Disabling PID loop on SMC03A or introducing a dead zone

Support Motor controllers/drivers and motors
1

I have the following issue:

I want to control a linear moving DC motor based on the feedback from a pod meter. The problem is that whenever the controller is slowing the motor down it starts to make a horrible peeping noise (caused by the PWM frequency of the controller) and since the error never gets to zero, this peep is constant untill the next command is issued. I trieed to find better settings for the PID controller such that it would reach the perfect position but I was out of luck.

We identified the following solutions:

  • Get the PID to accept a small error and stop sending commands to the motor
  • Disable the PID and replace it with an alogrithm that just moves to the disered position and turns the motor of (the motor is relativly slow and responds immidiatly to the command PID is therefor not necesary)
  • Switch online to speed control wait for a period long enough to make sure that the pid algorithm is in its final fase (and effectivly only making noise and not moving the motor) and send a zero speed command

The interface to the SMC03A does however not support any of these opperations, do you have any suggestions?

2

Hello.

Unfortunately, the SMC03A does not have the features you are looking for. What is the volume for your application? If it’s large enough, we might be able to customize the motor controller for you. Otherwise, you might consider the more advanced SMC04, which can do 20 kHz PWM and avoid the whine.

- Jan

3

Hi Jan thanks for your reply but we require that our motor is operated at 24V, 3A which is out of specs for this chip. We are working on a demonstration project and the size therefore does not justify a costumised solution. Do you have any other solutions?

4

We don’t have much to offer at 24V right now. If your 3A is a maximum, our MC33887 carrier might at least give you a motor driver to which you could add a control loop. We plan on having higher-current 24V motor drivers and controllers later this year, with the first driver coming out in about a month, but I don’t know if that will fit your schedule.

- Jan