Fluid structure interaction in electrohydraulic servovalve: a finite element approach

Abstract

Electrohydraulic servovalves (EHSV) promise unique application opportunities and high performance, unmatched by other drive technologies. Typical applications include aerospace, robotic manipulators, motion simulators, injection molding, CNC machines and material testing machines. EHSV available are either a flapper/nozzle type or a jet pipe type. In the present paper an attempt has been made to study the dynamics of jet pipe EHSV with built-in mechanical feedback using Finite Element Method (FEM). In jet pipe EHSV, the dynamics of spool greatly depends on pressure recovery and hence the fluid flow at spool ends. The effect of pressure recovery on spool dynamics is studied using FEM by creating the fluid-structure-interaction. The mechanical parts were created using general purpose finite elements like shell, beam, and solid elements while fluid cavities were created using hydrostatic fluid elements. The analysis was carried out using the commercially available FE code ABAQUS. The jet pipe and spool dynamics are presented in the paper.Keywords: Fluid-structure-interaction, drain line orifice, mechatronic component, finite element method, feedback. INTRODUCTIONFluid power control is the transmission and control of energy by means of a pressurized fluid, is an old and well recognized discipline. The growth of fluid power has accelerated with our desires to control ever increasing quantities of power and mass with higher speeds and greater precision. More specifically, where precise motion control is desired and space and weight are limited, the convenience of high power-to-weight ratio makes hydraulic servomechanisms the ideal control elements. The demand to achieve more accurate and faster control at high power levels, especially in the areas of machine tools, primary flight controls, and automatic fire control produced an ideal marriage of hydraulic servomechanisms with electronic signal processing. Information could be transduced, generated, and processed more easily in the electronic medium than as pure mechanical or fluid signals, while the delivery of power at high speeds could be accomplished best by the hydraulic servo. This marriage of electronics and hydraulics into electrohydraulic servomechanisms created both a solution to an existing class of control problems and a demand for a whole new strain of components. The evolution of these components is really a story of increasingly demanding applications each of which caused the creation of better, or more efficient, or more reliable, or faster devices. To satisfy this demand, new manufacturing methods had to be conceived and original testing techniques developed.Electrohydraulic Servovalve (EHSV) are faster responding directional, pressure and flow control valves which are frequently used in a closed loop arrangements to produce the highly sophisticated performance, in terms of high

A Review of Electro-Hydraulic Servovalve Research and Development

“…Several studies have been proposed to model servovalves, using analytical, CFD (Computational Fluid Dynamics) and/or FEM (Finite Element Method) approaches (Lin and Akers, 1989, Hiremath, 2013, Urata et al, 2008, Ghasemi et al, 2008, Di Rito and Galatolo, 2008, El-Araby et al, 2011, Gordić et al, 2004, Maré and Attar, 2008, Hiremath and Singaperumal, 2010. In this section, analytical models are considered.…”