Istanbul Technical
University
Unmanned Aerial
Quadrotor System
for the 2014 AUVSI UAS Student Competition
By
Onur Esmercan, Efe Ballı, Saim Can Bakır, Erhan Koçyiğit, Halil Kayıkcı, Dilara Kurt, Enes
Aytekin, Süleyman Sümertaş, Ertuğrul Çinar, Fatmanur Şirin, Gökçe Vural ,Selin Bulut
Faculty Advisor: Prof. Dr. M. Adil Yükselen
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Table of Contents
1. INTRODUCTION ............................................................................................................. 3
1.1. Team
................................................................................................................. 3
1.2. Mission Requirements ................................................................................................. 3
1.3. Mission Tasks ............................................................................................................. 3
1.3.1. Flight over Waypoints ........................................................................................ 3
1.3.2. Area Search ......................................................................................................... 3
1.3.3. Emergent Target ................................................................................................. 4
1.3.4. SRIC ................................................................................................................... 4
2. AIRFRAME ....................................................................................................................... 4
2.1. Frame ........................................................................................................................... 4
2.2. Motor............................................................................................................................ 5
2.3. ESC .............................................................................................................................. 5
2.4. Cable ............................................................................................................................ 5
2.5. Propeller ....................................................................................................................... 5
2.6. Battery .......................................................................................................................... 6
3. FLIGHT CONTROL SYSTEM ....................................................................................... 6
3.1. Main Controller ............................................................................................................ 7
3.2. GPS-Compass Pro Module .......................................................................................... 7
3.3. IMU .............................................................................................................................. 8
3.4. PMU ............................................................................................................................. 8
3.5. Led ............................................................................................................................... 8
4. PAYLOAD ......................................................................................................................... 9
4.1. Choice of Camera & Gimbal
............................................................................. 9
4.2. Target Recognition ....................................................................................................... 9
5. IMAGING & GROUND CONTROL ............................................................................. 11
5.1. Ground Control Station ............................................................................................. 11
5.2. Mission Planning ....................................................................................................... 11
6. TESTING .......................................................................................................................... 12
6.1. Checklist..................................................................................................................... 12
6.2. Mission Risks & Contingency Plans .......................................................................... 13
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1. INTRODUCTION
1.1. TEAM
The ITU Multicopter Team was established in 2012 to do research on multi-rotor air
vehicles. After research, design and testing, the team has established the Student UAS
competition as its target.
The team leader Onur Esmercan handles the administrative and paperwork and is
responsible with the performance of the whole system. The team is divided into squads,
dealing with various tasks, them being Umut Erhan Koçyiğit working on software and ground
control, Halil Kayıkçı, Dilara Kurt, and Enes Aytekin working on the frame, engines and
propellers, Efe Ballı working on the camera and gimbal, and Fatmanur Şirin and Süleyman
Sümertaş working on image processing.
1.2. MISSION REQUIREMENT ANALYSIS
We have chosen to do all secondary missions except for IR target detection and off-axis
target detection. The take-off and landing will be done manually for safety purposes but
autonomous take-off and landing capabilities will be retained. As per the regulations, the pilot
will be ready to take control over the autopilot at all times. The waypoints for the first mission
will be entered to the mission planner beforehand, but editing and adding waypoints will be
trivial.
There are two failsafe systems on board. The first one is return home, the aircraft will
return to the launch location and try to reacquire the signal from the GCS. The other is
throttle-off, the system will cut throttle if there are any malfunctions on the craft. The aircraft
will hit the ground approximately 7 seconds after throttle-cut, when flying at 750 ft AGL
(maximum allowable altitude). The aircraft will have lateral travel of no more than 100 metres
if flying at maximum speed at maximum allowable altitude.
1.3. Tasks
1.3.1. Flight over Waypoints
The aircraft will fly over the waypoints at maximum speed, which is around 35 km/h
(20 knots) indicated. The flight wll be continuously monitored visually by the pilot and
through the GCS by the operators. The interface will display the position of the craft relative
to the map and the entered waypoints in 3D. The interface allows the GCS operators to add or
edit the waypoints easily.
1.3.2. Area Search
After flying through waypoints, the aircraft will start flying a search pattern over the
search area. The video feed will be monitored manually, and screenshots will be taken when a
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target gets into the image. The images will be sent to the computer for enhancement and
processing, and the targets will be identified. The screenshots, in other words target
acquisition will be done manually, but the process is automated after that point. The image
will be linked to the craft’s position at that time.
1.3.3. Emergent Target
After receiving the location of the emergent target, a search pattern will be constructed
over the given area and the video feed will be monitored manually. A screenshot will be taken
when the target is found, along with is location and description.
1.3.4. SRIC
When the location of the SRIC antenna is broadcast, the craft will move to the general
location of the antenna and the signal will be acquired by the onboard modem. The data will
be viewed at the GCS and the given task will be carried out. The pilot may take over the
controls for the task, if needed.
2. AIRFRAME (STRUCTURE)
After trials with quad- and hexacopters, we have elected to use an octocopter frame
to have the best balance of load carrying and efficiency. In order to have the motors working
at the same speed, that is, as slow as possible, the center of gravity must be right at the center.
If the CG moves to one side, the engine(s) at that side will have to turn faster, decreasing
propeller efficiency and consuming valuable energy.
Because of the long flight we will take from Turkey, the frame must be easily disassembled
and reassembled.
2.1. FRAME
Frame must be strong for unwanted landings or small crashes. On the other hand, for the
best battery usage, frame must be lightweight. Because of these reasons we have chosen a
carbon fiber and aluminum mixture octocopter frame. Its total weight is 885gr (only frame).
Frame with ESC and motors weigh approximately 2125 gr. Tricopters and quadrocopters have
maneuverability more than hexacopters and octocopters. However, multicopters which have
more than 4 propellers have more lifting ability than tricopter or quadrocopters.
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One of the advantages of octocopter is that it can fly even one missing or broken
propeller. Because of the payload amount the chosen multicopters must have large payload
capacity.
Diameter of the frame = 885mm (without propellers)
2.2. MOTOR
The most important part of propulsion system of
multicopter is motor. Our octocopter has T-Motor
MT2814-10 type brushless motor. The total thrust will be
14400g.Each motor has 120g weight and total weight of
motors is 960g. This is an out-runner motor. This kind of
motors are highly efficient for UAVs.
2.3. ESC (Electronic Speed Controllers)
Optimal ESC for our motor and battery combination on the octocopter is 40 A TMotor 400 Hz ESC BEC.
2.4. CABLE
Total =
Motor +
ESC +
Battery + Propeller +
Cable
Cables on the octocopter seems like very simple. However, for the optimal efficiency
cables have most significant role on the multicopters. Total efficiency equals to motor, ESC
(Electronic Speed Controller), battery and propeller efficiency. But these efficiency ratios
depend on efficiency of cables. No matter how motors, ESCs, propellers or batteries are good,
if cable system is not efficient, then the multicopter will not be efficient. Avoid this situation,
cables must be chosen very carefully. Choice of cables depends on weight, thickness, length,
material, the ratio of substance of cables, coating materials of cables and the final is solder.
According to all criterions we have chosen GS 16 AWG Silicone Cable Ultimate 259
Stranded.
2.5. PROPELLER
The multicopter system contain 12’’ by 4.5‘’ propellers
each of which is weight of 11g. The multicopter's working
principle is associated with impulse that occur owing to
the rotation of propellers. Some of them have to turn left
while the others turn right in order to remove the
centrifugal force. The other issue about our design is
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propeller balancing which lead to vibration and unstable flight. The problem disappear owing
to the propeller balancer and so vibration free multicopter will fly better and longer.
2.6. Battery
We will use two 4400 mAh, 14.8 V lithium-ion polymer batteries made by Gens. The
motor/propeller configuration we have selected has the greatest efficiency at around 15 V, so
having a 4S, 14.8V battery is the best compromise. Lithium-polymer batteries currently have
the best energy-to-weight ratio and are compact enough for our applications, so they were the
obvious choice for power on board the aircraft.
Lipo safety

Use fire resistant containers while storaging and charging.

While charging battery, you should not leave it.

Balance cells of battery in several cycles.

Be sure of that you are considering recommended charge and discharge limits.

Do not use water while putting out burning battery.

After crash, first remove the battery connection from vehicle.
3. FLIGHT CONTROL SYSTEM
The team ITU MULTICOPTER choose to use a commercial otopilot system to
supply(effective) stabile for the UAV’s autonomous flight. The various autopilot systems
(was tried) have been tried such as a homemade autopilot associated with Arduino, Ardupilot
2.5 Mega and some kind of DJI models. At the end of trying these models we prefer to set DJI
A2 flight controller on our multirotor. The DJI A2 provides more precise position hold in
more extreme air conditions with developed IMU and GPS module unlike APM or others.
The higher accuracy of the GPS is complemented with the enhanced anti-vibration
characteristics in the flight controllers IMU. These kind of properties is separating the A2
with the other experimented autopilot systems.
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3.1. Main controller
All saved datas inside of main controller, it manages A2’s reactions with inputs that
comes from IMU and GPS. The flight controller keeps your multi-rotor stable while you are
flying in manual mode, and can take over to fly to 3D waypoints when you fly in autonomous
mode.The important thing is that the main controller includes built-in receiver.
3.2. GPS-Compass Pro Module
The GPS receiver of the A2 GPS-Compass Pro Module is equipped with a new high gain and
high performance right-handed circular polarized (RHCP) antenna, the low noise antiinterference front-end RF design and the optimized localization algorithm, which provides the
GPS Pro with stronger anti-interference performance, a stronger ability to capture satellite
signals and a more accurate position hold calculating ability. All these features have enhanced
its position locking capability.
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3.3. IMU
The interior sensor of the A2 IMU has been upgraded comprehensively, and with
higher accuracy performance, larger measuring range, and a unique damping design and
calibration algorithm, the IMU is able to provide stable output even with high vibration and a
large movement environment.
3.4. PMU
The PMU detects voltage permanently and alerts in unexpected situations. It also has
an extendable CAN BUS port.
3.5. LED
Equipped with an LED Bluetooth indicator adjusting parameters conveniently.
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4. PAYLOAD
4.1. Choice of Camera & Gimbal
We have elected to use the Foxtech FH10Z camera with 4X optical zoom. When a target
is found, the craft will zoom in to the target and have a better picture of the target for
recognition. We were originally planning to use a GoPro camera system but its image quality
proved to be unsatisfactory. Also the ultra-wide field of view required extra optics to reduce
the image to a narrower FOV. At the other end, we evaluated an SLR camera, but the
necessity of a video feed and the SLR camera's weight led us to eliminate it from the shortlist.
Evaluation of a handheld video camera also yielded unsatisfactory images and also it proved
difficult to control and receive video from. Therefore we turned to a camera designed for
flight, the Foxtech camera which is designed as an FPV camera.
We have chosen to construct a 3-axis gimbal to carry the camera as ready-made gimbals
were either too light (built for the likes of GoPro) or too heavy(built for SLR cameras and the
like). We have used predominantly carbon fiber on the structure and utilized brushless motors
for the gimbal pivots. The gimbal has a movement of +10/-90 degrees in azimuth, +60/-60
degrees in tilt and +90/-90 degrees in pan. The landing gear is in the image at around ±30
degrees of pan, at 1X zoom.
4.2. Target Detection
Overview:
Basically, image processing will follow these steps.

Following the taken video on the ground station.

Noticing some discrepancies on the display screen.

By using screenshots, these different displays will be got to the GS.

Processing the image with the preformed codes and algorithms.
Image Tracking:
DJI AVL58 5.8GHz Video Link Kit provides to watch video that the shooted by camera
on the craft as live for a long range.
Display will be followed by ground station as manual.
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Any discrepancies on the screen will be taken to the GS so that image can be processe
Image Processing:
After ground station gets the photos as JPG type, image processing will start and follow
some steps.Noise reduction.


Image enhancement.
Zooming the target by using interpolation.
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5. IMAGING AND GROUND CONTROL SYSTEM
5.1. Ground Control System
Google 3D Maps
Ground Station designed around intuitive Google 3D map offering GIS(Geographic
Informations System) data. We can operate and plan flight routes anywhere, using mouse to
zoom in/out of 3D Maps which can be downloaded to PC.
Accurate Flight Control Algorithms
The entire ground control system combines GPS 6DOF(Six Degrees of Freedom)
inertial measurement unit, magnetometer, and pressure altimeter sensors to optimize
robustness of algorithms and robotic control logics. Ground control system utilizes advanced
GPS/INS(Inertial Navigation System) proprietary algorithm technology in the entire design.
Even in adverse conditions, high vibration and high demand environments, the aircraft
maintains flight stability accurately to ensure mission success.
5.2. Mission Planning
Customizable Waypoints
We can carry out special settings, such as height, latitude and longitude, flight speed, the
nose toward, the turning patterns and residence time etc. Also we can batch for all
destinations, by setting once if required. Especially, we can customize specific properties such
as altitude, turnmode, forward flight speed and head degree.
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6. TESTING
6.1. ITU multicopter team checklist
Before Flight:

Check weather.

Battery fully charged and undamaged.

Remote check on, check frequency.

All connections, screws and bolts torqued to spec.

All components undamaged and placed in the correct orientation.

All cables secured and placed properly.

Frame arms and landing gear checked straight.

Check motors turning in the correct direction.

Check propellers balanced, undamaged and in the correct direction.

Check toolbox with screwdriver, hex tools, zipties, double-sided tape, pliers, stiletto,
electrician's tape and velcro.

Check spare props, spare batteries and fire extinguisher.
Before Flight - At Ramp:

Check sufficient visibility, no persons or foreign objects near aircraft.

Final visual check.

Check GPS calibration.
During Flight:

Pilot to monitor the aircraft at all times.

Team members except the member to watch the surroundings and keep people out of
the danger zone.
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
Aircraft to never leave visual or datalink range.

In an emergency, the aircraft is to be landed immediately, or to be crashed away from
people or property if safe landing is not possible.
Crash:

Move to vicinity of crash with fire extinguisher.

Aircraft not to be touched until propellers stop.

Battery to be removed before any other intervention.
After Flight:

Battery/batteries to be recharged, cells to be balanced if necessary.

Check if any systems are damaged.

Check motor and ESC temperatures
6.2. Mission Risks & Contingency Plans

Datalink Cut:
Last known location of contact to be established.
Aircraft to be relocated visually, if possible.
"Return Home" command to be issued through the GCS continuously.
Authorities to be notified if no contact is made for 2 minutes.
Immediate landing if contact is re-established.

Failure on Board:
Immediate safe landing to be made if possible.
Immediate grounding of the aircraft, through throttle cut, to be made if safe landing is
impossible.
Safe landing is possible in the following circumstances: GPS failure, single engine failure,
payload failure.
On all other circumstances the aircraft will be crashed by throttle cut.
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