A position control of electro-hydraulic actuator systems using the adaptive control scheme

In general, the position control of electro-hydraulic actuator(EHA) systems is difficult because of the large variation of the effective bulk modulus of the working fluid, which is due to the absence of a heat exchanger like a reservoir tank, a friction between the cylinder and piston, and an external disturbance force. Moreover, it is difficult to identify the values of the effective bulk modulus and friction. In this paper, the variations of the effective bulk modulus, friction, and external disturbance are considered as uncertainties of EHA systems. To solve the problems due to these system uncertainties, an adaptive control scheme is proposed. This new scheme uses the error equations for velocity, acceleration, and jerk, which are generated in the design procedure of the standard back-stepping control scheme. The effectiveness of the adaptive back-stepping control system was compared to that of the standard back-stepping control system through computer simulation.