A Reference Trajectory-Based Approach to Safe and Efficient Trajectory Planning for an Overactuated River Ferry

Abstract

The planning of safe trajectories that are also time and energy efficient is an important part of automated ships. During trajectory planning, the expected motion of other traffic participants as well as the dynamic capabilities of the own vessel need to be considered. This paper presents a variation of the path-velocity decomposition (PVD) approach that builds upon a predefined reference trajectory instead of a reference path. By solving a shortest-path problem, collisions with dynamic obstacles are avoided. Collisions with static obstacles are inherently ruled out by selecting a suitable reference trajectory. The proposed method ensures dynamic feasibility and energy efficiency of the optimized trajectory using a detailed powertrain model. In addition, the collision detection is divided into a broad and narrow phase to reduce calculation time. As a concrete application, the trajectory planning is designed for a double-ended river ferry with four cycloidal propellers. The proposed method is tested within an exemplary traffic scenario with three dynamic obstacles using a high-fidelity vessel simulator. The results show the ability of the presented approach to generate collision-free and energy efficient trajectories that can safely be calculated within the required cycle time of 5 s. Using multiple reference trajectories in parallel and a velocity-dependent ship orientation offers potential for improvement for future research.