Event-triggered practical fixed/predefined-time formation control of multiple unmanned surface vehicles with obstacle avoidance

To obtain a fixed/predefined-time stability criterion with low tracking errors against unknown disturbance, a new fixed/predefined-time criterion is proposed, which is more general for facilitating the control design, and can converge to a smaller residual set. Moreover, an improved event-triggered mechanism related to the collision risk is devised. In narrow environment, the threshold in the triggered condition is low, while it is high in open area. In addition, an obstacle avoidance mechanism, simultaneously including formation-keeping and physical limitations such as actuator saturation is designed. The distance between the follower and the leader ship changes dynamically, allowing for better coordination in obstacle avoidance. Finally, the control scheme is verified through formation control of multiple unmanned surface vehicles. The numerical results validate that it is collision free, and reduces overall trajectory tracking error with the presence of disturbance and uncertainties.