Bridge structure deformation test system based on microwave sensing

Abstract

The invention discloses a bridge structure deformation test system based on microwave sensing, and relates to the field of bridge deformation monitoring, and the system comprises a transmitting module which is used for generating a microwave signal and directionally transmitting the signal to a preset target test section on a bridge; the receiving module is used for capturing the microwave signal reflected by the target test section on the bridge, and outputting the microwave signal after filtering processing and amplification matched with the frequency of the transmitted signal; the directional microwave signal can be generated and accurately transmitted to the bridge target test section, the reflected signal is captured and then filtered, amplified and demodulated to improve the signal quality, environmental interference is effectively filtered out, multi-dimensional characteristic parameters are extracted from the processed signal, and the detection accuracy is improved. A deformation calculation model is constructed by combining basic information such as bridge section size and material elasticity modulus.

Description

Technical Field

[0001] This invention relates to the field of bridge deformation monitoring technology, specifically a bridge structural deformation testing system based on microwave sensing. Background Technology

[0002] Microwave sensing technology for bridge structural deformation utilizes the penetrability and anti-interference properties of microwave signals. It transmits microwaves through equipment such as radar, receives the reflected signals from the bridge, and analyzes the phase / frequency changes of the signals to inversely reflect the deformation.

[0003] Patent application No. 202510947855.3 discloses an online monitoring method for bridge structural deformation. This application aims to solve the problem that "in contact-based bridge deformation monitoring methods, GPS measurement technology is used for long-term online monitoring of bridge deformation due to its advantages such as high accuracy, full automation, and all-weather operation. However, this method ignores the short-term bridge displacement caused by external wind loads and vehicle loads on the bridge. These short-term bridge displacements are captured by the GPS receiver and superimposed on the real data of bridge deformation monitoring. This causes these short-term bridge displacements caused by external wind force and traffic loads to be mistakenly identified as bridge structural deformation, thereby reducing the accuracy of bridge structural deformation monitoring."

[0004] Bridge deformation directly affects the safety performance of bridges in daily use. To improve the accuracy, intelligence and real-time performance of bridge deformation monitoring, we propose a bridge structural deformation testing system based on microwave sensing. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the present invention provides a bridge structure deformation testing system based on microwave sensing, which can effectively solve the problems of the existing technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions;

[0007] This invention discloses a bridge structure deformation testing system based on microwave sensing, comprising:

[0008] The transmitting module generates a microwave signal and transmits it directionally to a pre-defined target test section on the bridge. The receiving module captures the microwave signal reflected from the target test section, filters it to match the transmitted signal frequency, and amplifies it before outputting the signal. The extraction module acquires the microwave signal output from the receiving module, extracts phase shift, frequency change, and amplitude change rate from the signal, and transmits these parameters as feature parameters to the calculation module. The calculation module stores the length, width, and height of the target test section, as well as the concrete's elastic modulus and material information. It synchronously receives the feature parameters output from the extraction module to create a deformation calculation model, and then uses this model to transform the feature parameters into... The system outputs the strain and deflection values ​​of the bridge test section. A correction module receives the calculation results from the calculation module, generates calibration instructions based on a preset standard deformation database, and uses these instructions to adjust the microwave signal of the transmitting module, the processing parameters of the receiving module, and the model coefficients of the deformation calculation module. It then jumps back to the calculation module to run again, outputting the strain and deflection values ​​of the bridge test section. A transmission module receives the strain and deflection values ​​of the bridge test section again when the calculation module is triggered by the correction module. Based on comparisons of the strain and deflection values ​​with preset safety thresholds, it determines whether the bridge structure has a deformation risk and packages the determination result along with the strain and deflection values ​​to a preset feedback target for transmission.

[0009] Furthermore, the transmitting module includes a microwave signal generator, a reconfigurable beam transmitting component, and a power adjustment unit;

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

[0011] The reconfigurable beam transmitting component consists of a radiating element array, a phase shifter network, and a beam control chip. The radiating element array contains 16 microstrip patch units arranged in a regular hexagonal pattern. Each microstrip patch unit controls the phase shift through an independent phase shifter. The beam control chip calculates the control voltage of each phase shifter based on preset target test section coordinate data and the following formula:

[0012] , This represents the control voltage of the i-th phase shifter. This represents the full-scale voltage. This represents the target phase offset of the i-th radiating element. , Let be the distance between the i-th radiating element and the array center. For the azimuth and elevation angles of the beam, The wavelength of the microwave signal;

[0013] The power conditioning unit incorporates an environmental adaptive correction factor to adjust the final output power transmitted by the reconfigurable beam transmitting assembly to the target test section.

[0014] ;

[0015] In the formula: This refers to the final output power; Reference power; Used as the reference distance; This refers to the actual distance between the launch module and the target test section; Environmental degradation coefficient; This is a temperature correction factor; This is the difference between the real-time temperature and the reference temperature. This is the humidity correction factor; This represents the difference between the real-time humidity and the reference humidity.

[0016] Among them, the environmental attenuation coefficient ∈[0.8,1.0], and subject to the condition that the higher the density of dust, water vapor condensate, and physical obstacles in the microwave signal transmission path, and the longer the transmission distance, the better. The smaller the value, the better the temperature correction factor. The initial setting is -0.002 / ℃, used to quantify the impact of temperature deviation from the baseline value; humidity correction factor. ∈-0.001 / %RH, used to quantify the impact of humidity deviation from the baseline value, where the temperature baseline value is 25℃ and the humidity baseline value is 50%RH.

[0017] Furthermore, the receiving module includes a low-noise amplifier, a bandpass filter, and a signal demodulation unit. The signal demodulation unit is an orthogonal demodulation architecture used to decompose the received microwave signal into in-phase and quadrature baseband signals.

[0018] The low-noise amplifier is limited to a noise figure fluctuation of no more than 0.3dB within an operating temperature range of -40℃ to 85℃, and the gain is adjustable from 20dB to 60dB.

[0019] The center frequency of the bandpass filter is the same as the frequency of the transmitted signal, and the 3dB bandwidth is ≤100kHz, so as to filter out interference signals outside the same frequency band in the environment.

[0020] The signal demodulation unit includes Phase shifter and two mixers, of which The phase shifter divides the local oscillation signal into phase difference signals. The two signals are input to two mixers respectively to mix with the received signal. The output phase and crossover baseband signals are sampled by a 16-bit ADC and then subjected to interference suppression.

[0021] ;

[0022] In the formula: , This is the baseband signal after interference removal; The receiving module outputs two baseband signals through an orthogonal demodulation architecture; This is the interference suppression coefficient; For reference channel output signal; The phase difference between the transmit and receive channels;

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

[0024] Furthermore, the extraction module performs the following operations:

[0025] 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;

[0026] 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 ;

[0027] 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.

[0028] 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; Let represent the instantaneous rate of change of the i-th modal component, that is, to represent the change of . The process of performing time-domain differentiation; The initial synthesized amplitude is the synthesized amplitude value of the first sampling point after the system starts.

[0029] Among them, gradient correction coefficient The values ​​are determined as follows: when the microwave echo signal-to-noise ratio is not less than 40dB, the value is 0.15-0.2; otherwise, the value is 0.05-0.1. The weight coefficients of the modal components are determined as follows: the sum of the weight coefficients of all modal classifications is 1, and the weight coefficients of each modal component are positive numbers. The higher the signal-to-noise ratio of a modal component, the larger the weight coefficient of that modal component, and vice versa.

[0030] Furthermore, in the process of converting characteristic parameters into strain and deflection values ​​of the bridge test section, the deformation calculation model in the calculation module introduces a material nonlinearity correction term:

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

[0032] Deflection calculation sub-model: , The actual deflection value of the target test section of the bridge; The speed of light in a vacuum; The frequency change of the microwave signal obtained by the extraction module; The initial frequency for 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 , The strain limit threshold The deflection limit threshold. For deformation rate, This represents the deformation rate limit threshold.

[0042] The preset safety threshold is initially set to [0, 0.5). Then, 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.

[0043] In high-risk situations, millimeter-wave frequency band transmission is used. The operating frequency of the millimeter-wave frequency band is 28 GHz, and the transmission bandwidth is dynamically adjusted according to the comprehensive risk index. ;

[0044] For medium-risk situations, the 3.5GHz frequency band is used for transmission, with a transmission interval of [missing information]. The unit is seconds;

[0045] In low-risk and no-risk scenarios, a low-power wide-area transmission architecture is adopted, with the carrier frequency ranging from 433MHz to 915MHz, the spreading factor from 12 to 16, and the receiver sensitivity ≤ -148dBm. The transmission period shortens as R increases. The unit is seconds. Used to indicate the transmission cycle in low-risk and risk-free scenarios.

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

[0047] A three-dimensional rectangular coordinate system is established with the installation position of the launch module as the origin. The actual coordinate values ​​of the four vertices of the target test section in this coordinate system are obtained. The average value of the coordinates of the four vertices is calculated as the center coordinate of the target test section after calibration. Then, the control voltage of each phase shifter is calculated based on the calibrated coordinates.

[0048] In the phase offset extraction process of the extraction module, the wavelet basis function of the wavelet transform is selected as db4 wavelet, the number of decomposition layers is set to 5, and the EMD decomposition of Hilbert-Huang transform terminates when the energy difference of the intrinsic mode functions obtained from two adjacent decompositions is less than 0.01%.

[0049] During the extraction of frequency changes, the sliding window length of the sliding Fourier transform is set to 512 sampling points, and the time interval is... The value is 0.001 seconds;

[0050] During the amplitude change rate extraction process, the penalty factor for variational mode decomposition was set to 2000, and the noise tolerance was set to 0.001.

[0051] Furthermore, in the preset standard deformation database of the correction module, the classification criteria for static load, dynamic load, and temperature load conditions are as follows:

[0052] The static load condition refers to the condition where the bridge is subjected to a constant load and the load value does not exceed 50% of the design load. The dynamic load condition refers to the condition where the bridge is subjected to a periodically changing load and the load change frequency is between 0.1Hz and 5Hz. The temperature load condition refers to the condition where the ambient temperature of the bridge changes by more than 5℃ within 24 hours. The standard strain value, standard deflection value and corresponding standard characteristic parameters under each condition are obtained by more than 100 repeated tests on bridge specimens with the same structural type and material parameters as the tested bridge.

[0053] Deformation rate in the transmission module The calculation method is as follows:

[0054] Three sets of strain and deflection values ​​received continuously by the transmission module are selected. The time interval between two adjacent sets of data is calculated. The average of the ratios of the strain value change to the corresponding time interval and the deflection value change to the 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 results of three consecutive determinations are inconsistent, the determination result with the most occurrences shall be selected as the final risk determination result. If the three determination results are different, the intermediate risk level shall be used as the final risk determination result.

[0056] Furthermore, the receiving module interacts with the extraction module via a wireless network, the extraction module interacts with the computing module via a wireless network, the computing module interacts with the correction module via a wireless network, and the correction module interacts with the transmission module via a wireless network.

[0057] Compared with the known prior art, the technical solution provided by this invention has the following beneficial effects:

[0058] This invention provides a bridge structure deformation testing system based on microwave sensing. During operation, the system can generate directional microwave signals and accurately transmit them to the target test section of the bridge. After capturing the reflected signals, the system filters, amplifies, and demodulates the signals to improve signal quality and effectively filter out environmental interference. Multi-dimensional feature parameters are extracted from the processed signals. A deformation calculation model is constructed by combining the bridge cross-sectional dimensions, material elastic modulus, and other basic information. By introducing material nonlinearity and geometric nonlinearity correction terms, the feature parameters are accurately converted into the strain and deflection values ​​of the bridge.

[0059] Simultaneously, calibration instructions are generated based on a preset standard deformation database to dynamically adjust signal parameters and calculation model coefficients to optimize calculation results. Then, by comparing strain values, deflection values, and preset safety thresholds, and combining the deformation rate, a comprehensive risk index is calculated. Based on the risk level, the appropriate transmission frequency band, bandwidth, and period are flexibly selected to achieve efficient and accurate feedback of test data and risk assessment results. This not only adapts to different load conditions and environmental conditions, ensuring the accuracy, stability, and timeliness of bridge deformation testing, but also identifies deformation risks in a timely manner, providing support for bridge structural safety monitoring and maintenance. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0061] Figure 1 This is a schematic diagram of a bridge structure deformation testing system based on microwave sensing.

[0062] Figure 2 This is a schematic diagram of the test section location in application scenario one of the present invention;

[0063] Figure 3 This is a diagram showing the arrangement of the vibration pickup in application scenario two of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0065] The present invention will be further described below with reference to embodiments.

[0066] Example:

[0067] The bridge structure deformation testing system based on microwave sensing in this embodiment, such as... Figure 1 As shown, it includes:

[0068] The transmitting module is used to generate microwave signals and transmit them directionally to a predetermined target test section on the bridge;

[0069] The transmitting module includes a microwave signal generator, a reconfigurable beam transmitting component, and a power adjustment unit;

[0070] The microwave signal generator is used to generate frequency-adjustable continuous wave microwave signals, with a frequency adjustment range of 10GHz-30GHz and a frequency resolution of ≤100Hz.

[0071] The reconfigurable beam transmitting assembly consists of a radiating element array, a phase shifter network, and a beam control chip. The radiating element array contains 16 microstrip patch elements arranged in a regular hexagonal pattern. Each microstrip patch element controls its phase shift through an independent phase shifter. The beam control chip calculates the control voltage of each phase shifter based on preset target test section coordinate data and the following formula:

[0072] , This represents the control voltage of the i-th phase shifter. This represents the full-scale voltage. This represents the target phase offset of the i-th radiating element. , Let be the distance between the i-th radiating element and the array center. For the azimuth and elevation angles of the beam, The wavelength of the microwave signal;

[0073] The above formula focuses on the physical layout of the radiating element array and the beam pointing requirements. By combining spatial parameters such as the distance between the i-th radiating element and the array center, the beam azimuth angle, and the elevation angle with the microwave signal wavelength, it converts these parameters into target phase offset. Then, using the full-scale voltage as a reference, it establishes a linear mapping relationship between the phase and the control voltage, ensuring that each microstrip patch unit can accurately adjust its phase to form a directional beam. Breaking through the traditional fixed beam design, it achieves precise signal coverage of any preset test section of the bridge through 16 independently controlled phase units distributed in a regular hexagonal pattern and dynamic voltage calculation. This solves the problem of insufficient signal transmission directivity under complex structures and improves the targeting of the test target.

[0074] The power conditioning unit incorporates an environmental adaptive correction factor to adjust the final output power transmitted by the reconfigurable beam transmitting assembly to the target test cross section.

[0075] ;

[0076] In the formula: This refers to the final output power; Reference power; Used as the reference distance; This refers to the actual distance between the launch module and the target test section; Environmental degradation coefficient; This is a temperature correction factor; This is the difference between the real-time temperature and the reference temperature. This is the humidity correction factor; This represents the difference between the real-time humidity and the reference humidity.

[0077] Among them, the environmental attenuation coefficient ∈[0.8,1.0], and subject to the condition that the higher the density of dust, water vapor condensate, and physical obstacles in the microwave signal transmission path, and the longer the transmission distance, the better. The smaller the value, the better the temperature correction factor. The initial setting is -0.002 / ℃, used to quantify the impact of temperature deviation from the baseline value; humidity correction factor. ∈-0.001 / %RH, used to quantify the impact of humidity deviation from the baseline value, where the temperature baseline value is 25℃ and the humidity baseline value is 50%RH;

[0078] The above formula is based on the reference power and reference distance, and introduces the inverse square relationship of the actual transmission distance to compensate for signal attenuation. At the same time, it innovatively incorporates environmental attenuation coefficient, temperature correction coefficient and humidity correction coefficient to quantify the interference of obstacles such as dust and water vapor, as well as the impact of temperature and humidity deviation from the reference value on signal power. 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, and ensure the power stability of microwave signal when it reaches the test section under different operating conditions, providing a reliable signal foundation 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 component 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 launch module as the origin. The actual coordinate values ​​of the four vertices of the target test section in this coordinate system are obtained. The average value of the coordinates of the four vertices is calculated as the center coordinate of the target test section after calibration. Then, the control voltage of each phase shifter is calculated based on the calibrated coordinates.

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

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

[0083] The low-noise amplifier limits the noise figure fluctuation to no more than 0.3dB within the operating temperature range of -40℃ to 85℃, and the adjustable gain range is 20dB-60dB;

[0084] The center frequency of the bandpass filter is the same as the frequency of the transmitted signal, and the 3dB bandwidth is ≤100kHz, so as to filter out interference signals outside the same frequency band in the environment;

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

[0086] ;

[0087] In the formula: , This is the baseband signal after interference removal; The receiving module outputs two baseband signals through an orthogonal demodulation architecture; This is the interference suppression coefficient; For reference channel output signal; The phase difference between the transmit and receive channels;

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

[0089] The above formula is based on the original baseband signal output by orthogonal demodulation. By introducing a reference channel that is directly coupled to the transmitted signal, the correlation between the original signal and the reference signal is established using the interference suppression coefficient. At the same time, the signal phase is calibrated by combining the phase difference between the transmitting and receiving channels, thereby filtering out co-channel interference in the environment. It dynamically adjusts the interference suppression coefficient through the Pearson correlation coefficient. When the interference correlation between the reference channel and the main receiving channel is high, the coefficient is increased to enhance the suppression effect, and vice versa to avoid signal distortion. This solves the problem that traditional fixed filtering is difficult to adapt to dynamic interference scenarios and significantly improves the signal-to-noise ratio of the baseband signal.

[0090] The extraction module is used to acquire the microwave signal output by the receiving module, 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 calculation module.

[0091] Extracting operations from the extraction module follows these rules:

[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; Let represent the instantaneous rate of change of the i-th modal component, that is, to represent the change of . The process of performing time-domain differentiation; The initial synthesized amplitude is 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—instantaneous fluctuation, short-term trend, and long-term drift—through variational mode decomposition. Subsequently, weight coefficients are assigned according to the signal-to-noise ratio (SNR) of each modal component. Finally, the amplitude change rate is obtained by summing the products of the instantaneous change rate of each component and its weight, combined with the initial synthesized amplitude. Its innovation lies in distinguishing amplitude change components with different characteristics through mode decomposition and dynamically assigning weights according to the SNR, avoiding interference from noise or trend components in single-signal analysis, achieving refined extraction of the amplitude change rate, and providing more comprehensive feature support for deformation calculations.

[0098] Among them, gradient correction coefficient The values ​​are determined as follows: when the microwave echo signal-to-noise ratio is not less than 40dB, the value is 0.15-0.2; otherwise, the value is 0.05-0.1. The weight coefficients of the modal components are determined as follows: the sum of the weight coefficients of all modal classifications is 1, and the weight coefficients of each modal component are positive. The higher the signal-to-noise ratio of the modal component, the larger the weight coefficient of that modal component, and vice versa.

[0099] In the phase offset extraction process of the extraction module, the wavelet basis function of the wavelet transform is selected as db4 wavelet, the number of decomposition levels is set to 5, and the EMD decomposition of Hilbert-Huang transform terminates when the energy difference of the intrinsic mode functions obtained from two adjacent decompositions is less than 0.01%.

[0100] During the extraction of frequency changes, the sliding window length of the sliding Fourier transform is set to 512 sampling points, and the time interval is... The value is 0.001 seconds;

[0101] During the amplitude change rate extraction process, the penalty factor for variational mode decomposition was set to 2000, and the noise tolerance was set to 0.001.

[0102] The calculation module is used to store the length, width, height of the target test section, as well as the elastic modulus and material information of concrete. It synchronously receives the feature parameters output by the extraction module to create a deformation calculation model. The deformation calculation model is then used to convert the feature parameters into strain and deflection values ​​of the bridge test section and output them.

[0103] In the deformation calculation model of the computation module, a material nonlinearity correction term is introduced during the process of converting characteristic parameters into strain and deflection values ​​of the bridge test section.

[0104] Strain calculation sub-model: , The actual strain value of the target test section of the bridge; The wavelength of the microwave signal output by the transmitting module; The phase offset of the microwave signal obtained by the extraction module; The length of the target test section of the bridge; The elastic modulus of bridge concrete; This is a material nonlinearity correction factor; The phase threshold corresponding to the yielding of concrete material; The hardening index of concrete materials;

[0105] The above formula uses microwave signal wavelength and phase offset as core parameters, and establishes basic strain relationship in combination with test section length. At the same time, it introduces concrete elastic modulus, material nonlinearity correction coefficient, yield phase threshold and hardening index to quantify the nonlinear characteristics of concrete material in the stress process. The material nonlinearity correction coefficient is dynamically selected according to the load size and concrete strength grade. It breaks through the traditional linear strain calculation model and can accurately reflect the strain change law of concrete material from the elastic stage to the plastic stage, so that the calculation results are more consistent with the actual stress and deformation state of the bridge.

[0106] Deflection calculation sub-model: , The actual deflection value of the target test section of the bridge; The speed of light in a vacuum; The frequency change of the microwave signal obtained by the extraction module; The initial frequency for 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;

[0107] The above formula establishes the relationship between distance change and frequency based on the speed of light, initial microwave frequency, and frequency change. It also incorporates the amplitude change rate, test section height, concrete density, and geometric nonlinearity correction coefficient. Combined with the initial deflection value, the actual deflection is obtained. The geometric nonlinearity correction coefficient is dynamically determined according to the bridge span. It innovatively combines frequency change and amplitude change and considers the influence of structural geometry on deflection. It breaks the traditional deflection calculation mode that relies on only a single parameter. It can accurately capture the geometric nonlinear deformation of long-span bridges under stress and improve the applicability and accuracy of deflection calculation.

[0108] 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;

[0109] The correction module receives the calculation results output by the calculation module, generates calibration instructions based on the preset standard deformation database, applies the calibration instructions to adjust the microwave signal of the transmitting module, the processing parameters of the receiving module and the model coefficients of the deformation calculation module respectively, and jumps to the calculation module to run again, outputting the strain value and deflection value of the bridge test section.

[0110] The preset standard deformation database in the correction module includes standard strain values ​​for bridges under static, dynamic, 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;

[0111] 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.

[0112] Control commands for the transmitting module: Adjust microwave signal frequency deviation ;

[0113] Control commands for the receiving module: Adjust the bandwidth of the bandpass filter. ;

[0114] Control instructions for the computation module: Correct the coefficients of the deformation calculation model. The corrected strain value is The deflection value is ;

[0115] 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.

[0116] In the above setup, the frequency deviation adjustment formula uses the initial microwave frequency as a reference and dynamically corrects the frequency based on the strain and deflection deviation rate to ensure that the transmitted signal matches the test requirements. The bandwidth adjustment formula is based on the initial bandpass filter bandwidth and optimizes the filtering range by combining the deviation rate to improve the interference filtering effect. The corrected strain and deflection formulas reduce the error between theoretical calculation and actual deformation by introducing deviation correction terms into the original calculation results. Its innovation lies in using a standard deformation database as a reference and triggering multi-module collaborative calibration through the deviation rate, rather than adjusting a single module, to form a closed loop of "calculation-comparison-correction-recalculation". This solves the long-term drift problem caused by fixed parameters in traditional systems and continuously ensures the accuracy of deformation calculation.

[0117] The classification criteria for static load, dynamic load, and temperature load conditions in the preset standard deformation database of the correction module are as follows:

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

[0119] The transmission module is used to receive the strain and deflection values ​​of the bridge test section when the correction module triggers the calculation module to run again. Based on the comparison of the strain and deflection values ​​with the preset safety thresholds, it determines whether there is a risk of deformation in the bridge structure, and packages the determination result with the strain and deflection values ​​and transmits it to the preset feedback target.

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

[0121] Calculate the comprehensive risk index , The strain limit threshold The deflection limit threshold. For deformation rate, This represents the deformation rate limit threshold.

[0122] The preset safety threshold is initially set to [0, 0.5). Then, 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.

[0123] In high-risk situations, millimeter-wave frequency band transmission is used. The operating frequency of the millimeter-wave frequency band is 28 GHz, and the transmission bandwidth is dynamically adjusted according to the comprehensive risk index. ;

[0124] For medium-risk situations, the 3.5GHz frequency band is used for transmission, with a transmission interval of [missing information]. The unit is seconds;

[0125] In low-risk and no-risk scenarios, a low-power wide-area transmission architecture is adopted, with the carrier frequency ranging from 433MHz to 915MHz, the spreading factor from 12 to 16, and the receiver sensitivity ≤ -148dBm. The transmission period shortens as R increases. The unit is seconds. Used to indicate the transmission cycle in low-risk and risk-free scenarios;

[0126] Deformation rate in transmission module The calculation method is as follows:

[0127] Three sets of strain and deflection values ​​received continuously by the transmission module are selected. The time interval between two adjacent sets of data is calculated. The average of the ratios of the strain value change to the corresponding time interval and the deflection value change to the corresponding time interval is taken as the deformation rate. ;

[0128] When the transmission module determines the deformation risk of the bridge structure based on the comprehensive risk index, if the results of three consecutive determinations are inconsistent, the determination result with the most occurrences shall be selected as the final risk determination result. If the three determination results are different, the intermediate risk level shall be used as the final risk determination result.

[0129] The receiving module interacts with the extraction module via a wireless network, the extraction module interacts with the calculation module via a wireless network, the calculation module interacts with the correction module via a wireless network, and the correction module interacts with the transmission module via a wireless network.

[0130] In this embodiment, the transmitting module first generates a microwave signal with an adjustable frequency of 10GHz-30GHz, which is then transmitted directionally according to the target test section coordinates via a reconfigurable beam transmitting component. Simultaneously, the power adjustment unit adjusts the output power based on environmental factors. The receiving module amplifies the signal using a low-noise amplifier, filters it with a bandpass filter at the same frequency as the transmitted signal, decomposes the signal using an orthogonal demodulation architecture, and performs 16-bit ADC sampling and interference suppression processing. The extraction module uses a combination of wavelet transform and Hilbert-Huang (HHT) transform to extract three types of feature parameters from the received signal: phase shift, frequency change, and amplitude change rate. The calculation... The module calls the pre-stored bridge cross-section dimensions and material information, and converts the characteristic parameters into strain and deflection values ​​through a deformation calculation model containing material and geometric nonlinear correction terms. The correction module compares the calculation results with the preset standard deformation database data. If the deviation rate exceeds 5%, a calibration command is generated to adjust the frequency of the transmitting module, the filter bandwidth of the receiving module, and the model coefficients of the calculation module, and then triggers the calculation module to recalculate. The transmission module receives the corrected strain and deflection values, calculates the comprehensive risk index to determine the risk level, and uses the corresponding frequency band and transmission parameters according to the level. The determination results and data are packaged and fed back to the preset target.

[0131] In the above embodiments, the system can accurately capture bridge reflection signals during bridge deformation testing, process and extract key parameters, and calculate strain and deflection values ​​by combining them with the bridge's own information. It can also calibrate and optimize the results based on a standard database to ensure data accuracy. At the same time, it can judge the bridge deformation risk, dynamically adjust the transmission method and parameters according to the risk level, and provide timely feedback on the results. This effectively ensures bridge safety monitoring, improves monitoring efficiency and reliability, provides accurate data support for bridge maintenance, and reduces safety hazards.

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

[0133] Regarding calibration termination conditions: Set a maximum calibration count threshold (e.g., 3 times). If the deviation rate is still >5% after the consecutive calibration count reaches the threshold, a fault alarm will be triggered and the current deviation data will be recorded. At the same time, the system will automatically switch to the backup test mode (e.g., enable redundant sensor data) to avoid infinite loops. If the deviation rate is ≤5% within the threshold count, the calibration will terminate and the current calibration parameters will be saved.

[0134] Regarding the time interval for calculating the deformation rate: During system operation, the sampling time interval for three consecutive sets of strain and deflection values ​​is specified as a fixed value (e.g., 1 second), and this interval is not affected by the transmission cycle. The uniformity of data acquisition time is ensured through an independent timing module. The deformation rate calculation formula is uniformly calculated as the difference between the previous set of data and the next set of data, divided by the fixed time interval. The average of the three calculation results is taken as the final deformation rate.

[0135] Regarding the method for obtaining key parameters:

[0136] The phase threshold corresponding to the yield of concrete material was obtained by uniaxial compression test of concrete specimens in the same batch. When the stress-strain curve showed an obvious yield plateau, the corresponding microwave phase shift was recorded as the threshold.

[0137] The hardening index was determined by referring to the material parameters of concrete of the same strength grade in the "Code for Design of Concrete Structures" and combining the microwave test data of more than 10 sets of specimens.

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

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

[0140] The radiating element array uses a 4×4 microstrip patch antenna array, with each element connected to the phase shifter network via an SMA interface;

[0141] The phase shifter is a 6-bit digital phase shifter of model HMC547LP4E. The beam control chip (optional model STM32F407) outputs control voltage (0-5V) to the phase shifter through the SPI interface.

[0142] In the orthogonal demodulation architecture:

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

[0144] The following example illustrates an application instance of the system described in the above embodiments:

[0145] I. Project Background

[0146] This application example focuses on the S43 Airport Expressway, specifically the section from K1+388.357 to K1+478.357 of the Shibugeng Interchange A ramp bridge (3×30m cast-in-place prestressed concrete continuous box girder). The bridge is 90.0m long, with a superstructure of cast-in-place prestressed concrete continuous box girder. The girder height is 1.8m, the cantilever length is 1.8m, the bridge deck cross slope is 2%, the longitudinal slope is -0.4%, the design load is Highway-I, and the concrete used is C50 with an elastic modulus of 3.45×10⁻⁶. 4 MPa, unit weight 26kN / m³. To accurately grasp the structural deformation of the bridge under static and dynamic load conditions and verify whether its bearing capacity meets the design requirements, a bridge structural deformation testing system based on microwave sensing was introduced for deformation monitoring.

[0147] II. System Deployment and Parameter Setting

[0148] (I) Deployment and parameter configuration of the launch module

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

[0150] The microwave signal generator in the transmitting module generates a frequency-adjustable continuous wave microwave signal. Considering the electromagnetic interference conditions of the bridge testing environment, the initial frequency is set to 20GHz (within the 10GHz-30GHz adjustment range, a frequency resolution of 80Hz, meeting the ≤100Hz requirement). The reconfigurable beam transmitting component contains 16 hexagonally distributed microstrip patch units. Based on the center coordinates of the target test section (taking section AA as an example, coordinates are X=15m, Y=0m, Z=1.8m), the target phase offset of each radiating unit is calculated. Then, combined with the full-scale voltage of 10V, the phase shifter control voltage is calculated using the phase shifter control voltage calculation formula, resulting in a phase shifter control voltage between 1.2V and 3.5V, achieving directional transmission of the microwave signal to the test section.

[0151] Regarding the power adjustment unit, the reference power P0 = 15dBm, the reference distance d0 = 20m, and the actual distance between the transmitting module and the AA cross-section d = 18m were set. The actual measured temperature on-site was 28℃ (difference from the reference temperature of 25℃ ΔT = 3℃), and the humidity was 55%RH (difference from the reference humidity of 50%RH ΔH = 5%RH). The environmental attenuation coefficient n was set to 0.92 (within the 0.8-1.0 range) based on the on-site dust and moisture conditions. The temperature correction coefficient k1 = -0.002 / ℃ and the humidity correction coefficient kh = -0.001 / %RH were used. Substituting these values ​​into the power calculation formula, the final output power Pou = 14.8dBm was calculated, ensuring stable microwave signal transmission to the target test cross-section.

[0152] (II) Deployment and Parameter Configuration of Receiving Module

[0153] The receiving module is mounted on the same side as the transmitting module, maintaining axis alignment, and is used to capture microwave signals reflected from each test cross-section. The low-noise amplifier's operating temperature is set between -40℃ and 85℃. Considering the ambient temperature of 28℃, the gain was adjusted to 40dB (within the adjustable range of 20dB-60dB). Testing showed its noise figure fluctuation was 0.2dB, meeting the requirement of ≤0.3dB. The bandpass filter's center frequency is consistent with the transmitted signal frequency of 20GHz, with a 3dB bandwidth of 80kHz (≤100kHz), effectively filtering out interference signals from outside the same frequency band in the environment.

[0154] The signal demodulation unit adopts an orthogonal demodulation architecture. A phase shifter splits the local oscillation signal into two signals with a 90° phase difference. These signals are then input to two mixers and mixed with the received signal. The output in-phase and crossover baseband signals are sampled by a 16-bit ADC for interference suppression. Interference signals are captured through a reference channel (directly coupled to the original signal from the transmitting module). The Pearson correlation coefficient between the reference channel signal and the interference signal from the main receiving channel is calculated to be 85% (≥80%). An interference suppression coefficient α = 0.7 is set and substituted into the interference suppression formula to process the baseband signal, reducing the impact of environmental interference on signal quality.

[0155] (III) Input of parameters for the calculation module

[0156] The structural parameters of each test section were pre-entered into the calculation module: Section AA: length 18m (corresponding to the transverse width of the bridge, conforming to the actual range of bridge deck width 0.5m + 14.37~11.07m + 0.5m), height 1.8m (beam height); Section BB: length 18m, height 1.8m; Section CC: length 18m, height 1.8m; Simultaneously, the elastic modulus of C50 concrete was entered as 3.45 × 10⁻⁶. 4 Material information such as MPa and density of 2600 kg / m³ provides basic data for the deformation calculation model.

[0157] III. Data Acquisition and Processing

[0158] (I) Feature Parameter Extraction

[0159] Phase Shift Extraction: After the receiving module outputs the microwave signal, the extraction module uses a combination of wavelet transform (using db4 wavelet as the wavelet basis function, with 5 decomposition levels) and Hilbert-Huang transform to perform EMD decomposition on the I / Q signal, obtaining 8 intrinsic mode functions (IMFs). The top 3 IMF components by energy percentage are selected to reconstruct the signal. Calculations show that the amplitude of the reconstructed orthogonal baseband signal at the AA section is 2.5V, the amplitude of the in-phase baseband signal is 2.3V, and the initial phase of the transmitted signal is 0°. The final phase shift is calculated to be 0.02 rad at the AA section, -0.015 rad at the BB section, and 0.018 rad at the CC section.

[0160] Frequency change extraction: Based on the reconstructed signal, the instantaneous frequency is calculated with a time interval Δt = 0.001 seconds. The frequency change gradient is calculated using a sliding Fourier transform (sliding window length of 512 sampling points). The measured instantaneous frequency of the AA section at time t+Δt is 20.0001 GHz, the instantaneous frequency at time t-Δt is 19.9999 GHz, the instantaneous frequency at the current time is 20 GHz, the initial transmission frequency is 20 GHz, the microwave echo signal-to-noise ratio is 45 dB (≥40 dB), and the gradient correction coefficient is 0.18. Substituting these values ​​into the frequency change calculation formula, the frequency change of the AA section is 0.00012 GHz, the frequency change of the BB section is -0.00009 GHz, and the frequency change of the CC section is 0.0001 GHz.

[0161] Amplitude Change Rate Extraction: The synthesized amplitude A(t) of the original baseband signal output by the receiving module is calculated. Variational mode decomposition (penalty factor 2000, noise tolerance 0.001) is performed on A(t), decomposing it into three modal components (instantaneous fluctuation, short-term trend, and long-term drift). The weighting coefficients of each modal component are determined based on the signal-to-noise ratio, and are 0.3, 0.4, and 0.3 respectively (summing to 1). The instantaneous change rate of each modal component is calculated. With an initial synthesized amplitude of 2.4V, substituting into the amplitude change rate calculation formula, the amplitude change rate of the AA cross section is found to be 0.002. The amplitude change rate of the BB section is -0.0015. The rate of change of the CC cross section is 0.0018s. .

[0162] (II) Calculation of Deformation

[0163] Strain calculation: Combining the extracted feature parameters with the structural and material parameters stored in the calculation module, section AA bears a large load, the concrete strength grade is C50, the material nonlinearity correction coefficient is taken as 0.06 (in the range of 0.02-0.08), the phase threshold corresponding to the yield of concrete material is 0.05 rad, and the hardening index is 0.8. Substituting into the strain calculation sub-model, the microwave wavelength λ is based on the initial frequency of 20 GHz and the speed of light 3 × 10⁻⁶. 8 The calculated m / s value is 0.015m. The final calculated strain value for section AA is 85, for section BB is -65, and for section CC is 78.

[0164] Deflection calculation: The bridge span of section AA is 30m, the geometric nonlinearity correction factor is 0.25 (in the range of 0.15-0.3), and the initial deflection value is 0mm. Substitute into the deflection calculation sub-model.

[0165] IV. Data Correction and Risk Assessment

[0166] (a) Data Correction

[0167] The correction module calls a preset standard deformation database (containing standard strain, deflection, and corresponding standard characteristic parameters of a 3×30m continuous beam of C50 concrete under static, dynamic, and temperature load conditions. This database is based on bridge specimens of the same structural type and material parameters as the test bridge, obtained through more than 100 repeated tests, and meets the technical requirements). It then calculates the deviation rate between the output results of the calculation module and the standard values. Specifically, the strain deviation rate for section AA is 3.2% (≤5%), the deflection deviation rate is 2.8% (≤5%), the strain deviation rate for section BB is 4.5% (≤5%), and the strain deviation rate for section CC is 3.8% (≤5%) and the deflection deviation rate is 3.1% (≤5%). All these meet the accuracy requirements, and no calibration command needs to be generated; the current calculation results are used directly.

[0168] (II) Deformation Risk Assessment

[0169] The transmission module calls the preset safety threshold [0, 0.5), and combines the strain limit threshold, deflection limit threshold, and deformation rate limit threshold to select three consecutive sets of strain and deflection data. The time interval between two adjacent sets of data is 10s. The strain changes are 5 and 4, and the deflection changes are 0.3mm and 0.2mm, respectively. The deformation rate is found to be 0.45mm / s.

[0170] Substituting into the comprehensive risk index calculation formula, the calculated cross-section R = 0.42 for AA, R = 0.38 for BB, and R = 0.40 for CC, all less than 0.5, thus indicating no risk.

[0171] The transmission module adopts a low-power wide-area transmission architecture, with a carrier frequency set at 868MHz (within the range of 433MHz-915MHz), a spreading factor of 14 (within the range of 12-16), and a receiving sensitivity of -150dBm (≤-148dBm). Based on the comprehensive risk index R=0.40, and substituting it into the transmission period calculation formula, the transmission period is found to be 30s. The strain value, deflection value, and risk-free determination result are packaged and transmitted to the preset bridge operation and maintenance management platform.

[0172] V. Application Effect Verification

[0173] The test results of the microwave sensing system were compared with those of traditional displacement gauges and strain gauges. The measured strain value of section AA deviated by 2.4% and the measured deflection value by 1.9% compared with the traditional test value. The measured strain value of section CC deviated by 2.6% and the measured deflection value by 2.1% compared with the traditional test value. All deviations were within 5%, which verified the accuracy of the system test data.

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

[0175] The observation section and measurement contents are shown in the table below:

[0176] Operating conditions Observation section position Measurement content Operating Condition 1 Maximum positive bending moment in the first span (section AA) Box girder concrete strain, deflection, and support settlement Operating Condition 2 Negative bending moment at the top of pier #1 (section BB) Box girder concrete strain Operating Condition 3 Maximum positive bending moment at mid-span of the second span (CC section) Box girder concrete strain, deflection, and support settlement

[0177] See Figure 3 As shown, the bridge modal testing acquisition module was used to determine the dynamic parameters of the bridge under dynamic loads, including mode shape, frequency, and damping ratio. Vibration pickups were arranged longitudinally along the bridge at positions at 1 / 4L, 1 / 2L, and 3 / 4L of each span in the test section. The pickups were vertically perpendicular to the bridge deck to measure the bridge's vertical vibration response, and laterally positioned approximately 30cm from the crash barrier. After determining the measurement point locations, the pickups were leveled with modeling clay and coupled to the bridge deck. The measurement point arrangement is as follows. Figure 3 As shown.

[0178] In summary, the system in the above embodiments 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, effectively filtering out environmental interference. Multi-dimensional feature parameters are extracted from the processed signals, and a deformation calculation model is constructed by combining the bridge cross-sectional dimensions, material elastic modulus, and other basic information. By introducing material nonlinearity and geometric nonlinearity correction terms, the feature parameters are accurately converted into the strain and deflection values ​​of the bridge. At the same time, calibration instructions are generated based on a preset standard deformation database to dynamically adjust the signal parameters and calculation model coefficients to optimize the calculation results. Then, by comparing the strain and deflection values ​​with preset safety thresholds and combining the deformation rate, a comprehensive risk index is calculated. The appropriate transmission frequency band, bandwidth, and period are flexibly selected according to the risk level to achieve efficient and accurate feedback of test data and risk judgment results. It can adapt to different load conditions and environmental conditions, ensuring the accuracy, stability, and timeliness of bridge deformation testing, and can also identify deformation risks in a timely manner, providing support for bridge structural safety monitoring and maintenance.

[0179] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bridge structure deformation testing system based on microwave sensing, characterized in that, include: The transmitting module is used to generate microwave signals and transmit them directionally to a predetermined target test section on the bridge; The receiving module is used to capture the microwave signal reflected from the target test section on the bridge, and output it after filtering and amplification matching the frequency of the transmitted signal; The extraction module is used to acquire the microwave signal output by the receiving module, 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 calculation module. The calculation module is used to store the length, width, height of the target test section, as well as the elastic modulus and material information of concrete. It synchronously receives the feature parameters output by the extraction module to create a deformation calculation model. The deformation calculation model is then used to convert the feature parameters into strain and deflection values ​​of the bridge test section and output them. The correction module receives the calculation results output by the calculation module, generates calibration instructions based on the preset standard deformation database, applies the calibration instructions to adjust the microwave signal of the transmitting module, the processing parameters of the receiving module and the model coefficients of the deformation calculation module respectively, and jumps to the calculation module to run again, outputting the strain value and deflection value of the bridge test section. The transmission module is used to receive the strain and deflection values ​​of the bridge test section when the correction module triggers the calculation module to run again. Based on the comparison of the strain and deflection values ​​with the preset safety thresholds, it determines whether there is a risk of deformation in the bridge structure, and packages the determination result with the strain and deflection values ​​and transmits it to the preset feedback target.

2. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The transmitting module includes a microwave signal generator, a reconfigurable beam transmitting component, and a power adjustment unit; The microwave signal generator is used to generate frequency-adjustable continuous wave microwave signals, with a frequency adjustment range of 10GHz-30GHz and a frequency resolution of ≤100Hz. The reconfigurable beam transmitting component consists of a radiating element array, a phase shifter network, and a beam control chip. The radiating element array contains 16 microstrip patch units arranged in a regular hexagonal pattern. Each microstrip patch unit controls the phase shift through an independent phase shifter. The beam control chip calculates the control voltage of each phase shifter based on preset target test section coordinate data and the following formula: , This represents the control voltage of the i-th phase shifter. This represents the full-scale voltage. This represents the target phase offset of the i-th radiating element. , Let be the distance between the i-th radiating element and the array center. For the azimuth and elevation angles of the beam, The wavelength of the microwave signal; The power conditioning unit incorporates an environmental adaptive correction factor to adjust the final output power transmitted by the reconfigurable beam transmitting assembly to the target test section. ； In the formula: This refers to the final output power; Reference power; Used as the reference distance; This refers to the actual distance between the launch module and the target test section; Environmental degradation coefficient; This is a temperature correction factor; This is the difference between the real-time temperature and the reference temperature. This is the humidity correction factor; This represents the difference between the real-time humidity and the reference humidity. Among them, the environmental attenuation coefficient ∈[0.8,1.0], and subject to the condition that the higher the density of dust, water vapor condensate, and physical obstacles in the microwave signal transmission path, and the longer the transmission distance, the better. The smaller the value, the better the temperature correction factor. The initial setting is -0.002 / ℃, used to quantify the impact of temperature deviation from the baseline value; humidity correction factor. ∈-0.001 / %RH, used to quantify the impact of humidity deviation from the baseline value, where the temperature baseline value is 25℃ and the humidity baseline value is 50%RH.

3. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The receiving module includes a low-noise amplifier, a bandpass filter, and a signal demodulation unit. The signal demodulation unit is an orthogonal demodulation architecture used to decompose the received microwave signal into in-phase and quadrature baseband signals. The low-noise amplifier is limited to a noise figure fluctuation of no more than 0.3dB within an operating temperature range of -40℃ to 85℃, and the gain is adjustable from 20dB to 60dB. The center frequency of the bandpass filter is the same as the frequency of the transmitted signal, and the 3dB bandwidth is ≤100kHz, so as to filter out interference signals outside the same frequency band in the environment. The signal demodulation unit includes Phase shifter and two mixers, of which The phase shifter divides the local oscillation signal into phase difference signals. The two signals are input to two mixers respectively to mix with the received signal. The output phase and crossover baseband signals are sampled by a 16-bit ADC and then subjected to interference suppression. ； In the formula: , This is the baseband signal after interference removal; The receiving module outputs two baseband signals through an orthogonal demodulation architecture; This is the interference suppression coefficient; For reference channel output signal; The phase difference between the transmit and receive channels; The reference channel is the channel directly coupled to the original signal of the transmitting module, and the interference suppression coefficient is... ∈[0.1, 0.9], when the Pearson correlation coefficient between the interference signal captured by the reference channel and the interference signal of the main receiving channel is not less than 80%, The larger the value, the lower the correlation coefficient when the Pearson correlation coefficient is less than 50%. The smaller the value.

4. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The extraction module extracts operations that conform to: 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; 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 ; 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. 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; Let represent the instantaneous rate of change of the i-th modal component, that is, to represent the change of . The process of performing time-domain differentiation; The initial synthesized amplitude is the synthesized amplitude value of the first sampling point after the system starts. Among them, gradient correction coefficient The values ​​are determined as follows: when the microwave echo signal-to-noise ratio is not less than 40dB, the value is 0.15-0.2; otherwise, the value is 0.05-0.

1. The weight coefficients of the modal components are determined as follows: the sum of the weight coefficients of all modal classifications is 1, and the weight coefficients of each modal component are positive numbers. The higher the signal-to-noise ratio of a modal component, the larger the weight coefficient of that modal component, and vice versa.

5. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, In the deformation calculation model of the aforementioned calculation module, a material nonlinearity correction term is introduced during the process of converting characteristic parameters into strain and deflection values ​​of the bridge test section. Strain calculation sub-model: , The actual strain value of the target test section of the bridge; The wavelength of the microwave signal output by the transmitting module; The phase offset of the microwave signal obtained by the extraction module; The length of the target test section of the bridge; The elastic modulus of bridge concrete; This is a material nonlinearity correction factor; This represents the phase threshold corresponding to the yielding of concrete. The hardening index of concrete materials; Deflection calculation sub-model: , The actual deflection value of the target test section of the bridge; The speed of light in a vacuum; The frequency change of the microwave signal obtained by the extraction module; The initial frequency for 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; 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.

6. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The preset standard deformation database in the correction module includes standard strain values ​​of bridges 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; 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 commands for the transmitting module: Adjust microwave signal frequency deviation ; Control commands for the receiving module: Adjust the bandwidth of the bandpass filter. ; Control instructions for the computation module: Correct the coefficients of the deformation calculation model. The corrected strain value is The deflection value is ; 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.

7. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The deformation risk determination logic in the transmission module is as follows: Calculate the comprehensive risk index , The strain limit threshold The deflection limit threshold. For deformation rate, This represents the deformation rate limit threshold. The preset safety threshold is initially set to [0, 0.5). Then, 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. In high-risk situations, millimeter-wave frequency band transmission is used. The operating frequency of the millimeter-wave frequency band is 28 GHz, and the transmission bandwidth is dynamically adjusted according to the comprehensive risk index. ; For medium-risk situations, the 3.5GHz frequency band is used for transmission, with a transmission interval of [missing information]. The unit is seconds; In low-risk and no-risk scenarios, a low-power wide-area transmission architecture is adopted, with the carrier frequency ranging from 433MHz to 915MHz, the spreading factor from 12 to 16, and the receiver sensitivity ≤ -148dBm. The transmission period shortens as R increases. The unit is seconds. Used to indicate the transmission cycle in low-risk and risk-free scenarios.

8. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, Before calculating the control voltage of each phase shifter, 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. The calibration process is as follows: A three-dimensional rectangular coordinate system is established with the installation position of the launch module as the origin. The actual coordinate values ​​of the four vertices of the target test section in this coordinate system are obtained. The average value of the coordinates of the four vertices is calculated as the center coordinate of the target test section after calibration. Then, the control voltage of each phase shifter is calculated based on the calibrated coordinates. In the phase offset extraction process of the extraction module, the wavelet basis function of the wavelet transform is selected as db4 wavelet, the number of decomposition layers is set to 5, and the EMD decomposition of Hilbert-Huang transform terminates when the energy difference of the intrinsic mode functions obtained from two adjacent decompositions is less than 0.01%. During the extraction of frequency changes, the sliding window length of the sliding Fourier transform is set to 512 sampling points, and the time interval is... The value is 0.001 seconds; During the amplitude change rate extraction process, the penalty factor for variational mode decomposition was set to 2000, and the noise tolerance was set to 0.

001.

9. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The classification criteria for static load, dynamic load, and temperature load conditions in the preset standard deformation database of the correction module are as follows: The static load condition refers to the condition where the bridge is subjected to a constant load and the load value does not exceed 50% of the design load. The dynamic load condition refers to the condition where the bridge is subjected to a periodically changing load and the load change frequency is between 0.1Hz and 5Hz. The temperature load condition refers to the condition where the ambient temperature of the bridge changes by more than 5℃ within 24 hours. The standard strain value, standard deflection value and corresponding standard characteristic parameters under each condition are obtained by more than 100 repeated tests on bridge specimens with the same structural type and material parameters as the tested bridge. Deformation rate in the transmission module The calculation method is as follows: Three sets of strain and deflection values ​​received continuously by the transmission module are selected. The time interval between two adjacent sets of data is calculated. The average of the ratios of the strain value change to the corresponding time interval and the deflection value change to the corresponding time interval is taken as the deformation rate. ; When the transmission module determines the deformation risk of the bridge structure based on the comprehensive risk index, if the results of three consecutive determinations are inconsistent, the determination result with the most occurrences shall be selected as the final risk determination result. If the three determination results are different, the intermediate risk level shall be used as the final risk determination result.

10. The bridge structure deformation testing system based on microwave sensing according to claim 1, characterized in that, The receiving module interacts with the extraction module via a wireless network, the extraction module interacts with the calculation module via a wireless network, the calculation module interacts with the correction module via a wireless network, and the correction module interacts with the transmission module via a wireless network.

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