Bolt looseness monitoring device, system and method based on U-shaped resonator

Abstract

The invention belongs to the technical field of testing, and relates to a bolt looseness monitoring device, system and method based on a U-shaped resonator. The monitoring device comprises a first assembly, a second assembly and a third assembly, wherein the first assembly is fixedly arranged on a connecting component; the second assembly is stacked above the first assembly; the second assembly and the third assembly are fixedly connected and can rotate along with the nut. When the nut rotates, the overlapping length between the U-shaped resonator of the first assembly and the sub-patch of the second assembly is changed, so that the effective electrical length of the combined U-shaped resonator is changed, the resonant frequency of the combined U-shaped resonator is changed, and the rotation looseness of the bolt is detected. The monitoring device can sense the looseness of the bolt, through the arrangement of the first assembly and the second assembly, the drift distance of the resonant frequency of the monitoring device and the change size of the rotation angle of the nut have a clear relation within a fixed range, the rotation angle of the nut is calculated accordingly, and wireless monitoring of the looseness of the bolt is achieved.

Description

Technical Field

[0001] The invention belongs to the field of testing technology, and in particular relates to a bolt loosening monitoring device, system and method based on a U-shaped resonator. Background Art

[0002] Bolts are widely used in component connections in various fields. Their high strength and detachable features make them more widely applicable. However, bolts are prone to loosening under long-term loads, which can pose a serious safety hazard to the structure. Therefore, for structures connected by bolts, it is necessary to conduct regular bolt monitoring to avoid structural damage caused by loose bolts.

[0003] At present, the commonly used bolt monitoring technologies are: bolt loosening monitoring method based on piezoelectric admittance and strain gauge electrical measurement method. The bolt loosening monitoring method based on piezoelectric admittance pastes a piezoelectric sensor on the bolt, and by measuring the peak frequency change in the piezoelectric admittance diagram, it can be judged whether the bolt is loose. However, the piezoelectric sensor needs to be excited by a wire and requires an expensive high-precision impedance analyzer, which is difficult to be widely used in engineering practice. The strain gauge electrical measurement method accurately measures the axial force of the bolt by measuring the strain of the bolt screw, but the axial force of the bolt is not large, which makes its measurement accuracy low, and it is difficult to be widely used due to the limitations of installation conditions. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a bolt loosening monitoring device, system and method based on a U-shaped resonator with high accuracy, convenient detection and wide application range.

[0005] The objective of the present invention can be achieved through the following technical scheme: a bolt loosening monitoring device based on a U-shaped resonator, comprising a first component, a second component and a third component, wherein the first component is fixedly arranged on a connecting member; the second component is stacked and placed above the first component; the second component and the third component are fixedly connected, and both can rotate with the nut; wherein the first component is composed of a receiving antenna, a transmitting antenna and a dielectric substrate covering an arc-shaped microstrip line and a U-shaped resonator, and the second component is an arc-shaped dielectric substrate covering a sub-patch; the U-shaped resonator of the first component and the sub-patch of the second component are located in the same plane, and together constitute a combined U-shaped resonator; when the nut is rotated and loosened, the overlapping length between the U-shaped resonator of the first component and the sub-patch of the second component changes, resulting in a change in the effective electrical length of the combined U-shaped resonator, so that its resonant frequency changes, thereby realizing the detection of the rotational loosening of the bolt.

[0006] Preferably, the U-shaped resonator is electromagnetically coupled near the arc-shaped microstrip line, and when current flows through the arc-shaped microstrip line, the U-shaped resonator generates electromagnetic resonance to dissipate the energy of the electromagnetic signal at its resonant frequency.

[0007] Preferably, the inner edge of the transparent acrylic plate of the third component is fixed to the outer edge of the nut, and the outer edge of the transparent acrylic plate is fixedly connected to the inner edge of the arc-shaped dielectric substrate of the second component.

[0008] Preferably, the lower surface of the dielectric substrate is covered with brass.

[0009] Preferably, the receiving antenna and the transmitting antenna are selected to be any single linearly polarized broadband antenna, and the positions of the receiving antenna and the transmitting antenna are kept orthogonal.

[0010] Preferably, the arc-shaped microstrip line, the U-shaped resonator and the sub-patch are made of brass. Preferably, the material of the dielectric substrate and the curved dielectric substrate is RT5880.

[0011] The present invention further provides a bolt loosening monitoring system based on a U-shaped resonator, which includes a bolt loosening monitoring device and a reader based on a U-shaped resonator that are communicatively connected to each other. The reader is used to transmit electromagnetic wave signals to the monitoring device and read the retransmitted signals of the monitoring device and perform data processing to extract monitoring information. It includes a wireless transceiver module, a control module, a modulation and demodulation module and a digital processing module.

[0012] The present invention also provides a bolt loosening monitoring method based on a U-shaped resonator, using the system, comprising the following steps: (1) The reader transmits electromagnetic wave signals to the receiving antenna; (2) The receiving antenna captures the electromagnetic wave energy and generates electromagnetic resonance, generating surface current, which flows to the arc microstrip line through the coaxial line. When the signal frequency matches the resonant frequency of the combined U-shaped resonator, the combined U-shaped resonator generates electromagnetic resonance to dissipate this part of the signal energy, while the signals of other frequencies are not affected and flow to the transmitting antenna through the arc microstrip line. (3) The transmitting antenna generates electromagnetic resonance and retransmits the remaining signal to the reader; (4) The reader can obtain the resonant frequency information of the monitoring device by detecting the frequency position corresponding to the notch in the received signal. Then, based on the relationship between the resonant frequency drift of the monitoring device obtained from the experiment and the change in the relative angle between the U-shaped resonator and the sub-patch, the rotation angle of the nut is obtained to determine whether the bolt has been loosened by rotation.

[0013] Compared with the prior art, the present invention has the following advantages: 1) The monitoring device of the present invention can sense the change in the rotation angle of the nut. By setting the first component and the second component, the drift of the resonant frequency and the change in the rotation angle of the nut have a clear relationship within a fixed range; 2) The reader of the present invention can wirelessly detect the drift of the resonant frequency of the monitoring device, and thereby calculate the rotation angle of the nut caused by the loosening of the bolt, thereby realizing wireless monitoring of the loosening of the bolt; 3) The monitoring device of the present invention uses a cross-polarized broadband antenna to receive and retransmit signals respectively, which can avoid interference from environmental reflection signals and improve the accuracy and stability of the wireless reading of the monitoring device; 4) When using the system of the present invention, there is no need to modify the bolts during installation, and the system can be directly installed on the existing bolts, which is economical and practical and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic structural diagram of a bolt loosening monitoring device based on a U-shaped resonator provided in Example 1 of the present invention; Figure 2 is a schematic structural diagram of a first component; Figure 3 is a schematic structural diagram of a second component; Figure 4 is a schematic structural diagram of a third component; Figure 5 A schematic diagram of the structure of a bolt loosening monitoring system based on a U-shaped resonator provided in Example 2 of the present invention; In the figure, 1. nut; 2. curved dielectric substrate; 3. transparent acrylic plate; 4. dielectric substrate; 5. curved microstrip line; 6. transmitting antenna; 7. receiving antenna; 8. connecting component; 9. reader; 10. bolt; 11. U-shaped resonator; 12. sub-patch. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below through the accompanying drawings and embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the scope of the present invention.

[0016] Embodiment 1 This embodiment provides a bolt loosening monitoring device based on a U-shaped resonator. The device is used to detect whether a bolt 10 connecting two connecting members 8 is loosened by rotation. Figure 1 As shown, the device is arranged on the connecting member 8 and sleeved on the outer edge of the bolt 10, and includes a first component, a second component and a third component.

[0017] The first component is fixedly arranged on the connecting member 8, such as Figure 2As shown, the first component is composed of a receiving antenna 7, a transmitting antenna 6, and a dielectric substrate 4 covering a curved microstrip line 5 and a U-shaped resonator 11. The U-shaped resonator 11 on the upper surface of the dielectric substrate 4 in the first component is electromagnetically coupled near the curved microstrip line 5. When a current flows through the curved microstrip line 5, the U-shaped resonator 11 will generate electromagnetic resonance to dissipate the energy of the electromagnetic signal at its resonant frequency.

[0018] like Figure 3 As shown, the second component is an arc-shaped dielectric substrate 2 covering the sub-patch 12. The second component is stacked and placed on top of the first component, ensuring that the U-shaped resonator 11 of the first component and the sub-patch 12 of the second component are located in the same plane. When there is an overlapping length between the two, current can flow between the two. Therefore, the U-shaped resonator 11 of the first component and the sub-patch 12 of the second component together constitute a combined U-shaped resonator inside the device to resonate and consume energy.

[0019] like Figure 4 As shown, the third component is a transparent acrylic plate 3 for being nested in the outer edge of the nut 1, and the second component and the third component are fixedly connected. The inner edge opening of the transparent acrylic plate 3 of the third component cooperates with the outer edge of the nut 1 of the bolt 10, and can be stably nested and fixed in the outer edge of the nut 1 through adhesives such as glue, and the inner edge of the arc-shaped dielectric substrate 2 of the second component is fixedly connected to the outer edge of the transparent acrylic plate 3. Both can rotate with the nut 1. When the nut 1 rotates loose, it drives the second component and the third component to rotate together, while the first component remains fixed. Therefore, the second component rotates relative to the first component, so that the overlapping length between the U-shaped resonator 11 of the first component and the sub-patch 12 of the second component changes, resulting in a change in the effective electrical length of the internal combined U-shaped resonator, which changes the resonant frequency of the sensor, thereby realizing the detection of the loosening of the bolt rotation.

[0020] When the bolt 10 is not rotated and loosened, the U-shaped resonator 11 of the first component and the sub-patch 12 of the second component are tightly fitted but do not overlap, that is, the effective electrical length of the combined U-shaped resonator in the initial position is the longest; when the bolt 10 is rotated and loosened, it drives the third component and the second component to rotate together, that is, the arc-shaped dielectric substrate 2 of the second component rotates relative to the dielectric substrate 4 of the first component, the position of the sub-patch 12 rotates relative to the U-shaped resonator 11, the overlapping length of the sub-patch 12 relative to the U-shaped resonator 11 changes, the effective electrical length of the combined U-shaped resonator changes, resulting in a change in the resonant frequency of the combined U-shaped resonator, thereby realizing the detection of the rotational looseness of the bolt.

[0021] The materials of the arc-shaped microstrip line 5, the U-shaped resonator 11 and the sub-patch 12 are all brass. The lower surface of the dielectric substrate 4 of the first component is covered with brass. The materials of the dielectric substrate 4 and the arc-shaped dielectric substrate 2 are RT5880 (RT5880 usually refers to a high-frequency circuit material produced by Rogers or a printed circuit board (PCB) made based on this material).

[0022] The receiving antenna 7 and transmitting antenna 6 of the first component are circular monopole broadband antennas, which can only transmit and receive linearly polarized electromagnetic waves. During the installation process, the positions of the receiving antenna 7 and the transmitting antenna 6 must remain orthogonal to achieve the intersection of the polarization directions of the received signal and the retransmitted signal. The receiving antenna 7 and the transmitting antenna 6 can use any single linearly polarized broadband antenna, and are not limited to circular monopole broadband antennas.

[0023] Embodiment 2 This embodiment provides a bolt loosening monitoring system based on a U-shaped resonator, comprising a bolt loosening monitoring device based on a U-shaped resonator as provided in Embodiment 1 and a reader 9 which are connected to each other for communication, wherein the reader 9 is used to read the retransmitted signal of the monitoring device and perform data processing to extract the monitoring information. Figure 5 As shown, the reader 9 includes: a wireless transceiver module, a control module, a modulation and demodulation module and a digital processing module. The wireless transceiver module is used to transmit electromagnetic wave signals to the monitoring device and receive retransmission signals from the monitoring device. The control module is used to control the generation of signals; the modulation and demodulation module is used to demodulate the received retransmission signals to obtain the resonant frequency; the digital processing module is used to calculate the rotation angle of the nut from the obtained resonant frequency shift.

[0024] When the system is working, the reader 9 transmits an electromagnetic wave signal to the receiving antenna 7 of the monitoring device, and then the receiving antenna 7 captures the electromagnetic wave energy to produce electromagnetic resonance, generate surface current, and flow to the arc microstrip line 5 through the coaxial line. When the signal frequency matches the resonant frequency of the combined U-shaped resonator, the combined U-shaped resonator will produce electromagnetic resonance to dissipate this part of the signal energy, while the signals of the remaining frequencies are not affected and flow to the transmitting antenna 6 through the arc microstrip line 5. Finally, the transmitting antenna 6 produces electromagnetic resonance to retransmit the remaining signal to the reader 9; the polarization directions of the query signal emitted by the reader and the signal carrying the monitoring information retransmitted by the monitoring device remain in a crossed state, and the polarization direction of the environmental reflection signal is consistent with that of the query signal, so the environmental reflection signal will not cause any interference to the retransmitted signal of the monitoring device, thereby improving the accuracy and stability of the reader during wireless reading. The reader can obtain the resonant frequency information of the monitoring device by detecting the frequency position corresponding to the notch in the received signal, and then obtain the rotation angle of the nut 1 based on the influence relationship between the resonant frequency drift of the monitoring device and the change in the relative angle between the U-shaped resonator 11 and the sub-patch 12 obtained from the experiment, and judge whether the bolt 10 is loosened by rotation.

[0025] The specific calculation process is as follows: Assume that the total length of the U-shaped resonator on the upper surface of the first component is , the total length of the sub-patch on the lower surface of the second component is In the initial state, the two are closely fitted but there is no overlapping length, and the total length of the combined U-shaped resonator is , at this time the resonant frequency of the monitoring device can be expressed as: (1); in, is the speed of light, is the relative dielectric constant of the dielectric substrate.

[0026] When the bolt is loosened and the nut is turned, the U-shaped resonator on the upper surface of the first component and the sub-patch on the lower surface of the second component overlap, and the overlapping length is expressed as , the total length of the combined U-shaped resonator is , at this time the resonant frequency of the monitoring device can be expressed as: (2).

[0027] The shift in resonant frequency can be expressed as: (3).

[0028] Combining equations (1), (2), and (3), the overlap length can be calculated from the resonant frequency offset. Assume that the distance from the center of the sub-patch to the center of the bolt is , then the nut rotation angle can be approximately expressed as: (4).

[0029] This is the angle at which the nut rotates when the bolt is loosened.

Claims

1. A bolt loosening monitoring device based on a U-shaped resonator, characterized in that: The invention comprises a first component, a second component and a third component, wherein the first component is fixedly arranged on a connecting member; the second component is stacked and placed above the first component; the second component and the third component are fixedly connected, and both can rotate with the nut; wherein the first component is composed of a receiving antenna, a transmitting antenna and a dielectric substrate with an arc-shaped microstrip line and a U-shaped resonator on top, and the second component is an arc-shaped dielectric substrate with a sub-patch on the bottom; the U-shaped resonator of the first component and the sub-patch of the second component are located in the same plane, and together constitute a combined U-shaped resonator; when the nut is rotated and loosened, the overlapping length between the U-shaped resonator of the first component and the sub-patch of the second component changes, resulting in a change in the effective electrical length of the combined U-shaped resonator, so that its resonant frequency changes, thereby realizing the detection of the loosening of the bolt rotation.

2. The bolt loosening monitoring device based on a U-shaped resonator according to claim 1 is characterized in that: The U-shaped resonator is electromagnetically coupled near the arc-shaped microstrip line. When current flows through the arc-shaped microstrip line, the U-shaped resonator generates electromagnetic resonance to dissipate the energy of the electromagnetic signal at its resonance frequency.

3. The bolt loosening monitoring device based on a U-shaped resonator according to claim 1 is characterized in that: The inner edge of the transparent acrylic plate of the third component is fixed to the outer edge of the nut, and the outer edge of the transparent acrylic plate is fixedly connected to the inner edge of the arc-shaped dielectric substrate of the second component.

4. The bolt loosening monitoring device based on a U-shaped resonator according to claim 1 is characterized in that: The lower surface of the dielectric substrate is covered with brass.

5. The bolt loosening monitoring device based on a U-shaped resonator according to claim 1 is characterized in that: The receiving antenna and the transmitting antenna are selected to be any single linearly polarized broadband antenna, and the positions of the receiving antenna and the transmitting antenna are kept orthogonal.

6. The bolt loosening monitoring device based on a U-shaped resonator according to any one of claims 1 to 5, characterized in that: The materials of the arc-shaped microstrip line, the U-shaped resonator and the sub-patch are all brass.

7. The bolt loosening monitoring device based on a U-shaped resonator according to any one of claims 1 to 5, characterized in that: The material of the dielectric substrate and the curved dielectric substrate is RT5880.

8. A bolt loosening monitoring system based on a U-shaped resonator, characterized in that: It comprises a bolt loosening monitoring device based on a U-shaped resonator as described in any one of claims 1 to 5 and a reader which are communicatively connected to each other, wherein the reader is used to transmit electromagnetic wave signals to the monitoring device and read the retransmitted signals of the monitoring device and perform data processing to extract monitoring information, and it comprises a wireless transceiver module, a control module, a modulation and demodulation module and a digital processing module.

9. A bolt loosening monitoring method based on a U-shaped resonator, characterized in that: Utilizing the system as claimed in claim 8, comprising the steps of: (1) The reader transmits electromagnetic wave signals to the receiving antenna; (2) The receiving antenna captures the electromagnetic wave energy and generates electromagnetic resonance, generating surface current, which flows to the arc microstrip line through the coaxial line. When the signal frequency matches the resonant frequency of the combined U-shaped resonator, the combined U-shaped resonator generates electromagnetic resonance to dissipate this part of the signal energy, while the signals of other frequencies are not affected and flow to the transmitting antenna through the arc microstrip line. (3) The transmitting antenna generates electromagnetic resonance and retransmits the remaining signal to the reader; (4) The reader can obtain the resonant frequency information of the monitoring device by detecting the frequency position corresponding to the notch in the received signal. Then, based on the relationship between the resonant frequency drift of the monitoring device obtained from the experiment and the change in the relative angle between the U-shaped resonator and the sub-patch, the rotation angle of the nut is obtained to determine whether the bolt has been loosened by rotation.

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