Classification of servo control systems and introduction to common servo control systems

A servo control system is an operating system that can automatically control the mechanical motion of a testing device according to predetermined requirements. There are many classification methods for servo systems, and there are three common classification methods:

1. Classify according to the characteristics of the controlled parameter.
2. Classification by type of driving components: Servo control systems can be divided into electromechanical servo systems, hydraulic servo systems (hydraulic control systems), and pneumatic servo systems based on the type of control components used.
3. According to control principles, servo systems can be classified into open-loop control servo systems, closed-loop control servo systems, and semi closed loop control servo systems.

1. Hydraulic servo control system
The hydraulic servo control system is based on the power provided by an electric motor, and uses a hydraulic pump to convert mechanical energy into pressure and drive hydraulic oil. By controlling various valves to change the flow direction of hydraulic oil, the hydraulic cylinder can be driven to make different strokes and directions of action to meet the different action needs of various equipment. Hydraulic servo control systems are divided into mechanical hydraulic, electro-hydraulic, pneumatic hydraulic, etc. according to the different ways of obtaining and transmitting deviation signals, among which the most commonly used are mechanical hydraulic and electro-hydraulic control systems.
According to the different controlled physical quantities, hydraulic servo control systems can be divided into position control, speed control, force control, acceleration control, pressure control, and other physical quantity control. Hydraulic control systems can also be divided into throttle control valve control and volume control pump control. In mechanical equipment, there are mainly organic hydraulic servo systems and electro-hydraulic servo systems.

2. Communication servo control system
The AC servo control system includes AC servo systems based on asynchronous motors and AC servo systems based on synchronous motors. In addition to its good stability, fast speed, and high accuracy, it also has a series of advantages. Its performance indicators can be measured from aspects such as speed range, positioning accuracy, stable speed accuracy, dynamic response, and operational stability.

3. DC servo control system
The working principle of communication servo control system is based on the law of electromagnetic force. Related to electromagnetic torque are two independent variables, main magnetic flux and armature current, which respectively control excitation current and armature current, making it easy to control torque and speed. On the other hand, from a control perspective, DC servo control is a single input single output single variable control system, and classical control theory is fully applicable to this system. Therefore, it once dominated the feed drive of CNC machine tools due to its simple control and excellent speed regulation performance.

4. Electro hydraulic servo control system
It is a feedback control system composed of an electrical signal processing device and a hydraulic power mechanism. The most common ones are electro-hydraulic position servo systems, electro-hydraulic speed control systems, and electro-hydraulic force or torque control systems.