Twin-Rudder Steering Angle Correction Under Wind and Current Drift
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Solution Overview
Problem
Conventional autopilots for ships struggle to maintain a precise course in challenging conditions such as strong winds, waves, and sea currents, particularly in congested waters, and lack the ability to automatically correct for deviations from the planned route.
Innovation Solution
A steering system for single-propeller twin-rudder ships that integrates a digital twin computation to simulate hull motion, calculates corrective rudder angles based on actual and assumed hull positions, and adjusts steering to account for external forces, ensuring precise navigation and collision avoidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional autopilot is used to maintain course, then the ship can navigate automatically on open ocean, but the ship cannot correct position deviation from course line caused by wind, waves, or currents
Solution Approach 1:
The system continuously measures the ship's actual position using GPS and compares it with the planned course line, then automatically calculates and applies corrective rudder angles to eliminate position deviation, forming a closed-loop feedback control system that maintains both automation and position accuracy
Solution Approach 2:
The invention replaces conventional mechanical autopilot systems with an electronic control system that uses GPS position data, external force calculation, and automated rudder angle computation to achieve both automatic navigation and precise course line maintenance
2Measurement precision
If manual steering is used to maintain high accuracy course in congested waters, then position precision can be maintained, but automation is lost and operator burden increases
Solution Approach 1:
The system performs self-correction by automatically detecting position deviation from the course line and independently calculating the necessary rudder angle adjustments without requiring manual intervention, thereby maintaining high position accuracy while preserving automation
3Speed
If large rudder angles are applied for quick maneuvering in congested waters, then response time is reduced, but ship stability and control precision deteriorate
Solution Approach 1:
The system dynamically adjusts rudder angle parameters based on real-time conditions, calculating optimal rudder angles that achieve the necessary maneuvering response while maintaining control precision through continuous optimization of steering parameters
4Reliability
If external forces such as wind, waves, and currents are not compensated, then steering system remains simple, but the ship deviates from planned route in adverse conditions
Solution Approach 1:
The system introduces an external force calculation module that acts as an intermediary, measuring and quantifying the effects of wind, waves, and currents, then using this information to pre-calculate compensatory rudder angles that counteract these forces and maintain route accuracy
Data Source
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AI summary
A digital twin computation section 291 collects a speed of an own ship, a position of the own ship, and a heading of the own ship in real time, and reproduces an actual hull motion of the own ship realized at a current steering angle on a navigational electronic marine chart. A simulation computation section 292 displays, on the navigational electronic marine chart, an assumed hull motion of the own ship determined by calculation that assumes that a force acting on the hull is a driving force at the current steering angle. A resultant force of external forces computation section 293 calculates an acting direction and a magnitude of a resultant force of external forces acting on the hull based on a ship speed difference, ship position difference, and heading difference between the actual hull motion and the assumed hull motion. A specified rudder angle computation section 294 calculates a corrective rudder angle for resisting the resultant force of external forces, and calculates an appropriate steering angle by correcting the current steering angle with the corrective rudder angle.