Nested Free-Flooded Ring Transducers for Wideband Sonar
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Solution Overview
Problem
Current sonar transducers face challenges in achieving a wideband, compact, and high-directivity design, particularly in littoral waters with high noise levels, where conventional systems struggle to produce sound waves over a wide range of frequencies effectively.
Innovation Solution
The system employs at least two mode-balanced free-flooded ring transducers with axial gaps filled with a cylindrical body, allowing for a compact columnar array that enhances directivity and bandwidth by utilizing an 'organ pipe' mode and incorporating a columnar secondary array of tweeter transducers to extend the frequency range beyond that of a single woofer array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional sonar array is used to achieve wide bandwidth, then frequency range is improved, but array size and weight increase significantly
Solution Approach 1:
The patent implements a nested array configuration where a columnar secondary array of tweeter transducers is positioned within the axial gap of a columnar primary array of woofer transducers. This nesting allows both arrays to occupy the same spatial envelope, achieving wide bandwidth (two octaves or more) without increasing the overall array dimensions or weight. The inner tweeter array operates at higher frequencies while the outer woofer array operates at lower frequencies, with both contributing to the combined wideband output.
2Volume of moving object
If transducer size is reduced to achieve compactness, then array footprint is improved, but directivity and power output deteriorate
Solution Approach 1:
The patent combines multiple transducer elements into a unified array system where woofer transducers and tweeter transducers work together. The woofer array provides low-frequency power output while the nested tweeter array provides high-frequency directivity. The merging of these complementary functions in a compact nested configuration achieves both high power output and good directivity within a small volume, resolving the contradiction between compactness and performance.
3Volume of moving object
If transducer size is reduced to achieve compactness, then array footprint is improved, but detection range deteriorates
Solution Approach 1:
The patent employs mode-balanced free-flooded ring transducers that can dynamically operate in different vibration modes (cavity mode and radial mode) depending on the driving frequency. This dynamic behavior allows the compact transducers to achieve low-frequency operation with wavelengths much longer than the physical dimensions of the array, thereby extending detection range without increasing array size. The mode-balanced design ensures continuous operation across a wide frequency range.
4Device complexity
If a single transducer type is used to simplify design, then device complexity is reduced, but bandwidth is limited to approximately one octave
Solution Approach 1:
The patent segments the frequency spectrum by using two distinct transducer types: woofer transducers for low frequencies and tweeter transducers for high frequencies. Each segment is optimized for its specific frequency range, with the woofer array handling the lower octave and the tweeter array handling the upper octave. This segmentation allows the system to achieve a total bandwidth of two octaves or more while keeping each individual transducer design relatively simple and well-optimized for its operating range.
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 configuration results in a compact, high-power sonar system capable of producing sound waves over a wide range of frequencies, improving detection range, target resolution, and reducing interference, making it suitable for Wideband Active Sonar applications.
Implementation Method 1
Free-flooded ring transducers typically comprise segments 102 of a piezoelectric ceramic, arranged in a ring such that an electrical current applied to the ring can cause it to change size and so generate sound waves
Implementation Method 2
In a cavity mode, the FFR transducer 100 vibrates slowly enough that water is drawn in and out of the cavity in the middle of the ring. It is the drawing in and pushing out of the water that creates the sonar transmission in an FFR transducer operating in cavity mode
Implementation Method 3
In a radial mode, the FFR transducer vibrates such that sound waves are transmitted primarily from the outer surface of the cylinder
Data Source
Figure 1~2
Figure 3
Figure 4a
AI summary
A system for producing sound waves in a medium, the system comprising: at least two first free-flooded ring transducers (100) centred about a first axis, the first free-flooded ring transducers (100) being substantially cylindrical and having an axial gap of height g therebetween such that they form a first column; and at least one cylindrical body (500a, 500b) centred about the first axis nested in the first column, such that the cylindrical body is aligned with the axial gap. The cylindrical body may be a tweeter free-flooded ring transducer. This provides for improved wideband performance in a free flooded ring array.