Types, principles and characteristics of hydraulic motor speed servo system

Types, principles and characteristics of hydraulic motor speed servo system

Hydraulic motor speed servo system is a commonly used servo control system in engineering. It has the characteristics of fast response, high power / mass ratio, high load rigidity and high performance price ratio. It can realize high-precision, high-speed and high-power control. Therefore, it has been widely used in aerospace, metallurgy, shipbuilding, machine tools, power equipment, coal mining machinery and other industrial fields, such as aircraft engine speed simulation system Large radar antenna, automatic gun following system, injection molding machine and oil press, etc. With the further improvement of the use requirements, such as high response and high efficiency, on the basis of the original pump controlled motor speed servo system and valve controlled motor speed servo system, there is a motor speed servo system jointly controlled by valve and pump, which is a trend of the development of hydraulic motor speed servo system.

The basic types of hydraulic motor speed servo system include pump control (volume control) and valve control (throttle control) systems. The former has high efficiency, but due to the large structural size and inertia of the swashplate variable mechanism, the dynamic response is slow, which is suitable for occasions with high power and low requirements for rapidity; Due to the servo valve or proportional valve control, the latter has fast dynamic response but low efficiency, and is suitable for medium and small power occasions with high requirements for rapidity. In order to solve the contradiction between rapidity and system efficiency, the combination of valve control (short adjustment time and small overshoot) and pump control (high system efficiency) is a trend of the development of hydraulic motor speed servo system. This valve pump simultaneous control system uses valve control output to ensure dynamic performance in the process of dynamic regulation, and mainly uses pump control output for power regulation in the steady-state regulation, so this system has high efficiency while ensuring rapidity.

The basic forms of hydraulic motor speed servo system include volume speed regulation and throttle speed regulation: ① the typical structure of volume speed regulation system is pump controlled hydraulic motor system, which controls the motor output by changing the displacement of variable pump. This control method has the advantages of low power loss and high efficiency. Therefore, it has been applied in many occasions, especially in high-power systems, but it has the defects of low-speed instability and poor dynamic characteristics; ② The throttle speed regulation system regulates the flow into the hydraulic motor by adjusting the opening of the servo valve, so as to control the speed of the motor. It is characterized by fast response and low efficiency, and is suitable for occasions with high requirements for dynamic characteristics. The emergence of valve pump combined regulation system partially solves the contradiction between rapidity and system efficiency. It has the characteristics of fast response and high efficiency, and can be applied to occasions with high power, high precision and fast response. To sum up, the main structural forms, characteristics and applications of the hydraulic motor speed servo system are summarized in the following table as a reference for application.

Structure and performance comparison table of hydraulic motor speed servo system