motor control ... howto ?

[proton]

Hi,
I'm designing a control system for a motor, used in a dish positioning system.
The motor has to go to a certain angular position given by a compass sensor and keep
the position even if the base moves.
I've been using stepping motors and also fast microstepping motors.
Every 10 ms I sample the compass and define the speed of the motor to be proportional to the angular difference of the set point towards the actual position (defining however an acceleration curve). What I see is that the dish remains
always a little bit behind ... I've also tried to use a PID control, but even in this case I do not get good results (oscillations etc etc)
May ask suggestions on which is the right control algorithm to use ? I'm evaluating
thinks like autotuning PIDs with neural networks, but there are many other possibilities and I'd like to have an hint before starting. 10 ms is too low ?
thanks a lot
proton

 

[artem]

I am not a expert in this field but may be Kalman filter?

And is you motor constantly rotating ? If so may it be 10 ms is too long ?

 

[proton]

yes thanks. kalman is a possibility, but does someone has a sample code
or a sort of example that I could follow _
thanks
proton

 

[artem]

not exactly your case , but could be useful :
http://www.standardics.nxp.com/support/documents/microcontrollers/pdf/an715.pdf

 

[ronyutp]

I think your might have problems with motor axis static friction. You could try to compensate it. The following book could be helpful for you:

Adaptive Control of Systems with Actuator and Sensor Nonlinearities.

G. Tao, P. Kokotovic.
John Wiley & Sons, Inc. 1996