Variable structure control with applications to T-S fuzzy systems
Khoo, Sui Yang
Date of Issue2008
School of Computer Engineering
In this thesis, the problem of robust variable structure control for a class of complex uncertain nonlinear systems is investigated. A number of robustness and convergence results are presented for variable structure control systems with bounded unknown mismatched uncertainties. The finite time stabilization problems of uncertain nonlinear system and T-S fuzzy system are addressed. The major outcomes of the work described in this thesis are summarized as follows: First, a simplified multiple-surface sliding control (MSSC) algorithm is proposed based on a recursive design approach that can significantly reduce the time complexity from D(2 n) to D(n), where n is the number of iterations. This methodology is then extended to the problem of adaptive fuzzy multiple-surface sliding mode control (AFMSMC) of a class of nonlinear systems with mismatched uncertainties. In this scheme, the Mamdani fuzzy logic-based approximator is first employed to learn the system uncertainties in Lyapunov sense, i.e., the weights are adaptively adjusted so that the output tracking error can asymptotically converge to zero according to the second method of Lyapunov stability. The iterative MSSC design is then carried out to ensure closed-loop stability. Strong robustness property and asymptotic error convergence are guaranteed.
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