The University of Texas at ArlingtonAutonomous Vehicles
Laboratory
2011 AUVSI Student UAS Competition Journal PaperSubmitted: May
23, 2011Student TeamDaniel Glowicz, Jonathan Efinger, Mariah
Bacchus, Martin Dickson, Nicholas Yokell
FacultyDr. Atilla Dogan - Mechanical and Aerospace
EngineeringDr. Brian Huff - Industrial & Manufacturing Systems
EngineeringDr. Kamesh Subbarao - Mechanical and Aerospace
EngineeringAbstract:This paper describes a system for
semi-automated reconnaissance for the AUVSI 2011 Student UAS
Competition. An aircraft with a payload autonomously takes off and
navigates via specific GPS waypoints to a predetermined search area
where it performs a search pattern. The payload is a camera mounted
on a pan-tilt-zoom platform and it is used in searching for
targets. The location and other parameters of the target are then
identified and given to judges. Success depends on proficiently
controlling mission elements including; autonomous takeoff and
landing, autonomous control, waypoint navigation, mission
flexibility (the ability to change missions before and during
flight), and target interpretation. Discussed in this text are the
rationales, architectures, components, and processes involved in
achieving this goal. The system design is described in terms of
Project Chartering, System Requirement Review, Baseline Design,
Conceptual Design, Feasibility Studies, Preliminary Design, Unit
Testing, Detailed Design, and Integrated Testing. Additionally,
Safety features such as structural reinforcements, the ability to
switch to manual control at anytime during the flight, and
safety-specific engineering processes are addressed.
IntroductionDuring this time of the global war on terror, the
safety of the troops is of utmost concern especially in the vast,
dangerous and unknown terrains where they have to fight. Unmanned
Aerial Vehicles, from the Global Hawk to the Predator and also the
Scan Eagle, have been vital in reducing troops risks by providing a
less fatal but very effective way of obtaining reconnaissance on
their surroundings. As the years have gone by, the difficulty of
the unmanned systems missions have increased, however, so have
their technological advances. The Annual AUVSI Student Unmanned
Aerial Systems Competition, formerly known as the Student Unmanned
Aerial Vehicle competition, was created to urge students in this
technological frontier. The competition is a simulation of a
plausible US Marine UAS support mission. The mission objective is
to develop a system which can provide the Marines with information
such as locations of targets in a danger zone. An unmanned vehicle,
after a manual or automatic takeoff, will autonomously navigate
into a predefined combat zone via a given waypoint corridor. In
this combat zone, the vehicle is to find and identify targets for
the Marines. The system is required to be robust as this is a
battle zone and the situation may change at any moment and it is
vital that the system responds accordingly.The change of the
competition name to from vehicles to systems is indicative of the
degree planning necessary in meeting the mission requirements. This
report discusses the approach of the University of Texas at
Arlington (UTA) Autonomous Vehicles Laboratory (AVL), systems
design, expected performance and results as well as safety
considerations made in effort to succeed in the mission.Mission
RequirementsThe mission requirements, as specified in the
competition rules, have five major parts which are summarized in
the table below.Table 21: Key Performance Parameters (From 2011
AUVSI SUAS Rules)ParameterThresholdObjective
AutonomyDuring way point navigation and area search. All phases
of flight, including takeoff and landing
ImageryIdentify any two target characteristics: Shape Background
color Orientation Alphanumeric Alphanumeric color Identify all five
target characteristics
Target LocationDetermine target location ddd.mm.ssss within 250
ft Determine target location within 50 ft
Mission timeLess than 40 minutes total
Imagery/location/identification provided at mission conclusion 20
minutes Imagery/location/identification provided in real time
In-flight re-taskingAdd a fly to way pointAdjust search area
MethodologyIn order to successfully complete the mission, an
engineering approach was taken to address the requirements given in
the rules. The approach was to methodically design a system that
will accomplish most or all of the mission phases. The methodology
chosen is similar to the ones which top design teams use and is
shown below. Project Chartering System Requirement Review Baseline
Design Conceptual Design Feasibility Studies Preliminary Design
Detailed Design Unit Testing Integrated Testing System Tuning and
RehearsalsProject CharteringA charter for this project was issued
on August 31, 2010. This document formally authorized the teams
embarkation into the 2011 AUVSI SUAS Competition. The main purpose
of the document is to ensure that all the members of the team are
aware of the competition and the level of commitment it requires.
The document contains a project description, available resources, a
statement of work, a work breakdown structure, important AUVSI
contact information, competition milestones, the above methodology
and a project timeline.System Requirements ReviewA review session
was conducted in which the competition rules were thoroughly
analyzed in order to develop detailed system requirements and to
generate questions for clarification at the competition University
Day. The table below highlights the system requirements defined at
this meeting. The threshold level implies the bare minimum for the
system, while the objectives are the goals and the stretch
objectives are bonus for the system.Table 51: System Requirement
SummaryCapability LevelCapability
ThresholdAdd a fly-to waypoint
ThresholdChange altitude while in automatic mode
ThresholdChange airspeed while in automatic mode
ThresholdAutomatically fly waypoints
ThresholdAutomatically fly search area
ThresholdView 60 degrees in every direction vertically below the
air vehicle
ThresholdPrint 2/5 target characteristics at conclusion
ThresholdPrint target location within 250 at conclusion
ThresholdConclude within 40 minutes
ThresholdAddress Safety issues
ObjectiveAutomatically take off
ObjectiveAdjust the search area and display the changes
ObjectiveDisplay/Print 2/5 target characteristics during
flight
ObjectiveDisplay/Print 5/5 target characteristics during
flight
ObjectiveDisplay/Print target location within 250 during
flight
ObjectiveDisplay/Print target location within 50 during
flight
ObjectiveAutomatically land
ObjectivePrint 5/5 target characteristics at mission
conclusion
ObjectivePrint target location within 50 at mission
conclusion
ObjectiveConclude at 20 minutes
StretchPrint 4/5 enroute-off-flight-path target info at mission
conclusion
StretchDisplay new search area (for Pop Up target) during
flight
StretchPrint Pop Up target image & location within 250 at
mission conclusion
StretchAutomatically id/cue >= 2 targets with >= 50%
correct
StretchJAUS Compliance
Baseline DesignThe baseline design phase was an opportunity for
team members to come up with open ended creative ideas for solving
the design problem. The ideas proposed were diverse varying from
unconventional aircrafts such as a tilt rotor to a simple
modification of a conventional aircraft. The decisions made in this
phase were twofold: Selecting an aircraft and Selecting an auto
controllerA figure of merit system is used in explaining how these
decisions were made. The figures of merit for air vehicle selection
and auto controller selection are shown below. Each merit was given
a weight factor (on a scale of 1 to 5) in order to amplify its
importance. The grading scheme is as follows Strong point: 1
Indifference or unknown: 0 Weakness: -1The table below shows the
figure of merit for aircraft selection.Table 61: Air Vehicle Figure
of MeritsMeritsW. F.BlimpFixed Wing PropTilt rotorHelicopterFixed
Wing Jet
Payload Volume to vehicle weight ratio4-11 1 -11
Cost of parts4-10 -1-1-1
Legacy30 1 0 0 0
Ease of implementation3-11 -1-10
Compatibility with auto Controller50 1 -10 0
Speed3-11 1 -11
Maneuverability in search Area31 0 1 1 -1
Piloting experience50 1 -10 -1
Product Total-1123 -7-11-5
A conventional fixed-wing propeller-driven aircraft was chosen
because it has the least unknowns, it is easy to implement,
favorable to most auto controllers and the most familiar to the
safety pilot, hence the safest choice. The table below shows the
FOM for the auto controllers. Table 62: Vehicle Configuration
Figure of MeritsMeritsW. F.MicroPilotPiccoloKestrelStargate
Cost41 -1-11
Experience with it51 0 0 -1
Package41 1 1 0
Accessibility31 0 0 -1
Flexibility30 0 1 1
Meets all autonomous objectives51 1 0 -1
Product Total21 5 3 -6
The MicroPilot solution was chosen because it was the most cost
effective choice as the team already possesses two systems.
Additionally, the team has about five years of experience with
MicroPilot and has performed well in two UAV competitions using
it.Conceptual Design and Feasibility StudiesSince a decision had
been made on the autonomous flight system, the conceptual design
phase was spent in creating different set-ups for meeting the
imagining requirements. The candidate designs were as follows.
Fixed Wide-Angle (120 FOV) High Definition Camera Gimbaled Camera
Stabilized by MP board Gimbaled Camera controlled by a processor
programmed by the team Multiple Fixed Cameras with a Video
MultiplexerThe Feasibility of each these options were determined
and a decision on a design concept to move forward with was made
using the figure of merits table shown below.Table 71: Conceptual
Design Figure of MeritsMeritsW. F.Single Fixed CamMP Stabilized
CameraIn House Stabilized CameraMultiple Fixed Cameras
Overall Risk31 0 -1-1
Incremental Development41 0 -1-1
Reliability41 0 0 -1
Available Resources 30 0 0 -1
Our Experience 41 1 -1-1
HW Complexity 31 0 -1-1
Weight4-11 -1-1
Cost4-10 0 -1
Flexibility4-11 1 1
Ingenuity2-11 1 1
Product Total4 14 -12-23
The gimbaled camera stabilized by the MicroPilot design was
chosen because it eliminates the need for a heavy wide angle lens
yet gives the ability to see sixty degrees in all the directions
below the aircraft. Additionally, a stabilized camera means that
the camera can move independently of the aircrafts rotations. Since
MicroPilot does the stabilization there will be no need for an
extra processor, its complexity and all the sensors and
communication devices that it will require.Preliminary DesignDuring
this phase, a general idea all the components going into the system
were determined. The premise was that a fixed wing aircraft
controlled by the MicroPilot carries a stabilized gimbaled camera
which sends live video to the ground. On the ground, there is a
Ground Control Station for the MicroPilot and an imaging station
for viewing the video. An image processing station was also added
in this phase. This station was added in order to initiate work by
the team on autonomous image recognition. A diagram of this system
is shown below.
Imaging Station Pilot Aircraft ServosSafety SwitchSwitchRadio
ModemR/C RXVideo TXGround Control Station
GroundControlStationRadio ModemTeam LiaisonJudgesVideo RX
Imaging LaptopR/C TXData LinkAirAutonomous Imaging
ProcessingJoystickLeft AileronRight
AileronElevatorRudderThrottleRollPitchStabilizedMountGround
GroundMicroPilotVideo LinkOEM Camera
Figure 81: System diagramThe overall system can be divided into
the airframe, radio control, autonomous control, imaging,
communication and power subsystems.Airframe SubsystemThe R/C
aircraft chosen is a SIG Kadet Senior ARF (Almost Ready to Fly)
equipped with an O.S. FX 0.91 in3 engine. The Kadet Senior is a
stable fixed-wing airplane with a large wing area and sufficient
payload space. Additionally, since it is an ARF it has a short
build time. The OS FX 0.91 in3 is a powerful, reliable and easy to
maintain engine with a top output of 2.8 hp. The airframe is
equipped with HS-81MG servos for the throttle, HS 645MG for rudder
and HS-645BB servos for the other surfaces, all of which are very
durable and reliable. Additionally, a few modifications were made
to make the airframe more ergonomic. Modifications such as
Reinforcement of the firewall to withstand stresses from the more
powerful engine. Relocation of the throttle, rudder and elevator
servos to increase payload space. Creation of panel hatches for
easy access to the batteries, payload and servos. Replacement of
stock main landing gear with composite to improve take-off and
landing stability.A three view of the airframe with dimensions and
tables of its characteristics and that of the engine are shown
below.
Figure 82: Three-view drawing of the SIG Kadet Senior (picture
from ARF Manual)
Journal Article: 2011 AUVSI Student UAS Competition
University of Texas at Arlington Autonomous Vehicles Lab Page 1
of 20Table 81: Airframe CharacteristicsAspect Ratio5.07
Wing Area (ft2)7.92
Wing Span (ft)6.33
W/S (lb/ft2)0.66
Fuselage Length (ft)5.33
Fuselage Width (ft)0.42
Weight Take-Off (lbs)12
Weight Landing (lbs)11.5
Table 82: Engine SpecificationsEngine Model.91 FX (OSMG0591)
Displacement (cu in)0.912
Bore (in)1.091
Stroke (in)0.976
RPM2,000 -16,000
Output (hp @ rpm)2.80 @ 15,000
Weight (oz)19.42
Recommended Props15x8, 16x6
Radio Control SubsystemThe R/C Subsystem is the subsystem used
for manual control of the aircraft. The subsystem includes an R/C
Transmitter, R/C receiver, a safety switch and a glitch buster. A
diagram of the subsystem is shown below.
Figure 83: Radio Control Subsystem diagramGlitch Buster:The
glitch buster is a device made by Jomar electronics which amplifies
and cleans servo input signals and provides servo power isolation.
It has 8 input and output channels and weighs about an ounce. It
was implemented as a safety measure to ensure that the servos
receive clean strong signals at all times because there are a lot
of signal wire splits in the system. A picture of the Glitch buster
board is shown below.
Figure 84: Jomar Electronics Glitch buster (from
http://www.emsjomar.com/)Safety Switch:The safety switch is a
custom-built device created by Reactive Technologies10 in
collaboration with NCSU11. It receives inputs from both the R/C
receiver and the MicroPilot and it outputs signals from either of
them to the glitch buster. The switch is controlled by an input
channel from the R/C Receiver that allows the pilot to select which
set of inputs is to be sent to the aircraft servos. The pilot can
manually bypass the auto controller during emergencies by switching
control directly to the R/C receiver. It has an added feature that
in a case where the aircraft losses signal from the pilots
transmitter, the switch automatically turns control to the R/C
receiver which is preprogrammed to initiate a
cut-throttle-spiral-to-the-ground maneuver. This is a fail-safe
maneuver implemented in compliance with the AUVSI competition
rules. A picture of the reactive technologies safety switch is
shown below.
Figure 85: Reactive Technologies Safety Switch (from
http://www.reactivetechnologies.com/RxMux.html)R/C Receiver:The
purpose of an R/C receiver is to allow the pilot to control the
aircraft. It relays the signals from the pilots transmitter to the
aircraft. It is connected to both the auto controller and the
safety switch. Under normal conditions, the pilot can fly the
aircraft through the auto controller via the receiver. However in
an emergency, the pilot can take direct control of the aircraft by
sending a signal to the safety switch. The R/C receiver selected
for this UAS is a synthesized Multiplex IPD 9 channel RX. This
receiver was chosen because it is synthesized and can run on almost
any R/C frequency. Additionally it can be programmed to initiate a
fail-safe maneuver if the aircraft losses signal from the pilots
transmitter.
Figure 86: R/C Receiver (from
http://www.multiplexusa.com/)Pilots R/C Transmitter:The pilots
transmitter is the means by which the pilot can control the
airplane. This transmitter sends signals to the air vehicles
receiver, allowing the pilot to fly either via the auto controller
or directly through the safety switch. The transmitter chosen is a
Multiplex Royal EVO 9 channel TX equipped with a frequency scanner.
It is reliable, durable and versatile. It is versatile in the sense
that it allows the pilot to assign any of its switches to any of
its channels. The frequency scanner allows the transmitter to check
for dirty or in-use R/C frequencies. This gives added safety
because the transmitter will be inactive if a channel is dirty and
the UAV will not fly if the transmitter is inactive (see safety
switch section).
Figure 87: R/C Transmitter (from
http://www.multiplexusa.com/)The roles of a pilot are summarized
below: Ensure the auto controller flies the aircraft in a regular
manner. Update the team and the liaison on any irregularities
during the course of the mission Take control of the aircraft if
there is a major malfunctionAutonomous Control SubsystemThe auto
controller chosen is the MicroPilot MP2028g. It was chosen during
the baseline design phase because the team is familiar with the
system and it meets design requirements. It is capable of altitude
hold, airspeed hold, coordinated turns and GPS navigation as well
as autonomous take-off and landing. It is also able to stabilize a
gimbaled camera to compensate for the aircrafts rotations.
Additionally, it produces sufficient telemetry data which can be
transmitted via a modem link or overlaid unto a video as needed.
The Autonomous subsystem comprises of the MP2028g board, its
sensors and Ground Control Station softwareMP2028g Board:The
MP2028g is the base of the autonomous control subsystem. It is
where all the flight parameters are stored including airplane
characteristics and the current flight plan. It weighs only 1 oz
and measures 3.9 inch by 1.5 inch. It comes equipped with two
pressure transducers, X-Y gyros and a GPS unit. One of its pressure
transducers is open to ambient air for altitude measurements while
the other is connected to a stagnation pressure tube for airspeed
measurements. A layout of the MP 2028 board is shown below.
Figure 88: MP2028g Layout (from Micropilot manual)From the
sensor data, the board determines the required action in order to
achieve a desired flight condition. The actual magnitude of the
commands MP2028g issues to the aircraft servos are governed
Proportional-Integral-Derivative (PID) control loops which are
tuned to the specific airframe. It uses 12 PID loops which are:1.
Aileron from Desired Roll2. Elevator from Desired Pitch3. Rudder
from Y-accelerometer 4. Rudder from Heading 5. Throttle from Speed
6. Throttle from Glide Slope 7. Pitch from Altitude8. Pitch from
AGL Altitude9. Pitch from Airspeed Altitude10. Roll from Heading
11. Heading from Cross Track12. Pitch from DescentGround Control
Station (GCS) Horizon Software:The GCS software that comes with the
MicroPilot is called HORIZONmp. Horizon displays information in a
Graphics User Interface (GUI) and allows the operator to monitor as
well as dynamically change flight parameters. It is also used to
upload aircraft parameters and flight plans to the auto controller.
A screenshot of the GCS Horizon Software GUI is shown below.
Figure 89: A screen shot of the GCS HORIZON Software GUIThe GCS
also has a window which displays the cameras projection and gives
the camera center location in UTM coordinates. A picture of this
widow is shown below.
Figure 810: A screen shot of the Camera Status window showing
camera center locationImaging SubsystemThe imaging subsystem is the
system used to identify targets. It is comprised of a roll-pitch
gimbaled camera, Image viewing and an Image processing station and
components of the autonomous subsystem such as the MicroPilot and
GCS. A diagram of the imaging subsystem is shown below.
Figure 811: Imaging subsystem diagramRoll-Pitch Stabilized
Gimbaled Camera:The aircraft carries a gimbaled camera for
capturing in-flight video used in target search and recognition.
The camera rotates about the roll and pitch directions with respect
to the aircraft. The rotations are controlled by servos connected
to the MicroPilot which makes them compensate for the planes
rotations. The camera used is a Sony FCB color OEM camera. It was
selected because it is light, has high quality images and a serial
interface which allows zoom (26x) control. Zoom control has not
been implemented at the time of writing this report; however, it is
in the works. A picture of the camera in the gimbaled mount is
shown below.
Figure 812: Roll-Pitch gimbaled cameraImage Viewing Station:The
image viewing station is where the Camera Operator works. The
Camera Operator uses a joystick to control the camera via the GCS.
The operator is responsible for finding targets and alerts others
about it.Autonomous Image Processing Station:This is a computer
dedicated solely to autonomous imaging. A simultaneous video feed
is sent to the laptop which is running a program written using
OpenCV. The program autonomously detects shapes and their colors.
The pictures below show the software detecting triangles.
Figure 813: Pictures of triangles automatically detected by the
imaging programCommunication SubsystemThe communication subsystem
is the means by which the ground subsystems communicate with those
in the air. This subsystem has two components: a two-way data link
and a video link. The data link is via two 900 Hz MaxStream Xtend
radio modems while the video link is through a 2.4 GHz Black Widow
Audio/Video transmitter and a diversity receiver.
Figure 814: Radio Modem, Video Transmitter and Diversity
ReceiverPower SubsystemA schematic of the power distribution is
shown below. Lithium Polymer batteries were chosen because they are
light weight (1.1lbs total) and have high current capacities. The
master switch is a safety precaution to ensure that all the
batteries are turned off when they are supposed to be.
Figure 815: Power distribution schematicUnit TestingAll the
subsystems were tested individually to ensure they work as expected
and in the cases where they did not, the subsystems were redesigned
to do so. R/C and autonomous flights were performed, the camera
stabilization system was bench tested and the communication links
were proven to work.Detailed DesignDuring this phase of the process
the interconnections between the subsystems were designed as well
as their placements. Consideration was also given to the methods in
which the system as a whole is used to perform the mission. The
designs are described in the following sections.Aircraft LayoutEach
subsystem in the airframe was carefully grouped and some were
mounted in metal boxes and then placed in various sections of the
aircraft with weight/balance and RF interference considerations.
Since some of the systems are connected via multiple wires Alden
Pulse Lock connectors were used to connect between them. These
connectors are lightweight and provide secure connections which are
quick to release. The pictures below show some of the grouped
subsystems.
Figure 101: Power, autonomous and R/C subsystems and an Alden
PL700 connectorTarget Search Pattern and Target identification
ProcedureA search needs to be performed that will maximize the use
of the gimbaled camera and MicroPilots capabilities in
accomplishing the mission. A figure of the selected search pattern
is shown in Figure 102 below. It involves the camera operator
performing a sweep while the aircraft performs a back-and-forth
pattern in and out of the search area. Upon target discovery the
GCS operator initiates either a right or left orbit depending on
the location of the target. After the target is identified the
aircraft returns to its original path. The full target
identification process is described in two sections: the Operators
loop and the Target editors loop. The operators are the GCS and
Imaging Station operators while the Target editor is in charge of
determining the image parameters and filling out the Real Time
Actionable Intelligence Forms (RTAIF) and Mission report.
Figure 102: Target Search PatternOperator Loop:1. While manually
steering & zooming the camera searching for targets, the Camera
Operator sees a target on his real-time video computer screen.2.
The Camera Operator loudly says I see a target on the left (or
right).3. The Horizon Operator commands the GCS to orbit the
airplane to the left or right, depending on the side stated by the
Camera Operator.4. While the airplane orbits, the Camera Operator
attempts to compose a good image of the target.5. When the Camera
Operator composes a satisfactory image of the target, he says out
loud Acquire target! and maintains the composition. 6. When hearing
Acquire target! the Target Editor reaches over & presses the
PrtSc button on the Camera Operators computer.7. The Camera
Operators computer spools the print job without further manual
intervention.8. The Horizon Operator, upon hearing the Camera
Operator say Acquire target! selects the Horizon Camera Status
Window and presses the Alt-PrtSc key combination.9. The Horizon
Operators computer spools the print job without further manual
intervention.10. The Horizon Operator then commands the airplane to
resume its flight plan. 11. This process is repeated until the
entire search area is covered.Target Editors Loop:1. The printer
prints the Camera Operators image.2. The printer prints the Horizon
Operators Camera Status window.3. The Target Editor gets both
hardcopies from the printer.4. The Target Editor gets a blank
Real-Time Actionable Intelligence Form (RTAIF).5. The Target Editor
transcribes the CAM Center Hdg(deg.), UTM zone, Easting, &
Northing numbers into a custom Excel worksheet.6. The Excel
worksheet computes the latitude & longitude of where the
cameras boresight intersects the ground.7. The Target Editor
transcribes the computed latitude & longitude to the RTAIF.8.
The Target Editor looks at the hardcopy target image and fills in
as many of the RTAIF fields as reasonably possible.9. If time
allows, the Target Editor estimates the direction of true north on
the hardcopy of the target.10. If time allows, the Target Editor
estimates the orientation of the target with respect to the eight
cardinal compass directions relative to the true north direction he
drew on the hardcopy.11. If time allows, the Target Editor adds the
target orientation to the RTAIF.12. The Target Editor gives the
completed RTAIF to the judge & announces This is real-time
actionable intelligence, Sir!13. This process is repeated until the
all the targets are handed to the judgesIntegration
TestingIntegration testing is the phase where the fully integrated
system as well as the methods described in the detailed design
section is to be tested and timed. Due to unforeseen circumstances,
no integrated testing has been done at the time of creation of this
document.Safety FeaturesSafety is an important part of engineering
design. A lot of thought and planning has to go into ensuring that
personnel, equipment, and software are well-protected before,
during and after the missions. In this project, safety was stressed
from the beginning and was emphasized through the daily operation
of the equipment in the Autonomous Vehicles Laboratory. It was
standard practice to use checklists and other means in order to
prevent or minimize the chance of injury. Some of the Standard
Operating Procedures (SOP) for safety are characterized below under
Procedures for Accident Avoidance, Hardware Handling and Safety
Devices.Procedures for Accident AvoidanceThe general operation
guidelines are: Checklists are used for procedures such as charging
batteries to reduce the risk of damage The airplane must be
de-fueled after each flight. Two team members are involved in the
starting of the airplanes engine. One secures the plane while the
other starts the engine. Prior to each flight, the transmitter and
receiver range checks are performed according to the manufacturers
suggested procedure. All flights are conducted using a skilled
pilot covered by AMA insurance. No spectators or operators are
allowed to stand in front or to the side of a rotating propeller.
All team members must remain behind the airplane while the engine
is on. All autonomous fine-tuning flights are conducted at a
minimum altitude of 500 ft. This altitude provides enough time to
safely transition from autonomous to manual flight in case of an
emergency. Also, in the event of an engine failure, the
conservative altitude provides the pilot with a better chance of
recovery.Hardware Handling The tips of the propeller are painted
white so that its boundary is visible at all times while in
rotation. All battery charging ports and switches are placed inside
hatches on the top aft of the fuselage, away from the engines
exhaust in order to prevent possible short-circuiting due to fuel
or oil ingestion. The Lithium-Polymer batteries are charged outside
the aircraft. This is done in order to prevent improper charging
which could result in fire or a possible explosion. The master
switch is turned off before the aircraft is loaded for
transportation Fuel is stored in a fireproof cabinet and never left
unattended to or under the direct heat of the sun. All batteries
onboard the aircraft are checked for proper charge prior to each
takeoff in order to prevent loss of control or communication during
flight due to insufficient battery charge. All software files and
programs pertinent to the autonomous project including the
operating system of the ground station are backed up and saved.
This gives the ability to retrieve the information in case of loss
or damage of the original oneSafety Devices Glitch Buster See
Section 8.2.1 for more details Safety Switch See Section 8.2.2 for
more details Frequency Scanner See Section 8.2.4 for more details
Master Switch See Section 8.6 for more detailsConclusionMany
considerations must go into the design of an autonomous aerial
system, from aerodynamics and structures to electronics and
communications. This paper has briefly described the University of
Texas at Arlingtons Autonomous Vehicles Labs UAS. It described the
process by which the air vehicle was selected, the suite of
electronics chosen to be integrated, the tuning of the autonomous
system and the modifications that took place on the airframe in
preparation for the AUVSI 2011 Student UAS Competition. The design
phases were Project Chartering, System Requirement Review, Baseline
Design, Conceptual Design, Feasibility Studies, Preliminary Design,
Unit Testing, Detailed Design, and Integrated Testing. Safety was
also paramount. The participating students had to become familiar
and fully aware to the associated risks of dealing with flammables,
internal combustion engines and propellers. Safety compliance was
addressed with safety devices, procedure checklists and constant
reinforcement of situational awareness. From the content of this
document, the UTA AVL is confident that its UAS is capable of
achieving the performance goals of the 2011 AUVSI Student UAS
Competition.AcknowledgementsWe would like to thank the MicroPilot
Company for their contributions in technical support and product
discounts. Additional thanks goes to Multiplex giving the team a
wonderful deal on their radios and other electronics. Special
gratitude goes to Jay Francis from Reactive Technologies for
developing and donating two of his bypass boards to the
AVL.References1. MicroPilot, MP2028g - Autopilot.2005,
http://www.micropilot.com/Manual-MP2028.pdf2. MicroPilot, HORIZONmp
User Guide.2004.3. MicroPilot, Working with radio modems. 2005.4.
MaxStream, Xtend Wireless OEM RF Module.
2006.http://maxstream.net/products/xtend/product-manual_XTend_PKG-R_rs-232-rs-485-RF-Modem.pdf5.
O.S. Engines, 61FX Owners Instruction Manual. 2001.6. SIG, Kadet
Senior ARF Assembly Manual. 2002.7. Multiplex, Royal EVO
Instructions. 2002.8. Multiplex, Operating Instructions RX-9 /
RX-12 SYNTH DS IPD receivers.9. Ublox TIM-LP Product Summary
http://www.u-blox.com/products/Product_Summaries/TIM-LP_Prod_Summary(GPS.G3-MS3-02028).pd10.
Reactive Technologies- James T. Francis.11. North Carolina State
University- Dan Edwards.12. EMS Jomar,
http://www.emsjomar.com/SearchResult.aspx?CategoryID=4 , 200613.
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