Servosphere
Owen Loh and Erik Cruz built a "servosphere" for an insect. It's a two dimensional treadmill.

 

A webcam images the sphere from the top. The sphere can be rotated around two horizontal axes by rollers driven by servomotors.

An insect is placed on the top of the sphere

This is the image from the webcam, as captured by a matlab program...

...and thresholded. The centroid of the darkness distribution is computed, and the deviation from the center of the image is used as a velocity command to the servomotors.

 

Soon we'll put a video of a bug running.

Matlab code and other technical info.