Virtual STW Sensor Using Hydrodynamic Modeling for Marine Vessels
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Solution Overview
Problem
Conventional methods for measuring the speed through water (STW) of marine vessels are plagued by noise issues, calibration errors, and inaccuracies, especially in environments with low water impurities, and rely on multiple data sources prone to errors.
Innovation Solution
A method and sensor system that combine propeller revolutions per minute, torque, propulsion power, and thrust data with hydrodynamic modeling, along with speed over ground measurements, to determine STW accurately, using a statistical state-space model and oceanographic current data for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler Log is used to measure STW, then speed measurement is possible, but noise level is high and measurement precision deteriorates
Solution Approach 1:
The patent combines multiple data sources (Doppler Log STW measurements, propeller RPM, torque, propulsion power, thrust, and speed over ground) into a unified statistical state-space model. This merging of data sources allows the system to cross-validate measurements and filter out noise, thereby improving both measurement precision and reliability simultaneously.
Solution Approach 2:
The patent implements a feedback mechanism where the statistical state-space model continuously processes incoming data from multiple sensors and adjusts the STW estimation in real-time. The model uses feedback from the relationship between propeller parameters and vessel motion to correct Doppler Log measurements, reducing noise and improving measurement reliability.
2Measurement precision
If Doppler Log is used to measure STW, then speed measurement is possible, but calibration errors occur and long-term accuracy deteriorates
Solution Approach 1:
The statistical state-space model continuously compares the relationship between propeller parameters (RPM, torque, power, thrust) and vessel motion against expected hydrodynamic relationships. This feedback mechanism detects calibration drift over time and automatically corrects it, preventing long-term accuracy deterioration without requiring manual recalibration.
Solution Approach 2:
The system performs self-calibration by using the inherent relationships between propeller parameters and vessel motion as reference standards. The statistical model automatically adjusts calibration parameters based on the consistency of physical relationships, enabling the system to maintain accuracy without external intervention or multiple data sources.
3Measurement precision
If multiple data sources are used to approximate STW, then accuracy may improve, but device complexity increases
Solution Approach 1:
The statistical state-space model serves multiple functions simultaneously: it processes Doppler Log data, integrates propeller parameters, calculates thrust and power relationships, and performs calibration correction. This multi-functionality allows the system to achieve high measurement accuracy using a single integrated model rather than multiple separate systems, reducing overall device complexity.
Solution Approach 2:
The patent merges the processing of multiple data sources into a single statistical state-space model that handles all inputs (Doppler Log, RPM, torque, power, thrust, speed over ground) uniformly. This consolidation reduces the complexity that would arise from managing multiple separate data processing systems while maintaining the accuracy benefits of using multiple sources.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a robust and accurate STW measurement, reducing noise and calibration errors, and eliminating the need for multiple data sources, thereby optimizing vessel operation and energy efficiency.
Implementation Method 1
The most common sensor type to measure STW for a vessel is the Doppler Log, which transmits ultrasound pulses from the vessel, and measures the backscatter echo. The frequency shift (Doppler shift) can be utilized to calculate the speed of the vessel through water.
Data Source
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AI summary
Disclosed are a method and a virtual sensor system for determining the speed through water of a marine vessel. The method includes obtaining propeller revolutions per minute and at least one of torque at propeller, propulsion power, thrust and engine fuel flow, obtaining speed over ground of the vessel and using the obtained data and hydrodynamic modelling to determine the speed through water of the vessel.