
requirements and provides many useful ideas. (16)
Figure 2-10 The Chrusher (16)
2.2.11.
robuROC 6
The robuROC 6, shown in Figure 2-11, is a wheeled vehicle that is capable of climbing stairs. While this
vehicle is much larger than required or desired by the Salem Police its general layout could be used in a
smaller vehicle. Each of the three articulated sections has two wheels. The articulation allows the
20
vehicle to conform to the surface and maintain contact with the ground. A six wheeled vehicle with a
layout similar to the robuROC would stand the best chance of climbing stairs for a wheeled design. (17)
Figure 2-11 robuROC 6 (17)
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3. DESIGNS CONSIDERED
3.1. Drive Train
3.1.1. Fixed Tracks
“From a mobility perspective, tracked vehicles offer the best solution for a versatile mobile platform that
is required to operate over diverse terrain, including extremely difficult ground, because tracks
inherently provide a greater surface area than wheels.” (17) Tank tracks have been successfully
implemented on a wide variety of vehicles, from small scale hobby robots which are less than one foot
in length to a 67 ton M1A1 tank. The M1A1 clearly demonstrates the capabilities of a tracked vehicle,
and has been a main battle tank of the US military for over 20 years.
Implementation of a tank tread drive train will require, at a minimum, the following components for
each track: a drive motor, a drive wheel, a series of idler wheels and a tensioned track system which is
wrapped around the outside of the idler and drive wheels. It is important to note that this track design
serves two primary purposes: to transfer power from the drive wheels to the rest of the drive train and to
remain in contact with the ground to provide traction.
The ability of a tracked vehicle to climb stairs effectively brings it under special consideration for the
project. Tracked vehicles with a wheelbase longer than 2 b2  h2 , see Figure 3-1, have the ability to
seamlessly ascend the noseline of the stair. Ascending stairs in this manner is ideal because the
consistent points of contact with the noses of the stairs makes the vehicle very stable when transitioning
from one stair to the next.
Figure 3-1 Tracked Vehicle Ascending Stair Noseline (17)
While a long track length aids a vehicle in climbing stairs, it inhibits the vehicle’s turning ability and
increases the turning radius. Turning characteristics of tracked vehicles are vastly different than those of
common wheeled vehicles. Turning is achieved by “skid-steering,” which means to drive one track at a
different speed than the other. This causes the tracks to skid and induce rotation of the vehicle. Skid
steering allows the unique ability of a vehicle to pivot about its center if its tracks are driven at equal
22
speeds in opposite directions. These characteristics facilitate maneuverability in close quarters at the
expense of electrical efficiency, as a high amount of power is required to force the tracks to skid.
3.1.2. Articulating Tracks
The current state of the art in tracked robotics is the articulating tread design. This type of design utilizes
a single motor per side to drive pairs of parallel treads and allows one set of treads to be raised or
lowered together. An excellent example of this design is the iRobot Negotiator, seen in Figure 3-2.
Figure 3-2 iRobot Negotiator Climbing Stairs (6)
Articulating tracks provide incredible versatility when maneuvering on or around obstacles. The
auxiliary track position can be altered to provide optimal traction when mounting, traversing, or
dismounting an obstacle or navigating difficult terrain. The tracks can be lowered to allow for more
tread contact area, or raised to decrease the turning radius and facilitate turning with less skidding. One
extremely important aspect of this tread design is that it can effectively climb stairs with a much shorter
wheelbase than a fixed tread design. The treads can be raised to allow the vehicle to climb on the first
step, then lowered to span two complete steps and seamlessly ascend the noseline of the stairs, see
Figure 3-1. An additional benefit of the articulating tread design is that the auxiliary treads can be used
as a self-righting mechanism should the vehicle flip over.
Implementation of articulating tracks presents significant challenges when compared to a fixed track
system. Special attention must be directed to drive train tolerances because both tracks must be driven at
the same speed, retain sufficient tension at all times and track interference must not occur. The system
must allow one motor per side to drive both treads or provide a total of four drive motors. Additional
servos would be required to raise and lower the auxiliary treads and they must be capable of lifting the
weight of the entire vehicle.
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3.1.3. Six-Wheeled Vehicle
Vehicles with a properly implemented wheel-based drivetrain have proven effective in traversing
difficult terrain. One important element of this type of drive train is the ability to allow relative motion
between the wheels and vehicle chassis. This passive articulation of the wheels allows the vehicle to
retain contact with the ground where a vehicle with no suspension would not, thus providing increased
ability to traverse difficult terrain. Vehicles such as the Crusher and robuROC 6 clearly demonstrate the
abilities of a six-wheel-drive platform but are both far too large to be used for typical SWAT operations,
Figure 2-11 shows the effectiveness of the robuROC 6 climbing stairs.
While six-wheel-drive vehicle platforms have been proven to effectively navigate difficult terrain,
special design considerations must be made to allow such a vehicle to ascend stairs. Unlike tracked
vehicles which can ascend the noseline of a set of stairs, wheeled vehicles must climb up and over each
stair with every set of wheels.
Another important consideration for a six-wheeled-vehicle design is the manner in which the wheels are
driven. A very complex drive train would be required to power all six wheels from a central power
source because of the suspension, which allows relative motion of the wheels to the chassis. Driving all
six wheels independently requires six motors, which will significantly increase the weight of the vehicle.
3.1.4. Spoked Wheels
Many universities and government agencies are looking into the problem of climbing stairs. Some the
more interesting work has focused on alternative wheel designs incorporating lobes or spokes that stick
out from a central hub. These robots look like normal RC cars with the wheels swapped for the new
design. Most designs are steered using differential drive, the wheels on one side turn faster than the
other; however a traditional carlike steering could be implemented.
These designs offer the potential for vehicles to climb obstacles that are taller than the wheel center.
Wheeled vehicles must rely on friction to pull the vehicle up the obstacle while the normal force is
pushing the vehicle back. The spokes on the other had create a normal force that lifts the robot rather
than push it backwards and the frictional force pulls the vehicle forward, see Figure 3-3. Once on the
stairs, if the spokes and axles are properly spaced, the nose of the stair will fall between spokes allowing
the wheel to act like a gear, quickly ascending the stairs.
Figure 3-3 Comparison of Stair Climbing Ability of Wheels and Spoked Wheels (19)
Spoked wheels offer great mobility in a small and simple design but they do have some draw backs. One
advantage is that they do not need to be long like a tracked vehicle that needs to span multiple stairs.
This makes the vehicle lighter and more able to fit in tighter spaces. Performance in situations beyond
24
stairs would not be as good as other design options. The spokes would create uneven motion due to the
changing distance between the axles and the ground. This could make controlling the vehicle difficult
from a camera mounted to the chassis.
3.2. Vehicle Control
3.2.1. Wireless Router
This project was attempted last year and utilized a wireless 802.11g network control system. This
consisted of TS7200 microcontroller and a Linksys WRT-54G Ethernet Bridge which sent commands to
the vehicle via a laptop computer. The user interfaced with the vehicle via a java program written by the
team. In addition to providing complete control of the vehicle, the program provided live audio and
video feeds. Using the java interface, the control station sent commands to the microcontroller, which
then relayed those commands to the motor controller. The system acted like an onboard computer and
required integrated design and complex coding (20).
A control system such as this provides an integrated solution to the end user. Laptops, PDA’s and other
consumer electronics support Java applications, leaving the end user many choices for a control
platform. This system is very expandable because additional network devices can be added to the
vehicles router or attached to the microcontroller. Examples of devices include sensors, servos, cameras
or a robotic arm. An additional advantage of this system is that is has already been designed, built and
tested.
The major disadvantage of this solution lies in its current state of operation. The Java application was
run on two different laptops and failed to work properly. All vehicle controls were inoperable, streaming
audio did not work in either direction, and the camera system which worked refreshed at a rate of less
than 1 frame per second. The software also caused one of the computers to crash on two occasions.
Utilizing this design would require computer science resources which are beyond the capabilities of
current team members. A large amount of time would also be required to reverse engineer this solution
to fully understand how it functions, to determine which systems function at an acceptable level and
which systems need to be changed.
3.2.2. Hobby Remote Control
Hobby-level remote control (RC) systems are a very common way to provide control for a differential
drive vehicle. A six channel aircraft RC system would utilize four channels to provide the operator
control of the vehicle with one joystick and control of the pan and tilt camera with a second joystick.
The remaining two channels provide expandability and could be used for auxiliary lighting or servo
control.
Using an aircraft RC system would allow the reuse of the Sabertooth motor controller. This is a top-shelf
component, capable of supplying power to two motors independently, at 24V and up 50A peak per
channel. This control board switches at 32kHz, so it is not audible and has built in thermal and over
current protection. The Sabertooth controller requires only a speed and direction PWM input from the
aforementioned aircraft RC system to control for a differential drive vehicle. This is a considerable
advantage because it allows intuitive control of the vehicle with one joystick. This controller also has
synchronous regenerative drivers, which extends operational life by allowing current to flow back into
the batteries. One design consideration of the Sabertooth motor controller is that it generates a lot of heat
25
(21). This heat is well managed with a heat spreader and heat sink, but may require a small amount of
active cooling.
Hobby level RC systems typically operate on 72MHz, 75MHz and 2.4GHz. The 72MHz band is
reserved for air vehicles only. Many 2.4Ghz radios utilize spread spectrum technology, which allows
active switching of available frequencies and significantly reduces the possibility of signal interference
with other RF devices. A six channel 2.4GHz RC system will cost about $220 (22). Some modification
of this system may be required to provide the user an integrated control solution.
3.2.3. Video Game Controller
Modern video game controllers which operate on the 2.4GHz frequency present an interesting solution
for vehicle control. Examples of these are the wireless controllers utilized by the Playstation 2 (PS2) and
Microsoft XBOX360 consoles. Third party companies, such as Lynxmotion, modify these controllers
for use on robotic vehicles.
Video game controllers have the potential to reduce training time required to efficiently operate the
vehicle. This is due to an intuitive control interface and a high likelihood of operator familiarity with the
controller. These controllers come at a cost of about $20 (23) but require an additional board and
microcontroller such as AX500 with Basic Atom, for a total cost of over $100 (24). A major
disadvantage of this controller is that its operational range is limited to 75 feet, falling short of the 250
foot line of sight engineering requirement.
Utilizing a system with a microcontroller would provide the functionality of the Sabertooth motor
controller, would allows for expandability and is capable of logging internal data parameters. Along
with this increase in functionality comes programming complexity, which is a major concern due to the
groups lack of experience with microcontroller coding. The AX500 is only capable of digital output, so
it would require an additional digital-to-analog converter (DAC) between the controller and drivers (25).
It would also cost $145 (26).
3.3. Audio and Video Feedback
3.3.1. Integrated Audio/Video System
Using a wireless router as a vehicle control solution would allow for an integrated audio and video
feedback system. This type of system was used when this project was attempted last year. Microphones
and webcams were setup as network devices to stream live feeds over the connection. The user received
this information on any device which supports Java applications, such as a laptop of PDA (20).
This system is convenient because it utilizes the computing potential of electronics which are already
onboard the vehicle to provide audio and video feeds. The integration of this system into the vehicles
network system saves money, as specific transmitters and receivers are not required for this system. The
components which make up the vehicles network system, however, are very expensive (20). There is
also substantial lag between the camera and the Java user interface, resulting in a screen refresh rate of
less than frame per second. The vehicles network system is currently in a state of disrepair, and the team
does not currently have the resources or knowledge required to troubleshoot it.
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3.3.2. Baby Monitor
A baby monitor is a common household item which has the ability to wirelessly stream audio and video.
These systems typically come with a remote camera and a receiver with built in LCD and speaker. Many
baby monitors include IR sensitive lens and IR LEDs, providing integrated night vision functionality.
These systems have a range of up to 300 feet and some systems offer integrated pan and tilt kits,
providing 270 degree pan and 120 degree tilt. The cameras included with these systems feature low
current draw, even with the IR LEDs on (27).
This is an appealing option because its off the shelf functionality meets many of our customer and
engineering requirements. This system would, however, present challenges for implementation.
Providing the user an integrated control solution would be difficult because the pan and tilt controls for
the camera would be located on a device separate from vehicle control. Integrating the pan and tilt
controls of the baby monitor into a RC controller would require a digital to analog converter, as digital
controls are used on the baby monitor (27). The range of the baby monitor solution is a cause for
concern, because the maximum stated range is approximately equal to the minimum engineering
requirement.
3.3.3. High Power Tx/Rx Component System
High power transmitters and receivers present a very appealing audio and video solution. This is a
component system, as cameras, lenses, transmitters and receivers can all be specified and purchased
separately. These systems are designed for RC and hobby use, and as such are very compact and
lightweight. Figure 3-4 shows a camera with transmitter attached to a standard 9V battery next to the
receiver.
Figure 3-4 Wireless Video Camera, Transmitter and Receiver (28)
Cameras available for this type of system cost about $100, are extremely small and lightweight, have
low current draw, and provide excellent video quality. These cameras have better picture quality than
standard DVDs and an auto switch between (color) day mode and IR sensitive black and white night
mode (29). The size and weight of the camera makes it ideal for use with hobby level components, such
as a pan and tilt kit. Lenses which provide a wide angle of view are available, allowing the operator to
be more aware of the vehicles surroundings.
High power transmitters operate in the 2.4GHz range, offer transmit power of 200mW to 1W and have
an expected range of about 5,000 feet (30). These units are deemed high power for their transmission
27
power, not power consumption. A 1W transmitter, camera and microphone together will use less than
500mA from a 12V source (31). Matching receivers for this type of transmitter are compact and would
have to be wired to a separate LCD. This type of audio and video solution lends itself well to an
integrated and portable yet custom user control unit. The control unit would consist of a RC radio, a
video receiver, an LCD and a power source.
3.4. Power Systems
3.4.1. Isolation vs. Decoupling
High power motors generate a great deal of electric noise which may adversely affect other components
on the vehicle. This can be easily dealt with by isolating or decoupling the motors from the rest of the
electronic systems. Both of these options have advantages and disadvantages.
The incorporation of decoupling capacitors in the power supply design will reduce the electric noise and
still allow the vehicle to function from a central power source (32). The advantage of this is approach is
that all of the vehicles power can be used for either navigation or surveillance, making the vehicle
equally well suited for missions which require long periods of surveillance and those which require it to
move great distances. The disadvantage of this system is that it increases the complexity of the power
supply circuitry and may still allow some noise into the rest of the circuit.
The second option for dealing with motor noise is to power the motors with an independent power
source, providing complete isolation of the motors and effectively eliminating motor noise. This is a
common practice which was recommended the project faculty advisor. Isolating the power systems of
the vehicle may reduce vehicle versatility, as power is designated for each system. An additional circuit,
however, may be implemented to allow the vehicle to function on either power supply.
3.4.2. Cell Types
3.4.2.1. NiMH
NiMH batteries are the most commonly used battery type for hobby and RC use, making them
readily available, relatively inexpensive and easy to replace. NiMH cells which are under
consideration for this project come in AA, C, and D sizes and have a nominal and end voltages of
1.2V and 1.0V respectively (33). Two battery packs were used for the project last year, and consisted
of twenty NiMH cells each.
The low internal impedance of NiMH cells allows them to handle high discharge rates. They also
have a flat discharge curve, allowing the batteries to maintain constant voltage until the end of the
cycle (34). The high energy density of NiMH batteries allows longer operation time at a reasonable
weight. They are environmentally friendly and can be recycled easily. NiMH batteries are middle of
the spectrum with respect to cost (35).
NiMH batteries have a self-discharge rate of about 4% per day (34) . They need to be fully
discharged every three months to extend their lives, which is generally limited to 200-300 cycles
(35). NiMH batteries also generate a lot of heat, so overcharge/over-discharge protection is needed,
and they need to be cool before charging or discharging to maintain their health (36).
If NiMH batteries are utilized for this project, they will need to be purchased. The battery packs
constructed last year are held together with solder, cardboard boxes, and duct tape. Some of the cells
also show signs of physical damage. There are multiple imprecise solder joints, creating a higher
28
potential for electrical failures. Additionally, the packs from last year contributed almost fifteen
pounds to the weight of the vehicle, so it will be necessary to reduce the number of cells being used.
3.4.2.2. Sealed Lead Acid (SLA)
Sealed lead-acid batteries have a nominal voltage of 2V and an end voltage of 1.75V per cell (33).
They are commonly used in scooters and golf carts. These batteries are relatively low cost, highly
reliable (they are used by hospitals and in virtually all automobiles), and have a service life of 300500 cycles (35). Like NiMH, SLA batteries have a flat discharge curve (34). They do not generate
significant heat during operation, can be easily recycled, and only self-discharge at a rate of five
percent per month (36). The low internal impedance of SLA batteries allows them to handle a full
range of discharge rates. They can also be left to float charge for a long period of time (37).
Sealed lead-acid batteries have some important disadvantages as well. They cannot be stored in a
depleted state and they need to have their charge topped off every 3-6 months. SLA batteries need to
utilize a trickle-charger or a three-stage charger to prevent overheating. Though they can be
recycled, they are not environmentally friendly. The biggest disadvantage of using SLA batteries for
this project is weight, as they much heavier than NiMH or LiPo (36).
3.4.2.3. Lithium-Ion Polymer (LiPo)
Lithium-Ion Polymer batteries are commonly found in consumer electronics where size and weight
are an issue. LiPo cells have a nominal voltage of 3.7V and an end voltage of 2.75V per cell (33).
LiPo batteries can be as thin as one millimeter. They are more resistant to overcharge and there is
less likelihood of electrolyte leaking from the cell (38). LiPo batteries also have a life of over 500
cycles, and they can maintain their charge for 12 months. LiPo batteries are very susceptible to
damage by over discharge and generally require over discharge protection circuitry. LiPo batteries
are used in high end hobby applications due to their extremely high energy density. LiPo batteries
can be designed to support current draws as high as 90 amps continuous (39).
3.4.3. Voltage Regulators
3.4.3.1. Linear Regulators
Linear regulators typically utilize an active device such as a BJT or MOSFET, operating in its active
region. This type of regulator is essentially operating as a self-adjusting voltage divider. A linear
voltage divider cannot step-up voltage, so it requires a source that is greater than the desired output
voltage. Additionally, linear voltage regulators generally require a source that is at least two volts
above the output voltage.
Linear voltage regulators would require the use of 14.8V battery packs since the control unit and
vehicle components require up to 12VDC for operation. These batteries cost approximately 50%
more than 11.1V batteries with the same amp-hour rating. Linear regulators would also dissipate a
lot of heat. This would require very large heat sinks and forced air cooling to prevent damage to the
regulators.
29
3.4.3.2. Switching Regulators
Switching regulators operate by rapidly switching a device (typically a MOSFET) off and on, so it
dissipates almost no power. This allows them to achieve high efficiency. Operating at higher
frequencies achieves a higher efficiency, but higher frequencies also introduce electromagnetic
interference (EMI). Unlike linear voltage regulators, switching regulators can output a voltage
greater than the input.
Switching regulators require the use of components with low equivalent series resistance (ESR)
components. All capacitors and inductors add some real resistance to the circuit, and minimizing the
ESR is important for the proper functioning of a switching regulator. These components are typically
more expensive than those that offer higher ESR. Switching regulators will also require the use of
printed circuit boards due to the complexity of the circuits.
4. DESIGN SELECTED
4.1. Rationale for Design Selection
4.1.1. Drivetrain: Fixed Track
Of the designs considered, the fixed track was selected as the most appropriate solution. This design
offers simple and robust features while still adhering to the engineering and customer requirements. This
conclusion was reached through the use of the decision matrix in Figure 4-1. The critical parameters for
the design of the drivetrain were to: ascend and descend household stairs, navigate debris and maintain a
sustainable design. Research has shown that a fixed track design can accomplish all of these tasks (18).
The six wheel drivetrain was the first design to be discarded. Research showed that this design had
difficulty climbing stairs. There is also the issue of providing power to all of the wheels, which is
necessary when climbing over obstacles. A spoked wheel design was also considered but quickly
discarded due to the bumpy motion and lack of mobility required in many instances. The most
comparable alternative drivetrain was one which was tracked based and included articulating tracks.
This met all of the drivetrain requirements as well. The articulating flipper arms allowed the vehicle to
be more flexible in certain situations. However, the added complexity did not offer enough advantages
to make it worth the undertaking. The fixed track design is a well rounded solution that meets the project
requirements.
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Figure 4-1: Decision Matrix for Drivetrain
4.1.2. Vehicle Control: Hobby Remote Control
Hobby remote controllers are a proven solution for wireless vehicle control. The other systems
considered could not compete with range that is offered by the hobby remote control. The game
controller does not meet the minimum requirements and the wireless g is only marginally above the
minimum requirements. Hobby remote control units are designed to interface directly with the types of
system components that we are using. The most compelling feature of the wireless g solution is its large
potential for expandability. However, the hobby remote control offers similar expandability without the
complexity. The categories and weighting associated with the decisions made can be found on Figure 42.
Figure 4-2 Decision Matrix for Vehicle Control
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4.1.3. Audio/Video: High Power Transmitter
The selection of the hobby remote controller as a standalone system makes the use of the webcam and
router impractical on the vehicle. Baby monitors present an inexpensive, simple solution but lack the
range and pan and tilt functionality required for this project. The High Power Transmitter provides the
best solution for this system. Figure 4-3 shows relevant system attributes and associated scores for each
system.
Figure 4-3 Decision Matrix for Streaming Audio and Video
4.1.4. Battery Cell Type
Lithium Polymer batteries were selected for use in this project. Their extremely high energy density,
support of high discharge rates and low self discharge rate make them ideal for this application. The
additional cost of these batteries is more than offset by their positive attributes, as indicated in Figure
4-4.
Figure 4-4 Decision Matrix for Battery Cell Type
4.1.5. Voltage Regulators
Linear voltage regulars are simpler to implement, requiring fewer components. However, they require
the purchase of larger battery packs and are less efficient to use. The power dissipated is equal to (VinVout)*Iout. For large currents or large voltage differences, the power dissipated is very significant.
Stepping down from 14.8V to 5V with an output current of 700mA results in 6.86W of heat dissipated.
32
Switching regulators are more complex to implement, necessitating PCB design, but their efficiency is
higher, resulting in almost no power dissipation. Switching regulators allow all the use of 11.1V battery
packs, which are less expensive than 14.8V battery packs. Additionally, battery life is very important to
the project, so switching regulators are the best choice for this design. The rationale for this selection is
supported in Figure 4-5.
Figure 4-5 Decision Matrix for Voltage Regulators
4.2. Design Description
4.2.1. Drivetrain
The fixed track drivetrain solution required the selection of various components based on the
Engineering Requirements. Description of the components and rationale for the selection is found
below.
4.2.1.1. Track – Link Based
The key considerations for track selection are as follows:
- Traction on various surfaces
- Cost
- Sustainability
- Reliability
There are a limited number of solutions which are commercially available. The two prominent
solutions are a link based system and a continuous rubber belt. The link based system prevails due to
the highest number of comparative advantages. The base of the track is 45A rubber which is very
soft and has a high coefficient of friction on many surfaces. (40) This provides the desired
functionality for meeting the engineering requirements to ascend and descend stairs. The continuous
belt system also had similar traction characteristics however it was only available at a high cost.
Another advantage of the link based track system is that it offers a complete solution including track,
cogs, and hubs. This complete solution has a high level of sustainability due to a reduced number of
custom parts. The ability to remove individual links also allows for easy maintenance and
adjustability. The track can be sized to the vehicle which facilitates the tensioning of the track.
Proper track tension is necessary to keep the track on the vehicle. The positive engagement between
the track and the cog teeth restrict the track from coming off making it more reliable than belt
solutions. Figure 4-5 shows a picture of out tracks.
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Figure 4-6 Lynxmotion Tracks (40)
4.2.1.2. Motors
The key considerations for motor selection are as follows:
- Torque output
- Weight
- Size
- Current Draw
- Vehicle Speed
The motors selected are salvage components from the prior year’s project. This component selection
translated into a significant cost savings. The specifications for the motors are categorized in Table
4-1.
Table 4-1 Motor Specifications (41)
Reduction
Ratio
1:12
Rated Torque
Rated Speed
kgf-cm
rpm
11
285
No Load
Current
Stall Torque
mA
mA
kgf-cm
<2850mA
<700mA
300
Rated Current
These specifications are more than sufficient for the application in which the motor will be used. The
high torque output is more than the required amount to maneuver and clear obstacles. The motors
weigh 3.5 pounds which is acceptable given the maximum allowable vehicle weight. The motor has
a length of 7.25 inches and a diameter of 2 inches. These motors can easily fit into a chassis which
meets the size requirements.
The vehicle must be able to explore an environment efficiently to provide meaningful data. This
directly relates to the vehicle speed. Therefore vehicle speed was calculated based on the rated speed
of the motor. The vehicle speed was found to be 3.81 ft/s which is approximate to a human walking.
Shown below is the calculation:
1min 1 ft
 rev 
 in 
 ft 
R
x
 v   (EQ. 1)
 xD 
 xGRx
60s 12in
 min 
 rev 
 s 
 rev 
 in  18teeth 1min 1 ft
 ft 
285 
x
x
 3.82  
 x3.75 
x
 min 
 rev  22teeth 60s 12in
 s 
R : Re volutions
D : Diameter
GR : GearRatio
v : Velocity
34
4.2.1.3. Chain Drive
For ground clearance and center of gravity reasons it was decided to used a chain drive mechanism
to transmit power from the motor to the drive cog. Direct driving the track system would require the
mounting of the motor to be at ground level. This severely inhibits the ability of the vehicle to climb
objects. Also, by having the motors in the middle of the vehicle shifts the center of gravity towards
the center. This allows for a smooth motion when ascending and descending stairs. A chain drive
allows for further variation of the drivetrain gearing allowing greater flexibility to meet
requirements.
4.2.1.4. Tensioning
Maintaining tension in the track and chain drive systems is vital to keeping the vehicle moving. The
system used to tension the track must apply and maintain sufficient force. The tensioning system
designed consists of sliding bearing blocks (02-003) with threaded holes. Screws will then be
installed to push on fixed blocks (02-006). The mechanical advantage of the screws will make it easy
to tension the tracks securely and will provide significant resistance to slipping.
4.2.2. Chassis
Once the drivetrain had been specified a chassis could be designed to accommodate it.
4.2.2.1. Material – Aluminum Sheet Metal
The key considerations for material selection are as follows:
- Strength
- Rigidity
- Weight
- Cost
- Machining
The material selected to construct the bulk of the chassis greatly influences futures design decisions.
Aluminum sheet metal and plywood were the two most feasible choices for the chassis design. Each
of these materials had more than the necessary strength to withstand the loading during operation.
Many of the drivetrain components require tight tolerances on spacing in relation to other parts,
therefore limited deflection is required. Formed aluminum sheet metal displays a high resistance to
deflection. However, plywood is very rigid in nature as well. In addition designs from either material
would be sufficiently lightweight. The major driving factor in selecting aluminum sheet metal was
the cost. Aluminum sheet metal and the machining of it are donated. This factor allowed for a clear
decision to be made.
4.2.2.2. Track Profiles
The key considerations for track profile design are as follows:
- Potential to climb stairs
- Rigidity
- Track Interface
One of the core requirements of this project was for the vehicle to have the ability to climb stairs.
Having the proper track profile is vital to climbing stairs. In order to meet the initial design target of
climbing a stair with the height of 7.75 inches, the center of the top hub must exceed this height.
35
This will allow the vehicle the easily mount the first stair. To insure smooth ascension, the base of
the profile must exceed the nose-line of two stairs (shown in Figure 4-7) and be in contact with two
stairs at all times. These dimensions are household stair dimensions. In addition there are
calculations which show the minimum dimensions that the vehicle must have.
h
d
Ө
w
Figure 4-7 Stair Dimension Diagram
d  h2  w2 (EQ. 2)
(7.75in) 2  (10in) 2  12.65in
h
tan 1     (EQ. 3)
 w
 7.75 
tan 1 
  37.78
 10 
d  Noseline
h  height
w  StairDepth
  StairAngle
The calculations performed using equations 2 and 3 show the dimensions necessary to climb stairs.
One stair noseline is shown to be 12.65 inches, however for smooth ascension the base of the track
must be twice this amount. The incline angle of the stairs based on common household dimensions is
37.78° which can be show with equation three.
Rigidity is an important faction in a track profile design because any significant deflection can cause
misalignment of axles allowing a track to be thrown. If properly designed, a sheet metal track profile
can be very robust. To restrict the amount of deflection incurred, two track profile plates will be
placed in parallel and secured with spacers. These profile plates can be seen in parts 01-001 and 01004, these are the outer and inner plates respectively. To increase the stiffness, bent flanges will line
certain parts of the profile.
It is important to not impede the motion of the track. This will maximize the life of the track and the
efficiency of the power use. The bent flanges and edges which line the profile will be covered with
plastic molding. This increases the surface area that the track is in contact with and reduces the
friction. The bent flange on the top of the profiles will further increase the surface area to
compensate for the lack of idlers in this area.
4.2.2.3. Center Structure
The key considerations for design the center structure are as follows:
36
-
Torsional Rigidity
Component Protection
Water Resistance
Cargo Capacity
A box structure was used to connect the two side profile assemblies. To accomplish this design we
have bolted 4 plates together, this can be view in the assembly drawing by referring to parts 01-005,
01-011, 01-012 and 01-013. A section was removed from the top plate to allow easy access to the
components inside. To maintain the structural integrity and protection, a removable plate, part 01014, was added to cover the resulting hole. This structure has a very high strength to weight ratio, it
also very good at resisting torsional motion. The fully closed structure also serves to protect sensitive
components such as the electronic circuitry.
A specific engineering requirement is the ability to carry a cargo volume of at least 96 in3. The box
structure is truncated before the end of the vehicle to provide a flat section for cargo to be secured.
4.2.3. Control
4.2.3.1. Controller – RC Controller
The key considerations for controller selection are as follows:
- Number of control channels
- Operation Range
There are five main functionalities which need to be controlled through the controller. The functions
are: panning the camera, tilting the camera, moving forward and backward, turning left and right,
and auxiliary capability. Due to these required functions, the controller needs to have a minimum of
five channels. However, expandability was discussed as a possibility so a controller was selected
which had seven channels.
A substantial engineering requirement involved the distance at which the vehicle is operable. The
design target for this requirement is 1000 feet line of sight. The controller selected has the potential
to operate at a range of 1500 feet as specified by the manufacturer.
4.2.4. Audio/Video
The key considerations for audio and video system selections are as follows:
- Range
- Quality
- Cost
The video system that was selected utilizes a high power transmitter which sends the signal from the
camera to the receiver. Many high powered video transmitters are readily available on the hobby market
which makes it a viable and sustainable option. The system selected was originally designed for use in
rocketry thus it is sufficiently rugged and meets the range requirements.
The image for the transmitter will be captured using a bullet style camera. This particular camera offers
built in IR functionality for low light situations. It is also water resistant so it does not require any
additional protection. The camera has excellent quality of 492 horizontal lines which will exceed the
engineering design target that was set at 240 horizontal lines. The cost of this camera is relatively low
compared to other high quality cameras.
37
Accompanying this system to provide audio capability will be a FRS radio. This is a highly refined
consumer product which will require no modification and the range exceeds 14 miles. The decision to
use this piece of equipment is clear especially considering it has a very low cost.
4.2.5. Power
4.2.5.1. Battery
Four Lithium-Ion Polymer battery packs were selected. The Primary drive battery has a nominal
voltage of 22.2 V to supply maximum power to the motors without exceeding the 30V rated
maximum of the motor controller. It is constructed from a 14.8 V and a 7.4 V battery pack,
connected in series. The controller and auxiliary batteries have nominal voltages of 11.1 V to be as
close as possible to the required component voltages. The energy capacities were selected to
maximize run time and minimize cost. Calculations for the projected run time for the selected
batteries are shown below.
Expected Runtime
Controller battery:
Motor battery:
Auxiliary battery:
The batteries will be charged using a 6 cell balancing charger. This will charge each cell individually
ensuring maximum charge and safe and reliable charging. Keeping the cells balanced will also
prolong the life of the batteries.
4.2.5.2. Voltage Regulation
Four voltage regulators will be implemented, two for the control unit and two for the vehicle. The
Control unit requires two output voltages, 9.6V for the RC transmitter and 12V for the LCD monitor
and audio/video receiver. The battery for the control unit will be an 11.1V LiPo pack, with a fully38
charged voltage of approximately 12.6V and a dissipated voltage of approximately 9V. The output
voltage will start above the output voltage, but eventually drop below it. Because of this, a buckboost regulator will be used. The buck-boost regulator will “buck” the input down to the necessary
output level, and will “boost” up the input to the necessary output level. The buck-boost regulator
uses a feedback loop to determine whether it needs to buck or boost the voltage.
The vehicle will also use an 11.1V LiPo pack for the auxiliary components. The camera with IR
LEDs, audio/video transmitter, and microphone require 12V for operation. As with the control unit,
a buck-boost configuration will be implemented for these components. The pan-and-tilt servos and
RC receiver will operate on 5V. Because the input voltage will always exceed the output voltage, a
simple buck regulator will be used for these components. All regulator ICs have built in current
protection.
The motor controller will be powered by a separate 22.2V LiPo pack. Due to the wide range of input
voltages that the motor controller can accept (6-30VDC), a regulator will not be necessary for this
component. The battery pack selected is 8Ah, 15C which means it is capable of supplying 120A
continuous current. (Continuous current capability = amp-hours * discharge rate). Because the motor
draw will be less than this, current limiting (which could hinder the performance of the motor
controller) will not be necessary. Instead a fuse will be added for short-circuit protection.
39
5. IMPLEMENTATION
5.1. Chassis
The chassis will be constructed of custom sheet metal machined parts. Detailed drawings for all fabricated
parts are located in APPENDIX C. All sheet metal part drawings were sent to Garmin and finished parts are
expected to arrive by January 9th, 2009. The parts received from Garmin will be formed, will have press fit
hardware installed, and will be chromated and painted black. Bearing mounts, the track tensioning system
and standoffs will be machined from aluminum stock. Material will be purchased from McMaster and the
parts will be fabricated in the Rogers Hall machine shop by the mechanical team members.
5.2. Drivetrain
The vehicle drive train will primarily consist of purchased parts. The tracks, track cogs and hubs will be
purchased from Lynxmotion. The chain and associated sprockets will be purchased from McMaster.
Implementation of the chain drive system will include some minor fabrication, as sprockets will need to be
bored to the proper size and hubs will need to be tapped to provide a solid connection between the sprockets
and hubs. This fabrication will be done in the Roger’s Hall machine shop. Once fabrication is finished the
drivetrain will be assembled with these components.
5.3. Power
Implementation of a PCB buck-boost switching power regulator will be an iterative process. Manufacturer
specifications and recommendations will be used to design the initial PCB layout and schematic. Advanced
PCB will construct the board with these documents and circuit components will be hand soldered by ECE
team members. The circuit will then be bench tested with a variable DC power supply to ensure that
acceptable voltage and current outputs are provided with inputs expected from the 11.1VDC battery pack. If
this test is passed, an additional test will be performed by wiring the circuits to the components in the
vehicle to test run time and functionality. It is not uncommon for initial PCB designs to have problems
which prevent them from functioning properly. If the results from either test are failed the circuit will be
debugged with input from the manufacturer and professors at Oregon State University. The boards will be
reordered, assembled and tested. This process will be repeated until the circuits pass both tests outlined
above.
Lithium-Polymer batteries will be used as a power source for the auxiliary and drive systems as well as the
vehicle control unit. These batteries and a load balancing charger will be purchased from All Battery.
5.4. Control
The control system of the vehicle will consist of hobby level, purchased parts. A 75MHz transmitter and
receiver will be purchased from Hobby Warehouse. This will be wired directly to the motor driver board
which is purchased from SuperDroidRobots and to the servos purchased from Lynxmotion.
5.5. Audio/video
The wireless audio and video system will consist of purchased parts from BoosterVision and
SuperDroidRobots. The camera will be attached to the pan and tilt servos and plugged into the transmitter
along with a microphone purchased from Supercircuits. The LCD will be mounted on the radio controller
and plugged into the receiver.
40
6. TESTING
7. PROJECT ETHICS
8. PROJECT SUMMARY
41
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Robotics and Automation, 2003.
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7. Lombardi, Candace. Planetary Gear. Cnet. [Online] October 28, 2008. [Cited: November 1, 2008.]
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October 15, 2008.] http://www.officer.com/web/online/Industry-Business-Wire/ReconRobotics-IntroducesRobot-W-NV-Capabilities/9$43493.
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http://www.themachinelab.com/swatbot.html.
11. Foster-Miller. The Soldier's Choice: TALONROBOTS.COM. [Online] [Cited: October 18, 2008.]
http://www/foster-miller/com/literature/documents/TALON-Brochure.pdf#talon_brochure.
12. —. TALON. [Online] October 10, 2008. [Cited: October 18, 2008.] http://en.wikipedia.org/wiki/FosterMiller_TALON.
13. Crane, David. Robo-Soldier Ready for Combat Deployment to Iraq for Urban Warfare/CI Ops. Defense
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14. University, Case Western Reserve. Department of Mechanical and Aerospace Engineering. Whegs Robots.
[Online] 2006. [Cited: October 19, 2008.] http://biorobots.cwru.edu/projects/whegs/whegs.html.
15. Mesa Robotics. Performance Specifications and Features - MATILDA II Robotic Platform. [Online]
January 31, 2006. [Cited: October 18, 2008.] http://www.mesa-robotics.com/matilda_spec.pdf.
16. Shane, L. They call him the Crusher. Stars and Stripes. [Online] [Cited: October 16, 2008.]
http://www.stripes.com/article.asp?section=104&article=60193&archive=true.
17. robosoft. robuROC 6 Technical Specifications. [Online] 2008. [Cited: October 19, 2008.]
http://www.robosoft.fr/img/data/robuROC6_web1.pdf.
18. Stability of a Multi Tracked Robot Traveling Over Steep Slopes. Shraga Shoval. New Orleans : IEEE, 2004.
19. Quansi-Static Analysis of a Leg-Wheel Hybrid Vehicle for Enhancing Stair Climbing Ability. Sathaporn
Laksanacharoen, Pattaromon Tantichattanont, Szathys Songschon. Sanya : IEEE, 2007.
20. Waldstein, M., et al. SWAT Reconnaissance Vehicle: Computer Science Capstone Project. 2007.
21. Sabertooth Dual 25A Motor Driver. Motor Control Boards. [Online] SuperDroid Robots, 2006. [Cited:
October 31, 2008.] http://www.superdroidrobots.com/shop/item.asp?itemid=822.
22. A Main Hobbies. Radios & Accesories. A Main Hobbies. [Online]
http://www.amainhobbies.com/product_info.php/products_id/12578.
42
23. Lynxmotion Inc. Robot Controllers. PS2 Robot Controller. [Online] 2008. [Cited: October 31, 2008.]
http://lynxmotion.com/Product.aspx?productID=552&CategoryID=.
24. —. Robot Controllers. Search Results. [Online] 2008. [Cited: October 31, 2008.]
http://www.lynxmotion.com/Search.aspx?txtSearch=atom.
25. Active Robots. AX500 Dual Channel Digital Motor Controller. Robot Controllers, Microcontrollers &
Development Systems. [Online] 2007. [Cited: October 31, 2008.] http://www.activerobots.com/products/motorcon/roboteq/ax500/ax500man19preliminary020907_book.pdf.
26. The Robot Marketplace. RoboteQ Speed Controllers. Electonics. [Online] 2008. [Cited: October 31,
2008.] http://www.robotmarketplace.com/products/RTQ-AX500.html.
27. Next Step Baby Monitors. Operation Guide: 2.4Ghz Wireless Remote Control Camera Kit. [Online] 2008.
[Cited: October 31, 2008.] http://www.nextstepbabymonitors.com/downloads/pan-tilt.pdf.
28. BoosterVision. BoosterVision GearCam. Wireless Video Transmitters. [Online] 2008. [Cited: October 31,
2008.] http://www.boostervision.com/cart/scripts/prodView.asp?idproduct=71.
29. RangeVideo. KX191 color and night mode CCD camera. Wireless Video Solutions. [Online] 2008. [Cited:
October 31, 2008.]
http://www.rangevideo.com/index.php?main_page=product_info&cPath=6&products_id=111.
30. BoosterVision. Mini 1 Watt Hi-Power transmitter and receiver. Wireless Video Transmitters. [Online]
2008. [Cited: October 31, 2008.] http://www.boostervision.com/cart/scripts/prodView.asp?idproduct=113.
31. RangeVideo. 2.4GHz 1000mW audio/video transmitter. Wireless Video Solutions. [Online] 2008. [Cited:
October 31, 2008.]
http://www.rangevideo.com/index.php?main_page=product_info&cPath=35_22&products_id=6.
32. Wikipedia. Decoupling Capacitor. [Online] September 20, 2008. [Cited: October 31, 2008.]
http://en.wikipedia.org/wiki/Decoupling_capacitor.
33. Advanced Battery Systems. Battery Knowledge. [Online] 2008. [Cited: October 31, 2008.]
http://www.advanced-battery.com/batteryknowledge.html.
34. RadioShack. RadioShack's On-Line Battery GuideBook. RadioShack. [Online] 2004. [Cited: November 2,
2008.] http://support.radioshack.com/support_tutorials/batteries/batgd-c01.htm.
35. Buchmann, Isidor. What is the perfect battery? [Online] 2001. [Cited: October 31, 2008.]
http://www.buchmann.ca/Article4-Page1.asp.
36. Duncan, B. Are Nickel-Metal Hydride Batteries Superior to Sealed Lead-Acid in Light Electric Vehicle
Applications? [Online] 2007. [Cited: October 31, 2008.] http://www.steveduncan.net/html/nimh_vs__sla.html.
37. Source Batteries. Battery Information. [Online] 2001. [Cited: October 31, 2008.]
http://www.sourcebatteries.com/index.php?mode=batteryinfo.
38. Quest Batteries. Comparison Applications. Harding Energy. [Online] 2004. [Cited: October 31, 2008.]
http://www.hardingenergy.com/pdfs/ComparisonofApplication.pdf.
39. All Battery. 22.2V 6000mAh 15C 90+ amp brick style. Rechargable Batteries & Battery Chargers.
[Online] 2008. [Cited: December 5, 2008.] http://www.all-battery.com/222volt6000mah15c90ampbrickstyle.aspx.
40. Lynxmotion Inc. Tracks. Lynx Motion Robotics. [Online] 2008. [Cited: 12 5, 2008.]
http://www.lynxmotion.com/Product.aspx?productID=512&CategoryID=94.
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http://www.superdroidrobots.com/shop/item.asp?itemid=871.
43
10. APPENDIX A: BILL OF MATERIALS
Part Number
Description
Cost
Quantity
Extended
Cost
Supplier
PCC182BNCT-ND
1800pF Capacitor
0.260
2
0.52
Digikey
PCC272BNCT-ND
2700pF Capacitor
0.260
2
0.52
Digikey
PCC183BGCT-ND
.018µF Capacitor
0.260
2
0.52
Digikey
PCC1833CT-ND
.027µF Capacitor
0.310
2
0.62
Digikey
PCC223BGCT-ND
.022µF Capacitor
0.099
1
0.10
Digikey
PCC1818CT-ND
.47µF Capacitor
0.200
2
0.40
Digikey
PCC2314CT-ND
1.0µF Capacitor
0.480
4
1.92
Digikey
PCF1126CT-ND
.1µF Capacitor
0.330
1
0.33
Digikey
P1.00KCCT-ND
1.00k Resistor
0.091
2
0.18
Digikey
P1.00MCCT-ND
1.00M Resistor
0.091
2
0.18
Digikey
P15.0KCCT-ND
15k Resistor
0.091
2
0.18
Digikey
P39NACT-ND
.039 Ohm Resistor
0.534
2
1.07
Digikey
490-1438-1-ND
300pF Capacitor
0.113
2
0.23
Digikey
MBRD835LT4GOSCTND
Schottky Diode
0.560
2
1.12
Digikey
B340LA-FDICT-ND
Schottky Diode
1.120
2
2.24
Digikey
RJK0305DPB00#J0CT-ND
N-Channel Mosfet
0.980
2
1.96
Digikey
P21.0KCCT-ND
21k Resistor
0.091
2
0.18
Digikey
P14.3KCCT-ND
14.3k Resistor
0.091
1
0.09
Digikey
P2.94KCCT-ND
2.94k Resistor
0.091
2
0.18
Digikey
565-3082-1-ND
33µF Capacitor
1.504
2
3.01
Digikey
P2.87KCCT-ND
2.87k Resisor
0.091
2
0.18
Digikey
P6.8KACT-ND
6.8k Resistor
0.077
2
0.15
Digikey
P4.22KCCT-ND
4.22k Resistor
0.091
2
0.18
Digikey
445-1436-1-ND
22µF Capacitor
1.386
1
1.39
Digikey
445-1385-1-ND
4.7µF Capacitor
0.264
2
0.53
Digikey
B130LAW-FDICT-ND
Schottky Diode
0.680
1
0.68
Digikey
IRLR3715ZPBFCT-ND
N-Channel Mosfet
1.100
4
4.40
Digikey
399-1255-1-ND
1.0 µF Capacitor
0.188
1
0.19
Digikey
490-1604-1-ND
160pF Capacitor
0.110
1
0.11
Digikey
490-1664-1-ND
10000pF Capacitor
0.047
2
0.09
Digikey
490-1665-1-ND
.022µF Capacitor
0.068
2
0.14
Digikey
490-1683-1-ND
.1µF Capacitor
0.074
2
0.15
Digikey
LM25575MH-ND
Buck Regulator
4.050
1
4.05
Digikey
LVK12R050FERCTND
.05 Ohm Resistor
0.380
1
0.38
Digikey
P3.09KCCT-ND
3.09k Resistor
0.091
1
0.09
Digikey
P6.98KCCT-ND
6.98k Resistor
0.091
1
0.09
Digikey
P8.66KCCT-ND
8.66k Resistor
0.091
1
0.09
Digikey
P1.0KACT-ND
1.0k Resistor
0.077
2
0.15
Digikey
P10KACT-ND
10k Resistor
0.077
1
0.08
Digikey
P1.0MACT-ND
1.0M Resistor
0.077
1
0.08
Digikey
P27KACT-ND
27k Resistor
0.077
1
0.08
Digikey
44
P3.0KACT-ND
3.0k Resistor
0.077
1
0.08
Digikey
P4.7KACT-ND
4.7k Resistor
0.077
1
0.08
Digikey
RJK0305DPB00#J0CT-ND
N-Channel Mosfet
0.980
1
0.98
Digikey
308-1433-1-ND
33µH Inductor
2.450
1
2.45
Digikey
587-1292-1-ND
2.2µF Capacitor
0.308
1
0.31
Digikey
587-1282-1-ND
.47µF Capacitor
0.110
2
0.22
Digikey
587-1284-1-ND
1.0µF Capacitor
0.121
2
0.24
Digikey
445-1426-1-ND
10µF Capacitor
0.330
1
0.33
Digikey
732-1224-1-ND
12µH Capacitor
3.320
1
3.32
Digikey
311-1127-1-ND
1000pF Capacitor
0.049
1
0.05
Digikey
311-1143-1-ND
.015µF Capacitor
0.050
1
0.05
Digikey
311-1192-1-ND
330pF Capacitor
0.058
1
0.06
Digikey
311-1194-1-ND
820pF Capacitor
0.058
1
0.06
Digikey
LM3914N-1-ND
LED Driver
2.600
2
5.20
Digikey
T93YB-200K-ND
200k Trim Potentiometer
1.250
2
2.50
Digikey
98K6373
10µF Capacitor
1.480
2
2.96
Newark
2.8k Resistor
0.060
2
0.12
Mouser
660RK73H2ATTD2801F
660RK73H2ATTD2052F
20.5k Resistor
0.060
2
0.12
Mouser
288-0805-5.9K-RC
5.9k Resistor
0.750
2
1.50
Mouser
SER2918H-223KL
22µH Inductor
5.550
1
5.55
Coilcraft
MSS1038T-823MLB
82µH Inductor
0.880
1
0.88
Coilcraft
LM5118
Buck-Boost Regulator
5.760
3
17.28
Arrow
PA3
58 dB Microphone
9.990
1
9.99
Supercircuits
N/A
Custom Regulator PCBs
33.000
4
132.00
Advanced Circuit
SDM30-12S12
12VDC-12DC Converter
34.200
1
34.20
Peak to Peak Power
BV-M1Watt
High Power Tx/Rx
169.000
1
169.00
BoosterVision
WC-029-000
7" TFT LCD Monitor
169.000
1
169.00
Superdroid Robots
DE-12
Sabertooth Motor Controller
124.990
1
124.99
Dimension Engineering
276-150
Multipurpose PC Boards
1.990
2
3.98
Radio Shack
278-1627
Heat Shrink
5.490
1
5.49
Radio Shack
N/A
Deans Ultra Plug
3.250
9
29.25
Trump's Hobbies
278-565
12AWG Wire - Red
4.990
1
4.99
Radio Shack
278-566
12AWG Wire - Black
4.990
1
4.99
Radio Shack
278-1224
22AWG Wire
6.590
1
6.59
Radio Shack
7CAP
Futaba Tx/Rx/Servos
279.990
1
279.99
Tower Hobbies
S125 1T 2BB
360-degree Servo
15.740
1
15.74
HiModel
31321
14.8V 8000mAh LiPo Battery
149.990
1
149.99
All-Battery
31119
7.4V 8000mAh LiPo Battery
81.220
1
81.22
All-Battery
31231
11.1V 4000mAh LiPo Battery
66.990
2
133.98
All-Battery
401-1304-ND
SPST Rocker Switch
0.728
2
1.46
Digikey
270-1217
20A Inline Fuse Holder
2.690
1
2.69
Radio Shack
270-1041
20 Inline Fuse 4pk
2.990
1
2.99
Radio Shack
1203
Balancing LiPo Charger
169.990
1
169.99
All-Battery
H104CRD
LED Assembly - Red
1.130
2
2.26
Bivar
45
H104CGD
LED Assembly - Green
1.130
2
2.26
Bivar
H104CYD
LED Assembly - Yellow
1.210
2
2.42
Bivar
N/A
33uF Capacitor
0.100
2
0.20
IEEE Store
N/A
100uF Capacitor
0.050
2
0.10
IEEE Store
N/A
56k Resistor
0.050
2
0.10
IEEE Store
N/A
SPST Switch
0.100
2
0.20
IEEE Store
270-1801
Enclosure
2.290
2
4.58
Radio Shack
270-1805
Enclosure
3.790
1
3.79
Radio Shack
N/A
DC Plugs
1.990
3
5.97
Goodwill
WC-044-000
IR Camera
82.000
1
82.00
Superdroid Robots
RKI-1139
1x40 Female Header
0.630
1
0.63
Robokits World
RKI-1140
1x40 Male Header
0.25
1
0.25
Robokits World
05-018
FRS radios
39.00
1
39.00
REI
01-001
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-002
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-003
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-004
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-005
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-006
.100" 5052 Aluminum, painted black
0.00
2
0.00
Garmin
01-007
.100" 5052 Aluminum, painted black
0.00
4
0.00
Garmin
01-008
.062" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-011
.062" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-012
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-013
.100" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
01-014
.062" 5052 Aluminum, painted black
0.00
1
0.00
Garmin
04-002
8-32 self clinching nut, stainless steel
0.00
0.00
Garmin
04-004
10-32 self clinching nut, stainless steel
0.00
0.00
Garmin
04-001
8-32 socket head cap screw, SS, 100 pack
5.66
2
11.32
McMaster
04-003
10-32 socket head cap screw, SS, 100 pack
8.22
1
8.22
McMaster
04-007
spring lock washer, stainless steel, 100 pack
1.74
2
3.48
McMaster
04-008
spring lock washer, stainless steel, 100 pack
2.29
1
2.29
McMaster
02-004
1/2" hexagonal bar stock, 24" length
7.34
1
7.34
McMaster
02-005
1/2" hexagonal bar stock, 24" length
7.34
1
7.34
McMaster
02-002
Delrin, 1/2" round stock, black
2.84
4
11.36
McMaster
02-001
Aluminum stock, 2" X 1" X 1', 6061 mill finish
19.84
1
19.84
McMaster
02-003
Aluminum stock, 2" X 0.25" X 12", mill finish
12.80
1
12.80
McMaster
02-006
Aluminum stock, from 02-003
0.00
0
0.00
McMaster
03-004
65" of 3" track per side
38.95
7
272.65
Lynxmotion
03-001
3" track cog
9.95
10
99.50
Lynxmotion
03-005
3" hubs, machined aluminum
14.95
5
74.75
Lynxmotion
03-006
R3 Bearing, 3/16" ID, 1/2" OD
0.00
20
0.00
Scott Zenier
03-008
#25 chain, 7', steel
22.68
1
22.68
McMaster
#25-#60 roller chain breaker, 1/4"-3/4" pitch
21.60
1
21.60
McMaster
Add and connect links, #25 chain
2.20
4
8.80
McMaster
03-009
46
03-003
22 tooth steel roller chain sprocket
7.04
4
28.16
McMaster
03-007
22mm ID, 27mm OD, flanged, 22mm length
4.38
03-002
18 tooth steel machinable sprocket
6.10
2
8.76
McMaster
2
12.20
McMaster
47
11.APPENDIX B: PART DRAWINGS
Figure 11-1 5 Volt Servo Regulator
Figure 11-2 9.6 Volt RC Controller Regulator
48
Figure 11-3 12 Volt LCD Monitor
Regulator
Figure 11-4 12 Volt Audio/Video System Regulator
49
Figure 11-5 Battery Meters
50
12.APPENDIX C: PART DRAWINGS
51