Designing Quadcopter and Using camera output for

crowd estimation/behaviour.

Students Project Guide

Devesh (136/10) Mrs Farida Khurshid

Nikhilesh Sharma (185/10) Associate Professor

Shubham Pandey (457/10) Deptt. of Electronics and Communication

Akhilesh Koul (334/10) NIT Srinagar

Deptt. of Electronics and Communication

NIT Srinagar

Abstract:

Our project will be in two stages. First stage will be: building a quadcopter that

has manoeuvring capability that can move up, down, left, right, forward and

backward. The control of the quadcopter will be done using RF module i.e.

Receiver and Transmitter Module. Further the stabilization will be done using

sensors like gyro, accelerometer mounted on the board. The second stage will be:

using camera output for crowd estimation. This can be done in two ways, first

recording the data during the in-flight and processing it post flight and the second,

video transmission using live feed from the camera and processing it in real time

mode.

Quadcopter:

Quadcopter is a quad rotor based helicopter that is lifted and propelled by four

rotors. Unlike helicopters they use symmetrically pitched blades. Control of

vehicle is achieved by altering the pitch and/or rotation of one or more rotor

discs, thereby changing its torque load and thrust.

The quadcopter design was chosen for this project due to its high degree of

stability and lifting power. The design consists of a symmetrical array of four

motors commonly attached with an ‘X’ shaped frame. The rotation direction of

the motors is alternated, so opposite motors spin in the same direction, to

counteract the reaction torques produced by the rotors. This design eliminates

the need for a yaw stabilizing rotor commonly used on helicopters.

The use of multiple rotors allows the vehicle to have a large lift capacity. For our

design we will aim to build a quadcopter with a lifting force that is double its own

weight.

Applications of quadcopter:

Research platform

Quadcopters are a useful tool for university researchers to test and evaluate new ideas in a number of different fields, including flight control theory, navigation, real time systems, and robotics. In recent years many universities

have shown quadcopters performing increasingly complex aerial maneuvers. Swarms of quadcopters can hover in mid-air, in formation, autonomously perform complex flying routines such as flips, darting through hula-hoops and organise themselves to fly through windows as a group.

Military and law enforcement

Quadcopter unmanned aerial vehicles are used for surveillance and reconnaissance by military and law enforcement agencies, as well as search and rescue missions in urban environments.[22]

Commercial

The largest use of quadcopters has been in the field of aerial imagery although, in the USA, it is currently illegal to use remote controlled vehicles for commercial purposes. Quadcopter UAVs are suitable for this job because of their autonomous nature and huge cost savings. Capturing aerial imagery with a quadcopter is as simple as programming GPS coordinates and hitting the go button. Using on-board cameras, users have the option of being streamed live to the ground.

Figure 1. Prototype

Figure 2. Reaction Torque

COMPONENTS DESCRIPTION:

Brushless DC Motor: It will be used to rotate propellers which will subsequently

provide thrust, needed to lift the system. Brushless motors are used because they

provide maximum RPM.

Specifications :

Weight : 49gms

Get 700 gms Thrust

Prop. : 9x4.7E

LIPO : 2cell 7.4v

Operating voltage : 7.1v

Current Drawn at load : 15A

ESC : 20 amp

Electronic Speed Controller (ESC): They will be used to control the RPM of motor,

needed in proper manoeuvring. They are driver cum controller circuit which

consist of an on-board processor, firmware and FET’s (for switching, to provide

Pulse Width Modulated signal).

Specifications:

Weight:18g

Size:32x47x4mm

Cells:2-3S(AutoDetect)

MaxCurrent:18A

Burst:20A

Sensor: once the system is airborne it will need auto stabilization which will be

provided by gyro. Gyro gives output in the form of pitch, yaw and roll. These three

parameter will be processed in MCU and the motors will be controlled

accordingly.

Propellers: These are blades, connected to motor to provide thrust.

Battery: We shall need Lithium polymer battery to power all the four motors

since this battery provides optimum amps and power to drive the motor for a

longer flight time as compared to other batteries.

Figure 3. Quadcopter System Overview

Figure 4. Motor Control using ESC

Transmitter and receiver:

RF Module: As the quadcopter need signal for its manoeuvring, it needs RF to

transmit data(control). We shall need Rx-Tx module to send control signals

(wirelessly) to the quadcopter for its movement.

Specifications:

Receiver Transmitter

Product Model: XY-MK-5V Product Model: MX-FS-03V

Operating voltage: DC5V Operating Voltage: 3.5-12V

Receiving frequency: 433.92MHZ Transmitting frequency: 433M

MCU: The data from RF module, Sensor module are to be processed and output

signal is to be fed into ESC for motor control. All these processes and data

manipulation will be done in microcontroller unit.

Video Recording:

The choice of video system is one of the most crucial decisions for the project.

The camera needs to be light enough so that the UAV can fly unabated and

compact enough so that it does not interfere with the landing gear and rotors.

The height for our project is 50-100m.

Video Camera:

There are many different options for the camera. One of the first solutions is to

mount a camera to the fuselage of the quadcopter which would be able to

produce a high resolution image.

We will be using a CMOS camera for image acquisition which uses a CMOS

imaging chip . A CMOS imaging chip is a type of active pixel sensor which is

an image sensor consisting of an integrated circuit containing an array of pixel

sensors, each pixel containing a photo detector and an active amplifier made

using the CMOS semiconductor process. Extra circuitry next to each photo sensor

converts the light energy to a voltage. Additional circuitry on the chip may be

included to convert the voltage to digital data.

Figure 5. CMOS Camera

VIDEO ANALYSIS:

The video analysis process consists of processing the acquired video frames to

achieve the desired result which in this case is crowd estimation. Firstly, we need

to stitch the various images acquired to form a mosaic and then further

processing it assess the crowd density in a particular area. The reason behind

creating a mosaic is to increase the area under consideration.

The algorithm used in the crowd estimation is our project is canny edge detection

employing which we can detect and differentiate members of the crowd. Then

further creating the contour around the detected edges we can easily count the

number of people.

Canny Edge Detection:

In the canny edge detection algorithm, it tries to assemble the individual edge

candidate pixels into contours. These contours are formed by applying upper and

Figure 6. a) and b) Two different Images with some overlap region, c) Feature Matching using SIFT, d) Stiched Image

lower threshold to the pixel. If a pixel has a gradient larger than the upper

threshold, then it is accepted as an edge pixel; if a pixel is below the lower

threshold, it is rejected. If the pixel’s gradient is between the thresholds, then it

will be accepted only if it is connected to a pixel that is above the high threshold.

Limitations:

Though this method helps in differentiating the people in a crowd but this

increases the contour area of each individual by adding the area covered by the

shadow of the individual as well. This leads to miscalculations which is not

tolerable.

To overcome this issue, we can use crowd density estimation techniques.

Figure 7. Canny Edge Detection, selecting high and low threshold

Figure 8. In both these examples above, succesfully able to draw contours, but because of the shadows, it is giving wrong results.

Estimated Cost:

Components Price(INR)

Frame 700

Brushless Motor(4 No’s) 4x1000

Electronics Speed Controller(4 No’s) 4X700 Sensor(Gyro) 1200

Propellers(4 No’s) 4x100 Battery (LiPo) 600

RF Module 350

MCU + PCB + Other IC’s - Camera and Other Accessories -

Miscellaneous 3000

Total 13050