Robust force control in a novel electro-hydraulic structure using polytopic uncertainty representation

Electro-hydraulic servo systems (EHSS) are used in many industrial applications for position and force control. Force control with a hydraulic actuator is challenging and requires complicated control algorithms used along with high crossover frequency electro-hydraulic valves, even for simple force control tasks. In this paper, a different hydraulic structure is proposed to improve the force tracking quality and increase efficiency in the EHSS. This comes at the cost of a new model with linearization and uncertainty challenges. To address these challenges, a robust H. control design approach is followed to control the proposed EHSS. Model linearization uncertainties are approximated by a polytope and a robust controller is designed to keep the system stable and satisfy the H. performance conditions within this polytope. Experimental results verify that the objectives of the paper are satisfied after using the proposed system. (C) 2014 ISA. Published by Elsevier Ltd. All rights reserved.