阅读说明：本技术 一种电力机车辅助变流柜无线无源温度感知系统 (Wireless passive temperature sensing system of auxiliary converter cabinet of electric locomotive ) 是由 李林 刘翊 刘凯 杨颖� 莫洪波 黄贵励 吴晗 陈勇 胡凯 沈意平 周剑 段辉 于 2020-10-29 设计创作，主要内容包括：本发明公开了一种电力机车辅助变流柜无线无源温度感知系统,包括声表面波温度感知单元、天线单元和采集单元；所述声表面波温度感知单元安装于电力机车辅助变流柜内待测温度处,所述声表面波温度感知单元通过天线单元与所述采集单元相连；所述声表面波温度感知单元包括衬底、压电基片、天线模块、叉指换能器和反射栅；所述压电基片包括声波传导基片和位于所述声波传导基片上的压电薄膜；所述声波传导基片位于所述衬底上,所述天线模块、叉指换能器和反射栅位于所述压电薄膜上；所述衬底为聚二甲基硅氧烷高分子材料制成的柔性衬底。本发明具有高频化、低时延、高声速、高可靠性、高适应性等优点。(The invention discloses a wireless passive temperature sensing system of an auxiliary converter cabinet of an electric locomotive, which comprises an acoustic surface wave temperature sensing unit, an antenna unit and an acquisition unit, wherein the acoustic surface wave temperature sensing unit is connected with the antenna unit; the acoustic surface wave temperature sensing unit is arranged at a temperature to be detected in the auxiliary converter cabinet of the electric locomotive and is connected with the acquisition unit through the antenna unit; the surface acoustic wave temperature sensing unit comprises a substrate, a piezoelectric substrate, an antenna module, an interdigital transducer and a reflecting grating; the piezoelectric substrate comprises an acoustic wave conduction substrate and a piezoelectric film positioned on the acoustic wave conduction substrate; the acoustic wave conduction substrate is positioned on the substrate, and the antenna module, the interdigital transducer and the reflection grating are positioned on the piezoelectric film; the substrate is a flexible substrate made of polydimethylsiloxane high molecular material. The invention has the advantages of high frequency, low time delay, high sound velocity, high reliability, high adaptability and the like.)

1. A wireless passive temperature sensing system of an auxiliary converter cabinet of an electric locomotive is characterized by comprising an acoustic surface wave temperature sensing unit (1), an antenna unit (2) and an acquisition unit (3); the acoustic surface wave temperature sensing unit (1) is arranged at a temperature to be measured in the auxiliary converter cabinet of the electric locomotive, and the acoustic surface wave temperature sensing unit (1) is connected with the acquisition unit (3) through the antenna unit (2); the surface acoustic wave temperature sensing unit (1) comprises a substrate (101), a piezoelectric substrate (103), an antenna module (106), an interdigital transducer (107) and a reflecting grating (108); the piezoelectric substrate (103) comprises an acoustic wave conductive substrate (1031) and a piezoelectric film (1032) on the acoustic wave conductive substrate (1031); the acoustic wave conducting substrate (1031) is located on the substrate (101), and the antenna module (106), interdigital transducer (107) and reflective grating (108) are located on the piezoelectric film (1032); the substrate (101) is a flexible substrate made of polydimethylsiloxane high polymer material.

2. The wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive according to claim 1, wherein the sound wave conducting substrate (1031) comprises a diamond film.

3. The wireless passive temperature sensing system of the electric locomotive auxiliary converter cabinet according to claim 1, wherein the interdigital transducer (107) is prepared on the piezoelectric substrate (103) by an electron beam exposure technique.

4. The wireless and passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive according to claim 1, 2 or 3, characterized in that a sound absorption layer (104) is applied to the surface of the piezoelectric film (1032) for absorbing bulk acoustic wave signals in surface acoustic waves.

5. The wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive according to claim 1, 2 or 3, characterized in that a first temperature compensation layer (102) is arranged between the sound wave conduction substrate (1031) of the piezoelectric substrate (103) and the substrate (101), a second temperature compensation layer (105) is arranged on the piezoelectric film (1032), and the interdigital transducer (107) and the reflection grating (108) are both arranged between the piezoelectric film (1032) and the second temperature compensation layer (105).

6. The wireless passive temperature sensing system of an electric locomotive auxiliary converter cabinet according to claim 5, characterized in that the first temperature compensation layer (102) and the second temperature compensation layer (105) are both alumina.

7. The wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive according to claim 1, 2 or 3, wherein the surface acoustic wave temperature sensing unit (1) is packaged into a patch type structure or a tuning fork type structure.

8. The wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive according to claim 1, 2 or 3, characterized in that the antenna unit (2) is plate-shaped.

9. The wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive as claimed in claim 1, 2 or 3, wherein the antenna unit (2) is correspondingly configured with a plurality of surface acoustic wave temperature sensing units (1) with different resonant frequencies; each acquisition unit (3) is networked and connected with the centralized server.

10. The wireless and passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive as claimed in claim 1, 2 or 3, further comprising an alarm unit connected to the acquisition unit (3) for alarming when the real-time temperature or the temperature change rate exceeds a corresponding preset value.

Technical Field

The invention mainly relates to the technical field of temperature sensing, in particular to a wireless passive temperature sensing system for an auxiliary converter cabinet of an electric locomotive.

Background

The traction power of the electrified railway is an electric locomotive, the power supply safety is always the guarantee of fire safety and reliable operation of the locomotive, and the practical significance of ensuring the power supply safety and further ensuring the safe and stable operation of the train is very important. The locomotive power supply voltage is usually more than 25KV, the required energy is provided by an electric traction power supply system, and the energy supply mode adopts a pantograph to obtain electric energy from a contact network and then transmits the electric energy to an electric system to drive a traction train to operate. The electric system of the electric locomotive consists of a main transmission system, an auxiliary electric control system and a control circuit system, wherein the control circuit is a main command circuit, and a driver sends an instruction through the main command circuit to indirectly control the main circuit and the auxiliary circuit of the locomotive so as to finish various working condition operations. The main command electric circuit comprises a 110V direct current stabilized power supply, a storage battery pack, a main command electric appliance for controlling different states (traction, braking, forward, backward, accelerated parking and the like) of the locomotive and controlling the starting and stopping of each auxiliary machine and lighting operation, and low-voltage electric appliances and switches with various functions.

The method is a key link for ensuring the operation safety of the electric locomotive, wherein the temperature in the auxiliary converter cabinet is one of very important monitoring parameters. In the process of high-speed operation of the electric locomotive, the contact resistance of a busbar node in a cabinet is increased due to loosening, aging, electric arc impact and the like, the phenomenon of temperature rise is shown, and then the faults of a vehicle power supply system and the damage of the vehicle are caused, even serious accidents of vehicle fire can occur, the operation is interrupted, and the consequences are very serious. Meanwhile, an online temperature sensing system is not installed in the conventional auxiliary converter cabinet, the visualization, intelligentization and big data degree is not enough, and the internal temperature state of the auxiliary converter cabinet is a 'blind zone' in work, so that accurate accident analysis cannot be carried out, and an accurate accident treatment suggestion cannot be given. Therefore, the temperature of the auxiliary converter cabinet under the running state of the electric locomotive can be monitored in real time on line, so that the running safety of the train can be ensured, and the method has important practical significance for the safe and stable running of the train.

At present, the temperature monitoring at home and abroad mainly comprises the following detection means: compared with the traditional method, the traditional method is temperature indication paper and manual temperature measurement, but the traditional method has low efficiency and cannot realize online temperature monitoring; in addition, the infrared thermal imaging temperature measurement is carried out by utilizing a thermal imaging principle, but the area of a detection area is limited, and only the temperature in an unobstructed and visible range can be monitored; the fiber grating sensing temperature measurement is carried out by using the principle of expansion with heat and contraction with cold of a grating structure, but needs wired connection, has complex wiring and is easy to break an optical fiber; active wireless temperature measurement carries out wireless temperature measurement through using the battery to the sensor power supply, but the battery life is limited, must regularly change the battery, and has weeping, the hidden danger of even exploding of firing under the high voltage environment. In summary, the current popular temperature measurement method at home and abroad is difficult to adapt to the strong electromagnetism, severe vibration and closed environment of the auxiliary converter cabinet of the electric locomotive in the high-speed running process, and the research belongs to the domestic blank.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the problems in the prior art, the invention provides a wireless passive temperature sensing system of an auxiliary converter cabinet of an electric locomotive, which has high frequency, high sound velocity and high reliability.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

a wireless passive temperature sensing system of an auxiliary converter cabinet of an electric locomotive comprises an acoustic surface wave temperature sensing unit, an antenna unit and an acquisition unit; the acoustic surface wave temperature sensing unit is arranged at a temperature to be detected in the auxiliary converter cabinet of the electric locomotive and is connected with the acquisition unit through the antenna unit; the surface acoustic wave temperature sensing unit comprises a substrate, a piezoelectric substrate, an antenna module, an interdigital transducer and a reflecting grating; the piezoelectric substrate comprises an acoustic wave conduction substrate and a piezoelectric film positioned on the acoustic wave conduction substrate; the acoustic wave conduction substrate is positioned on the substrate, and the antenna module, the interdigital transducer and the reflection grating are positioned on the piezoelectric film; the substrate is a flexible substrate made of polydimethylsiloxane high molecular material.

As a further improvement of the above technical solution:

the acoustic wave conductive substrate includes a diamond film.

The interdigital transducer is prepared on the piezoelectric substrate by an electron beam exposure technology.

And the surface of the piezoelectric film is laid with a sound absorption layer for absorbing bulk acoustic wave signals in the surface acoustic wave.

A first temperature compensation layer is arranged between the sound wave conduction substrate of the piezoelectric substrate and the substrate, a second temperature compensation layer is arranged on the piezoelectric film, and the interdigital transducer and the reflection grating are both located between the piezoelectric film and the second temperature compensation layer.

The first temperature compensation layer and the second temperature compensation layer are both made of aluminum oxide.

And the surface acoustic wave temperature sensing unit is packaged into a surface mounted structure or a tuning fork structure.

The antenna unit is plate-shaped.

The antenna unit is correspondingly provided with a plurality of surface acoustic wave temperature sensing units with different resonant frequencies; and the acquisition units are networked and are connected with the centralized server.

The temperature monitoring device also comprises an alarm unit, wherein the alarm unit is connected with the acquisition unit and used for giving an alarm when the real-time temperature or the temperature change rate exceeds a corresponding preset value.

Compared with the prior art, the invention has the advantages that:

(1) aiming at strong electromagnetism, severe vibration and a closed environment in the auxiliary converter cabinet of the electric locomotive, the wireless passive high-frequency surface acoustic wave temperature sensing unit is used for realizing the online temperature monitoring function in the cabinet, and compared with other temperature measuring modes, the invention has the following advantages and characteristics: the wireless passive high-frequency surface acoustic wave temperature sensing unit is made of piezoelectric materials and does not contain a semiconductor device, so that the wireless passive high-frequency surface acoustic wave temperature sensing unit is a coreless device, has a wide working temperature range and is suitable for working in a high-speed rail-40-150 ℃; the interior of the wireless passive high-frequency surface acoustic wave temperature sensing unit works by sound waves, no circuit is provided, no battery is needed for power supply, hidden dangers such as high-temperature explosion and chemical leakage of the battery are avoided, wireless passive reading is really realized, complicated wiring in the auxiliary converter cabinet is avoided, the wireless passive high-frequency surface acoustic wave temperature sensing unit can be attached to the surface of a busbar, and compared with a semiconductor technology, the wireless passive high-frequency surface acoustic wave temperature sensing unit is free of threshold voltage limitation in principle; the wireless passive high-frequency surface acoustic wave temperature sensing unit is internally provided with no circuit, has strong anti-interference capability and excellent high-voltage and electromagnetic radiation resistance; the working environment depends on the tolerance of the piezoelectric material and the metal film, and can work in extreme environments, such as severe environments with high temperature resistance, acid and alkali resistance and the like, as long as the selected material and the related structure are appropriate.

(2) The acoustic surface wave temperature sensing unit adopts a resonator type high-frequency SAW temperature sensing device, and compared with a resonator type low-frequency SAW temperature sensing device, the resonator type high-frequency SAW temperature sensing device has the characteristics of low time delay, high acoustic velocity, high reliability and the like, and can better adapt to high voltage, strong electromagnetism, severe vibration and a closed environment of an electric locomotive.

(3) In order to obtain a high-frequency surface acoustic wave temperature sensing device, on one hand, a method for improving the SAW frequency is to prepare a high-acoustic-speed piezoelectric substrate. The traditional integrated piezoelectric substrate is decomposed into an acoustic wave conduction substrate and a piezoelectric film positioned on the acoustic wave conduction substrate; the acoustic wave conduction substrate can provide a path for fast propagation of acoustic waves, the piezoelectric film ensures the piezoelectric effect of the piezoelectric substrate, namely, on the basis of ensuring the normal piezoelectric effect of the piezoelectric substrate, the acoustic waves are fast propagated through the acoustic wave conduction substrate, and therefore high frequency of the acoustic surface wave temperature sensing device is achieved. In particular, diamond has the fastest sound velocity (12000m/s) and extremely high Young modulus, and is very suitable for being used as an acoustic wave conduction substrate. However, diamond does not have piezoelectric property, so a piezoelectric film is usually deposited on diamond to form a piezoelectric film/diamond layer structure high sound speed piezoelectric substrate.

(4) On the other hand, the method for improving the SAW frequency is to reduce the period of the interdigital electrode and reduce the wavelength. The IDT of the traditional low-frequency SAW device is prepared by adopting an ultraviolet lithography technology, the technology is limited by ultraviolet wavelength (0.20-4 mu m), the frequency of the prepared SAW is generally below 3GHz, and the requirements of a high-frequency SAW device cannot be met. The IDT preparation of the invention adopts a higher-precision electron beam Exposure (EBL) technology, and can process an IDT structure with smaller size, wherein the smaller the size of the IDT is, the higher the SAW frequency is; the IDT material adopts composite metals such as Al, Al/Ti, Al/Cr, Al/Ti/Cu/Ti, Pt/Rh and the like.

(5) The surface of the piezoelectric film is laid with the sound absorption layer for absorbing the bulk acoustic wave signals in the surface acoustic wave, so that the separation of the surface acoustic wave and the bulk acoustic wave signals is realized, and the accuracy of subsequent signal detection is ensured.

(6) A first temperature compensation layer is arranged between a sound wave conduction substrate and a substrate of the piezoelectric substrate, a second temperature compensation layer is arranged on a piezoelectric film, and an interdigital transducer and a reflection grating are both positioned between the piezoelectric film and the second temperature compensation layer. The piezoelectric substrate is arranged in the upper temperature compensation layer and the lower temperature compensation layer, and the temperature compensation of the wave speed of the surface acoustic wave is realized from the upper direction and the lower direction. The first temperature compensation layer and the second temperature compensation layer are made of materials with low thermal expansion coefficients, so that the self thermal expansion effect of a piezoelectric substrate (mainly a piezoelectric film) sandwiched between the two layers can be limited, and the temperature compensation effect of the surface acoustic wave device, particularly the high-frequency surface acoustic wave device, can be effectively improved. In addition, the mode of covering the second temperature compensation layer on the small-sized metal electrode (namely the interdigital transducer and the reflecting grating) can effectively inhibit the acoustic migration effect of the electrode material under the working conditions of high temperature and high power, thereby improving the reliability of the surface acoustic wave device. Furthermore, the second temperature compensation layer can also serve as a protective layer, so that the degradation problem of the piezoelectric film and the metal electrode in a high-temperature environment can be solved, the high-temperature resistance of the device is enhanced, the corrosion of the external environment to the surface of the device is isolated, and the working time of the device in the high-temperature environment is prolonged.

(7) The substrate of the invention adopts a flexible substrate and is made of PDMS high polymer material, and the thickness of the substrate is about 500 mu m. The PDMS-based flexible substrate used as the surface acoustic wave can also transmit the surface acoustic wave, and when the temperature is slightly changed, the propagation of the surface acoustic wave on the flexible substrate is affected, so that a device based on the flexible substrate also has sensitive temperature response.

Drawings

Fig. 1 is a schematic structural diagram of a resonator type vssaw temperature sensing device according to the present invention.

Fig. 2 is a schematic structural diagram of a wireless passive temperature sensing system of an auxiliary converter cabinet of an electric locomotive.

Fig. 3 is a schematic top view of the surface mount type high-frequency temperature sensing device according to the present invention.

Fig. 4 is a schematic side view of the patch type high-frequency temperature sensing device according to the present invention.

FIG. 5 is a schematic top view of the tuning fork high frequency temperature sensing device of the present invention.

FIG. 6 is a schematic side view of the tuning fork high frequency temperature sensing device of the present invention.

Fig. 7 is a schematic networking diagram of the wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive.

FIG. 8 is a diagram illustrating an internal analysis system of an electric locomotive according to the present invention.

The reference numbers in the figures denote: 1. a surface acoustic wave temperature sensing unit; 101. a substrate; 102. a first temperature compensation layer; 103. a piezoelectric substrate; 1031. an acoustic wave conductive substrate; 1032. a piezoelectric film; 104. a sound absorbing layer; 105. a second temperature compensation layer; 106. an antenna module; 107. an interdigital transducer; 108. a reflective grating; 109. a base; 1010. a housing; 2. an antenna unit; 3. and a collecting unit.

Detailed Description

The invention is further described below with reference to the figures and the specific embodiments of the description.

As shown in fig. 1, the wireless passive temperature sensing system of the auxiliary converter cabinet of the electric locomotive in the embodiment includes a surface acoustic wave temperature sensing unit 1, an antenna unit 2 and an acquisition unit 3; the acoustic surface wave temperature sensing unit 1 is arranged at a temperature to be measured in an auxiliary converter cabinet of the electric locomotive, and the acoustic surface wave temperature sensing unit 1 is connected with the acquisition unit 3 through the antenna unit 2; the surface acoustic wave temperature sensing unit 1 comprises a substrate 101, a piezoelectric substrate 103, an antenna module 106, an interdigital transducer 107 and a reflecting grating 108; the piezoelectric substrate 103 includes an acoustic wave conductive substrate 1031 and a piezoelectric film 1032 located on the acoustic wave conductive substrate 1031; an acoustic wave conducting substrate 1031 is positioned on the substrate 101 and an antenna module 106, an interdigital transducer 107, and a reflective grating 108 are positioned on the piezoelectric film 1032.

In practical application, the acquisition unit 3 transmits a Radio Frequency (RF) query electromagnetic wave signal to the surface acoustic wave temperature sensing unit 1 through the antenna unit 2; the surface acoustic wave temperature sensing unit 1 receives an inquiry RF signal through the antenna module 106, and the interdigital transducer 107 converts the received RF signal into a surface acoustic wave (SAW acoustic wave) through an inverse piezoelectric effect; SAW acoustic waves propagate along the surface of the piezoelectric substrate 103 and are reflected when the SAW encounters the reflective grating 108 (or array of reflective gratings), all of the reflected signals add up and excite an RF electrical signal; the RF electrical signal is again converted by the interdigital transducer 107IDT into an echo electromagnetic wave signal by the piezoelectric effect, wherein the signal carries temperature information; the echo electromagnetic wave signal is transmitted back to the antenna unit 2 through the antenna module 106, the antenna unit 2 transmits the echo electromagnetic wave signal to the acquisition unit 3, and the temperature information is obtained after the echo electromagnetic wave signal is demodulated through the acquisition unit 3.

Aiming at strong electromagnetism, severe vibration and a closed environment in an auxiliary converter cabinet of an electric locomotive, the wireless passive high-frequency surface acoustic wave temperature sensing unit 1 is used for realizing the online temperature monitoring function in the cabinet, and compared with other temperature measuring modes, the invention has the following advantages and characteristics:

the wireless passive high-frequency surface acoustic wave temperature sensing unit 1 is made of piezoelectric materials and does not contain a semiconductor device, so that the wireless passive high-frequency surface acoustic wave temperature sensing unit is a coreless device, has a wide working temperature range and is suitable for working in a high-speed rail-40-150 ℃;

the interior of the wireless passive high-frequency surface acoustic wave temperature sensing unit 1 works by sound waves, no circuit is provided, no battery is needed for power supply, hidden dangers such as high-temperature explosion and chemical leakage of the battery are avoided, wireless passive reading is really realized, complicated wiring in an auxiliary converter cabinet is avoided, the wireless passive high-frequency surface acoustic wave temperature sensing unit can be attached to the surface of a busbar, and compared with a semiconductor technology, the wireless passive high-frequency surface acoustic wave temperature sensing unit is free of threshold voltage limitation in principle;

the wireless passive high-frequency surface acoustic wave temperature sensing unit 1 is internally provided with no circuit, has strong anti-interference capability and excellent high-voltage and electromagnetic radiation resistance; the working environment depends on the tolerance of the piezoelectric material and the metal film, and can work in extreme environments, such as severe environments with high temperature resistance, acid and alkali resistance and the like, as long as the selected material and the related structure are appropriate.

In this embodiment, the surface acoustic wave temperature sensing unit 1 employs a resonator type SAW temperature sensing device, and specifically includes an interdigital transducer 107(IDT) and two sets of reflection gratings 108 (or reflection grating arrays), where the interdigital transducer 107 is located in the center of the piezoelectric substrate 103, and the two sets of reflection gratings 108 are located on the piezoelectric substrate 103 on both sides of the piezoelectric substrate 103. By designing the structure of the reflection grating 108 and the shape of the IDT, the IDT can excite a SAW acoustic wave satisfying the bragg reflection condition, and coherent reflected waves are generated at both ends of the piezoelectric substrate 103 at the same time, and resonance is generated, so that energy is resident on the piezoelectric substrate 103, and the piezoelectric substrate 103 forms a resonator with a high Q value. In this configuration, the grating 108 forms an acoustic mirror and the interdigital transducer 107 forms an acoustic resonator, and the IDT directs the excitation energy into the harmonicAnd the energy in the resonant cavity can be continuously emitted through the antenna module 106 when the electromagnetic excitation signal is ended. When the excitation frequency f is equal to the natural frequency f of the resonant cavity₀In time, the temperature sensing device will resonate due to the high Q value of the quality factor of the temperature sensing device.

Furthermore, the acoustic surface wave temperature sensing unit 1 adopts a resonator type high-frequency SAW temperature sensing device, and compared with a resonator type low-frequency SAW temperature sensing device, the resonator type high-frequency SAW temperature sensing device has the characteristics of low time delay, high sound velocity, high reliability and the like, and can better adapt to high voltage, strong electromagnetism, severe vibration and a closed environment of an electric locomotive. Wherein the low frequency is 30kHz-300kHz, the intermediate frequency is 300kHz-30MHz, the high frequency is 30MHz-3GHz, and the ultrahigh frequency is 3GHz-30 GHz.

The relationship between the wave propagation speed of the SAW resonant cavity and the external temperature, stress, strain and mass load is as follows:

whereinIs the mass density;is strain;is a stress;is surface tension;is the temperature;

under the condition of considering the influence of a single variable, the SAW temperature sensing device is attached to the key part of the busbar, and when the temperature of the busbar changes, the wave velocity changes, so that the inherent frequency changes. The temperature information can be calculated by accurately sensing the natural frequency of the SAW temperature sensing device or the related phase information thereof, and the linear relationship between the temperature and the natural frequency can be realized through reasonable design.

In this embodiment, the resonant operating frequency f of the high-frequency SAW temperature sensing device₀Determined by the SAW propagation velocity VR0 and the wavelength λ, f₀VR0/λ, where the wavelength is equal to the distance of a pair of fingers. In order to obtain a high-frequency surface acoustic wave temperature sensing device, on one hand, a method for improving the SAW frequency is to prepare a high-acoustic-speed piezoelectric substrate 103. The piezoelectric substrate 103 of the SAW device is mainly a piezoelectric single crystal (quartz, LiNbO3, LiTaO3, and the like), and the sound velocity thereof is generally 3000 to 4000m/s, which is not favorable for increasing the frequency. In the present embodiment, the presently conventional integrated piezoelectric substrate 103 is decomposed into the acoustic wave conductive substrate 1031 and the piezoelectric film 1032 on the acoustic wave conductive substrate 1031; the acoustic wave conduction substrate 1031 can provide a path for fast propagation of acoustic waves, and the piezoelectric film 1032 ensures the piezoelectric effect of the piezoelectric substrate 103, that is, on the basis of ensuring the normal piezoelectric effect of the piezoelectric substrate 103, the acoustic waves are fast propagated through the acoustic wave conduction substrate 1031, so that the high frequency of the surface acoustic wave temperature sensing device is realized; the split design of the piezoelectric substrate 103 can select a good sound wave conduction medium, and on the other hand, the normal piezoelectric effect cannot be influenced. In particular, diamond has the fastest sound velocity (12000m/s), extremely high Young's modulus, and is well suited for use as the acoustic wave conduction substrate 1031. Since diamond does not have piezoelectric properties, a piezoelectric film 1032 is generally deposited on diamond, and a piezoelectric film 1032/diamond layer structure high acoustic velocity piezoelectric substrate 103 is formed. The piezoelectric film 1032 is prepared on the diamond film through preparation processes such as electron beam evaporation, magnetron sputtering and ion beam sputtering. The piezoelectric film 1032 can be made of similar materials with high sound speed and excellent piezoelectric effect, such as AlN, ZnO, AlScN and the like. The acoustic wave conductive substrate 1031 may also be made of a high-density material such as diamond or sapphire.

On the other hand, the method for increasing the SAW frequency is to reduce the period of the interdigital electrode and reduce the wavelength. The IDT of the traditional low-frequency SAW device is prepared by adopting an ultraviolet lithography technology, the technology is limited by ultraviolet wavelength (0.20-4 mu m), the frequency of the prepared SAW is generally below 3GHz, and the requirements of a high-frequency SAW device cannot be met. Therefore, the IDT in this embodiment is prepared by using a higher-precision electron beam Exposure (EBL) technique (which belongs to the application of the conventional technique and is not described herein), and an IDT structure with a smaller size can be processed, wherein the smaller the size of the IDT, the higher the SAW frequency; the IDT material adopts composite metals such as Al, Al/Ti, Al/Cr, Al/Ti/Cu/Ti, Pt/Rh and the like.

In this embodiment, a sound absorption layer 104 (a thin film layer made of a high-conductivity polymer synthesized from polyaniline, polypyrrole, and octa-carboxyl copper phthalocyanine and graphite) is laid on the surface of the piezoelectric film 1032 and is used for absorbing bulk acoustic wave signals in the surface acoustic wave, so that separation of the surface acoustic wave and the bulk acoustic wave signals is realized, and accuracy of subsequent signal detection is ensured.

In this embodiment, a first temperature compensation layer 102 is disposed between the acoustic wave conduction substrate 1031 of the piezoelectric substrate 103 and the substrate 101, a second temperature compensation layer 105 is disposed on the piezoelectric film 1032, and the interdigital transducer 107 and the reflective grating 108 are both disposed between the piezoelectric film 1032 and the second temperature compensation layer 105. The piezoelectric substrate 103 is arranged in the upper and lower temperature compensation layers, and realizes the temperature compensation of the surface acoustic wave velocity from the upper and lower directions. The first temperature compensation layer 102 and the second temperature compensation layer 105 are made of materials with low thermal expansion coefficients, so that the self thermal expansion effect of the piezoelectric substrate 103 (mainly a piezoelectric film 1032) sandwiched between the two temperature compensation layers can be limited, and the temperature compensation effect of the surface acoustic wave device, particularly the high-frequency surface acoustic wave device, can be effectively improved.

In addition, the acoustic migration effect of the electrode material under high-temperature and high-power operating conditions can be effectively suppressed by covering the second temperature compensation layer 105 on the small-sized metal electrodes (i.e., the interdigital transducer 107 and the reflection grating 108), thereby improving the reliability of the surface acoustic wave device. As the second temperature compensation layer 105, the material thereof is preferably Al having a low/negative thermal expansion temperature coefficient or a low/negative wave speed temperature coefficient₂O₃The thickness is preferably in the range of 1 μm to 20 μm. Of course, in other embodiments, the second temperature compensation layer 105 can be the same as the first temperature compensation layerSiO₂、ZrO₂、TeO₂、ZrW₂O₈Any one or more materials of diamond, diamond-like carbon, sapphire and the like. Further, the second temperature compensation layer 105 can also serve as a protection layer, so that the degradation problem of the piezoelectric film 1032 and the metal electrode in a high-temperature environment can be solved, the high-temperature resistance of the device is enhanced, meanwhile, the corrosion of the external environment to the surface of the device is isolated, and the working time of the device in the high-temperature environment is prolonged.

In this embodiment, the piezoelectric film 1032 is made of PVDF (polyvinylidene fluoride) and has a thickness of about 30 μm. Interdigital transducer 107 is made of a gold thin film having a thickness of about 500 nm. The reflective grating 1081 is made of a gold thin film, and has a thickness of about 500 nm. The substrate 101 is a flexible substrate 101 made of PDMS polymer (Polydimethylsiloxane) with a thickness of about 500 μm. When the external temperature changes, the surface acoustic wave is influenced by the external temperature during transmission, and surface acoustic waves with different waveforms are formed. The flexible substrate 101 based on PDMS as the surface acoustic wave can also transmit the surface acoustic wave, and when the temperature changes slightly, the propagation of the surface acoustic wave on the flexible substrate 101 is affected, so the device based on the flexible substrate 101 has a more sensitive temperature response.

In this embodiment, before the surface acoustic wave temperature sensing unit 1 is applied to the field, it and a standard temperature measuring device (such as a calibrated PT100 temperature measuring device or a thermocouple temperature measuring device) are placed in the same high and low temperature chamber, and the measurement data of the surface acoustic wave temperature sensing unit 1 and the data of the standard temperature measuring device are monitored at the same time, and the data are accumulated through multiple batches of experiments, compared, analyzed, and fitted to study whether the data are convergent and linear, and how to achieve the expected accuracy by adjusting parameters. After the adjustment work is finished, the surface acoustic wave temperature sensing unit 1 is installed in the field auxiliary converter cabinet.

In this embodiment, according to the specific conditions of the size and the distribution of the busbar in the auxiliary converter cabinet, the packaging form and the installation mode of the surface acoustic wave temperature sensing unit 1 are designed in a customized manner, and the surface acoustic wave temperature sensing unit 1 is fastened at a temperature to be measured (such as on the busbar or a fastening bolt) in the auxiliary converter cabinet. According to different structures of the busbar at the mounting part, the surface acoustic wave temperature sensing unit 1 is packaged into a surface mounted type tuning fork structure. As shown in fig. 3, the surface acoustic wave temperature sensing unit 1 is attached to the base 109 and is packaged in the plastic housing 1010, and the surface acoustic wave temperature sensing unit can be attached to a part to be measured by using high-temperature glue. As shown in fig. 5, the tuning fork structure is installed at the joint of the fastening bolt, the copper sheet at the bottom of the tuning fork structure is made into a tuning fork-shaped base 109, and the tuning fork-shaped base can be directly fixed by the bolt, and the surface acoustic wave temperature sensing unit 1 is attached to the base 109 and is simultaneously packaged in the plastic shell 1010. If no bolts are available, they can be secured by special clamps or ties. The change of structure is carried out according to its installation environment to the aforesaid, sets up surface acoustic wave temperature perception unit 1 into multiple structure, and the strong vibration environment of adaptation that can be better can show improvement its practicality.

In this embodiment, the antenna unit 2 (or called as a reading antenna) is installed on an inner wall of the auxiliary converter cabinet. Because the auxiliary converter cabinet has higher insulation requirement, the space in the cabinet is narrow, and the antenna unit 2 cannot have too high protrusions, the antenna unit 2 is made into a plate shape, and the potential safety hazard is avoided. In addition, a strong elastic magnet (the adsorption force is over 1 kilogram) is arranged at the bottom of the plate-shaped antenna unit 2, so that the installation firmness is ensured.

In this embodiment, the acquisition unit 3 (e.g., an acquisition unit) is similar to a pulse radar transceiver. When the temperature sensor works, the temperature sensor continuously emits pulse frequency sweeping signals, and the emitted signals can excite the resonance of the surface acoustic wave temperature sensing unit 1, so that a reader can detect the resonance frequency of the device, and a temperature value is analyzed. Specifically, one end of the collector is provided with a plurality of antenna interfaces for wired connection of the antenna unit 2 (such as a reading antenna), and the number of the antenna interfaces is determined according to the number of devices. The other end of the collector is provided with a power supply and a communication interface, including an RS485 interface, an RS232 interface and the like.

In specific application, aiming at high voltage, strong electromagnetism, severe vibration and a closed environment of the auxiliary converter cabinet, in order to ensure signal quality, the temperature sensing system is matched with a standard of a reading antenna according to each 6 surface acoustic wave temperature sensing units 1 (or called temperature sensing devices, the same below). Potential heating hidden trouble positions of the auxiliary converter cabinet are bus bar nodes and fastening bolts, the bus bar nodes or the fastening bolts in the cabinet can cause contact resistance increase due to loosening, aging, electric arc impact and the like, the phenomenon of temperature rise is shown, and a patch type or tuning fork type structure can be selected according to the specific distribution situation of the bus bars in the cabinet and is installed at a proper temperature measuring point. In addition, the surface acoustic wave temperature sensing unit 1 is powered by no power supply and works by absorbing the energy of the query signal of the reading antenna, so that the signal is very weak, and the reading antenna cannot be far away from the temperature sensing device. Ideally the maximum distance is about 2 meters. When the environment is shielded by obstacles or the installation angle is not good, the effect is better when the distance is less than 1 meter. So that 1 reading antenna is respectively adsorbed on the inner walls of the two sides of the cabinet body. The collector is in wired connection with the reading antenna, and the collector can be installed in a cab.

In addition, through reasonable design, SAW temperature sensing devices with different resonant frequencies can be used to form a set of online temperature monitoring system, through frequency division multiple access technology, one reading antenna transmits a frequency band containing 6 resonant frequencies of the high-frequency SAW temperature sensing devices, simultaneously excites all the temperature sensing devices, and the reading antenna receives reflected Bragg base frequency signals, so that temperature information sensed by the different temperature sensing devices can be coded and identified, and distributed multipoint temperature measurement in the auxiliary converter cabinet is realized.

As shown in fig. 7, each auxiliary converter cabinet is provided with two sets of temperature sensing systems, all the temperature sensing systems are networked through an RS485 bus and can be connected to a centralized server of a control center, and temperature data and numbers of temperature measuring points of all the auxiliary converter cabinets are uploaded to the centralized server. Of course, wireless data transmission can be used to replace the RS485 bus, and a wireless module and an antenna can be added to each collector. In addition, the RS485 interface of the collector is replaced by a wireless module for transmission, so that an internal wireless local area network is formed. In other embodiments, other wireless transmission schemes may be employed, such as WIFI, ZIGBEE, 5G, and the like.

As shown in fig. 8, the whole system includes a plurality of communication modules, and the communication functions can be selected according to the needs. When the electric locomotive is installed, the industrial Ethernet or the multifunctional vehicle bus is connected with the vehicle-mounted wireless transmission gateway, and the data is transmitted to the ground analysis system for further analysis and display through the WIFI or 4G or 5G wireless communication module of the vehicle-mounted wireless transmission gateway.

In order to reduce the data transmission quantity and accelerate the temperature abnormal condition discovery and diagnosis, an intelligent analysis module based on an FPGA (field programmable gate array) is arranged in the temperature measurement system, the intelligent analysis can be carried out on the collected temperature data in the system, and the analyzed data also comprises the data of the working state of the train traction system transmitted through the multifunctional vehicle bus in addition to the collected temperature data so as to determine the working load of the auxiliary converter cabinet. The program control logic can be divided into the following three types according to actual requirements by analyzing the program preset in the intelligent analysis module: 1. setting a fixed temperature threshold value according to the running condition of the train, and alarming if the fixed temperature threshold value is exceeded; 2. alarming when the temperature rapidly rises according to the time change rate of the temperature; 3. and (3) using a recurrent neural network analysis, taking the working state of the traction system and temperature data of a period of time as input, and alarming when the trend that the temperature exceeds a threshold value occurs. The method comprises the steps that diagnosis data and original temperature data are output to a traction control system of the electric locomotive through a multifunctional vehicle bus, meanwhile, in order to guarantee that the system has an alarm function when the train network communication fails, a group of 110V hard-wire control circuit outputs are further included, when the 110V output is power-off, the temperature is over a threshold value, and the traction system stops traction and current transformation to reduce the temperature of a main transformer cabinet.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.