A high gain disturbance observer design for nonlinear affine systems

This paper proposes a dynamic high gain disturbance observer design approach for a class of nonlinear affine systems. Compared with previous works, it can admit much larger class of disturbances produced by nonlinear exosystems. Under certain conditions, the observer error for the disturbances generated by nonlinear exosystems globally asymptotically converges to zero. An illustrative example of a two-link robot manipulator with limit cycles disturbance is presented to show the effectiveness of the proposed method.