Hierarchical Vessel Autonomous Operation in a Port with Safety Certificates: Combined MPC and CBF Approach

In this paper, we investigate autonomous vessel operation in/near a port and present a novel hierarchical control architecture that combines model predictive control (MPC) and control barrier function (CBF). Our architecture is composed of two layers, navigation and control, and switches control schemes as the ideal vessel operations vary depending on the vessel locations. Specifically, we divide the operation into three phases, namely approaching phase, breakwater passing phase, and docking phase. In all phases, we employ the CBF-based online optimization with a vessel kinematic model at a lower layer to certify safety even in the presence of the prediction error in the navigation layer. The navigation layer is designed based on MPC so as to smoothen the collision avoidance behavior and to reflect various specifications stemming from laws. The present control architecture is demonstrated through various simulations including the one with real data of vessels in Tokyo Bay.