Self-locating Multistatic Coherent Sonar for GPS-Denied Target Detection
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Solution Overview
Problem
Current multistatic active coherent sonar systems face limitations in accurately detecting and locating submerged targets due to uncertainty in the positions and velocities of drifting sonobuoys, especially in the absence of GPS signals, which affects the reliability and accuracy of target object detection.
Innovation Solution
The implementation of a multistatic active coherent sonar system that uses multiple source and receiver sonobuoys, along with stationary acoustic devices, and a control unit with programmed electronic processors to calculate the absolute or relative positions and velocities of sonobuoys without relying on GPS signals, employing techniques such as time delays, Doppler shifts, and Bayesian methods, and incorporating initial deployment positions and velocities to improve target detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS signals are used to track sonobuoy positions, then positioning accuracy is improved, but the system becomes dependent on external signals that may be unavailable in GPS-denied environments
Solution Approach 1:
The sonar system uses its own acoustic signals to determine sonobuoy positions. The sonobuoys act as both transmitters and receivers of acoustic signals, enabling them to self-localize relative to each other and to the platform without requiring external GPS signals. This mutual acoustic ranging creates a self-contained positioning system that operates independently in GPS-denied environments.
Solution Approach 2:
Acoustic signals serve as an intermediary medium to transfer position and velocity information between sonobuoys and the central platform. Instead of relying on direct satellite-to-sonobuoy communication (GPS), the system uses acoustic wave propagation through water as the mediation mechanism, converting acoustic measurements into positional data through signal processing algorithms.
2Measurement precision
If multiple sonobuoys are deployed to improve target detection accuracy, then measurement precision is improved, but uncertainty in sonobuoy positions and velocities increases without GPS
Solution Approach 1:
The system continuously exchanges acoustic signals between all sonobuoys and the platform, creating a network of mutual measurements. Each sonobuoy's position and velocity estimates are refined through feedback from multiple acoustic signal interactions, allowing the system to maintain reliable tracking of multiple drifting sonobuoys even without GPS by leveraging the collective information from the entire sonar network.
3Measurement precision
If traditional Doppler estimation techniques are used, then velocity estimation is achieved, but accuracy is limited compared to more sophisticated methods
Solution Approach 1:
The system transitions from traditional Doppler estimation to Coherent Time Change Estimation (CTCE), which fundamentally changes the parameter being measured from frequency shift to time delay variation. This parameter change enables more accurate velocity estimation by directly measuring the rate of change of signal travel time, capturing second-order effects that traditional Doppler methods miss, while the increased complexity is managed through programmed electronic processors.
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 enables earlier detection of target objects and more accurate estimation of their positions and velocities, even in GPS-denied environments, by reducing errors in sonobuoy positioning and improving the overall accuracy of target localization.
Implementation Method 1
acoustic signals are emitted by an acoustic source device to propagate underwater
Implementation Method 2
reflect or scatter from various underwater objects or bathymetric features
Implementation Method 3
reflect or scatter from various underwater objects or bathymetric features
Implementation Method 4
Position and velocity of a submerged object can be estimated from intensity, timing, phase, Doppler shift, directionality, or other properties of the acoustic signals
Implementation Method 5
Position and velocity of a submerged object can be estimated from intensity, timing, phase, Doppler shift, directionality, or other properties of the acoustic signals
Data Source
AI summary
Multistatic active coherent sonar systems and methods include reception by floating receiver sonobuoys of acoustic signals emitted by floating source sonobuoys, by both direct propagation from the source sonobuoys and reflection or scattering from a target object. Subsequent calculations based at least in part on those signals can be employed to estimate relative or absolute positions or velocities of the target object and the source and receiver sonobuoys. The estimated relative velocities and positions can be calculated without relying on GPS or other extrinsic positioning signals acquired for each sonobuoy after its deployment. Acoustic signals emitted by a stationary source on the seabed, received by a stationary receiver on the seabed, or reflected/scattered from a bathymetric feature, can be employed to estimate absolute or relative positions or velocities of the target object and the source and receiver sonobuoys.