Fuzzy finite-time depth control for unmanned underwater vehicles subject to actuator and sensor faults

This paper investigates the finite-time depth control problem for unmanned underwater vehicles (UUVs) in the presence of both actuator and sensor faults. First, UUVs affected by sea current perturbations and uncertainties are modeled using Takagi–Sugeno (T-S) fuzzy model. In particular, both actuator and sensor faults are considered in the designed model. As a result, the applicability of UUVs in complex marine environments is improved. Second, a fuzzy observer is developed to simultaneously estimate unknown system states and faults. Based on the output of the observer, a novel fuzzy fault-tolerant controller is established to compensate for the effects of faults and sea current perturbations, ensuring the stability of the system. Third, a Lyapunov–Krasovskii functional (LKF) dependent on fuzzy membership functions (FMFs) is constructed, and sufficient conditions are derived to guarantee finite-time stabilization of UUVs with H ∞ performance. Finally, a simulation example is provided to verify the feasibility and effectiveness of the proposed approach.