Proportional control of on/off solenoid operated hydraulic valve by nonlinear robust controller

Absrracf - The growth of electonics control systems, automation and robotics for agricultural and construaion machinery demands less expensive, robust electrohydraulic devices to interface fluid power systems. Servo and proportional valves need two or three stages of amplification and delicate mechanisms or sensors in the loops, to control high oil flow by small electomecbanical motors linearly. Tradictional onloif solenoids are cheaper, robust, have higher power-mass ratio and could have small and large sues, but they are not usally used for this aim by high nonlinearit?.. The present work investigates about continuos and proponional control of on/oN solenoid driving valve spool directly, by modern nonlinear control like VSC and using solenoid model to estimate spool position. Magnetic model of solenoid and hydralic floa forces of valve are carried out without to use FEM tecbiques. The inevitable inaccuracies of these models and the impossibilit?. IO consider and value frictions forces suggested to use VSC b? its robustness, the architecture of control system is based on a external VSC position loop and an internal current loop with tradictional PI controller to reduce problems due to the chattering further. We investigated to estimate position too, in particular when the valve is power by a solenoid only, to avid use of additional sensor, for this aim the derivative of current is used in simple way. Control and di/dt measurement systems are designed to fit practical and not expensive approach.