What Is the Cause of Servo Motor Jitter?

Under which conditions will the servo motor shake? How to solve these problems caused by servo motor jitter? How are they solved?

For example: if the acceleration and deceleration time is set too small, the servo motor will produce high inertia jitter when it suddenly starts or stops… Increasing the acceleration and deceleration time can solve this problem.

The following is an analysis of the causes of servo motor jitter by netizens for your reference.

Viewpoint 1

When the servo motor jitters at zero speed, the gain should be set high to reduce the gain value.

If the alarm stops when the motor starts, the most possible reason is that the motor phase sequence is not correct.

Viewpoint 2

  • When the PID gain adjustment is too large, it is easy to cause motor jitter, especially after adding D, which is particularly serious, so try to increase P and reduce I, and it is better not to add D.
  • When the encoder is wrongly connected, jitter will also occur.
  • If the load inertia is too large, replace the larger motor and driver.
  • The disturbance of analog input port causes jitter, and the magnetic ring is added to the motor input line and the servo driver power input line to keep the signal line away from the power line.
  • There is also a rotary encoder interface motor, poor grounding is easy to cause vibration.

What Is The Cause Of Servo Motor Jitter?

Viewpoint 3

① Servo wiring:

  • Use standard power cable, encoder cable, control cable and check whether the cable is damaged;
  • Check whether there is interference source near the control line, whether it is parallel to or too close to the nearby high current power cable;
  • Check whether there is any change in the potential of the grounding terminal to ensure good grounding.

② Servo parameters:

  • The servo gain setting is too large, so it is recommended to adjust the servo parameters manually or automatically;
  • Confirm the setting of the time constant of the speed feedback filter. The initial value is 0. Try to increase the setting value;
  • The setting of electronic gear ratio is too large, so it is recommended to return to the factory setting;
  • Try to adjust the frequency and amplitude of harmonic filter.

③ Mechanical system:

  • The coupling connecting the motor shaft and the equipment system is offset, and the mounting screw is not tightened;
  • Poor engagement of pulley or gear will also lead to load torque variation. Try to run without load. If it is normal during no-load operation, check whether the joint part of mechanical system is abnormal;
  • Confirm whether the load inertia, torque and speed are too large, and try to run without load. If the no-load operation is normal, reduce the load or replace the driver and motor with larger capacity.

Servo wiring

Viewpoint 4

Servo motor jitter is caused by mechanical structure, speed loop, compensation board and servo amplifier of servo system, load inertia, electrical part etc.


1. The vibration caused by mechanical structure can be divided into two cases

1) No load jitter:

  • The motor foundation is not firm, the rigidity is not enough or the fixation is not tight.
  • The fan blade is damaged, which destroys the mechanical balance of the rotor.
  • The shaft is bent or cracked. It can be solved by fastening screw, replacing fan blade and shaft.

2) If the vibration occurs after loading, it is generally caused by the failure of the transmission device.

It can be judged that there are defects in the following parts:

  • The rotation of belt pulley or coupling is unbalanced.
  • The central line of the coupling is inconsistent, so that the motor and the mechanical axis are not coincident.
  • The transmission belt joint is unbalanced. It can be solved by adjusting the transmission device to make it balance.

2. Jitter caused by speed loop problem

The integral gain, proportional gain and acceleration feedback gain of the velocity loop are improper.

The greater the gain, the greater the velocity, the greater the inertia force and the smaller the deviation, the easier the jitter will occur.

Setting a small gain can maintain the speed response and is not easy to produce jitter.

3. Jitter caused by fault of compensation board and servo amplifier of servo system

The motor stops suddenly when it is in motion, resulting in great jitter, which is related to the improper BRK terminal of servo amplifier and setting parameters.

The time constant of acceleration and deceleration can be increased, and the motor can be started or stopped slowly by PLC to make it not shake.

4. Jitter caused by load inertia

The problem of guide rail and screw causes the load inertia to increase.

The moment of inertia of guide rail and lead screw has great influence on the rigidity of servo motor drive system

Under the fixed gain, the larger the moment of inertia is, the greater the rigidity is, and the easier it is to cause motor jitter;

The smaller the moment of inertia is, the smaller the rigidity is, and the less likely the motor is to shake.

By changing the guide rail and screw rod with smaller diameter, the moment of inertia can be reduced, so as to reduce the load inertia, so that the motor does not shake.

5. Jitter caused by electrical part

  • The brake is not opened, and the feedback voltage is unstable.

Check whether the brake is turned on, add the encoder vector control zero servo function, and output a certain torque by reducing the torque to solve the jitter.

If the feedback voltage is abnormal, check whether the vibration period is related to the speed

If so, check whether the connection between the spindle and the spindle motor is faulty, and whether the spindle and the pulse generator installed at the tail of the AC spindle motor are damaged

If not, check if there is any fault on the printed circuit board, check the circuit board or readjust it.

  • The sudden jitter of the motor during operation is mostly caused by the lack of phase. It is necessary to check whether the fuse melts, whether the switch contacts well, and whether each phase of the power grid has power.

Final thoughts

With the analysis of these netizens, do you have a general understanding of the causes of servo motor jitter?

When encounter this kind of circumstance, can carry on the investigation according to the reason in the netizen viewpoint analysis.

In addition, we can also pay attention to these problems to avoid the vibration of the servo motor.

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