EP4173728A1

EP4173728A1 - High-power high-frequency directional transmission underwater acoustic transducer and manufacturing method therefor

Info

Publication number: EP4173728A1
Application number: EP20952299.4A
Authority: EP
Inventors: Lei Qin; Chao Zhong; Likun WANG
Original assignee: Beijing Information Science and Technology University
Current assignee: Beijing Information Science and Technology University
Priority date: 2020-09-04
Filing date: 2020-12-04
Publication date: 2023-05-03
Also published as: CN112221917B; CN112221917A; WO2022048058A1; EP4173728A4

Abstract

The invention relates to a high-power high-frequency directional transmission underwate acoustic transducer and a preparation method thereof. The emission water acoustic transducer includes piezoelectric composite material, electrode, matching layer, heat dissipation structure, and wave absorption backing. The Piezoelectric composite material is the 1-1-3 piezoelectric composite material, which is composed of piezoelectric phase, passive phase, and structural phase. The piezoelectric phase is a piezoelectric material column array. The structural phase is a rigid material frame located between the piezoelectric material columns, and the passive phase is a flexible polymer located in the gaps between the piezoelectric phase and the structural phase. The heat dissipation structure is the same rigid material frame as the rigid structure in the piezoelectric composite material; and the sound absorption backing is distributed in the heat dissipation structure. The present invention employs piezoelectric materials with low loss and high voltage resistance, and adopts the 1-1-3 piezoelectric composite structures to design an emission transducer with high-frequency, high-directivity, high-power, low-loss, and fast heat dissipation. The disclosed transducer can realize a continuous transmission of directional energy through acoustic waves within a distance range of 10m in the Marine environment.

Description

TECHNICAL FIELD

The present invention relates to the technical field of piezoelectric transducers, and in particular, relates to a high-frequency hydroacoustic transducer with high-power directional acoustic wave emission, based on a piezoelectric composite material and a preparation method thereof.

BACKGROUND OF THE INVENTION

With the rigorous development of Unmanned Undersea Vehicle (UUV) and underwater sensor network, the energy supply of these equipment sets now requires high automation and long-distance transmission. Traditional salvage charging and electromagnetic underwater wireless charging have high charging efficiency; however, they are difficult to operate and have charging distance of only a few millimeters, which limit their applicability in most of the application scenarios.
In recent years, the wireless transmission technology for underwater power has attracted a significant amount of attention. Such type of charging eliminates the shackles of long wires and could achieve independent packaging, thereby improving the reliability, mobility, and concealment. At present, the underwater wreless energy transmission technology mainly rely on the electromagnetic and the ultrasonic principles, which transmit the energy through electromagnetic field and sound waves as the media, respectively. It is well-known that seawater has good electrical conductivity and high electrical conductivity, and the high-frequency alternating magnetic field induces an electric eddy current loss in seawater, thus affecting the transmission efficiency of electromagnetic transmission. In addition, the charging by transmitting energy through electromagnetic field usually have a range in the order of millimeter. Therefore, it is required in the process of underwater charging to have an accurate connection between the charger and the recipient, which is time consuming and costly. There for, this kind of underwater charging method has poor operability for small size underwater sensor network nodes. It is only suitable for large UUV and other equipment of 100 watts to kilowatt level high-power charging from large underwater fixed charging stations. Under the condition of ensuring the charging efficiency, the acoustic wireless charging can avoid underwater interface and realize long-distance charging without the need for precise positioning. Hence, it is the potential optimal solution for wireless power supply for small UUV and underwater sensor network nodes.
The main advantage of underwater acoustic wireless charging is the long transmission distance under water. Compared with the electromagnetic induction type, this method neither produces the electromagnetic interference, nor is affected by the electromagnetic interference. The wavelength of acoustic wave is much smaller than the electromagnetic wave, which is beneficial for concentrating the energy in the transmission direction. The current research situation shows that underwater acoustic wireless charging can be realized at a distance of 6cm, which validates the feasibility of acoustic wireless charging. Nevertheless, there still exist many technical difficulties to be overcome, due to small transmission power and close action distance. This is due to the neglect of the influence of the hydroacoustic transducer as a sound wave conversion device on the charging effect. First, it results in energy loss due to the use of the same transducers as the transmitting end and receiver end, not using the characteristics of the transmitting transducers and the receiving transducers. Secondly, the scattering loss of sound waves was ignored during transmission, which makes the charging efficiency inefficient. In addition, the existing research on energy conversion efficiency of transducer, heat dissipation problem of emission transducer, acoustic matching of transducer and water, and acoustic energy focus is scarce.
Therefore, the key challenges are to realize the design of high-frequency and high-power directional water acoustic transducer and to solve the heat dissipation problem of the transducer in the future. On one hand, the purpose of traditional underwater acoustic transducer is to improve the detection distance and spatial range as much as possible, which has low frequency and wide beam angle. This transducer suffers from scattering of acoustic energy, and with the increase in transmission distance of the acoustic wave, the energy transmission efficiency of the designed underwater acoustic wireless charging device will inevitably decrease while relying on the traditional transducer. On the other hand, the hydroacoustic transducer usually works in the pulse excitation conditions (such as the pulse duty cycle of 2%) in sonar and hydroacoustic communication. In such case, the internal generated heat can be distributed in time without a special heat dissipation design. However, the transmitting transducer in underwater charging needs a continuous high-power, resulting in large heat generation, which then makes the heat dissipation design a core problem.

SUMMARY OF THE INVENTION

In order to realize the high-power continuous directional transmission of underwater acoustic energy and the wireless power supply of underwater unmanned vehicles and underwater sensor networks, the present invention introduces an emission hydroacoustic transducer with high-frequency, high-power, high-directivity, low-loss and fast heat dissipation, with 1-1-3 piezoelectric composite structure. The adopted piezoelectric composite material has lower loss and higher piezoelectric constants.
The technical solution adopted by the present invention is as follows:
A high-power high-frequency directional emission hydroacoustic transducer is disclosed, which includes piezoelectric composite materials, electrode, matching layer, heat dissipation structure, and wave absorption backing. The composite is a 1-1-3 piezoelectric composite, which contains a piezoelectric phase, a passive phase, and a structural phase. The piezoelectric phase is a piezoelectric material column array. The structural phase is a rigid material frame located between the piezoelectric material columns. The passive phase is a flexible polymer located between the piezoelectric phase and the structural phase. The piezoelectric composite covers the electrode on two surfaces along the thickness direction. The matching layer is located on one side of the piezoelectric composite, while the heat dissipation structure and the wave absorption backing are located on the other side of the piezoelectric composite. The heat dissipation structure is a rigid material frame similar to the structure in piezoelectric composite material. The wave absorption backing is distributed in the heat dissipation structure.
The heat dissipation structure has the same material and size as the heat dissipation structure (i. e., structural phase) contained in the piezoelectric composite material. They match each other accurately to achieve a good heat transfer.
The device includes the enclosure as well as the cable. The enclosing body is a metal shell, and the heat dissipation structure is closely connected to the metal shell for good heat transfer. The cable connects to the leads on the electrode.
The piezoelectric phase of the piezoelectric composite material is composed of low-loss piezoelectric ceramics or piezoelectric crystals. It can include piezoelectric ceramics, piezoelectric crystals, or the like.
The passive phase of the piezoelectric composite material is composed of high-temperature resistant flexible polymer, which can be polyphenylene, polyp-xylene, polyaromatic ether, polyaromatic ester, aromatic polyamide, polyimide, silicone rubber, or the like.
The structural phase of the piezoelectric composite material has good heat dissipation characteristics with grid-type structure. It can include carbon fiber composite materials, low-density metal materials such as aluminum and titanium alloy, or the like.
The matching layer is a trapezoidal matching layer. The lower surface of each trapezoidal matching layer lies against the upper surface of the piezoelectric material column of the piezoelectric composite material.
A method to prepare the above-described high-power high-frequency directional emission hydroacoustic transducer contains the following steps:

1) cutting the whole piece of piezoelectric material into a periodic array of piezoelectric material columns;
2) placing the processed rigid material frame between the columns of piezoelectric material array, filling the passive phase material into the gaps between the rigid material frame and the piezoelectric material column, and then solidifying;
3) grinding the upper and lower surfaces to the required thickness, and fabricating the metal electrodes on upper and lower surfaces to form 1-1-3 piezoelectric composite material;
4) welding the wire on upper and lower electrode surfaces of 1-1-3 piezoelectric composite material;
5) connecting the lower surface of 1-1-3 piezoelectric composite material with the heat dissipation structure of the rigid material frame, and adjusting the rigid material frame to match with the rigid material frame inside the 1-1-3 piezoelectric composite material;
6) affusing or splicing the wave absorption backing material in the heat dissipation structure composed of rigid material frame, and then solidifying;
7) sticking the processed trapezoidal matching layer on the electrode surface of the 1-1-3 piezoelectric composite material, adjusting the lower surface of each trapezoidal matching layer to be against the upper surface of the piezoelectric material column;
8) assembling the structure described in step 7) with the structural components, and welding the wire and watertight cable;
9) putting the structure of step 8) in the mold, filling the mold with waterproof sound wave transmission layer, and then solidifying, to obtain the transducer.

An emission hydroacoustic transducer array includes at least two high-power high-frequency directional hydroacoustic emission transducers described above.
The benefits of the present invention are as follows:
In view of the high demand of wireless power supplies for underwater unmanned vehicles and sensor network nodes, the present invention designs a transmitting transducer with high-frequency, high-directivity, high-power, low-loss and fast heat dissipation by using a 1-1-3 piezoelectric composite structure that contains a piezoelectric ceramic with low loss and high voltage resistance. The disclosed transducer allows continuous directional transmission of sound wave energy up to distances of 10m in the Marine environment.
The invention extends loss and heat dissipation to the piezoelectric composite materials and transducers firstly. Starting from low-loss piezoelectric materials, the heat dissipation structure is introduced into the piezoelectric composite materials, and expanded to the transducer structure. The invention explores the design scheme of high-power and continuous working hydroacoustic emission transducer. The development of this new underwater acoustic emission transducer not only changes the application of traditional high-frequency sonar, but also explores new applications such as underwater directional comunication.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of the high-power, directional water acoustic emission transducer structure.
Figure 2 is a schematic view of the 1-1-3 composite structure, wherein (a) is the stereo view and (b) is the top view.
Figure 3 is the curve of the acoustic performance of directional water acoustic emission transducer, wherein (a) the curve of emission voltage response of sample A, (b) the curve of emission voltage response of sample B, (c) the curves of sound source levels of samples A and B, and (d) the curves of directivity for samples A and B.
Figure 4 is a schematic view of the near-field acoustic radiation characteristics of the emission transducer.

DETAILED DESCRIPTION OF THE INVENTION

The technical content of the present invention will be further described in detail with reference to the accompanying drawings.
The structure of the high-power, directional water acoustic emission transducer of this embodiment is shown in Fig. 1, including a piezoelectric composite material, a matching layer, a heat dissipation structure, a wave absorbing backing, and a waterproof wave transmission layer, and a shell etc. The piezoelectric composite material adopts a large-size 1-1-3 piezoelectric composite material prepared by cutting-perfusion process, so as to realize the high-power and directional emission of sound waves from the transducer. The electrode of piezoelectric composite material (not indicated in Fig. 1) adopts low-temperature curing silver paste, with high soldability and high firmness. The trapezoidal matching layer shown in Fig. 1 was used to achieve acoustic impedance matching and displacement amplification effect, simultaneously.
Traditional transducers use pulse excitation and work in underwater environments, hence they do not require heat dissipation structure. In the present invention, the transmitting transducer works at a high power with continuous sine wave excitation, and thus it is necessary to introduce an additional heat dissipation structure, to extend the heat dissipation mechanism of the composite (via the heat dissipation structure corresponding to the third phase of the piezoelectric composite), so as to achieve a further improvement in heat dissipation. The heat dissipation structure has the same material and structure as those of the third phase material of the 1-1-3 piezoelectric composite. The epoxy resin tungsten powder mixture with high sound impedance is added to the pores of heat dissipation structure, to realize the sound absorption backing.
The 1-1-3 composite structure of this embodiment is shown in Fig. 2, where the piezoelectric column (first phase material, also called as piezoelectric phase) is connected in the z direction, surrounded by a layer of flexible polymer (second phase material, also known as passive phase), and the rigid material (third phase material, also known as structural phase) is connected in the x, y and z directions with playing the role of support. The longitudinal expansion mode of the first phase material in 1-1-3 piezoelectric composite material is used to realize a conversion between vibration energy and electric energy. The low Young's modulus of second phase material allows the piezoelectric column to work in an approximate free vibration state in the piezoelectric composite material, which further improves the energy conversion efficiency. Meanwhile, a rubber with high thermal conductivity is used to timely distribute the heat energy generated by the piezoelectric column and the interface. The high Young's modulus of the third-phase material in the piezoelectric composite material ensures the mechanical stability of the composite material, and carbon fiber or low-density metallic material with high thermal conductivity is selected as the third-phase material to further enhance the heat dissipation. By regulating the proportion of piezoelectric phase in the piezoelectric composite material, the density of the composite material can be lowered, and the acoustic impedance can be reduced, so that it can achieve an optimal matching with the water through a matching layer.
The high-power high-frequency directional emission hydroacoustic transducer shown in Fig. 1 is prepared using the following steps:

1) cutting the whole piezoelectric ceramic into a periodic array of piezoelectric ceramic columns;
2) placing the processed rigid material frame between the piezoelectric ceramic column array, filling the passive phase material (rubber with high thermal conductivity) into the gaps between the frame and the piezoelectric ceramic column, and solidifying;
3) grinding the upper and lower surfaces to the required thickness, and preparing metal electrodes on the upper and lower surfaces to form a 1-1-3 piezoelectric composite material;
4) welding the wire on the upper and lower electrode surfaces of the 1-1-3 piezoelectric composite material;
5) connecting the heat dissipation structure with the lower electrode surface of the 1-1-3 piezoelectric composite material and the rigid material frame each other, and adjusting the rigid material frame of heat dissipation structure to match with the rigid material frame inside the 1-1-3 piezoelectric composite material;
6) affuse or splice wave absorption backing material in the heat dissipation structure composed of rigid material frame, and solidify;
7) sticking the processed trapezoidal matching layer on the electrode surface of the 1-1-3 piezoelectric composite material, and adjusting the lower surface of each trapezoidal matching layer to be against the upper surface of the piezoelectric ceramic column;
8) assembling the above structural components with each other, and welding the wire and watertight cable;
9) putting the above structure in the mold, filling with the waterproof sound wave transmission layer, and solidifying, to obtain the transducer.

Key features of the present invention include:

1) Piezoelectric composite material and high-power hydroacoustic emission transducer heat dissipation technology.

Inside the piezoelectric composite material and subsequently the high-power water acoustic emission transducer, a heat dissipation frame structure with excellent heat dissipation effect (that is, the third phase of piezoelectric composite material) is introduced between the piezoelectric ceramic materials. On one hand, the frame structure of 1-1-3 composite material is cleverly used, not only to ensure mechanical structural to composite, but also to enable efficient heat dissipation. On the other hand, this heat dissipation structure is closer to the source of heat generation, which maximizes the distance of heat transfer and increases the area of heat transfer, so as to achieve a better heat dissipation effect.
2) Wide wave and lateral flap suppression technology of high-power water acoustic emission transducer.
The surface vibration distribution of the 1-1-3 piezoelectric composite material is not uniform. The piezoelectric phase is large, whereas the polymer phase is approximately zero. Therefore, the wave of transducer can be controlled by adjusting the arrangement of transducer according to the principle of acoustic point source radiation superposition. In addition, by adjusting the lateral flap to lateral flap suppression effect. The acoustic energy is mainly concentrated in the main valve, and reduce the energy transmission loss.
To improve the transducer power transmission and control the wave, the disclosed transducer can be arranged in the form of transmitter transducer array, as shown on the left side of Fig. 4. Compared to a single emission transducer, the transducer array has more radiation surface, smaller wave, smaller area of corresponding hydrophone, and farther action distance. Considering the actual working conditions of underwater wireless charging, the receiving hydrophone may appear either in the far field or the near field of transmitting transducer. Therefore, to improve the charging range, the size of hydrophone should not be too small, and an array of receiving hydrophones can be used. The hydrophone can be decomposed into multiple sub-hydrophones in the near-field region of the transmitting transducer. It receives the acoustic energy via the matching sub-hydrophone of the far field of the sub-transmitting transducer. Therefore, in practice, the hydrophone articulations also need the designing of multiple independent charging circuits.
With the underwater acoustic transducer of the present invention, the underwater unmanned vehicles and the underwater sensor networks can be powered wirelessly from a distance. The underwater acoustic transducer achieves the conversion from electric energy to acoustic energy by the reverse piezoelectric effect, and then the acoustic waves are radiated through the water medium. When the acoustic waves reach the hydrophone of the underwater unmanned vehicle or sensor network, the acoustic energy is converted back into electric energy through the piezoelectric effect. Then, the load is charged through the matching circuit.
The present invention prepares the above-mentioned directional water acoustic emission transducer using a large-size piezoelectric composite material. The piezoelectric composite material is 200mm, and the performance index of transducer is shown in Fig. 3. The resonance frequency of the transducer is about 150kHz. The maximum transmission voltage response is 183.6dB, -3dB operating frequency range: 126kHz~174kHz, and the bandwidth is around 48kHz. The maximum sound source level of the transducer is 233.2dB, and -3dB directional open angle is 3 ° , i.e., when the charging distance is 1m, -3dB covering arc length is 5cm; when the charging distance is 10m, -3dB covering arc length is 50cm. The maximum side valve grade of the transducer is -23.65dB, indicating that the energy is mainly concentrated in the main valve.
The above embodiments and drawings of the present invention disclosed are intended to help understand the contents and implementation of the invention, so that ordinary technicians in the art can understand. Various changes and modifications are possible without leaving the spirit and scope of the invention. The present invention shall not be limited to the embodiments of present specification and accompanying drawings. The scope of protection of the present invention shall be subject to the scope defined in the claim.

Claims

A high-power high-frequency directional transmission underwate acoustic transducer, which includes piezoelectric composite materials, electrodes, matching layer, heat dissipation structure, and sound wave absorption backing; the piezoelectric composite is the 1-1-3 piezoelectric composite, consisting of a piezoelectric phase, a passive phase, and a structural phase; the piezoelectric phase is a column array of piezoelectric material; the structural phase is a rigid material frame located between the piezoelectric material columns; the passive phase is a flexible polymer filled between the piezoelectric phase and the structural phase; the piezoelectric composite covers the electrode on two surfaces in the thickness direction; the matching layer is located on one side of the piezoelectric composite; the heat dissipation structure and the sound wave absorption backing are located on the other side of the piezoelectric composite; the heat dissipation structure is a rigid material frame similar to the rigid structure in the piezoelectric composite material; the sound-absorbing backing is distributed in the heat dissipation structure.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, wherein the heat dissipation structure is precisely matched with the structural phase in piezoelectric composite material to achieve a good transfer of heat.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, whichin it further includes a shell and a cable; the shell is metallic, and the heat dissipation structure is tightly connected to the metal shell for good transfer of heat; the cable is connected to a lead on the electrode.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, wherein the piezoelectric phase is a low-loss piezoelectric ceramic or a piezoelectric crystal.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, wherein the passive phase is a high-temperature-resistant flexible polymer.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 5, wherein the passive phase is made of polyphenylene, polyp-xylene, polyaromatic ether, polyaromatic ester, aromatic polyamide, polyimide, or silicone rubber.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, wherein the structural phase has a grid structure fabricated from a material with good heat dissipation properties; the material of structural phase is carbon fiber composite or low-density metallic material.
The high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, wherein the matching layer is a trapezoidal matching layer, and the lower surface of each such trapezoidal matching layer is adjusted against the upper surface of piezoelectric material column of the piezoelectric composite.
A method of preparing the high-power high-frequency directional transmission underwate acoustic transducer according to claim 1, comprising the steps of:
1) cutting the whole piece of piezoelectric material into a periodic array of piezoelectric material columns;

2) placing the processed rigid material frame between the columns of piezoelectric material array, filling the passive phase material into the gaps between the rigid material frame and the piezoelectric material columns, and solidifying;

3) grinding the upper and lower surfaces to the required thickness, and preparing the metal electrodes on the upper and lower surfaces to form the 1-1-3 piezoelectric composite material;

4) welding the wire on the upper and lower electrode surfaces of 1-1-3 piezoelectric composite material;

5) connecting the lower surface of 1-1-3 piezoelectric composite material with the heat dissipation structure of the rigid material frame, and arranging the rigid material frame to match with the rigid material frame inside the 1-1-3 piezoelectric composite material;

6) affuse or splice wave absorption backing material in the heat dissipation structure composed of a rigid material frame, and solidify;

7) sticking the processed trapezoidal matching layer on the electrode surface of the 1-1-3 piezoelectric composite material, and keeping the lower surface of each trapezoidal matching layer against the upper surface of the piezoelectric material column;

8) assembling the structure of step 7) with necessary structural components, and welding the wire and watertight cable;

9) putting the structure of step 8) in the mold, filling with the waterproof sound wave transmission layer, and solidifying, to obtain the transducer.
An hydroacoustic transducer array comprising a high-power high-frequency directional transmission underwate acoustic transducer according to any one of at least two of claims 1~8.