Decentralized Linear Convoying for Underactuated Surface Craft with Partial State Coupling

This work introduces a novel decentralized algorithm and control law for stable linear convoying using a layered control approach. This algorithm was implemented in MOOS-IvP, using an abstraction layer that models a virtual system decoupled from the system’s actual dynamics. This makes the algorithm platform-agnostic and able to be combined with other behaviors such as collision avoidance and operating region behaviors. A trajectory defined by a lead agent is discretized and embedded with the leader’s dynamics and propagated to all following agents. We first demonstrate that this approach when paired with a simple PD controller prevents accumulated errors and improves trajectory tracking for follower agents. Thereafter we demonstrate how virtually coupling a subset of agent states improves the overall cohesiveness of the convoy. Improvements are demonstrated in both simulations and field trials using five autonomous surface vehicles.