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Practical profile tracking for a hydraulic press using sliding mode controller

Electro Hydraulic Servo Systems (EHSS) offer fast response in different industrial aspects such as heavy machines, cranes and robots. To obtain a precise piston profile and to achieve the designed speed, a Sliding Mode Controller (SMC) for the duration of piston extension and retraction is presented in this paper. The novelty lies in the development of a practical profile connecting the system supply pressure dynamics to the duration of piston extension and retraction. Based on the curve fitting technique, a quadratic profile is designed for a practical hydraulic press. The Sliding Mode Controller is employed to achieve repeatable tracking of the profile generated with guaranteed soft seating velocity, thereby increasing the lifetime of the hydraulic press. The performance of the proposed controller is compared with the baseline Proportional Integral Derivative (PID) controller with square wave as well as exponential wave tracking tests in simulation and experimentation which confirm the effectiveness of the proposed control scheme.