在未知系統參數的變動或系統內部不穩定性及外部干擾下，很可能造成非線性系統的工作性能下降，以致追蹤不易被達成，甚至造成系統不穩定，因此以本文提出的模糊滑動 控制器來解決此問題。基於李亞布諾夫穩定性準則下，本控制器可以使具有內部不穩定性的非線性系統穩定，除此之外，亦可將閉迴路系統中外界干擾對系統輸出的 -norm 壓低在一個範圍之內，使外界干擾對輸出的影響壓至最低，並利用模糊控制的優點，有效改善滑動模式出現在平衡點附近的顫抖現象。
最後，本文舉出兩個例題，例題一針對一具有非結構不確定性與外擾的非線性倒單擺系統作為模擬控制對象，來驗證本研究所設計之模糊滑動 控制器之可行性，並經由模擬結果，顯示本控制器能有效降低外擾對輸出的影響，且達到良好的追蹤性能；例題二針對水下載具進行航向與潛水控制，最終模擬結果顯示，本控制器在各種船速下皆能使系統完成追蹤，且有不錯的強健性能。

A nonlinear dynamic system usually contains some uncertainties, such as plant uncertainties and external disturbances, which may make the desired performance hard to be achieved or even cause the close-loop system unstable. This research proposes a fuzzy-sliding mode controller to resolve the above problem. The proposed controller is based on Lyapunov synthesis approach so that the close loop transfer function between the exogenous inputs and the controlled outputs of a nonlinear system can not only be stabilized but also be guaranteed to be bounded in a prescribed norm. In addition, in this study, a Fuzzy skill is added to the proposed composite control law to remove the chattering effects occurred in the sliding surface.
A nonlinear inverted pendulum system with unstructured uncertainty is given to illustrate the effectiveness of the proposed approaches. Then a six degree of freedom model of an underwater vehicle is used to demonstrate the feasiability of the proposed fuzzy-sliding mode H∞-autopilot by showing its performance in steering and diving. The computer simulation results reveal that the proposed fuzzy-sliding mode H∞-controller scheme is robust to the system uncertainties and disturbances and is able to achieve good tracking performance.

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