Underwater Positioning Using Region-Specific Time Windows
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Solution Overview
Problem
Existing underwater positioning systems face challenges in accurately determining the position of an acoustic transmitter or hydrophone due to interference from reflected and diffracted sound waves, which complicates the calculation of direct wave arrival times and leads to positioning errors.
Innovation Solution
An underwater positioning system that employs a database to store time windows for sound wave propagation in predefined regions, using a coordinate estimation unit to calculate a time window-applied impulse response and maximize energy to accurately determine the location of an unknown point by excluding unintended sound waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If individual impulse response calculation is used to estimate coordinates, then calculation simplicity is maintained, but positioning accuracy deteriorates due to interference from reflected and diffracted waves
Solution Approach 1:
The patent divides the underwater positioning range into multiple regions and creates separate time windows for each region. This segmentation allows the system to isolate and process direct waves from different spatial zones independently, preventing interference from reflected and diffracted waves in other regions. The coordinate estimation is performed by comparing impulse responses across segmented regions to identify the region with maximum energy, thereby improving positioning accuracy while maintaining manageable calculation complexity.
Solution Approach 2:
The patent extracts the direct wave component from the composite impulse response by applying region-specific time windows. Each time window is designed to capture only the direct wave arrival time for its corresponding region, effectively extracting the useful signal while excluding reflected and diffracted waves. This extraction process resolves the contradiction by isolating the direct wave information needed for accurate positioning without requiring complex interference cancellation methods.
2Measurement precision
If time window filtering is applied to exclude unintended sound waves, then positioning accuracy improves, but calculation complexity increases
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing time windows for each region in a database before actual positioning operations. These time windows are computed based on expected direct wave arrival times for various regions, allowing the system to quickly apply pre-prepared filtering during runtime. This preliminary preparation reduces real-time calculation complexity while maintaining the ability to accurately filter out reflected and diffracted waves, thus resolving the contradiction between positioning accuracy and calculation complexity.
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 allows for precise determination of the underwater position of acoustic transmitters or hydrophones by isolating the direct wave component and comparing energies across regions, reducing positioning errors.
Implementation Method 1
a sound wave emitted from the acoustic transmitter to reach the hydrophone
Implementation Method 2
a sound wave reflected by a water surface, a water bottom, or a structure (reflected wave)
Implementation Method 3
a sound wave diffracted by a water bottom or a structure (diffracted wave)
Data Source
AI summary
An underwater positioning system for accurate underwater positioning. At least one among at least one acoustic transmitter and at least one hydrophone is provided at known coordinates and which positions an unknown point having unknown coordinates at which another acoustic transmitter or hydrophone is provided, includes a time window that stores in advance, when the unknown point is set in a plurality of regions set by dividing an underwater positioning range, a time window for a sound wave emitted from the acoustic transmitter to reach the hydrophone for each of the regions, and a coordinate estimation and specification unit that calculates for each of the regions a time window-applied impulse response as an inner product of the time window and an impulse response of a sound wave propagation path from the acoustic transmitter to the hydrophone and estimates that the unknown point is located in the region where the energy of the time window-applied impulse response is maximized.