speed-based tracking

edit

Or simpler, if you are using openni.

[EDIT] : the pi_tracker is the one I meant. Openni tracker only gives transforms, not coordinate of the joints.

If you have a look at the tracker file, you'll see that you can access to the points coordinates. Then computing a velocity is the easy part. However, I have no idea how to command your motors (but I hope you know it ;-) )

To access the points, it easy : make a listener, then access the parts you are interested in :

for each joint (here corresponding to index k), you have the following fields

msg.position[k].x
msg.position[k].y
msg.position[k].z
msg.orientation[k].x
msg.orientation[k].y
msg.orientation[k].z
msg.orientation[k].w

[EDIT 2 ] = the pi_tracker has already something to command velocity for a robot, based on joint velocity....

I hope it'll help you,

Bests,

Steph