Compact Piezo-Ceramic Sound Source for AUVs
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Solution Overview
Problem
Current underwater acoustic communication systems for autonomous underwater vehicles (AUVs) face challenges with large and heavy piezo-ceramic transducers, which are impractical for small AUVs, and pressure-compensated systems are unreliable and depth-limited, while existing free flooded resonators are sensitive to enclosures and not broadband.
Innovation Solution
The design incorporates a cylindrical piezo-ceramic ring transducer with a flexible sleeve and a resonant pipe forming a gap, or a spherical piezo-ceramic transducer mounted on metal rods with a resonant pipe, both of which are compact, efficient, and tunable within the 500 Hz to 1500 Hz frequency range, minimizing drag and maintaining high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If piezo-ceramic rings, spheres, and tonpilz transducers are used for underwater acoustic communication in the 500 Hz to 1500 Hz frequency range, then communication efficiency is improved, but the transducers become too large and heavy for small AUVs
Solution Approach 1:
The transducer is segmented into two functional parts: a compact piezo-ceramic element (ring, sphere, or tonpilz) and a separate resonant cavity. The piezo-ceramic element generates acoustic waves at the desired frequency, while the resonant cavity amplifies these waves through resonance, allowing the piezo-ceramic element itself to be much smaller than conventional full-size transducers while maintaining high communication efficiency.
Solution Approach 2:
The piezo-ceramic element is nested within or coupled to a resonant cavity structure. The cavity acts as an acoustic amplifier that contains and reinforces the sound waves generated by the small piezo-ceramic element, effectively multiplying its acoustic output without requiring the piezo-ceramic material itself to be large or heavy.
2Length of stationary object
If heavy piezo-ceramic transducers are used for long-range underwater communication, then communication range is improved, but they cannot be used on small AUVs
Solution Approach 1:
The transducer system is divided into a small piezo-ceramic wave generator and a resonant cavity amplifier. This segmentation allows the actual transducer component to be miniaturized to fit on small AUVs, while the resonant cavity maintains the acoustic power necessary for long-range communication (300+ kilometers).
Solution Approach 2:
The resonant cavity is designed to vibrate at specific resonant frequencies corresponding to the desired communication frequency range (500 Hz to 1500 Hz). By tuning the cavity dimensions and shape, the system achieves maximum acoustic output at these frequencies, enabling long-range communication without requiring large transducer dimensions.
3Adaptability or versatility
If pressure-compensated systems are used for depth-independent operation, then depth capability is improved, but reliability decreases and depth limitation occurs
Solution Approach 1:
The complex pressure-compensation mechanism is extracted and replaced with a simple resonant cavity design. The cavity is filled with a material (such as foam or air) that is inherently resistant to water pressure, eliminating the need for active pressure compensation systems. This extraction of the pressure management function simplifies the overall system, improving reliability while maintaining depth independence through the pressure-resistant cavity material.
4Volume of moving object
If free flooded resonators are used for compact design, then size is reduced, but sensitivity to enclosure and narrow bandwidth occur
Solution Approach 1:
Instead of using a single free-flooded resonator design, the patent employs multiple resonant cavities with different geometries, volumes, and boundary conditions. Each cavity is optimized for specific frequency ranges, and by combining multiple cavities with different resonant frequencies, the system achieves broad bandwidth coverage while maintaining compact overall size. The local quality of each cavity is optimized for its specific function, and the combination provides versatility.
Solution Approach 2:
The resonant cavity structure is designed to serve multiple functions: it acts as an acoustic amplifier, a frequency tuner, and a bandwidth extender when combined with multiple cavities. The same basic cavity geometry can be adjusted through dimension changes to achieve different resonant frequencies, making the design universally applicable across the 500 Hz to 1500 Hz range and beyond.
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
These designs provide a compact, efficient, and depth-independent mid- and low-frequency sound source for long-range underwater communication, maintaining high efficiency and reasonable frequency bandwidth with minimal impact on the AUV's drag coefficient, suitable for AUVs up to 1000 meters depth.
Implementation Method 1
a cylindrical piezo-ceramic ring transducer disposed between the front body portion and the rear body portion
Implementation Method 2
a resonant pipe mounted to the cylindrical body and surrounding the cylindrical piezo-ceramic ring transducer. The resonant pipe, disposed around the cylindrical piezo-ceramic ring transducer, may form a gap between an inner surface of the resonant pipe and the outer surface of the cylindrical piezo-ceramic ring transducer
Data Source
AI summary
An underwater sound source includes a cylindrical body having a front body portion, a rear body portion, a cylindrical piezo-ceramic ring transducer disposed therebetween, a flexible sleeve configured to cover an outer surface of the cylindrical piezo ceramic ring transducer, and a resonant pipe mounted to the cylindrical body and surrounding the cylindrical piezo-ceramic ring transducer. The resonant pipe is disposed around the cylindrical piezo-ceramic ring transducer, forming a gap between an inner surface of the resonant pipe and the outer surface of the cylindrical piezo-ceramic ring transducer.