Control design for harmonic disturbance rejection for robot manipulators with bounded inputs

In this paper, we consider the tracking control problem under input constraints for robot manipulators which are affected by unmeasurable harmonic disturbances. A new control scheme is proposed for the problem, which composed of a parameter-dependent nonlinear observer and a tracking controller. The parameter-dependent nonlinear observer designed by the internal model principle, can achieve a estimation and compensating of a class of harmonic disturbance with unknown frequency. The tracking controller, which is designed via adaptive technique, can asymptotically track desired trajectory. In control design using continuous piecewise differentiable increasing function to limit control input, such that control input saturation is avoided. The Lyapunov stability of closed loop system is analyzed. The simulation results show the effectiveness of the proposed controller.