Asymptotic output tracking control of electro-hydraulic systems with unmatched disturbances

In this study, an introduced auxiliary error signal-based robust control method and an adaptive control strategy are synthesised through backstepping method for high precise motion tracking control of double-rod hydraulic servo systems. The controller takes the non-linear behaviour in flow, unmatched disturbances in inertia load dynamics, and matched uncertainties in pressure dynamics into consideration. In addition, the developed controller does not require a priori knowledge on the bounds of the lumped disturbances and the gain of the devised robust control law can be tuned itself. As a result, the obtained control strategy can achieve an exact tracking performance for the whole closed-loop hydraulic system in the presence of matched and unmatched uncertainties simultaneously. Extensive experiments are carried out for the trajectory tracking control of a double-rod hydraulic servo system and the results reveal the high-performance of the presented controller.