Adaptive Fuzzy Control of Nonlinear Systems With Unmodeled Dynamics and Input Saturation Using Small-Gain Approach

• Published in: IEEE transactions on systems, man, and cybernetics. Systems Vol. 47; no. 8; pp. 1979 - 1989
• Main Authors: Zhou, Qi, Li, Hongyi, Wu, Chengwei, Wang, Lijie, Ahn, Choon Ki
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive control; backstepping; Control systems; Design engineering; Dynamical systems; Feedback control; Fuzzy control; Fuzzy logic; fuzzy logic systems; Fuzzy systems; MIMO; Nonlinear dynamical systems; Nonlinear dynamics; Nonlinear systems; nonstrict-feedback system; Saturation; Separation; small gain approach
• ISSN: 2168-2216; 2168-2232
• DOI: 10.1109/TSMC.2016.2586108

This paper investigates the problem of adaptive fuzzy state-feedback control for a category of single-input and single-output nonlinear systems in nonstrict-feedback form. Unmodeled dynamics and input constraint are considered in the system. Fuzzy logic systems are employed to identify unknown nonlinear characteristics existing in systems. An appropriate Lyapunov function is chosen to ensure unmodeled dynamics to be input-to-state practically stable. A smooth function is introduced to tackle input saturation. In order to overcome the difficulty of controller design for nonstrict-feedback system in backstepping design process, a variables separation method is introduced. Moreover, based on small-gain technique, an adaptive fuzzy controller is designed to guarantee all the signals of the resulting closed-loop system to be bounded. Finally, two illustrative examples are given to validate the effectiveness of the new design techniques.