Underactuated Autonomous Underwater Vehicle Time-Varying Formation Consensus Control With Multiple Actuator Constraints

This article addresses the challenges of actuator constraints in underactuated autonomous underwater vehicles (AUVs) during the design of time-varying formation controllers. It focuses specifically on actuator input saturation, actuator faults, and frequent actuator use. A novel distributed saturation and fault-tolerant time-varying formation consensus (TVFC) control system, incorporating a dynamic event-triggering mechanism, is proposed. First, to address the TVFC, a reference trajectory is generated for each AUV using neighbor information and formation information. Error tracking is performed using the dynamic equation in a noninertial polar coordinate system, with the AUV as the origin. A saturation function is employed in controller design to ensure that the actuator input remains within its upper bounds. A constrained Lyapunov function is constructed to prove the stability of the system. Subsequently, a saturated observer is used to detect disturbances and faults, compensating for actuator input errors caused by faults. The observer also estimates the severity of actuator faults based on triggered sampling outcomes. Finally, a dynamic event-triggered mechanism is implemented to reduce the operating frequency of the actuators. Simulation results demonstrate the effectiveness of the proposed control algorithm in achieving TVFC control and fault tolerance while respecting actuator input saturation constraints. Additionally, the algorithm enables effective monitoring of actuator health status and reduces actuator execution frequency. Field experiments with two underactuated AUVs partially verify the feasibility of the proposed method.