Ship Disturbance Estimation Using GNSS and Thrust Separation
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Solution Overview
Problem
Existing marine vessel control systems struggle to accurately estimate and account for disturbances such as wave and wind forces, making it difficult to maintain a fixed position or desired heading, which affects navigation accuracy and efficiency.
Innovation Solution
A disturbance estimation apparatus and method using a GNSS receiver, thrust data receiver, and processing circuitry to determine the magnitude and direction of external forces acting on a ship when the thrust force is below a threshold, allowing for precise control and display of disturbance data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position information from GNSS is used to estimate disturbance, then the system can provide disturbance estimation, but the accuracy is insufficient because it is difficult to distinguish thrust-induced movement from disturbance-induced movement
Solution Approach 1:
The patent extracts and separates the thrust force component from the total ship movement by introducing a thrust data receiver that specifically measures thrust force. This allows the system to isolate and remove the thrust-induced movement component from the position information, leaving only the disturbance-induced movement for accurate disturbance estimation.
Solution Approach 2:
The patent introduces thrust force as an intermediary variable that mediates between the ship's propulsion system and the position information. By measuring thrust force separately and using it to compensate for its effect in position data, the system can accurately extract disturbance information that would otherwise be hidden in the combined movement signal.
2Loss of time
If disturbance estimation is performed continuously, then timely disturbance detection is achieved, but the system complexity and computational load increase
Solution Approach 1:
The patent performs preliminary action by continuously measuring and storing thrust force data in advance. This pre-acquired thrust information is readily available when disturbance estimation is needed, enabling timely disturbance detection without requiring complex real-time separation calculations during disturbance events.
Solution Approach 2:
The patent implements feedback by continuously monitoring both position information and thrust force data, then using this feedback loop to calculate and update disturbance estimates in real-time. The disturbance estimation is fed back to the control system, which adjusts hull control accordingly, creating a closed-loop system that responds timely to disturbances.
3Reliability
If threshold-based disturbance detection is used, then false positives from normal thrust variations are reduced, but disturbances occurring during thrust application may be missed
Solution Approach 1:
The patent maintains continuity of useful action by continuously measuring both position information and thrust force data without interruption. This continuous dual measurement allows the system to accurately determine disturbance at any thrust level by comparing position changes with corresponding thrust force measurements, ensuring no disturbances are missed regardless of thrust state.
Data Source
AI summary
A disturbance estimation apparatus that includes a position data receiver, a thrust data receiver, and processing circuitry is provided. The position data receiver receives position data indicating a position of a ship. The thrust data receiver receives thrust data indicating a thrust force driving the ship during navigation. The processing circuitry determines a magnitude of the thrust force based on the thrust data, and determines, based on the position data, disturbance data including a drift direction in which the ship drifts due to an external force and a drift speed of the ship while the thrust force is less than a threshold value. The processing circuitry outputs the disturbance data that indicates disturbance acting on the ship and assists to control movement of the ship for automatically maintaining a selected position or heading direction of the ship.