Multibeam Acoustic Doppler System Using Mills Cross Arrays
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Solution Overview
Problem
Existing SONAR devices face errors in Doppler velocity measurements due to multiple sources, limiting their utility in survey and navigation tasks.
Innovation Solution
A multifan survey system utilizing a single linear projector array and a Mills Cross arrangement of transducers for transmitting and receiving acoustic signals, processing backscattered returns via autocorrelation to calculate Doppler radial velocities, enhancing accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler velocity measurements are made using conventional SONAR devices, then relative target velocities can be determined, but multiple sources of error limit measurement accuracy
Solution Approach 1:
The system segments the measurement process by using multiple pulse pairs (first and second pulse pairs) with different time delays, enabling separate autocorrelation calculations for each pulse pair. This segmentation allows multiple independent Doppler radial velocity estimates to be obtained and combined, improving measurement accuracy by reducing the impact of error sources in any single measurement.
Solution Approach 2:
The system employs a feedback mechanism where multiple Doppler radial velocity estimates from different pulse pairs are processed through autocorrelation and combined to produce a final velocity measurement. The receiver uses the backscattered return signals from multiple transmissions to iteratively refine the velocity estimate, thereby improving reliability and accuracy through cumulative information.
2Measurement precision
If multiple pulse pairs are used for Doppler measurements, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The measurement process is divided into distinct segments using multiple pulse pairs with different time delays. Each pulse pair undergoes separate autocorrelation processing, allowing the complex measurement task to be broken down into manageable, independent calculations that can be systematically combined for improved accuracy.
Solution Approach 2:
The system uses periodic transmission of pulse pairs with predetermined time delays between them. This periodic structure allows the receiver to systematically process each pulse pair through autocorrelation at regular intervals, managing computational complexity through structured, repeating measurement cycles rather than continuous complex processing.
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
Improves the accuracy and reliability of Doppler velocity measurements by simultaneously considering multiple Doppler radial velocity estimates, providing enhanced survey capabilities in bathymetry, water column monitoring, and motion stabilization.
Implementation Method 1
a transmitter for transmitting a message via the one or more projector arrays, the message for ensonifying i >= 2 fans
Implementation Method 2
echoes from the target may be used to determine relative target velocities
Implementation Method 3
plural transducers in a single hydrophone array for sensing backscattered returns
Implementation Method 4
Doppler velocimetry... Doppler estimates like Doppler velocity log ("DVL") estimates may be made... calculate for each of (i * j) beams respective Doppler radial velocity estimates DRV i,j
Implementation Method 5
the return signals processed via autocorrelation of pulse pairs to calculate for each of (i * j) beams respective Doppler radial velocity estimates DRV i,j
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A survey system including a multibeam echo sounder having a projector array and a hydrophone array in a Mills Cross arrangement uses a multi-component message to ensonify one or more fans to estimate a Doppler velocity.