The document proposes a design for a low-cost outdoor surveillance system using an unmanned aerial vehicle (UAV). The system would use a quadcopter mini-UAV equipped with an onboard camera and autopilot system. Video from the camera would be transmitted to a ground control station via an FM link. The ground station would process the video for viewing in real-time. Key components of the design include the quadcopter MAV for aerial surveillance, onboard hardware like the autopilot and camera, and a ground station for receiving and displaying the video feed.

1. Preliminary design proposal
for
“Deployable Low Cost Outdoor Surveillance
System with Remote Access to Imagery”.
Submitted by –
Electronics Students Team,
Northern India Engineering College,
FC-26, Shastri Park,
New Delhi
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2. Index
1. Abstract - 3
2. Component Description
2.1) MAV - 4
2.2) On board hardware
2.2.1) Autopilot System - 5
2.2.2) Inertial Measurement Unit - 6
2.2.3) Visual Sensors - 7
2.2.4) Power Source - 7
2.3) The ground Control Station - 8
3. Communication Links between MAV and GCS - 9
4. References - 9
LIST OF FIGURES
Figure Topic
1. Modular decomposition of the problem.
2. Schematic of the Solution.
3. Quad rotor MAV
4. To show the quad rotor Dynamics
5. To show the co-ordinate system of a quad rotor.
6. Autopilot System with inertial measurement unit.
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3. 1. Abstract
The following paper is in response to the project challenge where we
have to conceive, design and develop a “Deployable low-cost outdoor
surveillance system”. The following design solution has evolved with the
basic idea of the following challenges.
• Development of a suitable lightweight system in which a sensor is
airborne for carrying out surveillance at a minimum height of 30m and
above ,for a minimum of 2 minutes ,to do imaging of a proportionate
area below.
• Sensor should be able to detect man-sized objects in above-mentioned
conditions.
• Recognizable real time video information should be transmitted to the
ground receiver point suitably located in the observation area.
Proposed solution
The basic approach used to solve the problem was to divide the
problem in modules. The modules of the problem are shown in Figure 1. For
the fulfillment of the above challenges we propose a development of a MAV
or Miniature Aerial Vehicle which is a small UAV (Unmanned Aerial
Vehicle).The MAV will be responsible for carrying the sensor to a suitable
altitude. Considering the conditions in above challenges we propose a quad-
rotor MAV, due to its characteristics such as vertical takeoff and landing and
hovering at any point so that the surveillance can be taken out effectively
without much distortion in the transmitted video.
The MAV will be semi-tele-operated and for this purpose it will carry an
Autopilot system and a standard Remote Control link (also called a safe link).
This will relieve burden on the human operator on the ground and will
provide a much stabilized and smoother flight.
The sensor or video camera will be a low-cost and light weight CCD
camera with analog video output. The output will be transmitted to ground
using a FM video transmitter. The transmitted video will be received by a
Frame-Grabber interfaced at the Ground Control Station. This will provide us
video in digital form which can easily be manipulated using software system
at the ground station.
However, due to constraint that the image received on PCI based
frame-grabber, so we have to use a high end microprocessor based Personal
computer. The entire working block diagram is shown in figure 2.
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4. 2. Component Description
2.1. The MAV
Unmanned aerial vehicles (UAVs) are crafts capable of flight without an
on board pilot. They can be controlled remotely by an operator, or can be
controlled autonomously via preprogrammed flight paths.
A quad-rotor helicopter is an aircraft whose lift is generated by four
rotors, as shown in figure -3. In order to generate lift without causing the
rotational effects in the opposite direction multiple rotary wing craft use
paired rotors spinning in opposite directions to counteract each other’s force,
this obviously has the advantage that there is no need to use power on a
stability control as all of the force generated by the rotary wings acts in the
same direction.
Control of such a craft is accomplished by varying the speeds of the
four motors relative to each other. A quad-rotor has four motors located at
the front, rear, left, and right ends of a cross frame. The quad-rotor is
controlled by changing the speed of rotation of each motor. The front and
rear rotors rotate in a counter-clockwise direction while the left and right
rotors rotate in a clockwise direction to balance the torque created by the
spinning rotors (Fig 4 and 5).
The relative speed of the left and right rotors is varied to control the
roll rate of the UAV. Increasing the speed of the left motor by the same
amount that the speed of the right motor is decreased will keep the total
thrust provided by the four rotors approximately the same. In addition, the
total torque created by these two rotors will remain constant. Similarly, the
pitch rate is controlled by varying the relative speed of the front and rear
rotors.
To control the yaw a Multiple Rotary Wing craft uses it's motors in two
groups, those spinning clockwise and those spinning anticlockwise, if the
craft wants to rotate clockwise the motors spinning clockwise slow down and
the motors spinning anticlockwise speed up, this unbalances the rotary
forces and rotates the craft clockwise with the added advantage that as the
clockwise and anticlockwise motors have decreased and increased their
speed by the same amount the craft's lift remains the same allowing the
craft to rotate on the spot.
In order to control pitch and roll, and therefore movement as the lift
will be converted into lift and thrust due to the diagonal force vectors, the
craft will decrease the speed of the motor in the direction that it wants to
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5. travel whilst simultaneously accelerating the motor directly opposite. It will
also be necessary to speed up the other motors slightly so as not to lose
altitude. This will decrease the lift on the front of the craft and increase it at
the rear changing the pitch, or roll depending on how you look at it, thus
changing the direction of the force vector to be mostly lift but some lateral
movement.
Advantages
1. Vertical take-off and landing (VTOL)
2. Can hover at any place for effective surveillance.
3. Can fly at very low altitudes.
4. Easy to control
5. Good maneuverability
6. Simple mechanics
7. Increased payload
Disadvantages
1. High energy consumption
2. Large size
2.2. The On-board Hardware
2.2.1. The autopilot system
The Autopilot system is the important part of the MAV as it is
responsible for stabilizing of the vehicle in air. It also removes overhead on
the ground support system. It fulfills the following tasks:
1. measuring the angular velocity of the three axes
2. measuring the acceleration data of the three axes
3. measuring the atmospheric pressure for altitude control
4. evaluation of a digital compass signal
5. measuring the battery voltage
6. evaluation of the R/C signal
7. processing of sensor data and computing the actual angular position
8. driving four Brush less ESC (electronic speed controllers)
All the telemetry data, which is recorded by the Autopilot board, is
send to the ground control station which is utilized for the effective
controlling of the MAV and is logged for future debugging and problem
solving purposes. Considering the challenges in our project we eliminate use
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6. of GPS system as well as telemetry link because there is no need for long
range surveillance where the MAV has to fly out of sight regions and the time
of flight is also very less. However, GPS is recommended for fully automatic
flight. But due to cost considerations and lack of the requirements we
eliminate use of GPS in our Autopilot module. Our Autopilot module is based
on study of TWOG module which is open-source Autopilot hardware
developed by Paparazzi UAV. After studying and adapting the following
hardware design for our design solution we are capable of developing a low
cost and light weight effective autopilot system. The basic initial system
design is shown in figure-6 .
2.2.2. Inertial Measurement Unit
• Complete inertial measurement unit (IMU) with 3-axis gyro, 3-axis
accelerometer, and 3-axis magnetometer.
• The Gyro Sensors measure the angular velocity (rotational speed) of
each axis. We need three sensors to stabilize all three axes. These
sensors are the most elementary components for the MAV stability in
air.
• The main function of the acceleration sensor is to measure the actual
tilt of the MAV and to support the altitude adjustment. Here we use a
three axis sensor.
The configuration of both the on board system is shown in figure – 4.
Brief Description
• The main component of the system is LPC2148 MCU. The Philip's
LPC2148 is an ARM7 based micro controller. The ARM7 is a low-power
32-bit RISC processor core and the Philip's LPC2148 has 512KB on-chip
Flash ROM, 40KB RAM and can be clocked at 60MHz.
• It has two UART (UART0 and UART1) or Universal Asynchronous
receiver and transmitters. One is used as an interface for the radio
modem which receives the control signal and transmits the telemetry
data. The other UART is spare and can be used to interface GPS system
later.
• The Texas Instruments PTH08080WAH switching 5V/2.25A is an
integrated 5V switching power supply module.
• LM3940 is a 3.3V /1A linear regulator for 5V to 3.3V c
• The four motor controllers are used to control each servo motor for
better control.
• The remote control receiver is interfaced with the input capture
module which is used to control the MAV from the ground by any
human operator.
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7. 2.2.3. The Visual Sensor
Due to lack of any light weight camera with digital output we have to
use a camera with analog output. CCD camera with analog output and up to
60m of capturing distance is perfect for our project.
A charge coupled device (CCD) camera is an apparatus which is
designed to convert optical brightness into electrical amplitude signals using
a plurality of CCDs, and then reproduce the image of a subject using the
electric signals without time restriction. Charge coupled devices or CCDs are
arrays of semiconductor gates formed on a substrate of an integrated circuit
or chip. The gates of the CCD are operative to individually collect, store and
transfer charge. When used in image applications, the charge collected and
stored in each gate of the array represents a picture element or pixel of an
image output form.
Key Specifications/Special Features of the sensor
Image sensor: 1/3-inch Sharp CCD
Horizontal resolution: 420TV lines
Minimum illumination: 0.3/0.8 LUX
System: PAL/CCIR or NTSC/EIA
IR distance: 40 to 50m (at night)
IR lamps: 55
Zoom lens
Gamma characteristic: 0.45
Built-in lens: 6mm
IR distance: 60m (at night)
Power consumption: 12V DC
Storage temperature: -20 to +60 degree Celsius
Dimensions: 80 x 120mm
2.2.4. Power Source
The battery must be light weight, low cost and high capacity to support
various on-board components. For this purpose we have chosen a lithium
polymer (Li Po) batteries chosen for their low weight and high output.
Lithium-ion polymer batteries, polymer lithium ion, or more commonly
lithium polymer batteries (abbreviated Li-poly, Li-Pol, LiPo, LIP, PLI or LiP) are
rechargeable batteries which have technologically evolved from lithium-ion
batteries.
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8. The voltage of a Li-poly cell varies from about 2.7 V (discharged) to
about 4.23 V (fully charged), and Li-poly cells have to be protected from
overcharge by limiting the applied voltage to no more than 4.235 V per cell
used in a series combination. Overcharging a Li-poly battery will likely result
in explosion and/or fire. During discharge on load, the load has to be
removed as soon as the voltage drops below approximately 3.0 V per cell
(used in a series combination), or else the battery will subsequently no
longer accept a full charge and may experience problems holding voltage
under load.
2.3. The Ground Control Station
The ground control station acts as a base system and a support
system. It receives the video information from the MAV and processes it to a
recognizable video in real time. It also acts as a support system as it receives
the telemetry data and sends the control signal. The visual system along
with the telemetry data also acts as a feedback to the human operator at the
ground station which uses the remote controlled link to operate the MAV.
We initially planned to use a stand-alone embedded based ground
station but cost limitations compelled us to use a general purpose personal
computer system. The main problem was the unavailability of a frame-
grabber which can digitize the analog video received at the ground station.
Moreover the technology, cost and weight limitations also do not allow to use
any digital camera. However due to these considerations we are using a
desktop system with interfaced DVR or frame- grabber running on a Windows
based system. The computer will act as a server and will transmit the video
over wireless LAN (Local Area Network). The video can be received on any
PDA or any laptop at a suitable area around the GCS. The ground control
system is also open source called PAPARAZZI shipped under the GPL or
General Public license.
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9. 3. Communication Links between MAV and GCS.
There will be two links between the MAV and GCS. These links will be
• Safe link
• Video link
The safe link will be used as to control the MAV by any human operator
at the ground. It will be RF (radio frequency) based Remote control link so
that the human operator can interfere in case of any on board hardware
failure. The flow of information will be mostly in upward direction or towards
MAV so this is only an up link.
The video link will be the down link from MAV to the GCS and will
transmit the video from the MAV. The transmission will be based on
frequency modulation (FM) techniques. The suitable frequency band for
transmission will be chosen so as to minimize the interference caused due to
the RF remote control link.
4. References
1. Valvanis K. , “Advances in Unmanned Aerial vehicles”, Springer
Publications.
2. Gregory L. Sinsley, Jodi A. Miller , Lyle N. Long, Brian R. Geiger, Albert
F. Niessner, Jr., and Joseph F. Horn , “An Intelligent Controller for
Collaborative Unmanned Air Vehicles”, Proceedings of the 2007 IEEE
Symposium on Computational Intelligence in Security and Defense
Applications (CISDA 2007).
3. Paul Pounds, Robert Mahony, Peter Corke “Modelling and Control of a
Quad-Rotor Robot”.
4. William k. Pratt, “Digital Image processing”, Wiley Publications
5. http://en.paparazzi.fr – The Paparazzi UAV project.
6. http://www.mikrokopter.de/ - The Mikrokopter UAV project
7. http://www.wikipedia.org/
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10. Fig – 1 Modular decomposition of the problem.
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11. Fig – 2 Schematic of the Solution.
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12. Fig – 3 Quad rotor MAV
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13. Fig- 4 The quad rotor Dynamics
Fig-5 The co-ordinate system of a quad rotor.
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14. Fig 6 – The basic circuit diagram of Autopilot system and IMU
interfaced to a Micro controller
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