My problem: create a device that can take a scan of a target via a camera and a shooting rig (that I am building).
The camera is connected to a motor that rotates the camera, and this is connected to a belt that translates left/right on a rail.
Diagram: 
I leave the translation motor's speed alone and let it go fully from start to finish without giving it any other commands. However for the rotation motor I compare the desired position with the actual position and give it an error value via an error function (negative means its too slow and positive means its too fast). Depending on the magnitude of the error value I either speed up or slow down the rotation motor.
However I am not getting much success as the tracking of the target is quite inaccurate. And I made up the error function - I have been trying to tweak it using trial and error but it isn't providing satisfying results.
Anybody have tips on how to solve this either than tweaking my error function? Is there any resources (books, internet guideS) for such a Tracking Acquisition project?
