PIDs out of control

[Ether]

Originally Posted by gpetilli

To Ether's point, I assume you are using one of the newer "absolute encoder" http://www.andymark.com/product-p/am-2899.htm for the feedback? If not, you should consider something similar that will not be damaged if you over rotate. Again, this device will have a "discontinuity" at the 360->0 point that needs special consideration.

I assumed he is indeed using a pot (as he said). Some pots have no mechanical stops, but they have a small "blind spot". If his controller is being commanded to an angle within that blind spot, I can imagine how that might make the controller go nuts, especially if his angle error computation is not finding the shortest angle.