I am trying to implment a bidirectional PWM based control strategy for a BLDC motor.

I have implemented three stage cascade control
Outer loop: Position Control: P Controller
Middle Loop: Speed Control: PI Control
Inner Loop: Current Control: PI Control

I am having problem in designing for bi-directional rotation of motor. Could you please suggest strategy for use in inner loop so that I am able to turn the motor in both directions for precisely controlling an actuator?

Also is my choice of controllers for the loops in cascade control ok? If not please advise.

 

1. As you may see from previous postings, design of current loop for BLDC motor isn't simply. The servo amp in current mode would be suggested - for example from Elmo (http://www.elmomc.com).

2.The structure without velocity loop maybe suggested for your design including PI-filter for current loop and PID-filtewr for position loop - see for example Galil motion controllers (http://www.galilmc.com).

 

Is this for some kind of college or technical school assignment?

No disrespect, but I see these kinds of posts on a regular basis and wonder why anyone would want to design/build an amplifier that you can purchase from any number of sources for far less $ and time than it would take to develop from scratch.

Buy something off the shelf - install it, commission it and take all the time and $$ you saved and spend it on your spouse if you are married or your parents in a show of gratitude.

If it is a college assignment... please state this up front so we have context for the question.

Thanks,

Ken Brown
Applied Motion Systems, Inc.