Control design for a multi input single output hydraulic cylinder system

Abstract This work discusses several approaches to the multi input, single output problem in hydraulic control. The multi input problem arises from the fact, that the actuator force in a hydraulic cylinder is the result of a combination of two pressure states, which is not uniquely defined. With each individual pressure state there may be associated a subsystem with a control input. To achieve a desired actuator force there are inifinitely many combinations of pressure values possible, and it is therefore unclear how to chose the tracking reference values for the pressure subsystems. Secondary objectives are defined, with time optimality of the step response of the subsystems being one of them, that can be used to solve the multi input problem by treating it as an optimization problem. The practical implications of the optimal solutions are discussed and a new solution is proposed, motivated by the results of the optimization problems. The proposed solution is used to develop a backstepping control for a hydraulic multi input single output system, and its performance is shown in simulation.