A COLREG-Compliant Ship Collision Avoidance Algorithm

The compliance with the navigation rules plays a primary role in the development of routing algorithms to be applied in autonomous navigation. For such a reason this paper presents the mathematical formulations necessary to implement the Collision Regulations (COLREGs) within a previously developed ship path planning algorithm. The proposed approach is designed to be part of a decision support system for the bridge operators, in order to enhance traditional navigation; or, looking forward, to be part of the autonomous ship guidance system. Unlike other approaches that can be found in the scientific literature, the proposed work relies on the algebra of vectors, in order to describe the different scenarios as provided for in the COLREGs. The formulations to handle: head-on, crossing and overtaking, are formalized, described in detail and discussed. Eventually, some test cases are presented to show the effectiveness of the implementation of the proposed modeling into a Rapidly-exploring Random Tree (RRT*) algorithm. A simplified ship simulator is embedded in the algorithm to generate feasible solutions, taking into account the ship's manoeuvring capability.