A Nonlinear Model Predictive Control Scheme with Multirate Integral Sliding Mode *

In this paper, a hierarchical multirate control scheme for nonlinear discrete-time systems is proposed, composed of a robust model predictive controller (MPC) and a multirate integral sliding mode (MISM) controller. In particular, the MISM controller acts at a faster sampling time than the MPC controller, and reduces the effect of model uncertainties and external disturbances, in order to obtain, at the next sampling instant of the MPC controller, a value of the system state that is as close as possible to the nominal one. To obtain this result, the control variable is composed of two parts: one generated by the MPC controller, and the other by the MISM controller. The a-priori reduction of the disturbance terms turns out to be very useful in order to improve the convergence properties of the MPC controller.