Passive Wireless Detection Device and Method for Bolt Tightening State with Frequency-Stress Mapping

Abstract

The present application discloses a passive wireless detection device and method for frequency-stress mapping of bolt fastening states, which relates to the field of rail traffic safety monitoring. In this device, a receiving-end capacitive harmonic circuit, a transmitting-end capacitive harmonic circuit, a first piezoelectric material, and a second piezoelectric material are all arranged on the side wall of the nut, and the nut is arranged on the bolt to be measured; interdigital electrodes are arranged on the surface of the piezoelectric material; a signal generating device emits an excitation signal to the receiving-end capacitive harmonic circuit, and the receiving-end capacitive harmonic circuit mixes and filters the excitation signal so that the receiving-end capacitive harmonic circuit generates resonance and generates an alternating current; the first interdigital electrode is connected to the receiving-end capacitive harmonic circuit, and the second interdigital electrode is connected to the transmitting-end capacitive harmonic circuit; a signal receiving device obtains the resonant frequency of the transmitting-end capacitive harmonic circuit, and a judgment host determines the pre-tightening force and rotation angle of the bolt to be measured according to the resonant frequency, and then obtains the fastening state. The present application can automatically detect the bolt fastening state without manual operation and without battery power supply.

Description

Technical Field

[0001] This application relates to the field of rail transit safety monitoring, and particularly to a passive wireless detection device and method for bolt fastening status with frequency-stress mapping. Background Art

[0002] Bolt fasteners are key components to ensure the structural stability and operation safety of transportation equipment. In the complex driving environment with long hours, high intensity, and high load, bolts may become loose, gradually weakening their fastening ability. Moreover, due to their long-term exposure to the natural environment, bolts may have safety hazards such as corrosion, fatigue, and fracture. Bolt loosening or damage may lead to equipment failures, operation interruptions, and even major safety accidents such as train derailment, seriously threatening the lives of passengers. Therefore, monitoring the loosening of various bolts in the rail transit industry is of great significance for improving industry safety.

[0003] The existing mainstream method for detecting bolt fastening status is manual inspection after the train stops. That is, for some important bolts, workers will use a torque wrench to tighten them again. This method is relatively reliable, but it still cannot completely avoid the problems of missed inspection and misjudgment caused by human errors. Moreover, it requires a large amount of human resources, is time-consuming and laborious, and cannot perform real-time and automated detection of bolt loosening. Other emerging bolt loosening detection technologies, such as video monitoring method and gasket type pressure sensor measurement method, have improved the disadvantages of the manual detection method in some aspects, but still have many problems. For example, the video monitoring method still requires manual visual inspection and has visual blind spots, and can only detect bolts that can be photographed by the camera; the pressure measurement module and wireless transmission module of the gasket type pressure sensor measurement method both rely on a micro battery for power supply, greatly reducing the service life, and the usage scenario is severely limited. Currently, on the market, the principle of the traditional gasket type pressure sensor measurement method has been improved so that it no longer requires battery power supply. The main representatives are Radio Frequency Identification (RFID) gasket type pressure sensors and Near Field Communication (NFC) gasket type pressure sensors. The former uses high-frequency passive RFID tags for communication, but this method is greatly affected by metal and cannot adapt to the daily working environment of rail transit; the communication distance of the latter is very short, and the pressure information can only be read when it is closely attached, and still requires manual operation.

[0004] Therefore, the main problems existing in the existing bolt fastening status detection methods are mainly the following two points.

[0005] 1. Manpower is required for detection, with high labor costs, cumbersome operations, and professional training is needed.

[0006] 2. Miniature batteries are required to power functions such as pressure detection, analog-to-digital conversion, and wireless communication, resulting in low durability and limited usage scenarios. Summary of the Invention

[0007] The objective of this application is to provide a passive wireless detection device and method for bolt tightening status with frequency-stress mapping, which can automatically detect the bolt tightening status without manual operation and without battery power supply.

[0008] To achieve the above objective, this application provides the following solutions: In the first aspect, this application provides a passive wireless detection device for bolt tightening status with frequency-stress mapping, which is used to simultaneously measure the tightening status of n bolts to be measured at n positions, where n is a positive integer greater than or equal to 1. The passive wireless detection device for bolt tightening status with frequency-stress mapping includes: a signal generating device, a signal receiving device, a judgment host, and n bolt tightening status detection modules; the n bolt tightening status detection modules are arranged in one-to-one correspondence with the bolts to be measured at n positions. The signal receiving device is communicatively connected to the judgment host.

[0009] The bolt tightening status detection module includes: a nut, a receiving-end capacitive harmonic circuit, a transmitting-end capacitive harmonic circuit, a first interdigital electrode, a second interdigital electrode, a first piezoelectric material, and a second piezoelectric material; the nut is arranged on the bolt to be measured; the receiving-end capacitive harmonic circuit, the transmitting-end capacitive harmonic circuit, the first piezoelectric material, and the second piezoelectric material are all arranged on the side wall of the nut; the first interdigital electrode is arranged on the surface of the first piezoelectric material, and the second interdigital electrode is arranged on the surface of the second piezoelectric material; the transmitting-end capacitive harmonic circuit includes a mechanically variable capacitor; the two plates of the mechanically variable capacitor are arranged along the axial direction of the nut; the adjacent fingers of the first interdigital electrode are arranged along the axial direction of the nut; the adjacent fingers of the second interdigital electrode are arranged along the axial direction of the nut; the first interdigital electrode and the second interdigital electrode are symmetric about the axial direction of the nut; the first interdigital electrode is electrically connected to the receiving-end capacitive harmonic circuit, and the second interdigital electrode is electrically connected to the transmitting-end capacitive harmonic circuit.

[0010] The signal generating device is used to transmit an excitation signal to the receiving end resonance circuit in each bolt fastening state detection module. The receiving end resonance circuit is used to mix and filter the excitation signal so that the receiving end resonance circuit generates resonance and generates an alternating current. The signal receiving device is used to obtain the resonance frequency of the transmitting end resonance circuit in each bolt fastening state detection module. The judgment host is used to determine the fastening state parameters of the bolts to be measured at each position according to the resonance frequency of the transmitting end resonance circuit in each bolt fastening state detection module, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position. When n is greater than 1, the resonance frequencies of the alternating currents generated by the receiving end resonance circuits in different bolt fastening state detection modules are different. The fastening state parameters include: pre-tightening force and rotation angle.

[0011] Optionally, the receiving end resonance circuit specifically includes: a three-terminal composite semiconductor circuit and an LC resonance circuit. The input end of the three-terminal composite semiconductor circuit is connected to the signal generating device. The input end of the LC resonance circuit is connected to the output end of the three-terminal composite semiconductor circuit. The output end of the LC resonance circuit is connected to the first interdigital electrode. The three-terminal composite semiconductor circuit is used to mix the excitation signal, and the LC resonance circuit is used to filter the mixed excitation signal. When n is greater than 1, the capacitance values of the LC resonance circuits in different bolt fastening state detection modules are different.

[0012] Optionally, when n equals 1, the judgment host is used to determine the fastening state parameters of the bolt to be measured based on the resonance frequency of the transmitting end resonance circuit in the bolt fastening state detection module, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtain the fastening state of the bolt to be measured based on the fastening state parameters of the bolt to be measured. When n is greater than 1, the judgment host is used to determine the fastening state parameters of the bolts to be measured at each position based on the resonance frequency set, the preset resonance frequency interval corresponding to the bolts to be measured at each position, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position. The resonance frequency set includes: the resonance frequencies of the transmitting end resonance circuits in each bolt fastening state detection module.

[0013] Optionally, the nut includes: a lower nut body and an upper nut body. The upper nut body is arranged above the lower nut body. The material of the lower nut body is metal, and the material of the upper nut body is a high molecular composite material. The receiving end resonance circuit, the transmitting end resonance circuit, the first piezoelectric material, and the second piezoelectric material are all arranged on the side wall of the upper nut body.

[0014] Optionally, the signal generating device, the signal receiving device, and the judgment host are all integrated on a fixed-point detection system at the unmanned patrol vehicle or the train storage area.

[0015] In a second aspect, the present application provides a passive wireless detection method for bolt fastening state with frequency-stress mapping, which is applied to the above-mentioned passive wireless detection device for bolt fastening state with frequency-stress mapping. The passive wireless detection method for bolt fastening state with frequency-stress mapping includes: obtaining the resonance frequency of the transmitting-end capacitive harmonic circuit in each bolt fastening state detection module.

[0016] Determine the fastening state parameters of the bolts to be measured at each position based on the resonance frequency of the transmitting-end capacitive harmonic circuit in each bolt fastening state detection module, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position; the fastening state parameters include: pre-tightening force and rotation angle.

[0017] Optionally, determining the fastening state parameters of the bolts to be measured at each position based on the resonance frequency of the transmitting-end capacitive harmonic circuit in each bolt fastening state detection module, and obtaining the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position, specifically includes: when n is equal to 1, determining the fastening state parameters of the bolt to be measured based on the resonance frequency of the transmitting-end capacitive harmonic circuit in the bolt fastening state detection module, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtaining the fastening state of the bolt to be measured based on the fastening state parameters of the bolt to be measured.

[0018] When n is greater than 1, determine the fastening state parameters of the bolts to be measured at each position based on the resonance frequency set, the preset resonance frequency interval corresponding to the bolts to be measured at each position, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position; the resonance frequency set includes: the resonance frequencies of the transmitting-end capacitive harmonic circuits in each bolt fastening state detection module.

[0019] Optionally, determining the fastening state parameters of the bolt to be measured based on the resonance frequency of the transmitting-end capacitive harmonic circuit in the bolt fastening state detection module, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtaining the fastening state of the bolt to be measured based on the fastening state parameters of the bolt to be measured, specifically includes: determining the pre-tightening force of the bolt to be measured based on the resonance frequency of the transmitting-end capacitive harmonic circuit in the bolt fastening state detection module and the relationship curve between the resonance frequency and the bolt pre-tightening force.

[0020] Determine the rotation angle of the bolt to be measured based on the resonance frequency of the transmitting-end capacitive harmonic circuit in the bolt fastening state detection module and the relationship curve between the resonance frequency and the bolt rotation angle.

[0021] Determine the fastening state of the bolt to be measured according to the pre-tightening force and rotation angle of the bolt to be measured.

[0022] Optionally, based on the resonant frequency set, the preset resonant frequency intervals corresponding to the bolts to be measured at each position, the relationship curve between the resonant frequency and the bolt pre-tightening force, and the relationship curve between the resonant frequency and the bolt rotation angle, determine the fastening state parameters of the bolts to be measured at each position, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position. Specifically, it includes: based on the resonant frequency set and the preset resonant frequency intervals corresponding to the bolts to be measured at each position, determine the positions of the bolts to be measured corresponding to each resonant frequency in the resonant frequency set.

[0023] Determine the fastening state of the bolts to be measured corresponding to each resonant frequency in the resonant frequency set according to the resonant frequency set, the relationship curve between the resonant frequency and the bolt pre-tightening force, and the relationship curve between the resonant frequency and the bolt rotation angle.

[0024] Based on the fastening state of the bolts to be measured corresponding to each resonant frequency and the positions of the bolts to be measured corresponding to each resonant frequency, determine the fastening state of the bolts to be measured at each position.

[0025] Optionally, based on the resonant frequency set and the preset resonant frequency intervals corresponding to the bolts to be measured at each position, determine the positions of the bolts to be measured corresponding to each resonant frequency in the resonant frequency set. Specifically, for any resonant frequency in the resonant frequency set, determine the position of the bolt to be measured corresponding to the preset resonant frequency interval where the resonant frequency is located as the position of the bolt to be measured corresponding to the resonant frequency.

[0026] According to the specific embodiments provided by the present application, the present application has the following technical effects: The present application provides a passive wireless detection device and method for the fastening state of frequency-stress mapping bolts. The signal generating device automatically generates an excitation signal, the bolt fastening state detection module processes the excitation signal and generates a resonant frequency, the signal receiving device automatically receives the resonant frequency and uploads it to the judgment host, and the judgment host obtains the bolt fastening state according to the resonant frequency. The whole process does not require human participation and can automatically detect the bolt fastening state.

[0027] Because the transmitting end capacitive resonant circuit in the bolt fastening state detection module includes a mechanical variable capacitor, the two plates of the mechanical variable capacitor and the adjacent fingers of the two interdigital electrodes are all arranged along the axial direction of the nut, resulting in the change of the distance between the mechanical variable capacitor and the adjacent fingers of the interdigital electrodes with the nut compression amount. The nut compression amount changes with the magnitude of the bolt pre-tightening force, and the bolt pre-tightening force is different for different fastening states. Therefore, the resonant frequency is related to the bolt fastening state, and the frequency-stress mapping bolt fastening state is adopted.

[0028] The receiving-end capacitive resonance circuit generates alternating current through the resonance between the external excitation signal and its own resonance circuit, eliminating the need for external battery power supply and the dependence on batteries or external power sources. The alternating current drives the first interdigital electrode, the second interdigital electrode, the first piezoelectric material, and the second piezoelectric material to work; the transmitting-end capacitive resonance circuit generates a resonance frequency through the dynamic tuning of the mechanical variable capacitor and sends it to the signal receiving device. The resonance frequency of the transmitting-end capacitive resonance circuit measured is transmitted to the signal receiving device through passive wireless communication technology, which is not affected by the metal environment, solving the problems of poor communication performance and short communication distance of existing passive detection methods in a metal environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 Schematic diagram of the structure of a passive wireless detection device for bolt tightening state with frequency-stress mapping provided by an embodiment of the present application.

[0031] Figure 2 Structure of a nut provided by an embodiment of the present application.

[0032] Figure 3 Equivalent diagram of the receiving-end capacitive resonance circuit provided by an embodiment of the present application.

[0033] Figure 4 Circuit diagram of the receiving-end capacitive resonance circuit provided by an embodiment of the present application.

[0034] Figure 5 Schematic diagram of the setting positions of the first interdigital electrode and the second interdigital electrode provided by an embodiment of the present application.

[0035] Figure 6 Equivalent diagram of the transmitting-end capacitive resonance circuit provided by an embodiment of the present application.

[0036] Figure 7 Circuit diagram of the transmitting-end capacitive resonance circuit provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0038] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] When the bolt is tightened, the pre-tightening force is the largest, and the compression amount of the nut is also the largest. When the bolt becomes loose, the compression amount of the nut will gradually become smaller. Based on this, the present application provides a passive wireless detection device for bolt tightening state with frequency-stress mapping, which is used to simultaneously measure the tightening states of n bolts to be measured at n positions, where n is a positive integer greater than or equal to 1. As Figure 1 shown, the passive wireless detection device for bolt tightening state with frequency-stress mapping includes: a signal generating device, a signal receiving device, a judgment host, and n bolt tightening state detection modules; the n bolt tightening state detection modules are arranged in one-to-one correspondence with the bolts to be measured at n positions; the signal receiving device is communicatively connected to the judgment host. The bolt tightening state detection module includes: a nut, a capacitive harmonic passive wireless communication circuit, and a grid-shaped ultrasonic structure; the capacitive harmonic passive wireless communication circuit includes: a receiving-end capacitive harmonic circuit and a transmitting-end capacitive harmonic circuit; the grid-shaped ultrasonic structure includes: a first interdigital electrode, a second interdigital electrode, a first piezoelectric material, and a second piezoelectric material; so the bolt tightening state detection module includes: a nut, a receiving-end capacitive harmonic circuit, a transmitting-end capacitive harmonic circuit, a first interdigital electrode, a second interdigital electrode, a first piezoelectric material, and a second piezoelectric material; the nut is arranged on the bolt to be measured; the receiving-end capacitive harmonic circuit, the transmitting-end capacitive harmonic circuit, the first piezoelectric material, and the second piezoelectric material are all arranged on the side wall of the nut; the first interdigital electrode is arranged on the surface of the first piezoelectric material, and the second interdigital electrode is arranged on the surface of the second piezoelectric material.

[0040] The transmitting-end capacitive harmonic circuit includes a mechanically variable capacitor; the two plates of the mechanically variable capacitor are arranged along the axial direction of the nut, so that its capacitance value changes with the compression amount of the nut; the adjacent fingers of the first interdigital electrode are arranged along the axial direction of the nut; the adjacent fingers of the second interdigital electrode are arranged along the axial direction of the nut, so that the finger spacing between adjacent fingers changes with the compression amount of the nut; as Figure 5 shown, the first interdigital electrode and the second interdigital electrode are symmetric about the axial direction of the nut; the first interdigital electrode is electrically connected to the receiving-end capacitive harmonic circuit. The second interdigital electrode is electrically connected to the transmitting-end capacitive harmonic circuit.

[0041] The signal generating device is used to transmit an excitation signal to the receiving-end capacitive resonant circuit in each bolt fastening state detection module. The receiving-end capacitive resonant circuit is used to mix and filter the excitation signal so that the receiving-end capacitive resonant circuit generates resonance and generates an alternating current. The signal receiving device is used to obtain the resonant frequency of the transmitting-end capacitive resonant circuit in each bolt fastening state detection module and transmit the resonant frequency to the judgment host. The judgment host is used to determine the fastening state parameters of the bolts to be measured at each position according to the resonant frequency of the transmitting-end capacitive resonant circuit in each bolt fastening state detection module, and obtain the fastening state of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position. When n is greater than 1, the resonant frequencies of the alternating currents generated by the receiving-end capacitive resonant circuits in different bolt fastening state detection modules are different. The fastening state parameters include: pre-tightening force and rotation angle. The bolt connection state is set to five grades, namely fully fastened, relatively fastened, relatively loose, loose and detached states.

[0042] In this application, the change in the pre-tightening force of the bolt is reflected by the change in the finger spacing between the interdigital electrodes. Since the finger spacing between the first interdigital electrode and the second interdigital electrode changes with the compression amount of the nut, the mechanical variable capacitor in the transmitting-end capacitive resonant circuit also changes with the compression amount of the nut. When the compression amount of the nut increases, the finger spacing decreases, and the capacitor spacing also decreases. This directly causes the acoustic wave frequency generated by the first interdigital electrode to change, and the alternating voltage applied across the transmitting-end capacitive resonant circuit and the resonant frequency of the transmitting-end capacitive resonant circuit also change. Therefore, the tightness state of the bolt connection is reflected by converting it into a secondary quantity of frequency.

[0043] The detection principle of the passive wireless detection device for bolt fastening state with frequency-stress mapping provided by this application is as follows: First, a signal generating device emits an excitation electromagnetic wave signal. When the excitation electromagnetic wave signal is loaded onto the receiving-end capacitive resonant circuit, the receiving-end capacitive resonant circuit mixes and filters the excitation signal, causing the receiving-end capacitive resonant circuit to resonate and generate an alternating current. Both ends of the two interdigital electrodes have reflective grid bars, which can absorb the sound waves emitted backward. Combining with the structure of the interdigital electrodes themselves, the directional emission of sound waves is achieved. The two poles of the first interdigital electrode are connected to the receiving-end capacitive resonant circuit. When the receiving-end capacitive resonant circuit resonates, an alternating current is generated, which in turn excites an alternating electric field. Due to the existence of the alternating electric field, the first piezoelectric material laid under the first interdigital electrode undergoes the inverse piezoelectric effect and vibrates, exciting sound waves to propagate forward along the nut surface. The waveform and wavelength of the sound waves are closely related to the geometric parameters of the interdigital electrodes; when the sound waves propagate along the nut surface to the second interdigital electrode, the second piezoelectric material undergoes the direct piezoelectric effect under the action of the sound waves, generating polarized charges and forming an electric field at both ends of the second interdigital electrode. Thus, the energy conversion and information transfer process of the interdigital electrodes are completed. The transmitting-end capacitive resonant circuit, which is connected to the second interdigital electrode at the end where the direct piezoelectric effect occurs, has an alternating voltage loaded across its two ends. The transmitting-end capacitive resonant circuit contains a mechanically variable capacitor, whose capacitance value changes with the compression amount of the nut and has a linear relationship with the finger spacing of the second interdigital electrode. When the alternating voltage at both ends of the second interdigital electrode is loaded onto the transmitting-end capacitive resonant circuit, the resonant frequency of the transmitting-end capacitive resonant circuit always remains consistent with the frequency of the alternating voltage loaded across its two ends, thereby achieving resonance and sending the resonant frequency to the signal receiving device. The signal receiving device sends the resonant frequency to the judgment host to determine the fastening state of the bolt to be measured. The capacitive resonant passive wireless communication circuit realizes signal mixing, filtering, resonance, and electromagnetic wave emission through the receiving-end capacitive resonant circuit and the transmitting-end capacitive resonant circuit; the grid-shaped ultrasonic structure realizes sound wave excitation, energy conversion, and information transfer through piezoelectric materials and interdigital electrodes.

[0044] In another exemplary embodiment of this application, as Figure 3As shown, the receiving-end capacitance resonance circuit specifically includes: a three-terminal compound semiconductor circuit and an LC resonance circuit; the input end of the three-terminal compound semiconductor circuit is connected to the signal generating device, the input end of the LC resonance circuit is connected to the output end of the three-terminal compound semiconductor circuit, the output end of the LC resonance circuit is connected to the first interdigital electrode, the three-terminal compound semiconductor circuit is used for mixing the excitation signal, and the LC resonance circuit is used for filtering the mixed excitation signal. Due to the non-linear characteristics of the three-terminal compound semiconductor circuit, the generated signal will be mixed and a series of new frequency components will be generated. Subsequently, the LC resonance circuit will filter and select these frequency components, that is, select specific frequency components to excite resonance, and then an alternating current will be generated in the receiving-end capacitance resonance circuit. When n is greater than 1, the capacitance values of the LC resonance circuits in different bolt fastening state detection modules are different. By fixing the inductance value and changing the capacitance value, the resonance frequencies of the receiving-end capacitance resonance circuits corresponding to bolts at different positions are different. Due to the different resonance frequencies, the acoustic wave frequencies excited by the grid-shaped ultrasonic structure and the alternating voltage applied across the transmitting-end capacitance resonance circuit are also different, and frequency discrimination and bolt positioning can be achieved based on this. Specifically, assume that the connection states of bolts need to be detected at one time, and the total range of frequency change is ~ . The preset resonance frequency range corresponding to bolt is ~ . The preset resonance frequency range corresponding to bolt is ~ . The preset resonance frequency range corresponding to bolt is ~ , that is, the preset resonance frequency ranges corresponding to bolts at each position do not overlap and have a frequency difference. Then, according to the different frequency bands where the resonance frequencies corresponding to the detected bolts are located, the positions of the bolts corresponding to each resonance frequency can be distinguished.

[0045] In another exemplary embodiment of the present application, as Figure 6 shown, the transmitting-end capacitance resonance circuit further includes: a first antenna; the transmitting-end capacitance resonance circuit sends the resonance frequency to the signal receiving device through the first antenna.

[0046] In another exemplary embodiment of the present application, as Figure 4As shown, the receiving-end capacitance-resonance circuit further includes: a second antenna, a first capacitor (with a capacitance value of 100 pF), a first inductor, and a second inductor (with an inductance value of 10 mH); the excitation signal emitted by the signal generating device is transmitted to the receiving-end capacitance-resonance circuit through the second antenna. The second antenna is respectively connected to one end of the first capacitor and one end of the second inductor. One end of the second inductor is connected to VCC. The other end of the first capacitor is connected to one end of the first inductor. The other end of the first inductor is connected to the first input terminal of the three-terminal compound semiconductor circuit. The other end of the second inductor is connected to the second input terminal of the three-terminal compound semiconductor circuit. The output terminal of the three-terminal compound semiconductor circuit is connected to the input terminal of the LC resonance circuit. The output terminal of the LC resonance circuit is connected to the first interdigital electrode.

[0047] In another exemplary embodiment of the present application, as Figure 4 shown, the three-terminal compound semiconductor circuit includes: a first PMOS transistor and a second PMOS transistor; the LC resonance circuit includes: a second capacitor and a third inductor (with an inductance value of 3.9 ). The gate of the first PMOS transistor is connected to the other end of the first inductor. The source of the first PMOS transistor is grounded. The drain of the first PMOS transistor is connected to the drain of the second PMOS transistor. The gate of the second PMOS transistor is respectively connected to one end of the third inductor and one end of the second capacitor. The other end of the third inductor and the other end of the second capacitor are both grounded. The source of the second PMOS transistor is connected to the other end of the second inductor. One end and the other end of the second capacitor are connected to the first interdigital electrode. Due to the non-linear characteristics of the two PMOS transistors, a new frequency is generated, achieving the effect of mixing, and the mixing is a single input rather than multiple inputs.

[0048] In another exemplary embodiment of the present application, as Figure 7 shown, the transmitting-end capacitance-resonance circuit further includes: a third capacitor (with a capacitance value of 100 pF), a fourth inductor, a fifth inductor (with an inductance value of 10 mH), a fourth capacitor (with a capacitance value of 100 pF), and a sixth capacitor; one end of the third capacitor and one end of the sixth inductor are both connected to the second interdigital electrode. The other end of the third capacitor is connected to one end of the fourth inductor. The other end of the fourth inductor is respectively connected to the other end of the sixth inductor, one end of the mechanical variable capacitor, and one end of the fifth inductor. One end of the sixth inductor and the other end of the mechanical variable capacitor are grounded. The other end of the fifth inductor is connected to one end of the fourth capacitor. The other end of the fourth capacitor is connected to the first antenna.

[0049] In another exemplary embodiment of the present application, when n is equal to 1, the judgment host is used to determine the fastening state parameters of the bolt to be measured based on the resonance frequency of the transmitting end resonance circuit in the bolt fastening state detection module, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtain the fastening state of the bolt to be measured based on the fastening state parameters of the bolt to be measured. When n is greater than 1, the judgment host is used to determine the fastening state parameters of the bolts to be measured at each position based on the resonance frequency set, the preset resonance frequency intervals corresponding to the bolts to be measured at each position, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle, and obtain the fastening states of the bolts to be measured at each position based on the fastening state parameters of the bolts to be measured at each position; the resonance frequency set includes: the resonance frequencies of the transmitting end resonance circuits in each bolt fastening state detection module.

[0050] In another exemplary embodiment of the present application, in the early stage, the nut structure in the bolt fastening state detection module is installed on the sample bolt, and then by measuring the resonance frequency of the transmitting end resonance circuit in the bolt fastening state detection module under different bolt pre-tightening forces, the relationship curve between the resonance frequency and the bolt pre-tightening force is obtained by fitting.

[0051] In another exemplary embodiment of the present application, as Figure 2 shown, the nut is a double-layer structure, including: a lower nut body and an upper nut body, and the upper nut body is arranged above the lower nut body; the material of the lower nut body is metal, and the material of the upper nut body is a polymer composite material; the receiving end resonance circuit, the transmitting end resonance circuit, the first piezoelectric material and the second piezoelectric material are all arranged on the side wall of the upper nut body. On the surface of the polymer composite material, a resonance passive wireless communication circuit and a grid-shaped ultrasonic structure are integrated. The lower nut body can be made of high-strength alloy steel material to ensure mechanical properties and durability. The upper nut body can be made of a polymer-based composite material with excellent insulation and flexibility to protect the internal electronic components from external environmental interference.

[0052] In another exemplary embodiment of the present application, the signal generating device, the signal receiving device and the judgment host are all integrated on the fixed-point detection system at the unmanned inspection vehicle or the train storage area, and can detect the looseness of bolts of the vehicles on the return track. By integrating with the fixed-point detection system at the unmanned inspection vehicle or the train storage area, full-automatic monitoring can be realized without manual operation.

[0053] The present application has the following technical effects.

[0054] This application can achieve precise measurement of the change in pre-tightening force and the rotation angle of bolts. Traditional bolt monitoring methods usually rely on battery power or external power sources, suffering from problems such as limited battery life, high maintenance costs, and poor environmental adaptability. In this application, the receiving-end capacitive harmonic circuit generates alternating current through the resonance between the external excitation signal and its own resonance circuit, driving the grid-shaped ultrasonic structure to work; the transmitting-end capacitive harmonic circuit realizes the emission of electromagnetic waves through the dynamic tuning of the mechanical variable capacitor, thereby completing the wireless transmission of data. The resonance frequency of the transmitting-end capacitive harmonic circuit measured is transmitted to the signal receiving device through passive wireless communication technology and then to the judgment host to achieve passive, wireless, real-time, and hierarchical detection of the bolt tightening state in the rail transit industry. When this application conducts bolt tightening state detection and wireless data transmission, it does not require an external power source such as a battery for power supply. It only needs to use electromagnetic waves for long-distance excitation, eliminating the dependence on external power sources such as batteries. At the same time, this application is different in principle from existing passive detection methods. For example, the RFID gasket-type pressure sensor mainly accumulates electrical energy briefly through the internal capacitance (or other energy storage components) of the tag. When the capacitor voltage reaches the threshold, the chip inside the tag is activated, and then operations such as data decoding, frequency adjustment, and wireless transmission are carried out. However, there is no typical energy storage component inside the circuit design of this application. The existing capacitance mainly functions to change the resonance frequency and filter, which is different from the function of the capacitance in the RFID gasket-type pressure sensor. Therefore, this application can also perform passive wireless information transmission when the excitation energy is extremely low, effectively solving the problems of the RFID gasket-type pressure sensor, such as short communication distance, long excitation time, and poor communication performance in complex environments (especially metal environments). The existing bolt loosening detection methods in the rail transit industry mainly rely on manual inspections, such as using torque wrenches for regular inspections. This method not only consumes a large amount of manpower and material resources but also has the risks of missed inspections and misjudgments. Other emerging technologies such as video monitoring methods and ultrasonic detection methods, although reducing manual intervention to a certain extent, still require manual participation in data analysis or equipment operation and cannot achieve full automation. This application can send the collected resonance frequency to the judgment host in real time through the signal receiving device. The judgment host uses the judgment algorithm stored internally to analyze and process the data, and can complete the evaluation of the bolt tightening state without manual intervention. This not only greatly reduces the labor cost but also improves the detection efficiency and accuracy, and is particularly suitable for the high-intensity and high-frequency detection requirements in the rail transit industry. The passive wireless detection device for bolt tightening state with frequency-stress mapping of this application only needs to be set on the nut, avoiding the risk of structural damage caused by other devices introduced by traditional detection methods, and further enhancing the safety and reliability of the system. This application also provides an embodiment of applying the passive wireless detection device for bolt tightening state with frequency-stress mapping provided in the above embodiment to detect bolt loosening of the in-stock rail vehicles by the rail transit unmanned inspection vehicle. The specific steps are as follows, from step S1 to step S3.

[0055] Step S1: Install the passive wireless detection device for bolt fastening state with frequency-stress mapping on the nut corresponding to the bolt to be detected.

[0056] Step S2: After the rail vehicle returns to the depot, use the unmanned inspection vehicle to conduct fault troubleshooting according to the established route. A signal generating device, a signal receiving device, and a judgment host are installed on the vehicle. For the detection of the bolt connection state, the vehicle will stop at the middle position of each carriage, transmit an excitation electromagnetic wave signal to all receiving-end capacitive harmonic circuits in this carriage, and receive the echo signals transmitted by all transmitting-end capacitive harmonic circuits in this carriage, that is, the resonant frequency of the transmitting-end capacitive harmonic circuit.

[0057] Step S2-1: The signal generating device transmits an excitation electromagnetic wave signal. When this signal is loaded onto the receiving-end capacitive harmonic circuit, first, through the three-terminal compound semiconductor circuit, due to its non-linear characteristics, signal mixing will occur and a series of new frequency components will be generated; subsequently, the LC resonant circuit will filter and select these frequency components, that is, select specific frequency components to excite resonance, and then an alternating current will be generated in the receiving-end capacitive harmonic circuit.

[0058] Step S2-2: The two poles of the first interdigital electrode are connected to the above-mentioned receiving-end capacitive harmonic circuit. When the receiving-end capacitive harmonic circuit resonates, an alternating current is generated, which in turn excites an alternating electric field. Due to the existence of the alternating electric field, the first piezoelectric material laid under the first interdigital electrode undergoes the inverse piezoelectric effect and will vibrate, exciting sound waves to propagate forward along the nut surface layer. The waveform and wavelength of these sound waves are closely related to the geometric parameters of the first interdigital electrode;

[0059] Step S2-3: When the sound wave propagates along the nut surface layer to the second interdigital electrode, the second piezoelectric material undergoes the direct piezoelectric effect under the action of the sound wave, generating polarization charges and forming an alternating voltage at both ends of the second interdigital electrode. Thus, the process of energy conversion and information transmission of the interdigital electrode is completed.

[0060] Step S2-4: The two poles of the second interdigital electrode are connected to the transmitting-end capacitive harmonic circuit, that is, an alternating voltage is loaded at both ends of the transmitting-end capacitive harmonic circuit. The transmitting-end capacitive harmonic circuit contains a mechanically variable capacitor, and the capacitance value of this capacitor changes with the compressive deformation of the nut and has a linear relationship with the finger spacing of the interdigital electrode, so that the frequency of the alternating voltage loaded at both ends of the transmitting-end capacitive harmonic circuit can be made to be consistent with the resonant frequency in the circuit, thereby achieving resonance and transmitting the electromagnetic wave carrying the bolt tightening and loosening state through the first antenna.

[0061] Step S2-5: As can be seen from the foregoing analysis, the resonant frequencies of the receiving-end capacitance-resonance circuits corresponding to the bolts at different positions are different. Ultimately, it is manifested that the frequency change ranges corresponding to the bolts at different positions do not overlap and have a frequency difference, whereby the bolts at different positions can be distinguished. In addition, the unmanned inspection vehicle can detect the bolts at important positions of a whole carriage each time. In order to effectively distinguish the echo signals of the bolts at different positions, two different capacitance-resonance passive wireless communication circuits and grid-shaped ultrasonic structures are used for every two adjacent carriages. The echo frequencies of these two capacitance-resonance passive wireless communication circuits and grid-shaped ultrasonic structures are different from each other, avoiding the problems caused by mixing frequency and harmonic noise. Finally, the signal receiving device on the unmanned inspection vehicle receives the resonant frequencies corresponding to the bolts of this carriage.

[0062] Step S3: The judgment host on the unmanned inspection vehicle will process and analyze the collected resonant frequencies. Specifically, the relationship curves between the resonant frequency and the bolt pre-tightening force and between the resonant frequency and the bolt rotation angle are fitted in advance, and then the connection state of the bolt at this time is deduced based on the received resonant frequency. The bolt connection state is set to five gears, namely fully tightened, relatively tightened, relatively loose, loose and detached states. The judgment host can identify the gear of the connection state of each bolt point and display it. Thus, the passive wireless detection of the bolt connection state is completed.

[0063] The signal generating device and the signal receiving device in the passive wireless detection device for bolt tightening state with frequency-stress mapping provided in the above embodiment can also be set on the fixed-point detection system at the train depot entrance, and the bolt tightening state can be inspected when the train passes through the depot entrance.

[0064] The present application also provides a passive wireless detection method for bolt tightening state with frequency-stress mapping, which is applied to the passive wireless detection device for bolt tightening state with frequency-stress mapping. The passive wireless detection method for bolt tightening state with frequency-stress mapping includes: obtaining the resonant frequencies of the transmitting-end capacitance-resonance circuits in each bolt tightening state detection module.

[0065] Determining the tightening state parameters of the bolts to be measured at each position based on the resonant frequencies of the transmitting-end capacitance-resonance circuits in each bolt tightening state detection module, and obtaining the tightening states of the bolts to be measured at each position based on the tightening state parameters of the bolts to be measured at each position; the tightening state parameters include: pre-tightening force and rotation angle.

[0066] In another exemplary embodiment of the present application, the tightening state parameters of the bolts to be measured at each position are determined based on the resonance frequencies of the transmitting end capacitive resonance circuits in each bolt tightening state detection module, and the tightening states of the bolts to be measured at each position are obtained based on the tightening state parameters of the bolts to be measured at each position. Specifically, when n is equal to 1, the tightening state parameters of the bolt to be measured are determined based on the resonance frequency of the transmitting end capacitive resonance circuit in the bolt tightening state detection module, the curve of the resonance frequency versus the bolt pre-tightening force, and the curve of the resonance frequency versus the bolt rotation angle, and the tightening state of the bolt to be measured is obtained based on the tightening state parameters of the bolt to be measured; the curve of the resonance frequency versus the bolt pre-tightening force and the curve of the resonance frequency versus the bolt rotation angle are pre-fitted.

[0067] When n is greater than 1, the tightening state parameters of the bolts to be measured at each position are determined based on the resonance frequency set, the preset resonance frequency intervals corresponding to the bolts to be measured at each position, the curve of the resonance frequency versus the bolt pre-tightening force, and the curve of the resonance frequency versus the bolt rotation angle, and the tightening states of the bolts to be measured at each position are obtained based on the tightening state parameters of the bolts to be measured at each position; the resonance frequency set includes: the resonance frequencies of the transmitting end capacitive resonance circuits in each bolt tightening state detection module.

[0068] In another exemplary embodiment of the present application, the tightening state parameters of the bolt to be measured are determined based on the resonance frequency of the transmitting end capacitive resonance circuit in the bolt tightening state detection module, the curve of the resonance frequency versus the bolt pre-tightening force, and the curve of the resonance frequency versus the bolt rotation angle, and the tightening state of the bolt to be measured is obtained based on the tightening state parameters of the bolt to be measured. Specifically, the pre-tightening force of the bolt to be measured is determined based on the resonance frequency of the transmitting end capacitive resonance circuit in the bolt tightening state detection module and the curve of the resonance frequency versus the bolt pre-tightening force.

[0069] The rotation angle of the bolt to be measured is determined based on the resonance frequency of the transmitting end capacitive resonance circuit in the bolt tightening state detection module and the curve of the resonance frequency versus the bolt rotation angle.

[0070] The tightening state of the bolt to be measured is determined according to the pre-tightening force and the rotation angle of the bolt to be measured.

[0071] In another exemplary embodiment of the present application, the tightening state parameters of the bolts to be measured at each position are determined based on the resonance frequency set, the preset resonance frequency intervals corresponding to the bolts to be measured at each position, the curve of the resonance frequency versus the bolt pre-tightening force, and the curve of the resonance frequency versus the bolt rotation angle, and the tightening states of the bolts to be measured at each position are obtained based on the tightening state parameters of the bolts to be measured at each position. Specifically, based on the resonance frequency set and the preset resonance frequency intervals corresponding to the bolts to be measured at each position, the positions of the bolts to be measured corresponding to each resonance frequency in the resonance frequency set are determined.

[0072] Determine the fastening state of the bolt to be measured corresponding to each resonance frequency in the resonance frequency set according to the resonance frequency set, the relationship curve between the resonance frequency and the bolt pre-tightening force, and the relationship curve between the resonance frequency and the bolt rotation angle.

[0073] Based on the fastening state of the bolt to be measured corresponding to each resonance frequency and the position of the bolt to be measured corresponding to each resonance frequency, determine the fastening state of the bolt to be measured at each position.

[0074] In another exemplary embodiment of the present application, based on the resonance frequency set and the preset resonance frequency intervals corresponding to the bolts to be measured at each position, determine the positions of the bolts to be measured corresponding to each resonance frequency in the resonance frequency set, specifically including: for any resonance frequency in the resonance frequency set, determine that the position of the bolt to be measured corresponding to the preset resonance frequency interval where the resonance frequency is located is the position of the bolt to be measured corresponding to the resonance frequency.

[0075] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0076] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A frequency-stress mapping passive wireless detection device for bolt tightening status, characterized in that: The bolt tightening state passive wireless detection device for frequency-stress mapping is used to simultaneously measure the tightening state of the bolts to be tested at n positions, where n is a positive integer greater than or equal to 1, and comprises: A signal generating device, a signal receiving device, a judging host and n bolt tightening state detecting modules; the n bolt tightening state detecting modules are arranged in one-to-one correspondence with the bolts to be tested at n positions; the signal receiving device is connected to the judging host for communication; The bolt tightening state detection module includes: a nut, a receiving end capacitance resonant circuit, a transmitting end capacitance resonant circuit, a first interdigital electrode, a second interdigital electrode, a first piezoelectric material and a second piezoelectric material; the nut is arranged on the bolt to be tested; the receiving end capacitance resonant circuit, the transmitting end capacitance resonant circuit, the first piezoelectric material and the second piezoelectric material are all arranged on the side wall of the nut; the first interdigital electrode is arranged on the surface of the first piezoelectric material, and the second interdigital electrode is arranged on the surface of the second piezoelectric material; the transmitting end capacitance resonant circuit includes a mechanical variable capacitor; two plates of the mechanical variable capacitor are arranged along the axial direction of the nut; adjacent interdigital electrodes of the first interdigital electrode are arranged along the axial direction of the nut; adjacent interdigital electrodes of the second interdigital electrode are arranged along the axial direction of the nut; the first interdigital electrode and the second interdigital electrode are symmetrical in the axial direction of the nut; the first interdigital electrode is electrically connected to the receiving end capacitance resonant circuit, and the second interdigital electrode is electrically connected to the transmitting end capacitance resonant circuit; The signal generating device is used to transmit an excitation signal to the receiving end capacitive harmonic circuit in each bolt tightening state detection module, and the receiving end capacitive harmonic circuit is used to mix and filter the excitation signal so that the receiving end capacitive harmonic circuit resonates and generates an alternating current; the signal receiving device is used to obtain the resonant frequency of the transmitting end capacitive harmonic circuit in each bolt tightening state detection module, and the judging host is used to determine the tightening state parameters of the bolts to be tested at each position according to the resonant frequency of the transmitting end capacitive harmonic circuit in each bolt tightening state detection module, and obtain the tightening state of the bolts to be tested at each position based on the tightening state parameters of the bolts to be tested at each position; the tightening state parameters include: pre-tightening force and rotation angle, when n is greater than 1, the resonant frequencies of the alternating currents generated by the receiving end capacitive harmonic circuits in different bolt tightening state detection modules are different.

2. The passive wireless detection device for bolt tightening state based on frequency-stress mapping according to claim 1 is characterized in that: The receiving end capacitance resonant circuit specifically comprises: A three-terminal composite semiconductor circuit and an LC resonant circuit; the input end of the three-terminal composite semiconductor circuit is connected to the signal generating device, the input end of the LC resonant circuit is connected to the output end of the three-terminal composite semiconductor circuit, the output end of the LC resonant circuit is connected to the first interdigitated electrode, the three-terminal composite semiconductor circuit is used to mix the excitation signal, and the LC resonant circuit is used to filter the mixed excitation signal. When n is greater than 1, the capacitance values ​​of the LC resonant circuits in different bolt tightening status detection modules are different.

3. The passive wireless detection device for bolt tightening state based on frequency-stress mapping according to claim 1, characterized in that: When n is equal to 1, the judgment host is used to determine the tightening state parameters of the bolt to be tested based on the resonant frequency of the transmitting end capacitor harmonic circuit in the bolt tightening state detection module, the resonant frequency and bolt preload relationship curve, and the resonant frequency and bolt rotation angle relationship curve, and obtain the tightening state of the bolt to be tested based on the tightening state parameters of the bolt to be tested. When n is greater than 1, the judgment host is used to determine the tightening state parameters of the bolt to be tested at each position based on the resonant frequency set, the preset resonant frequency range corresponding to the bolt to be tested at each position, the resonant frequency and bolt preload relationship curve, and the resonant frequency and bolt rotation angle relationship curve, and obtain the tightening state of the bolt to be tested at each position based on the tightening state parameters of the bolt to be tested at each position; the resonant frequency set includes: the resonant frequency of the transmitting end capacitor harmonic circuit in each bolt tightening state detection module.

4. The frequency-stress mapping passive wireless detection device for bolt tightening status according to claim 1, characterized in that: The nut includes: a lower nut body and an upper nut body; the upper nut body is arranged above the lower nut body; the material of the lower nut body is metal, and the material of the upper nut body is a polymer composite material; the receiving end capacitance harmonic circuit, the transmitting end capacitance harmonic circuit, the first piezoelectric material and the second piezoelectric material are all arranged on the side wall of the upper nut body.

5. The frequency-stress mapping passive wireless detection device for bolt tightening status according to claim 1, characterized in that: The signal generating device, the signal receiving device and the judgment host are all integrated into a fixed-point detection system at an unmanned inspection vehicle or a train entry point.

6. A method for passive wireless detection of bolt tightening status based on frequency-stress mapping, characterized in that: The passive wireless detection device for bolt tightening state of frequency-stress mapping according to any one of claims 1 to 5 above, the passive wireless detection method for bolt tightening state of frequency-stress mapping comprising: Obtaining the resonant frequency of the transmitting end capacitor resonant circuit in each bolt tightening state detection module; The tightening state parameters of the bolts to be tested at each position are determined based on the resonant frequency of the transmitting end capacitor resonant circuit in each bolt tightening state detection module, and the tightening state of the bolts to be tested at each position is obtained based on the tightening state parameters of the bolts to be tested at each position; the tightening state parameters include: pre-tightening force and rotation angle.

7. The method for passive wireless detection of bolt tightening status based on frequency-stress mapping according to claim 6, characterized in that: Determining the tightening state parameters of the bolts to be tested at each position based on the resonant frequency of the transmitting end capacitor resonant circuit in each bolt tightening state detection module, and obtaining the tightening state of the bolts to be tested at each position based on the tightening state parameters of the bolts to be tested at each position, specifically includes: When n is equal to 1, the tightening state parameters of the bolt to be tested are determined based on the resonant frequency of the transmitting end capacitor resonant circuit in the bolt tightening state detection module, the relationship curve between the resonant frequency and the bolt preload force, and the relationship curve between the resonant frequency and the bolt rotation angle, and the tightening state of the bolt to be tested is obtained based on the tightening state parameters of the bolt to be tested; When n is greater than 1, based on the resonant frequency set, the preset resonant frequency range corresponding to the bolts to be tested at each position, the resonant frequency and bolt preload relationship curve, and the resonant frequency and bolt rotation angle relationship curve, the tightening state parameters of the bolts to be tested at each position are determined, and the tightening state of the bolts to be tested at each position is obtained based on the tightening state parameters of the bolts to be tested at each position; the resonant frequency set includes: the resonant frequency of the transmitting end capacitor resonant circuit in each bolt tightening state detection module.

8. The method for passive wireless detection of bolt tightening status based on frequency-stress mapping according to claim 7, characterized in that: The tightening state parameters of the bolt to be tested are determined based on the resonant frequency of the transmitting end capacitor resonant circuit in the bolt tightening state detection module, the relationship curve between the resonant frequency and the bolt preload force, and the relationship curve between the resonant frequency and the bolt rotation angle, and the tightening state parameters of the bolt to be tested are obtained based on the tightening state parameters of the bolt to be tested, specifically including: Determine the preload force of the bolt to be tested based on the resonant frequency of the transmitting end capacitor resonant circuit in the bolt tightening state detection module and the relationship curve between the resonant frequency and the bolt preload force; Determine the rotation angle of the bolt to be tested based on the resonant frequency of the transmitting end capacitor resonant circuit in the bolt tightening state detection module and the relationship curve between the resonant frequency and the bolt rotation angle; The tightening state of the bolt to be tested is determined according to the preload force and rotation angle of the bolt to be tested.

9. The method for passive wireless detection of bolt tightening status based on frequency-stress mapping according to claim 7, characterized in that: Based on the resonant frequency set, the preset resonant frequency range corresponding to the bolts to be tested at each position, the resonant frequency and bolt preload relationship curve, and the resonant frequency and bolt rotation angle relationship curve, the tightening state parameters of the bolts to be tested at each position are determined, and the tightening state of the bolts to be tested at each position is obtained based on the tightening state parameters of the bolts to be tested at each position, specifically including: Based on the resonant frequency set and the preset resonant frequency intervals corresponding to the bolts to be tested at each position, determining the position of the bolt to be tested corresponding to each resonant frequency in the resonant frequency set; Determine the tightening state of the bolt to be tested corresponding to each resonant frequency in the resonant frequency set according to the resonant frequency set, the resonant frequency and bolt preload relationship curve, and the resonant frequency and bolt rotation angle relationship curve; The tightening state of the bolt to be measured at each position is determined based on the tightening state of the bolt to be measured corresponding to each resonant frequency and the position of the bolt to be measured corresponding to each resonant frequency.

10. The method for passive wireless detection of bolt tightening status based on frequency-stress mapping according to claim 9, characterized in that: Based on the resonant frequency set and the preset resonant frequency intervals corresponding to the bolts to be tested at each position, determining the position of the bolts to be tested corresponding to each resonant frequency in the resonant frequency set specifically includes: For any resonant frequency in the resonant frequency set, the position of the bolt to be measured corresponding to the preset resonant frequency interval where the resonant frequency is located is determined as the position of the bolt to be measured corresponding to the resonant frequency.

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