Iterative Learning Control With Time-Delay Compensation: An Application to Twin-Roll Strip Casting

In this article, we propose an iterative learning control (ILC) algorithm for a class of periodic processes with a variable time-delay that is greater than one iteration of the process. We propose a definition of the time delay as the sum of an integer and a residual such that the two components can be estimated separately. This structure enables the derivation of a stability law for an ILC algorithm that is a function of the delay-estimation error. Additional remarks are given regarding the steady-state performance of the combined time-delay-estimation and ILC algorithm. The proposed algorithm is then applied to a twin-roll strip casting process. We demonstrate the sensitivity of the ILC algorithm to the time-delay-estimation error through simulation results and define an upper bound for the time-delay-estimation error that can be tolerated before the ILC algorithm begins to amplify the disturbance. We then validate the combined time-delay-estimation and ILC algorithm's performance using experimental process data from an industrial twin-roll strip casting process.