Safety and COLREG evaluation for marine collision avoidance algorithms

Abstract

Verification is a necessary step in system development, so too for autonomous surface vehicles (ASVs). However, formal and analytical verification methods are not well suited for such highly complex systems. Simulation-based testing has therefore been proposed as a viable approach. This would require numerous simulations to be performed and evaluated, raising the need for automatic evaluation.An important assessment measure with regards to ASV safety, is the degree of International Regulations for Preventing Collisions at Sea (COLREG) compliance. One important aspect of these rules is vessel behavior in situations where a risk of collision with other vessels is present.This paper presents a comprehensive method for automatic evaluation of collision avoidance maneuvers in terms of safety and compliance with a subset of the COLREG steering and sailing rules. The rules are formulated as mathematical expressions, and insight is given into the authors’ interpretation of the rules through the choice of values for parameters and weights. Results from simulated encounters and from encounters between vessels in normal operation show the method’s capability to correctly identify situations and detect and penalize undesired behaviors. They also evoke the need for more research into how to interpret the COLREG in terms of angles, velocities, and distance between vessels.