| Summary: | In this paper, a new hybrid robust tracking control for an underwater vehicle in dive plane via H ∞ method and time-variant sliding mode control is designed. The proposed controller is composed of two control signals. One control signal is designed via time-variant sliding function based on time-variant rejection parameter, and the other control signal is designed based on H ∞ control approach. The underwater vehicle dynamics are nonlinear uncertain dynamical equation with unknown external disturbances. Therefore, in this paper, an observation of the external disturbance with a time-variant gain parameter is designed. The proposed method eliminates the effects of uncertainties and chattering phenomenon. Also, the time-variant sliding function filters all the unmodeled frequencies and external noises, such as a chain of ( n − 1 ) first-order adaptive low-pass filters. A new theorem, for facilitating the presented method, is proved. Finally, two examples for demonstrating the advantages of the proposed method are simulated.
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