Event-triggered cooperative path following control for underactuated AUVs based on adaptive fixed-time disturbance observer

This study introduces a three-dimensional cooperative path-following control strategy with fixed-time convergence and event-triggered mechanisms for underactuated autonomous underwater vehicles (AUVs), employing an adaptive fixed-time disturbance observer (AFTDO) to handle model inaccuracies and uncertain current disturbances. Initially, an AFTDO is constructed to achieve composite disturbance estimation within a fixed time, independent of prior disturbance information. Following this, a three-dimensional fixed-time line-of-sight (LOS) guidance framework is formulated to produce reference velocity commands. For the purpose of attaining fixed-time synchronized path tracking, a consensus-driven controller is additionally devised for coordinating path variables. Moreover, an event-triggering mechanism with dynamic thresholds is integrated. Building upon this mechanism, a fixed-time dynamic controller is developed that employs event-triggered integral sliding mode control techniques. The proposed approach not only substantially decreases the actuation update rate and reduces mechanical wear on actuators, but also improves overall system performance. Utilizing Lyapunov stability analysis, the complete closed-loop system is shown to exhibit global fixed-time stability. Simulation results confirm the effectiveness and advantages of the designed control strategy.