Investigation of an Electrohydraulic Servovalve With Tuneable Return Pressure and Drain Orifice

Abstract

This paper describes a new concept of electrohydraulic servovalve where the novelty lies mainly in the fact that the return pressure and return orifice of the servovalve are tuneable and can be adjusted to satisfy the system control requirements. The actuator velocity characteristics of a hydraulic servomechanism operating under steady state condition is analysed through the use of dimensionless quantities. It is established that the proposed configuration exhibits a nonlinear actuator velocity versus servovalve opening relationship and at small servovalve opening, the system offers a higher actuator velocity. The closed loop system transient responses are also investigated by means of digital computer simulation. The results are experimentally verified on a test rig specifically designed for this purpose. It is observed that with the return pressure and return orifice properly tuned, one can achieve a high gain yet high damping servosystem. A design procedure is described which provides the designer with a step by step method for determining the tuning parameters in order to obtain a desired system performance.

Influence of drain orifice on poppet valve stability

“…where F is the flow force acting on the poppet, which is given by (4) where the valve seat is not chamfered.…”