Integrated Guidance and Motion Control for USV Collision Avoidance

In coastal waters, the navigable domain of unmanned surface vehicles (USVs) is restricted due to irregular static obstacles and encountered vessels, which increases the collision risk (CR) of a USV with encountered vessels and hence collision avoidance (COLAV) maneuvers of the USV will increase its sailing distance. This paper proposes a new integrated guidance and motion control scheme for the COLAV of USVs with encountered vessels based on the idea of nonlinear model predictive control (NMPC). An integral-type objective function of NMPC is designed as a function with respect to the heading deviation, surge speed, and distance from the USV position at instant t to its next waypoint position in the planned path over a prediction time horizon. The navigable domain of the USV, CR indexes of the USV with encountered vessels, USV dynamics, etc., are taken as the constraints of the objective function. Using a nonlinear programming technique, we obtain optimal solutions minimizing the objective function subject to the constraints, i.e., the optimal thrust and yaw moment for the integrated guidance and motion control for the COLAV of the USV with encountered vessels. Simulations and simulation comparison results on the USV and four other vessels demonstrate that, under the proposed integrated guidance and motion control scheme, the USV avoids collisions with encountered vessels along a shorter route with a lower CR.