Force and position control in the electro-hydraulic system by using a MIMO fuzzy controller

An electro-hydraulic system (EHS) usually has the force and position controls. For control of these parameters to the desired value, multiple PID controllers are often used, which are sensitive to change in system parameters. Therefore, in this paper, a multi-input multi-output (MIMO) fuzzy controller is proposed to control those variables. The proposed controller has four inputs and three outputs. The input variable consists of a position error, velocity error, force error, and change of force error. The part of output variable consists of a signal to drive proportional direction control valve to control the position of an actuator, a signal is used to command the inverter to control the speed of the electric motor to drive the fixed displacement gear pump which determines flow and pressure (force), and finally, a signal to drive proportional pressure relief valve to reduce any losses. Consequentially, the EHS that is used for this control is designed to saving energy. The proposed controller and the EHS are implemented to the hydraulic press. The experimental results showed that the hybrid of force and position control by using a MIMO fuzzy controller has a superior performance compared to the multiple PID controllers. The proposed EHS also saves more energy than conventional EHS. Thus, the MIMO fuzzy controller can be an alternative to control multi-variables in the EHS.