Iterative learning control of non-linear systems with iteration-varying control direction and reference trajectory

For a class of high order nonlinear systems with structure and non structure uncertainty which are repeatable in a finite time interval, an adaptive iterative learning control algorithm is proposed. By combining the Back stepping approach, the system replacement technique with the parameter regrouping technique, which can handle the iteration-varying control direction and iteration-varying trajectory tracking problem. A differential-difference type adaptive law and an adaptive iterative learning controller are constructed to ensure the asymptotic convergence of tracking error in the sense of square error norm on the finite interval, by introducing a Lyapunov function, a sufficient condition of the convergence of the method is given. A simulation example illustrates the feasibility of the proposed method.