C:/Users/Michael/Desktop/trunk/program/demo/runfollowball.h File Reference

Following balls using the camera. More...

Functions
void	run_follow_ball (void)
	The "main" function to follow all the balls.
void	run_follow_ball_green (void)
	The "main" function to follow the green ball.
void	run_follow_ball_red (void)
	The "main" function to follow the red ball.

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Detailed Description

Following balls using the camera.

Introduction

This demo show you how you can drive the camera to make vision based algorithmes. This programm uses the camera to follow balls. There are three differents configurations:

• Following the green balls: put the selector on position 6. Now the e-puck will follow the first green ball he saw indifferently of the color.
• Following the red balls: put the selector on position 7. Now the e-puck will follow the first red ball he saw indifferently of the color.
• Following all the balls: put the selector on position 8. Now the e-puck will follow the first ball he saw indifferently of the color.
  

How it works

The goal of this programm is to search a ball, when one is found the e-puck has to go in it direction and has to stop at a specified distance. This is done by the following steps:

• First of all we have to capture an image. The image is 4 pixels height and 480 pixels width. We take one pixel each for pixels then the image is finally 1 pixel height and 120 pixels width => stored in array 1x120.
• We normalize the array to 10 (the mean value of the array is now ten).
• We search a pic in the array which correspond of a ball (look at the picture below to see how is the values when a ball is detected).
• We work with the motors to do two thinks at the same time: 1) to put this pic on the center of the array => it would place the e-puck across the ball; 2) to adjust the thickness of this pic at the desired value => it would place the e-puck on the good distance of the ball. To have the best control we use a PI (proportionnal intergral) regulator.

The graphe of the array when a ball is detected

Playing the follower

When we want to follow all the balls, the camera is used in gray scale mode.
When we want to follow the green ball for exemple, the camera is used in color mode. In color mode, we have three values: 1 for the red, 1 one for the green, 1 for the blue. Then to follow the green ball we only have to take the red constituent, because the value of green in the red constituent is near zero => it makes a pic in the array.
When we want to follow the red ball, it's the same principle: we take the green constituent,...

Playing the demo

The programm works with the contrast of the color between the ball and the environement, so to have the best result you should place the e-puck in an arena which has white wall and good luminosity.
To play the demo select the configuration you want (follow all, green, red balls) and let's go. The e-puck will turn on himself until he finds a ball.

Video of the demo

• Following all the balls: http://www.youtube.com/watch?v=Pga71leqf1A
• Following the green balls: http://www.youtube.com/watch?v=FGXBy9FOnmw

Author:

Jonathan Besuchet

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