Initial shift problem and its ILC solution for nonlinear systems with higher relative degree

This paper is concerned with iterative learning control for a class of nonlinear systems with higher relative degree. As a conventional learning algorithm is applied the tracking error caused by a nonzero initial shift is detected. An initial rectifying action is introduced in the learning algorithm and is shown effective to achieve the desired trajectory jointed smoothly with a transitional trajectory from the starting position. This proposed algorithm also ensures robustness performance in the presence of resetting errors.