Adaptive super-twisting sliding mode control on hydraulic actuator of a 6-DOF parallel manipulator

In this paper, the robust control strategy, super-twisting algorithm, is applied on the hydraulic actuator of the 6 degree-of-freedom (DOF) parallel manipulator, so-called Stewart platform. The second order sliding mode algorithm is often used to design controllers for the properties of robustness and chattering-free. In the control issues of hydraulic actuators, the perturbations such as friction and parameter variation are usually considered. The proposed controller guarantees finite time convergence with the constant bounded perturbation and the friction which is described by the dynamics friction model. In addition, the perturbation caused of model parametric error was also tackled via designing an adaptive law. The Lyapunov stability analysis ensures the robustness and convergence of the hydraulic system. The control performance of the proposed approach is demonstrated in the simulation results.