On three discrete-time adaptive ILCs for different nonlinear uncertain systems

In this paper, three discrete-time adaptive ILC approaches are discussed fully. In parallel with the continuous-time systems, a discrete-time adaptive ILC with time-difference estimator is first proposed for a class of discrete-time systems with constant parametric uncertainties. And then, a discrete-time adaptive ILC with hybrid-difference estimator is proposed for the other class of discrete-time systems with a mixture of time-varying and time-invariant uncertain parameters. The existing discrete-time adaptive ILC with iteration-difference is also reviewed for the convenience of comparison. Three cases are considered in the simulation to show the effectiveness of the proposed adaptive ILCs and to answer the question that which one is most suitable for the different controlled systems.