Model Improvement for a Servovalve with Force Feedback and Back Pressure

Electro-hydraulic servovalve are usually an important part in mechatronic systems. The simplified governing equations for such systems already exist in literature. A comprehensive theoretical analysis of a two-stage electro hydraulic servo valve with a spool position feedback is carried out considering two main probable effects, underlap and back pressure. These analyses are based on fundamental laws of electromagnetism, fluid and general mechanics, and rectangular ports to simplify the equations. A detailed mathematical model of servovalve with circular ports (the real configuration) is developed to improve the accuracy of the model. Besides, the back pressure in the pilot region of the flapper nozzle servo valve is considered. Obtained simulation results are compared with the appropriate experimental data in literature through which the validity of the proposed model is confirmed with good accuracy. The effects of the underlap spool and the back pressure on the performance, stability and response of the whole system are investigated through solving the governing equations in Matlab simulink. Moreover, the ways to get into better responses will be suggested.