Sliding-mode control of a servomotor-pump in a position control application

This paper presents the design of a position controller in a power cylinder control application using a servomotor-pump assembly. Electro-hydraulic systems are known for their highly non-linear behavior and their sensitivity to parameter variation. The controller presented here uses the robustness property of sliding-mode controllers to resolve efficiency variations of the pump which are dependant of the pressure operating point and its speed of rotation. Complete electrohydraulic simulation models including the servomotor and hydraulic valves are used to demonstrate the effectiveness of the controller compared to a standard PI position controller. The results show that the presented sliding-mode controller is up to 24 times more robust to parameter variation than a standard PI position controller.