A Control Barrier Function Composition Approach for Multiagent Systems in Marine Applications

Abstract

The agents within a multiagent system (MAS) operating in marine environments often need to utilize task payloads and avoid collisions in coordination, necessitating adherence to a set of relative-pose constraints, which may include field-of-view, line-of-sight, collision-avoidance, and range constraints. A nominal controller designed for reference tracking may not guarantee the marine MAS stays safe w.r.t. these constraints. To modify the nominal input as one that enforces safety, we introduce a framework to systematically encode the relative-pose constraints as control barrier functions (CBFs) and combine them as a composite nonsmooth CBF (NCBF) using Boolean composition, which enables a less conservative safe control design compared to enforcing the individual CBFs. Within the relative-pose constraints, the challenging line-of-sight constraint is derived from a minimum distance function whose derivative is not explicit. Involving it in the composition renders the resulting NCBF not enforceable through existing safe control design methods. To address this challenge, we propose a novel quadratic program formulation based on the dual of the minimum distance problem and develop a new theory to ensure the resulting control input guarantees constraint satisfaction. Lastly, we validate the effectiveness of our proposed framework on a simulated marine MAS and a real-world marine MAS comprising one autonomous surface vehicle and two autonomous underwater vehicles.