Servo drives protect servo motors and allow for better operation. Below, we'll examine the control circuit structure and some relevant parameters of servo drives.
Servo driver control circuit structure
The DSP is the core of the entire system, mainly responsible for tasks with high real-time requirements, such as vector control, current loop, speed loop, position loop control, PWM signal generation, and various fault protection handling.
MCUs perform management tasks with relatively low real-time requirements, such as parameter setting, key handling, status display, and serial communication.
FPGA enables data exchange between DSP and MCU, external I/O signal processing, internal I/O signal processing, position pulse command processing, and second encoder counting.
The power circuit adopts a modular design, with the three-phase full-bridge rectifier and the AC-DC-AC voltage source inverter connected via a common DC bus. The three-phase full-bridge rectifier is implemented using power modules, and a soft-start circuit and an energy dissipation circuit are included to avoid excessive instantaneous current during power-on and high pump-up voltage during motor braking. The inverter is implemented using intelligent power modules.
Servo driver parameters
Position Scale Gain
① Set the proportional gain of the position loop regulator.
② 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 conditions. However, too large a value may cause oscillation or overshoot.
③ The parameter values are determined by the specific servo system model and load conditions.
Position feedforward gain
① Set the feedforward gain of the position loop.
② A larger set value indicates a smaller position lag under any command pulse frequency.
③ A large feedforward gain in the position loop improves the high-speed response characteristics of the control system, but it can also make the system's position unstable and prone to oscillation.
④ When a high response characteristic is not required, this parameter is usually set to 0, indicating a range of 0~100%.
Speed proportional gain
① Set the proportional gain of the speed regulator.
② The larger the setting value, the higher the gain and the greater the stiffness. 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 setting value.
③ Set the value as large as possible without causing system oscillation.
Velocity integral time constant
① Set the integral time constant of the speed regulator.
④ The smaller the setting value, the faster the integration 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 setting value.
② Set the value as small as possible, provided that the system does not oscillate.
Speed feedback filter factor
① Set the characteristics of the speed feedback low-pass filter.
② The higher the value, the lower the cutoff frequency, and the less noise the motor produces. If the load inertia is very large, the set value can be appropriately reduced. A value that is too large will slow down the response and may cause oscillation.
③ The smaller the value, the higher the cutoff frequency, and the faster the speed feedback response. If a higher speed response is required, the set value can be appropriately reduced.
Maximum output torque setting
① Set the internal torque limit value of the servo motor.
② The setting value is a percentage of the rated torque.
③ This limitation effectively defines the scope of completion at all times.
① Set the positioning completion pulse range under the position control mode.
② This parameter provides the basis for the driver to determine whether positioning is complete under position control mode. When the remaining number of pulses in the position deviation counter is less than or equal to the value set in this parameter, the driver considers positioning to be complete and the position switch signal is ON; otherwise, it is OFF.
③ In position control mode, output a position positioning completion signal and acceleration/deceleration time constant.
① The setting value represents the acceleration time of the motor from 0 to 2000 r/min or the deceleration time from 2000 to 0 r/min.
②The acceleration/deceleration characteristics are linear, and the speed range is [not specified].
① Set arrival speed
② In non-position control mode, if the motor speed exceeds the set value, the speed reach switch signal is ON; otherwise, it is OFF.
③ This parameter is not needed in position control mode.
④ It is independent of the direction of rotation.
This concludes the introduction to servo drives. We believe that after reading this article, you will have a deeper understanding of servo drives.
