New synthetic fluid dynamic model for aerospace four-ways servovalve

Design and development of modern flight control systems require highly detailed computer models of the on-board equipment in order to emulate its behaviour; conversely, simplified models are needed in preliminary design optimization and diagnostic or prognostic strategies. In these cases constrains on computational time require to implement simplified models able to combine sufficient levels of accuracy and reliability with reduced computational costs. In this context, this work proposes a new simplified numerical model of the servovalve fluid-dynamic behaviours; this algorithm, characterized by a semi-empirical formulation, account for the effects of spool geometry, variable supply pressure and water hammer. In order to evaluate the approximations introduced by this model into a system-level simulation, it has been integrated in a proper numerical model emulating the behaviour of a typical electrohydraulic on-board actuator. It is compared with a higher fidelity servovalve model and its accuracy is evaluated both regarding the static pressure-flow characteristic and servomechanism dynamic response.