Finite-Time Disturbance Observer Based Fuzzy Terminal Sliding Mode Depth Control for Underwater Vehicles

Automatic depth control is an essential function for all kinds of underwater vehicles. To deal with both the matched and mismatched disturbances and parameter uncertainties of the underwater vehicles and obtain finite-time convergence, a novel control method combining terminal sliding mode control and finite-time disturbance observer is proposed in this work. The stability of the controller is proved by the Lyapunov stability theory and verified by a numerical simulation example. The simulation results show that the proposed control method has satisfying dynamic tracking performance and high accuracy against disturbances and system uncertainties. Most importantly, the controller can converge in a desired time which is an appealing and competitive characteristic compared to other control technologies.