Closed loop PID

I have a ME0907 4 pole motor and an HBL1650 controller. Everything is fine in power mode, but I can\'t get much beyond 1000rpm in closed loop. It doesn\'t matter if I am using the hall sensors as feedback or the 1000 ppr encoder. The only load on the motor is a 2:1 reduction gear. Why is it unstable at higher rpms? I try different KP, KD and KI to stabilize it, but nothing seems to work. It also doesn\'t change rpm very smoothly at the lower rpms.

A couple of things work here. Very high KD (>150) and very low KI and KP (<20) works great. Smooth start, smooth transitions and good speed control. I also noticed in the manual that it says KI is most important. KI=20 and KD=0 and KP=0 also works well. Not sure what all that means, but it\'s doing what I want now.