Report - Low Cost Surveillance DRDO

8/6/2019 Report - Low Cost Surveillance DRDO

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Student Competition

Deployable low cost outdoor surveillance system

Abhiram.R.N

Anoop.M.K

Gadhadar.C

Madusudhan.C.S

Sridhar.B.V

Vikas Tavanandi

Vincent Shanthakumar.S

B.M.S College of Engineering

P.O. Box No. 1908, Bull Temple Road, Bangalore-560019.

Project Advisor

Dr.L.Ravikumar

Department of Mechanical Engineering

B.M.S College of Engineering, Bangalore.


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Abstract

An airborne surveillance system would be successful if it is light-weight, has a high maneuverability,

has stealth and if it could encrypt transmissions to and from the base station. Our design for the system

tries to optimize these factors.

We will be using a quad-rotor design for our aircraft. The advantage of a quad rotor over aconventional winged plane is that it has a very high maneuverability. It can hover over a place and

make an observation. By simply changing the rotation speed of the motors, we can control the

direction of motion of the system. Aluminum will be used for the legs and the central plate as it is easy

to fabricate. In order to enable a higher payload we will be using Fiber glass for the arms of the vehicleas it is lighter than aluminum. The fiber glass components can be easily obtained according to our

design specifications from local manufacturers.

Since the system will be of very small dimensions (about 50 cm X 50 cm) it will be hardly registered

on radar. The only possible method of detection would be from the sound produced by the craft. Thesound is emitted due to the mechanical vibrations of the system. For this design of the vehicle the arms

experience maximum vibration. Fiber-glass arms will produce fewer vibrations than metal arms as itselasticity is much smaller. The entire aircraft will be painted blue so that it will be hard to discern by acasual observer.

A color video camera with an in-built IR-emitter/detector will be our sensor. The IR camera can be

used to take black and white images at night time. The camera has an in-built transmitter. The camera

has an aperture of 45 Degrees and will be placed at an angle to the horizontal. This will enable us torecognize objects more easily. In this position we will be able to see the vertical dimensions of the

objects apart from their top view. All transmissions will use fast hopping spread spectrum modulation

and this will guarantee a secure line. The transmitter will operate in the 2.4 GHz spectrum. The dataobtained from the camera will be transmitted over the secure link to the base station. In the base

station, the computer will select the best frame among a series of images and will apply feature

detection techniques. These feature points are then compared with those in the database to detectobject of interest. This will help us to highlight all the objects that are of human-size.

Our craft will also have the MAX2740 G.P.S module. This will help us identify the co-ordinates of

the craft at all times. The GPS signals will be sent over the secure line in the audio channel of the

video data line. The co-ordinates of the system will be used in Google Earth to get a terrain mappingof the region. The data from the image processing operations will provide the possible location of theHuman sized objects. These two data streams will be combined to give a single image highlighting the

positions of the objects along with their possible co-ordinates.

The power system for all these components will be a Lithium-Polymer battery. This battery was

chosen because of its capability to support a large current requirement.

Almost all the components that we will be using for the project can be procured locally. None of thecomponents have any kind of import restrictions. Since the components can be sourced locally, the

Aircraft can be built and serviced at a low cost.


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Table of Contents

1. INTRODUCTION .............................................................................................................. 4

2. VEHICLE CONCEPTUAL DESIGN ................................................................................. 4

3. QUADROTOR .................................................................................................................. 5

3.1 ANALYSISANDCOMPONENTSELECTION ...................................................................... 53.1.1. Body or Structure .............................................................................................................................. 63.1.2. Selection of Motor ............................................................................................................................. 63.1.3. Motors ................................................................................................................................................ 73.1.4. Propellers .......................................................................................................................................... 73.1.5. Battery ............................................................................................................................................... 7

3.2 CONTROLSYSTEMDESIGNANDCOMMUNICATION ...................................................... 93.2.1. AVR microcontroller (ATmega 16) .................................................................................................... 93.2.2. RF Communication ............................................................................................................................ 93.2.3. The control circuit details ................................................................................................................. 103.2.4. Camera ............................................................................................................................................ 123.2.5. GPS/ GLONASS /IRNSS ................................................................................................................ 13

3.3 VIDEOANALYSIS ............................................................................................................. 14

4. CONCLUSION ............................................................................................................... 15

5. REFERENCES & BIBLIOGRAPHY ............................................................................... 16


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1. INTRODUCTION

An airborne surveillance system can provide tactical inputs which will put a person using the

system in an advantageous position. In order to make an effective surveillance system, we recognized

that we need people who have knowledge in the fields of Mechanical, Electronics and Software

Engineering to work together. Keeping this in mind we have put together a team consisting of 2

Mechanical engineers, 4 Electronics engineers and 1 Computer Science Engineer.The Mechanical Engineers will be working on the Body of the system. They will deal with the

proper aerodynamic design for our vehicle and the materials used to fabricate it.

The Electronics engineers will work on programming the micro-controller, transmission ofcontrol and data signals to and from the vehicle and also on processing the images obtained from the

on board camera.

The Software engineer will work on integrating the image and GPS data with the open source

Google maps interface. This will provide a visually rich view of the area under surveillance. It willalso provide almost exact co-ordinates of the targets.

The problem statement of the project requires that we build a system that satisfies the following

conditions

The surveillance system should be light in weight.

The sensor should remain airborne for a minimum of 2 minutes at a minimum height of 30m tocarry out 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 pointsuitably located in the observation area.

In the subsequent pages we will show how we will tackle all these requirements.

2. VEHICLE CONCEPTUAL DESIGN

In order to be an effective surveillance system, the Air borne vehicle must have the following

features:

Ability to HOVER: This is highly advantageous in surveillance applications. Since the vehicleis expected to transmit video image of an area continuously, the hovering ability enables it totransmit a better video in terms of the focusing over the area of interest.

MANEUVERABILITY in all directions about hover: Maneuverability is an equallyimportant ability that the vehicle should have. This is required to move the vehicle smoothly to

a desired location from the base station.

ENDURANCE of at least 5 minutes: 5 minutes was judged a practical minimum to allowsufficient time for take off and landing.

The use of a fixed wing aircraft, like an airplane, for this project was ruled out because of itsinability to hover. The use of a lighter-than-air aircraft, like an airship, which even though has theability to hover, was not appropriate for this project because of its large size and slow cruise speed that

made it an easy target. It is also more suitable for indoor application rather than outdoor. The design of

a helicopter was considered suitable. But as the helicopter involves very intricate mechanisms, and isalso very difficult to maneuver, the idea of designing a helicopter was turned down.

Taking all these into account, a QUADROTOR or QUAD ROTOR HELICOPTER was

considered best suitable for this project.


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3. QUADROTOR

A quad rotor, also called as quadrotor helicopter or quadrocopter, is an aircraft that is lifted and

propelled by four rotors. Unlike standard helicopter, quadrotors are able to use fixed-pitch blades,

whose angle of attack does not vary as the blades rotate. Hence the use of complicated mechanisms to

change the pitch of the blades while in rotation is not required. Control of the vehicle motion can be

achieved by varying therelative speed of each rotor to change the thrust and torque produced by eachto achieve satisfactory speeds.

There are two different propeller rotations. The figure showsthat the front and back propellers (props 1 and 3 respectively)

turn clockwise, while the right and left propellers (props 2 and 4

respectively) spin counter-clockwise. This provides automaticbalance to the aircraft.

To hover, all propellors rotate at the same speed. When

doing so, the forces between the clockwise propellers on one

hand, and the counter-clockwise propellers on the other hand,

are balanced out. This makes the quadrocopter hang steady inthe air.

To be able to fly in one direction, the quadrotor will be

brought out of balance. The speed of the propeller that opposesthe desired direction is increased. This makes the quadrotor tip

over in a certain direction. Fig 1: Direction of rotation of the 4rotors

Example: To fly forward (positive y-direction), the propellor 3 has to turn faster. This is called "pitch".Left and right movements (x directions) are called "rolls".

Turning around it's vertical axis is called "yaw". The force required for producing yaw is obtained by

changing the speeds between the forward/backward propellers and the left/right propellers. Example:

to be able to yaw clockwise, the forward/backward propellers(1 & 3) will turn faster and the left/rightpropellers(4 & 2) will slow down a little. This makes the quadrotor turn clockwise, while maintaining

the same height.

The various advantages of quadrotor over conventional helicopters are as follows. First,

quadrotors do not require mechanical linkages to vary rotor angle of attack as they spin. Thissimplifies design of the vehicle. Second, the use of four rotors allows each individual rotor to have a

smaller diameter than the equivalent helicopter rotor. Also, as the two pairs of rotors are counter

rotating, the net aerodynamic torque and the angular acceleration about the yaw axis is zero, whichimplies that a separate yaw stabilizing rotor is not required.

3.1 ANALYSIS AND COMPONENT SELECTIONThe most important parameter to be considered when building an airborne system is the

weight. The mechanical aspects of the vehicle design could be divided into the design of the body orstructure, battery, motor and propeller combination. The selection and design of these depends on the

weight of the electronic components. The electronics weight was estimated to be about 400g

(including the camera). The total weight of the vehicle was estimated to be about 1350g. In order toaccount for any unexpected additional components we have assumed a weight of 1.5 Kg. (Table 1shows the rough estimation of the weight of each component in grams).


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The lift produced by each rotor is given by the formula,

F = 0.5 * density * (velocity) ^2 * (A * C)

F= 0.5 * 1.24 * V ^2 * (0.00785 *1)

V = 28.668 m/s

But V = radius * angular velocityTherefore, angular velocity = 573.3625 radian/s

= 32,851.25 degrees/s

= 91.25 Rotations/s= 5,475 rpm

Therefore, a motor with a minimum speed of 6000 rpm can be used. Higher speed produces morethrust, which is preferable.

3.1.3. Motors[15]

Brushless DC motors:

Kv: 840 rpm/V

Maximum current: 8.4 A

Advantages: The Brushless motors are more efficient and have longer lifetime than brushed motors

due to the absence of friction and electrical losses arising from having brushes. Since theelectromagnets are placed at the perimeter, it can be cooled by radiation rather than air flow inside the

motors hence, this reduces the size and motor parts can be packaged to protect from external agents

like dirt. Reduced noise, lower electromagnetic interference and low power consumption are added

advantages of using Brushless motors.

3.1.4. Propellers[10]

2 pairs of counter rotating propellers of 10cm diameter are used. EPP1045 propeller was considered

for its high thrust generation capacity. The diameter was limited to 10cm taking into account the size

of the entire structure and the portability.

Pitch: 4.5``

Blades per propeller: 2

3.1.5. Battery[8]

Lithium-polymer or Li-Po batteries

Voltage: 11.1V

Maximum Discharge Current: 15C

Capacity: about 2100mAh

Advantages: Light weight, high power to weight ratio, high endurance.

The above data shows that each battery will last for 4 minutes when drained at its Maximum

Discharge current. Hence, we will use 2 such battery packs to provide us a minimum flying time of 5minutes using the above mentioned motors.


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Fig 2: QuadRotor model created using SolidEdge

Fig 3: Different views of QuadRotor


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3.2 CONTROL SYSTEM DESIGN AND COMMUNICATION

Due to the mechanical designs inherent stability, controlling the airborne vehicle becomes alot easier. Also MEMS accelerometers are employed to obtain stability. As a part of the control

system, we provide a keypad to execute basic maneuvers. Spread spectrum transmission of data makes

the communication system secure and immune to jamming. The motors will be controlled by an Atmel

ATmega16 micro controller. The video feed from the camera is sent to the computer at the base stationthat will perform the video analysis and display the processed data as a continuous video. MATLAB is

used for this purpose.

3.2.1. AVR microcontroller (ATmega 16)

AVR stands for Advanced Versatile RISC. The Atmega16 is a low power AVR 8-bitMicrocontroller. It was chosen to control the motors on the surveillance vehicle. This microcontroller

has 32 programmable I/O lines, 16K bytes of In-system Self-Programmable Flash memory, 1K byte

internal SRAM, 512 bytes EEPROM. This AVR microcontroller has several hardware features thatprove to be useful in the surveillance vehicle and simplify the interfacing of motors with the

microcontroller. The Features of this microcontroller that made us incorporate it in our project are: -

Advanced RISC Architecture that makes programming easier Peripheral Features

Two 8-bit Timer/Counters with Separate Pre-scalers and Compare modes

One 16-bit Timer/Counter with Separate Pre-scaler, Compare Mode, and Capture mode

Four PWM Channels that can be employed for 4 motors

On-Chip Analog Comparator

The datasheet[11]

of ATmega 16 is provided in the references

3.2.2. RF Communication

A pair of TWS/RWS 434 transmitter receiver module interfacing micro controller is used to

send and receive data between the ground station and quad-rotor. Two 433MHz whip style antennasare also used in the set up for long range detection. A 4-bit encoder (HT-12E Encoder IC) is used in

the transmitter circuit, to convert the parallel output from the keypad to Serial data output. The serialdata is transmitted through RF. A 4-bit decoder (HT-12D Decoder IC) is used in the receiver circuit to

convert the serial data received through RF to parallel data which can be given to the micro controller.

TWS 434: It outputs up to 172.44mW (Max) at

433.92MHz. It has an operating range of about 400 ftoutdoors, or about 200 ft indoors. It can go through most

walls. The operational voltage varies from 1.5 to 12 V and

accepts both linear and digital input. Figure 4 shows the

schematic of the transmitter with its pin specifications.

Fig 4: TWS-434 RF Transmitter


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RWS 434: This too operates at 433.92MHz with an operational voltage of around 4.5 5.5 V DC. Its

sensitivity is 3V, and it can have both linear and digital outputs. Figure 5 shows the schematic of thisreceiver with the pin specifications.

Fig 5: RWS-434 RF Receiver

3.2.3. The control circuit details

The vehicle will be controlled using a RF control. The Remote control consists of 6 switches inthe form of a keypad. Four of these switches are used to maneuver the quad rotor in the four different

directions. One switch is used to turn it on and control the speed and the other one is used to turn on

the camera. The output from the keypad is a 4-bit sequence. This is fed to HT 12E 4-bit encoder IC. Itis operated at the frequency of 8 MHz. The encoder IC converts the parallel input into a serial encoded

output. This is then fed to the TWS434 RF transmitter.

The control signals are received by RWS434 RF receiver mounted on the quad-rotor. This is

then fed to HT 12D decoder operated at same frequency as the encoder (i.e., 8 MHz). This decodes theserial data into a 4-bit parallel output. This is then given as input to the port A (shown in figure 7) of

ATmega16 mounted on the quad rotor and depending on the code generated, appropriate action is

taken. The list of intended functions are given below

TABLE 2: List of functions intended for our use

Code Function

0000 The rotors speed is set so that they hover in their place

0001 The back rotors speed is increased thereby generating a backward thrust force that drives

the vehicle forward

0010 The left rotors speed is increased thereby generating a leftward thrust force that drives the

vehicle towards right

0011 The right rotors speed is increased thereby generating a rightward thrust force that

drives the vehicle towards left

0100 The front rotors speed is increased thereby generating a forward thrust force that

drives the vehicle backward

The motors are controlled using brushless ESC[9]

(Electronic Speed Control) ICs. The ESC

converts the batterys DC voltage into 3-phase AC that the brushless motors can use. But, this is morecomplex as the correct phase varies with the motor speed. Hence, the back EMF from the motor is

used by ESC to set the phase. These ESCs can be programmed to control the low voltage cut-off

limits, timing, acceleration, braking and direction of rotation. Thus, we can efficiently control theoperation of brushless motors.


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Fig 6: Circuit Diagram for Transmitter section

Fig 7: Circuit Diagram for receiver section


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Accelerometer[13]

In order to enable an automatic control of the vehicle we will be using the Analog DevicesADXL-30013 MEMS based 3-axis accelerometer. This device will sense an acceleration of up to 3g in

all the 3 axis of motion. This information is obtained as an analog signal. The Accelerometer is as

shown below.

Fig 8: Accelerometer circuit diagram

The sensor will register acceleration whenever there is a sudden acceleration of the quad-rotor.

Whenever acceleration is detected, the micro-controller will attempt to produce acceleration in the

opposite direction by decreasing the speed of the corresponding motor. By doing this within specifiedlimits we will be able to maintain the Quad rotor in a stationary position.

3.2.4. Camera[6]

The camera will form the most important sub-system in our design. We will be using the Equicom

High Power Camera with Night Vision as our sensor.This camera features a built-in wireless transmitter with

a range of over 200m.

The camera

weighs 245g, but we will beremoving all the protective coverings in order to reduce

the overall weight of the quad rotor.

The camera uses the latest CMOS sensors at its

core. We will attach the camera at a small angle to thevertical plane. By doing so we will be increasing the

aperture of the camera, and at the same time, will make

the task of locating targets easier. Since the camera has ahigher field of view in this mode, we will be able to see a

larger area of the human sized object.

Fig 9: EquicomHigh Power Camera with Night

VisionSince the camera has a built-in IR emitter, it can produce clear black and white images in pitch

dark. This allows us to use the quad rotor for surveillance during low light conditions and at night

times without any modifications.

The camera uses spread spectrum modulation in order to transfer the video signals. Spread

Spectrum Modulation is a data encryption technique that is very difficult to crack. Thus, the Camerawill be transferring Video signals with the highest encryption. The Audio channel of the camera will

be used to transmit the GPS signals.


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The camera requires a power supply of 12V/500mA and this will be met by the on board Li-

Polymer Battery. The Receiver of the camera is connected to a computer for further processing of theimages. The camera will be encased in a separate compartment below the quadrotor body, with

sufficient cushioning to avoid damage due to mechanical shocks.

3.2.5. GPS/ GLONASS /IRNSS

GPS is a network of 24 American satellites that generate timing signals which can in-turn beused to find out the co-ordinates of a person anywhere on Earth. GLONASS is the Russian equivalentof the GPS system. The IRNSS (Indian Regional Navigational Satellite System) is India's own

Satellite based navigation system which is under development right now. The timing signals from any

one of these systems could be used to obtain the precise location of the Quad rotor.We will use the MAXIM2740 [7] GPS/GLONASS Integrated Receiver and Synthesizer. This

small chip can receive the signals from the consortium of the GPS satellites and can process it. It will

produce the precise co-ordinates at its output.The Co-ordinates will be transmitted back to the base station using the unused Audio channel

of the Camera. By doing this we will not have to use a separate transmitter and we will be making a

full use of the bandwidth allocated to the video channel.

The co-ordinates thus obtained will be used for tracking the Quad Rotor at all times. This datawill be passed to the open source Google maps API. This will finally produce the positions of all

human sized objects on a map. The codes for performing this operation will be written by the

Programmer in our team; who has worked on similar features for Google before.

Fig 10: MAXIM2740 GPS/GLONASS Integrated Receiver and Synthesizer circuit diagram


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3.3 VIDEO ANALYSIS

Before we actually try to extract human-like feature points, we first need to eliminate noise

from the images obtained. The basic short noise or impulse noise is first taken into account that arisesdue to the equipment used. This noise is usually in high frequency range hence, it is eliminated by

using a content based median filter that will intelligently filter only images with noise and will not

contribute towards blurring of the images. This is achieved by calculating the distance of a pixel with

its neighbours and it is compared with a threshold and a decision is made whether to apply the filter ornot. Further, this image is subjected to feature extraction and detection techniques to identify human

sized objects. For any image, there will be certain points of interest or feature points on the

object to be recognized. These points are taken from training images and stored so that they can beused later when detecting these objects in the test image. It is to be noted that, for this to work

efficiently, the feature points must be robust.

We propose to use the SIFT (Scale-Invariant Feature Transform) technique that satisfies the above

conditions. As mentioned earlier, in SIFT, an object in the test image is recognized by comparing eachfeature point from the test image to the stored database and finding matching features based on

Euclidean Distance of their feature vectors. The algorithm basically consists of the following steps

Extraction of the feature pointsThis is done by convolving the image with Gaussian filters of various scales. The difference of

these successive blurred images is taken. Feature points are then taken as maxima or minima of

the Difference of Gaussians (DoG) that occur at multiple scales. Hence, the generic equation

for such an operation would beD(x, y, ) = J(x, y, ki) J(x, y,kj)

and

J(x, y, k) = G(x, y, k)*I(x, y)Where,

D(x, y, ) is the Difference of Gaussian image

G(x, y, k) is the Gaussian filterI(x, y) is the original image.

Feature point localizationThe first step produces too many feature points. Some of the poor feature points can be

eliminated by performing a detailed fit to the nearby data for accurate location, scale, and ratio

of principal curvatures. This will help us to eliminate the poor feature points.

InterpolationFurther, the position of each image is determined using interpolation methods which will

improve the matching and stability. Quadratic Taylor expansion of the Difference of Gaussian

function with feature point as origin is used to perform the interpolation. This step increases the

robustness of the feature points. The second order Taylor series can be considered to eliminate

low contrast points that may in fact be redundant. But, this may not be necessary in all cases.


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Edge response eliminationThe obtained feature points may have strong edge response even if it is not immune to noise.

Such points are eliminated by a similar approach as Harris operator for corner detection.

OrientationIn order to achieve invariance to rotation we can assign one or more orientation to the featurepoints using the direction gradient.

Feature points descriptorsFinally, each feature point needs a descriptor to be calculated more or less similar to orientation

assignment. This will make the feature point highly distinctive, partially invariant there by

giving us efficient method to base our comparisons.

Using the feature points obtained from the above steps, we can compare these with the training

images to get efficient results.

Note: All the electronic components will be housed in the dome shaped compartment.

4. CONCLUSIONIn our paper, we have presented simple and effective solution to the proposed problem. We

have tried to predict most of the problems that may arise and have provided suitable solutions to thesein terms of design and control system. The paper shows the use of unconventional quad rotor

mechanism to fly the sensors over the battle field to collect the data. The design also provides a secure

data-link to the base station to transfer the data collected from the sensors. Since the design has beenconsidered as segments and then unified, we can quickly adopt to newer technologies. For example,

the GPS model can be replaced by IRNSS on its inception. The components are accessible for quick

replacements which is desirable in any battle field situation. The algorithms employed to process the

data to obtain useful information are robust and hence promise very high efficiency.


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5. REFERENCES & BIBLIOGRAPHY

1) http://www.performancecomposites.com/design_guide1.html : Fiberglass and other materials

comparison table.

2) http://ecommons.library.cornell.edu/bitstream/1813/93/2/Designof4RotHoverVehicle.pdf :Design and Mechanical Equations that are required to make a quad rotor fly. Master thesis, Cornell

University.

3)http://www.dce.edu/current/DCE_Newsletter_Sept_2006.pdf : Pictures of Quad Rotor

4) http://ieeexplore.ieee.org/iel4/5402/14705/00671033.pdf?arnumber=671033 :Noise reduction in

mechanical systems

5) http://www.aerospaceweb.org/question/aerodynamics/q0015b.shtml : Formula for rotor speed

6) http://www.equicom.ie/high-power-camera-with-night-vision-20-p.asp : Information about thecamera that will be used.

7)MAXIM Integrated Products, Sunnyvale, California

8)http://www.rctoys.com/rc-toys-and-parts/TP-2100-3SPL/RC-PARTS-THUNDER-POWER-PRO-LITE-LI-POLY-BATTERY.html: Batteries

9) http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4204 : Electronic Speed

Control

10) http://www.rctoys.com/rc-toys-and-parts/MPI-EPP1045/RC-PARTS-APC-PROPELLERS.html :

Propellers

11)http://www.datasheetcatalog.org/datasheet/atmel/2466S.pdf : ATmega16 datasheet

12) Lowe, D.G..2004. Distinctive Image Features from Scale-Invariant Keypoints. January 5, 2004

13)http://www.analog.com/en/mems-and-sensors/imems-accelerometers/adxl330/products/product.html :MEMS Accelerometers

14) http://en.wikipedia.org/wiki/Quadrotor : Wikipedia link for Quadrotor.

15) http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5111 : Motors

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Report - Low Cost Surveillance DRDO