How to set the parameters of the servo motor?

Servo motors are often used in automation equipment, especially position control. Most brands of servo motors have position control functions. The controller sends pulses to control the operation of the servo motor. The number of pulses corresponds to the angle of rotation, and the pulse frequency corresponds to the speed (related to the electronic gear setting). When a new system and the parameters do not work, first set the position gain to ensure that the motor is noiseless and try to set it as large as possible. The moment of inertia ratio is also very important and can be used as a reference through the number set by self-learning.

Then set the speed gain and speed integral time to ensure continuous operation at low speed and controlled position accuracy.

(1) Position proportional gain

Set the proportional gain of the position loop regulator. The larger the setting value, the higher the gain, the greater the stiffness, and the smaller the position lag under the same frequency command pulse condition. However, too large a value may cause oscillation or overshoot. The parameter value is determined by the specific servo system model and load conditions.

(2) Position feedforward gain

Set the feedforward gain of the position loop. The larger the setting value, the smaller the position lag is under any frequency of the command pulse. The larger the feedforward gain of the position loop is, the higher the high-speed response characteristics of the control system are, but it will make the position of the system unstable and prone to oscillation. When a very high response characteristic is not required, this parameter is usually set to 0. Range: 0~100%

(3) Speed ​​proportional gain

Set the proportional gain of the speed regulator. The larger the setting value, the higher the gain and the greater the stiffness. The parameter value is determined according to the specific servo drive system model and load value. In general, the larger the load inertia, the larger the setting value. Under the condition that the system does not produce oscillation, try to set a larger value.

(4) Velocity integration time constant

Set the integral time constant of the speed regulator. The smaller the setting value, the faster the integral speed. The parameter value is determined according to the specific servo drive system model and load conditions. Generally, the larger the load inertia, the larger the setting value. Under the condition that the system does not produce oscillation, try to set a smaller value.

(5) Speed ​​feedback filter factor

Set the speed feedback low-pass filter characteristics. The larger the value, the lower the cut-off frequency and the less noise the motor generates. If the load inertia is large, the set value can be appropriately reduced. If the value is too large, the response will be slow and may cause oscillation. The smaller the value, the higher the cut-off frequency and the faster the speed feedback response. If a higher speed response is required, the set value can be appropriately reduced.

(6) Maximum output torque setting

Set the internal torque limit value of the servo drive. The setting value is a percentage of the rated torque. This limit is valid at any time. Positioning completion range sets the positioning completion pulse range under position control mode. This parameter provides the basis for the drive to determine whether positioning is completed under position control mode. When the number of remaining pulses in the position deviation counter is less than or equal to the setting value of this parameter, the drive considers that positioning is completed and the in-place switch signal is ON, otherwise it is OFF.

In position control mode, the output position positioning completion signal, the acceleration and deceleration time constant setting value represents the acceleration time of the motor from 02000r/min or the deceleration time from 20000r/min. The acceleration and deceleration characteristics are linear. The arrival speed range is set to the arrival speed. In non-position control mode, if the servo motor speed exceeds this setting value, the speed arrival switch signal is ON, otherwise it is OFF. In position control mode, this parameter is not used. It has nothing to do with the direction of rotation.

(7) Manually adjust the gain parameters

Adjust the speed proportional gain KVP value. After the servo system is installed, the parameters must be adjusted to make the system rotate stably. First adjust the speed proportional gain KVP value. Before adjustment, the integral gain KVI and the differential gain KVD must be adjusted to zero, and then the KVP value is gradually increased; at the same time, observe whether the servo motor produces oscillation when it stops, and adjust the KVP parameter manually to observe whether the rotation speed is obviously fast and slow. When the KVP value is increased to produce the above phenomenon, the KVP value must be adjusted back to a smaller value to eliminate the oscillation and stabilize the rotation speed. The KVP value at this time is the initially determined parameter value. If necessary, after adjusting KVI and KVD, it can be repeatedly corrected to reach the ideal value.

Adjust the integral gain KVI value. Gradually increase the integral gain KVI value to gradually produce the integral effect. From the above introduction to integral control, it can be seen that when the KVP value increases to the critical value with the integral effect, oscillation will occur and it will be unstable. Just like the KVP value, adjust the KVI value back to a smaller value to eliminate the oscillation and stabilize the rotation speed. The KVI value at this time is the initially determined parameter value.

Adjust the differential gain KVD value. The main purpose of the differential gain is to make the speed rotation stable and reduce the overshoot. Therefore, gradually increasing the KVD value can improve the speed stability.

Adjust the position proportional gain KPP value. If the KPP value is adjusted too large, the motor positioning overshoot will be too large when the servo motor is positioned, causing instability. At this time, the KPP value must be adjusted down to reduce the overshoot and avoid the unstable area; but it cannot be adjusted too small to reduce the positioning efficiency. Therefore, you should be careful when adjusting.

(8) Automatically adjust gain parameters

Modern servo drives are all microcomputerized, and most of them provide automatic gain adjustment (autotuning) function, which can cope with most load conditions. When adjusting parameters, you can use the automatic parameter adjustment function first, and then adjust manually when necessary.

In fact, automatic gain adjustment also has option settings, which generally divide the control response into several levels, such as high response, medium response, and low response. Users can set it according to actual needs.