On the Field Test of the Autonomous Collision Avoidance Among the Swarm of Four Unmanned Surface Vehicles

International Maritime Organization (IMO) adopted the term of Maritime Autonomous Surface Ships (MASS) as a concept of future ship at the Maritime Safety Committee (MSC) in 2017. IMO MSC is crafting a new, non-mandatory MASS code for adoption as early as 2025. Unmanned Surface Vehicle (USV) has been developed in order to perform dangerous missions instead of manned vehicle in bad sea weather condition. USV is a small boat as a kind of small MASS and it can be controlled remotely or autonomously. Since 2020, Korea Research Institute of Ships and Ocean Engineering (KRISO) has newly developed ARAGON CAT40 as a catamaran unmanned surface vehicle (USV) under the financial support of KOREA Ministry of Science and ICT. It has the length of 11 meters and the displacement of about 10 tons with electric twin motors and sail-drives. On the other hand, USV has heavier payloads and longer operation distance in sea area than aerial drone and the swarm of USVs are more effective for maritime mission than single USV. In KRISO, the operation system of the swarm of USVs for sea surveillance has been developed since 2019. Previously, the swarm autonomous navigation system (SANS) for collision avoidance was tested in in-land water by using USV swarm. Now, we would like to evaluate the performance of autonomous collision avoidance of ARAGON 1, ARAGON2, ARAGON3 and ARAGON CAT40 through field tests in the actual sea area. For safe navigation among the swarm of four USVs, they should keep the convention on the international regulations for preventing collisions at sea, 1972 (COLREGs). Collision avoidance algorithm in SANS is implemented by using changeable action space searching, which can be flexibly changed according to the collision risk (CR) based on fuzzy inference. Each USV can navigate autonomously without human operation by using SANS. In the actual sea area, field tests are carried out in order to evaluate the performance of collision avoidance algorithm among the swarm of four USVs and ensure the robustness of swarm operation on the four USVs. Scenarios are tested on the dangerous colliding situations such as head-on, crossing and their combinations among the swarm of four USVs. In this paper, the main features of SANS and main results of field tests on autonomous collision avoidance among the swarm of four USVs are described.