Nonlinear Robust Adaptive Control of Hydraulic Manipulators with Asymptotic Tracking Performance

Parametric uncertainties associated with un-modeled disturbances always exist in hydraulic manipulator systems, which will degrade their motion tracking accuracy. In this paper, a nonlinear robust adaptive control strategy is proposed for achieving the high precise tracking control of hydraulic manipulator system. The dynamics equations are first derived. Then, a parameter adaptive law and a nonlinear robust control law are designed to eliminate the effect of errors between the theoretical and the practical model and suppress unmodeled disturbances, respectively. Furthermore, the designed controller guarantees an asymptotic tracking performance even in the presence of various uncertainties via Lyapunov analysis. Finally, the proposed controller is tested through multi-platform co-simulation. Comparative results are provided to illustrate that the designed controller is able to reduce the max tracking errors of the three joints by 12%, 61% and 53% with higher performance nature compared to model-based control(MBC).