Marine Vessel Positioning via Alternating Propulsion Subsets
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Solution Overview
Problem
Existing marine vessel positioning systems face challenges in accurately and efficiently maintaining a vessel's position and heading, particularly in the presence of external forces like wind and waves, and can overshoot target positions due to large thrust increments from propulsion devices.
Innovation Solution
A control module communicates with marine propulsion devices to calculate and correct position and heading errors using a PID feedback controller, and strategically activates subsets of propulsion devices to minimize errors, reducing overall thrust and preventing overshoot by alternating thrust production between subsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all propulsion devices are activated to minimize position error, then positioning precision is improved, but the risk of overshooting target position increases
Solution Approach 1:
The propulsion device group is segmented into multiple subsets that are activated alternately. Instead of activating all propulsion devices simultaneously, the system divides them into groups and switches between groups, reducing the total thrust applied at any given time while maintaining positioning precision through coordinated control.
Solution Approach 2:
The system implements periodic activation of propulsion device subsets by switching between different groups at regular intervals. This periodic action allows the vessel to make gradual positional adjustments without applying continuous full thrust, thereby preventing overshooting while maintaining positioning accuracy.
2Speed
If large thrust increments are applied to correct position errors, then response speed is improved, but positioning precision deteriorates
Solution Approach 1:
The system applies partial thrust by activating only a subset of propulsion devices at any given time rather than all devices. This partial action provides sufficient response speed to correct position errors while avoiding excessive thrust that would compromise positioning precision.
Data Source
AI summary
A method for positioning a marine vessel includes receiving a measured actual position of the vessel and determining a first error between the actual position of the vessel and a desired target position of the vessel. In response to the first error being in a fore/aft direction of the vessel, the method includes commanding a first subset of marine propulsion devices in a plurality of marine propulsion devices to produce thrust to minimize the first error in the fore/aft direction, as appropriate, while a remainder of the marine propulsion devices in the plurality do not produce thrust. The method thereafter includes commanding the first subset of marine propulsion devices to cease producing thrust. The method may also include selecting whether to actuate all marine propulsion devices in the plurality of marine propulsion devices or a first subset thereof based on a magnitude and a direction of the first error.