Disturbance observer based adaptive fuzzy sliding mode control: A dynamic sliding surface approach

In this paper, the disturbance observer based adaptive sliding mode control (SMC) approaches are established for Takagi-Sugeno fuzzy systems with unknown external disturbance. In order to counteract the disturbance actively, a novel memory-based fuzzy disturbance observer is proposed to estimate the unknown disturbance. In the absence of upper bound information of the disturbance estimation errors, by designing novel dynamic sliding surfaces and adaptive laws, both the state- and output-based adaptive fuzzy sliding mode controllers are designed without any constraints on input matrices, and the disturbance estimate is incorporated to achieve active disturbance rejection. It can be shown that, with the proposed control approaches, both the sliding variables and the adaptive parameter estimation errors will converge to the bounded region in fixed-time. Finally, numerical examples are presented to show the effectiveness of the proposed control approaches. (C) 2021 Elsevier Ltd. All rights reserved.