1. Classified according to the characteristics of the controlled variable parameter.
2. Classification by type of driving element: Servo control systems can be classified into electromechanical servo systems, hydraulic servo systems (hydraulic control systems) and pneumatic servo systems according to the type of control element used.
3. Classification by control principle: Servo systems can be divided into open-loop control servo systems, closed-loop control servo systems, and semi-closed-loop control servo systems.
The four common servo control systems are as follows:
1. Hydraulic servo control system
A hydraulic servo control system uses an electric motor as its power source and a hydraulic pump to convert mechanical energy into pressure, which then drives hydraulic oil. By controlling various valves to change the flow direction of the hydraulic oil, it drives the hydraulic cylinder to perform movements of different strokes and directions, fulfilling the different action requirements of various equipment. Hydraulic servo control systems are classified into mechanical-hydraulic, electro-hydraulic, and pneumatic-hydraulic systems according to the different methods of obtaining and transmitting deviation signals. Among these, mechanical-hydraulic and electro-hydraulic control systems are more commonly used.
Based on 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 throttling control (valve-controlled) and volumetric control (pump-controlled). In mechanical equipment, the main types are organic-hydraulic servo systems and electro-hydraulic servo systems.
2. AC servo control system
AC servo control systems include AC servo systems based on asynchronous motors and AC servo systems based on synchronous motors. Besides being characterized by good stability, high speed, and high precision, they possess a range of advantages. Their performance can be measured by factors such as speed range, positioning accuracy, speed stability, dynamic response, and operational stability.
3. DC Servo Control System
The working principle of an AC servo control system is based on the law of electromagnetic force. Related to electromagnetic torque are two independent variables: the main magnetic flux and the armature current. These control the excitation current and armature current respectively, facilitating torque and speed control. On the other hand, from a control perspective, a DC servo control system is a single-input, single-output, single-variable control system. Classical control theory is fully applicable to this type of system. Therefore, due to its simple control and excellent speed regulation performance, it once dominated the feed drive of CNC machine tools.
4. Electro-hydraulic servo control system
It is a feedback control system consisting of an electrical signal processing device and a hydraulic power mechanism. The most common types include electro-hydraulic position servo systems, electro-hydraulic speed control systems, and electro-hydraulic force (or torque) control systems.
These are four commonly used servo systems. Their working principles, performance, and application ranges differ, each with its own characteristics, advantages, and disadvantages. Therefore, when selecting or purchasing, it is necessary to calculate and choose the appropriate product based on the system's requirements, the parameters to be controlled, and the performance to be achieved.
