A ring-shaped overlapping sub-patch antenna structure of a bolt loosening detection sensor

Abstract

The application discloses a ring-shaped overlapped sub-patch antenna structure of a bolt loosening detection sensor, which comprises a first insulating part provided with an outer circumferential surface and a second insulating part provided with an inner arc surface, a ring-shaped first radiation patch is covered on the outer circumferential surface, a curved rectangular second radiation patch is covered on the inner arc surface, the first insulating part is fixedly connected on the head of a bolt to be detected, the first radiation patch is coaxially arranged with the bolt to be detected, the second insulating part is fixedly connected on a connected part, the first radiation patch is concentrically arranged with the second radiation patch and overlaps with each other; when the bolt is loosened, the first radiation patch is spirally or linearly displaced relative to the second radiation patch, according to the relationship between the length variation of the overlapping of the first radiation patch and the second radiation patch and the variation of the longitudinal resonant frequency, the bolt displacement can be calculated by determining the variation of the longitudinal resonant frequency, so that the bolt loosening amount under different displacement conditions can be accurately detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave measurement and sensing technology, and particularly relates to a ring-shaped overlapped sub-patch antenna structure of a bolt loosening detection sensor. BACKGROUND

[0002] Bolted connections are widely used in many industries, including mechanical engineering, civil engineering and aerospace engineering. Their popularity is due to ease of installation and implementation, ability to withstand relatively heavy loads, low cost, and acceptable reliability. However, under the influence of temperature fluctuations, repeated forces and vibrations, the bolt threads slide relative to the joint threads, resulting in bolt loosening. If the loosened bolt cannot be found and tightened in time, the connection of the bolt with the loosened bolt will become a weak point of the structure, threatening the safety of the entire structure.

[0003] The torque detection method is direct, and the inspector directly checks the torque of the bolt with a torque wrench, however, this method is not suitable for all cases. Visual inspection is another typical detection method that focuses on the second stage of bolt loosening, which evaluates bolt loosening by capturing digital images or videos of the rotation between the nut and the bolt shaft, but the accuracy of the visual inspection monitoring is currently limited. The principle of the vibration-based method is based on recording and analyzing dynamic responses to evaluate the bolt state of the structure exposed to vibration loads, however, since the vibration response mainly depends on the input, the vibration-based technology is more suitable for identifying global damage.

[0004] The design of the planar overlapping angle sensor is to connect the screw and the base plate with a connecting plate in the upper half, when the screw loosens, it will drive the base plate to rotate together, thereby achieving the purpose of detecting screw loosening, however, when the screw loosens and drives the upper base plate to rotate, the gap between the upper base plate and the lower base plate increases, which affects the sensitivity of the sensor, thereby affecting the detection effect. Furthermore, when the bolt is affected by some physical factors and does not rotate but directly displaces up and down to loosen, the planar overlapping angle sensor cannot detect the loosening state of the screw, and since the gap between the upper and lower base plates of the sensor is too large, it cannot accurately measure the loosening of the screw, the sensitivity will decrease linearly, and even the regular change of the antenna resonance frequency will be destroyed. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a ring-shaped overlapped sub-patch antenna structure of a bolt loosening detection sensor, which aims to accurately detect the elongation of the displacement of the sensor caused by the rotation of the bolt or other factors, avoid the influence of the increase of the gap between the base plates on the stability and sensitivity of the sensor, and thus ensure the regular change of the antenna resonance frequency.

[0006] The application discloses a ring-shaped overlapping sub-patch antenna structure of a bolt looseness detection sensor, which comprises a first insulating part provided with an outer circumferential surface and a second insulating part provided with an inner arc surface, a ring-shaped first radiation patch is covered on the outer circumferential surface, and a curved rectangular second radiation patch is covered on the inner arc surface; the first insulating part is fixedly connected on the head of a bolt to be detected, and the first radiation patch is coaxially arranged with the bolt to be detected; the second insulating part is fixedly connected on a connected part; the first radiation patch and the second radiation patch are concentrically arranged and overlap with each other; when the bolt is loosened, the relationship between the change amount AL of the overlapping length of the first radiation patch and the second radiation patch and the change amount AF of the longitudinal resonant frequency is as follows: o 10

[0007]

[0008] Wherein, c is the speed of light in vacuum, epsilon is the relative dielectric constant of the second insulating part, L1 is the length of the second radiation patch, W1 is the width of the first radiation patch, and L0 is the initial overlapping length of the first radiation patch and the second radiation patch; by determining the change amount of the longitudinal resonant frequency, the displacement amount of the bolt can be calculated.

[0009] Further, the outer diameter of the first radiation patch is 20mm, the length of the second radiation patch is 19mm, the width of the second radiation patch is 3.5mm, the distance between the second radiation patch and the linear side edges of the inner arc surface is 0.705mm, and the distance between the second radiation patch and the arc side edge of the inner arc surface is 1mm.

[0010] In order to facilitate signal transmission, the second radiation patch is located at the lower part of the second insulating part, a metal transmission line is arranged above the second radiation patch on the second insulating part, the metal transmission line is in a straight line shape and is arranged in parallel with the axial direction of the bolt, the lower end of the metal transmission line is electrically connected with the second radiation patch, and the upper end of the metal transmission line is a lumped port.

[0011] Further, the width of the metal transmission line is 0.8mm, and the impedance matching and sensitivity are high.

[0012] Further, the overlapping length range of the first radiation patch and the second radiation patch is 0mm-5mm.

[0013] ​​The beneficial effects of the present application are that when the bolt is loosened, the first radiation patch spirally or linearly displaces relative to the second radiation patch, the overlapping length of the first radiation patch and the second radiation patch changes, the resonant frequency changes, and the loosening amount of the bolt is calculated according to the corresponding relationship between the overlapping length change amount and the resonant frequency change amount; so that the loosening amount of the bolt under different displacement conditions can be accurately detected. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The connection diagram of the bolt and the connected piece in the present application is shown in the figure.

[0015] Figure 2 The assembly effect diagram of the second insulating piece and the second radiation patch in the present application is shown in the figure.

[0016] Figure 3 The assembly effect diagram of the first radiation patch and the second radiation patch in the present application is shown in the figure.

[0017] Figure 4 The resonant frequency diagram when the overlapping length of the first radiation patch and the second radiation patch increases from 0 mm to 5 mm with a step of 0.5 mm is shown in the figure.

[0018] Figure 5 The linear fitting curve diagram when the overlapping length of the first radiation patch and the second radiation patch increases from 0 mm to 5 mm with a step of 0.5 mm is shown in the figure.

[0019] Figure 6 The resonant frequency diagram when the overlapping length of the first radiation patch and the second radiation patch increases from 4 mm to 5 mm with a step of 0.1 mm is shown in the figure.

[0020] Figure 7 The linear fitting curve diagram when the overlapping length of the first radiation patch and the second radiation patch increases from 4 mm to 5 mm with a step of 0.1 mm is shown in the figure.

[0021] In the figure, 1 is a bolt, 2 is a first radiation patch, 3 is a first insulating piece, 4 is a second insulating piece, 5 is a connected piece, 6 is a metal transmission line, and 7 is a second radiation patch. DETAILED DESCRIPTION

[0022] The application will be described in detail below with reference to the drawings. The embodiments of the application are described below in detail, examples of which are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are only used to explain the application, and cannot be interpreted as a limitation on the application. The orientation terms such as left, middle, right, upper, lower, etc. in the examples of the application are only relative concepts or are referenced to the normal use state of the product, and should not be considered as limiting.

[0023] An annular overlapping sub-patch antenna structure of a bolt looseness detection sensor, as shown in Figure 1 、 Figure 2 and Figure 3 , comprising a first insulating part 3 provided with an outer circumferential surface and a second insulating part 4 provided with an inner arc surface, an annular first radiation patch 2 is covered on the outer circumferential surface, and a curved rectangular second radiation patch 7 is covered on the inner arc surface, the first insulating part 3 is fixedly connected on the head of the bolt to be detected 1, and the first radiation patch 2 and the bolt to be detected 1 are coaxially arranged, the second insulating part 4 is fixedly connected on the connected part 5, the first radiation patch 2 and the second radiation patch 7 are concentrically arranged and overlap with each other; when the bolt 1 is loose, the relationship between the change amount ΔL o of the overlapping length of the first radiation patch 2 and the second radiation patch 7 and the change amount Δf 10 of the longitudinal resonant frequency is:

[0024]

[0025] Wherein, c is the speed of light in vacuum, ε is the relative dielectric constant of the second insulating part 4, L1 is the length of the second radiation patch 7, W1 is the width of the first radiation patch 2, L0 is the initial overlapping length of the first radiation patch 2 and the second radiation patch 7, and the displacement of the bolt 1 is the relative displacement of the first radiation patch 2 and the second radiation patch 7 in the axial direction. After the overlapping part between the first radiation patch 2 and the second radiation patch 7 forms an electric field, a resonant frequency is generated, and with the change of the overlapping length, the resonant frequency will also be shifted. By comparing the resonant frequency before the change of the overlapping length, the sensitivity of the two radiation patches to the change of the overlapping length caused by the loosening of the bolt 1 can be judged.

[0026] In addition, the outer diameter of the first radiation patch 2 is 20 mm, the length of the second radiation patch 7 is 19 mm, the width of the second radiation patch 7 is 3.5 mm, the distance between the second radiation patch 7 and the linear side of the inner arc surface is 0.705 mm, and the distance between the second radiation patch 7 and the arc side of the inner arc surface is 1 mm. These parameters can make the sensor reflection coefficient smaller and the transmission effect better. The first radiation patch 2 and the second radiation patch 7 are both copper sheets, the first insulating part 3 and the second insulating part 4 are both FR4 plates with a thickness of 1 mm, so that the frequency changes linearly with the length of the overlapping part of the first radiation patch 2 and the second radiation patch 7. The second radiation patch 7 is located at the lower part of the second insulating part 4, a metal transmission line 6 is arranged above the second radiation patch 7 on the second insulating part 4, the metal transmission line 6 is in a straight line shape and is arranged in parallel with the axial direction of the bolt 1, the lower end of the metal transmission line 6 is electrically connected with the second radiation patch 7, and the upper end of the metal transmission line 6 is a lumped port. The lumped port is connected with a monopole antenna through a coaxial line, and the sensor frequency change detection can be performed after the monopole antenna is connected with a net. The width of the metal transmission line 6 is 0.8 mm, and the overlapping length of the first radiation patch 2 and the second radiation patch 7 ranges from 0 mm to 5 mm.

[0027] As Figure 4 It can be seen that when the overlapping length of the first radiation patch 2 and the second radiation patch 7 is 0 mm, the resonant frequency is 2.95 GHz; when the overlapping length of the two radiation patches ranges from 0 mm to 5 mm with a step of 0.5 mm, the resonant frequency increases from 2.95 GHz to 3.44 GHz, and the sensitivity is 49.14 MHz per 0.5 mm of resonant frequency change.

[0028] As Figure 5 It can be seen that when the overlapping length of the first radiation patch 2 and the second radiation patch 7 increases from 0 mm to 5 mm with a step of 0.5 mm, the fitting correlation coefficient is 0.9985.

[0029] As Figure 6 It can be seen that when the overlapping length of the first radiation patch 2 and the second radiation patch 7 increases from 4 mm to 5 mm with a step of 0.1 mm, the resonant frequency increases from 3.31 GHz to 3.44 GHz, and the sensitivity is 12.87 MHz per 0.1 mm of resonant frequency change.

[0030] As Figure 7 It can be seen that when the overlapping length of the first radiation patch 2 and the second radiation patch 7 increases from 4 mm to 5 mm with a step of 0.1 mm, the fitting correlation coefficient is 0.9989.

[0031] In combination with Figure 5 and Figure 7The linear fitting correlation coefficient shows that the length of the overlap between the first radiation patch 2 and the second radiation patch 7 and the resonant frequency have a good correlation.

[0032] In combination Figure 4 And Figure 6 It can be seen that the resonant frequency of the overlap between the first radiation patch 2 and the second radiation patch 7 shows a high sensitivity when the step is 0.5mm or a high-precision step of 0.1mm.

[0033] The above figures show the feasibility of the present application for detecting the loosening of the bolt 1.

[0034] Compared with other sensors, the present application has higher measurement accuracy and sensitivity, can adapt to various loosening conditions of the bolt, has low manufacturing cost, simple operation, small sample volume, and has a high application prospect in the field of microwave circuit manufacturing.

[0035] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A ring-shaped overlapping sub-pattern antenna structure for a bolt loosening detection sensor, characterized in that: The device includes a first insulating member with an outer circumferential surface and a second insulating member with an inner arc-shaped surface. A first annular radial patch is covered on the outer circumferential surface, and a second curved rectangular radial patch is covered on the inner arc-shaped surface. The first insulating member is fixedly connected to the head of the bolt to be tested, with the first radial patch and the bolt coaxially arranged. The second insulating member is fixedly connected to the connected component. The first and second radial patches are coaxially arranged, and at least a portion of the second radial patch partially overlaps with the first radial patch along the circumferential direction of the first radial patch. When the bolt loosens, the first radial patch shifts relative to the second radial patch, and the change in the overlap length ΔL between the first and second radial patches is significant. o The change in longitudinal resonant frequency Δf 10 The relationship between them is: ； Where c is the speed of light in a vacuum, ε is the relative permittivity of the second insulator, L1 is the length of the second radiating patch, W1 is the width of the first radiating patch, and L0 is the initial overlap length between the first and second radiating patches; the displacement of the bolt is calculated by determining the change in the longitudinal resonant frequency.

2. The ring-shaped overlapping sub-pattern antenna structure of the bolt loosening detection sensor according to claim 1, characterized in that: The outer diameter of the first radiating patch is 20 mm, the length of the second radiating patch is 19 mm, the width of the second radiating patch is 3.5 mm, the distance between the second radiating patch and the straight sides of the inner arc surface is 0.705 mm, and the distance between the second radiating patch and the arc side of the inner arc surface is 1 mm.

3. The ring-shaped overlapping sub-pattern antenna structure of the bolt loosening detection sensor according to claim 2, characterized in that: The second radiating patch is located at the lower part of the second insulating member. A metal transmission line is covered on the second insulating member above the second radiating patch. The metal transmission line is straight and parallel to the axis of the bolt. The lower end of the metal transmission line is electrically connected to the second radiating patch, and the upper end of the metal transmission line is a lumped port.

4. The ring-shaped overlapping sub-pattern antenna structure of the bolt loosening detection sensor according to claim 3, characterized in that: The width of the metal transmission line is 0.8 mm.

5. The ring-shaped overlapping sub-pattern antenna structure of the bolt loosening detection sensor according to any one of claims 1 to 4, characterized in that: The overlap length between the first and second radiating patches ranges from 0 mm to 5 mm.

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