Bridge structure deformation testing system based on microwave perception

Abstract

The application discloses a bridge structure deformation test system based on microwave sensing, and relates to the field of bridge deformation monitoring, and comprises a transmitting module, a receiving module and the like.The transmitting module is used for generating a microwave signal and transmitting the signal to a preset target test section on a bridge in a directional manner.The receiving module is used for capturing the microwave signal reflected by the target test section on the bridge, and outputting the signal after filtering and amplification matching the frequency of the transmitting signal.The application can generate a directional microwave signal and accurately transmit the signal to the target test section on the bridge, capture the reflected signal, and improve the signal quality through filtering, amplification and demodulation processing, effectively filter out environmental interference, extract multi-dimensional feature parameters from the processed signal, and construct a deformation calculation model in combination with basic information such as the size of the bridge section and the elastic modulus of the material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge deformation monitoring, in particular to a bridge structure deformation test system based on microwave sensing. BACKGROUND

[0002] The bridge structure deformation microwave sensing technology uses the penetration and anti-interference of microwave signals, emits microwaves through radar equipment, receives bridge reflection signals, analyzes signal phase / frequency changes, and inversely calculates deformation.

[0003] The invention patent application with application number 202510947855.3 discloses an online monitoring method for bridge structure deformation. The application aims to solve the problem that in the contact type bridge deformation monitoring method, the monitoring method based on GPS measurement technology is used for long-term deformation online monitoring of bridges due to its high precision, full automation, all-weather and other advantages, but this method ignores the short-term bridge displacement caused by bridge vibration due to external wind load and vehicle load in the bridge. These short-term bridge displacements will be captured by the GPS receiver and superimposed on the real data of bridge deformation monitoring, so that these short-term bridge displacements caused by external wind and driving load and other factors are mistaken for bridge structural deformation, thereby reducing the accuracy of bridge structure deformation monitoring.

[0004] Bridge deformation directly affects the safety performance of bridge daily use. In order to improve the accuracy, intelligence and real-time performance of bridge deformation monitoring, we propose a bridge structure deformation test system based on microwave sensing. SUMMARY

[0005] In view of the above shortcomings of the prior art, the present application provides a bridge structure deformation test system based on microwave sensing, which can effectively solve the problems of the prior art.

[0006] To achieve the above purpose, the present application is realized by the following technical scheme;

[0007] The present application discloses a bridge structure deformation test system based on microwave sensing, which comprises:

[0008] The transmission module is used for receiving the strain value and the deflection value of the bridge test section output by the operation module again, and comparing the strain value and the deflection value with preset safety threshold values respectively, determining whether the bridge structure has a deformation risk, and transmitting feedback of a determination result, the strain value and the deflection value to a preset feedback target.

[0009] Further, the transmission module includes a microwave signal generator, a reconfigurable beam transmission component, and a power adjustment unit.

[0010] The microwave signal generator is used for generating a continuous wave microwave signal with adjustable frequency, and the frequency adjustment range is 10GHz-30GHz, and the frequency resolution is ≤100Hz.

[0011] The reconfigurable beam transmission component is composed of a radiation unit array, a phase shifter network, and a beam control chip, the radiation unit array includes 16 microstrip patch units distributed in a regular hexagon, each microstrip patch unit controls a phase offset amount through an independent phase shifter, and the beam control chip calculates control voltages of the phase shifters based on preset target test section coordinate data and the following formula:

[0012] , V i represents the control voltage of the i th phase shifter, V represents a full-scale voltage, φ i represents a target phase offset amount of the i th radiation unit, , d i represents a distance between the i th radiation unit and the array center, θ and φ represent an azimuth angle and an elevation angle of the beam, λ represents a wavelength of the microwave signal;

[0013] The power adjustment unit introduces an environmental self-adaptive correction factor to adjust the final output power of the reconfigurable beam transmitting assembly to the target test section:

[0014]

[0015] In the formula: P is the final output power; P is the reference power; D is the reference distance; D is the actual distance between the transmitting module and the target test section; is the environmental attenuation coefficient; is the temperature correction coefficient; is the difference between the real-time temperature and the reference temperature; is the humidity correction coefficient; is the difference between the real-time humidity and the reference humidity;

[0016] wherein the environmental attenuation coefficient ∈[0.8,1.0], and the smaller the value is when the density of dust, water vapor condensate, and solid obstacles in the microwave signal transmission path is higher and the transmission distance is farther; The temperature correction coefficient is initially set to -0.002 / ℃, which is used to quantify the influence of temperature deviation from the reference value; and the humidity correction coefficient ∈-0.001 / %RH, which is used to quantify the influence of humidity deviation from the reference value, with the temperature reference value being 25℃ and the humidity reference value being 50%RH.

[0017] Further, the receiving module includes a low-noise amplifier, a band-pass filter, and a signal demodulation unit, the signal demodulation unit being a quadrature demodulation architecture for decomposing the received microwave signal into in-phase and quadrature baseband signals;

[0018] The low-noise amplifier limits the noise figure fluctuation within the working temperature range of -40℃~85℃ to not more than 0.3dB, and the gain adjustable range is 20dB-60dB;

[0019] The center frequency of the band-pass filter is consistent with the transmitting signal frequency, and the 3dB bandwidth is ≤100kHz to filter out the interference signals outside the same frequency band in the environment;

[0020] The signal demodulation unit includes a phase shifter and two mixers, wherein the phase shifter divides the local oscillation signal into two signals with a phase difference of 90°, which are input into the two mixers to mix with the received signal, and the output in-phase and quadrature baseband signals are sampled by 16-bit ADC and then subjected to interference suppression:​

[0021] ;

[0022] In the formula: 、 is the baseband signal after interference suppression; is the two-way baseband signal output by the receiving module through the quadrature demodulation architecture; is the interference suppression coefficient; is the reference channel output signal; is the phase difference of the transceiving channel;

[0023] Among them, the reference channel is the channel directly coupled to the original signal of the transmitting module, and the interference suppression coefficient ∈[0.1, 0.9], when the Pearson correlation coefficient of the interference signal captured by the reference channel and the main receiving channel is not less than 80%, the value of is greater, when the correlation Pearson correlation coefficient is less than 50%, the value of is smaller.

[0024] Further, the extraction operation in the extraction module is subject to:

[0025] Phase offset extraction: using the combination of wavelet transform and Hilbert-Huang transform, the I / Q signal is decomposed by EMD to obtain 8 intrinsic mode functions, the IMF components with the top 3 energy ratios are selected to reconstruct the signal, and the phase offset is calculated , denote the amplitude of the quadrature baseband signal after Hilbert-Huang transform decomposition reconstruction, the amplitude of the in-phase baseband signal after Hilbert-Huang transform decomposition reconstruction, denotes the initial phase of the transmitting signal;

[0026] Frequency change amount extraction: based on the reconstructed signal, the instantaneous frequency is calculated, and the frequency change gradient is calculated by sliding Fourier transform, then the final frequency change amount ;

[0027] In the formula: is the first derivative operator with respect to time t; is the instantaneous frequency at time ; is the instantaneous frequency at time ; is the time interval; is the instantaneous frequency at the current time t; is the initial microwave signal frequency output by the transmitting module; is the gradient correction coefficient; is the frequency change gradient;

[0028] Amplitude variation rate extraction: calculate the synthetic amplitude based on the original in-phase and quadrature baseband signals output by the receiving module , I and Q represent the original in-phase and quadrature baseband signals output by the quadrature demodulation unit of the receiving module; through variational mode decomposition, the original in-phase and quadrature baseband signals are decomposed into three modal components , which correspond to the instantaneous fluctuation, short-term trend and long-term drift of the signal respectively; finally, the amplitude variation rate is calculated , wi represents the weight coefficient of the i-th modal component; represents the instantaneous variation rate of the i-th modal component, that is, the process of taking the time-domain derivative of ; is the initial synthetic amplitude, which takes the synthetic amplitude value of the first sampling point after the system starts;

[0029] where the gradient correction coefficient takes a value subject to: when the microwave echo signal-to-noise ratio is not less than 40 dB, take 0.15-0.2, otherwise take 0.05-0.1; the weight coefficient of the modal component takes a value subject to: the sum of all modal classification weight coefficients is 1, and each modal component weight coefficient is positive; the higher the signal-to-noise ratio of the modal component, the larger the weight coefficient value of the modal component, and vice versa.

[0030] Further, in the process of converting the feature parameters into strain values and deflection values of the bridge test section in the operation module, a material nonlinearity correction term is introduced:

[0031] Strain calculation sub-model: , is the actual strain value of the bridge target test section; is the wavelength of the microwave signal output by the transmitting module; is the phase shift of the microwave signal obtained by the extraction module; is the length of the bridge target test section; is the elastic modulus of the bridge concrete; is the material nonlinearity correction coefficient; is the phase threshold corresponding to the yield of the concrete material; is the hardening index of the concrete material;

[0032] Deflection calculation sub-model: , is the actual deflection value of the bridge target test section; is the speed of light in a vacuum; is the frequency change of the microwave signal obtained by the extraction module; is the initial frequency of the microwave signal output by the transmitting module;​ The rate of change of microwave signal amplitude obtained by the extraction module; The height of the target test section of the bridge; The density of the bridge concrete; These are geometric nonlinearity correction coefficients; The initial deflection value of the target test section of the bridge;

[0033] Among them, the material nonlinearity correction coefficient ∈[0.02, 0.08], the value is larger when the load on the bridge concrete test section is greater and the concrete strength grade is lower, and vice versa; geometric nonlinearity correction coefficient ∈[0.15, 0.3], the larger the bridge span of the target test section of the bridge, the larger the value, and vice versa.

[0034] Furthermore, the preset standard deformation database in the correction module includes standard strain values ​​of the bridge under static load, dynamic load, and temperature load conditions. Standard deflection value And the corresponding standard characteristic parameters, including standard phase offset, standard frequency change, and standard amplitude change rate;

[0035] The calibration command generation process is as follows: the strain value output by the calculation module and... deviation rate and deflection value and deviation rate ,like >5% or If the value is greater than 5%, a calibration instruction will be generated.

[0036] Control commands for the transmitting module: Adjust microwave signal frequency deviation ;

[0037] Control commands for the receiving module: Adjust the bandwidth of the bandpass filter. ;

[0038] Control instructions for the computation module: Correct the coefficients of the deformation calculation model. The corrected strain value is The deflection value is ;

[0039] In the formula: The initial microwave signal frequency output by the transmitting module; This represents the initial bandwidth of the bandpass filter in the receiving module.

[0040] Furthermore, the deformation risk determination logic in the transmission module is as follows:

[0041] Calculate the comprehensive risk index , is a strain limit threshold value, is a deflection limit threshold value, is a deformation rate, is a deformation rate limit threshold value;

[0042] The preset safety threshold is initially set to [0, 0.5), R < 0.5 is risk-free, 0.5 ≤ R < 1.0 is low risk, 1.0 ≤ R < 1.5 is medium risk, and R ≥ 1.5 is high risk;

[0043] When the risk is high, millimeter wave frequency band transmission is used, the working frequency of the millimeter wave frequency band is 28 GHz, and the transmission bandwidth is dynamically adjusted according to the comprehensive risk index: ;

[0044] When the risk is medium, 3.5 GHz frequency band transmission is used, the transmission interval is seconds;

[0045] When the risk is low and risk-free, a low-power wide-area transmission architecture is used, and the architecture carrier frequency is in the range of 433 MHz-915 MHz, the spread spectrum factor is in the range of 12-16, and the receiving sensitivity is ≤-148 dBm, and the transmission period is shortened as R increases: , seconds, is used to represent the transmission period in the low-risk and risk-free scenarios.

[0046] Further, the beam control chip of the reconfigurable beam transmitting component in the transmitting module first calibrates the preset target test section coordinate data through the built-in coordinate calibration unit before calculating the control voltage of each phase shifter, and the calibration process is:

[0047] A three-dimensional rectangular coordinate system is established with the installation position of the transmitting module as the origin, the actual coordinate values of the four vertices of the target test section in the coordinate system are obtained, the average value of the four vertex coordinates is calculated as the center coordinate of the calibrated target test section, and the control voltage of each phase shifter is calculated based on the calibrated coordinate;

[0048] In the phase offset extraction process in the extraction module, the wavelet basis function of wavelet transform is db4 wavelet, the decomposition layer is set to 5 layers, and the EMD decomposition termination condition of Hilbert Huang transform is that the energy difference of the intrinsic mode functions obtained by adjacent two times of decomposition is less than 0.01%;

[0049] In the frequency change amount extraction process, the sliding window length of the sliding Fourier transform is set to 512 sampling points, and the time interval is 0.001 seconds;

[0050] In the amplitude change rate extraction process, the penalty factor of the variational mode decomposition is set to 2000, and the noise tolerance is set to 0.001.

[0051] Further, in the preset standard deformation database of the correction module, the division standards of static load, dynamic load and temperature load working conditions are:

[0052] The static load working condition refers to the working condition of the bridge under constant load and the load value does not exceed 50% of the design load, the dynamic load working condition refers to the working condition of the bridge under periodic load and the load change frequency is in the range of 0.1Hz-5Hz, and the temperature load working condition refers to the working condition of the bridge under the condition that the ambient temperature changes more than 5℃ within 24 hours, and the standard strain value, standard deflection value and corresponding standard characteristic parameters under each working condition are obtained based on more than 100 repeated tests on the bridge test piece with the same structure type and material parameters as the test bridge.

[0053] The calculation method of the deformation rate in the transmission module is:

[0054] The time interval of adjacent two groups of data is calculated by selecting three groups of strain values and deflection values continuously received by the transmission module, and the average value of the ratio of strain value change amount to corresponding time interval and the ratio of deflection value change amount to corresponding time interval is taken as the deformation rate

[0055] When the transmission module determines the deformation risk of the bridge structure based on the comprehensive risk index, if the continuous three determination results are inconsistent, the determination result with the highest occurrence frequency is selected as the final risk determination result, and if the three determination results are different, the intermediate risk level is taken as the final risk determination result.

[0056] Further, the receiving module is interactively connected with the extraction module through a wireless network, the extraction module is interactively connected with the operation module through a wireless network, the operation module is interactively connected with the correction module through a wireless network, and the correction module is interactively connected with the transmission module through a wireless network.

[0057] Compared with the known prior art, the technical scheme provided by the present application has the following beneficial effects:

[0058] The present application provides a bridge structure deformation test system based on microwave perception, which can generate directional microwave signals and accurately transmit them to the target test section of the bridge during operation, capture reflected signals, filter, amplify and demodulate the signals to improve signal quality, effectively filter out environmental interference, extract multi-dimensional feature parameters from the processed signals, construct a deformation calculation model combined with basic information such as bridge section size and material elastic modulus, and accurately convert the feature parameters into strain values and deflection values of the bridge by introducing material nonlinear and geometric nonlinear correction terms.​​

[0059] Meanwhile, calibration instructions are generated based on a preset standard deformation database, signal parameters and calculation model coefficients are dynamically regulated to optimize calculation results, and by comparing strain values and deflection values with preset safety thresholds, combining with deformation rate calculation to calculate a comprehensive risk index, and according to risk levels, a transmission frequency band, bandwidth and period that are suitable are flexibly selected, efficient and accurate feedback of test data and risk determination results is realized, which can adapt to different load working conditions and environmental conditions, guarantee the accuracy, stability and timeliness of bridge deformation testing, and identify deformation risks in time to provide support for bridge structure safety monitoring and maintenance. BRIEF DESCRIPTION OF DRAWINGS

[0060] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0061] Figure 1 Fig. 1 is a structural schematic diagram of a bridge structure deformation testing system based on microwave perception;

[0062] Figure 2 Fig. 2 is a schematic diagram of a test section position of the application scenario one;

[0063] Figure 3 Fig. 3 is a vibration pickup arrangement diagram of the application scenario two. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] The present application will be further described below in combination with the embodiments.

[0066] Embodiment:

[0067] The bridge structure deformation testing system based on microwave perception of the present embodiment, as shown in Fig. 1, comprises: Figure 1

[0068] The transmitting module is used for generating a microwave signal and directing the signal to be transmitted to a preset target test section on the bridge;

[0069] ​The transmitting module comprises a microwave signal generator, a reconfigurable beam transmitting assembly and a power adjusting unit;

[0070] The microwave signal generator is used for generating a continuous wave microwave signal with adjustable frequency, the frequency adjustment range being 10GHz-30GHz and the frequency resolution being ≤100Hz;

[0071] The reconfigurable beam transmitting assembly is composed of an array of radiating units, a network of phase shifters and a beam control chip, the array of radiating units comprising 16 microstrip patch units arranged in a regular hexagon, each microstrip patch unit being controlled by an independent phase shifter, and the beam control chip calculating the control voltage of each phase shifter based on preset target test section coordinate data and the following formula:

[0072] , V i represents the control voltage of the i th phase shifter, V represents the full-scale voltage, θ i represents the target phase shift of the i th radiating unit, , d i represents the distance between the i th radiating unit and the array center, θ and φ represent the azimuth angle and the elevation angle of the beam, λ represents the wavelength of the microwave signal;

[0073] The above formula takes the physical layout of the array of radiating units and the beam pointing requirement as the core, converts the spatial parameters such as the distance between the i th radiating unit and the array center, the azimuth angle and the elevation angle of the beam, and the wavelength of the microwave signal into the target phase shift, and establishes a linear mapping relationship between the phase and the control voltage based on the full-scale voltage, so as to ensure that each microstrip patch unit can accurately adjust the phase to form a directional beam. It breaks through the traditional fixed beam design, realizes accurate signal coverage of any preset test section of the bridge through 16 independent phase control units arranged in a regular hexagon and dynamic voltage calculation, solves the problem of insufficient signal transmission directivity under complex structure, and improves the targeting of the test target;

[0074] The power adjusting unit introduces an environmental adaptive correction factor to adjust the final output power of the reconfigurable beam transmitting assembly transmitted to the target test section:

[0075] ;

[0076] In the formula: P represents the final output power; P 0 represents the reference power; d 0 represents the reference distance; d represents the actual distance between the transmitting module and the target test section; α represents the environmental attenuation coefficient; β represents the temperature correction coefficient; is the difference between the real-time temperature and the reference temperature; is the humidity correction coefficient; is the difference between the real-time humidity and the reference humidity;

[0077] wherein the environmental attenuation coefficient ∈[0.8,1.0] and decreases as the density of dust, water vapor condensate and solid obstacles in the microwave signal transmission path increases and the transmission distance increases; The temperature correction coefficient is initially set to -0.002 / ℃ and is used to quantify the influence of temperature deviation from the reference value; the humidity correction coefficient ∈-0.001 / %RH is used to quantify the influence of humidity deviation from the reference value, and the temperature reference value is 25℃ and the humidity reference value is 50%RH;

[0078] The above formula is based on the reference power and the reference distance, introduces the inverse square relationship of the actual transmission distance to compensate for signal attenuation, and innovatively incorporates the environmental attenuation coefficient, the temperature correction coefficient and the humidity correction coefficient to quantify the influence of dust, water vapor and other obstacles and the influence of temperature and humidity deviation from the reference value on signal power, respectively. This multi-factor coupled power adjustment method breaks the traditional single attenuation model that only considers distance, so that the output power can adapt to complex environmental changes in real time, ensuring the power stability of the microwave signal reaching the test section under different working conditions, and providing a reliable signal basis for subsequent signal reception and feature extraction;

[0079] Before calculating the control voltage of each phase shifter, the beam control chip of the reconfigurable beam transmitting assembly in the transmitting module first calibrates the preset target test section coordinate data through the built-in coordinate calibration unit. The calibration process is as follows:

[0080] A three-dimensional rectangular coordinate system is established with the installation position of the transmitting module as the origin, the actual coordinate values of the four vertices of the target test section in the coordinate system are obtained, the average of the four vertex coordinates is calculated as the center coordinate of the calibrated target test section, and then the control voltage of each phase shifter is calculated based on the calibrated coordinate;

[0081] The receiving module is used to capture the microwave signal reflected by the target test section on the bridge, and outputs after filtering and amplification matching the frequency of the transmitted signal;

[0082] The receiving module includes a low-noise amplifier, a band-pass filter and a signal demodulation unit. The signal demodulation unit is a quadrature demodulation architecture and is used to decompose the received microwave signal into in-phase and quadrature baseband signals;

[0083] The low-noise amplifier has a noise coefficient fluctuation of not more than 0.3dB within a working temperature range of -40℃ to 85℃, and a gain adjustable range of 20dB-60dB;

[0084] The center frequency of the band-pass filter is consistent with the frequency of the transmitted signal, and the 3dB bandwidth is less than or equal to 100kHz, so as to filter out the interference signals in the environment outside the same frequency band;

[0085] The signal demodulation unit comprises a phase shifter and two mixers, wherein the phase shifter divides the local oscillation signal into two signals with a phase difference , which are input into the two mixers respectively to mix with the received signal, and the in-phase and quadrature baseband signals output are sampled by 16-bit ADC and then subjected to interference suppression:

[0086]

[0087] In the formula, , is the baseband signal after interference suppression; is the two baseband signals output by the receiving module through the quadrature demodulation architecture; is the interference suppression coefficient; is the reference channel output signal; is the phase difference of the transceiver channel;

[0088] The reference channel is a channel directly coupled to the original signal of the transmitting module, and the interference suppression coefficient ∈[0.1, 0.9], when the Pearson correlation coefficient of the interference signal captured by the reference channel and the interference signal of the main receiving channel is not less than 80%, the greater the value, when the correlation Pearson correlation coefficient is less than 50%, the smaller the value;

[0089] The above formula is based on the original baseband signal output by the quadrature demodulation, by introducing the reference channel directly coupled to the transmitted signal, using the interference suppression coefficient to establish the correlation between the original signal and the reference signal, and combining the phase difference of the transceiver channel to calibrate the signal phase, so as to filter out the same frequency interference in the environment. It dynamically adjusts the interference suppression coefficient through the Pearson correlation coefficient, increases the coefficient when the reference channel and the main receiving channel interference correlation is high to strengthen the suppression effect, and vice versa to avoid signal distortion, solves the problem that the traditional fixed filter is difficult to adapt to the dynamic interference scene, and significantly improves the signal-to-noise ratio of the baseband signal;

[0090] The extraction module is used to obtain the microwave signal output by the receiving module, and extract the phase offset, frequency change and amplitude change rate from the microwave signal, and transmit the phase offset, frequency change and amplitude change rate as feature parameters to the operation module;

[0091] The extraction operation in the extraction module is subject to:

[0092] ​Phase shift extraction: A combination of wavelet transform and Hilbert-Huang transform is used to perform EMD decomposition on the I / Q signal to obtain 8 intrinsic mode functions (IMFs). The top 3 IMF components by energy percentage are selected to reconstruct the signal, and then the phase shift is calculated. , This represents the amplitude of the quadrature baseband signal after Hilbert-Huang transform decomposition and reconstruction, and the amplitude of the in-phase baseband signal after Hilbert-Huang transform decomposition and reconstruction. Indicates the initial phase of the transmitted signal;

[0093] Frequency change extraction: Calculation of instantaneous frequency based on reconstructed signal The frequency gradient is calculated using the sliding Fourier transform. The final frequency change ;

[0094] In the formula: The first derivative operator with respect to time t; For a moment The instantaneous frequency; For a moment The instantaneous frequency; For time intervals; Let be the instantaneous frequency at the current time t; The initial microwave signal frequency output by the transmitting module; These are gradient correction coefficients; The gradient represents the frequency change.

[0095] The above formula uses a sliding Fourier transform to sample the instantaneous frequency of the reconstructed signal in the time domain, obtaining the instantaneous frequency difference between adjacent moments and the current moment. Then, a gradient correction coefficient is introduced to calibrate the frequency change gradient, and finally, the frequency change is obtained by combining this with the initial microwave frequency. The gradient correction coefficient is dynamically determined based on the echo signal-to-noise ratio (SNR), breaking through the traditional fixed-coefficient calculation mode. This ensures calculation accuracy under high SNR while reducing errors under low SNR, achieving accurate extraction of frequency changes under different signal qualities and providing reliable parameters for subsequent deflection calculations.

[0096] Amplitude change rate extraction: Calculate the synthesized amplitude based on the original phase and cross-path baseband signals output by the receiving module. , These represent the original in-phase baseband signal and the original quadrature baseband signal output by the quadrature demodulation unit of the receiving module, respectively; through variational mode decomposition... Decomposed into 3 modal components These correspond to the instantaneous fluctuation, short-term trend, and long-term drift of the signal, respectively; finally, the rate of change of amplitude is calculated. , The weighting coefficient for the i-th modal component; represents the instantaneous change rate of the i th modal component, that is, represents the change of the amplitude of the original baseband signal the process of time domain derivation; is the initial synthesized amplitude, taking the synthesized amplitude value of the first sampling point after the system starts;

[0097] The above formula calculates the synthesized amplitude based on the original baseband signal, and then decomposes the synthesized amplitude into three modal components of instantaneous fluctuation, short-term trend and long-term drift through variational modal decomposition. Subsequently, according to the signal-to-noise ratio of each modal component, a weight coefficient is allocated. Finally, the amplitude change rate is obtained by the sum of the product of the instantaneous change rate of each component and the weight, combined with the initial synthesized amplitude. The innovation lies in distinguishing the amplitude change components of different characteristics through modal decomposition, and dynamically allocating weights according to the signal-to-noise ratio, avoiding the interference of noise or trend components in single signal analysis, and realizing the fine extraction of amplitude change rate, providing more comprehensive feature support for deformation calculation;

[0098] The gradient correction coefficient is The value is subject to: when the microwave echo signal-to-noise ratio is not less than 40 dB, take 0.15-0.2, otherwise take 0.05-0.1, the weight coefficient of the modal component is subject to: the sum of all modal classification weight coefficients is 1, and each modal component weight coefficient is positive, the higher the signal-to-noise ratio of the modal component, the greater the weight coefficient value of the modal component, and vice versa;

[0099] In the phase offset extraction process in the extraction module, the wavelet basis function of wavelet transform is db4 wavelet, and the decomposition layer is set to 5 layers. The EMD decomposition termination condition of Hilbert Huang transform is that the energy difference of the intrinsic mode function obtained by adjacent two times of decomposition is less than 0.01%;

[0100] In the frequency change amount extraction process, the sliding window length of sliding Fourier transform is set to 512 sampling points, and the time interval The value is 0.001 seconds;

[0101] In the amplitude change rate extraction process, the penalty factor of variational modal decomposition is set to 2000, and the noise tolerance is set to 0.001;

[0102] The operation module is used to store the length, width, height and elastic modulus of concrete and material information of the target test section, and simultaneously receive the feature parameters output by the extraction module to create a deformation calculation model. The deformation calculation model in the operation module converts the feature parameters into strain values and deflection values of the bridge test section and outputs them.

[0103] In the process of converting the feature parameters into strain values and deflection values of the bridge test section in the deformation calculation model in the operation module, a material nonlinear correction term is introduced:

[0104] The strain calculation sub-model is: , is the actual strain value of the bridge target test section; is the wavelength of the microwave signal output by the emission module; is the phase shift of the microwave signal obtained by the extraction module; is the length of the bridge target test section; is the elastic modulus of the bridge concrete; is the material nonlinear correction coefficient; is the phase threshold corresponding to the yield of the concrete material; is the hardening index of the concrete material;

[0105] The above formula takes the wavelength and phase shift of the microwave signal as the core parameters, establishes a basic strain relationship in combination with the length of the test section, and introduces the elastic modulus of the concrete, the material nonlinear correction coefficient, the yield phase threshold, and the hardening index to quantify the nonlinear characteristics of the concrete material in the stress process. The material nonlinear correction coefficient is dynamically valued according to the load size and the concrete strength grade, breaks through the traditional linear strain calculation model, can accurately reflect the strain change law of the concrete material from the elastic stage to the plastic stage, and makes the calculation result more consistent with the actual stress deformation state of the bridge;

[0106] Deflection calculation sub-model: , is the actual deflection value of the bridge target test section; is the speed of light in a vacuum; is the frequency change of the microwave signal obtained by the extraction module; is the initial frequency of the microwave signal output by the emission module; is the amplitude change rate of the microwave signal obtained by the extraction module; is the height of the bridge target test section; is the density of the bridge concrete; is the geometric nonlinear correction coefficient; is the initial deflection value of the bridge target test section;

[0107] The above formula establishes the relationship between distance change and frequency based on the speed of light, the initial microwave frequency, and the frequency change, and integrates the amplitude change rate, the test section height, the concrete density, and the geometric nonlinear correction coefficient to obtain the actual deflection in combination with the initial deflection value. The geometric nonlinear correction coefficient is dynamically valued according to the bridge span, innovatively combines the frequency change and the amplitude change, and considers the influence of the structure geometric size on the deflection, breaks through the traditional deflection calculation mode which only relies on a single parameter, can accurately capture the geometric nonlinear deformation of the large-span bridge under stress, and improves the applicability and precision of the deflection calculation;

[0108] wherein the material nonlinear correction coefficient The bridge concrete test section bears a greater load, and the concrete strength grade is lower, and the value is greater, and vice versa, the value is smaller; the geometric nonlinear correction coefficient The bridge target test section bears a greater load, and the concrete strength grade is lower, and the value is greater, and vice versa, the value is smaller;

[0109] The correction module receives the calculation result output by the operation module, generates a calibration instruction based on a preset standard deformation database, applies the calibration instruction to respectively regulate the microwave signal of the transmitting module, the processing parameter of the receiving module and the model coefficient of the deformation calculation module, and jumps to the operation module to run again, and outputs the strain value and the deflection value of the bridge test section;

[0110] The preset standard deformation database in the correction module includes standard strain values , standard deflection values and corresponding standard characteristic parameters under the working conditions of static load, dynamic load and temperature load, including standard phase offset, standard frequency change and standard amplitude change rate.

[0111] The generation process of the calibration instruction is: calculating the deviation rate of the strain value output by the operation module and , and the deviation rate of the deflection value and , if >5% or >5%, a calibration instruction is generated:

[0112] The regulation instruction for the transmitting module: adjusting the frequency deviation of the microwave signal;

[0113] The regulation instruction for the receiving module: adjusting the bandwidth of the band-pass filter;

[0114] The regulation instruction for the operation module: correcting the deformation calculation model coefficient , the corrected strain value is , and the deflection value is ;

[0115] In the formula: is the initial microwave signal frequency output by the transmitting module; is the initial bandwidth of the band-pass filter in the receiving module;

[0116] In the above setting, the frequency deviation adjustment formula is based on the initial microwave frequency, dynamically corrects the frequency according to the strain and deflection deviation rate, and ensures that the transmitted signal matches the test requirements; the bandwidth adjustment formula is based on the initial bandpass filter bandwidth, optimizes the filtering range in combination with the deviation rate, and improves the interference filtering effect; the corrected strain and deflection formula reduces the error between theoretical calculation and actual deformation by introducing a deviation correction term to the original calculation result. The innovation lies in that the standard deformation database is used as a reference, and multiple modules are calibrated in coordination through the deviation rate, rather than a single module adjustment, forming a closed loop of "calculation-comparison-correction-re-calculation", solving the long-term drift problem caused by fixed parameters in traditional systems, and continuously ensuring the deformation calculation accuracy.

[0117] In the preset standard deformation database of the correction module, the division standards of static load, dynamic load and temperature load working conditions are:

[0118] The static load working condition refers to the working condition of the bridge under constant load and the load value does not exceed 50% of the design load, the dynamic load working condition refers to the working condition of the bridge under periodic load and the load change frequency is between 0.1Hz and 5Hz, and the temperature load working condition refers to the working condition of the bridge under the condition that the ambient temperature changes more than 5℃ within 24 hours, and the standard strain value, standard deflection value and corresponding standard characteristic parameters under each working condition are obtained based on more than 100 repeated tests on bridge test specimens with the same structure type and material parameters as the test bridge.

[0119] The transmission module is used to receive the strain value and deflection value of the bridge test section output by the operation module again when the correction module triggers the operation module to run again, compare the strain value and deflection value with the preset safety threshold value respectively, determine whether the bridge structure has deformation risk, and transmit the determination result, strain value and deflection value to the preset feedback target for feedback;

[0120] The deformation risk determination logic in the transmission module is:

[0121] Calculate the comprehensive risk index , is the strain limit threshold value, is the deflection limit threshold value, is the deformation rate, is the deformation rate limit threshold value;

[0122] The preset safety threshold value is initially set to [0, 0.5), then R<0.5 is risk-free, 0.5≤R<1.0 is low risk, 1.0≤R<1.5 is medium risk, and R≥1.5 is high risk;

[0123] When the risk is high, the millimeter wave frequency band is used for transmission, the working frequency of the millimeter wave frequency band is 28GHz, and the transmission bandwidth is dynamically adjusted according to the comprehensive risk index: ;

[0124] transmission interval , unit: second;

[0125] Low-risk and no-risk transmission using low-power wide-area transmission architecture, and the architecture carrier frequency is in the range of 433MHz-915MHz, the spread spectrum factor is in the range of 12-16, the receiving sensitivity is ≤-148dBm, and the transmission period is shortened as R increases: , unit: second, for indicating the transmission period under low-risk and no-risk scenarios;

[0126] the calculation method of the deformation rate in the transmission module is:

[0127] Select 3 groups of strain values and deflection values continuously received by the transmission module, calculate the time interval of the adjacent two groups of data, and take the average value of the ratio of the strain value change amount to the corresponding time interval and the ratio of the deflection value change amount to the corresponding time interval as the deformation rate ;

[0128] When the transmission module determines the bridge structure deformation risk based on the comprehensive risk index, if the continuous 3 times of determination results are inconsistent, the determination result with the most occurrences among them is selected as the final risk determination result, and if the 3 times of determination results are all different, the intermediate risk level is taken as the final risk determination result;

[0129] The receiving module is connected with the extraction module through a wireless network, the extraction module is connected with the operation module through a wireless network, the operation module is connected with the correction module through a wireless network, and the correction module is connected with the transmission module through a wireless network.

[0130] ​In the embodiment, the transmitting module first generates a microwave signal with a frequency adjustable from 10 GHz to 30 GHz, transmits the signal in the direction of the target test section coordinate through the reconfigurable beam transmitting assembly, and adjusts the output power in combination with the environmental factors by the power adjusting unit; the receiving module amplifies the signal through a low-noise amplifier, filters the signal through a band-pass filter with the same frequency as the transmitting signal, decomposes the signal through a quadrature demodulation architecture, samples the signal through a 16-bit ADC, and performs interference suppression processing; the extracting module extracts three types of characteristic parameters, i.e., phase shift, frequency change, and amplitude change rate, from the received signal by using a wavelet transform combined with a Hilbert Huang (HHT) transform; the operation module calls the pre-stored bridge section size and material information, converts the characteristic parameters into strain values and deflection values through a deformation calculation model containing material and geometric nonlinear correction terms; the correction module compares the operation results with the pre-set standard deformation database data, generates a calibration instruction if the deviation rate exceeds 5%, respectively adjusts the frequency of the transmitting module, the filter bandwidth of the receiving module, and the model coefficients of the operation module, and triggers the operation module to recalculate; the transmission module receives the corrected strain values and deflection values, calculates a comprehensive risk index to determine the risk level, adopts the corresponding frequency band and transmission parameters according to the level, and feeds back the determination results and data to the pre-set target.

[0131] In the bridge deformation test of the system in the above embodiment, the bridge reflection signal can be accurately captured, the key parameters can be extracted through processing, the strain and deflection values can be calculated in combination with the bridge information, the optimization results can be calibrated according to the standard database to ensure the accuracy of the data, the bridge deformation risk can be judged, the transmission mode and parameters can be dynamically adjusted according to the risk level, the results can be fed back in time, the bridge safety monitoring can be effectively ensured, the monitoring efficiency and reliability can be improved, accurate data support can be provided for bridge maintenance, and safety hazards can be reduced.

[0132] It should be noted that in the specific implementation scenarios of the above embodiments:

[0133] Regarding the calibration termination condition, a maximum calibration frequency threshold (e.g., 3 times) is set. If the deviation rate is still greater than 5% after the number of continuous calibrations reaches the threshold, a fault alarm is triggered and the current deviation data is recorded, and the system automatically switches to a backup test mode (e.g., redundant sensor data is enabled) to avoid infinite loops. If the deviation rate is less than or equal to 5% within the threshold number of times, the calibration is terminated and the current calibration parameters are saved.

[0134] Regarding the time interval for calculating the deformation rate, when the system is running, the sampling time interval of the last three groups of strain values and deflection values is a fixed value (e.g., 1 second), and the interval is not affected by the transmission period. The time interval is ensured to be uniform by an independent timing module, and the deformation rate calculation formula is uniformly set as the difference between the last group of data and the first group of data divided by the fixed time interval. The average value of the calculation results of three times is taken as the final deformation rate.

[0135] Regarding the way of obtaining key parameters:

[0136] The phase threshold corresponding to the yield of the concrete material is obtained through uniaxial compression tests of the same batch of concrete test pieces, and when the stress-strain curve shows a clear yield platform, the corresponding microwave phase offset is recorded as the threshold at the same time;

[0137] The hardening index is determined by fitting the microwave test data of more than 10 test pieces, referring to the material parameters of concrete with the same strength grade in the Code for Design of Concrete Structures;

[0138] The IMF component energy ratio is calculated according to the ratio of the root mean square energy of each component to the total energy, and the threshold is set to the first 3 components when the cumulative energy ratio is ≥90%.

[0139] In addition, in the reconfigurable beam transmitting assembly:

[0140] The array of radiation units uses a 4x4 microstrip patch antenna array, and each array element is connected to a phase shifter network through an SMA interface;

[0141] The phase shifter selects a 6-bit digital phase shifter model HMC547LP4E, and the beam control chip (optional model STM32F407) outputs a control voltage (0-5V) to the phase shifter through an SPI interface;

[0142] In the quadrature demodulation architecture:

[0143] The phase shifter is set to a fixed 90° phase difference, and the mixer selects an ADL5801 chip (operating frequency 10GHz-30GHz), and its output is connected to an operational amplifier AD8065 through an RC low-pass filter (cutoff frequency 100kHz).

[0144] Below, in the above-mentioned embodiment, an application example of the system is shown:

[0145] I. Engineering background

[0146] This application example is aimed at the S43 Airport Expressway Shibugeng Interchange A Ramp Bridge K1+388.357~K1+478.357 section (3x30m cast-in-place prestressed concrete continuous box girder). The bridge has a total length of 90.0m, the superstructure is a cast-in-place prestressed concrete continuous box girder, the beam height is 1.8m, the cantilever length is 1.8m, the bridge deck transverse slope is 2%, the longitudinal slope is -0.4%, the design load is highway-I level, the concrete uses C50, the elastic modulus is 3.45x10 4 MPa, and the unit weight is 26kN / m³. In order to accurately grasp the structural deformation of the bridge under static load and dynamic load conditions and verify whether its bearing capacity meets the design requirements, a bridge structure deformation test system based on microwave sensing is introduced for deformation monitoring.

[0147] II. System deployment and parameter setting

[0148] (I) Transmitting module deployment and parameter configuration

[0149] The transmitting module is installed on the stable area of one side of the bridge. A three-dimensional rectangular coordinate system is established with the transmitting module installation position as the origin. The coordinates of the four vertices of the target test section (the maximum positive bending moment A-A section of the 30th span, the negative bending moment B-B section of the top of the AP30 pier, and the maximum positive bending moment C-C section of the 31st span) are collected. The average of the coordinates is calculated to obtain the center coordinates of each test section, which are used as the target points for directional transmission of the microwave signal.

[0150] The microwave signal generator in the transmitting module generates a continuous wave microwave signal with adjustable frequency. Considering the electromagnetic interference in the bridge test environment, the initial frequency is set to 20 GHz (within the adjustment range of 10 GHz-30 GHz, with a frequency resolution of 80 Hz, which meets the requirement of ≤100 Hz). The reconfigurable beam transmitting assembly includes 16 microstrip patch elements arranged in a regular hexagon. According to the center coordinates of the target test section (taking the A-A section as an example, the coordinates are X=15 m, Y=0 m, and Z=1.8 m), the target phase offset of each radiation element is calculated. Then, combined with the full-scale voltage of 10 V, the control voltage of each phase shifter is calculated using the control voltage calculation formula, which is between 1.2 V and 3.5 V. This realizes the directional transmission of the microwave signal to the test section.

[0151] For the power adjustment unit, the reference power P0 is set to 15 dBm, the reference distance d0 is set to 20 m, the actual distance d between the transmitting module and the A-A section is 18 m. The actual temperature is 28℃ (with a difference ΔT of 3℃ from the reference temperature of 25℃), the actual humidity is 55%RH (with a difference ΔH of 5%RH from the reference humidity of 50%RH), and the environmental attenuation coefficient n is 0.92 (within the interval of 0.8-1.0) according to the dust and water vapor conditions on site. The temperature correction coefficient k1 is -0.002 / ℃, and the humidity correction coefficient kh is -0.001 / %RH. Substituting these values into the power calculation formula, the final output power Pou is calculated to be 14.8 dBm, ensuring stable transmission of the microwave signal to the target test section.

[0152] (II) Deployment and parameter configuration of the receiving module

[0153] The receiving module is installed on the same side as the transmitting module and maintains the same axis as the transmitting module. It is used to capture the reflected microwave signal of each test section. The working temperature of the low-noise amplifier is set to -40℃~85℃. Combined with the actual temperature of 28℃, the gain is adjusted to 40 dB (within the adjustable range of 20 dB-60 dB). The noise coefficient fluctuation is 0.2 dB, which meets the requirement of ≤0.3 dB. The center frequency of the bandpass filter is consistent with the frequency of the transmitting signal, which is 20 GHz. The 3dB bandwidth is 80 kHz (≤100 kHz), effectively filtering out the out-of-band interference signals in the environment.

[0154] The signal demodulation unit adopts a quadrature demodulation architecture. A phase shifter divides the local oscillation signal into two signals with a phase difference of 90°, which are input into two mixers for mixing with the received signal. The output in-phase and quadrature baseband signals are sampled by a 16-bit ADC and then subjected to interference suppression. The interference signal is captured by a reference channel (directly coupled to the original signal of the transmitting module), and the Pearson correlation coefficient of the interference signal and the main receiving channel is calculated to be 85% (≥80%). The interference suppression coefficient a is set to 0.7, which is substituted into the interference suppression formula to process the baseband signal and reduce the influence of environmental interference on the signal quality.

[0155] (Three) Parameter input of operation module

[0156] In the operation module, the structural parameters of each test section are pre-recorded: the A-A section length is 18 m (corresponding to the bridge transverse width, which conforms to the actual range of bridge width 0.5 m + 14.37 ~ 11.07 m + 0.5 m), the height is 1.8 m (beam height); the B-B section length is 18 m, the height is 1.8 m; the C-C section length is 18 m, the height is 1.8 m; at the same time, the material information such as the elastic modulus of C50 concrete 3.45 × 10 4 MPa, density 2600 kg / m³, etc. are recorded, which provides basic data for the deformation calculation model.

[0157] Three, data acquisition and processing

[0158] (One) Feature parameter extraction

[0159] Phase shift extraction: After the receiving module outputs the microwave signal, the extraction module uses a combination of wavelet transform (wavelet base function db4 wavelet, 5 layers of decomposition) and Hilbert Huang transform to perform EMD decomposition on the I / Q signal, obtaining 8 intrinsic mode functions. The reconstructed signal of the top 3 IMF components is selected. After calculation, the reconstructed orthogonal baseband signal amplitude of A-A section is 2.5 V, the in-phase baseband signal amplitude is 2.3 V, the initial phase of the transmitting signal is 0°, and finally the phase shift of A-A section is 0.02 rad, B-B is -0.015 rad, and C-C section is 0.018 rad.

[0160] Frequency change amount extraction: based on the reconstructed signal to calculate the instantaneous frequency, set the time interval At=0.001 seconds, calculate the frequency change gradient by sliding Fourier transform (sliding window length 512 sampling points). The measured A-A section at t+At moment instantaneous frequency is 20.0001GHz, t-At moment instantaneous frequency is 19.9999GHz, the current moment instantaneous frequency is 20GHz, the initial frequency of emission is 20GHz, the microwave echo signal-to-noise ratio is 45dB (≥40dB), the gradient correction coefficient is 0.18, and the frequency change amount calculation formula is obtained. The frequency change amount of A-A section is 0.00012GHz, the frequency change amount of B-B section is-0.00009GHz, and the frequency change amount of C-C section is 0.0001GHz.

[0161] Amplitude change rate extraction: calculate the received module output original baseband signal synthesis amplitude A(t), and carry out variational mode decomposition (penalty factor 2000, noise tolerance 0.001) on A(t). The decomposition is divided into three modal components (instantaneous fluctuation, short-term trend, long-term drift), and the weight coefficients of each modal component are determined according to the signal-to-noise ratio, which are 0.3, 0.4 and 0.3 (the sum is 1). Calculate the instantaneous change rate of each modal component, the initial synthesis amplitude is 2.4V, and the amplitude change rate calculation formula is obtained. The amplitude change rate of A-A section is 0.002 , the amplitude change rate of B-B section is-0.0015 , and the amplitude change rate of C-C section is 0.0018s .

[0162] (II) Deformation calculation

[0163] Strain value calculation: combined with the extracted characteristic parameters and the stored structure and material parameters in the operation module, A-A section bears larger load, concrete strength grade is C50, material nonlinear correction coefficient is 0.06 (in 0.02-0.08 interval), concrete material yield corresponding phase threshold is 0.05 rad, and hardening index is 0.8. Submodel for strain calculation, microwave wavelength λ is calculated according to initial frequency 20GHz and light speed 3×10 8 m / s, 0.015m, and finally A-A section strain value is 85, B-B section Ɛ=-65, and C-C section strain value is 78.

[0164] Deflection value calculation: A-A section bridge span is 30m, geometric nonlinear correction coefficient is 0.25 (in 0.15-0.3 interval), and initial deflection value is 0mm. Submodel for deflection calculation.

[0165] Four, data correction and risk judgment

[0166] (I) Data correction

[0167] The correction module calls a preset standard deformation database (containing standard strain, deflection and corresponding standard characteristic parameters of the same type C50 concrete 3x30m continuous beam under static load, dynamic load and temperature load working conditions, which is obtained by more than 100 repeated tests on bridge test specimens with the same structural type and material parameters as the test bridge, meeting the requirements of the technical scheme), and calculates the deviation rate of the output results of the calculation module from the standard values. The A-A section strain deviation rate is 3.2% (≤5%), the deflection deviation rate is 2.8% (≤5%), the B-B section strain deviation rate is 4.5% (≤5%), the C-C section strain deviation rate is 3.8% (≤5%), and the deflection deviation rate is 3.1% (≤5%), all meeting the accuracy requirements, without generating calibration instructions, and directly using the current calculation results.

[0168] (II) Deformation risk judgment

[0169] The transmission module calls a preset safety threshold [0, 0.5], combines the strain limit threshold, the deflection limit threshold, and the deformation rate limit threshold, selects three groups of strain and deflection data, calculates the time interval of the adjacent two groups of data, and the strain change amounts are 5 and 4, respectively, and the deflection change amounts are 0.3mm and 0.2mm, respectively, and obtains a deformation rate of 0.45mm / s.

[0170] Substitute the comprehensive risk index calculation formula, calculate A-A section R=0.42, B-B section R=0.38, C-C section R=0.40, all less than 0.5, and judge as no risk.

[0171] The transmission module uses a low-power wide-area transmission architecture, the carrier frequency is set to 868MHz (in the range of 433MHz-915MHz), the spread factor is 14 (in the range of 12-16), and the receiving sensitivity is -150dBm (≤-148dBm). According to the comprehensive risk index R=0.40, substitute the transmission period calculation formula, obtain the transmission period as 30s, pack the strain value, deflection value and no risk judgment result, and transmit to the preset bridge operation and maintenance management platform.

[0172] Five, application effect verification

[0173] Compare the test results of the microwave sensing system with the test results of the traditional displacement meter and strain gauge, the A-A section strain measured value deviates from the traditional test value by 2.4%, and the deflection measured value deviates from the traditional test value by 1.9%; the C-C section strain measured value deviates from the traditional test value by 2.6%, and the deflection measured value deviates from the traditional test value by 2.1%, the deviation is within 5%, verifying the accuracy of the system test data.

[0174] Reference Figure 2As shown in the figure, the figure is a bridge structure deformation test performed by the system in the embodiment;

[0175] The observed cross section and measurement contents are shown in the following table:

[0176] Working condition Observation section position Measurement content Working condition 1 Maximum positive bending moment of the 1st span (A-A section) Concrete strain, deflection, and support settlement of the box girder Working condition 2 Negative bending moment at the top of the 1st pier (B-B section) Concrete strain of the box girder Working condition 3 Maximum positive bending moment at the middle of the 2nd span (C-C section) Concrete strain, deflection, and support settlement of the box girder

[0177] Referring to Figure 3 As shown in the figure, the modal test acquisition module is used to determine the vibration mode, frequency, damping ratio and other dynamic parameters of the bridge under dynamic load. The vibration pickup is arranged longitudinally along the bridge at 1 / 4L, 1 / 2L and 3 / 4L of each span of the detection link, and is arranged vertically and perpendicular to the bridge deck to determine the vertical vibration response of the bridge. The transverse arrangement is about 30 cm away from the crash barrier. After determining the measurement point position, the vibration pickup is leveled with plasticine and coupled with the bridge deck. The measurement point arrangement is shown in Figure 3 As shown in the figure.

[0178] In summary, the system in the above embodiment can generate directional microwave signals and accurately transmit them to the target test section of the bridge during operation. After capturing the reflected signals, the signal quality is improved through filtering, amplification and demodulation processing, and environmental interference is effectively filtered out. The multi-dimensional feature parameters are extracted from the processed signals, and a deformation calculation model is constructed by combining the bridge section size, material elastic modulus and other basic information. By introducing material nonlinearity and geometric nonlinearity correction terms, the feature parameters are accurately converted into strain values and deflection values of the bridge. Based on the preset standard deformation database, calibration instructions are generated to dynamically control the signal parameters and calculation model coefficients to optimize the calculation results. By comparing the strain values and deflection values with the preset safety threshold, and combining the deformation rate to calculate the comprehensive risk index, the appropriate transmission frequency band, bandwidth and period are selected according to the risk level to realize efficient and accurate feedback of test data and risk judgment results. It can adapt to different load working conditions and environmental conditions, ensure the accuracy, stability and timeliness of the bridge deformation test, and timely identify the deformation risk to provide support for bridge structure safety monitoring and maintenance.

[0179] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A microwave perception based bridge structure deformation testing system, characterized in that, The method comprises the following steps: The transmitting module is used for generating a microwave signal and transmitting the signal to a preset target test section on the bridge in a directional manner; The receiving module is used for capturing the microwave signal reflected by the target test section on the bridge, and outputting the signal after filtering and amplification matching the frequency of the transmitting signal; The extracting module is used for obtaining the microwave signal output by the receiving module, extracting the phase offset, frequency change and amplitude change rate in the microwave signal, and transmitting the phase offset, frequency change and amplitude change rate to the operation module as characteristic parameters; The operation module is used for storing the length, width, height and concrete elastic modulus and material information of the target test section, synchronously receiving the characteristic parameters output by the extracting module, creating a deformation calculation model, and converting the characteristic parameters into strain values and deflection values of the bridge test section by using the deformation calculation model and outputting the strain values and deflection values; The correction module is used for receiving the calculation results output by the operation module, generating a calibration instruction based on a preset standard deformation database, adjusting the microwave signal of the transmitting module, the processing parameters of the receiving module and the model coefficients of the deformation calculation module by using the calibration instruction, and jumping to the operation module again for operation and outputting the strain values and deflection values of the bridge test section; The transmission module is used for receiving the strain values and deflection values of the bridge test section output by the operation module again when the operation module is triggered again by the correction module, comparing the strain values and deflection values with preset safety thresholds respectively, determining whether the bridge structure has a deformation risk, and transmitting the determination result, the strain values and the deflection values to a preset feedback target for feedback.

2. The microwave perception based bridge structure deformation testing system of claim 1, wherein, The transmitting module comprises a microwave signal generator, a reconfigurable beam transmitting assembly and a power adjusting unit; The microwave signal generator is used for generating a continuous wave microwave signal with adjustable frequency, and the frequency adjusting range is 10GHz-30GHz, and the frequency resolution is ≤100Hz; The reconfigurable beam transmitting assembly is composed of a radiation unit array, a phase shifter network and a beam control chip, the radiation unit array comprises 16 microstrip patch units arranged in a regular hexagon, each microstrip patch unit controls a phase offset by using an independent phase shifter, and the beam control chip calculates the control voltage of each phase shifter based on preset target test section coordinate data and the following formula: Vci represents the control voltage of the i-th phase shifter, Vrepresents the full-scale voltage, φti represents the target phase shift of the i-th radiating element, di represents the distance of the i-th radiating element from the array center, θ, φ represent the azimuth angle, the elevation angle of the beam, λ represents the wavelength of the microwave signal;​​ The power adjusting unit introduces an environment adaptive correction factor to adjust the final output power of the reconfigurable beam transmitting assembly to the target test section: ； In the formula: is the final output power; is the reference power; is the reference distance; is the actual distance between the transmitting module and the target test section; is the environmental attenuation coefficient; is the temperature correction coefficient; is the difference between the real-time temperature and the reference temperature; is the humidity correction coefficient; is the difference between the real-time humidity and the reference humidity; Wherein, the environmental attenuation coefficient ∈[0.8, 1.0], and the smaller the value is, the higher the density of dust, water vapor condensate and solid obstacles in the microwave signal transmission path is, and the farther the transmission distance is The temperature correction coefficient The initial setting is -0.002 / ℃, which is used to quantify the influence of temperature deviation from the reference value; the humidity correction coefficient ∈-0.001 / %RH, which is used to quantify the influence of humidity deviation from the reference value, the temperature reference value is 25℃, and the humidity reference value is 50%RH.

3. The microwave perception based bridge structure deformation testing system as claimed in claim 1, wherein, The receiving module comprises a low-noise amplifier, a band-pass filter and a signal demodulation unit, the signal demodulation unit is a quadrature demodulation architecture, and is used for decomposing the received microwave signal into in-phase and quadrature baseband signals; The low-noise amplifier limits the noise coefficient fluctuation to not more than 0.3dB within the working temperature range of-40℃~85℃, and the gain adjusting range is 20dB-60dB; The center frequency of the band-pass filter is consistent with the frequency of the transmitting signal, and the 3dB bandwidth is ≤100kHz, so as to filter out the interference signals outside the same frequency band in the environment; The signal demodulation unit comprises a phase shifter and two mixers, wherein the phase shifter divides the local oscillation signal into two signals with a phase difference of 90 degrees, which are respectively input into the two mixers to mix with the received signal, and the in-phase and quadrature-phase baseband signals output are sampled by 16-bit ADCs and then subjected to interference suppression. ； In the formula: , is the baseband signal after interference removal; is the two-way baseband signal output by the receiving module through the quadrature demodulation architecture; is the interference suppression coefficient; is the reference channel output signal; is the phase difference of the transceiving channel; Wherein, the reference channel is the channel directly coupled with the original signal of the transmitting module, the interference suppression coefficient ∈[0.1, 0.9], when the Pearson correlation coefficient of the interference signal captured by the reference channel and the interference signal of the main receiving channel is not less than 80%, the interference suppression coefficient The greater the value, when the correlation Pearson correlation coefficient is less than 50%, The smaller the value.

4. The microwave perception based bridge structure deformation testing system of claim 1, wherein, The extraction operation in the extracting module is subject to: Phase shift extraction: the I / Q signal is decomposed by EMD to obtain 8 intrinsic mode functions in combination of wavelet transform and Hilbert Huang transform, the signal is reconstructed by selecting the top 3 IMF components in terms of energy proportion, and the phase shift is calculated , denotes the amplitude of the quadrature baseband signal reconstructed by Hilbert Huang transform, the amplitude of the in-phase baseband signal reconstructed by Hilbert Huang transform, denotes the initial phase of the transmitted signal; Frequency change extraction: computation of instantaneous frequency based on the reconstructed signal The frequency change gradient is computed by a sliding Fourier transform The final frequency change is then ; In the formula: is a first-order derivative operator with respect to time t; is the instantaneous frequency at time is the instantaneous frequency at time is a time interval; is the instantaneous frequency at the current time t; is the initial microwave signal frequency output by the transmitting module; is a gradient correction coefficient; is a frequency change gradient;​​ Amplitude variation rate extraction: calculate the synthesized amplitude based on the original in-phase and quadrature baseband signals output by the receiving module , respectively represent the original in-phase and quadrature baseband signals output by the quadrature demodulation unit of the receiving module; the original in-phase and quadrature baseband signals are decomposed into three modal components by variational mode decomposition , respectively corresponding to the instantaneous fluctuation, short-term trend and long-term drift of the signal; finally, the amplitude variation rate is obtained , is the weight coefficient of the i-th modal component; represents the instantaneous variation rate of the i-th modal component, that is, it represents the process of time-domain derivation on ; is the initial synthesized amplitude, taking the synthesized amplitude value of the first sampling point after the system starts;​ wherein the gradient correction coefficient The value is subject to: when the microwave echo signal-to-noise ratio is not less than 40dB, 0.15-0.2 is taken, otherwise 0.05-0.1 is taken, the weight coefficient of the modal component is subject to: the sum of all modal classification weight coefficients is 1, and the weight coefficient of each modal component is positive, the higher the signal-to-noise ratio of the modal component, the greater the weight coefficient value of the modal component, otherwise the value is smaller.

5. The microwave perception based bridge structure deformation testing system of claim 1, wherein, In the operation module, a material nonlinear correction term is introduced in the process of converting the characteristic parameters into the strain values and deflection values of the bridge test section: Strain calculation sub-model: , is the actual strain value of the bridge target test section; is the wavelength of the microwave signal output by the emission module; is the phase offset of the microwave signal obtained by the extraction module; is the length of the bridge target test section; is the elastic modulus of the bridge concrete; is the material nonlinear correction coefficient; is the phase threshold corresponding to the yield of the concrete material; is the hardening index of the concrete material; Deflection calculation submodel: , is the actual deflection value of the bridge target test section; is the speed of light in a vacuum; is the frequency change of the microwave signal obtained by the extraction module; is the initial frequency of the microwave signal output by the transmission module; is the amplitude change rate of the microwave signal obtained by the extraction module; is the height of the bridge target test section; is the density of the bridge concrete; is the geometric nonlinear correction coefficient; is the initial deflection value of the bridge target test section; Wherein, the material nonlinear correction coefficient ∈ [0.02, 0.08], the greater the load of the test section of the bridge concrete, the lower the concrete strength grade, the greater the value, otherwise, the smaller the value; geometric nonlinear correction coefficient ∈ [0.15, 0.3], the greater the bridge span of the target test section of the bridge, the greater the value, otherwise, the smaller the value.

6. The microwave perception based bridge structure deformation testing system of claim 5, wherein, The preset standard deformation database in the correction module includes standard strain values of the bridge under static load, dynamic load and temperature load working conditions , standard deflection values , and corresponding standard characteristic parameters, including standard phase offset, standard frequency change amount and standard amplitude change rate; The calibration command generation process is as follows: the strain value output by the calculation module and... deviation rate and deflection value and deviation rate ,like >5% or If the value is greater than 5%, a calibration instruction will be generated. Control instruction to the transmitting module: adjust the frequency deviation of the microwave signal ; Modulation instruction to the receiving module: adjust the band pass filter bandwidth ; The control instruction of the operation module: correct the deformation calculation model coefficient The corrected strain value is The deflection value is ; In the formula: is the initial microwave signal frequency output by the transmitting module; is the initial bandwidth of the band-pass filter in the receiving module.

7. The microwave perception based bridge structure deformation testing system of claim 6, wherein, The transformation module includes a deformation risk determination logic, and the deformation risk determination logic includes the following steps: computing a composite risk index , is a strain limit threshold, is a deflection limit threshold, is a deformation rate, is a deformation rate limit threshold; The preset safety threshold is initially set as [0, 0.5), and R < 0.5 is no risk, 0.5 <= R < 1.0 is low risk, 1.0 <= R < 1.5 is medium risk, and R >= 1.5 is high risk; High-risk time to use millimeter wave frequency band transmission, millimeter wave frequency band of 28GHz, transmission bandwidth according to the dynamic adjustment of the comprehensive risk index: ; Medium risk uses 3.5 GHz band for transmission, transmission interval in seconds; Low-risk and no-risk time to use low-power wide-area transmission architecture, and the architecture carrier frequency is in the range of 433MHz-915MHz, the spread spectrum factor is in the range of 12-16, the receiving sensitivity is ≤-148dBm, and the transmission period is shortened as R increases: , unit: seconds, For the transmission period in the low-risk and no-risk scenarios.

8. The microwave perception based bridge structure deformation testing system of claim 1, wherein, The beam control chip of the reconfigurable beam transmitting assembly in the transmitting module first calibrates the preset target test section coordinate data through a built-in coordinate calibration unit before calculating the control voltage of each phase shifter, and the calibration process includes the following steps: A three-dimensional rectangular coordinate system is established with the installation position of the transmitting module as the origin, actual coordinate values of four vertices of the target test section in the coordinate system are obtained, an average value of the four vertex coordinates is calculated as the center coordinate of the calibrated target test section, and the control voltage of each phase shifter is calculated based on the calibrated coordinate; In the phase offset extraction process in the extraction module, the wavelet basis function of the wavelet transform is db4 wavelet, the decomposition layer is set to 5 layers, and the EMD decomposition termination condition of the Hilbert Huang transform is that the energy difference of the intrinsic mode functions obtained by adjacent two times of decomposition is less than 0.01%. In the frequency variation amount extraction process, the sliding window length of the sliding Fourier transform is set to 512 sampling points, and the time interval is 0.001 seconds. In the amplitude change rate extraction process, the penalty factor of the variational mode decomposition is set to 2000, and the noise tolerance is set to 0.

001.

9. The microwave perception based bridge structure deformation testing system of claim 1, wherein, In the preset standard deformation database of the correction module, the division standards of the static load, dynamic load and temperature load working conditions are as follows: The static load working condition refers to a working condition in which the bridge bears a constant load and the load value does not exceed 50% of the design load, the dynamic load working condition refers to a working condition in which the bridge bears a periodically changing load and the load change frequency is within 0.1Hz-5Hz, and the temperature load working condition refers to a working condition in which the ambient temperature of the bridge changes by more than 5℃ within 24 hours, and the standard strain value, standard deflection value and corresponding standard characteristic parameters under each working condition are obtained based on a bridge specimen with the same structure type and material parameters as the test bridge through more than 100 times of repeated tests; The rate of deformation in the transmission module is calculated as follows: Select 3 groups of strain values and deflection values continuously received by the transmission module, calculate the time interval of adjacent two groups of data, and take the average value of the ratio of strain value change amount to corresponding time interval and the ratio of deflection value change amount to corresponding time interval as the deformation rate ; When the transmission module determines the bridge structure deformation risk based on the comprehensive risk index, if the consecutive three determination results are inconsistent, the determination result with the highest occurrence frequency is selected as the final risk determination result, and if the three determination results are all different, the intermediate risk level is taken as the final risk determination result.

10. The microwave perception based bridge structure deformation testing system of claim 1, wherein, The receiving module is connected to the extraction module through a wireless network, the extraction module is connected to the operation module through a wireless network, the operation module is connected to the correction module through a wireless network, and the correction module is connected to the transmission module through a wireless network.

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