28 Jun 2002 motters   » (Master)

Have been testing out the visual tracking on Rodney. I switched off all his other behaviors, effectively bringing him to a complete stop except for the tracking routine.

Waiving a toy in front of the robot, it is actually trying to follow it at slow speed. I can see that the fovea region is continuously focused on the object. Unfortunately the robot's head tracks the object for a short time, then moves back again. At first I thought this was just too much gain, but no amount of tuning seemed to alleviate the problem.

What's actually happening is a sort of battle of the optical flows. The vision system is seeing a flow in one direction and initiates the command to move the robot's head, but then when the head moves this produces an apparent optical flow in the *opposite* direction. This causes the annoying back and forth behavior.

At the moment I'm not quite sure how to get around this problem. I don't really want the robot to ignore everything while it's head is moving because this is supposed to be a slow speed tracking mechanism independent from the ballistic trajectory system which already works ok for big movements. I think some sort of predictive mechanism is needed to anticipate the self-induced optical flow produced by the robot's own movement.

- Bob

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