Novel Formulation for Line of Sight Guidance and Obstacle Avoidance for Under-actuated Ships

Automatic control of under-actuated ships is a challenging task due to the external factors and limited actuators onboard a ship. It is even more so when the controller needs to seamlessly integrate with a guidance system and obstacle avoidance for the purpose of autonimity. In this paper, line of sight guidance system for marine surface vessels is augmented to include obstacle avoidance. The process of directing the ship movement to avoid a stationary and moving obstacles is tackled by introducing an iterative mathematical formulation for the circle of avoidance algorithm. Unlike learning based guidance system, the proposed formulation has an explicit solution that is updated at each instant in time. Three simulations are conducted to assess the performance of the overall guidance and avoidance system. The developed algorithm is validated through simulation results of a 6-degree of freedom model of a ship. The simulation results prove the effectiveness of the developed technique to converge the ship to the desired trajectory autonomously while avoiding obstacles along the path. Key-Words: Ship guidance system, trajectory planning, Line-of-Sight (LOS), Circle-of-Avoidance (COA) and obstacle avoidance. Received: January 15, 2021. Revised: February 25, 2021. Accepted: March 8, 2021. Published: March 16, 2021.