Autonomous ship berthing with reachability analysis based on Zonotopes

Abstract

Recently, autonomous ships in the field of shipbuilding have become popular. Among the various technologies of autonomous ships, autonomous berthing is very important. Thus, a technology called dynamic positioning exists and is used for maintaining an absolute position in a marine environment using an omnidirectional thruster. However, since ships used for autonomous berthing generally lack control power, berthing them in a disturbed environment using only classical control is difficult. Therefore, this study aimed to determine in advance whether a ship can berth and to take precautions by determining whether the current input does not deviate from the berthing trajectory within the disturbance through reachability analysis. Through backward reachability analysis, an area in which berthing can be performed is obtained in advance within a specific time, and when the vessel reaches this area, a berthing path is created and the berthing phase begins. We present a safe and efficient berthing algorithm through forward reachability analysis in the berthing stage. The performance of the proposed algorithm through forward reachability analysis was validated through a berthing simulation.