An electro-hydraulic servo system-also known as a tracking system-is a type of automatic control system in which the actuating element operates automatically, rapidly, and accurately in accordance with the variations of an input signal. Simultaneously, the system serves to amplify signal power. Systems composed of such electro-hydraulic components are referred to as hydraulic servo systems. Their characteristics are as follows:
(1) The servo system is a position-tracking system. The output displacement automatically follows the pattern of the input displacement, manifesting as a position-following motion.
(2) The servo system is a power amplification system. While the power required to actuate the spool valve is minimal, the system's output power can be substantial, enabling the movement of heavy loads.
(3) The servo system is a negative feedback system. The ability of the output displacement to precisely replicate the input displacement stems from the fact that the control valve body is rigidly connected to the hydraulic cylinder body, forming a negative feedback control loop. The output displacement of the hydraulic cylinder is fed back to the valve body via this loop and compared with the input displacement; this process progressively reduces and eliminates the deviation between the output and input displacements until they match. Consequently, the negative feedback mechanism is an essential component of a hydraulic servo system. Negative feedback is also a primary characteristic of automatic control systems.
