The Effects of Orifice Sizes on a Hydraulic Servo Valve Control System

Precision control for a force controlled hydraulic system can be achieved through the use of a flow controlled servo valve. Servo valves can be manufactured with a spool that is overlapped, an under lapped, or has a zero lap. A servo valve with a zero lap is desirable for a responsive hydraulic system without leakage, but has the disadvantage of creating a pressure pulse upon opening the valve. The hydraulic system for this setup involves having a double end, double action actuator that will have a cyclic motion generating multiple pressure waves in the system. Including an orifice in the system, which will function as a dampener, can reduce the pressure pulses. Traditional locations for orifices have been in the spool and on the actuator piston. For this hydraulic system design an external orifice will be introduced into the system via the use of an orifice plate included in the hydraulic fittings. This change allows for the ability to change the orifice size. Changing the orifice size to determine the effects on the systems control will be analyzed. The intended outcome is to demonstrate that different sized orifice plates will cause changes to the control system behavior so that an experimental formula will be established for this approach of a zero lap valve with an external damper for reduction of overshooting of dynamical behavior of the valve spool.