Prescribed-performance time-delay compensation control for UUV trajectory tracking in main-branch water conveyance tunnel transitions under unknown input delays

This study presents a novel control framework with delay compensation and prescribed performance guarantees for unmanned underwater vehicles (UUVs) trajectory tracking control in main-branch water conveyance tunnel transitions inspection tasks, addressing systems subject to uncertain time-varying input delays. The methodology integrates prescribed performance functions with a backstepping technique to develop virtual control laws, thereby ensuring bounded transient and steady-state tracking errors. Additionally, the study implements a delay compensator based on the integral of historical control inputs and estimation of uncertain input delays, effectively mitigating the adverse effects of unknown time-varying delays on trajectory tracking performance. Through the construction of Lyapunov-Krasovskii (L-K) functionals and Lyapunov theory, uniform ultimate boundednes of all closed-loop signals is rigorously proven. Simulation and field test results demonstrate that the proposed method maintains tracking errors within prescribed bounds, ensure both transient and steady-state control performance, and significantly enhance navigation safety for UUVs in tunnel entry/exit scenarios.