Radio frequency detection system, crack and strain detection method thereof, and RFID tag

Abstract

The present invention relates to a radio frequency detection system, crack and strain detection method, and RFID tag. The RFID tag comprises a dielectric substrate and an antenna attached to the top surface of the dielectric substrate. Tag excitation circuits are provided in all four directions of the dielectric substrate. Each tag excitation circuit includes a radio frequency chip, a coupling loop, a side branch inductor, an interdigital capacitor, and a matching capacitor. The dielectric substrates include a first dielectric substrate, a second dielectric substrate, and a third dielectric substrate. By providing tag excitation circuits in all four directions of the dielectric substrate, the multi-directional detection RFID tag can detect cracks and strain changes in a metal sample in all four directions. This solves the technical problem that existing radio frequency identification technology can only detect the structural health of metal components from a single direction, resulting in relatively one-sided detection results.

Description

Technical Field

[0001] The present invention relates to the technical field of crack detection, and in particular to a radio frequency detection system and a crack and strain detection method and an RFID tag thereof. Background Art

[0002] With the booming development of industries such as aerospace technology, steel bridges, construction, and rail transportation, most of the metal components used in these industries are large structures. These large-scale metal components are often exposed to harsh extreme environmental conditions and frequent stress concentration for a long time. Over time, the probability of these metal components developing cracks will greatly increase. For these small cracks, if they are not discovered and repaired immediately, once they expand beyond a certain threshold, they will pose a serious threat to the safe operation of the metal structure, and even cause significant property losses and major safety accidents. Therefore, the importance of health monitoring technology for the metal components of these large structures is self-evident.

[0003] In the field of structural health testing of metal components, non-destructive testing technology is currently used to test the structure of metal components. Non-destructive testing technology refers to the use of changes in the physical properties of the object after damage relative to its physical properties in a healthy state to analyze and infer damage such as fatigue cracks and corrosion, without damaging the object being tested, and to make reliable assessments of this. Common high-resolution and high-sensitivity non-destructive testing technologies include ultrasonic testing, pulsed eddy current testing, and electromagnetic thermal imaging testing. These high-resolution and high-sensitivity non-destructive testing technologies are widely used in the evaluation of composite material properties and the internal quality of metal components. However, in engineering practice, these traditional monitoring methods often have certain limitations, such as complex wiring, high cost of monitoring equipment, and poor flexibility. Therefore, they are not suitable for long-term structural surface crack monitoring.

[0004] With the advancement of technology, radio frequency identification (RFID) has also been applied to the structural health monitoring of metal components. RFID, as a contactless automatic target identification and data transmission technology, consists of a backend data management system, a reader, and a tag antenna. RFID technology operates by transmitting a modulated RF signal and energy from the reader antenna, which is then received by the tag antenna. When the collected RF energy reaches the activation threshold power of the RFID chip in the tag antenna, the RFID chip activates, demodulating the modulated RF signal and responding according to the instructions contained in the modulated information. Simultaneously, the tag information from the tag antenna is reflected back to the reader through backscatter modulation, enabling contactless target identification and data transmission between the reader and the tag antenna. RFID technology offers advantages such as low deployment cost, long recognition range, and the ability to simultaneously identify multiple tags. It has been widely used in various industries, including logistics and transportation, traffic management, smart homes, and industrial control. However, current RFID technology can only monitor the structural health of metal components from a single direction, detecting cracks and strain in a specific direction of the object under test, resulting in inaccurate and fragmented results. Summary of the Invention

[0005] The embodiments of the present invention provide a radio frequency detection system and its crack and strain detection method and RFID tag, which are used to solve the technical problem that the existing radio frequency identification technology can only perform health detection on the structure of metal components from one direction, and the detection results are relatively one-sided.

[0006] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A multi-directional detection RFID tag includes a dielectric substrate and an antenna attached to the top surface of the dielectric substrate. Tag excitation circuits are provided in all four directions of the dielectric substrate. Each tag excitation circuit includes a radio frequency chip, a coupling loop, a side branch inductor, an interdigital capacitor, and a matching capacitor. The dielectric substrates include a first dielectric substrate, a second dielectric substrate, and a third dielectric substrate. The radio frequency chip and the matching capacitor are provided on the top surface of the first dielectric substrate. The coupling loop is provided on the bottom surface of the first dielectric substrate and the top surface of the second dielectric substrate. The radio frequency chip and the matching capacitor are connected to the coupling loop through a via hole in the first dielectric substrate. The interdigital capacitor is provided on the bottom surface of the second dielectric substrate and connected to the coupling loop through a via hole in the second dielectric substrate. The side branch inductor is connected to both ends of the interdigital capacitor.

[0008] Preferably, the first dielectric substrate and the second dielectric substrate, and the second dielectric substrate and the third dielectric substrate are fixedly bonded by a bonding agent.

[0009] The present invention also provides a radio frequency detection system, comprising an RFID tag, a reader for bidirectional communication with the RFID tag, and a controller for controlling the operation of the RFID tag and the reader. The RFID tag is the multi-directional detection RFID tag described above.

[0010] The present invention also provides a crack detection method for a radio frequency detection system, which is applied to the radio frequency detection system described above. The crack detection method comprises the following steps:

[0011] Placing an RFID tag on a first metal sample to be tested with a certain type of crack width known to obtain the crack width of the first metal sample to be tested, and using a reader of a radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain first resonant frequency data corresponding to the working feedback of each tag excitation circuit;

[0012] Determining the crack characteristic sensitivity and the first frequency difference corresponding to each tag excitation circuit according to the first resonant frequency data and the first reference frequency fed back by each tag excitation circuit, and determining the direction of the crack in the first metal sample to be tested according to the first frequency difference;

[0013] Placing an RFID tag on a second metal sample to be tested of a certain type with an unknown crack width, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining second resonant frequency data corresponding to the operating feedback of each tag excitation circuit;

[0014] Determining a second frequency difference based on the second resonant frequency data fed back by each tag excitation circuit and the first reference frequency, and determining a crack width of the second metal sample to be tested based on the crack characteristic sensitivity and the second frequency difference;

[0015] The first reference frequency is the resonant frequency of a certain type of metal sample in a healthy state.

[0016] Preferably, the crack detection method of the radio frequency detection system includes: determining the crack characteristic sensitivity and frequency difference corresponding to each tag excitation circuit based on the first resonant frequency data and the first reference frequency fed back by each tag excitation circuit, and using a crack characteristic relationship formula, the crack characteristic relationship formula is: S = Δf1 / H, Δf1 = |f1-f0|, where S is the crack characteristic sensitivity, Δf1 is the first frequency difference, f1 is the first resonant frequency data, f0 is the first reference frequency, and H is the crack width.

[0017] Preferably, the crack detection method of the radio frequency detection system includes: determining the crack width of the second metal sample to be tested based on the crack characteristic sensitivity and the second frequency difference, and determining the crack width of the second metal sample to be tested using an offset relationship formula, the offset relationship formula is: L = Δf2 / S, Δf2 = |f2-f0|, where S is the crack characteristic sensitivity of a certain type of metal sample, Δf2 is the second frequency difference, f2 is the second resonant frequency data, f0 is the first reference frequency, and L is the crack width of the second metal sample to be tested.

[0018] Preferably, in the process of controlling the operation of the tag excitation circuit in the RFID tag in turn by the radio frequency detection system and obtaining the resonant frequency data corresponding to the working feedback of each tag excitation circuit, the crack detection method of the radio frequency detection system includes: controlling the tag impedance of the RFID tag to be equal to the radio frequency chip impedance of the RFID tag by the radio frequency detection system.

[0019] The present invention further provides a strain detection method for a radio frequency detection system, which is applied to the radio frequency detection system described above. The strain detection method comprises the following steps:

[0020] Placing an RFID tag on a third type of metal sample to be tested with a known bending radius, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining first strain resonance frequency data corresponding to the operating feedback of each tag excitation circuit;

[0021] Determining the strain sensitivity and the first strain frequency difference corresponding to each tag excitation circuit based on the first strain resonance frequency data and the second reference frequency fed back by each tag excitation circuit, and determining the direction in which the third metal sample to be tested is strained based on the first strain frequency difference;

[0022] Placing an RFID tag on a fourth type of metal sample to be tested with an unknown bending radius, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining second strain resonance frequency data corresponding to the operating feedback of each tag excitation circuit;

[0023] Determining a second strain frequency difference corresponding to each tag excitation circuit based on the second strain resonance frequency data fed back by each tag excitation circuit and a second reference frequency, and determining a strain curvature of the fourth metal sample to be tested based on the strain sensitivity and the second strain frequency difference;

[0024] The second reference frequency is the resonant frequency of a certain type of metal sample in a healthy state.

[0025] Preferably, the strain detection method of the radio frequency detection system includes: determining the strain sensitivity and strain frequency difference corresponding to each tag excitation circuit based on the first strain resonance frequency data and the second reference frequency fed back by each tag excitation circuit, and using a strain variable relationship formula, the strain variable relationship formula is: Y = Δf1' / (1r), Δf1' = |f1'-f0'|, where Y is the strain variable sensitivity, Δf1' is the first strain frequency difference, f1' is the first strain resonance frequency data, f0' is the second reference frequency, and r is the bending radius.

[0026] Preferably, the strain detection method of the radio frequency detection system includes: determining the strain curvature of the fourth metal sample to be tested based on the strain sensitivity and the second strain frequency difference using a strain curvature relationship formula, wherein the strain curvature relationship formula is: K=Δf2' / Y, Δf2'=|f2'-f0'|, wherein Y is the strain sensitivity, Δf2' is the second strain frequency difference, K is the strain curvature of the fourth metal sample to be tested, f2' is the second strain resonance frequency data, and f0' is the second reference frequency.

[0027] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages: the radio frequency detection system, crack and strain detection method thereof, and RFID tag; the multi-directional detection RFID tag includes a dielectric substrate and an antenna attached to the top surface of the dielectric substrate; tag excitation circuits are provided in all four directions of the dielectric substrate; each tag excitation circuit includes a radio frequency chip, a coupling ring, a side-branch inductor, an interdigital capacitor, and a matching capacitor; the dielectric substrates include a first dielectric substrate, a second dielectric substrate, and a third dielectric substrate; the radio frequency chip and the matching capacitor are provided on the upper surface of the first dielectric substrate; the coupling ring is provided on the lower surface of the first dielectric substrate and the upper surface of the second dielectric substrate; the radio frequency chip and the matching capacitor are connected to the coupling ring through a via hole in the first dielectric substrate; the interdigital capacitor is provided on the lower surface of the second dielectric substrate; the interdigital capacitor is connected to the coupling ring through a via hole in the second dielectric substrate; and the two ends of the interdigital capacitor are connected to the side-branch inductor. This multi-directional detection RFID tag is equipped with tag excitation circuits in four directions of the dielectric substrate, so that the multi-directional detection RFID tag can detect cracks and strain changes in the metal sample to be tested in four directions, solving the technical problem that the existing radio frequency identification technology can only perform structural health detection of metal components from one direction, resulting in relatively one-sided detection results.

[0028] This radio frequency detection system uses RFID tags with four-directional detection capabilities to achieve real-time detection of metal components, passive operation, and low cost, and can also detect multi-directional crack characteristics and strains.

[0029] The crack detection method of the radio frequency detection system realizes crack detection of the metal sample to be tested through the radio frequency detection system. It can detect the direction of crack occurrence, providing a basis for preventing the crack from further deteriorating and repairing the metal sample to be tested; it can also detect the width of the crack of the metal sample to be tested, providing data for studying the changes in the crack of the metal sample to be tested, and realizing the diversification of the crack information of the metal sample to be tested.

[0030] The RF detection system uses information from the RF chip on the RFID tag in four directions to detect and acquire data from the metal sample under test. By comparing each acquired data with the reference frequency of each matching circuit in a healthy state, it can determine which matching circuit the RF chip is located in, thereby determining the direction of the crack and strain. The corresponding crack width and strain curvature are then analyzed based on the data obtained on the crack and strain direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the top view of the multi-directional detection RFID tag according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the exploded structure of the multi-directional detection RFID tag according to an embodiment of the present invention;

[0034] Figure 3 This is a structural diagram of the interdigital capacitance and side-branch inductance of each tag excitation circuit in the multi-directional detection RFID tag according to an embodiment of the present invention;

[0035] Figure 4 This is a diagram showing an equivalent model of interdigital capacitance and side-branch inductance of each tag excitation circuit in a multi-directional detection RFID tag according to an embodiment of the present invention;

[0036] Figure 5 This is a framework diagram of a radio frequency detection system according to an embodiment of the present invention;

[0037] Figure 6 This is a framework diagram of a reader in a radio frequency detection system according to an embodiment of the present invention;

[0038] Figure 7 A flowchart of the steps of a crack detection method of a radio frequency detection system according to an embodiment of the present invention;

[0039] Figure 8 A comparison diagram of resonant frequencies in a crack detection method of a radio frequency detection system according to an embodiment of the present invention;

[0040] Figure 9 This is a flowchart of the steps of the strain detection method of the radio frequency detection system according to an embodiment of the present invention;

[0041] Figure 10 This is a comparison diagram of the resonant frequencies in the strain detection method of the radio frequency detection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0047] The embodiments of the present application provide a radio frequency detection system and its crack and strain detection method and RFID tag, which are used to solve the technical problem that the existing radio frequency identification technology can only perform health detection on the structure of metal components from one direction, and the detection results are relatively one-sided.

[0048] Example 1:

[0049] Figure 1 This is a schematic diagram of the top view of the multi-directional detection RFID tag according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the exploded structure of the multi-directional detection RFID tag according to an embodiment of the present invention.

[0050] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides an RFID tag with multi-directional detection, including a dielectric substrate 1 and an antenna 2 attached to the top surface of the dielectric substrate. Tag excitation circuits are provided on all four sides of the dielectric substrate 1. Each tag excitation circuit includes a radio frequency chip 5, a coupling loop 3, a side branch inductor 7, an interdigital capacitor 4, and a matching capacitor 6. The dielectric substrate 1 includes a first dielectric substrate 11, a second dielectric substrate 12, and a third dielectric substrate 13. The radio frequency chip 5 and the matching capacitor 6 are provided on the upper surface of the first dielectric substrate 11. The coupling loop 3 is provided on the lower surface of the first dielectric substrate 11 and the upper surface of the second dielectric substrate 12. The radio frequency chip 5 and the matching capacitor 6 are connected to the coupling loop 3 through a via hole in the first dielectric substrate 11. The interdigital capacitor 4 is provided on the lower surface of the second dielectric substrate 12 and connected to the coupling loop 3 through a via hole in the second dielectric substrate 12. The side branch inductor 7 is connected to both ends of the interdigital capacitor 4.

[0051] like Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the dielectric substrate 1 is a low-profile substrate made of a flexible material, so that the dielectric substrate 1 is thin, so that the dielectric substrate 1 can better fit the metal sample to be tested and can better adapt to the strain of the metal sample to be tested.

[0052] like Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the antenna 2 can be selected as a patch antenna.

[0053] It should be noted that antenna 2 can be used to communicate with the reader corresponding to the multi-directional detection RFID tag. In this embodiment, when the reader emits a detection / energy signal, antenna 2 (passive) receives the detection / energy signal and rectifies a portion of it into DC power to power the circuitry within the multi-directional detection RFID tag. The remaining energy signal is modulated by the data stored in the multi-directional detection RFID tag and then reflected back to the reader.

[0054] In an embodiment of the present invention, when the antenna 2 of the multi-directional detection RFID tag receives a signal from the reader, the coupling ring 3 will couple the signal into the coupling ring 3, and the signal in the coupling ring 3 will flow into the RF chip 5 and the interdigital capacitor 4, providing energy and signal to the RF chip 5.

[0055] In an embodiment of the present invention, the interdigital capacitor 4 is an ideal device for making a surface sensor due to its unique planar electrode structure and surface space electric field. The electric field between the positive and negative electrodes of the interdigital capacitor 4 is distributed in the surface space above and below the electrode plane. When the dielectric constant of the surface above and below the electrode plane changes, the capacitance value of the interdigital capacitor 4 will cause a change.

[0056] It should be noted that when the metal sample to be tested is in a healthy state, the RF chip 5 and the matching circuit composed of the interdigital capacitors 4 and the coupling loop 3 are impedance-matched. At a certain frequency, the power reflection coefficient Γ corresponding to the RF chip 5 is minimized. At this time, the response frequency read by the reader corresponding to the multi-directional detection RFID tag is the resonant frequency of the multi-directional detection RFID tag. The sensing performance of the multi-directional detection RFID tag is strongest at the resonant frequency. When a crack appears in the metal sample to be tested, the dielectric constant of the air in the crack changes relative to the healthy metal sample, causing the capacitance value of the interdigital capacitors 4 to change. The impedance of the matching circuit also changes, and the resonant frequency of the tag read by the reader corresponding to the multi-directional detection RFID tag also changes accordingly. Therefore, using this multi-directional detection RFID tag, it is possible to establish a relationship between crack characteristics such as crack width and depth and the tag resonant frequency. Through multiple tests, a relationship between crack width, depth, and frequency is obtained. The corresponding crack characteristics can be deduced from this relationship and the resonant frequency of the multi-directional detection RFID tag read by the reader. By designing and adjusting the sizes of various parts of the tag excitation circuit (such as the sizes of the coupling loop 3, the side inductor 7, the interdigital capacitor 4 and the matching capacitor 6), the impedance of the multi-directional detection RFID tag is matched with the radio frequency chip.

[0057] Figure 3 This is a structural diagram of the interdigital capacitance and side-branch inductance of each tag excitation circuit in the multi-directional detection RFID tag according to an embodiment of the present invention. Figure 4This is a diagram of the equivalent model of the interdigital capacitance and side-branch inductance of each tag excitation circuit in the multi-directional detection RFID tag according to an embodiment of the present invention.

[0058] like Figure 3 As shown, in the embodiment of the present invention, both ends of the interdigital capacitor 4 are connected to a side inductor 7 .

[0059] It should be noted that if Figure 4 As shown, They are the series branch capacitance and inductance of the equivalent model, the parallel branch capacitance of the equivalent model, the series branch inductance of the equivalent model, and the parallel branch inductance and capacitance of the equivalent model. int 、Y int 、Z stub 、Y stub They are the impedance and admittance of the interdigital capacitor and the impedance and admittance of the side inductor respectively. And Z derived from formula 2 to formula 5 and π-type and T-type network circuit models int 、Y int 、Z stub 、Y stub , Formula 6 and Formula 7 are the Y parameter of the interdigital capacitance and the Z parameter of the side-branch inductance respectively. In this embodiment, the power reflection coefficient Γ of the multi-directional detection RFID tag is expressed by Formula 1, which is: Γ=(Z C -Z A ) / (Z C +Z A ), where ZC is the impedance of the RF chip and ZA is the impedance of the multi-directional detection RFID tag. Formula 2 is:

[0060]

[0061] Formula 3 is:

[0062]

[0063] Formula 4 is: Formula 5 is:

[0064] Formula 6 is:

[0065]

[0066] Formula 7 is:

[0067]

[0068] Where j is the imaginary unit and ω is the angular frequency of the RFID tag for multi-directional detection.

[0069] In the embodiment of the present invention, the radio frequency chip 5 includes a voltage regulator, a modulator, a demodulator, a logic control unit and a storage unit.

[0070] It should be noted that the voltage regulator can be used to convert the radio frequency signal transmitted by the reader corresponding to the multi-directional detection RFID tag into a DC power supply, and store the converted DC power supply through a large capacitor. The stored voltage is then used to provide a stable power supply to the modulator, demodulator, logic control unit, and storage unit through a voltage stabilization circuit. The modulator can be used to logically control the data sent by the video chip 5, which is modulated and then transmitted to the antenna 2 for transmission to the reader. The demodulator can be used to remove the carrier in the signal to obtain the true modulated signal. The logic control unit can be used to decode the signal sent by the reader and transmit data to the reader according to its requirements. The storage unit includes EEPROM and ROM, which can be used to store identification data.

[0071] In an embodiment of the present invention, the multi-directional detection RFID tag uses a radio frequency chip, a coupling ring, and a finger capacitor to form a matching circuit for each tag excitation circuit, so that the multi-directional detection RFID tag adjusts the capacitance and inductance values of the matching circuit by adjusting the finger spacing, finger length, and size of the branch capacitor of the finger capacitor, so that the matching circuit achieves impedance matching between the radio frequency chip and the impedance of the multi-directional detection RFID tag.

[0072] In an embodiment of the present invention, the matching capacitor 6 can be used for matching between the multi-directional detection RFID tag and the radio frequency chip 5. The multi-directional detection RFID tag is flexibly set by matching the matching capacitor 6 in conjunction with the interdigital capacitor 4. When the capacitance value of the radio frequency chip 5 is small to a certain value, it can be removed, so that the multi-directional detection RFID tag has better performance.

[0073] The present invention provides a multi-directional detection RFID tag, comprising a dielectric substrate and an antenna attached to the top surface of the dielectric substrate. Tag excitation circuits are provided in all four directions of the dielectric substrate, each of which includes a radio frequency chip, a coupling loop, a side-branch inductor, an interdigital capacitor, and a matching capacitor. The dielectric substrates include a first dielectric substrate, a second dielectric substrate, and a third dielectric substrate. The radio frequency chip and the matching capacitor are provided on the top surface of the first dielectric substrate. Coupling loops are provided on the bottom surface of the first dielectric substrate and the top surface of the second dielectric substrate. The radio frequency chip and the matching capacitor are connected to the coupling loops through vias in the first dielectric substrate. The interdigital capacitors are provided on the bottom surface of the second dielectric substrate and connected to the coupling loops through vias in the second dielectric substrate. Side-branch inductors are connected to both ends of the interdigital capacitors. By providing tag excitation circuits in all four directions of the dielectric substrate, the multi-directional detection RFID tag can detect cracks and strain changes in metal samples in all four directions, resolving the technical problem that existing radio frequency identification technology can only detect the structural health of metal components from one direction, resulting in relatively one-sided detection results.

[0074] In an embodiment of the present invention, when the multi-directional detection RFID tag is used to perform health detection on the metal sample to be tested, the operation of each tag excitation circuit can be controlled in turn to achieve multi-directional detection of the metal sample to be tested, thereby improving the efficiency of the health detection of the metal sample to be tested.

[0075] In one embodiment of the present invention, the first dielectric substrate 11 and the second dielectric substrate 12 and the second dielectric substrate 12 and the third dielectric substrate 13 are both fixedly bonded by a bonding agent.

[0076] Example 2

[0077] Figure 5 This is a framework diagram of a radio frequency detection system according to an embodiment of the present invention. Figure 6 This is a framework diagram of a reader in a radio frequency detection system according to an embodiment of the present invention.

[0078] like Figure 5 As shown, the present invention also provides a radio frequency detection system, including an RFID tag 10, a reader 20 for bidirectional communication with the RFID tag 10, and a controller 30 for controlling the operation of the RFID tag 10 and the reader 20. The RFID tag 10 is the above-mentioned multi-directional detection RFID tag.

[0079] It should be noted that the multi-directional detection RFID tag has been described in Example 1 and will not be further described in this example. RFID tag 10, also known as a smart tag, is an ultra-micro tag consisting of a radio frequency chip and a wireless communication antenna. Its built-in radio frequency antenna is used to communicate with reader 20. When the radio frequency detection system is operating, reader 20 emits a query / energy signal. RFID tag 10 receives the query / energy signal via its antenna and rectifies a portion of it into a DC power source to power the circuitry within RFID tag 10. The remaining energy signal is modulated by the data stored within RFID tag 10 and then reflected back to reader 20. RFID tag 10 is the true data carrier of the radio frequency detection system and can take on different forms depending on its application. For example, in the field of animal tracking and tracing, it can be called an animal tag, animal tracking tag, or electronic dog tag; in the field of automatic vehicle identification such as toll collection or vehicle entry and exit management, it can be called a vehicle long-distance IC card, vehicle long-distance radio frequency tag, or electronic license plate; and in the field of access control, it can be called an access card or card. The RFID tag 10 used in the RF detection system is capable of detecting cracks and strains. When the RFID tag 10 detects the presence of cracks and strains, its RF signal will change accordingly, which is read by the reader 20 and finally analyzed and processed by the controller 30.

[0080] like Figure 5 As shown, in one embodiment of the present invention, the reader 20, also known as a reader, reader / writer, etc., plays an important role in the radio frequency detection system. The reader 20 is mainly responsible for bidirectional communication with the RFID tag 10, and at the same time receives control instructions from the controller 30. The frequency of the reader 20 determines the frequency band in which the radio frequency detection system operates, and the power of the reader 20 determines the effective distance of radio frequency identification. The reader 20 can be a reading or reading and writing device according to the structure and technology used. It is the information control and processing center of the radio frequency detection system. Figure 6 As shown, the reader 20 is generally composed of three parts: a radio frequency interface unit, a logic control unit and an antenna.

[0081] It should be noted that the radio frequency interface unit can be used to generate high-frequency transmission energy, which is used to activate the RFID tag 10 and provide energy for it. The radio frequency interface unit can also modulate the transmission signal of the high-frequency transmission energy and transmit the modulated transmission signal to the RFID tag 10. The radio frequency interface unit can also be used to receive and modulate the radio frequency signal from the RFID tag 10. There are two separated signal channels in the radio frequency interface unit, and the two signal channels are used for data transmission in two directions between the RFID tag 10 and the reader 20. Among them, the two signal channels are the transmitting channel of the transmitter and the receiving channel of the receiver. The transmitting channel of the transmitter can transmit a signal channel that can send data to the RFID tag 10 through the transmitter branch channel, and the receiving channel of the receiver can receive a signal channel that can receive data from the RFID tag 10 through the receiver branch channel. The logic control unit, also known as the read / write module, has the following functions: first, to communicate with the controller 30 and execute instructions sent from the controller 30; second, to control the communication process between the reader 20 and the RFID tag 10; third, to be able to encode the transmitted signal and decode the received signal; fourth, to encrypt and decrypt the data transmitted between the reader 20 and the RFID tag 10; fifth, to be able to execute the anti-collision algorithm; and sixth, to verify the identity of the reader 20 and the RFID tag 10. An antenna is a device that can convert received electromagnetic waves into current signals, or convert current signals into electromagnetic waves and transmit them. In this radio frequency detection system, the reader 20 must transmit energy through the antenna to form an electromagnetic field, and then identify the RFID tag 10 through the electromagnetic field. Therefore, the electromagnetic field range formed by the antenna on the reader 20 is the readable zone of the reader 20.

[0082] like Figure 5 As shown, the controller 30 can effectively control the reader 20 to read and write information from the RFID tag 10, and centrally collect and process the target information or detection information received by the reader 20. In this embodiment, the controller 30 can be set on the RFID application system software, which can be integrated into existing e-commerce and e-government platforms and combined with systems such as ERP, CRM, and WMS to improve production efficiency in various industries.

[0083] It should be noted that middleware is also installed between the reader 20 and the controller 30 of this RF detection system. This middleware manages computing resources and network communications. Through a set of universal application programming interfaces (APIs) provided by the middleware, the API can connect to the reader 20 and read the data received by the reader 20. If the database software or back-end application storing RFID tags 10 in the controller 30 is added or replaced by other software, or if the number of readers 20 increases, the controller 30 can handle it without modification, thus reducing the maintenance complexity of many-to-many connections.

[0084] In the embodiment of the present invention, the radio frequency detection system can realize the advantages of real-time detection, passiveness, and low cost for metal components through the RFID tag with four-directional detection, and can also realize the detection of multi-directional crack characteristics and strain.

[0085] Example 3:

[0086] Figure 7 This is a flowchart of the steps of the crack detection method of the radio frequency detection system according to an embodiment of the present invention.

[0087] like Figure 7 As shown, the present invention also provides a crack detection method for a radio frequency detection system, which is applied to the above radio frequency detection system. The crack detection method includes the following steps:

[0088] S1. Place an RFID tag on a first metal sample to be tested of a certain type with a known crack width and obtain the crack width of the first metal sample to be tested. Use the reader of the radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain the first resonant frequency data corresponding to the working feedback of each tag excitation circuit.

[0089] It should be noted that the contents of the radio frequency detection system have been described in Example 2 and will not be further described in this example. In step S1, an RFID tag according to Example 1 is placed on a metal sample (denoted as the first metal sample) of a class requiring health testing and having a known crack width. The controller of the radio frequency detection system according to Example 2 controls the reader to activate the tag excitation circuits in each direction of the RFID tag in turn, so that the tag excitation circuits operate and obtain signal data fed back by the activated tag excitation circuits, i.e., first resonant frequency data. This first resonant frequency data is received by the reader of the radio frequency detection system and transmitted to the controller. In this embodiment, the tag excitation circuits in each direction of the RFID tag are activated in turn, and four first resonant frequency data of the first metal sample are correspondingly obtained. The operation of the tag excitation circuit refers to the following: the circuit (coupling loop, matching capacitor, interdigital capacitor, and side inductor) where the RF chip is located in the activated tag excitation circuit is in a conductive state, and the circuit where the unactivated tag excitation circuit is located is in an open circuit. That is, a tag excitation circuit path is formed by the RF chip, matching capacitor, coupling ring, interdigital capacitor, and side inductor, and the tag excitation circuit in the path can receive the energy sent by the reader to the antenna in the RFID tag, so that the tag excitation circuit in this path can perform crack detection on the first metal sample to be tested.

[0090] S2. Determine the crack characteristic sensitivity and first frequency difference corresponding to each tag excitation circuit based on the first resonant frequency data fed back by each tag excitation circuit and the first reference frequency, and determine the direction of the crack in the first metal sample to be tested based on the first frequency difference. The first reference frequency is the resonant frequency of a certain type of metal sample in a healthy state.

[0091] It should be noted that in step S2, the first frequency difference and crack characteristic sensitivity in each direction are calculated based on the four first resonant frequency data detected in four directions of the first metal sample to be tested and the reference frequency. In this embodiment, the crack characteristic sensitivity can be used to determine the direction in which the crack in the metal sample to be tested has occurred. Specifically, when a crack appears in the metal sample, the dielectric constant of the air in the crack changes relative to the metal sample in a healthy state, thereby causing the capacitance value of the interdigital capacitor in the tag excitation circuit to change, and the matching circuit impedance to change accordingly. Accordingly, the resonant frequency of the RFID tag read by the reader also changes. If a crack exists in a certain direction of the first metal sample to be tested, the impedance of the matching circuit where the interdigital capacitor in the tag excitation circuit perpendicular to that direction is located will change compared to the metal sample in a healthy state, causing the resonant frequency of the matching circuit to change compared to the first metal sample in a healthy state. When the information of the four RF chips on the RFID tag is read in turn, by comparing it with the resonant frequency of each matching circuit in a healthy state, it is possible to know which RF chip's matching circuit the crack is located in, thereby determining the direction of the crack. For example, if the first frequency difference in a certain direction is greater than 0, it means that the direction is the direction of the crack.

[0092] Figure 8 This is a comparison diagram of the resonant frequencies in the crack detection method of the radio frequency detection system according to an embodiment of the present invention.

[0093] Furthermore, the crack detection method of the radio frequency detection system includes: determining the crack characteristic sensitivity and frequency difference corresponding to each tag excitation circuit based on the first resonant frequency data and the first reference frequency fed back by each tag excitation circuit, and using a crack characteristic relationship formula. The crack characteristic relationship formula is: S = Δf1 / H, Δf1 = |f1-f0|, where S is the crack characteristic sensitivity, Δf1 is the first frequency difference, f1 is the first resonant frequency data, f0 is the first reference frequency, and H is the crack width.

[0094] It should be noted that if Figure 8 As shown in the figure, if the resonant frequency of the first metal sample under test in a healthy state is used as the first reference frequency, and f0 = 0.958 GHz, and H = 2 mm, then the resonant frequency data f1 = 0.964 GHz detected by the RFID tag in one direction of the first metal sample under test, then the first frequency difference Δf1 = 6 MHz, and its crack characteristic sensitivity is 3 MHz / mm. This means that if a 1 mm deep crack appears in the metal sample under test, the resonant frequency of the tag will shift by 3 MHz. Here, 1 GHz = 1000 MHz.

[0095] S3. Place the RFID tag on a second metal sample to be tested of a certain type with an unknown crack width, and use the reader of the radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain the second resonant frequency data corresponding to the working feedback of each tag excitation circuit.

[0096] It should be noted that the first metal sample to be tested and the second metal sample to be tested belong to the same metal type. For example, if the first metal sample to be tested is an iron metal sample, then the second metal sample to be tested is also an iron metal sample of the same type as the first metal sample to be tested. Metal samples of the same type have the same crack characteristic sensitivity. In step S3, the second resonant frequency data of the second metal sample to be tested is obtained primarily using the same method as step S1.

[0097] S4. Determine a second frequency difference based on the second resonant frequency data fed back by each tag excitation circuit and the first reference frequency, and determine the crack width of the second metal sample to be tested based on the crack characteristic sensitivity and the second frequency difference.

[0098] It should be noted that, in step S4, the crack width of the second metal sample to be tested can be determined according to the crack characteristic sensitivity and the second frequency difference.

[0099] Furthermore, the crack detection method of the radio frequency detection system includes: determining the crack width of the second metal sample to be tested based on the crack characteristic sensitivity and the second frequency difference, and using an offset relationship to determine the crack width of the second metal sample to be tested, the offset relationship is: L = Δf2 / S, Δf2 = |f2-f0|, where S is the crack characteristic sensitivity of a certain type of metal sample, Δf2 is the second frequency difference, f2 is the second resonant frequency data, f0 is the first reference frequency, and L is the crack width of the second metal sample to be tested.

[0100] In one embodiment of the present invention, in a process of obtaining resonant frequency data corresponding to the working feedback of each tag excitation circuit by taking turns controlling the operation of the tag excitation circuit in the RFID tag through the radio frequency detection system, the crack detection method of the radio frequency detection system includes: controlling the tag impedance of the RFID tag to be equal to the radio frequency chip impedance of the RFID tag through the radio frequency detection system.

[0101] It should be noted that by controlling the tag impedance of the RFID tag to be equal to the RFID chip impedance of the RFID tag through the RFID detection system, the resonant frequency reflected by the RFID tag can be made more accurate, and the frequency of the metal sample to be tested can be obtained more accurately, thereby improving the accuracy of the RFID detection system in detecting cracks.

[0102] In an embodiment of the present invention, the crack detection method of the radio frequency detection system realizes crack detection of a first metal sample to be tested of a certain type with a known crack width through the radio frequency detection system, and can detect the direction of crack occurrence, providing a basis for preventing the crack from continuing to deteriorate and repairing the first metal sample to be tested; it can also detect the width of the crack of the same type of second metal sample to be tested, providing data for studying the changes in the cracks of the second metal sample to be tested, and realizing the diversification of the crack information detection of the second metal sample to be tested.

[0103] Example 4:

[0104] Figure 9 This is a flowchart of the steps of the strain detection method of the radio frequency detection system according to an embodiment of the present invention.

[0105] like Figure 9 As shown, an embodiment of the present invention further provides a strain detection method of a radio frequency detection system, which is applied to the above radio frequency detection system. The strain detection method of the radio frequency detection system includes the following steps:

[0106] S10. Place the RFID tag on a third type of metal sample to be tested with a known bending radius, and use the reader of the radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain the first strain resonance frequency data corresponding to the working feedback of each tag excitation circuit.

[0107] It should be noted that the contents of the RF detection system have been described in Example 2 and will not be further described in this example. In step S10, an RFID tag according to Example 1 is placed on a certain type of metal sample to be tested (denoted as the third metal sample to be tested) with a known bending radius requiring health testing. The controller of the RF detection system according to Example 2 controls the reader to activate the tag excitation circuits in each direction of the RFID tag in turn, so that the tag excitation circuits operate and obtain signal data fed back by the activated tag excitation circuits, namely, first strain resonance frequency data. This first strain resonance frequency data is received by the reader of the RF detection system and transmitted to the controller. In this embodiment, the tag excitation circuits in each direction of the RFID tag are activated in turn, and four resonance frequency data of the metal sample to be tested are correspondingly obtained. The operation of the tag excitation circuit refers to the following: the circuit (coupling loop, matching capacitor, interdigital capacitor, and side inductor) where the RF chip is located in the excited tag excitation circuit is in a conductive state, and the circuit where the unactivated tag excitation circuit is located is in an open circuit. That is, a tag excitation circuit path is formed by the RF chip, matching capacitors, coupling rings, interdigital capacitors, and side inductors, and the tag excitation circuit in the path can receive the energy sent by the reader to the antenna in the RFID tag, so that the tag excitation circuit in this path can perform strain detection on the third metal sample to be tested.

[0108] S20. Determine the strain sensitivity and first strain frequency difference corresponding to each tag excitation circuit based on the first strain resonant frequency data fed back by each tag excitation circuit and the second reference frequency, and determine the direction in which the third metal sample to be tested will be strained based on the first strain frequency difference. The second reference frequency is the resonant frequency of the third metal sample in a healthy state.

[0109] It should be noted that in step S20, the strain frequency difference and strain sensitivity for each direction are calculated based on the four strain resonance frequency data detected in the four directions of the metal sample to be tested. In this embodiment, the strain sensitivity can be used to determine the direction in which the crack in the third metal sample to be tested has occurred. That is, when the metal sample is strained, the installed RFID tag will also be strained, thereby changing the RFID tag's current path, impedance, and other parameters, causing the RFID tag's resonant frequency to shift. When the RFID tag is strained in a certain direction, the stress on its matching circuit in the orthogonal direction is the greatest, and the strain has the greatest impact. In step S10, the first strain resonance frequency data for the four directions of the third metal sample to be tested, detected by the RFID tag, are acquired in turn. Each first strain resonance frequency data is compared with the pre-strain reference frequency to calculate each strain resonance frequency data, thereby determining the direction in which the strain has occurred. For example, if the first strain frequency difference in a certain direction is greater than 0, it indicates that the third metal sample to be tested has been strained in that direction.

[0110] Figure 10 This is a comparison diagram of the resonant frequencies in the strain detection method of the radio frequency detection system according to an embodiment of the present invention.

[0111] Furthermore, the strain detection method of the radio frequency detection system includes: determining the strain sensitivity and strain frequency difference corresponding to each tag excitation circuit based on the first strain resonance frequency data and the second reference frequency fed back by each tag excitation circuit, and using a strain variable relationship formula. The strain variable relationship formula is: Y = Δf1' / (1 / r), Δf1' = |f1'-f0'|, where Y is the strain variable sensitivity, Δf1' is the first strain frequency difference, f1' is the first strain resonance frequency data, f0' is the second reference frequency, and r is the bending radius.

[0112] It should be noted that if Figure 10As shown in the figure, if the resonant frequency of the third metal sample under test in its healthy state is used as the second reference frequency, and f0' = 0.958 GHz, and r = 900 mm, the first strain resonant frequency data f = 0.952 GHz detected by the RFID tag in one direction of the third metal sample under test is then the first strain frequency difference Δf1' = 6 MHz, and the strain sensitivity is 5400 MHz / mm. Here, 1 GHz = 1000 MHz.

[0113] S30. Place the RFID tag on a fourth type of metal sample to be tested with an unknown bending radius, and use the reader of the radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain the second strain resonance frequency data corresponding to the working feedback of each tag excitation circuit.

[0114] It should be noted that the third and fourth metal samples to be tested belong to the same metal type. For example, if the third metal sample to be tested is ferrous, then the fourth metal sample to be tested is also ferrous. Metal samples of the same type have the same strain sensitivity. In step S30, the second strain resonance frequency data of the fourth metal sample to be tested is obtained primarily using the same method as step S10.

[0115] S40. Determine the second strain frequency difference corresponding to each tag excitation circuit based on the second strain resonance frequency data fed back by each tag excitation circuit and the second reference frequency, and determine the strain curvature of the fourth metal sample to be tested based on the strain sensitivity and the second strain frequency difference.

[0116] It should be noted that, in step S40, the strain curvature of the fourth metal sample to be tested can be determined according to the strain sensitivity and the second strain frequency difference.

[0117] Furthermore, the strain detection method of the radio frequency detection system includes: determining the strain curvature of the fourth metal sample to be tested based on the strain sensitivity and the second strain frequency difference using a strain curvature relationship formula, wherein the strain curvature relationship formula is: K = Δf2' / Y, Δf2' = |f2'-f0'|, where Y is the strain sensitivity, Δf2' is the second strain frequency difference, K is the strain curvature of the fourth metal sample to be tested, f2' is the second strain resonance frequency data, and f0' is the second reference frequency.

[0118] In an embodiment of the present invention, the strain detection method of the radio frequency detection system realizes strain detection of a third metal sample to be tested with a known strain bending radius through the radio frequency detection system. The obtained strain sensitivity can detect the direction of the strain, providing a basis for preventing the strain from continuing to deteriorate and repairing the metal sample to be tested; it can also detect the curvature of the strain of a fourth metal sample to be tested with an unknown bending radius that is the same type as the third metal sample to be tested, provide data for studying the changes in the strain of the fourth metal sample to be tested, and realize diversified detection of the strain information of the fourth metal sample to be tested.

[0119] In an embodiment of the present invention, the RF detection system can sequentially detect and acquire data from the metal sample under test using information from the RF chips on the RFID tag in four directions. By comparing each acquired data point with the reference frequency of each matching circuit in a healthy state, the system can determine which matching circuit the RF chip in question is in, thereby determining the direction of the crack or strain. Furthermore, the corresponding crack width and strain curvature can be determined based on the data obtained from the detected crack and strain directions.

[0120] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0121] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0122] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0123] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0124] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0125] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-directional detection RFID tag, comprising a dielectric substrate and an antenna attached to the top surface of the dielectric substrate, characterized in that: Tag excitation circuits are provided on all four sides of the dielectric substrate. Each tag excitation circuit includes a radio frequency chip, a coupling ring, a side-branch inductor, an interdigital capacitor, and a matching capacitor. The dielectric substrate includes a first dielectric substrate, a second dielectric substrate, and a third dielectric substrate. The radio frequency chip and the matching capacitor are provided on the upper surface of the first dielectric substrate. The coupling ring is provided on the lower surface of the first dielectric substrate and the upper surface of the second dielectric substrate. The radio frequency chip and the matching capacitor are connected to the coupling ring through a via hole of the first dielectric substrate. The interdigital capacitor is provided on the lower surface of the second dielectric substrate and connected to the coupling ring through a via hole of the second dielectric substrate. Both ends of the interdigital capacitor are connected to the side-branch inductor. The RF chip, the coupling ring, and the interdigital capacitors constitute a matching circuit for each tag excitation circuit. The capacitance and inductance of the matching circuit are adjusted by adjusting the interdigital spacing and length of the interdigital capacitors and the size of the side inductors to match the impedance of the RF chip with the impedance of the multi-directional detection RFID tag, so that the power reflection coefficient corresponding to the RF chip is minimized at a certain frequency. The first dielectric substrate and the second dielectric substrate, and the second dielectric substrate and the third dielectric substrate are fixedly bonded by a bonding agent.

2. A radio frequency detection system, characterized in that: The invention comprises an RFID tag, a reader for bidirectional communication with the RFID tag, and a controller for controlling the operation of the RFID tag and the reader. The RFID tag is the multi-directional detection RFID tag according to claim 1.

3. A crack detection method for a radio frequency detection system, applied to the radio frequency detection system according to claim 2, characterized in that: The crack detection method comprises the following steps: Placing an RFID tag on a first metal sample to be tested with a certain type of crack width known to obtain the crack width of the first metal sample to be tested, and using a reader of a radio frequency detection system to control the operation of the tag excitation circuit in the RFID tag in turn to obtain first resonant frequency data corresponding to the operating feedback of each tag excitation circuit; Determining the crack characteristic sensitivity and the first frequency difference corresponding to each tag excitation circuit according to the first resonant frequency data and the first reference frequency fed back by each tag excitation circuit, and determining the direction of the crack in the first metal sample to be tested according to the first frequency difference; Placing an RFID tag on a second metal sample to be tested of a certain type with an unknown crack width, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining second resonant frequency data corresponding to the operating feedback of each tag excitation circuit; Determining a second frequency difference based on the second resonant frequency data fed back by each tag excitation circuit and the first reference frequency, and determining a crack width of the second metal sample to be tested based on the crack characteristic sensitivity and the second frequency difference; The first reference frequency is the resonant frequency of a certain type of metal sample in a healthy state.

4. The crack detection method of the radio frequency detection system according to claim 3, characterized in that: include: According to the first resonant frequency data and the first reference frequency fed back by each tag excitation circuit, the crack characteristic sensitivity and the first frequency difference corresponding to each tag excitation circuit are determined using a crack characteristic relationship formula, wherein the crack characteristic relationship formula is: , where S is the crack characteristic sensitivity, is the first frequency difference, f1 is the first resonant frequency data, f0 is the first reference frequency, and H is the crack width.

5. The crack detection method of the radio frequency detection system according to claim 3, characterized in that: include: The crack width of the second metal sample to be tested is determined according to the crack characteristic sensitivity and the second frequency difference, and the crack width of the second metal sample to be tested is determined using an offset relationship, and the offset relationship is: , where S is the crack characteristic sensitivity of a certain type of metal sample, is the second frequency difference, f2 is the second resonant frequency data, f0 is the first reference frequency, and L is the crack width of the second metal sample to be tested.

6. The crack detection method of the radio frequency detection system according to claim 3, characterized in that: In the process of obtaining resonant frequency data corresponding to the working feedback of each tag excitation circuit by taking turns to control the operation of the tag excitation circuit in the RFID tag through the radio frequency detection system, the crack detection method of the radio frequency detection system includes: controlling the tag impedance of the RFID tag to be equal to the radio frequency chip impedance of the RFID tag through the radio frequency detection system.

7. A strain detection method for a radio frequency detection system, applied to the radio frequency detection system according to claim 2, characterized in that: The strain detection method comprises the following steps: Placing an RFID tag on a third type of metal sample to be tested with a known bending radius, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining first strain resonance frequency data corresponding to the operating feedback of each tag excitation circuit; Determining the strain sensitivity and the first strain frequency difference corresponding to each tag excitation circuit based on the first strain resonance frequency data and the second reference frequency fed back by each tag excitation circuit, and determining the direction in which the third metal sample to be tested is strained based on the first strain frequency difference; Placing an RFID tag on a fourth type of metal sample to be tested with an unknown bending radius, and using a reader of a radio frequency detection system to control the operation of a tag excitation circuit in the RFID tag in turn, and obtaining second strain resonance frequency data corresponding to the operating feedback of each tag excitation circuit; Determining a second strain frequency difference corresponding to each tag excitation circuit based on the second strain resonance frequency data fed back by each tag excitation circuit and a second reference frequency, and determining a strain curvature of the fourth metal sample to be tested based on the strain sensitivity and the second strain frequency difference; The second reference frequency is the resonant frequency of a certain type of metal sample in a healthy state.

8. The strain detection method of the radio frequency detection system according to claim 7, characterized in that: include: According to the first strain resonance frequency data and the second reference frequency fed back by each tag excitation circuit, the strain sensitivity and the first strain frequency difference corresponding to each tag excitation circuit are determined using a strain relationship formula, wherein the strain relationship formula is: , where Y is the strain sensitivity, is the first strain frequency difference, is the first strain resonance frequency data, is the second reference frequency, and r is the bending radius.

9. The strain detection method of the radio frequency detection system according to claim 7, characterized in that: include: According to the strain sensitivity and the second strain frequency difference, the strain curvature of the fourth metal sample to be tested is determined using a strain curvature relationship, and the strain curvature relationship is: , where Y is the strain sensitivity, is the second strain frequency difference, K is the strain curvature of the fourth metal sample to be tested, is the second strain resonance frequency data, is the second reference frequency.

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