THE BALL FOLLOWER BOT

AN AUTONOMOUS IMAGE PROCESSING PROJECTWinter Workshop 2009 Technology Robotics Society IIT Kharagpur

Problem Statement:Build an autonomous bot that can track a ball' s motion and follow it.

Group Heads:Pinaki Ghosh Rahul Das Subhagato Dutta

Group Members:Bharath Mahadevan Deepit Purkayastha Hindole Dutta Nitin Nagwani Nilanjana Bhattacharya Aiyush Suhasaria Anirban Majumdar Ayan Chattopadhyay

Software Used:1. Microsoft Visual Studio 2008 :Microsoft Visual Studio is an Integrated Development Environment (IDE) from Microsoft. It can be used to develop console user interface applications along with Windows Forms applications, web sites, web applications, and web services in both native code together with managed code for all platforms supported by Microsoft Windows, Windows Mobile, Windows CE, .NET Framework, .NET Compact Framework and Microsoft Silverlight. Visual Studio includes a code editor supporting IntelliSense as well as code

refactoring. The integrated debugger works both as a source-level debugger and a machine-level debugger. Visual Studio supports languages by means of language services, which allow any programming language to be supported (to varying degrees) by the code editor and debugger, provided a language-specific service has been authored. Built-in languages include C/C++ (via Visual C++), VB.NET (via Visual Basic .NET), and C# (via Visual C#). Support for other languages such as F#, M, Python, and Rubyamong others has been made available via language services which are to be installed separately. It also supports XML/XSLT,HTML/XHTML, JavaScript and CSS.

2.Microsoft Visual C++ 2005 :Microsoft Visual C++ (often abbreviated as MSVC) is a commercial integrated development environment (IDE) product engineered by Microsoftfor the C, C++, and C++/CLI programming languages. It has tools for developing and debugging C++ code, especially code written for theMicrosoft Windows API, the DirectX API, and the Microsoft .NET Framework.

3. OpenCV 1.1Pre1A :OpenCV is a computer vision library originally developed by Intel. It is free for use under the open source BSD license. The library is cross-platform. It focuses mainly on real-time image processing, as such, if it finds Intel's Integrated Performance Primitives on the system, it will use these commercial optimized routines to accelerate itself. One of OpenCVs goals is to provide a simple-to-use computer vision infrastructure that helps people build fairly sophisticated vision applications quickly.

4. Serial Communication:The header file tserial.h was used to enable serial communication

5.

WinAVR:

WinAVR was used to write the operating program for the bot to run on.

Hardware Used:1. Rectifier Circuit:The power supply is derived from the AC main supply of 220 V. A rectifier circuit is used to generate constant DC power supply of 12V to the bot. The circuit is as

As can be seen, the circuit constitutes: A Step Down Transformer Two Diodes One Capacitor

The circuit basically generates a fully rectified wave out of the input AC wave . The capacitance is used to smooth out the generated curve. So the waveforms are as:Input waveform:

Output waveform:

IC 7812:The bot requires constant DC supply yet the output from the rectifier circuit still has ripples. Hence the IC 7812 is used which makes the output exactly 12V.

2. L293D The Motor Driver CircuitThe L293D circuit is used to run two motors that control the motion of the bot. It is a current amplifying circuit. A low current control signal is converted into a higher current signal which can be used to drive a motor.

The L293D has two H-bridge circuits inbuilt in it. Each H-bridge circuit controls one motor. Each H bridge circuit is configured as follows:

The direction of motion of the motor is given by the switching on and off of the switches S1, S2, S3 and S4.

3. Development Board :

We used an ATMEGA16 microcontroller in the development board to control the motion of the bot. Some of the important features of the ATMEGA16 are: 16-Kbyte self-programming Flash Program Memory, 1-Kbyte SRAM, 512 Byte EEPROM, 8 Channel 10-bit A/D-converter.J

TAG interface for on-chip-debug. Up to 16 MIPS throughput at 16 Mhz.

A MAX232 IC was used to perform the serial communication. The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the RX, TX, CTS and RTS signals. An external 16 MHz crystal is being used to generate a system speed of 16 MHz.

4. Motors:Two DC motors of 45 rpm each have been used in the bot running on a constant DC supply of 12V.

5. Camera: iBall Face2Face C8.0

The camera is mounted on the bot to take images of the ball to be followed continuously.

6.

USB 232 Converter:

It allows serial communication between the bot and the laptop.

ALGORITHM:We use the laptop as the image processing device in order to track the images that are taken by the camera mounted on our bot. Lets take a look at the stepwise algorithm now: 1. The camera on the bot begins taking a continuous video stream of the ball in the form of still frames one after the other. 2. Processing The Frame: At each frame, the colour image taken as input is converted into a grayscale image. Grayscaling: Every frame is divided into pixels. Each pixel sends a set of properties which can be read through functions provided in OpenCV. The RGB values of each pixel is read by the code and using the cvCvtColor() function we convert the colour image into gray image. In the next step, the grayscale image is converted into a binary image using the cvThreshold() function. Setting the Threshold: The threshold was set as 250 putting it close to the maximum value 255 so as to make the pixels with intensity value close to 255 prominent. Making the Binary Image: The cvCvtColor() function is called with Threshold value 250 and threshold

type CV_THRESH_BINARY. This creates a binary image of the entered frame. Now, the unwanted noises in the frame are removed and the largest white patch in the image is found. The centre of the largest white patch in the image is computed.

3.

Function to find the direction in which the bot should move: The distance between the centre of the screen and the centre of the largest white patch is calculated both in the vertical and horizontal directions. If yscreen> ypatch,,, then the bot moves in the backward direction. If yscreen< ypatch,,, then the bot moves in the forward direction. If xscreen> xpatch,,, then the bot moves in the right direction. If xscreen