Servo motors are frequently used in automated equipment, especially for position control. Most brands of servo motors have position control functions, which are controlled by pulses emitted by the controller. The number of pulses corresponds to the rotation angle, and the pulse frequency corresponds to the speed (related to the electronic gear settings). When a new system fails to function properly, first set the position gain, ensuring the motor operates without noise, and set it as high as possible. The moment of inertia ratio is also very important and can be referenced using the values set through self-learning.
Then set the speed gain and speed integration time to ensure continuous operation at low speeds and controllable position accuracy.
(1) Position proportional gain
Set the proportional gain of the position loop regulator. A higher value results in higher gain, greater stiffness, and less position hysteresis under the same frequency command pulse conditions. However, excessively high values may cause oscillation or overshoot. The parameter value is determined by the specific servo system model and load conditions.
(2) Position feedforward gain
This parameter sets the feedforward gain of the position loop. A higher value indicates a smaller position hysteresis at any command pulse frequency. A larger feedforward gain improves the high-speed response of the control system, but it can also make the system's position unstable and prone to oscillations. When a high response characteristic is not required, this parameter is usually set to 0. Range: 0~100%
(3) Velocity proportional gain
Set the proportional gain of the speed regulator. A higher value results in higher gain and greater stiffness. The parameter value is determined based on the specific servo drive system model and load conditions. Generally, the higher the load inertia, the higher the set value. Set the largest possible value while ensuring the system does not oscillate.
(4) Velocity integral time constant
Set the integral time constant of the speed regulator. The smaller the value, the faster the integral speed. The parameter value is determined based on the specific servo drive system model and load conditions. Generally, the larger the load inertia, the larger the set value. Set the smallest possible value while ensuring the system does not oscillate.
(5) Velocity feedback filter factor
Configure the characteristics of the speed feedback low-pass filter. A higher value results in a lower cutoff frequency and less noise from the motor. If the load inertia is large, the setting can be reduced appropriately. A value that is too large will slow down the response and may cause oscillation. A lower value results in a higher cutoff frequency and a faster speed feedback response. If a higher speed response is required, the setting can be reduced appropriately.
(6) Maximum output torque setting
Sets the internal torque limit value of the servo drive . The setting value is a percentage of the rated torque, and this limit is effective at all times. The positioning completion range is set to the positioning completion pulse range in position control mode. This parameter provides the basis for the drive to determine whether positioning is complete in position control mode. When the remaining number of pulses in the position deviation counter is less than or equal to the setting value of this parameter, the drive considers positioning complete, and the position switch signal is ON; otherwise, it is OFF.
In position control mode, the output position positioning completion signal is displayed. The acceleration/deceleration time constant setting represents the acceleration time of the motor from 0 to 2000 r/min or the deceleration time from 2000 to 0 r/min. The acceleration/deceleration characteristic is linear. The speed range setting determines the speed reach. In non-position control mode, if the servo motor speed exceeds this setting, the speed reach switch signal is ON; otherwise, it is OFF. This parameter is not used in position control mode. It is independent of the rotation direction.
(7) Manually adjust the gain parameters
Adjust the speed proportional gain (KVP) value. After the servo system is installed, parameters must be adjusted to ensure stable rotation. First, adjust the speed proportional gain (KVP) value. Before adjustment, the integral gain (KVI) and derivative gain (KVD) must be adjusted to zero. Then, gradually increase the KVP value; simultaneously observe whether oscillation occurs when the servo motor stops, and manually adjust the KVP parameter to observe whether the rotational speed fluctuates significantly. If the KVP value increases to the point where the above phenomenon occurs, the KVP value must be reduced back to eliminate oscillation and stabilize the rotational speed. This KVP value is the initially determined parameter value. If necessary, after adjusting KVI and KVD, repeated corrections can be made to achieve the ideal value.
Adjust the integral gain KVI value. Gradually increase the integral gain KVI value to allow the integral effect to gradually emerge. As can be seen from the previous introduction to integral control, the KVP value, when increased to a critical value in conjunction with the integral effect, will produce oscillations and instability. Similar to the KVP value, reduce the KVI value to eliminate the oscillations and stabilize the rotational speed. The KVI value at this point is the initially determined parameter value.
Adjust the differential gain (KVD) value. The main purpose of the differential gain is to smooth the rotation of the speed and reduce overshoot. Therefore, gradually increasing the KVD value can improve speed stability.
Adjust the position proportional gain (KPP) value. If the KPP value is set too high, the servo motor will experience excessive overshoot during positioning, causing instability. In this case, the KPP value must be reduced to decrease the overshoot and avoid the unstable region; however, it cannot be set too low, as this will reduce positioning efficiency. Therefore, careful adjustment is necessary.
(8) Automatically adjust gain parameters
Modern servo drives are all microcomputer-based, and most offer automatic gain adjustment (autotuning) to handle most load conditions. When adjusting parameters, you can first use the automatic parameter adjustment function, and then adjust manually if necessary.
In fact, automatic gain control also has settings options, and the control response is generally divided into several levels, such as high response, medium response, and low response, which users can set according to their actual needs.
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