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- Title
Neural network‐based output‐feedback adaptive control for a class of uncertain strict feedback fractional‐order nonlinear systems subject to input saturation.
- Authors
Rabahi, Zoubir; Daoudi, Islem; Chemachema, Mohamed
- Abstract
Summary: This paper presents neural networks (NNs) adaptive controller for an uncertain fractional‐order nonlinear system in strict‐feedback form, subject to input saturation, unavailable states for measurement, and external disturbances. The fractional‐order adaptive laws are derived based only on the output tracking error thanks to the implementation of the strictly positive real (SPR) property, differently from the existing results in the literature of fractional‐order strict‐feedback systems where all system states are used in the adaptive laws. The proposed design approach addresses the nonaffine nature of the control input due to saturation nonlinearity by using the mean value theorem and follows a nonrecursive design by using a state transformation where the advantage is twofold. First, it eliminates the explosion complexity found in back‐stepping control‐based approaches design, and second, it reduces the approximators units and parameters in controller implementation. Furthermore, an observer is introduced to estimate the unavailable newly defined states, and then an output adaptive feedback control design is ensured. An NN is used to approximate the unknown ideal control law, and an auxiliary control term is appended to deal with saturation effect, unknown disturbance, and approximation errors. The tracking error is proved to converge asymptotically to a bounded set using the Lyapunov theory. Simulation results on three examples show the effectiveness of the proposed approach.
- Subjects
ADAPTIVE control systems; NONLINEAR systems; MEAN value theorems; BACKSTEPPING control method; APPROXIMATION error; PSYCHOLOGICAL feedback
- Publication
International Journal of Adaptive Control & Signal Processing, 2024, Vol 38, Issue 5, p1690
- ISSN
0890-6327
- Publication type
Article
- DOI
10.1002/acs.3773