Signal transmission and command issuance
- The PLC (Programmable Logic Controller) sends control instructions to the servo controller through its output port. These instructions are usually in the form of digital signals, for example, pulse sequences and direction signals are used to control the movement of the servo motor. The PLC generates specific pulse signals according to the pre-written control program. The frequency of the pulse signal determines the speed of the servo motor, and the number of pulses determines the rotation angle of the motor. The direction signal is used to determine the direction of rotation of the motor, such as forward or reverse rotation.
- At the same time, other signals can be transmitted between the PLC and the servo controller, such as speed control mode selection signals, torque limit signals, etc. These signals allow the servo controller to accurately control the servo motor according to different working requirements. For example, in applications that require high-precision positioning, the PLC will send precise pulse number and frequency signals to ensure that the servo motor moves the load accurately to the specified position.
Internal processing of the servo controller
- Signal reception and decoding: The servo controller first receives the control command signals from the PLC and decodes these signals. It can identify information such as the frequency, number, and direction of the pulse signal and convert these digital signals into an electrical signal format that can be processed internally.
- Speed and position control algorithm: Based on the decoded signal, the servo controller uses an internal control algorithm to generate a current or voltage signal to drive the servo motor. For speed control, it adjusts the motor’s power supply frequency according to the received pulse frequency signal through the internal speed loop control algorithm to match the motor speed with the desired speed. In terms of position control, the servo controller uses the position loop control algorithm to accurately control the motor’s rotation angle based on the pulse number signal and the feedback information of the position feedback sensor (such as an encoder) to achieve high-precision positioning.
- Torque control (optional): Some application scenarios require the control of the servo motor’s torque. The servo controller can adjust the motor’s current according to the torque limit signal sent by the PLC or according to its own torque control algorithm, thereby controlling the motor’s output torque. For example, during machining, when the tool encounters a large resistance, the servo controller can control the motor’s output torque according to the torque feedback to prevent the motor from overloading and damage to the workpiece.
Servo motor drive and feedback regulation
- Motor drive: The servo controller outputs the processed current or voltage signal to the servo motor to drive the motor to operate. The servo motor generates the corresponding electromagnetic torque based on the received signal to drive the load to move. Since the servo motor has a high-precision magnetic field and winding design, it can quickly respond to the controller’s signal and achieve precise speed and position control.
- Feedback regulation: Servo motors are usually equipped with position and speed feedback sensors, such as encoders. The encoder converts the actual position and speed information of the motor into electrical signals and feeds them back to the servo controller. The servo controller compares the feedback signal with the received PLC control instructions and calculates the deviation value. If there is a deviation, the servo controller will adjust the current or voltage signal output to the motor in time according to the size and direction of the deviation to reduce the deviation and achieve closed-loop control. For example, when the motor speed drops due to load changes, the speed feedback signal will cause the servo controller to increase the motor’s power supply voltage to restore the motor speed to the desired value.
