Robust control method for automatic berthing of unmanned ships based on weight optimal loop shaping

Abstract

Automatic berthing is one of the key functions for autonomous navigation of unmanned ships, and it is an important technology that assists and ensures ships complete their voyage tasks. To enhance the robustness, scenario universality, and disturbance resistance of automatic berthing technology, an automatic berthing method based on weight optimal loop shaping is proposed in this paper. Firstly, to enhance the robust stability margins of the berthing controller, the concept of weight optimization is introduced to transform the frequency-domain dependent weight optimization into an optimization problem with a finite number of frequency-domain independent constraints. Secondly, to improve the continuity and scenario universality of the algorithm, a transformation model between berth and earth coordinates is constructed using Bézier curves, and a forward Euler signal tracking method is introduced to provide a differentiable reference trajectory for the control system. Finally, the proposed method is validated through the construction of various berthing scenarios. The validation results indicate that the proposed method can achieve automatic berthing in different scenarios with better stability and disturbance resistance, and a theoretical reference is provided for the development of autonomous berthing technology for unmanned ships.