MEMS Vector Hydrophone Research Articles

Embedded UUV conformal MEMS vector hydrophone

As the core equipment of Underwater acoustic detection, MEMS vector hydrophones are applied to Unmanned Underwater Vehicles (UUV), which can better detect underwater targets. Most of the MEMS vector hydrophones currently used are long-tube cylindrical, relatively large in volume and weight, which is not suitable for installation on UUV. The co-vibration vector hydrophone is small in size and weight, but it needs elastic suspension due to the requirements of the working principle. Therefore, according to the needs of practical engineering applications, this paper designs an Embedded UUV Conformal MEMS Vector Hydrophone (ECVH), establishes an encapsulation model through theoretical analysis, and uses COMSOL6.0 to simulate its acoustic performance. The sensitivity and directionality of the ECVH are verified in the standing wave barrel. When the test frequency is 630 Hz, the sensitivity of the vector channel is −182.3 dB, and the depth of the ' 8 ' direction concave point is greater than 35 dB. The sensitivity of the sound pressure channel is −182 dB, which is omnidirectional. Finally, it is mounted on UUV for preliminary signal acquisition verification test. The test results show that the ECVH can work normally on UUV, which provides a new idea for underwater small platform test.

An acoustic pressure-gradient MEMS vector hydrophone system based on piezoelectric micromachined ultrasonic transducer array

This article presents an acoustic pressure-gradient MEMS vector hydrophone system, which consists of a 2 × 2 piezoelectric scalar hydrophone array and a microcontroller unit (MCU)-based signal-conditioning circuit. The reported scalar hydrophone is fabricated based on a scandium-doped aluminum nitride (Sc0.2Al0.8N) piezoelectric micromachined ultrasonic transducer (PMUT) array. Four identical scalar hydrophones are adopted and arranged in a 2 × 2 array for detecting the acoustic pressure gradient along different incident angles. The received electrical signals in each scalar hydrophone are collected and processed by the MCU directly. Experimental results show that the vector hydrophone system has a receive sensitivity of −168 dB (re: 1 V/μPa) in the omnidirectional receive mode, and a receive sensitivity of −198 dB (re: 1 V/μPa) at 10 kHz in the dipole receive mode, respectively. With the aid of an advanced data preprocessing approach, the reported vector hydrophone system achieves the direction-of-arrival (DOA) estimations of underwater acoustic signals with an error of less than 2°. The measurement results show that the reported MEMS vector hydrophone system has the potential for the detection of underwater sound sources.

Design and Implementation of a Four-Unit Array Piezoelectric Bionic MEMS Vector Hydrophone.

High-performance vector hydrophones have been gaining attention for underwater target-monitoring applications. Nevertheless, there exists the mutual constraint between sensitivity and bandwidth of a single hydrophone. To solve this problem, a four-unit array piezoelectric bionic MEMS vector hydrophone (FPVH) was developed in this paper, which has a cross-beam and a bionic fish-lateral-line-nerve-cell-cilia unit array structure. Simulation analysis and optimization in the design of the bionic microstructure have been performed by COMSOL 6.1 software to determine the structure dimensions and the lead zirconate titanate (PZT) thin film distribution. The FPVH was manufactured using MEMS technology and tested in a standing wave bucket. The results indicate that the FPVH has a sensitivity of up to -167.93 dB@1000 Hz (0 dB = 1 V/μPa), which is 12 dB higher than that of the one-unit piezoelectric MEMS vector hydrophone (OPVH). Additionally, the working bandwidth of the FPVH reaches 20 Hz~1200 Hz, exhibiting a good cosine curve with an 8-shape. This work paves a new way for the development of multi-unit piezoelectric vector hydrophones for underwater acoustic detectors.

Design and Algorithm Integration of High-Precision Adaptive Underwater Detection System Based on MEMS Vector Hydrophone.

Real-time DOA (direction of arrival) estimation of surface or underwater targets is of great significance to the research of marine environment and national security protection. When conducting real-time DOA estimation of underwater targets, it can be difficult to extract the prior characteristics of noise due to the complexity and variability of the marine environment. Therefore, the accuracy of target orientation in the absence of a known noise is significantly reduced, thereby presenting an additional challenge for the DOA estimation of the marine targets in real-time. Aiming at the problem of real-time DOA estimation of acoustic targets in complex environments, this paper applies the MEMS vector hydrophone with a small size and high sensitivity to sense the conditions of the ocean environment and change the structural parameters in the adaptive adjustments system itself to obtain the desired target signal, proposes a signal processing method when the prior characteristics of noise are unknown. Theoretical analysis and experimental verification show that the method can achieve accurate real-time DOA estimation of the target, achieve an error within 3.1° under the SNR (signal-to-noise ratio) of the X channel of -17 dB, and maintain a stable value when the SNR continues to decrease. The results show that this method has a very broad application prospect in the field of ocean monitoring.

A directional algorithm from single MEMS vector hydrophone based on polynomial fitting and real-time attitude compensation

In order to solve the problem of noise interference and attitude shift of vector hydrophone due to the influence of natural factors during underwater detection, it is necessary to develop a new method to solve the problem. In this paper designs an orientation algorithm of single MEMS vector hydrophone based on polynomial fitting and real-time attitude compensation. It is proved that the algorithm will not change the stability of the system, and the time complexity is low. In order to verify the effect of this algorithm, this paper compares this algorithm with other signal denoising methods and attitude correction methods, and proves that this algorithm has smaller processing error. Finally, the underwater acoustic signal actually collected in the lake is used as the input signal to calculate, and the orientation error is less than 1, which verifies the feasibility and practicability of the algorithm.

Design and Fabrication of Hollow Mushroom-Like Cilia MEMS Vector Hydrophone

Vector hydrophone is the core equipment of underwater acoustic detection. Aiming at the problem of low sensitivity and short detection distance of existing vector hydrophone. In this paper, a hollow mushroom-like cilia sensitive structure is designed to optimize the hydrophone sensitive unit. The optimal size of the hollow mushroom-like cilia MEMS vector hydrophone (MCVH) microstructure was determined by COMSOL5.6 simulation. The hollow structure is adopted, which not only ensures the working bandwidth of the hydrophone is 20Hz-1000Hz, but also improves the sensitivity of the hydrophone by increasing the receiving area of the sound wave. The test results show that the hollow structure has obvious "8" directivity, and the pit depth of the "8" directivity larger than 40dB at 315Hz. Meantime, the sensitivity of MCVH can reach -180.9dB at 1000Hz. Compared with Ciliary MEMS vector hydrophone(CVH), the sensitivity is improved by 16.8dB.

Signal Denoising of MEMS Vector Hydrophone Based on Optimized VMD, Compressed Sensing, and Wavelet Threshold

With the noise in underwater acoustic signal extracted from ocean background, the denoising algorithm based on the Variational Mode Decomposition (VMD) optimized by improved Grasshopper Optimization Algorithm (IGOA), the compressed sensing (CS) and wavelet threshold (WT) is proposed in this paper, named by IGOA-VMD-CS-WT, where VMD optimized by IGOA is utilized to perform sign composition and the obtained Intrinsic Mode Functions (IMF) are divided into effective components and noise components using cross-correlation coefficient of each IMF. CS is performed on sparse representation of noise components and the obtained sparse coefficients are processed with WT for the filters. The effective components and the denoised components are reconstructed to the denoised signal by the Orthogonal Matching Pursuit. The experiments show that IGOA-VMD-CS-WT has the highest signal-to-noise ratios and the least root mean square errors under different noise levels and has the better denoising effect on the denoising of the actual data.

A ScAlN Piezoelectric High-Frequency Acoustic Pressure-Gradient MEMS Vector Hydrophone With Large Bandwidth

In this letter, a scandium-doped aluminum nitride (Sc <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {Al}}_{1-x}\text{N}$ </tex-math></inline-formula> , x = 9.5%) piezoelectric high-frequency MEMS vector hydrophone with large operation bandwidth is presented, which measures acoustic pressure gradient underwater. The hydrophone sensor consists of four groups of sensing cell arrays. Each sensing cell is composed of a hexagonal sensing diaphragm made up of a piezoelectric stack of ScAlN piezoelectric thin-film sandwiched by Mo and highly doped single-crystal silicon, with a top and a bottom oxide film surrounding the piezoelectric stack. The hydrophone sensor can operate in not only omnidirectional receive mode, but also dipole receive mode, depending on the signal processing algorithm used for the four array groups. The vector hydrophone operates in the frequency range of 20 kHz to 160 kHz, which is specially designed to monitor the dolphin calls. The measured maximum receive sensitivity is -175 dB (re: 1 V/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Pa) in the dipole receive mode at 160 kHz and −169±2 dB (re: 1 V/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Pa) in the omnidirectional receive mode in the operation bandwidth, respectively. The reported vector hydrophone also presents a smooth directivity pattern at 100 kHz. The experiments show the reported MEMS vector hydrophone has good potential in conservation of dolphins and other underwater detection at high frequency between 20 kHz to 160 kHz.

Design and analysis of monolithic integrated MEMS vector hydrophone micro-array

Based on the high sensitivity and miniaturization advantages of MEMS vector hydrophone, we proposed and designed a monolithic integrated micro-array vector hydrophone composed of multiple sensor units. The theoretical model shows that the micro-array can improve the structural sensitivity and output signal-to-noise ratio while eliminating the problem of port and starboard ambiguity. Meanwhile, the micro-array structure clearly reduces the installation error of conventional vector array and improve the directional accuracy. Taking 5-element micro-array as an example, the resonance frequency in wet mode reaches 956 Hz that meets the requirement of test frequency band. Through theoretical and computational analysis, the sensitivity of micro-array is increased 14 dB and the SNR is increased 3.1 dB compared with that of the single vector hydrophone. The standing-wave tube experiment verified the directional effect of vector micro-array. The research of vector hydrophone micro-array is helpful to the application of underwater acoustic engineering.

Research on Direction of Arrival Estimation Based on Self-Contained MEMS Vector Hydrophone.

A self-contained MEMS vector hydrophone with a scalar–vector integrated design is proposed in this paper. Compared with traditional MEMS vector hydrophones, this design solves the problem of ambiguity in the port and starboard during orientation, and also realizes the self-contained storage of acoustic signals. First, the sensor principle and structural design of the self-contained MEMS hydrophone are introduced, and then the principle of the combined beamforming algorithm is given. In addition to this, the amplitude and phase calibration method based on the self-contained MEMS vector hydrophone is proposed. Then, the sensitivity and phase calibrations of the sensor are carried out in the standing wave tube. The sensitivity of the vector channel is −182.7 dB (0 dB@1 V/Pa) and the sensitivity of the scalar channel is −181.8 dB (0 dB@1 V/Pa). Finally, an outdoor water experiment was carried out. The experimental results show that the self-contained MEMS vector hydrophone can accurately pick up and record underwater acoustics information. It realizes the precise orientation of the target by combining beamforming algorithms. The direction of arrival (DOA) error is within 5° under the outdoor experimental conditions with an SNR of 13.67 dB.

Research on Doa Estimation Method of Single Mems Vector Hydrophone Based on Pulse Signal

Research on Doa Estimation Method of Single Mems Vector Hydrophone Based on Pulse Signal

Research on Doa Estimation Method of Single Memsvector Hydrophone Based on Pulse Signal

Research on Doa Estimation Method of Single Memsvector Hydrophone Based on Pulse Signal

Research on the influence of hydrostatic pressure on the sensitivity of bionic cilia MEMS vector hydrophone

Hydrophones are one of the main sensors for underwater acoustic signal detection, and their positioning accuracy is closely related to their sensitivity. However, in practice, hydrophones need to work in different depths of water environment. The ciliated MEMS vector hydrophone has a four-beam structure and has a certain anti-interference ability against hydrostatic pressure. However, due to the manufacturing process and other reasons, there may be certain errors in the production of varistors, which leads to the hydrophone's resistance to hydrostatic pressure. The resistance to the impact is reduced. Therefore, studying the influence of hydrostatic pressure environment on the sensitivity of MEMS vector hydrophones is of great significance to the application of MEMS vector hydrophones. According to the application environment of MEMS vector hydrophone, the sensitivity of MEMS vector hydrophone is studied in this paper within the range of hydrostatic pressure 1 atm ∼ 12 MPa. In this paper, the influence of hydrostatic pressure on the sound transmission loss and piezoresistor are studied to theoretically verify that the hydrostatic pressure has little effect on the sensitivity of MEMS vector hydrophone. It is verified by COMSOL5.6 software simulation that the sensitivity changes within the pressure range of 1 dB. In order to facilitate the experiment of the MEMS vector hydrophone in the hydrostatic environment, this paper proposed a method of combining an external sound source with a marine environment simulation test machine. It is concluded that within the test pressure range, the sensitivity change of the MEMS vector hydrophone fluctuates within ±1 dB.

Design and Simulation of Flexible Underwater Acoustic Sensor Based on 3D Buckling Structure.

The exploration of marine resources has become an essential part of the development of marine strategies of various countries. MEMS vector hydrophone has great application value in the exploration of marine resources. However, existing MEMS vector hydrophones have a narrow frequency bandwidth and are based on rigid substrates, which are not easy to be bent in the array of underwater robots. This paper introduces a new type of flexible buckling crossbeam–cilium flexible MEMS vector hydrophone, arranged on a curved surface by a flexible substrate. A hydrophone model in the fluid domain was established by COMSOL Multiphysics software. A flexible hydrophone with a bandwidth of 20~4992 Hz, a sensitivity of −193.7 dB, excellent “8” character directivity, and a depth of concave point of 41.5 dB was obtained through structured data optimization. This study plays a guiding role in the manufacture and application of flexible hydrophones and sheds light on a new way of marine exploration.

Design of ciliated MEMS vector hydrophone based on stainless steel mesh cap

The polyurethane-encapsulated lateral line-inspired MEMS vector hydrophone has problems such as low-frequency sensitivity (10–80 Hz) loss and narrow working bandwidth. In order to eliminate these two problems, a new encapsulation with a stainless steel mesh cap structure was proposed. This paper first verified the sensitivity loss and narrow working bandwidth of the polyurethane encapsulation through experiments and simulations, analyzed the impact of the perforation rate, thickness, and aperture of the stainless steel mesh cap structure on the vector hydrophone through simulation, and finally made 8 types of stainless steel mesh cap with different apertures was tested experimentally. Finally, the experimental results show that the sensitivity of the stainless steel mesh encapsulation in the low frequency range (10–80 Hz) is improved by an average of 12 dB than that of the polyurethane encapsulation, and the working bandwidth has been increased from 10–210 Hz to 10–667 Hz.

High-sensitivity lollipop-shaped cilia sensor for ocean turbulence measurement

A lollipop-shaped cilia sensor based on the MEMS vector hydrophone was designed for measuring ocean turbulence. The micro-cross beam structure met successfully detected the ocean turbulence vector. In addition, the cilia were designed in a lollipop shape, which not only increased the turbulence signal receiving area but also achieved better diversion effects. In general, the turbulence signal is usually concentrated in the range 0–200 Hz. The sensor structure was simulated and analyzed and its size was optimized. The frequency response bandwidth was also ensured, leading to improved sensitivity. The results of sensor calibration experiments prove that the lollipop-type cilia sensor has high sensitivity, reaching 2.73×10−2 Vms2/kg. In addition, the vector test results verify that the MEMS turbulence sensor accurately measured the two-dimensional ocean turbulence.

Design and Implementation of a Composite Hydrophone of Sound Pressure and Sound Pressure Gradient.

The bionic cilium MEMS vector hydrophone has the characteristics of low power consumption, small volume, and good low-frequency response. Nevertheless, there exists the problem of left–right ambiguity in the azimuth estimation of a single hydrophone. In order to solve the engineering application problem, a sound-pressure sound-pressure-gradient hydrophone is designed in this paper. The new composite hydrophone consists of two channels. The bionic cilium microstructure is optimized and used as the vector channel, to collect the sound pressure gradient information, and a scalar channel, based on a piezoelectric ceramic tube, is added, to receive the sound pressure information. The theoretical analysis, simulation analysis, and test analysis of the composite hydrophone are carried out, respectively. The test results show that the sensitivities of the hydrophone can reach up to −188 dB (vector channel) and −204 dB (scalar channel). The problem of left–right ambiguity is solved by combining the sound pressure and sound pressure gradient in different ways. This is of great significance in the engineering application of single cilium MEMS hydrophone orientation.

Design and realization of cap-shaped cilia MEMS vector hydrophone

Ciliary MEMS vector hydrophone (CVH) has excellent performance in low-frequency detection, however, there is still the problem of poor sensitivity in some applications. A cap-shaped ciliary vector hydrophone (CCVH) is proposed in this paper. The microstructure not only ensures the working bandwidth of the hydrophone, but also increases the sensitivity. A single integration process is adopted to complete the pasting of the cap-shaped cilia and the cantilever beam, requiring no complicated secondary cilia integration process. Firstly, a mathematical model is established for theoretical derivation, and then the principle is verified via COMSOL simulation. Finally, test results show that the sensitivity of CCVH can reach −182.7 dB at 1 kHz (1 kHz, 0 dB@1 V/µPa). Compared with the CVH, the sensitivity has increased by 14.4 dB. Concave point depth of 8-shaped directivity is beyond 30 dB, which indicates that CCVH has an excellent ability to detect underwater ship noise.

Design and implementation of beaded cilia MEMS vector hydrophone

In view of the problem that the increased difficulty of underwater moving targets detection caused by the development of acoustic stealth technology, a beaded cilia MEMS vector hydrophone (BCVH) is proposed in this paper. Compared with previous cilia structures, it can enlarge the receiving area of acoustic wave to improve sensitivity without the introduction of additional structures. Meanwhile, the introduction of additional mass and the loss of working frequency band are reduced, and the structure is manufactured at one time. In this paper, the design scheme and optimal size of BCVH are determined via theoretical analysis and simulation, then vector hydrophone calibration system is used to verify it. The experimental results show that the sensitivity of BCVH reaches −183.3 dB (@1kHz, 0dB=1V/μPa), 13.7 dB higher than bionic cilia MEMS vector hydrophone (CVH). Moreover, the depth of concave point of BCVH is more than 30 dB, which has a good directivity.

The Influence of Ambient Temperature on the Sensitivity of MEMS Vector Hydrophone

During underwater acoustic detection, the positioning accuracy of the bionic cilia MEMS vector hydrophone is affected by its own sensitivity. MEMS vector hydrophone operate in different temperature environments, so studies on the environmental temperature and the sensitivity of the MEMS vector hydrophone are of great significance. In this paper, based on the sensitivity of the MEMS vector hydrophone at room temperature (22°C), its sensitivity variation is studied within the temperature range of 0–40°C. The relationship between the temperature and the piezoresistor in the MEMS vector hydrophone is theoretically analyzed, and it is concluded that the sensitivity change is within ±0.6dB. The sensitivity change of MEMS vector hydrophone is proved to be within ±0.3 dB via COMSOL 5.4 simulation software, and the MEMS vector hydrophone is verified experimentally by the hydrophone temperature characteristic testing system. The results show that the variation of the sensitivity is within ±0.5 dB, which is basically consistent with the theoretical analysis results and simulation results. It can be said that under normal non-extreme ambient temperature, the operating temperature has little effect on the sensitivity of the MEMS vector hydrophone.