A Reactive Collision Avoidance Algorithm for Vehicles with Underactuated Dynamics

This paper presents a reactive collision avoidance algorithm, which avoids both static and moving obstacles by keeping a constant avoidance angle between the vehicle velocity vector and the obstacle. In particular, we consider marine vehicles with underactuated sway dynamics, which cannot be directly controlled. This gives an underactuated component in the vehicle velocity, which the proposed algorithm is designed to compensate for. The algorithm furthermore compensates for the obstacle velocity. Conditions are derived under which the sway movement is bounded and collision avoidance is mathematically proved. The theoretical results are supported by simulations. The proposed algorithm makes only limited sensing requirements on the vehicle, is intuitive and suitable for a wide range of vehicles. This includes vehicles with heavy forward acceleration constraints, which is demonstrated by applying the algorithm to a vehicle with constant surge speed.