I am currently working on a controller that aims to control a cart that moves 200mm in x-direction. It is driven by a linear motor that is connected to a geared belt. The belt is connected to a cart (0.5kg) that slides on a rail. The cart has to make a cycle of 200mm in 0.9 seconds. It takes 0.05s to accelerate, then travels at constant speed until it reaches the end, decelerates and does the same thing on its way back. During the constant speed an accuracy of 10micron has to be achieved. I am currently stuck at 30 micron and am left with a high frequency vibration. I am using a PID controller and feed forward. The crossover frequency can not be raised due to stability. See the attached figure for the error.
Any ideas on how to remove the vibration? I was thinking it might be due to possible vibrations of the belt.