PID with geartrains

I am using the integrated motor encoders on my arm this year and it has 6 motors on it. I can get it to work as a encoder but I can never get the PID to work smoothly am I doing somthing wrong? I use RobotC, Thanks in advance.

I would avoid the ROBOTC built in PID for this type of application, however, as with all PID control loops, the trick is in the tuning, that is, you need to find the correct values of the three fundamental constants used in the algorithm, Kp, Ki and Kd. So you are probably not doing anything wrong but will need to experiment and test until you find the correct values for your specific arm system.