Electrohydraulic Servo System

 Fig.8.26 illustrates a circuit that uses a closed-loop electrohydraulic servo control system.

ELECTROHYDRAULIC SERVO SYSTEM

1. Construction

Fig.8.26 illustrates a circuit that uses a closed-loop electrohydraulic servo control system. This circuit is very much similar to the open loop hydraulic circuit except that a servo valve replaces the flow control and directional valves.

2. Operation

In this servo system, a feedback device which is attached to the hydraulic actuator senses the actuator position or speed and transmits a corresponding electrical signal to the servo valve. This feedback signal is compared with electrical input signal. Suppose the actuator position or speed is not that intended, then the electronic summer will generate an error signal. This error signal is amplified and fed to the torque motor to correct the difference.

Therefore electrohydraulic servo valves can provide very accurate control relative to position, speed, pressure and load by incorporating the appropriate feedback devices.