How to avoid resonance issues in stepper motors?
Montag, 4. November 2019
Stepper motors are unique among electronic motors in that they move in a series of discrete steps (hence their name) rather than a continuous motion. This is a useful property since it allows steppers to have positional and velocity control that is both accurate and easy and doesn’t even require feedback to maintain (under normal operation).
However, one of the primary disadvantages of this style of motor comes as a direct result of this discrete nature and open loop control.
Since steppers are typically run in open loop, the controller has no knowledge of these missed steps; The result is the motor will not get to its destination successfully. The effect can become so pronounced that the nema 23 stepper motor loses torque completely and stops rotating. Depending on the synchronization of the steps, it can even reverse the direction of rotation.
First, this phenomenon is only problematic at the stepper’s natural frequency. This means that it will only be at work in a certain velocity band. Depending on what speeds you are running your motor at, you may never even notice it at all!
Second, the resonance takes time to build up. It’s not like you will hit a bad velocity and immediately lose torque. The oscillations will take a few seconds to get to the troublesome levels. Since this issue only crops up at certain velocities, you can typically accelerate through a bad region and emerge unaffected on the other side. You are only at risk if you are staying in the bad region for extended periods of time. (Click here to buy cnc stepper motor kit)
Finally, this effect is greatly reduced by having load on the motor. If the motor has load on it, then the inertia is much greater and the oscillations will be reduced substantially.