Abstract
Dynamic obstacle avoidance is essential for unmanned surface vehicles (USVs) to achieve autonomous sailing. This paper presents a dynamic navigation ship domain (DNSD)-based dynamic obstacle avoidance approach for USVs in compliance with COLREGs. Based on the detected obstacle information, the approach can not only infer the collision risk, but also plan the local avoidance path trajectory to make appropriate avoidance maneuvers. Firstly, the analytical DNSD model is established taking into account the ship parameters, maneuverability, sailing speed, and encounter situations regarding COLREGs. Thus, the DNSDs of the own and target ships are utilized to trigger the obstacle avoidance mode and determine whether and when the USV should make avoidance maneuvers. Then, the local avoidance path planner generates the new avoidance waypoints and plans the avoidance trajectory. Simulations were implemented for a single obstacle under different encounter situations and multiple dynamic obstacles. The results demonstrated the effectiveness and superiority of the proposed DNSD-based obstacle avoidance algorithm.
Highlights
Unmanned surface vehicles (USVs) can perform various applications in various science, civilian, and military fields, such as environmental monitoring [1,2,3] and military defense [4,5]
distance to the CPA (DCPA) as the most dangerous target ship (TS); Determining the COLREGs encounter situation by calculating the relative bearing angle according to (5); Determining the shape of the dynamic navigation ship domain (DNSD) of the own ship (OS) and TSs in the xō ȳ coordinates according to Equations (6)–(10); Transforming the DNSDs along with the position and heading of the ships according to Equations (11)–(12); Assessing the collision risk by (13) and determining the navigation mode: obstacle avoidance or path following; Determining the new obstacle avoidance waypoint according to COLREGs using (14)
This paper proposed a dynamic navigation ship domain-based (DNSD-based) dynamic obstacle avoidance algorithm for USVs in compliance with COLREGs
Summary
Unmanned surface vehicles (USVs) can perform various applications in various science, civilian, and military fields, such as environmental monitoring [1,2,3] and military defense [4,5]. Referring to Szlapczynski and Szlapczynska [13], ship domains can be implemented in an encounter situation with four safety criteria (see Figure 1) Based on these criteria, ship domains are commonly used in obstacle avoidance alerting systems to assess the collision risk and answer whether and when to make evasive maneuvers [15,20,21]. The SBG algorithm overcomes the wiggling behavior caused by the VO when the velocity is between multiple obstacles and reduces the wear of the USVs. since the reaction and safety area are set as circles with constant radii, the radii cannot reflect the influences of the sailing speed and different encounter situations.
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