A 3D Reactive Collision Avoidance Algorithm for Underactuated Vehicles

Abstract

This paper presents a 3D reactive collision avoidance algorithm for vehicles with underactuated dynamics. The underactuated states cannot be directly controlled, but are controlled indirectly by steering the direction of the vehicle's velocity vector. This vector is made to point a constant avoidance angle away from the obstacle, thus ensuring collision avoidance, while the forward speed is kept constant to maintain maneuverability. We choose an optimal pair of desired heading and pitch angles during the maneuver, thus taking advantage of the flexibility provided by operating in 3D. The algorithm incorporates limits on both the allowed pitch angle and the control inputs, which are limits that often are present in practical scenarios. Finally, we provide a mathematical proof that the collision avoidance maneuver is safe, and support the analysis through several simulations.

A 3D reactive collision avoidance algorithm for underactuated underwater vehicles

“…Only the vehicle kinematics was considered in Wiig et al (2018a). In Wiig et al (2018b), the design and analysis of the algorithm also included the important underactuated dynamics of an underactuated marine vehicle. This necessitates the design of a Flow frame controller, a controller steering the direction of the vehicleʼs velocity vector.…”

“…By smoothing the required pitch and yaw rate during the discrete switch from nominal operation when starting the collision avoidance maneuver, we ensure that all the control signals in the system remain well defined. Furthermore, while Wiig et al (2018aWiig et al ( , 2018b only considered static obstacles, we will in this paper extend the algorithm to also include moving obstacles by compensating the cone of safe directions for the obstacleʼs velocity. The compensation is dependent also on the vehicle speed, which contains an underactuated component when the vehicle is turning.…”