Hi all,

I am trying to control dc motor of the DC micromotors of Faulhaber and I am using a Maxon Motor Control Servoamplifier (the ADS 50/5) which has I am using in the current mode. It has a PWM of 50kHz and a additional motor choke. In order to develop a superior position controller for my motor, I need first of all to simulate the system. But when I use the current control mode, so just applying a voltage to the driver and measuring the speed of the motor(without using any controller except than the current PI one), the responses of the speed vary from time to time, for the same "step" voltage input! Is this normal? Wouldn't have had to be an exponential response? After calculating a transfer function for the system with input=voltage to the driver and output=speed of the shaft, the system was of 2ond order with two real poles and a real zero and the response was exponential. But in practice, the response is very slow and not exactly an exponential. Can anyone explain me if this problem is caused maybe by the PWM or maybe because of the current ripple due to the motor choke? I would also appreciate if you had any other useful information or paper concerning the current control and in general the simulation of a brushed motor.

Thanks a lot.

 

If you want check current mode amp, then you need check motor current (from driver's current monitor) vs. current command and not motor speed.
Locking motor shaft (i.e. without rotation) can help you get looked transfer function. But you may use simply gain for current loop simulation.