Distributed Fixed-Time Nonsingular Terminal Sliding Mode Time-Varying Formation Control of ASVs Based on Hierarchical Control Mechanism

This paper presents a distributed fixed-time nonsingular terminal sliding mode (FxTNTSM) time-varying formation control scheme based on a hierarchical control mechanism (HCM) for autonomous surface vessels (ASVs) with model parameter uncertainties and unknown environment disturbances. The HCM includes a distributed estimation layer and a local time-varying formation control layer. Specifically, in the distributed estimation layer, a distributed fixed-time estimator (DFxTEO) is designed to estimate the leader’s state information. In the local time-varying formation control layer, a fixed-time integral sliding mode disturbance observer (FxTISMDO) is designed to estimate the compound disturbances lumped by uncertain dynamics and unknown ocean environment disturbances within a fixed settling time. A distributed time-varying formation control law for multiple ASVs is developed by incorporating the DFxTEO and the FxTISMDO into the FxTNTSM technique. Theoretical analyses and simulation studies show that the developed formation control law enables the multiple ASVs to achieve the desired formation control, and the formation errors can converge to origin within a fixed settling time.