Servo hydraulic system is a closed-loop control system composed of hydraulic power mechanism and feedback mechanism, which is divided into mechanical hydraulic servo system and electrical hydraulic servo system (referred to as electro-hydraulic servo system). Among them, the mechanical hydraulic servo system was applied earlier, mainly used in aircraft rudder surface control and machine tool copying device. With the emergence of electro-hydraulic servo valve, electro-hydraulic servo system occupies an important position in the field of automation. Many high-power fast response position control and force control are applied to the electro-hydraulic servo system, such as aircraft, missile steering gear control system, ship steering gear system, radar, cannon servo system, rolling machinery hydraulic pressure system, manipulator control and various scientific test devices (flight simulation turntable, vibration test bench).
The servo hydraulic system has three advantages compared with the electrical servo system: (1) small size, light weight, small inertia, good reliability, and large output power; ② Good speed; (3) The stiffness is large (that is, the output displacement is less affected by the external load) and the positioning is accurate. The disadvantage is that the processing is difficult, the anti-pollution ability is poor, the maintenance is not easy, the cost is high.
