Non-linear adaptive controller with a variable adaptation rate for a simulated model of an electrohydraulic actuator

Abstract

An adaptive control method is presented for a single-rod electrohydraulic system with a heavy load force acting on the cylinder piston. Previous adaptive control approaches always used adaptation law to estimate the system parametric uncertainties. However, in a practical hydraulic thrust system with a heavy resistant load force, the system parametric uncertainties can be neglected with respect to the greater load force. The objective of the paper is to present a non-linear adaptive controller with adaptation laws to track the changeable load force automatically. The main feature of the scheme is that an exponential-form function has been introduced to construct an invariable convergence rate of the adaptive controller, by which the conflicting system performances could be satisfied harmonically. The simulation results for an electrohydraulic actuator show that the non-linear control algorithm, together with the variable adaptation scheme, achieves a good synthetic performance in keeping the cylinder thrusting in a smooth and optimal energy-saving operating state.