Position control of an electro-hydraulic servo system based on switching between nonlinear and linear control

This paper proposes a position controller to handle three problems in the control of an electro-hydraulic servo system. The first two problems are about the nonlinearities and the uncertainties of the electro-hydraulic servo system, and the third one is the chattering problem caused by adopting sliding mode control. The proposed controller is called a Switch Controller, for its control output switches between the outputs of two controllers, a Nonlinear Controller and a conventional Linear Controller. The Nonlinear Controller is actually a nonlinear sliding mode controller and is focused to deal with nonlinearities and uncertainties. The Linear Controller is designed to improve the transient performance near the steady state. Experimental results show that the Switch Controller can improve the response performance of the electro-hydraulic servo system and effectively avoid chattering.