A two-level dynamic obstacle avoidance algorithm for unmanned surface vehicles

Abstract

The unmanned surface vehicles (USVs) are required to perform a dynamic obstacle avoidance during a task. This is essential for USV safety in case of an emergency and this work has been proved to be difficult. However, little research has been done in this area. This paper focuses on an obstacle avoidance problem where the USVs are confronted with a moving ship. A two-level dynamic obstacle avoidance algorithm is introduced by combining the velocity obstacle (VO) algorithm with the improved artificial potential field (APF) method in a non-emergency situation, by using the VO algorithms to establish the velocity vector relationship between the USV and obstacles, both the obstacle avoidance and the goal approaching are considered. During an emergency, a compound potential field is formed around the obstacles. The field is composed of a repulsive potential field and a centrifugal potential field. Under its influence, only the collision avoidance is considered to ensure safety. Finally, numerical simulations are performed with the help of the particle swarm optimisation (PSO) method in order to improve the computational efficiency and accuracy. The results validated the feasibility and validity of the two-level dynamic obstacle avoidance algorithm.