Servo Motor Troubleshooting and Failure Analysis

Servo motor does not run when the pulse is output

1. Monitor the current pulse output value of controller and check if pulse output indicator lamp flashes to confirm that the controller has performed command pulse and has output pulse normally.
2. Check if the control cable, power cable, encoder cable between controller and driver are matched incorrectly damaged or contacted poorly.
3. Check if the brake of servo motor equipped with brake has been turned on.
4. Monitor the panel of servo driver to confirm if the pulse command has been input.
5. Run command is normal.
6. For control mode, always choose position control mode.
7. Check if the type of input pulse set by servo driver matches with that of command pulse.
8. Ensure that positive side drive prohibition, negative side drive prohibition signals and deviation counter reset signal are not input and the servo motor runs normally if load is removed, then check the mechanical system.

Overrun errors occur in motor deviation counter when servo motor rotates at high speed

1. Overrun errors occur in motor deviation counter when servo motor rotates at high speed.
   Countermeasure:
   Check if wirings of motor power cable and encoder cable match correctly and if there is any damage in cables.
2. Overrun errors occur in motor deviation counter when much longer command pulse is input.
   Countermeasure:
   a. Gain setting is too large. Manually adjust gain setting again or use automatic adjustment gain setting function.
   b. Prolong the acceleration/deceleration time.
   c. The load is too heavy. It is necessary to choose another motor with larger capacity or reduce the load, install speed
   reducer or other drive mechanism, so as to improve load capacity.
3. Overrun errors occur in motor deviation counter during operation.
   Countermeasure:
   a. Increase the overrun level set value of deviation counter.
   b. Reduce the rotation speed.
   c. Prolong the acceleration/deceleration time.
   d. The load is too heavy. It is necessary to choose another motor with larger capacity or reduce the load, install speed 
   reducer or other drive mechanism, so as to improve load capacity.

Overload is reported when servo motor runs without any load

1. If the condition occurs when servo run signal is access and there is no pulse:
   a. Check if the wiring of servo motor power cable is contacted poorly or there is any damage in cable.
   b. For servo motor with brake, always turn on the brake.
   c. If the speed circuit gain is set too large.
   d. If the integral time constant of speed circuit is set too large.
2. If the condition only occur during operation:
   a. If the position circuit gain is set too large.
   b. If the locating completion amplitude is set too small.
   c. Check that there is no stall on servo motor shaft and adjust the mechanism system again.

Abnormal noise or shaking occurs when servo motor is running

1. Servo wiring:
   a. Use the standard power cable, encoder cable and control cables and check if there is any damage in cables.
   b. Check if there is any interference source near the control wires and if the wires are parallel or too close to nearby
   high current power cables.
   c. Check if ground terminal potential has changed and ensure that grounding is in good condition.
2. Servo parameter:
   a. Servo gain is set too large. It is suggested to use manual or automatic way to adjust servo parameter again.
   b. Confirm that time constant for speed feedback filter is set at 0 as initial value and attempt to increase the set value.
   c. Electronic gear ratio is set too large. It is suggested to restore the factory setting.
   d. The servo system resonates with the mechanical system. Attempt to adjust the frequency and amplitude of notch filter.
3. Mechanical system:
   a. Deviation occurs in coupling connecting motor shaft and equipment system and mounting screws are not tightened firmly.
   b. Poor engagement of pulley or gear may also cause load torque change. Attempt to run without load. If the system operates normally without load, check if the engaged part of mechanical system has any abnormality.
   c. Confirm if load inertia, torque and speed are too large. Attempt to run without load. If the system operates normally without load, reduce the load or replace another driver and motor with large capacity.

The position control positioning of servo motor is inaccurately

1. First confirm if the current pulse value actual sent from controller is the same as anticipated. If not, perform inspection and correct the procedure.
2. Monitor if the number of pulse commands received by servo driver matches that from controller. If not, check the control wire cable.