H∞ tracking adaptive fuzzy integral sliding mode control for parallel manipulators

In this paper, an adaptive fuzzy integral sliding mode control scheme with H_∞ tracking performance is proposed for parallel manipulators to attenuate the effects caused by nonlinear unmodeled dynamics, external disturbances, and approximation errors. First, the parallel manipulator is formulated as an error dynamics according to a specified reference model. Then, an adaptive fuzzy integral sliding mode control scheme is developed to attenuate the effects caused by unmodeled dynamics, disturbances, approximation errors, and restrain the external disturbances. The integral sliding mode control is used not only to provide one more degree of freedom to eliminate the steady-state error but to make the state error approach the equilibrium point in a finite time period quickly. Based on Lyapunov stability theorem, the proposed control scheme can guarantee the stability of the closed-loop system and achieve the H_∞ tracking performance. Finally, we will use a 2-dof parallel robot system to verify the effectiveness of the proposed control scheme.