Global event-triggered inner–outer loop stabilization of under-actuated surface vessels

Abstract

An event-triggered controller (ETC) for global full-state stabilization of under-actuated surface vessels (USVs) is proposed. Based on an inner–outer loop structure with Lyapunov control design technique, the USV dynamics are separated into two subsystems to facilitate the design and stability analysis. A time-varying variable is constructed to design the desired velocities used as virtual control inputs to stabilize the under-actuated outer loop subsystem. For the fully-actuated inner loop subsystem, the actual control force and moment inputs are designed using a switching threshold event-triggering mechanism (SWT-ETM) to drive the actual velocities to the desired ones, thereby the inner loop subsystem and the closed-loop system are stabilized. The proposed ETC guarantees global asymptotical convergence of the stabilization error by choosing proper control parameters. It also significantly reduces the times for communication and the actuator burden while provides stable and accurate control performance. Simulation results are carried out to illustrate the effectiveness of the proposed scheme.