How to control the vibration and noise of the stepper motor

In the running process of the stepper motor, it will produce noise and vibration. For these problems, what methods can we take advantage of to eliminate?

1. Avoiding the resonance zone

With the same as the synchronous motor and mechanical system, there exists natural vibration frequency. It is impossible to remove the low-frequency resonance zone. Using some solutions can curb it to some extent. So, the best method is when designing the system to avoid the resonance zone, to make a working section of the system not coincide with the resonance zone. On the other hand, the mechanical transmission system also has a resonance frequency, this frequency can not coincide with the frequency of the motor. If the two coincides, there will be a serious consequence.

2. Adding damping

The vibration of the stepper motor is energy. If the energy can be absorbed in some way, the vibration will be reduced and suppressed. There are two ways to suppress vibration damping:

1) Mechanical damping

This damping is mainly used in reluctance stepper motors, which absorbs vibration energy by generating friction. One is mechanical disc friction damping, and the other is liquid viscous friction damping, but it is high cost, more complicated. At present, in high power reluctance stepper motor, mechanical disc friction damping is widely used.

2) Internal damping

All the stepper motor has internal damping. This because when the motor vibrates, there will be an electric potential in stator windings. Under the action of electrical potential, it will generate a current which will generate a torque when it interacts with the rotor. And this torque is opposite to the direction of the rotor movement, which acts as ad damper. In essence, the vibration energy is converted into electrical energy and absorbed, thereby suppressing vibration. The reactive steppe motor has small internal damping and its ability to suppress damping is limited. So, an external mechanical damper is required. Permanent magnet and hybrid type have permanent magnet steel, which has large internal damping and can effectively suppress dampers. Commonly, this motor does not need a damper. Although it vibrates, it will lose steps.

3) Adjust the natural vibration frequency

In some systems, due to the requirements of the working speed. The motor works in the resonance area. What’s more, the resonance of the load is close to the resonance frequency of the motor. To suppress resonance, only using methods to change the resonance frequency of the system.

The resonance frequency is:

Tm is the holding torque of the motor. Zr is the number of the tooth of the rotor. J is the moment inertia of the system. There are two ways to change f0: one is to change the moment inertia J. The most effective method is to increase or decrease the moment inertia before the reducer. Commonly, the method is to increase inertia. From (1): when the f0 decreases, and move it out of the working section. This method will decrease the starting frequency of the motor. But it has little impact on operation frequency. The other is to decrease or increase Tm, it can be completed by adjusting the windings current. Increasing the current will increase Tm. The increase of Tm is limited by the saturation of the magnetic circuit. Decreasing current will make Tm decrease. This will reduce the starting frequency and operation frequency. Which measure uses should adopt should depend on the overall load situation.

4) Using subdivision circuit

Using subdivided flow, the step angle of the motor is reduced, the amplitude is reduced. Although the vibration can be reduced, it can not completely be eliminated.

5) Eliminate electromagnetic asymmetry

(1) Motor design

When the motor works, reducing the value of static current and setting the value of constant current can reduce the torque asymmetry generated by magnetic saturation and reduce the vibration and noise.

(2) Windings parameter should be symmetric

(3) Choose a reasonable driving mode. The four-phase(two-phase) motor uses a double four-beat energization mode. Five phase motor uses 4-4 energization mode and subdivides on this basis.

(4) The parameters of each phase of the driver should be symmetrical and consistent.

(5) Process measures

Improve the concentricity of the stator and rotor.

The motor stator and rotor are axially centered.

Eliminating the axial gap and uses an elastic cushion.