  Energy efficiency and safety are two critical objectives for marine vehicles
operating in environments with obstacles, and they generally conflict with each
other. In this paper, we propose a novel online motion planning method of
marine vehicles which can make trade-offs between the two design objectives
based on the framework of economic model predictive control (EMPC). Firstly,
the feasible trajectory with the most safety margin is designed and utilized as
tracking reference. Secondly, the EMPC-based receding horizon motion planning
algorithm is designed, in which the practical consumed energy and safety
measure (i.e., the distance between the planning trajectory and the reference)
are considered. Experimental results verify the effectiveness and feasibility
of the proposed method.
