Interest in underwater transducers has persisted since the mid-1900s. Underwater transducers are designed in various shapes using various materials depending on the purpose of use, such as to achieve high power, improve broadband, and enhance beam steering. Therefore, in this study, an analysis is conducted according to the structural shape of the transducer, exterior material, and active material. By classifying transducers by structure, the transducer design trends and possible design issues can be identified. Researchers have constantly attempted new methods to improve the performance of transducers. In addition, a methodology to overcome this problem is presented. Finally, this review covers old and new research, and will serve as a reference for designers of underwater transducer.

https://www.mdpi.com/1424-8220/23/4/1821/pdf?version=1675680238

Design of Piezoelectric Acoustic Transducers for Underwater Applications

High-power giant magnetostrictive transducers are widely used in underwater acoustics. Because of the low magnetic permeability of giant magnetostrictive materials (GMMs) and permanent magnets (PMs), there must exist significant magnetic flux leakage. For establishing the equivalent model of high-power giant magnetostrictive transducers, it is of great necessity to accurately obtain an accurate magnetic spatial distribution and couple it to the mechanical domain. In this way, it can reflect the difference in the magnetic field of each giant magnetostrictive rod (GMR). However, most existing models for giant magnetostrictive transducers rarely consider the spatial distribution of the magnetic field and its coupling effect on the mechanical domain. The multi-degree-of-freedom (multi-DOF) lumped-parameter model (LPM) has been widely used due to its ability to reflect the motion of each degree of freedom in a vibration system and flexibility for multifield simulation. This study proposes a multi-DOF LPM of the high-power giant magnetostrictive transducer, which considers the magnetic flux leakage on both GMRs and PMs. To verify the effectiveness of the proposed technique, the variations of the magnetic flux on GMR before and after considering the flux leakage were compared. Moreover, a comparative analysis with the magnetomechanical coupling in the state-of- the-art plane wave model (PWM) is carried out, which verifies the superiority of our proposed model. Finally, the proposed model is used to simulate the impedance of the transducer, as well as the maximum transmitting current response (TCR), showing excellent agreement with the experimental results.

Multi-DOF Lumped-Parameter Modeling of High-Power Giant Magnetostrictive Transducer Coupled With Spatial Distribution of Magnetic Field

High-power giant magnetostrictive transducers are widely used in underwater acoustics. Because of the low magnetic permeability of giant magnetostrictive materials (GMMs) and permanent magnets (PMs), there must exist significant magnetic flux leakage. For establishing the equivalent model of high-power giant magnetostrictive transducers, it is of great necessity to accurately obtain an accurate magnetic spatial distribution and couple it to the mechanical domain. In this way, it can reflect the difference in the magnetic field of each giant magnetostrictive rod (GMR). However, most existing models for giant magnetostrictive transducers rarely consider the spatial distribution of the magnetic field and its coupling effect on the mechanical domain. The multi-degree-of-freedom (multi-DOF) lumped-parameter model (LPM) has been widely used due to its ability to reflect the motion of each degree of freedom in a vibration system and flexibility for multifield simulation. This study proposes a multi-DOF LPM of the high-power giant magnetostrictive transducer, which considers the magnetic flux leakage on both GMRs and PMs. To verify the effectiveness of the proposed technique, the variations of the magnetic flux on GMR before and after considering the flux leakage were compared. Moreover, a comparative analysis with the magnetomechanical coupling in the state-of- the-art plane wave model (PWM) is carried out, which verifies the superiority of our proposed model. Finally, the proposed model is used to simulate the impedance of the transducer, as well as the maximum transmitting current response (TCR), showing excellent agreement with the experimental results. 

The active sound navigation and ranging (SONAR) transmission system emits acoustic pulses underwater using a wave generator, a SONAR power amplifier (SPA), and a projector. The acoustic pulse travel in the direction of the target and return as an echo to a hydrophone to learn the range or speed of the object. Often the same device is used as a hydrophone and a projector; in this context, it is known as a transducer. In order to obtain a maximum range of detection in the SONAR, it is desirable to generate the maximum amount of acoustic power until the point in which the echo can be detectable in an atmosphere with non-wished noise. Therefore, a high value of source level (SL) is required that depends largely on the value of electrical power applied to the transducer (Pe). However, when trying to obtain the maximum range of detection in the SONAR system there are the following three peculiar limitations that affect performance: The cavitation, the reverberation, and the effect of interaction in the near field. In this paper, an experimental measurement methodology is presented to detect the cavitation effects in a tonpilz-type transducer for an active SONAR transmission system using a transducer as a projector and a calibrated hydrophone in a hydroacoustic tank by measuring the parameters of total harmonic distortion of the fundamental waveform (THD-F) of the generated acoustic pulse, transmitting voltage response (TVR) to characterize the system and sound pressure level (SPL) that indicates the intensity of sound at a given distance. Whereas the reverberation and the interaction effect in the near field are objects of other study cases. A 570.21 W and THD-F < 5% switched-mode power amplifier (SMPA) prototype was developed to excite the electroacoustic transducer employing a full-bridge inverter (FBI) topology and a digital controller using a field-programmable gate array (FPGA) for unipolar sine pulse width modulation (SPWM) to generate a continuous wave (CW) acoustic pulse at a frequency 11.6 kHz. The results obtained show that from the level of Pe=196.05 W with the transducer at 1 m of depth, the value of THD-F increases significantly while the behavior of the TVR and SPL parameters is affected since it is not as expected and is attributed when cavitation occurs.

/pdf/cavitation-detection-in-a-tonpilz-type-transducer-for-active-gf55coi5.pdf

Cavitation Detection in a Tonpilz-Type Transducer for Active SONAR Transmission System

Stretchable sound-in-displays, which can generate synchronous sound and light directly from the display without a separate speaker, allow immersive audio and visual perception even on curved surfaces. In stretchable sound-in-displays, alternating current electroluminescent (ACEL) devices have been used as light-emitting sources owing to their high brightness and stability. However, stretchable ACEL devices that use low dielectric constant (κ) materials require a high operating voltage for generating light and sound. Herein, we demonstrate a stretchable ACEL loudspeaker with a low operating voltage using stretchable high-κ dielectrics and strain-insensitive electrodes. Our device exhibits 87.7 cd/m2 of luminance and 79.70 dB of sound pressure level at an operating voltage of 120 V and 10 kHz. As the next platform of wearable devices, the suggested ACEL loudspeaker exhibits high-quality synchronous light and sound generation performance even under various types of mechanical deformation, such as finger flexion and wrist bending.

Low-Voltage Stretchable Electroluminescent Loudspeakers with Synchronous Sound and Light Generation.

The loss effect in smart materials, the active part of a transducer, is of significant importance to acoustic transducer designers, as it directly affects the important characteristics of the transducer, such as the impedance spectra, frequency response, and the amount of heat generated. It is therefore beneficial to be able to incorporate energy losses in the design phase. For high-power low-frequency transducers requiring more smart materials, losses become even more appreciable. In this paper, similar to piezoelectric materials, three losses in Terfenol-D are considered by introducing complex quantities, representing the elastic loss, piezomagnetic loss, and magnetic loss. The frequency-dependent eddy current loss is also considered and incorporated into the complex permeability of giant magnetostrictive materials. These complex material parameters are then successfully applied to improve the popular plane-wave method (PWM) circuit model and finite element method (FEM) model. To verify the accuracy and effectiveness of the proposed methods, a high-power Tonpilz Terfenol-D transducer with a resonance frequency of around 1 kHz and a maximum transmitting current response (TCR) of 187 dB/1A/μPa is manufactured and tested. The good agreement between the simulation and experimental results validates the improved PWM circuit model and FEA model, which may shed light on the more predictable design of high-power giant magnetostrictive transducers in the future.

/pdf/modeling-of-high-power-tonpilz-terfenol-d-transducer-using-3hw0ib57.pdf

Modeling of High-Power Tonpilz Terfenol-D Transducer Using Complex Material Parameters

The properties of giant magnetostrictive material (GMM) are very sensitive to external compressive stress. Knowledge of these key properties is of essential importance in practical applications such as high-power underwater transducers. Although the parameters of GMM have been extensively studied, characterization and analysis of magnetic, elastic, and piezoelectric losses under different compressive stresses are rarely reported due to the difficulty in experimentally realizing the ideal mechanical free or clamped boundary conditions. In this study, we designed a longitudinal transducer for complex parameters characterization of GMM. We successfully characterize the key three losses in GMM using a multi-degree-of-freedom (MDOF) lumped parameter equivalent circuit model (LECM), meticulously incorporating the surface contact damping, stiffness, and structural losses. MDOF LECM provides a novel idea for loss characterization of GMM under compressive stress. In contrast to prior-art parameters characterization based on the distributed parameter equivalent circuit model (DECM), the proposed characterization based on MDOF LECM shows apparent superiority in terms of global sensitivity. The intensive losses of GMM for ten-time characterizations show high stability and are all positive. Statistical analysis of intensive losses’ dependency on the compressive stress is performed. A longitudinal transducer is designed for experimental verification. Finally, 95% prediction and confidence intervals for the variation trend of the intensive losses in relationship with compressive stress are obtained.

/pdf/loss-characterization-of-giant-magnetostrictive-material-3n6hcnvd.pdf

Loss Characterization of Giant Magnetostrictive Material Under Compressive Stress

The statistical theory of magnetic losses provides a simple and general method for the interpretation and prediction of losses in various magnetic materials. However, there are difficulties in assessing the losses since it would require additional experimental data and is seldom available to device designers. In this article, based on the modified dynamic Jiles–Atherton (JA) model by parameters scaling, a parameter extraction process by three successive steps is proposed for identifying 11 effective parameters applicable to different sinusoidal excitation magnetic fields. It provides a promising solution for the prediction of magnetic losses in giant magnetostrictive material (GMM). First, a quasi-static saturation <inline-formula> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> curve is used to obtain five saturation parameters. Four optimization coefficients are then determined using the arbitrary quasi-static minor <inline-formula> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> curve. Finally, on the basis of the nine parameters determined in the former two steps, two dynamic factors are determined using an arbitrary dynamic minor <inline-formula> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> curve. Then, all 11 coefficients were obtained, which could be used to reliably simulate the hysteresis loop of GMM under different sinusoidal excitation magnetic fields and realize the prediction of magnetic loss. The simulation results of the proposed model are in good agreement with the experimental results, which confirm its validity and accuracy. The proposed parameter extraction process can remarkably reduce the required experiment tests, and only three sets of experimental curves are needed to achieve a fast and accurate prediction of GMM magnetic losses.

Yanfei Wei

Papers

Modeling of High-Power Tonpilz Terfenol-D Transducer Using Complex Material Parameters

Loss Characterization of Giant Magnetostrictive Material Under Compressive Stress

Prediction of Magnetic Losses in Giant Magnetostrictive Materials Under Different Sinusoidal Excitation Magnetic Fields