Towed Hydrophone Array for Underwater Beacon Location
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Solution Overview
Problem
Current methods for detecting and locating underwater location beacons (ULBs) are limited by their detection range, require costly modifications to aircraft and beacons, and lack precision in estimating the beacon's location, especially in varying water depths.
Innovation Solution
A system utilizing a towed underwater body equipped with a linear sensor array of hydrophones that processes acoustic signals to provide a precise estimate of the ULB's location using a Figure of Merit equation and beamforming techniques, increasing the detection range and directivity index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-correlation calculation is used to estimate distance to acoustic beacon, then location estimate is improved relative to single hydrophone, but no signal gain or greater detection range is achieved
Solution Approach 1:
The detection system is segmented into multiple spatially distributed hydrophones arranged in an array configuration. This segmentation allows the system to process acoustic signals from multiple spatial locations simultaneously, enabling both precise location estimation through cross-correlation and enhanced detection range through array signal processing techniques.
Solution Approach 2:
The system transitions from single-point detection to spatial distribution by arranging hydrophones in a two-dimensional array pattern. This dimensional expansion enables the system to exploit spatial information for both location estimation accuracy and detection range extension through beamforming and spatial filtering.
2Area of stationary object
If spread spectrum acoustic waveform is transmitted by ULB, then detection range is increased, but costly replacement of all underwater beacons in commercial aircraft is required
Solution Approach 1:
The patent introduces an intermediary detection system (the multi-hydrophone array with cross-correlation processing) that can work with existing ULB transmitters. Rather than modifying the beacons themselves, the system uses the array geometry and signal processing as the intermediary mechanism to achieve extended detection range with standard beacons.
Solution Approach 2:
The patent replaces the need for mechanical/modification changes to the beacon hardware with a signal processing solution. Instead of physically modifying beacons to use spread spectrum waveforms, the system uses cross-correlation processing of received signals to achieve similar detection range improvements with existing beacon technology.
3Reliability
If beacon is physically relocated and tethered to ascend from seafloor, then probability of locating downed aircraft is improved, but expensive modifications to beacon and aircraft are required
Solution Approach 1:
The patent creates a virtual copy of the beacon location information through signal processing. Instead of physically moving the beacon or modifying its deployment mechanism, the system processes acoustic signals to create a precise location estimate that replicates the information a relocated beacon would provide, but without the physical modifications.
4Ease of operation
If acoustic data link is used to transmit data upon command, then data recovery is facilitated by eliminating physical access requirement, but no advantage is provided for detecting and locating aircraft data recorder
Solution Approach 1:
The patent performs preliminary location estimation using cross-correlation processing of acoustic signals received by the hydrophone array. This preliminary action of determining beacon location occurs before any data recovery operations, enabling precise localization without requiring physical access to the aircraft debris field.
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
The system effectively doubles the detection range and area coverage of ULB signals, allowing for precise location estimation and rapid search operations across varying water depths without the need for costly modifications.
Implementation Method 1
a plurality of hydrophones to detect an acoustic signal transmitted by the ULB
Data Source
AI summary
A method using a tow body and sensor array for locating an underwater location beacon is provided. The steps of the method are moving the body and array in a direction of motion; orientating the array orthogonal to the direction of motion; beamforming acoustic conical beams from the array onto a seafloor; detecting a time series of acoustic data channels from the beacon; converting the data channels into spatial beams of acoustic frequency; determining if a signal of the underwater location beacon is present from each spatial beam; calculating likelihood functions for locations of the beacon to represent an area of the seafloor from which the signal of the underwater location beacon is to have originated; accumulating likelihood functions for the location of the underwater location beacon over the course of a search pattern; and producing a grid for a beacon location based on the likelihood functions.