Problem solving

Relevant parameters of integrated servo motor PID tuning
Release Date : 2021-07-17 17:10:08



The integrated low-voltage servo motor consists of three control loops, from the inside to the outside are the current loop, the speed loop and the position loop. The response frequency of the current loop is the highest.
The factory default current loop gain parameters of the servo motor have ensured sufficient responsiveness and generally do not need to be adjusted. Therefore, the position loop gain, speed loop gain, speed loop integral time constant, speed feedforward, speed feedforward filter time constant and Torque command filter time constant.
 
 
In order to ensure the stability of the system, it is necessary to increase the gain of the speed loop while increasing the gain of the position loop.
 
Speed ??loop gain: The speed loop gain directly determines the response bandwidth of the speed loop. In the case that the mechanical system does not produce resonance or noise, increase the speed loop gain, the faster the speed response will be and the better the speed followability. However, excessive speed loop gain will cause mechanical resonance.
 
Speed ??loop integral time constant: The speed loop integral time constant can effectively eliminate the steady-state error of speed and quickly react to subtle speed changes. When the mechanical system does not produce resonance or noise, reducing the integral time constant of the speed loop can increase the rigidity of the system and reduce the steady-state error. If the load inertia ratio is large or there are resonance factors in the mechanical system, the integral time constant of the speed loop must be increased to reduce the integral effect, otherwise the mechanical system is prone to resonance.
 
Position loop gain: The position loop gain directly determines the response speed of the position loop. When the mechanical system does not produce resonance or noise, increase the position loop gain to reduce the position tracking error and shorten the positioning time. But too large position loop gain can also cause mechanical system jitter or positioning overshoot.
 
Torque command filtering time constant: low-pass filtering of the torque command can make the torque command smoother and reduce vibration. The low-pass filter has a good attenuation of high frequency, can better suppress high frequency oscillation and noise, but has no effect on middle and low frequency resonance.
 
Speed ??feedforward: improve speed command response, reduce position deviation at fixed speed, mainly used in full closed loop position control mode. Set the speed feedforward filter time constant to a fixed value (usually set to 100-200ms); then, gradually increase the speed feedforward setting value from 0 until a certain setting value, the speed feedforward effect .
 
Torque feed forward: In non-torque mode, increasing this parameter can improve the response to changing speed commands and position command response, and reduce the position deviation at fixed speed. Generally, no adjustment is required.



 
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