Event-Triggered Formation and Obstacle Avoidance Control for Multiple USVs With Disturbance Observation

Abstract

This paper addresses the formation control problem of multiple unmanned surface vehicles (USVs) in maritime environments characterized by strong disturbances, nonlinear uncertainties, and obstacle constraints. Accordingly, a disturbance-observed adaptive event-triggered formation control method is proposed. First, a sliding-mode-enhanced extended-state observer (SMESO) is designed to estimate external disturbances. At the same time, an online radial basis function neural network (RBFNN) is introduced to perform gated compensation of the estimation residuals. Second, a distributed robust guidance law is constructed based on an auxiliary error system, utilizing smoothing and adaptive disturbance compensation to improve the convergence of formation errors and disturbance rejection capability. Furthermore, a geometric local obstacle avoidance strategy based on time-to-collision (TTC) is proposed, employing a stable side-selection mechanism and virtual tangent-point construction. The method ensures consistent avoidance direction and trajectory feasibility. To reduce control update and communication loads, an adaptive event-triggered mechanism (AETM) is designed that combines the rate of change in disturbance estimates and tracking error with communication broadcast conditions tailored to neighbor-based information exchange. Theoretical analysis demonstrates that the proposed method ensures the closed-loop system is consistently bounded, enabling stable formation and safe obstacle avoidance in perturbed environments. Simulation results verify the effectiveness of this method under complex sea conditions and highlight the advantages of the event-triggered mechanism. Note to Practitioners—As the use of multiple USVs in real-world maritime missions continues to grow, balancing operational efficiency with mission performance under limited energy constraints has become a central challenge in engineering practice. This paper proposes a disturbance-observed adaptive event-triggered formation control method tailored for energy-sensitive and computationally constrained multi-USV systems. It is applicable to mission scenarios such as cooperative patrols and urgent search-and-rescue operations, where obstacles are modeled using circular safety envelopes to approximate buoys, anchored vessels, and offshore structures. This framework organically integrates disturbance estimation, robust control, obstacle avoidance strategies, and event-triggered mechanisms. Theoretical proofs and simulations using actual model parameters obtained from experiments have validated the engineering feasibility of the proposed method. However, the current method is based on the assumption of ideal sensors and does not account for network uncertainties such as communication interruptions and data packet loss. Future work will further investigate formation control methods under complex network conditions to enhance the systems reliability and engineering applicability in real marine environments.