Model-free adaptive command-filtered-backstepping sliding mode control for discrete-time high-order nonlinear systems

A new model-free adaptive sliding mode control method is proposed to solve some control issues in a class of discrete-time high-order nonlinear systems whose dynamics are unknown in this paper. In order to simplify the nonlinear system, a new concept called pseudo-partial derivative matrix (PPDM) is introduced to facilitate the nonlinear system by using a compact form dynamic linearization approach. Therefore, to estimate the PPDM, the identified adaptive observer is constructed using the input/output data from each subsystem of the higher order discrete time system. Taking into account the amplitude and rate constraints of real-world input signals, an anti-windup dynamic compensator is developed. Furthermore, the problems of complexity explosion and non-causality are solved by using discrete-time command filters while designing the controller. It has been shown that all the control variables in closed-loop systems are uniformly-ultimately bounded. An example of a linear induction motor taking into account the end effects is used to verify the effectiveness of the presented control strategy through simulations and experiments. (C) 2019 Elsevier Inc. All rights reserved.