A bolt loosening sensing device and method

Abstract

This invention relates to a bolt loosening sensing device and method. The device is used to detect the deformation of a bolt with an opening. The sensing device includes an RFID tag with a chip on one side. An accessory is connected to the bolt with an opening via a first connecting rod and a second connecting rod. The RFID tag is wirelessly connected to a reader. The telescopic rod consists of a main body, a metal head, and a short tube. One end of the main body is connected to the metal head. The main body is placed in the short tube and inserted into an opening in a substrate. The metal head is positioned above the cut-off point of a microstrip feed line, without contacting the microstrip feed line. A hole is drilled at the center of the bolt, forming a closed groove filled with incompressible liquid. The other end of the main body is inserted into the incompressible liquid, and the short tube is fixed to the top of the closed groove. Compared with the prior art, this invention enables timely detection of the loosening of a bolt in the overall structure while ensuring the strength of the bolt.

Description

Technical Field

[0001] This invention relates to the field of bolt loosening detection, and in particular to a bolt loosening sensing device and method. Background Technology

[0002] Bolted connections are the most widely used connection method in engineering practice, transmitting forces between components. Bolts can loosen under the impact of cyclic loads and forced vibrations. However, for bolts operating in harsh environments, their tightness and fatigue damage are often difficult to assess directly, or their health status is frequently overlooked. To avoid the catastrophic consequences of bolt loosening, it is necessary to conduct bolt loosening detection to understand the bolt condition in a timely manner and minimize the occurrence of accidents.

[0003] Currently, bolt loosening detection methods are mainly divided into three categories: vibration-based, electromechanical impedance-based, and guided wave-based detection technologies. Vibration-based bolt detection technology determines the bolt connection status by extracting changes in the characteristic frequencies, transfer functions, power spectra, and other dynamic characteristics of the overall structure before and after bolt loosening. However, an assembled structure typically contains a large number of bolted connections, and localized bolt loosening does not cause changes in the overall dynamic characteristics of the structure. This means that vibration-based bolt loosening monitoring technology cannot make timely judgments about localized bolt loosening. Electromechanical impedance-based bolt loosening detection technology determines the bolt preload by detecting changes in the mechanical impedance of the bolt connection. In this method, a piezoelectric sensor (PZT) is usually attached close to the bolt connection. Due to the coupling between the PZT's impedance and mechanical impedance, changes in impedance can be detected to determine changes in bolt preload. However, the detection range of this technology is limited to the vicinity of the piezoelectric sensor and requires an expensive, high-precision impedance analyzer, which limits its practical application. Waveguide-based bolt loosening detection technology determines the bolt connection status by measuring the change in the propagation time of ultrasonic waves within the bolt or the change in the transmitted wave energy of ultrasonic guided waves at the connection surface of the connected components. It is an effective non-destructive testing method. However, this method has high requirements for measuring equipment and is difficult to apply on a large scale.

[0004] CN113125132B discloses a bolt loosening sensing device, system, and method based on a double-layer substrate patch antenna. The lower component can move along the bolt axial direction as the bolt length changes through the assembly unit. The open-hole bolt used in this solution requires through holes, resulting in weak bolt strength.

[0005] In summary, existing technologies are insufficient for timely judgment of bolt loosening in local locations, and cannot detect the loosening of a bolt in the overall structure in a timely manner. Furthermore, they cannot overcome the potential impact of through holes on loosening detection. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art by providing a bolt loosening sensing device and method, which enables timely detection of the loosening of a bolt in the overall structure while ensuring the strength of the bolt.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A bolt loosening sensing device is provided for detecting the deformation of a bolt with an opening. The sensing device includes an RFID tag with a chip on one side. The RFID tag is inserted into an accessory and connected to one end of a telescopic rod. The other end of the telescopic rod is inserted into the bolt with an opening. The accessory is connected to the bolt with an opening via a first connecting rod and a second connecting rod. The RFID tag is wirelessly connected to a reader.

[0009] The RFID tag also includes a substrate, a ring patch, and a microstrip feed line. The two ends of the microstrip feed line are connected to the chip and the ring patch, respectively. The ring patch and the chip are placed on the upper surface of the substrate. A hole is opened at the center of the substrate, which passes through the substrate and cuts off the middle of the microstrip feed line. The substrate, the microstrip feed line, and the chip form a patch antenna.

[0010] The telescopic rod consists of a main body, a metal head, and a short tube. One end of the main body is connected to the metal head. The main body is placed inside the short tube and fits into the opening in the substrate. The metal head is positioned above the cut-off point of the microstrip feed line and does not contact the microstrip feed line.

[0011] A hole is drilled at the center of the bolt to form a closed groove, which is filled with incompressible liquid. The other end of the main body of the rod is inserted into the incompressible liquid, and the short tube is fixed to the top of the closed groove.

[0012] Furthermore, the hole in the substrate is a circular hole, and the radius of the circular hole is larger than the cross-sectional radius of the main body of the rod.

[0013] Furthermore, the hole made by the piercing bolt is a round hole, and the diameter of the round hole is the outer diameter of the short pipe.

[0014] Furthermore, one end of the first connecting rod and one end of the second connecting rod are fixed to the perforated bolt, and the other ends of the first connecting rod and the other ends of the second connecting rod are connected to the lower surface of the accessory.

[0015] Furthermore, the side of the RFID tag has three notches that correspond to the protrusions of the accessory, and the RFID tag is inserted into the accessory through the protrusions and notches.

[0016] Furthermore, the microstrip feeder wire and metal head are made of brass, the substrate and rod body are made of FR4, and the short tube is made of resin.

[0017] In another aspect, the present invention provides a bolt loosening sensing method, employing a bolt loosening sensing device as described in any one of claims 1 to 6, the method comprising the following steps:

[0018] S1. The reader of the device sends modulated first electromagnetic wave signals to the RFID tag at different frequencies. When the power of the first electromagnetic wave signal received by the RFID tag reaches a threshold, the chip of the RFID tag is activated.

[0019] S2. After activation, the patch antenna in the RFID tag generates current and emits a second electromagnetic wave signal carrying the tag number and location information.

[0020] S3. The second electromagnetic wave signal with the tag number and location information is received and processed by the reader to obtain information about the position and status of the bolt.

[0021] When the bolt is under stress, the patch antenna switches between a closed circuit state and an open circuit state.

[0022] Furthermore, the second electromagnetic wave signal includes a resonant frequency. When the patch antenna is in a closed state, the reader detects the resonant frequency; when the patch antenna is in an open state, the reader cannot detect the resonant frequency.

[0023] Furthermore, the reader obtains information about the bolt's state based on the resonant frequency, which is information about the change in the bolt's tightness.

[0024] Furthermore, when the bolt with the hole is subjected to force, it causes a change in the volume of the incompressible liquid, and this change in volume is converted into a change in the state of the patch antenna through the telescopic rod.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The bolt loosening sensing device of the present invention utilizes the resonant characteristics of a double-layer substrate patch antenna. The upper patch, the ground plane, and the dielectric between them form a resonant system, which is connected to the bolt screw through an assembly unit. The lower component is displaced as the bolt length changes. When the gap between the upper and lower substrates is changed, the effective dielectric constant of the patch antenna changes, thereby causing the antenna resonant frequency to drift, thus realizing the detection of the bolt working state. The material is simple and the cost is lower. It can be designed and built as a prefabricated device along with the structure to build a monitoring network. At the same time, it adopts RFID technology, which can be activated by electromagnetic waves to make it work without the need for an additional power supply, realizing the passive nature of the sensor and having a wide range of applications.

[0027] (2) In this invention, when the bolt preload changes, the bolt strain is converted into liquid deformation, which will further amplify the deformation and produce a more obvious resonant frequency drift. The amount of resonant frequency drift of the wireless detection antenna is realized, and the connection status of the bolt is calculated. The resonant frequency of the antenna is used as a parameter to judge the bolt status. The influence of factors such as distance and environmental noise on this parameter can be ignored, which increases the applicability and accuracy of the sensing system.

[0028] (3) Compared with existing bolt loosening sensing devices based on double-layer substrate patch antennas, the bolt body of the present invention, based on incompressible liquid deformation detection device, requires significantly fewer openings to store liquid, thus avoiding excessive weakening of bolt strength due to excessively large through-holes and improving safety. Furthermore, since the lower part of the bolt remains solid, the bolt manufacturing and processing can utilize templates, eliminating the need for opening holes, reducing manufacturing procedures and costs, and preventing cracks or damage to the bolt during the opening process. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the present invention;

[0030] Figure 2 This is a cross-sectional view of the bolt loosening detection system of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of the RFID tag of the present invention;

[0032] Figure 4 This is a schematic diagram of the structure of the accessory of the present invention;

[0033] Figure 5 This is a schematic diagram of the assembly of the accessory and the RFID tag of the present invention;

[0034] Figure 6 This is a schematic diagram of the telescopic rod of the present invention;

[0035] Figure 7 This is a schematic diagram of the assembly of the perforated bolt and the telescopic rod according to the present invention;

[0036] Figure 8 This is a flowchart of the method of the present invention;

[0037] In the diagram, 1-RFID tag, 2-Hole bolt, 3-Telescopic rod, 4-Reader, 5-Accessory, 6-Substrate, 7-Annular patch, 8-Microstrip feeder, 9-Chip, 10-Main body of rod, 11-Metal head, 12-Short tube, 13-First connecting rod, 14-First connecting rod, 15-Closed groove, 16-Incompressible liquid. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0040] Example 1

[0041] This invention proposes a bolt loosening sensing device and method. The structural diagram of the device is shown below. Figure 1 As shown, the cross-sectional view is as follows Figure 2 As shown.

[0042] This invention proposes a bolt loosening sensing device for detecting the deformation of a bolt 2 with an opening. The sensing device includes an RFID tag 1, one side of which has a chip 9. The RFID tag 1 is fitted into an accessory 5. The RFID tag 1 is connected to one end of a telescopic rod 3, and the other end of the telescopic rod 3 is inserted into the bolt 2 with an opening. The accessory 5 is connected to the bolt 2 with a first connecting rod 13 and a second connecting rod 14. The RFID tag 1 is wirelessly connected to a reader 4. In some embodiments, the side of the RFID tag 1 has three notches corresponding to the protrusions of the accessory 5. The RFID tag 1 is fitted into the accessory 5 through the protrusions and notches. The structural diagram of the accessory 5 is shown below. Figure 4 As shown. The assembly diagram of Annex 5 and RFID tag 1 is as follows. Figure 5 As shown.

[0043] In some embodiments, one end of the first connecting rod 13 and one end of the second connecting rod 14 are fixed to the perforated bolt 2, and the other end of the first connecting rod 13 and the other end of the second connecting rod 14 are connected to the lower surface of the accessory 5.

[0044] The RFID tag 1 also includes a substrate 6, an annular patch 7, and a microstrip feed line 8. The two ends of the microstrip feed line 8 are connected to a chip 9 and the annular patch 7, respectively. The annular patch 7 and the chip 9 are placed on the upper surface of the substrate 6. A hole is opened at the center of the substrate 6, penetrating the substrate 6 and cutting off the middle of the microstrip feed line 8. The chip 9 is fixed on the substrate 6. In some embodiments, the hole in the substrate 6 is a circular hole, and the radius of the circular hole is larger than the cross-sectional radius of the main body 10. The substrate 6, the microstrip feed line 8, and the chip 9 constitute a patch antenna. The structure of the RFID tag is as follows. Figure 3 As shown.

[0045] The telescopic rod 3 consists of a rod body 10, a metal head 11, and a short tube 12. One end of the rod body 10 is connected to the metal head 11. The rod body 10 is placed inside the short tube 12 and fits into the opening of the substrate 6. The metal head 11 is located above the cut-off point of the microstrip feed line 8 and does not contact the microstrip feed line 8. A schematic diagram of the telescopic rod 3 is shown below. Figure 6 As shown.

[0046] A hole is drilled at the center of the bolt 2 to form a closed groove 15, which is filled with an incompressible liquid 16. The other end of the rod body 10 is inserted into the incompressible liquid 16, and the short tube 12 is fixed to the top of the closed groove 15. In some embodiments, the hole drilled by the bolt 2 is a circular hole, the diameter of which is the outer diameter of the short tube 12. The assembly of the bolt 2 and the telescopic rod 3 is as follows: Figure 7 As shown.

[0047] In this invention, the reader 4 is responsible for wirelessly reading the information on the RFID tag 1 and processing the data. In addition, this invention is assembled with the axially drilled bolt 4 via the attachment 5, and the patch antenna is responsible for converting the normal stress change information of the bolt 4 into electromagnetic wave signals.

[0048] In some embodiments, the microstrip feeder 8 and the metal head 11 are made of brass, the substrate 6 and the rod body 10 are made of FR4, and the short tube 12 is made of resin.

[0049] The first connecting rod 13, the second connecting rod 14, the RFID tag 1, the telescopic rod 3, and the accessory 5 of the present invention are fastened to the head of the hole bolt 2.

[0050] This invention utilizes the aforementioned device to propose a bolt loosening sensing method. The flowchart of the method is as follows: Figure 8 As shown. The method includes the following steps:

[0051] S1. The reader 4 of the device sends modulated first electromagnetic wave signals to the RFID tag 1 at different frequencies. When the power of the first electromagnetic wave signal received by the RFID tag 1 reaches the threshold, the chip 9 of the RFID tag 1 is activated.

[0052] S2. After activation, the patch antenna in RFID tag 1 generates current and emits a second electromagnetic wave signal with tag number and location information.

[0053] S3. The second electromagnetic wave signal with the tag number and location information is received and processed by the reader 4 to obtain information about the position and status of the bolt.

[0054] The force applied to the bolt causes changes in the liquid, which in turn translates into changes in the length of the bolt. These changes in length are then transmitted through the telescopic rod 3 to the connection and disconnection of the microstrip feed line 8, which in turn causes changes in the open and closed circuits of the patch antenna. This results in the appearance or disappearance of the antenna resonant frequency, causing the antenna resonant frequency to drift. The working state of the bolt can be determined based on the drift value.

[0055] The second electromagnetic wave signal includes the resonant frequency. When the patch antenna is in a closed state, the reader 4 detects the resonant frequency; when the patch antenna is in an open state, the reader 4 cannot detect the resonant frequency. The reader 4 obtains information about the bolt's state based on the resonant frequency, which indicates changes in bolt tightness. When the bolt 2 is subjected to force, it causes a change in the lateral force on the screw, resulting in a change in the volume of the incompressible liquid 16. This volume change is transmitted through the telescopic rod 3, which in turn changes the state of the patch antenna, causing the resonant frequency to appear or disappear. The appearance or disappearance of the resonant frequency indicates changes in bolt tightness, thus identifying bolt loosening. Simultaneously, when multiple RFID tags 1 are arranged within the scanning range of the reader 4, the reader 4 receives the tag number and location information provided by the chip 9, allowing it to mark the bolt state at each measuring point and locate the loose bolt.

[0056] The principle of this invention for measuring screw length changes is as follows: An RFID reader transmits modulated electromagnetic wave signals to an RFID tag at different frequencies. When the signal power received by the RFID tag reaches a threshold, the chip in the RFID tag is activated. The minimum transmission power required for tag activation is related to the frequency of the signal transmitted by the reader. When the reader transmits a signal at the resonant frequency of the partially overlapping fan-shaped patch antenna in the RFID tag, the minimum transmission power required to activate the tag is minimized. By finding the transmission frequency that minimizes the transmission power, the resonant frequency of the antenna in the RFID tag can be determined.

[0057] Once the chip in the RFID tag is activated, the antenna in the tag generates an electric current and emits an electromagnetic wave signal carrying the tag number and location information. This signal is received and processed by the reader to obtain information about the bolt's position and status.

[0058] This invention employs Radio Frequency Identification (RFID) technology to design a displacement sensor for monitoring changes in screw tension. When assembling the device used in this invention, the tag 1 and the axially oriented bolt 2 are assembled together via accessory 5 and connecting rod 13, and connecting rod 14.

[0059] The incompressible liquid 16 of the present invention can be water.

[0060] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A bolt loosening sensing device, characterized by, The device is used for detecting deformation of a hole bolt (2), and the sensing device comprises an RFID tag (1), one side of the RFID tag (1) is provided with a chip (9), the RFID tag (1) is sleeved into an accessory (5), the RFID tag (1) is connected with one end of an extension rod (3), the other end of the extension rod (3) is inserted into the hole bolt (2), the accessory (5) is connected with the hole bolt (2) through a first connecting rod (13) and a second connecting rod (14), and the RFID tag (1) is wirelessly connected with a reader (4); The RFID tag (1) further comprises a substrate (6), a ring-shaped patch (7) and a microstrip feed line (8), two ends of the microstrip feed line (8) are connected with the chip (9) and the ring-shaped patch (7) respectively, the ring-shaped patch (7) and the chip (9) are arranged on an upper surface of the substrate (6), a hole is formed in the center of the substrate (6), the hole penetrates through the substrate (6) and truncates a middle part of the microstrip feed line (8), and the substrate (6), the microstrip feed line (8) and the chip (9) form a patch antenna; The extension rod (3) is composed of a rod body (10), a metal head (11) and a short pipe (12), one end of the rod body (10) is connected with the metal head (11), the rod body (10) is arranged in the short pipe (12), the rod body (10) is sleeved into the hole of the substrate (6), and the metal head (11) is arranged above the truncated position of the microstrip feed line (8) and does not contact the microstrip feed line (8), The hole bolt (2) is provided with a hole in the center, forming a closed groove (15), the groove is filled with an incompressible liquid (16), the other end of the rod body (10) is inserted into the incompressible liquid (16), and the short pipe (12) is fixed on the top of the closed groove (15).

2. A bolt loosening sensing device according to claim 1, wherein The hole of the substrate (6) is a circular hole, and the radius of the circular hole is greater than the cross-sectional radius of the rod body (10).

3. A bolt loosening sensing device according to claim 1, wherein The hole of the hole bolt (2) is a circular hole, and the diameter of the circular hole is equal to the outer diameter of the short pipe (12).

4. A bolt loosening sensing device according to claim 1, wherein One end of the first connecting rod (13) and one end of the second connecting rod (14) are fixed to the hole bolt (2), and the other end of the first connecting rod (13) and the other end of the second connecting rod (14) are connected with the lower surface of the accessory (5).

5. A bolt loosening sensing device according to claim 1, wherein The side surface of the RFID tag (1) is provided with three notches corresponding to protrusions of the accessory (5), and the RFID tag (1) is sleeved into the accessory (5) through the protrusions and the notches.

6. A bolt loosening sensing device according to claim 1, wherein The materials of the microstrip feed line (8) and the metal head (11) are brass, the materials of the substrate (6) and the rod body (10) are FR4, and the material of the short pipe (12) is resin.

7. A bolt loosening sensing method characterized by, The method comprises the following steps: S1, the reader (4) of the device sends a modulated first electromagnetic wave signal to the RFID tag (1) at different frequencies, when the power of the first electromagnetic wave signal received by the RFID tag (1) reaches a threshold value, the chip (9) of the RFID tag (1) is activated; S2, after being activated, the patch antenna in the RFID tag (1) generates a current and emits a second electromagnetic wave signal with tag number and position information; S3. The second electromagnetic wave signal with the tag number and location information is received and processed by the reader (4) to obtain information on the position and status of the bolt; When the bolt (2) is under force, the state of the patch antenna switches between the open state and the closed state.

8. The method of claim 7, wherein the bolt loosening sensing method is characterized by, The second electromagnetic wave signal includes the resonant frequency. When the patch antenna is in the on state, the reader (4) detects the resonant frequency. When the patch antenna is in the off state, the reader (4) cannot detect the resonant frequency.

9. The method of claim 8, wherein the bolt loosening sensing method is characterized by, The reader (4) obtains information about the state of the bolt based on the resonant frequency. The information about the state of the bolt is the information about the change in the tightness of the bolt.

10. The method of claim 7, wherein the bolt loosening sensing method is characterized by, When the bolt (2) is under force, it causes a change in the volume of the incompressible liquid (16), and the change in volume is converted into a change in the state of the patch antenna through the telescopic rod (3).

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