CN113065627B - Chipless RFID strain sensing tag and nondestructive testing method thereof - Google Patents
Chipless RFID strain sensing tag and nondestructive testing method thereof Download PDFInfo
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- G—PHYSICS
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- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
- G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
- G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
- G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
- G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
- G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
- G06K19/07771—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object
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- G—PHYSICS
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/22—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in capacitance
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
- G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
- G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
- G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
- G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
- G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
- G06K19/07773—Antenna details
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
- H01Q1/2225—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
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Abstract
The invention discloses a chipless RFID strain sensing tag and a nondestructive testing method thereof, which are applied to the field of structural health monitoring and nondestructive testing, and aim to solve the problems that only a single strain direction can be detected and the prior art is easily interfered by the environment; the interference of RCS of the metal and antenna structure to echo signals is reduced by using a transmitting antenna to transmit cross-polarized electromagnetic waves; the structure provided by the invention can effectively guarantee the strength of the response signal and the working stability; compared with the existing scattering type strain sensing label, the invention has the advantages of stronger anti-interference capability, better communication performance and higher sensitivity to strain detection, can detect the strain direction and can reduce the influence of environmental noise.
Description
Technical Field
The invention belongs to the field of structural health monitoring and nondestructive testing, and particularly relates to a chipless RFID strain sensing detection technology.
Background
Metal structures are used in enormous quantities in modern engineering. Metal structures operate in harsh environments throughout the year and are subject to heavy and fatigue loads for extended periods of time, which inevitably result in various damage and defects. When damage and defects accumulate to a certain extent, the load-bearing capacity and fatigue resistance of the metal structure are reduced, with extremely serious consequences. The strain is an important index for representing the stress state of the engineering structure, and the safety condition of the structure can be effectively judged by strain detection of the stress concentration part, so that the strain of the surface of the metal structure is monitored by adopting a reliable and practical technical means, and then corresponding preventive measures are taken, thereby having important significance for reducing or avoiding structural failure accidents.
The traditional strain detection and health monitoring technology has been developed for decades, and a relatively perfect theoretical system is formed, and strain detection methods include a strain gauge electrical measurement method, a fiber Bragg grating test method and the like. However, the conventional nondestructive testing technology is often poor in feasibility and high in cost when detecting potential damages in large-scale facilities, particularly damages in complex environments, due to heavy equipment, low testing speed, small detectable range and low automation degree. Wireless Sensor Networks (WSNs) stand out for the problem of surface stress health monitoring of large-scale metal facilities. The WSN is an ad hoc network formed by a large number of cheap micro sensor nodes deployed in a monitoring area in a wireless communication mode. RFID technology can be used to build wireless sensor networks. RFID, a radio frequency identification technology, refers to non-contact two-way data communication by radio frequency, so as to achieve the purpose of identifying objects and exchanging data. A classical RFID system consists of one reader and a plurality of RFID tags. The RFID tags can form an array due to low cost, can realize long-distance communication and the like, and can be used as sensor nodes of a wireless sensing network after the sensing function is developed. The existing RFID wireless sensing technology is divided into an active type and a passive type, the active type needs a battery to provide energy for an antenna and a sensor, and the RFID wireless sensing technology using the battery does not become a mainstream technical scheme of the wireless detection technology due to the problems of relatively large size, expensive replacement cost, low service life of the sensor, pollution of the battery to the environment and the like. The passive RFID strain sensing technology does not need an extra integrated power supply, can work only by supplying power with an external radio frequency signal, can be implanted into equipment without replacing parts, has better robustness and stability, and can work unattended throughout the year and the like, thus becoming the mainstream technical scheme at present.
The RFID passive sensing technology is divided into two technologies, namely chip RFID strain sensing technology and chipless RFID strain sensing technology. The chip RFID sensing technology is basically operated in such a way that a tag antenna receives continuous electromagnetic waves sent by a reader, when the antenna is in strain, near-far field parameters such as antenna electromagnetic field distribution, antenna input impedance and gain are correspondingly changed due to the change of the structure of the tag antenna, and the change is received by the reader through backscatter communication by using analog quantities such as backscatter power, so that characteristic information can be extracted according to received signals, and the strain of a marked object can be inverted. The chipless RFID sensing technology does not need any digital chip, the working principle of the chipless RFID sensing technology is that a reader sends out a string of electromagnetic waves with a wide frequency band, when the electromagnetic waves irradiate a chipless RFID tag, because of the characteristics of the structure of the tag, different reflection capacities are provided for different frequency signals, so that the reflection signals carry the structure parameters of the antenna, when the structure of the antenna changes, the frequency domain characteristics of the tag antenna change accordingly, and the strain of the structure can be inverted by extracting the characteristic information of the echo signals.
Closest prior art
(1) RFID strain sensing label with chip
For example, in Embedded wireless strain sensors based on printed RFID tag, Sari Merilampi et al proposed an Embedded wireless strain sensing tag based on printed RFID tag, which awakens the threshold power P of the RFID tag through the reader t To invert the strain.
This method has the following disadvantages:
1. the relation between the threshold power characteristic value and the strain is established by using the amplitude of the signal, and when the interference of an external environment electromagnetic noise signal is received, the stability of the amplitude of the signal is difficult to ensure, and the error is very large.
2. When the distance R changes, the threshold power of the characteristic value also changes, when the relative angle between the reader antenna and the tag antenna changes, the directivity coefficient of the reader antenna and the directivity coefficient of the tag antenna also change, the threshold power of the characteristic value also changes, the reference value is difficult to calibrate in practical use, and the strain is difficult to quantitatively monitor.
In view of the above disadvantages, Matheus f.kuhn et al propose an RFID Strain sensing tag Based on an inverted F antenna in a Novel RFID-Based Strain Sensor for Wireless Structural Health Monitoring, and characterize Strain using the resonant frequency of the antenna Strain Sensor as a characteristic value.
The design fixes the transmitting power P of the reader, and the frequency is swept in a UHF (ultra high frequency) frequency band to obtain the frequency f i Maximum interrogation distance R of i The frequency corresponding to the maximum interrogation distance is the resonant frequency. When the antenna deforms, the resonant frequency of the antenna changes, and the strain of the antenna can be quantitatively inverted only by knowing the offset delta f of the resonant frequency. Compared with the prior art, the method has the advantages that the used resonance frequency is used as the characteristic value, and the defect that the signal amplitude characteristic value cannot be calibrated due to the change of the space angle and the distance is overcome. However, this design still suffers from the following disadvantages:
the UHF frequency band is too narrow, and the external metal environment may cause the resonance frequency to shift outside the UHF frequency band, thereby affecting the normal operation of the antenna.
The RFID radio frequency chip is a digital device and has certain requirements on temperature, so that the RFID strain sensing tag with the chip cannot work in extreme environments such as low temperature, high temperature and the like.
(2) Chipless antenna strain sensing tag
Aiming at the defect that the RFID strain sensing label with the chip can not work in an extreme environment and reducing the cost, the RFID strain sensing label without the chip is adopted for strain sensing.
A chip-free Strain sensing tag based on RCS (radar reflection cross section) is proposed by Trang T.Thai et al in A New Developed Radio Frequency free Passive high Sensitive Strain Transducer. The resonant frequency of the patch depends on the impedance of the resonator, which in turn depends on the gap capacitance at the open loop. The resonant frequency is very sensitive to the open-loop capacitance value, and the change of the gap capacitance value can be caused by the small deformation generated by the antenna, so that the design can realize the high-sensitivity detection of the strain.
The following problems still exist with this design:
1. the scattering type tag is small in size, based on the radar scattering principle, the energy of a response signal is weak, and the reading distance is limited.
2. The RCS of the metal object interferes with the detection result.
3. Only a single direction of strain can be detected.
4. The change of the resonance frequency is influenced by environmental noise signals and structural deformation, and the anti-interference capability is poor.
Disclosure of Invention
The invention provides a chipless RFID strain sensing tag and a nondestructive testing method thereof, aiming at overcoming the defect that the existing antenna strain sensing tag is easily interfered by the external environment, increasing the sensing sensitivity and realizing the measurement of the size and the direction of the strain on the metal surface.
One of the technical schemes adopted by the invention is as follows: a chipless RFID strain sensing tag comprising: the metal floor completely covers the bottom surface of the dielectric substrate, and the top metal patch is arranged on the top surface of the dielectric substrate;
the top metal patch includes at least: a main transmission line and n C-type resonators which are obtained by connecting the orthogonal polarization antennas;
the main transmission line is in an omega shape and specifically comprises: angle theta 1 2 angle theta 2 And 2 rectangular transmission lines, angle theta 1 The two ends of the annular transmission line respectively pass through 1 angle theta 2 The annular transmission line is connected with 1 rectangular transmission line;
the n C-type resonators are sequentially arranged at an angle theta 1 In the ring-shaped transmission line, n C-type resonator openings point to the angle theta 1 The symmetry axis of each C-type resonator passes through the angle theta 1 The center of the annular transmission line, the bottom of each C-type resonator and the angle theta 1 The distances between the ring transmission lines are the same.
Each C-type resonator is obtained by bending the transmission line with the same length twice.
Bottom of each C-type resonator and angle theta 1 The annular transmission lines include a coupling capacitor therebetween.
The top metal patch further comprises a top antenna, and the top antenna is connected with two ends of the main transmission line.
The second technical scheme provided by the invention is as follows: when strain occurs, the resonance frequency of the resonator changes, the resonance frequency of the resonator in the changed frequency domain information is extracted, and the magnitude and the direction of the strain are obtained through inversion.
Recording the symmetry axis and the over angle theta of the ith resonator 1 The included angle between horizontal lines of the circle centers of the annular transmission lines is theta i If the strain angle is θ', the i-th resonator forms an angle Δ θ with the strain i ＝θ’-θ i Let the sensitivity coefficients of the ith C-type resonator to the strain in the x and y directions be alpha respectively i And beta i And (3) arranging n resonators in a formula, and obtaining an expression for solving an included angle between the strain size and the strain as follows:
and obtaining the included angle between the strain magnitude and the strain by solving the least square.
The specific detection process is as follows:
s1, generating a broadband frequency-sweeping radio frequency signal: broadband frequency-sweeping radio-frequency electricity generating vertical polarization by broadband radio-frequency generating and receiving device arranged h meters above measured metal componentMagnetic wave signal U 1 ；
S2, attaching the RFID strain sensing label to the surface of the metal member;
s3, generating a broadband frequency-sweeping radio frequency signal: a broadband radio frequency generation and receiving device arranged h meters above the measured metal component generates a broadband frequency-sweeping radio frequency electromagnetic wave signal U with vertical polarization 2 ；
S4, generating a response signal: the vertical linear polarization antenna of the tag antenna attached to the surface of the metal component receives a vertically polarized broadband frequency-sweeping radio frequency electromagnetic wave signal U 2 Then, the main transmission line is transmitted to a horizontally polarized transmitting antenna in a guided wave mode, and the frequency domain information of the horizontally polarized electromagnetic wave radio frequency response signal transmitted to the free space by the horizontally linearly polarized transmitting antenna comprises the filtering information of all C-type resonators;
s5, receiving the radio frequency response signal: the radio frequency receiving and transmitting module receives the radio frequency response signal and converts the U 2 And U 1 Input data acquisition and processing module and subtract the two to obtain U 3 (ii) a Data acquisition and processing module pair signal U 3 Analyzing to obtain a signal U 3 Frequency-amplitude curve f-a;
s6, extracting characteristic frequency: the resonance frequency f of the frequency-amplitude curve f-A detected in S4 is extracted i ；
And S7, inverting the magnitude and direction of the strain through the frequency shift of the resonance frequency.
The invention has the beneficial effects that: the transmission line forwarding type antenna and the C-type resonator are used for forming the chipless RFID strain sensing tag, and strain characterization is based on resonance frequency change caused by structural change of the C-type resonator. The transmitting antenna is used for transmitting cross-polarized electromagnetic waves to reduce interference of RCS of the metal and antenna structure on echo signals. The structure can effectively guarantee the strength of the response signal and the working stability. Compared with a scattering type strain sensing tag, the scattering type strain sensing tag has the advantages of stronger anti-interference capability, better communication performance and higher sensitivity to strain detection, can detect the strain direction and can reduce the influence of environmental noise;
the invention has the following advantages:
1. the invention provides a transfer type RFID sensing tag with a plurality of C-shaped resonant structure transmission lines, wherein a pair of cross-polarized linear polarization antennas is used in an annular transmission line structure of the sensing tag, so that the communication distance is increased, and the interference of a metal object and an antenna structure RCS on signals is reduced; the quantitative detection of the strain in different directions can be realized;
2. detecting the magnitude and direction of the surface strain of the metal member based on the plurality of resonant frequencies of the sensor tag;
3. the detection method is realized by solving the least square solution of the over-determined equation, so that the interference of external noise signals can be reduced, and accidental errors can be removed.
Drawings
Fig. 1 is a schematic structural diagram of a top metal patch according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of a C-type resonator according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the orientation of a C-type resonator according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a force analysis provided by an embodiment of the present invention;
FIG. 5 is a drawing illustrating the detailed geometric parameters of a top metal patch according to an embodiment of the present invention;
FIG. 6 shows an S-shape of a linearly polarized antenna according to an embodiment of the present invention 11 A parameter schematic diagram;
FIG. 7 shows an S of a main transmission line according to an embodiment of the present invention 21 A parameter schematic diagram;
FIG. 8 is a diagram illustrating resonator length versus resonant frequency points provided by an embodiment of the present invention;
FIG. 9 is a schematic diagram of the variation of the resonant frequency of strain in the y-direction according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of a y-direction strain-resonant frequency linear fit provided by an embodiment of the present invention;
FIG. 11 is a schematic diagram illustrating the variation of resonant frequency of strain in the x-direction according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of an x-direction strain-resonant frequency linear fit provided by an embodiment of the present invention;
FIG. 13 is a strain diagram provided by an embodiment of the present invention;
FIG. 14 is a graph illustrating transmission coefficients after strain is applied according to an embodiment of the present invention;
FIG. 15 is a screenshot of a MATLAB least squares solution calculation routine provided by an embodiment of the present invention;
fig. 16 is a MATLAB least squares solution provided by an embodiment of the present invention.
Detailed Description
In order to facilitate the understanding of the technical contents of the present invention by those skilled in the art, the present invention will be further explained with reference to the accompanying drawings.
As shown in fig. 1, a chipless RFID strain sensor tag of the present invention includes three layers: a dielectric substrate, a metal floor and a top metal patch, wherein the dielectric substrate is of a bendable and extensible nonmetal sheet structure and has a thickness of h 0 (ii) a The metal floor is arranged in the whole area of the bottom surface of the medium substrate; the top metal patch is arranged on the top surface of the dielectric substrate.
The top patch structure is shown in fig. 1 and comprises: the broadband linear polarization antenna is a microstrip antenna composed of a top patch, a dielectric substrate and a metal floor, wherein the top antenna part is composed of a rectangle 1 and a rectangle 2, and the widths are w 2 Respectively having a length of w 3 And w 4 ；
Two orthogonally polarized antennas connected by a width w 1 The main transmission line structure comprises the following components in sequence from top to bottom: the metal floor comprises a top metal patch structure, a dielectric substrate and a metal floor. The top metal patch structure of the main transmission line specifically comprises: 1 segment angle theta 1 Annular transmission line (inner diameter r) 1 Outer diameter R 1 ) 2 section angle is theta 2 Annular transmission line (inner diameter r) 2 Outer diameter R 2 ) 2 segment lengths w 5 Width w 1 A rectangular transmission line of (1).
The n C-type resonator structures are sequentially as follows from top to bottom: the metal floor comprises a top metal patch structure, a dielectric substrate and a metal floor. Of said n C-type resonatorsAngle theta of the axis of symmetry to the main transmission line 1 The radius of the annular transmission line is coincident, and the distance from the bottom of the C-type resonator to the main transmission line is d 0 . The C-type resonator is formed by bending a section of transmission line twice, and the width of the transmission line is w 0 Let the length of the long side of the ith C-type resonator be l i Short side length of l 0 。
The working process of the label of the invention is as follows:
the reader transmits a series of broadband electromagnetic wave signals with the same amplitude and vertical polarization through the vertical polarization antenna, the receiving antenna of the chipless RFID strain sensing tag is the vertical polarization antenna, so that the electromagnetic waves can be better received, and the signals are transmitted to the transmitting antenna of the tag through the main transmission line of the tag and then are transmitted to the free space in the form of the horizontal polarization electromagnetic waves. And a horizontal polarization receiving antenna of the reader receives the signal to obtain frequency domain information of the echo signal. When the wave guide frequency on the main transmission line is the resonance frequency of the ith resonator, the C-type resonator resonates, and the transmission coefficient S of the transmission line 21 And sharply decreases. The signal strength of the transmit antenna echo signal within this stop band is drastically attenuated. When strain occurs, the resonant frequency of the resonator changes, and the magnitude and the direction of the strain can be obtained by extracting the resonant frequency of the resonator from the changed frequency domain information.
The chipless RFID strain sensing tag comprises a broadband linear polarization antenna and a broadband linear polarization antenna, wherein the broadband linear polarization antenna is vertically arranged, the broadband linear polarization antenna is horizontally arranged, and the two antennas are respectively used as a receiving and transmitting antenna; the purpose of cross polarization is to reduce interference and coupling between antennas and ensure effective transmission of signals.
The C-type microstrip resonator is a band elimination filter, and the purpose of connecting a capacitor in parallel between the resonator and the main transmission line is to reduce the bandwidth. The equivalent circuit is an LC parallel circuit as shown in fig. 2.
L is the equivalent inductance on the microstrip main transmission line, C 0 Is the coupling capacitance, L, between the resonator bottom and the microstrip main transmission line i And C i Is the equivalent inductance and capacitance of the ith C-type resonator. The resonant frequency of which is given by the formula1) The resonator is determined to exhibit band-stop characteristics.
The effect of the resonant frequency and strain of the C-type resonator is described in detail below:
equivalent inductance L i Transmission line length (2L) to C-type resonator i +L 0 ) Proportional relation, equivalent capacitance C i Then the width (L) of the slot of the C-type resonator 0 -2w 0 ) Inversely proportional to the length L of the transmission line i In direct proportion. The equivalent inductance and capacitance of the ith C-type resonator are characterized by formula (2), where k is 1 And k 2 Is a constant coefficient.
L i ＝k 1 (l 0 +2l i -2w 0 )
Taking the C-type resonator itself as a reference system, a rectangular coordinate system is set as shown in fig. 3, and the symmetry axis is set as the y-axis.
When a strain ε' in the y-direction occurs, the capacitance C i And an inductance L i Change to C i ' and L i ' as shown in equation (3).
L′ i ＝k 1 (l 0 +2l i -2w 0 )+2k 1 ε′l i
Thus the initial resonant frequency omega i Resonant frequency omega after occurrence of strain epsilon i ' the ratio and normalized resonance frequency are:
it can be seen that as the strain increases, the resonant frequency shifts to lower frequencies and the sensitivity is determined by the geometry of the C-type resonator.
And when a strain ε' in the x-direction occurs, the capacitance C i And an inductance L i Change to C i "and L i ″。
L″ i ＝k 1 (l 0 +2l i -2w 0 )+k 1 ε″l 0
Initial resonant frequency omega i With resonant frequency after strain epsilon ″) i The ratio and normalized resonance frequency are shown in equation (6).
When strain in the x direction occurs, the resonance frequency shifts to a high frequency direction as the strain increases.
The strain direction and magnitude detection principle:
arranging C-type resonators at different angles, arranging n C-type resonators, setting the angle of the first C-type resonator to be 0 degrees, numbering the other C-type resonators in a clockwise arrangement manner, and setting the angle of the ith C-type resonator to be theta i ；
The n C-shaped resonators only need to be arranged to ensure that the N C-shaped resonators cannot be influenced mutually, the specific value of the n C-shaped resonators does not need to be set, and the included angle of the symmetry axes of the adjacent C-shaped resonators can be set at any angle.
Those skilled in the art will appreciate that the line here is 0 degrees about the axis of symmetry of the first resonator, i.e. the angle theta i Is the angle between the symmetry axis of the ith C-type resonator and the symmetry axis of the first C-type resonator.
When the metal surface generates strain, a pair of stresses F with opposite directions acts on the object, the pair of forces is marked by the direction of the force with a smaller angle and is marked as theta', and therefore the included angle delta theta between the ith C-type resonator and the strain is marked as theta i ＝θ’-θ i . The strain is resolved along the xy direction of the C-type resonator, and the resonance frequency is affected by the xy direction partial strain, as shown in fig. 4.
The sensitivities of the C-type resonator resonance frequency to the strain in the x direction and the strain in the y direction are different, and the sensitivity coefficients of the ith C-type resonator to the strain in the x direction and the strain in the y direction are respectively assumed to be alpha i And beta i The sensitivity coefficient can be known by advance measurement, and equation (7) can be established, wherein alpha is i 、β i 、Δω i Is a known quantity, Δ θ i And F are unknown quantities.
Δθ i ＝θ’-θ i
α i F|sin△θ i |+β i F|cos△θ i |＝△ω xi +△ω yi ＝△ω i (7)
By arranging n resonators in a column, a system of equations (8) can be established, which is an over-determined system of equations, whose least squares solution is solved. I.e. to find the dependent variable which minimizes the value Q of the least squares function
And
s1, generating a broadband frequency-sweeping radio frequency signal: a broadband radio frequency generation and receiving device arranged h meters above the measured metal component generates a broadband frequency-sweeping radio frequency electromagnetic wave signal U with vertical polarization 1 ；
S2, attaching the RFID strain sensing label to the surface of the metal member;
s3, generating a broadband frequency-sweeping radio frequency signal: a broadband radio frequency generation and receiving device arranged h meters above the measured metal component generates a broadband frequency-sweeping radio frequency electromagnetic wave signal U with vertical polarization 2 ；
S4, generating a response signal: the vertical linear polarization antenna of the tag antenna attached to the surface of the metal component receives a vertically polarized broadband frequency-sweeping radio frequency electromagnetic wave signal U 2 Then, the main transmission line is transmitted to the horizontally polarized linear polarization transmitting antenna in the form of guided wave, and the guided wave frequency on the main transmission line is equal to the resonance frequency ω of the ith C-type resonator i When the signals (i, 1,2, n) are the same, the guided waves are transmitted into the resonant structure, the transmission coefficient of the main transmission line is attenuated, and the amplitude of the echo signal at the frequency is weakened; the frequency domain information of the horizontally polarized electromagnetic wave radio frequency response signal transmitted to the free space by the horizontally linearly polarized transmitting antenna comprises the filtering information of all C-type resonators;
s5, receiving the radio frequency response signal: the radio frequency receiving and transmitting module receives the radio frequency response signal and converts the U 2 And U 1 Input data acquisition and processing module and subtract the two to obtain U 3 . Data acquisition and processing module pair signal U 3 Analyzing to obtain a signal U 3 Frequency-amplitude curve f-a.
S6, extracting characteristic frequency: the resonance frequency f of the frequency-amplitude curve f-A detected in S4 is extracted i 。
S7 inversion of magnitude and direction of strain by frequency shift of resonance frequency
S71, establishing a positive relation between the frequency shift and the strain magnitude and direction: the ith resonator generates unit strain epsilon in the x and y directions of the metal specimen 0 The corresponding shift of the resonance frequency Δ ω is measured xi And Δ ω yi To find the sensitivity coefficients alpha in different directions i1 And alpha i2 And repeating the above process to obtain the sensitivity coefficients of all the resonators. (i ═ 1, 2.... times, n)
α i F sinθ i +β i F cosθ i ＝△ω xi +△ω yi ＝△ω i (10)
S72, when the metal test piece generates strain with unknown direction and unknown magnitude, the sensitivity coefficient and the resonance frequency shift of the ith resonator can establish an equation set containing n equations.
S73 finds the least squares solution of the above equation set. Strain to minimize Q
And an angle of 0 DEG
Namely, the following steps are obtained:
example (b):
the specific geometric parameters of the top metal patch are shown in FIG. 5, the material of the substrate is Rogers3003, and the dielectric constant3, loss tangent 0.0013 Poisson's ratio 0.4, Young's modulus 9X 10 8 Pa, density 2100kg/m 3 Thickness of substrate h 0 ＝1.6mm。
The width of each rectangle 1 is 26mm, and the length of each rectangle 2 is 14mm and 13 mm;
the main transmission line with the width of 4mm, which connects two orthogonal polarization antennas, consists of a patch structure, a dielectric substrate and a metal floor. The top patch structure of the main transmission line consists of three parts, namely an annular transmission line with an angle of 290 degrees (the inner diameter is 17mm, the outer diameter is 21mm), an annular transmission line with an angle of 100 degrees (the inner diameter is 4mm, the outer diameter is 8mm) and a rectangular transmission line with a length of 4mm and a width of 4 mm;
7C-type resonators,/, are provided i From 9.4mm to 8.2mm, step size 0.2 mm. The resonators are evenly distributed along the large loop transmission line from 0 to 270 with the angle definition seen in figure 13 and the angle between the resonators is 45. The resonator line width is 1mm and the short side length is 3 mm.
The linear polarization antenna works at 5.45-6.36GHz with the bandwidth of 910MHz, S 11 The parameters are shown in fig. 6.
Transmission coefficient S of main transmission line 21 As shown in fig. 7.
The relationship between the corresponding resonance frequency point and the resonator length is shown in fig. 8. It was fitted linearly, with a linear fit function f (x) -0.6489x + 11.56. The linearity R-square is 0.9991.
The resonant frequency is linear with respect to the strain in the xy direction. A C-type resonator having a length of 9mm and a width of 3mm was subjected to a tensile strain of 0 to 5% in the y-direction. The resonant frequency shifts towards low frequencies by 49.49MHz every 1% strain as shown in fig. 9 and 10. The linear fit R-square 0.9996 has the relationship f (x) 0.04949x + 5.648.
A tensile strain of 0-5% in the x-direction is applied. The resonant frequency shifts to high frequencies by 12.74MHz per 1% strain. As shown in fig. 11 and 12.
The simulation of the resonators with different lengths resulted in the xy direction sensitivities as shown in table 1.
TABLE 1 sensitivity coefficients
| Length (mm) | 9.4 | 9.2 | 9 | 8.8 | 8.6 | 8.4 | 8.2 |
| x |
12.89 | 12.81 | 12.74 | 12.66 | 12.59 | 12.52 | 12.45 |
| |
-51.67 | -50.59 | -49.49 | -48.39 | -47.29 | -46.19 | -45.09 |
The part under test developed a 1% strain at a 45 angle. As shown in fig. 13. The transmission coefficient is shown in fig. 14.
The values before and after the resonance frequency and the offset are shown in table 2.
TABLE 2 resonance frequency (MHz)
| Resonator length (mm) | 9.4 | 9.2 | 9 | 8.8 | 8.6 | 8.4 | 8.2 |
| Initial resonant frequency (MHz) | 5475.2 | 5589.1 | 5715.4 | 5842.8 | 5975.2 | 6114.7 | 6249.3 |
| Strain resonance frequency (MHz) | 5447.8 | 5538.5 | 5689.4 | 5855.5 | 5950.7 | 6068.5 | 6226.2 |
| Resonance frequency shift (MHz) | -27.4 | -50.6 | -26.0 | 12.7 | -24.5 | -46.2 | -23.1 |
Set forth the system of equations:
-45.09F|cosθ′|+12.45F|sinθ′|＝-27.4
-46.19F|cos(θ′-45°)|+12.52F|sin(θ′-45°)|＝-50.6
-47.29F|cos(θ′-90°)|+12.59F|sin(θ′-90°)|＝-26
-48.39F|cos(θ′-135°)|+12.66F|sin(θ′-135°)|＝12.7
-49.49F|cos(θ′-180°)|+12.74F|sin(θ′-180°)|＝-24.5
-50.59F|cos(θ′-225°)|+12.81F|sin(θ′-225°)|＝-46.2
-51.67F|cos(θ′-270°)|+12.89F|sin(θ′-270°)|＝-23.1 (13)
the solution using MATLAB is shown in fig. 15 and 16, and the results are given in table 3:
TABLE 3 actual and calculated values
| Actual value | Calculated value | Absolute error | Relative error | |
| Angle (°) | 45 | 45.0345 | 0.0345 | 0.077％ |
| Strain (%) | 1 | 1 | 0 | 0 |
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (8)
1. The utility model provides a chipless RFID strain sensing label which characterized in that, its structure from last to down be in proper order: a top metal patch, a dielectric substrate and a metal floor;
the top metal patch includes at least: a main transmission line and n C-type resonators which are obtained by connecting the orthogonal polarization antennas; the main transmission line is in an omega shape, and the n C-type resonators are arranged in the omega shape;
the main transmission line specifically includes: angle theta 1 2 angle theta 2 And 2 rectangular transmission lines, angle theta 1 The two ends of the annular transmission line respectively pass through 1 angle theta 2 The annular transmission line is connected with 1 rectangular transmission line;
the n C-type resonators are sequentially arranged at an angle theta 1 In the ring-shaped transmission line, n C-type resonator openings point to the angle theta 1 The symmetry axis of each C-type resonator passes through the angle theta 1 The center of the annular transmission line, the bottom of each C-type resonator and the angle theta 1 The distances between the ring transmission lines are the same.
2. The chipless RFID strain sensing tag of claim 1, wherein each C-type resonator is obtained by bending twice the same length transmission line.
3. The chipless RFID strain sensing tag of claim 2, wherein each C-type resonator has a bottom oriented at an angle θ 1 The annular transmission lines include a coupling capacitor therebetween.
4. The chipless RFID strain sensing tag of claim 3, wherein the top metal patch further comprises a top antenna connected to both ends of the main transmission line.
5. A nondestructive testing method for a chipless RFID strain sensing tag based on any one of claims 1-4 is characterized in that when strain occurs, the resonance frequency of a resonator changes, the resonance frequency of the resonator in changed frequency domain information is extracted, and the magnitude and direction of the strain are obtained through inversion.
6. The nondestructive testing method of claim 5, wherein the symmetry axis and the over angle θ of the ith resonator are recorded 1 The included angle between horizontal lines of the circle centers of the annular transmission lines is theta i If the strain angle is θ', the i-th resonator forms an angle Δ θ with the strain i ＝θ’-θ i Let the sensitivity coefficients of the ith C-type resonator to the strain in the x and y directions be alpha respectively i And beta i And (3) arranging n resonators in a formula, and obtaining an expression for solving an included angle between the strain size and the strain as follows:
wherein Q represents a function value,
the magnitude of the strain is shown as,
representing the included angle of strain.
7. The nondestructive testing method of claim 6, wherein the included angle between the strain magnitude and the strain is obtained by solving the least squares solution.
8. The nondestructive testing method according to claim 7, wherein the specific testing process is as follows:
s1, generating a broadband frequency-sweeping radio frequency signal: a broadband radio frequency generation and receiving device arranged h meters above the measured metal component generates a broadband frequency-sweeping radio frequency electromagnetic wave signal U with vertical polarization 1 ；
S2, attaching the RFID strain sensing label to the surface of the metal member;
S3generating a radio frequency signal of broadband frequency sweep: a broadband radio frequency generation and receiving device arranged h meters above the measured metal component generates a broadband frequency-sweeping radio frequency electromagnetic wave signal U with vertical polarization 2 ；
S4, generating a response signal: the vertical linear polarization antenna of the tag antenna attached to the surface of the metal component receives a vertically polarized broadband frequency-sweeping radio frequency electromagnetic wave signal U 2 Then, the main transmission line is transmitted to a horizontally polarized transmitting antenna in a guided wave mode, and the frequency domain information of the horizontally polarized electromagnetic wave radio frequency response signal transmitted to the free space by the horizontally linearly polarized transmitting antenna comprises the filtering information of all C-type resonators;
s5, receiving the radio frequency response signal: the radio frequency receiving and transmitting module receives the radio frequency response signal and converts the U 2 And U 1 Input data acquisition and processing module and subtract the two to obtain U 3 (ii) a Data acquisition and processing module pair signal U 3 Analyzing to obtain a signal U 3 Frequency-amplitude curve of (d);
s6, extracting characteristic frequency: extracting the resonant frequency f of the frequency-amplitude curve detected in S4 i ；
And S7, inverting the magnitude and direction of the strain through the frequency shift of the resonance frequency.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015195561A (en) * | 2014-03-27 | 2015-11-05 | サクラテック株式会社 | Multi-mode resonator and rfid tag employing the same |
| WO2016164970A1 (en) * | 2015-04-13 | 2016-10-20 | Rfid Technologies Pty Ltd | Rfid tag and reader |
| CN207216664U (en) * | 2017-08-14 | 2018-04-10 | 华南理工大学 | A kind of omnidirectional's chipless RFID label based on angle positioning |
| WO2018218313A1 (en) * | 2017-06-02 | 2018-12-06 | Monash University | Improved chipless rfid system and method |
| CN109165714A (en) * | 2018-08-07 | 2019-01-08 | 南京理工大学 | A kind of more bit coupled resonance Chip-free labels |
| US10211498B1 (en) * | 2018-05-08 | 2019-02-19 | King Saud University | Reconfigurable resonators for chipless RFID applications |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8857724B2 (en) * | 2009-03-10 | 2014-10-14 | Wal-Mart Stores, Inc. | Universal RFID tags and methods |
| US11093722B2 (en) * | 2011-12-05 | 2021-08-17 | Adasa Inc. | Holonomic RFID reader |
| US9824252B1 (en) * | 2016-05-13 | 2017-11-21 | Xerox Corporation | Chemical sensors based on chipless radio frequency identification (RFID) architectures |
| WO2019173264A1 (en) * | 2018-03-05 | 2019-09-12 | Board Of Trustees Of Michigan State University | Wireless detection of electrically or magnetically labeled analytes |
| WO2020021748A1 (en) * | 2018-07-24 | 2020-01-30 | 株式会社村田製作所 | Rfid tag reading antenna |
| JP2020181338A (en) * | 2019-04-24 | 2020-11-05 | 国立大学法人 東京大学 | RFID tag |
-
2021
- 2021-03-16 CN CN202110289713.4A patent/CN113065627B/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2015195561A (en) * | 2014-03-27 | 2015-11-05 | サクラテック株式会社 | Multi-mode resonator and rfid tag employing the same |
| WO2016164970A1 (en) * | 2015-04-13 | 2016-10-20 | Rfid Technologies Pty Ltd | Rfid tag and reader |
| WO2018218313A1 (en) * | 2017-06-02 | 2018-12-06 | Monash University | Improved chipless rfid system and method |
| CN207216664U (en) * | 2017-08-14 | 2018-04-10 | 华南理工大学 | A kind of omnidirectional's chipless RFID label based on angle positioning |
| US10211498B1 (en) * | 2018-05-08 | 2019-02-19 | King Saud University | Reconfigurable resonators for chipless RFID applications |
| CN109165714A (en) * | 2018-08-07 | 2019-01-08 | 南京理工大学 | A kind of more bit coupled resonance Chip-free labels |
Non-Patent Citations (1)
| Title |
|---|
| 一种新型的无芯片RFID双极化标签设计;左正璞等;《电子技术应用》;20171006(第10期);58-61 * |
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