Continuous Sliding Mode Iterative Learning Control for Output Constrained MIMO Nonlinear Systems

Abstract This paper investigates the time-varying output constraints tracking problem for a class of MIMO nonlinear system, where a new design of Iterative Learning Control (ILC) with adaptive sliding mode method is implemented. Firstly, to solve the unknown periodic parameters problem of MIMO nonlinear system, an ILC strategy is applied to estimate the parameters values which are difficult to be obtained accurately. Secondly, in view of unknown bounded disturbances, a continuous second-order sliding mode adaptive algorithm is utilized, where the disturbances can be estimated by the adaptive law without the upper bound knowledge. Meanwhile, the second-order sliding mode integral term is employed to suppress chattering phenomena. Then, considering the prescribed tracking performance, a novel universal Barrier Lyapunov Function (BLF) is proposed to address the constraint requirements which can change along with the time domain and the iteration domain. The stability and iterative convergence of the adaptive iterative learning sliding mode controller with time-varying constraints are proved by composite energy function (CEF). Finally, the effectiveness of the proposed algorithm is verified by simulation results.