Object tracking using open-loop system
Shane from United States  [10 posts]
12 year

For a senior design project we are attempting to make an autonomous paintball turret using RoboRealm. The main issue we have to overcome is accurately tracking a moving object detected by the COG module with a  pan/tilt servo assembly. Since there will be no feedback to ensure that the paintball gun is on target we have to be especially sure of how the position of the gun on the pan/tilt assembly relates to the pixel position calculated by the COG module. Our goal as of now is to simply experiment with how the servo values relate to the pixel position of the detected object and find a ratio that relates the two. I was wondering if you have any advice or suggestions for relating the servo positions with the pixel locations?


*note: we are using the movement module to compare the first frame to all later frames and using the COG module to get the position of the a moving object.
Anonymous 12 year

Experimentation will get you a long way there to the right ratio. But you can also try keeping the camera stable and position two objects one in the extreme left and the other in the extreme right of the image. Measure the number of pixels between the center of the two objects. Then move the servo until you center those same spots in the center of the image assuming the camera is mounted on the servo. Given these two ranges i.e. the pixel distance between the extreme left and right objects and the difference of the two servo values you have the needed pixel to servo ratio.

Note while this will provide a number it may or may not be the best to use since the servo may or may not be able to replicate accurately the position. Regardless, this will be a good starting point for the system.


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