Wireless passive ultrasonic sensor array monitoring system and monitoring method

Abstract

A wireless passive ultrasonic sensor array monitoring system and monitoring method. Three groups of coils sensor coils (131), transmitting coils (211) and receiving coils (311) are designed on the basis of the principle of inductive coupling, and are respectively connected to ultrasonic sensors (113), a controller output end and a controller input end. Wireless signal and power transmission can be performed between the sensor coils (131) and the transmitting coils (211) / receiving coils (311), so as to implement wireless passive operation of sensors, thus improving the detection efficiency. An m×n array of the ultrasonic sensors (113) is provided; and by means of combining phased array technology and an imaging algorithm, the present disclosure enables more accurate thickness measurement, and enables defect imaging functions which satisfy the monitoring requirements for cracks, pinhole corrosion and other non-uniform defects, thus broadening the application field of wireless passive sensors.

Description

A wireless passive ultrasonic sensor array monitoring system and monitoring method

[0001] This application claims priority to application number 202410815312.1 filed on June 24, 2024, entitled "A Wireless Passive Ultrasonic Sensor Array Monitoring System and Monitoring Method", originally accepted by the agency in China. Technical Field

[0002] This invention relates to the field of ultrasonic measurement technology, and in particular to a wireless passive ultrasonic sensor array monitoring system and monitoring method. Background Technology

[0003] In existing technology, the basic structure of a wireless passive sensor system based on inductive coupling is shown in Figure 1. Two coils A and B are connected to the controller, and two coils C and D are connected to the sensor. The four coils are placed close to each other and transmit signals / power through inductive coupling. The controller transmits electrical energy to coil C through coil A to excite the sensor. The sensor signal is transmitted from coil D to coil B and returned to the controller for signal processing. In this system, no wires are needed between the sensor and the controller, and no power supply is required at the sensor end, forming a wireless passive sensor system. Inductive coupling refers to the phenomenon where, when alternating current is passed through one coil, an induced current is generated in another nearby coil due to electromagnetic induction. Based on this principle, electrical signals can be wirelessly transmitted between two coils. Wireless and passive means that there is no wire connection between the sensor and the controller (i.e., wireless), and no power supply is required at the sensor end (i.e., passive).

[0004] Based on the basic structure of the wireless passive sensor system in Figure 1, an extension wire with coils at both ends can be inserted between the controller coil and the sensor coil to further develop the structure shown in Figure 2.

[0005] Phased array ultrasonic testing is an advanced ultrasonic testing method applicable to medical imaging and industrial non-destructive testing. Conventional ultrasonic probes can only emit ultrasonic beams in a fixed direction, requiring the probe to be moved or rotated during testing to sweep the beam across the area being tested. In contrast, the beam emitted by a phased array probe can be controlled by circuitry, achieving focusing and scanning without moving the probe.

[0006] Phased array probes consist of an array of ordinary ultrasonic sensors, with each element independently emitting ultrasonic excitation signals and receiving echo signals according to a time set by the controller. Compared to conventional ultrasonic sensor-based detection technologies, existing phased array ultrasonic testing technologies offer advantages such as defect imaging, enabling defect localization, quantification, and characterization, and can also inspect complex and difficult-to-test specimens. However, existing phased array ultrasonic testing technologies also have the following drawbacks: 1. They require wires to connect the phased array probe and the controller, and the probe is relatively large. This necessitates that each inspection requires the operator to hold the phased array probe or use a scanner to scan the area to be tested, making inspections in narrow gaps and other confined spaces inconvenient. 2. During the inspection process, the location of the defect is unknown, and the surface of the area to be tested needs to be scanned with a phased array probe. This places high demands on the inspection speed. To address this, existing phased array controllers use multiple parallel channels to simultaneously transmit and receive signals from multiple array elements. For example, for an 8×8 phased array probe, there are 64 channels, requiring 64 parallel channel wires and controllers for control. The use of a large number of independently controlled channels makes phased array inspection equipment expensive and greatly increases calibration and maintenance costs. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a wireless passive ultrasonic sensor array monitoring system. Based on the principle of inductive coupling, three sets of coils are designed, namely sensor coil, transmitting coil and receiving coil, which are respectively connected to the ultrasonic sensor, the controller input terminal and the controller output terminal, realizing wireless passive operation of the sensor and improving detection efficiency. At the same time, the channels are set into an array of a certain scale, which can be applied to phased array ultrasonic detection.

[0008] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0009] A wireless passive ultrasonic sensor array monitoring system, comprising: a sensor module, a signal transmitting module, a signal receiving module, and a controller;

[0010] The sensor module includes a sensor end and a sensor coil end. An array of ultrasonic sensors is arranged on the sensor end, and an array of sensor coils is arranged on the sensor coil end. The ultrasonic sensor array and the sensor coil array are of the same size, and the ultrasonic sensors and sensor coils at corresponding positions are connected one by one.

[0011] The signal transmission module includes a transmitting coil end, on which an array of transmitting coils is arranged. The transmitting coil array and the sensor coil array are the same in size and arrangement, and correspond one-to-one in the vertical direction; the leads of each transmitting coil are connected to the controller.

[0012] The signal receiving module includes a receiving coil end, on which an array of receiving coils is arranged. The receiving coil array and the sensor coil array are the same in size and arrangement, and correspond one-to-one in the vertical direction; the leads of each receiving coil are connected to the controller.

[0013] A set of sensor coils, transmitting coils, and receiving coils corresponding in the vertical direction constitutes a channel, which is used to transmit or receive signals; the controller is used to generate excitation signals and collect echo signals.

[0014] Preferably, the outer diameter of the receiving coil is smaller than the inner diameter of the transmitting coil, or the outer diameter of the transmitting coil is smaller than the inner diameter of the receiving coil, so that the receiving coil and the transmitting coil do not overlap in the vertical direction.

[0015] Preferably, electromagnetic shielding material is attached to the side of the sensor coil facing the structure under test.

[0016] Preferably, the system also includes a temperature sensor for collecting temperature information and sending the temperature information to the controller; the controller is used to perform real-time sound velocity correction based on the temperature information.

[0017] Preferably, the sensor module, signal transmitting module, and signal receiving module all use non-metallic materials as the substrate.

[0018] Preferably, the leads of each transmitting coil of the signal transmitting module are led out through the transmitting lead-out terminal. The transmitting lead-out terminal is provided with a front transmitting pad and a back transmitting pad corresponding to the number of transmitting coils, respectively. The front and back leads of each transmitting coil are respectively connected to the respective front transmitting pad and the respective back transmitting pad. The leads of each receiving coil of the signal receiving module are led out through the receiving lead-out terminal. The receiving lead-out terminal is provided with a front receiving pad and a back receiving pad corresponding to the number of receiving coils, respectively. The front and back leads of each receiving coil are respectively connected to the respective front receiving pad and the respective back receiving pad.

[0019] Preferably, the controller employs phased array ultrasonic detection to generate excitation signals and acquire and analyze echo signals.

[0020] This invention also discloses a wireless passive ultrasonic sensor array monitoring method, which includes the following steps:

[0021] S1, attach and fix the sensor end of the sensor module to the surface of the structure to be tested;

[0022] S2, the sensor coil of the sensor module, the transmitting coil of the signal transmitting module, and the receiving coil of the signal receiving module are aligned vertically and placed close together; the leads of each transmitting coil and each receiving coil are connected to the controller.

[0023] The sensor coil array, transmitting coil array, and receiving coil array are all m×n in size, which means they constitute m×n channels.

[0024] S3, the controller generates an excitation signal according to a preset method and transmits it to the sensor coil through the transmitting coil. The sensor coil then excites the ultrasonic sensor to work and emit ultrasonic waves. The ultrasonic sensor then receives the echo signal and transmits it to the receiving coil through the sensor coil, thereby obtaining the echo signal.

[0025] Preferably, in step S3, the monitoring system uses a full matrix acquisition method to acquire signals, employing a 1-transmit, 1-receive mode. The controller selects one channel from m×n channels for signal transmission, and after signal transmission, selects another channel from m×n channels for signal reception. The ultrasonic sensor corresponding to the channel used for signal transmission is the transmitting element, and the ultrasonic sensor corresponding to the channel used for signal reception is the receiving element. The signal transmission circuit corresponding to the transmitting element and the signal reception circuit corresponding to the receiving element form a transmit-receive pair, totaling (m×n). 2 There are several transmit and receive pairs, thus collecting (m×n) data. 2 One echo signal.

[0026] Preferably, the data processing procedure is as follows:

[0027] S41, Before installation, the monitoring system conducts experiments to obtain and record system delay data at different temperatures;

[0028] S42, Obtain the initial wall thickness information of the structure to be measured and input it into the controller;

[0029] S43, determine the monitoring area and divide it into grids to form X×Y×Z focal points;

[0030] S44 records the sound velocity matrix at each focal point at each temperature; the sound velocity matrix includes the sound velocity of each transmit / receive pair.

[0031] S45, monitoring is performed according to the method in step S3. Within one monitoring cycle, after each transceiver pair completes one signal transmission and reception, the signal strength caused by that transmission and reception at each focal point is recorded; after completing (m×n) 2 After the signals of each transmit / receive pair are transmitted and received, each focal point receives (m×n) signals. 2 Each signal strength data point; the monitoring system uses (m×n) data obtained at each focal point. 2 The signal strength data are used to calculate the signal integral response, and the final signal strength at each focal point is obtained. The specific calculation process is as follows:

[0032] S451, Get the current temperature value;

[0033] S452, based on the recorded system delay data at different temperatures, obtain the system delay value t' at the current temperature;

[0034] S453, select a transmit / receive pair for one signal transmission and reception, where the transmit element is (R i ,R j ), R i R is the row number of the transmitting coil corresponding to the transmitting element on the array. j The column number of the transmitting coil corresponding to the transmitting element on the array; the receiving element is (T i ,T j ), T i T is the row number of the receiving coil corresponding to the receiving element on the array. j The column number of the receiving coil corresponding to the receiving element on the array, 1≤R i ,T i ≤m, 1≤R j ,T j ≤n;

[0035] S454, calculate the ultrasonic time of flight for each focal point during this signal transmission and reception process; wherein, the ultrasonic time of flight for focal point (x,y,z) is calculated as follows:

[0036] Based on the sound velocity matrices of each focus at various temperatures, the sound velocity matrix of the focus (x, y, z) at the current temperature is obtained through interpolation. Then, the sound velocity v(R) of the transceiver pair is retrieved from the sound velocity matrix of the focus (x, y, z) at the current temperature. i ,R j ,T i ,T j (x,y,z);

[0037] Ultrasonic flight time t(R) of focal point (x,y,z) i ,R j ,T i ,T j The formula for calculating t(R, x, y, z) is: i ,R j ,T i ,T j (x,y,z)=L(R) i ,R j ,T i ,T j ,x,y,z) / v(R i ,R j ,T i ,T j (x,y,z);

[0038] Among them, L(R)i ,R j ,T i ,T j (x, y, z) represents the ultrasonic emission array element (R) i ,R j The signal is emitted, passes through the focal point (x,y,z), and arrives at the receiving element (T). i ,T j The sound path lengths are: 1 ≤ x ≤ X, 1 ≤ y ≤ Y, 1 ≤ z ≤ Z;

[0039] S455, Calculate the signal intensity of each focal point based on the echo signals obtained from this signal transmission and reception; where, for focal point (x,y,z), the arrival time t of the echo signal is selected in the data segment of the echo signal according to the ultrasonic flight time of focal point (x,y,z). f Record time (t) f The signal strength of +t') is taken as the signal strength H(R) at the focus (x,y,z). i ,R j ,T i ,T j (x,y,z);

[0040] S456, Repeat steps S453-S455 until all transmit and receive pairs have completed signal transmission and reception, and each focal point has obtained (m×n). 2 Individual signal strength data;

[0041] S457, for each focal point (m×n) 2 The signal strength data are accumulated, and the signal integral response at each focus is calculated to obtain the final signal strength at each focus; where the final signal strength I(x,y,z) at focus (x,y,z) is:

[0042] S46 performs full-focus imaging, forming X×Y×Z pixels, and maps the final signal intensity of each focal point to the corresponding pixel value to generate a full-focus image.

[0043] The advantages of this invention are:

[0044] (1) Compared with existing phased array ultrasonic testing equipment, this invention designs three sets of coils based on the principle of inductive coupling, namely sensor coil, transmitting coil and receiving coil, which are respectively connected to ultrasonic sensor, controller output terminal and controller input terminal. Wireless signal and power transmission can be performed between sensor coil and transmitting / receiving coil, thereby realizing wireless passive operation of sensor. This design greatly simplifies the structure of sensor end, and there is no need to connect to power supply or design battery, which reduces the difficulty of explosion-proof design and avoids a series of fault risks caused by factors such as circuit sealing, circuit aging, battery replacement or charging, etc., and enhances the safety and stability of sensor end; at the same time, due to wireless connection, it is only necessary to align and approach each other between coils to complete the acquisition of ultrasonic sensor echo signal, which improves detection efficiency.

[0045] (2) Compared with existing wireless passive sensors, the present invention sets the channel into an array of a certain size, specifically an ultrasonic sensor array of an m×n size, which is applicable to phased array ultrasonic detection. Combining phased array technology and imaging algorithms, it can not only achieve more accurate thickness measurement through mutual transmission and verification between multiple array elements, but also realize the defect imaging function of the ultrasonic sensor array attachment area, covering the monitoring needs of cracks, pinhole corrosion and other non-uniform defects, thus broadening the application field of wireless passive sensors.

[0046] (3) The receiving coil and the transmitting coil do not overlap in the vertical direction, reducing mutual interference during signal transmission and reception.

[0047] (4) Attaching a layer of electromagnetic shielding material to the reverse side of the sensor coil can suppress the eddy currents caused by the current in the sensor coil in the metal when detecting metal structures, reduce energy loss and improve the signal-to-noise ratio.

[0048] (5) The sensor module uses a non-metallic material as the substrate, which can avoid the eddy currents in the substrate material caused by the AC current in the sensor coil during signal transmission and reception, thus avoiding energy loss. It also reduces the risk of short circuits in the connecting wires, ultrasonic sensors, and sensor coil circuits. Furthermore, a thin film material can be used as the substrate, which can be bent within a certain range and better fit the surface of the structure under test. Specifically, a PI film can be used as the substrate.

[0049] (6) The signal transmitting module and the signal receiving module are made of non-metallic material substrates, which can avoid the eddy currents in the substrate material caused by the AC current in the transmitting coil / receiving coil during the signal transmission and reception process, resulting in energy loss or electromagnetic shielding effect.

[0050] (7) The sensor coil and the transmitting / receiving coil can work with a certain obstacle between them. Therefore, the sensor end can be pre-installed under the wrapping layer of the surface of the structure to be tested, which can avoid long-term disassembly and reassembly of the outer wrapping layer for testing, saving testing costs. At the same time, the position of the sensor end does not change after installation, and fixed-point monitoring can be performed.

[0051] (8) Compared with existing phased array monitoring methods, the present invention can be installed on the surface of the structure under test for continuous phased array monitoring. According to the application requirements of online monitoring, the speed of a single detection is not limited. Therefore, a channel switching circuit can be used to measure the transmit and receive signals of only one transmit and receive pair each time, reducing the number of controller channels, reducing the complexity of the equipment, and reducing costs.

[0052] (9) Compared with ordinary wired sensors, the wireless passive ultrasonic sensor array monitoring system of the present invention has the following main advantages: 1. The monitoring device, consisting of a signal transmitting module, a signal receiving module, and a controller, does not require a wire connection with the sensor end. Furthermore, since electromagnetic fields can penetrate most non-metallic materials, detection can be performed between the sensor and the monitoring device through a layer or other structure, making it applicable to situations where conventional detection equipment cannot directly detect. 2. The sensor end does not require a power supply, greatly simplifying its structure and avoiding various malfunctions and risks caused by batteries. 3. The sensor end has a simple structure, is easy to seal, and is suitable for operation in humid environments or even underwater. Attached Figure Description

[0053] Figure 1 shows the basic structure of a wireless passive sensor system based on inductive coupling in the prior art.

[0054] Figure 2 shows the basic structure of a wireless passive sensor system based on inductive coupling in the prior art.

[0055] Figure 3 is a structural diagram of a wireless passive ultrasonic sensor array monitoring system according to the present invention.

[0056] Figure 4 is a front view of the sensor module.

[0057] Figure 5 is a reverse view of the sensor module.

[0058] Figure 6 is a front view of the signal transmission module.

[0059] Figure 7 is a schematic diagram of the reverse side of the signal transmission module.

[0060] Figure 8 is a front view of the signal receiving module.

[0061] Figure 9 is a reverse view of the signal receiving module.

[0062] Figure 10 is a schematic diagram of the installation of a wireless passive ultrasonic sensor array monitoring system according to the present invention.

[0063] Figure 11 shows the full-focus image obtained in Example 4; where (a) is the initial (first detection) full-focus image, (b) is the full-focus image obtained after 1 year, and (c) is the processed image obtained by subtraction using the baseline method.

[0064] Explanation of reference numerals in the attached diagram: 1-Sensor module, 2-Signal transmitting module, 3-Signal receiving module, 4-Controller, 5-Wrapping layer, 6-Structure under test; 11-Sensor end, 111-Ultrasonic end through-hole, 112-Ultrasonic front lead, 113-Ultrasonic sensor, 114-Ultrasonic back lead, 12-First connector, 121-First front connecting wire, 122-First back connecting wire, 13-Sensor coil end, 131-Sensor coil, 132-Sensor front lead, 133-Sensor end through-hole, 134-Sensor back lead; 21-Transmitting coil end, 211-Transmitting coil, 212-Transmitting front lead, 213-Transmitting end through-hole, 214- 22-Second connector, 221-Second front connector, 222-Second reverse connector, 23-Emitter lead, 231-Front emitter pad lead, 232-Front emitter pad, 233-Reverse emitter pad lead, 234-Reverse emitter pad; 31-Receiver coil end, 311-Receiver coil, 312-Receiver front lead, 313-Receiver end via, 314-Receiver reverse lead, 32-Third connector, 321-Third front connector, 322-Third reverse connector, 33-Receiver lead, 331-Front receive pad lead, 332-Front receive pad, 333-Reverse receive pad lead, 334-Reverse receive pad. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Example 1

[0067] As shown in Figure 3, the wireless passive ultrasonic sensor array monitoring system of the present invention includes: a sensor module 1, a signal transmitting module 2, a signal receiving module 3, and a controller 4. The sensor module 1, signal transmitting module 2, and signal receiving module 3 are all thin-film structures. The controller 4 generates excitation signals and acquires, records, and analyzes echo signals. The controller 4 can be assembled from commercially available phased array ultrasonic boards and channel switching circuits.

[0068] As shown in Figures 4 and 5, sensor module 1 includes a sensor end 11 and a sensor coil end 13. An array of ultrasonic sensors 113 is arranged on sensor end 11, and an array of sensor coils 131 is arranged on sensor coil end 13. The array of ultrasonic sensors 113 and the array of sensor coils 131 have the same size, and the array elements at corresponding positions are connected one-to-one. A 4×4 array is used as an example in the figures. The specific connection method is as follows: the sensor end 11 and the sensor coil end 13 are connected through the first connector 12. Each ultrasonic sensor 113 and each sensor coil 131 in the ultrasonic sensor array and sensor coil array has two leads. The two leads are respectively arranged on the front and back sides of the sensor module 1. The ultrasonic front lead 112 of the ultrasonic sensor 113 is connected to the sensing front lead 132 of the sensor coil 131 through the first front connecting line 121. The ultrasonic back lead 114 of the ultrasonic sensor 113 is connected to the sensing back lead 134 of the sensor coil 131 through the first back connecting line 122. The sensor end 11 is provided with an ultrasonic end through hole 111 for the ultrasonic front lead 112 or ultrasonic back lead 114 of the ultrasonic sensor 113 to pass through. The sensor coil end 13 is provided with a sensing end through hole 133 for the sensing front lead 132 or sensing back lead 134 of the sensor coil 131 to pass through. The first connector 12 includes a first front connecting line 121 and a first back connecting line 122.

[0069] As shown in Figures 6 and 7, the signal transmitting module 2 includes a transmitting coil end 21 and a transmitting lead end 23. An array of transmitting coils 211 is arranged on the transmitting coil end 21. The array size of the transmitting coils 211 is the same as that of the sensor coils 131, and they are arranged in the same way, i.e., at the same intervals. A set of pads is arranged on both the front and back sides of the transmitting lead end 23, namely a front transmitting pad 232 and a back transmitting pad 234. The transmitting coil end 21 and the transmitting lead end 23 are connected by a second connector 22. The number of transmitting coils 211 on the front transmitting pad 232 and the number of back transmitting pads 234 are the same. Each transmitting coil 211 has two leads, a front transmitting lead 212 and a back transmitting lead 214, for connecting to the front transmitting pad 232 and the back transmitting pad 234. The pads 234 are correspondingly connected. The front-side lead 212 of the transmitting coil 211 is connected to the front-side lead 231 of the front-side transmitting pad 232 via the second front-side connecting line 221. The back-side lead 214 of the transmitting coil 211 is connected to the back-side lead 233 of the back-side transmitting pad 234 via the second back-side connecting line 222. The transmitting coil end 21 is provided with a transmitting end through hole 213 for the front-side lead 212 or the back-side lead 214 of the transmitting coil 211 to pass through. The second connector 22 includes the second front-side connecting line 221 and the second back-side connecting line 222.

[0070] As shown in Figures 8 and 9, the signal receiving module 3 and the signal transmitting module 2 have the same overall structure. The signal receiving module 3 includes a receiving coil end 31 and a receiving lead-out end 33. The difference between the signal receiving module 3 and the signal transmitting module 2 is that the specifications (diameter and number of turns) of the receiving coil 311 on the receiving coil end 31 of the signal receiving module 3 are different from those of the transmitting coil 211, while the rest of the arrangement is the same. The center positions of the receiving coil 311 and the transmitting coil 211 correspond one-to-one. Specifically, an array of receiving coils 311 is arranged on the receiving coil end 31. The array size of the receiving coils 311 is the same as the array size of the sensor coils 131, and they are arranged in the same way, i.e., at the same intervals. The receiving lead-out terminal 33 has a set of pads on both its front and back sides, namely a front receiving pad 332 and a back receiving pad 334. The receiving coil terminal 31 is connected to the receiving lead-out terminal 33 via a third connector 32. The number of receiving coils 311 is the same as the number of front receiving pads 332 and back receiving pads 334. Each receiving coil 311 has two leads, one on the front side and one on the back side, for connecting to the front receiving pad 332 and the back receiving pad 334. The pads 334 are correspondingly connected. The receiving front lead 312 of the receiving coil 311 is connected to the front receiving pad lead 331 of the front receiving pad 332 via the third front connecting line 321. The receiving back lead 314 of the receiving coil 311 is connected to the back receiving pad lead 333 of the back receiving pad 334 via the third back connecting line 322. The receiving coil end 31 is provided with a receiving end through hole 313 for the receiving front lead 312 or the receiving back lead 314 of the receiving coil 311 to pass through. The third connector 32 includes the third front connecting line 321 and the third back connecting line 322.

[0071] As shown in Figure 3, the installation method of the system of the present invention is to attach the sensor module 1 to the surface of the structure 6 to be tested, and stack the signal receiving module 3 and the signal transmitting module 2 together, which are connected to the controller 4. The positions of the signal receiving module 3 and the signal transmitting module 2 can be interchanged. The sensor coil end 13 of the sensor module 1, the transmitting coil end 21 of the signal transmitting module 2, and the receiving coil end 31 of the signal receiving module 3 are close to each other, and the centers of corresponding sets of sensor coils 131, transmitting coils 211, and receiving coils 311 in the vertical direction are aligned as closely as possible in the vertical direction, thus enabling ultrasonic testing of the structure 6 to be tested. In the working state, a wrapping layer 5 of a certain thickness can be placed between the sensor module 1 and the signal transmitting module 2 or the signal receiving module 3 to achieve ultrasonic testing through the wrapping layer 5.

[0072] The array size of the ultrasonic sensor 113, the transmitting coil 211, and the receiving coil 311 is m×n.

[0073] The outer diameter of the receiving coil 311 is smaller than the inner diameter of the transmitting coil 211, or the outer diameter of the transmitting coil 211 is smaller than the inner diameter of the receiving coil 311, to ensure that the receiving coil 311 and the transmitting coil 211 do not overlap in the vertical direction, thereby reducing mutual interference during signal transmission and reception. In this embodiment, the outer diameter of the receiving coil 311 is smaller than the inner diameter of the transmitting coil 211.

[0074] The wires (leads, connecting wires) of sensor module 1, signal transmitting module 2 and signal receiving module 3 are staggered on the front and back sides to avoid overlap, which reduces the processing difficulty and improves the reliability of the device structure.

[0075] A temperature sensor can be added to the sensor end 11 of sensor module 1 to collect temperature information and send it to controller 4. The monitoring system performs real-time sound velocity correction based on the temperature information to improve detection accuracy. Alternatively, a temperature sensor can be placed on the surface of the structure under test 6 or the surface of the wrapping layer. A thermistor can be used to measure temperature, as changes in temperature cause changes in resistance.

[0076] An electromagnetic shielding material is attached to the side of the sensor coil 13 facing the structure under test 6. This can suppress the eddy currents caused by the current in the sensor coil 131 within the metal when detecting the metal structure, thereby reducing energy loss and improving the signal-to-noise ratio.

[0077] The sensor module 1 uses a non-metallic material as its substrate, which avoids eddy currents in the substrate material caused by the alternating current in the sensor coil 131 during signal transmission and reception, thus preventing energy loss. It also reduces the risk of short circuits in the first connector 12, the ultrasonic sensor 113, and the sensor coil 131 circuit. Furthermore, a thin film material can be used as the substrate, allowing for bending within a certain range and better fitting to the surface of the structure under test 6, such as the cylindrical outer wall of a pressure vessel or pressure pipeline. Specifically, a PI thin film can be used as the substrate, and the connecting lines and sensor coil 131 can be fabricated using flexible printed circuit board (FPC) technology. A relatively thin ultrasonic sensor 113 is used to fabricate an m×n scale ultrasonic sensor array, such as a piezoelectric crystal transducer, a capacitive micromechanical ultrasonic transducer, or a piezoelectric micromechanical ultrasonic transducer. This ensures that the overall thickness of the sensor module 1 is small, enabling it to operate normally under various encapsulation layers 5 without affecting the closure of the encapsulation layer 5 or causing stress concentration in the outer layer.

[0078] The signal transmitting module 2 and the signal receiving module 3 are made of non-metallic material substrates, which can avoid eddy currents in the substrate material caused by the alternating current in the coil during signal transmission and reception, thus preventing energy loss or electromagnetic shielding effects. The vertical positions of the signal transmitting module 2 and the signal receiving module 3 can be interchanged without affecting the monitoring process.

[0079] The signal transmitting module 2, the signal receiving module 3, and the controller 4 are combined to form a monitoring device. The controller 4 has a battery installed inside or is connected to a power source. The circuit of the signal transmitting module 2 is led out through the front transmitting pad 232 and the back transmitting pad 234 of the transmitting lead 23. Similarly, the circuit of the signal receiving module 3 is led out through the front receiving pad 3232 and the back receiving pad 334 of the receiving lead 33.

[0080] A set of sensor coils 131, transmitting coil 211 and receiving coil 311 corresponding in the vertical direction constitutes a channel. The channel can be used to transmit or receive signals, and finally constitutes m×n channels.

[0081] Furthermore, there are alternative installation methods for sensor module 1: When installing sensor module 1, the sensor end 11 needs to be tightly attached to the surface of the structure under test 6 and fixed in place to ensure good coupling between the interfaces, while the installation positions of the first connector 12 and the sensor coil end 13 can be changed. In some specific cases, the installation method shown in Figure 3 is difficult to meet the usage requirements. For example, if the thickness of the wrapping layer 5 is too large, the inductive coupling effect will decrease, the signal-to-noise ratio will decrease, and the detection effect will be affected; the wrapping layer 5 contains a conductive layer, which will also play an electromagnetic shielding role, reducing the inductive coupling power / signal transmission efficiency and making it difficult to obtain effective detection data. In this case, the first connector 12 can be extended out of the wrapping layer 5 as shown in Figure 10, and the sensor coil end 13 can be installed outside the wrapping layer 5. When performing ultrasonic detection, the coil ends of the signal transmitting module 2 and the signal receiving module 3 of the monitoring device can be tightly attached to the sensor coil end 13, and it is also easier to align the coils and improve the signal-to-noise ratio.

[0082] Furthermore, there are alternative designs for the coils (sensor coil 131, transmitting coil 211, and receiving coil 311): the shape of the coils is not limited to a single-layer, single-turn spiral coil, but can be multi-turn or multi-layer, and the shape can be square or polygonal; the coil arrangement is not limited to the arrangement shown in Figure 4, but can be arranged horizontally, spaced apart, etc. For example, the coils can be designed as cones, with m×n conical recesses formed at the sensor coil end 13, and correspondingly, m×n conical protrusions formed at corresponding positions at the transmitting coil end 21 and the receiving coil end 31. This design not only improves the coupling effect between the coils, but also facilitates the center alignment between the coils, thereby improving the detection accuracy.

[0083] The controller 4 employs phased array ultrasonic detection to generate excitation signals and acquire and analyze echo signals. The controller 4 generates excitation signals according to a preset method, which are transmitted from the transmitting coil 211 of the signal transmitting module 2 to the sensor coil 131 of the sensor module 1. The sensor coil 131 then excites the ultrasonic sensor 113 to emit ultrasonic waves. The ultrasonic sensor 113 receives the echo signals and transmits them via the sensor coil 131 to the receiving coil 311 of the signal receiving module 3, thus obtaining the echo signals.

[0084] Example 2

[0085] Based on the monitoring system of Embodiment 1, the present invention provides a wireless passive ultrasonic sensor array monitoring method, comprising the following steps:

[0086] S1. Attach and fix the sensor module 1 to the surface of the structure 6 to be measured. For structures with a protective layer equivalent to a wrapping layer 5, the wrapping layer 5 should be removed before installation, or the sensor module 1 can be pre-embedded during the structure manufacturing process before processing the outer wrapping layer 5. Before installation, the surface of the structure 6 to be measured should be smoothed using methods such as grinding. Then, use coupling agent, adhesive, and strapping to firmly and evenly fix the sensor module 1 to the position to be measured. All ultrasonic sensors 113 at the sensor end 11 must have good coupling with the surface of the structure 6 to be measured. After the sensor module 1 is installed, it should not be moved to ensure that the position for each ultrasonic test is completely fixed.

[0087] S2, fix the monitoring device, consisting of signal transmitting module 2, signal receiving module 3, and controller 4, in a suitable position. Specifically, the sensor coil 131 of sensor module 1, the transmitting coil 211 of signal transmitting module 2, and the receiving coil 311 of signal receiving module 3 are vertically aligned and close together; the leads of each transmitting coil 211 and each receiving coil 311 are connected to controller 4. Controller 4 should be equipped with a battery or connected to a power source to enable long-term monitoring.

[0088] Among them, the sensor coil 131 array, the transmitting coil 211 array, and the receiving coil 311 array are all m×n in size, forming m×n channels.

[0089] S3, damage monitoring is performed. The monitoring device can be controlled by relevant personnel. The initial thickness of the structure under test 6, the sound velocity matrix, the detection method and the monitoring cycle are preset. The controller 4 generates an excitation signal according to the preset method and transmits it to the sensor coil 131 through the transmitting coil 211. The ultrasonic sensor 113 is excited to work by emitting ultrasonic waves through the sensor coil 131. The ultrasonic sensor 113 then receives the echo signal and transmits it to the receiving coil 311 through the sensor coil 131, thereby obtaining the echo signal and performing analysis.

[0090] In this embodiment, the monitoring system uses the Full Matrix Acquisition (FMC) method to acquire signals, ultimately achieving Total Focusing Motion (TFM) imaging. Since the application scenario in this embodiment is primarily long-term monitoring of structural damage and defects, the extended time of a single detection has minimal impact on the long-term monitoring effect. Therefore, a one-to-one transmit / receive mode can be used for detection, meaning that only one channel is selected from the m×n channels for either transmission or reception each time, reducing costs. The controller 4 selects one channel from the m×n channels for signal transmission. After signal transmission, it selects another channel from the m×n channels for signal reception. The ultrasonic sensor 113 in the channel used for signal transmission is the transmitting element, and the ultrasonic sensor 113 in the channel used for signal reception is the receiving element. The signal transmission circuit corresponding to the transmitting element and the signal reception circuit corresponding to the receiving element constitute a transmit / receive pair, totaling (m×n). 2 Each transmit / receive pair is processed repeatedly until all transmit / receive pairs are sequentially activated, thus collecting (m×n) data. 2 One echo signal.

[0091] Furthermore, there are alternative detection methods: the number of channels selected is not limited to 1 / (m×n). For example, 2 / (m×n) channels can be set. Each time a signal is received, two channels are selected from the m×n channels. After one transmitting coil transmits a signal, the two receiving coils detect the echo signal simultaneously. This can improve the efficiency of a single detection. The more channels there are, the faster the single detection speed.

[0092] Example 3

[0093] Based on Examples 1-2, the data processing procedure for echo signals in the wireless passive ultrasonic sensor array monitoring system of the present invention is as follows:

[0094] S41. Before installation, the monitoring system conducts experiments to obtain and record system delay data at different temperatures.

[0095] S42, obtain the initial wall thickness of the monitored object, i.e., the structure to be measured 6, and input it into the controller 4.

[0096] S43, based on the detection conditions, select the region of interest within the area where the phased array probe, i.e., the sensor end 11, can generate sufficient sound pressure, and at the same time, reasonably divide the grid to form X×Y×Z focal points.

[0097] S44 records the sound velocity matrix at each focal point at each temperature; the sound velocity matrix includes the sound velocity of each transmit / receive pair.

[0098] A short time range is set, within which the wall thickness of the structure under test 6 is considered not to have changed significantly. A temperature sensor is installed in sensor module 1 or controller 4 to measure the temperature simultaneously. When the temperature changes due to factors such as day and night temperature and equipment operation, the sound velocity matrix is ​​calculated and recorded.

[0099] The purpose of recording the sound velocity matrix at each focal point at different temperatures is as follows: During monitoring, temperature changes affect the ultrasonic velocity, which in turn leads to changes in TFM imaging. Furthermore, for monitoring objects with heterogeneous structures, such as weld seams, the sound velocity varies in different directions, potentially causing misjudgments. Since the focal point position remains unchanged during long-term monitoring, and the correspondence between sound velocity and angle at a specific point on the structure under test (6) remains unchanged at a constant temperature, the sound velocity matrix at each focal point at each temperature can be pre-recorded. This matrix can then be directly retrieved or interpolated to obtain the sound velocity matrix at the current temperature during subsequent data processing.

[0100] The method for calculating the sound velocity corresponding to the angle is as follows: The group velocity distribution at small angles is obtained using the bottom reflection method (BRM), and the group velocity distribution at large angles is extrapolated and predicted using the Christoffel equation to form the sound velocity matrix for a single focus. This process is repeated until a sound velocity matrix with X×Y×Z focuses is formed. Specifically:

[0101] The sound velocity distribution v(θ) at small angles is obtained by the bottom reflection method, and its formula is: v(θ)=2h / (t θ ×cosθ);

[0102] Where h is the initial wall thickness of the structure 6 to be measured; t θ The time it takes for the echo reflected from the bottom surface (i.e., the surface of the structure under test 6 opposite to the surface of the ultrasonic sensor) to reach the receiving element when the incident angle is θ; θ is the incident angle; θ = arctan(Δ×p / 2h);

[0103] Where p is the array pitch; Δ is the distance between the transmitting element and the receiving element;

[0104] Among them, the transmitting array element is (R i ,R j ), R i R is the row number of the transmitting coil 211 corresponding to the transmitting element on the array. j The column number of the transmitting coil 211 corresponding to the transmitting element on the array; the receiving element is (T i ,T j ), T i T is the row number of the receiving coil 311 corresponding to the receiving array element on the array. jThe column number of the receiving coil 311 corresponding to the receiving array element on the array, 1≤R i ,T i ≤m, 1≤R j ,T j ≤n;

[0105] Extrapolating the group velocity distribution in the large-angle direction using the Christoffel equation, we can solve for the sound velocity distribution v(θ) of the quasi-P-wave, as shown in the formula:

[0106] Where ρ is the material density; A and B are intermediate variables; A = C 11 cos 2 θ+C 33 sin 2 θ+C 44 B = (C 11 cos 2 θ+C 44 sin 2 θ)(C 11 sin 2 θ+C 44 cos 2 θ)-(C 13 +C 44 ) 2 sin 2 θcos 2 θ;

[0107] Among them, C 11 C 13 C 33 C 44 These are four independent elastic constants.

[0108] The sound velocity matrix forming a single focal point: each focal point will receive (m×n) 2 The echo signals of each transceiver pair can be obtained, and the beam angle of each transceiver pair at the focal point can be calculated based on the sensor's own position information. By deriving the sound velocity calculation formula corresponding to the angle, the actual sound velocity of each transceiver pair's beam can be obtained, with each focal point having a scale of (m×n). 2 The sound speed matrix.

[0109] S45, monitoring is performed according to the method described in Example 2 above. Within one monitoring cycle, after each transceiver pair completes one signal transmission and reception, the signal strength caused by that transmission and reception at each focal point is recorded; after completing (m×n) 2 After the signals of each transmit / receive pair are transmitted and received, each focal point receives (m×n) signals. 2 Each signal strength data point; the monitoring system uses (m×n) data obtained at each focal point. 2The signal intensity data are used to calculate the signal integral response, obtaining the final signal intensity at each focal point, which is then used for imaging in step S46; the specific calculation process is shown below:

[0110] S451 obtains the current temperature value through a temperature sensor.

[0111] S452, based on the recorded system delay data at different temperatures, obtain the system delay value t' at the current temperature value through interpolation.

[0112] S453, select a transmit / receive pair for one signal transmission and reception, where the transmit element is (R i ,R j ), the receiving array element is (T) i ,T j ).

[0113] S454, calculate the ultrasonic time of flight for each focal point during this signal transmission and reception process; wherein, the ultrasonic time of flight for focal point (x,y,z) is calculated as follows:

[0114] Based on the sound velocity matrices of each focus at various temperatures, the sound velocity matrix of the focus (x, y, z) at the current temperature is obtained through interpolation. Then, the corresponding sound velocity v(R) for the transceiver pair is retrieved from the sound velocity matrix of the focus (x, y, z) at the current temperature. i ,R j ,T i ,T j (x,y,z);

[0115] Ultrasonic flight time t(R) of focal point (x,y,z) i ,R j ,T i ,T j The formula for calculating t(R, x, y, z) is: i ,R j ,T i ,T j (x,y,z)=L(R) i ,R j ,T i ,T j ,x,y,z) / v(R i ,R j ,T i ,T j (x,y,z);

[0116] Among them, L(R) i ,R j ,T i ,T j (x, y, z) represents the ultrasonic emission array element (R) i ,Rj The signal is emitted, passes through the focal point (x,y,z), and arrives at the receiving element (T). i ,T j The sound path is 1≤x≤X, 1≤y≤Y, 1≤z≤Z.

[0117] S455, Calculate the signal intensity of each focal point based on the echo signals obtained from this signal transmission and reception; where, for focal point (x,y,z), the arrival time t of the echo signal is selected in the echo signal data segment based on the ultrasonic flight time of focal point (x,y,z). f Record this moment (t) f The signal strength of +t') is taken as the signal strength H(R) at the focus (x,y,z). i ,R j ,T i ,T j The formula for calculating (x, y, z) is:

[0118] Where h(t)Ri,Rj,Ti,Tj is the Hilbert transform of the ultrasonic A-scan echo signal.

[0119] S456, Repeat steps S453-S455 until all (m×n) are completed. 2 For each transmit / receive pair, the signals are transmitted and received, and each focal point receives (m×n) signals. 2 Signal strength data.

[0120] 4567, for each focus (m×n) 2 The signal strength data are accumulated, and the signal integral response at each focus is calculated to obtain the final signal strength at each focus; where the final signal strength I(x,y,z) at focus (x,y,z) is:

[0121] S46 performs full-focus imaging, forming X×Y×Z pixels, and maps the final signal intensity of each focal point to the corresponding pixel value to generate a full-focus image.

[0122] Furthermore, the imaging method of the monitoring system of the present invention is not limited to full-focus imaging. When the number of channels allows, it can perform all phased array single-point acquisition imaging methods such as sector scanning imaging, plane wave imaging, and wavenumber domain imaging.

[0123] In this embodiment, the baseline method can be used to remove inherent geometric features. After installing the monitoring system, a full-focus imaging is performed and recorded as the initial imaging data, representing the structural features before the defect occurs or develops. Subsequently, each full-focus imaging data is subtracted from the initial imaging data, retaining only the changed structural features, eliminating interference from inherent geometric features, and highlighting the defect location. During the a-th full-focus imaging, after subtraction using the baseline method, the intensity SI(a,x,y,z) at the focal point (x,y,z) is calculated as follows:

[0124] Where I(1,x,y,z) and I(a,x,y,z) are the final signal intensities obtained at the focal point (x,y,z) during the first and a-th full-focus imaging, respectively, and max(·) is the maximum value function.

[0125] Furthermore, there is an alternative to the baseline method: At defect-free locations, the bottom echo signal is strong; however, when a defect is present, the ultrasonic beam is blocked, weakening the signal at the bottom echo location. If the above calculation formula is used to subtract the values, the image intensity at the bottom echo location becomes negative; taking the absolute value then reveals an increase in image intensity at the bottom surface. Therefore, the following calculation method can be used as an alternative:

[0126] Where SI(a,x,y,z) is the final signal intensity obtained by subtracting the baseline at the focal point (x,y,z) during the a-th full-focus imaging.

[0127] Example 4

[0128] An 8×8 probe was used to monitor defects in the weld seam of an aluminum workpiece. The region of interest was set to 10mm×10mm×50mm, and a total of 71×71×357=1,799,637 focal points were selected. Taking the signal strength calculation at focal point (3,4,5) as an example:

[0129] The 8×8 probes are numbered. For the ultrasonic sensor in row a and column b, its number is 8×(a-1)+b. For example, the ultrasonic sensor in row 1 and column 2 is numbered 2, and the ultrasonic sensor in row 3 and column 4 is numbered 8×(3-1)+4=20. There are a total of 64 ultrasonic sensors, so the sound velocity matrix size is 64×64. When the monitoring system is first put into operation, based on the current temperature value of 9.2℃, two matrices recorded at 9.0℃ and 9.5℃ are selected from the sound velocity matrices of the focal point (3,4,5) at 25 temperature values. The sound velocity matrix of the focal point (3,4,5) at 9.2℃ is obtained by interpolation. The sound velocity matrix records the corresponding sound velocities of all transmit and receive pairs. For example, when ultrasonic sensor number 2 transmits and ultrasonic sensor number 20 receives, the value of row 2 and column 20 in the sound velocity matrix should be used to obtain the sound velocity value of 6150.3m / s. Based on the signal strength calculation formula, the signal strength H(1,2,3,4,3,4,5) at the focal point (3,4,5) is calculated to be 5.50 × 10⁻⁶. -3 After repeating the measurement 64×64 times, 4096 signal strength data points were obtained at the focal point (3,4,5). These data points were then summed according to the accumulation formula to obtain the final signal strength I(3,4,5) = 22.51 at the focal point (3,4,5).

[0130] From the intensity data of 1,799,637 focal points, the maximum value Imax(36,44,157) = 58.68 was selected. Based on this maximum value, the intensities of all focal points were normalized. For example, the normalized intensity of focal point (3,4,5) is:

[0131] The intensity of each focal point is mapped to the image color, forming 71×71×357=1799637 pixels, and finally a fully focused image is obtained, as shown in Figure 11(a).

[0132] One year later, a fully focused image was obtained using the same method, as shown in Figure 11(b). The processed image was obtained by baseline subtraction using the baseline method, as shown in Figure 11(c). It can be seen that the image after baseline subtraction suppressed the interference signal and highlighted the defect location.

[0133] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wireless passive ultrasonic sensor array monitoring system, characterized in that, The system includes: a sensor module (1), a signal transmitting module (2), a signal receiving module (3), and a controller (4); The sensor module (1) includes a sensor end (11) and a sensor coil end (13). An array of ultrasonic sensors (113) is arranged on the sensor end (11), and an array of sensor coils (131) is arranged on the sensor coil end (13). The ultrasonic sensor (113) array and the sensor coil (131) array are of the same size, and the ultrasonic sensors (113) and sensor coils (131) at corresponding positions are connected one by one. The signal transmitting module (2) includes a transmitting coil end (21), on which an array of transmitting coils (211) is arranged. The array of transmitting coils (211) and the array of sensor coils (131) are the same in size and arrangement, and correspond one-to-one in the vertical direction. The leads of each transmitting coil (211) are connected to the controller (4). The signal receiving module (3) includes a receiving coil end (31), and an array of receiving coils (311) is arranged on the receiving coil end (31). The array of receiving coils (311) and the array of sensor coils (131) are the same in size and arrangement, and correspond one-to-one in the vertical direction. The leads of each receiving coil (311) are connected to the controller (4). A set of sensor coils (131), transmitting coils (211) and receiving coils (311) corresponding in the vertical direction constitutes a channel, which is used to transmit or receive signals; the controller (4) is used to generate excitation signals and collect echo signals.

2. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, The outer diameter of the receiving coil (311) is smaller than the inner diameter of the transmitting coil (211), or the outer diameter of the transmitting coil (211) is smaller than the inner diameter of the receiving coil (311), so that the receiving coil (311) and the transmitting coil (211) do not overlap in the vertical direction.

3. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, Electromagnetic shielding material is attached to the side of the sensor coil end (13) facing the structure under test (6).

4. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, The system also includes a temperature sensor for collecting temperature information and sending the temperature information to the controller (4); the controller (4) is used to perform real-time sound velocity correction based on the temperature information.

5. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, The sensor module (1), signal transmitting module (2) and signal receiving module (3) all use non-metallic materials as substrates.

6. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, The leads of each transmitting coil (211) of the signal transmitting module (2) are led out through the transmitting lead-out terminal (23). The transmitting lead-out terminal (23) is provided with a front transmitting pad (232) and a back transmitting pad (234) corresponding to the number of transmitting coils (211). The front and back leads of each transmitting coil (211) are respectively connected to the front transmitting pad (232) and the back transmitting pad (234). The leads of each receiving coil (311) of the signal receiving module (3) are led out through the receiving lead-out terminal (33). The receiving lead-out terminal (33) is provided with a front receiving pad (332) and a back receiving pad (334) corresponding to the number of receiving coils (311). The front and back leads of each receiving coil (311) are respectively connected to the front receiving pad (332) and the back receiving pad (334).

7. The wireless passive ultrasonic sensor array monitoring system according to claim 1, characterized in that, The controller (4) uses phased array ultrasonic detection to generate excitation signals and collect and analyze echo signals.

8. A wireless passive ultrasonic sensor array monitoring method, characterized in that, A wireless passive ultrasonic sensor array monitoring system based on any one of claims 1-7, the method comprising the following steps: S1, attach and fix the sensor end (11) of the sensor module (1) to the surface of the structure to be tested (6); S2, the sensor coil (131) of the sensor module (1), the transmitting coil (211) of the signal transmitting module (2), and the receiving coil (311) of the signal receiving module (3) are aligned vertically and placed close together; the leads of each transmitting coil (211) and each receiving coil (311) are connected to the controller (4). Among them, the sensor coil (131) array, the transmitting coil (211) array and the receiving coil (311) array are all m×n in size, that is, they constitute m×n channels; S3, the controller (4) generates an excitation signal in a preset manner and transmits it to the sensor coil (131) via the transmitting coil (211). The sensor coil (131) excites the ultrasonic sensor (113) to work and emit ultrasonic waves. The ultrasonic sensor (113) then receives the echo signal and transmits it to the receiving coil (311) via the sensor coil (131), thereby obtaining the echo signal.

9. The wireless passive ultrasonic sensor array monitoring method according to claim 8, characterized in that, In step S3, the monitoring system uses a full matrix acquisition method to acquire signals, employing a 1-transmit, 1-receive mode. The controller (4) selects one channel from the m×n channels for transmitting signals. After signal transmission, it selects another channel from the m×n channels for receiving signals. The ultrasonic sensor (113) corresponding to the channel used for transmitting signals is the transmitting element, and the ultrasonic sensor (113) corresponding to the channel used for receiving signals is the receiving element. The signal transmission circuit corresponding to the transmitting element and the signal receiving circuit corresponding to the receiving element constitute a transceiver pair, totaling (m×n). 2 There are several transmit and receive pairs, thus collecting (m×n) data. 2 One echo signal.

10. The wireless passive ultrasonic sensor array monitoring method according to claim 9, characterized in that, The data processing procedure is as follows: S41, Before installation, the monitoring system conducts experiments to obtain and record system delay data at different temperatures; S42, obtain the initial wall thickness information of the structure to be tested (6) and input it into the controller (4); S43, determine the monitoring area and divide it into grids to form X×Y×Z focal points; S44 records the sound velocity matrix at each focal point at each temperature; the sound velocity matrix includes the sound velocity of each transmit / receive pair. S45, monitoring is performed according to the method in step S3. Within one monitoring cycle, after each transceiver pair completes one signal transmission and reception, the signal strength caused by that transmission and reception at each focal point is recorded; after completing (m×n) 2 After the signals of each transmit / receive pair are transmitted and received, each focal point receives (m×n) signals. 2 Individual signal strength data; The monitoring system uses (m×n) data obtained at each focal point. 2 The signal strength data are used to calculate the signal integral response, and the final signal strength at each focal point is obtained. The specific calculation process is as follows: S451, Get the current temperature value; S452, based on the recorded system delay data at different temperatures, obtain the system delay value t' at the current temperature; S453, select a transmit / receive pair for one signal transmission and reception, where the transmit element is (R i ,R j ), R i R is the row number of the transmitting coil (211) corresponding to the transmitting element on the array. j The column number of the transmitting coil (211) corresponding to the transmitting element on the array; the receiving element is (T i ,T j ), T i T is the row number of the receiving coil (311) corresponding to the receiving array element on the array. j The column number of the receiving coil (311) corresponding to the receiving element on the array, 1≤R i ,T i ≤m, 1≤R j ,T j ≤n; S454, calculate the ultrasonic time of flight for each focal point during this signal transmission and reception process; wherein, the ultrasonic time of flight for focal point (x,y,z) is calculated as follows: Based on the sound velocity matrices of each focus at various temperatures, the sound velocity matrix of the focus (x, y, z) at the current temperature is obtained through interpolation. Then, the sound velocity v(R) of the transceiver pair is retrieved from the sound velocity matrix of the focus (x, y, z) at the current temperature. i ,R j ,T i ,T j (x,y,z); Ultrasonic flight time t(R) of focal point (x,y,z) i ,R j ,T i ,T j The formula for calculating (x, y, z) is: t(R i ,R j ,T i ,T j ,x,y,z)=L(R i ,R j ,T i ,T j ,x,y,z) / v(R i ,R j ,T i ,T j ,x,y,z); Among them, L(R) i ,R j ,T i ,T j (x, y, z) represents the ultrasonic emission array element (R) i ,R j The signal is emitted, passes through the focal point (x,y,z), and arrives at the receiving element (T). i ,T j The sound path lengths are: 1 ≤ x ≤ X, 1 ≤ y ≤ Y, 1 ≤ z ≤ Z; S455, Calculate the signal intensity of each focal point based on the echo signals obtained from this signal transmission and reception; where, for focal point (x,y,z), the arrival time t of the echo signal is selected in the data segment of the echo signal according to the ultrasonic flight time of focal point (x,y,z). f Record time (t) f The signal strength of +t') is taken as the signal strength H(R) at the focus (x,y,z). i ,R j ,T i ,T j (x,y,z); S456, Repeat steps S453-S455 until all transmit and receive pairs have completed signal transmission and reception, and each focal point has obtained (m×n). 2 Individual signal strength data; S457, for each focal point (m×n) 2 The signal strength data are accumulated, and the signal integral response at each focus is calculated to obtain the final signal strength at each focus; where the final signal strength I(x,y,z) at focus (x,y,z) is: S46 performs full-focus imaging, forming X×Y×Z pixels, and maps the final signal intensity of each focal point to the corresponding pixel value to generate a full-focus image.

Images