Obstacle Avoidance and Trajectory Optimization for an Autonomous Vessel Utilizing MILP Path Planning, Computer Vision based Perception and Feedback Control

The framework of an autonomous vessel is typically composed of three distinct and independent blocks known as the Guidance, Navigation and Control (GNC) system. Whilst independent in their focus, the subsystems are nonetheless reliant on one another for a vessel to competently operate. This paper investigates the potential of using a combination of advanced complementary techniques in the different GNC subsystems to improve upon the current common practices/state of the art in obstacle avoidance. The novel Guidance system is based on Mixed Integer Linear Programming (MILP). This optimisation technique allows quick, robust path planning with the possibility for a variety of constraints. The feasibility of this method will be investigated with the goal of providing optimal path planning in the presence of static and dynamic obstacles during autonomous sailing operations. Within the Navigation System, a multi-modal neural network architecture is proposed for the perception branch to provide high-level situational awareness for collision avoidance purposes. The computer vision approach allows for the vessel type, position and orientation all to be extracted for encounters with both dynamic and static obstacles using only imaging sensors. Two Control methods are studied in the paper, an error-based PID control strategy as well as an MPC control scheme. These two techniques will be compared to evaluate the performance and reviewing the suitability for use within the specific GNC scheme and the generic application environment. This paper details the specific implementation of each system within the overall framework, presents simulation results of the path planner and control strategy, with a performance evaluation of the navigation system using an experimental dataset. The results obtained are analysed through qualitative discussion as well as quantitative performance indicators and key conclusions are consequently drawn.