Combining leakage and orifice flows in a hydraulic servovalve model

Experiments indicate that at small servovalve spool displacements, leakage flow between the valve spool and body dominates the orifice flow through th e valve. In precision positioning applications, where the servovalve operat es within the null region, this flow, if ignored, may severely degrade the performance of a conventional servohydraulic design. We have developed an i mproved servovalve model that combines both leakage and orifice flow. The m odel was developed by reviewing experimental leakage flow data and identify ing a simple mathematical form that (1) made physical sense and (2) replica ted experimental data. When combined with orifice relations, the model exte nds the accuracy and region of applicability of existing servovalve models. Further-more, the combined model is easily parameterized using available m anufacturer data.