Tips to Avoid Stepper Motor Resonance Problems

When an application requires a reliable, low-cost motor with simple operation, stepper motors can be hard to beat. They can be driven step by step without needing an encoder or Hall sensor for rotor position feedback. However, the same straightforward design and driving method that makes stepper motors popular can lead to resonance problems in certain conditions.

Resonance can lead to erratic operation of the motor, loss of steps and random changes to its rotational direction. We recommend you take preventive measures to avoid resonance and ensure proper synchronicity between the driver and the actual rotor position. Here are some different ways to avoid resonance issues and ensure trouble-free motion:

Avoid natural frequency. The most basic way to prevent the occurrence of resonance is to keep the commutation frequency away from the system’s natural frequency. Avoiding the natural frequency can cause the motor speed to adapt the commutation frequency and allow some application changes that are otherwise not typically possible.

•	Shift natural frequency. Instead of changing the commutation frequency, we recommend shifting the natural frequency higher or lower in order to prevent the commutation frequency from matching it. This can be done by working on the two factors that influence the natural frequency: the holding torque and the total inertia in the system.
•	Lower the holding torque. Using a higher current to increase the holding torque is not possible for a continuous operation, but a lower current can be used to achieve a lower holding torque and to shift the natural frequency down if the lower torque can meet the application’s needs.
•	Inertia changes. Increasing the inertia will shift the overall system’s natural frequency down, and vice-versa. Changing the system’s inertia can also affect the motor’s performance in the application. Be sure to check the motor’s specifications consult with the supplier to ensure proper operation.
•	Microstepping. Microsteps have a smaller step angle and require less energy to move from one stable position to the next. Because the target position overshoot is smaller along with the magnitude of the oscillation, microstepping can be an effective way to avoid resonance.
•	Damping via friction. Friction provides a braking torque that is opposed to the instant direction of rotation. This torque is constant, regardless of motor speed. While it helps dampen the oscillation and prevents resonance, the motor must provide sufficient performance when adding friction to prevent resonance. Viscous friction also provides a braking torque, but its magnitude depends on the motor speed and is desirable for oscillation damping within a very short time and without adding too much load onto the motor.

Work With Your Motor Provider

While stepper motors offer easy and cost-effective positioning, their step-by-step, sequential operation can lead to resonance issues under certain conditions apart from natural oscillation frequency. Motor providers can help you determine the frequency ranges that are likely to trigger resonance and offer solutions to prevent the issues from occurring.

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