Underwater Sensor Synchronization for Accurate Acoustic Ranging
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Solution Overview
Problem
Conventional methods for measuring underwater distances between sensor modules and a reference point, such as a vessel, are inaccurate due to varying sound propagation velocities in water, which depend on factors like temperature, salt content, and pressure, making precise distance measurement challenging.
Innovation Solution
A method involving a hydrophone unit and a pair of sensor modules that send synchronization and data signals to determine bearing angles and calculate distances using time values, accounting for delays and employing hydrophones to measure arrival times and angles relative to a reference point, with calculations based on a system of equations or dichotomy processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acoustic signals are used to measure underwater distances, then distance measurement can be performed without physical contact, but measurement precision deteriorates due to varying sound propagation velocities caused by temperature, salt content, and pressure changes
Solution Approach 1:
The system measures temperature, salinity, and pressure parameters to determine the actual sound propagation velocity in the water column, then uses these velocity values to correct distance calculations from acoustic signals, thereby maintaining measurement precision despite varying environmental conditions
Solution Approach 2:
The system continuously monitors environmental parameters (temperature, salinity, pressure) and feeds this information back to adjust the sound velocity model, which in turn corrects ongoing distance measurements, creating a closed-loop system that compensates for environmental variations in real-time
2Measurement precision
If multiple synchronization signals are exchanged between sensor modules to account for transmission delays, then measurement precision improves, but device complexity increases due to multiple signal exchanges and delay calculations
Solution Approach 1:
The system performs preliminary measurements of one-way signal transmission times between sensor modules during an initialization phase, storing these delay values for later use in distance calculations, thereby avoiding the need for complex real-time multi-signal exchanges during actual measurement operations
Solution Approach 2:
The system measures delay times in one direction only (from reference sensor to target sensor) rather than performing bidirectional measurements, which provides sufficient precision for the application while significantly reducing the complexity of the signal exchange protocol
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
Enables precise underwater distance determination by accounting for varying acoustic conditions, allowing for optimal trawl geometry and towing speed adjustments, enhancing fishing efficiency and reducing fuel consumption.
Implementation Method 1
sending a first sensor-to-hydrophone data signal from a first sensor module of a pair of sensor modules to a hydrophone unit located at a reference point... sending a first sensor-to-hydrophone synchronization signal from the first sensor module to the hydrophone unit
Implementation Method 2
measuring a time value T22 representing a total travel time of the first inter-sensor synchronization signal from the first sensor module and second synchronization signal from the second sensor module
Data Source
AI summary
A system and corresponding method perform underwater distance determination. The system comprises a hydrophone unit (HU) located at a reference point, a first sensor module (SM), and a second SM, each located underwater. The first SM sends a first sensor-to-hydrophone data signal and a first sensor-to-hydrophone synchronization signal to the HU and sends a first inter-sensor synchronization signal to the second SM. The second SM sends, responsive to receipt of the first inter-sensor synchronization signal from the first SM, a second inter-sensor synchronization signal to the first SM. The second SM sends a second sensor-to-hydrophone data signal to the HU. The first SM measures a time value representing a total travel time of the first inter-sensor synchronization signal from the first SM and second inter-sensor synchronization signal from the second SM and calculates a distance between the first SM and second SM based on the time value measured.