Servo system components

Since the servo system serves many purposes, such as computer CD drive control, radar tracking system, feed tracking system, etc., the requirements for the servo system are also different. The technical requirements for the servo system in engineering are very specific and can be summarized into the following aspects:

⒈ Requirements for the steady-state performance of the system;

⒉ Requirements for the dynamic performance of the servo system;

3. Requirements for system working environment conditions;

⒋ Requirements on system manufacturing cost, operating economy, degree of standardization, energy conditions, etc.

Although the requirements of servo systems vary due to the different moving parts, detection parts and mechanical structures of the service objects, the common point of all servo systems is to drive the controlled objects to perform mechanical movements according to the specified rules. From the perspective of automatic control theory, servo control systems generally include five parts: controller, controlled object, execution link, detection link and comparison link.

The block diagram of the servo system composition is shown in Figure 1.1.

Servo system composition (from top to bottom)

Controller: PLC, inverter, motion control card and other control devices, also called host computer;

The controller adjusts the control quantity according to the difference between the given value of the numerical control system and the actual operating value detected by the feedback device.

Servo drive: communicates between the host computer and the servo motor, and its function is similar to that of a frequency converter on an ordinary AC motor.

The power drive device is the main circuit of the system. On the one hand, it applies the electric energy in the power grid to the motor according to the size of the control quantity to adjust the size of the motor torque. On the other hand, it converts the constant voltage and frequency power supply of the power grid into the AC or DC power required by the motor according to the requirements of the motor.

Servo motor: an actuator that receives control signals from the driver;

The electric motor drives the machine to operate according to the power supply.

Mechanical equipment: convert the circular motion of the servo motor (or the linear motion of the linear motor) into the required motion form;

Various sensors and relays: detect various signals in industrial control environments and send them to the host computer or driver as the judgment standard for certain actions.

A servo system is an automatic control system that uses a certain component (such as a joystick) to make the system state reach or approach a predetermined value, and can compare the desired state (required value) with the actual state, and adjust the control component according to the difference between them (sometimes the rate of change of the difference).

Main Function

1. Use low-power command signals to control high-power loads;

2. In the absence of mechanical connection, the input shaft controls the output shaft located far away to achieve long-distance synchronous transmission;

3. Make the output mechanical displacement accurately track the electrical signal, such as recording and indicating instruments.