Anti-vibration interference displacement measurement method and device based on millimeter wave radar structure

Abstract

The invention discloses an anti-vibration interference displacement measurement method and device based on a millimeter-wave radar structure. The method comprises the following steps: acquiring a radar echo signal of a measured structural body through a millimeter-wave radar configured with an anti-vibration interference structure; performing focusing processing on the echo signal to generate a two-dimensional single-view complex radar image and performing registration; selecting a fixed part of a measured structural body and a scattering unit with high echo intensity and stable phase from the registered image as a reference; carrying out anti-vibration interference correction on the interference phase based on the reference, and removing residual vibration interference phase components to obtain a target phase; performing phase unwrapping on the target phase and converting the target phase into vertical displacement data; and continuously collecting multiple groups of signals and repeating the operation to generate a vertical displacement sequence of the measured structural body so as to realize displacement measurement. According to the invention, the problem that the millimeter wave radar is interfered by vibration in displacement measurement is effectively solved, the measurement precision and stability are greatly improved, and the method is suitable for displacement monitoring scenes of bridges, buildings and other structural bodies.

Description

Technical Field

[0001] This invention relates to the field of structural displacement monitoring technology, specifically to a displacement measurement method and device based on millimeter-wave radar for structural vibration interference resistance. Background Technology

[0002] Displacement measurement is a core tool for structural health monitoring and equipment condition assessment, widely used in bridge maintenance, building safety, and precision equipment testing. Existing displacement measurement technologies have significant limitations in vibration environments, struggling to balance accuracy and interference resistance. Fiber optic displacement sensors and piezoelectric displacement gauges require direct mounting to the measured structure, resulting in high installation and maintenance costs and a lack of vibration-resistant design, making them susceptible to additional errors from environmental vibrations. Accelerometers require displacement calculation through quadratic integration, and sensor drift caused by vibration accumulates errors, failing to meet sub-millimeter accuracy requirements. While laser displacement gauges offer high accuracy, they lack dedicated vibration-resistant structures, making measurement distances prone to shift when affected by carrier vibrations, and requiring close-range deployment. Visual imaging measurements require marker points, and vibration can cause image blurring or marker point identification errors, resulting in poor interference resistance.

[0003] Traditional radar measurement techniques have shortcomings. Ground-based synthetic aperture radar (GB-SAR) relies on mechanical motion to construct the synthetic aperture, lacking anti-vibration design, and vibration will destroy the accuracy of aperture synthesis. When existing millimeter-wave radars are used for displacement measurement, they are mostly not equipped with anti-vibration interference structures. When the radar itself or the carrier is affected by vibration (such as being carried by UAVs or deployed on vehicles), the phase center shift will introduce millimeter-level phase errors, completely masking the sub-millimeter-level true displacement signal of the structure, leading to measurement failure.

[0004] Existing technologies for interference compensation in radar displacement measurement mostly rely on single software algorithms (such as inertial measurement unit-assisted correction) or structures, lacking a coordinated design of hardware vibration-resistant structures and software signal correction. Software compensation alone is insufficient to eliminate hardware-level phase deviations caused by vibration, and increases system complexity and cost.

[0005] Chinese patent (CN202410977460.0) discloses a two-dimensional vibration measurement method based on a single millimeter-wave radar, which achieves anti-interference only through signal-level optimization: first, it uses corner reflectors to enhance the line-of-sight / non-line-of-sight signal strength to resist signal attenuation interference; second, it removes static components through a circle fitting algorithm to reduce environmental static clutter interference; however, it lacks any hardware anti-vibration interference structure (such as shock-absorbing brackets or phase center stabilization mechanisms) and cannot suppress phase center shift caused by radar carrier or environmental vibration.

[0006] Chinese patent (CN202411073578.0) discloses a mobile millimeter-wave radar detection device that achieves anti-vibration interference through dynamic hardware adjustment: relying on a position / angle adjustment system composed of a slide and a rudder mechanism, the radar attitude is corrected in real time based on point cloud data feedback to resist the influence of vibration; however, it does not have a dedicated displacement measurement function. The core objective is to ensure the radar's detection accuracy of the target's position, velocity, and azimuth, rather than extracting the target's displacement signal.

[0007] In summary, there is an urgent need for a displacement measurement method that integrates a millimeter-wave radar-specific anti-vibration interference structure with an adaptive algorithm to solve the problems of low displacement measurement accuracy and weak anti-interference capability under vibration environment, and to achieve stable and high-precision monitoring of structural displacement. Summary of the Invention

[0008] To address the aforementioned technical problems, this application discloses a displacement measurement method and apparatus based on millimeter-wave radar structure vibration interference resistance; the displacement measurement method based on millimeter-wave radar structure vibration interference resistance specifically includes:

[0009] The radar echo signal reflected by the structure under test is collected by a millimeter-wave radar equipped with a vibration-resistant structure.

[0010] The radar echo signal is focused to generate a two-dimensional single-view complex radar image, and registration is performed to eliminate minor positional deviations.

[0011] In the registered two-dimensional single-view complex radar image, the scattering unit with high echo intensity and stable phase at the fixed part of the measured structure is selected as the reference.

[0012] Based on the aforementioned benchmark, the interference phase of the two-dimensional single-view complex radar image is corrected against vibration interference, and the phase component corresponding to the residual vibration interference is removed to obtain the target phase of the structure displacement.

[0013] The target phase is unwrapped to eliminate phase ambiguity, and the unwrapped phase is converted into vertical displacement data of the measured structure.

[0014] Multiple sets of radar echo signals are continuously acquired, and image generation and registration, phase correction, phase unwrapping and displacement conversion operations are repeatedly performed to generate the vertical displacement sequence of the measured structure and obtain the displacement of the measured structure.

[0015] Preferably, the step of acquiring the radar echo signal reflected by the structure under test using a millimeter-wave radar configured with an anti-vibration interference structure includes:

[0016] The millimeter-wave radar is deployed on a pre-set measurement platform, and the radar observation attitude is adjusted to upward observation so that the radar signal is aimed at the structure being measured.

[0017] The millimeter-wave radar is controlled to operate in frequency-modulated continuous wave mode to collect radar echo signals reflected by the structure under test under external load, and the collection timestamp is recorded synchronously.

[0018] The vibration-damping structure includes a vibration damping component and a phase stabilizing component. The vibration damping component is made of elastic damping material to suppress the transmission of external vibrations to the radar body. The phase stabilizing component fixes the radar's transmitting antenna array and receiving antenna array through a rigid frame to maintain the relative position stability of the phase center of the transmitting antenna and the phase center of the receiving antenna.

[0019] Preferably, the step of focusing the radar echo signal to generate a two-dimensional single-view complex radar image includes:

[0020] The radar echo signal is focused using a far-field pseudo-polar imaging algorithm;

[0021] Based on the transmitting and receiving antennas of millimeter-wave radar, a virtual antenna array element is synthesized using the phase center approximation principle. The spatial sampling characteristics of the virtual antenna array element are utilized to reduce the computational load of signal processing. A dynamic resolution enhancement function is introduced during the focusing process. The formula is: ,in, For signal frequency, The radar's operating center frequency, This is the resolution enhancement factor. The frequency bandwidth adjustment parameter is used to optimize the image spatial resolution through the enhancement function, generating a two-dimensional single-view complex radar image.

[0022] Preferably, in the registered two-dimensional single-view complex radar image, selecting a scattering unit with high echo intensity and stable phase at a fixed location of the measured structure as a reference includes:

[0023] In a two-dimensional single-view complex radar image, the average intensity of the radar echo signal is calculated, and values ​​higher than the average intensity are set as a preset threshold. Scattering units with echo intensity higher than the preset threshold are then filtered out.

[0024] From the selected scattering units, scattering units located at fixed locations such as supports and foundation platforms of the structure under test are chosen;

[0025] Calculate the phase standard deviation of the selected scattering unit in multiple consecutive two-dimensional single-view complex radar images, and select scattering units whose phase standard deviation is less than a preset deviation threshold.

[0026] By constructing a phase stability evaluation function The candidate scattering unit is evaluated a second time using the following formula: ,in, As a candidate scattering unit, The number of consecutive image frames. For the first Scattering units in frame image phase, For scattering unit The average phase, selected Scattering units with values ​​greater than a preset evaluation threshold are used as the benchmark.

[0027] Preferably, the step of performing vibration-resistant phase correction on the interferometric phase of the two-dimensional single-view complex radar image based on the reference includes:

[0028] Obtain the interferometric phase of two adjacent two-dimensional single-view complex radar images The interference phase Includes the structural displacement phase and the residual vibration disturbance phase;

[0029] The interference phase Convert to vertical phase The transformation relation satisfies: ,in, The angle between the line-of-sight direction and the vertical direction of the millimeter-wave radar's transmitted signal;

[0030] Vertical phase based on the aforementioned reference For the total number of pixels in the image Linear detrending processing is performed to remove residual vibration interference phase; a spatial gradient compensation factor is introduced. The phase after linear detrending is corrected using the following formula: ,in, Let be the spatial gradient magnitude at pixel (x, y). The maximum value of the gradient magnitude across the entire image is used to obtain the target phase that reflects only the displacement of the structure. .

[0031] Preferably, the process for all image pixels... Perform linear detrending processing, including:

[0032] The vertical phase corresponding to the residual vibration interference Modeled as a spatial linear function, the formula is: ,in, , These are the pixel coordinates of a two-dimensional single-view complex radar image. The coefficient of the constant term, , They are respectively , The linear coefficient of direction;

[0033] Select at least two of the aforementioned references and obtain the pixel coordinates corresponding to each reference. and vertical phase Substituting the spatial linear function, the objective function is constructed using ordinary least squares. , Using the baseline quantity, iterative calculations are performed to obtain... , , ;

[0034] The total number of pixels in the image Subtract the corresponding coordinates Below The phase after preliminary correction is obtained. The formula is: .

[0035] Preferably, the step of unwrapping the target phase to eliminate phase ambiguity and converting the unwrapped phase into vertical displacement data of the measured structure includes:

[0036] Using the branch cutting method to target phase Perform phase unwrapping to eliminate Phase blurring, obtaining the unwrapped phase Based on the wavelength of the millimeter-wave radar signal ,Will Convert to vertical displacement The conversion formula is: Introducing a temperature compensation coefficient For vertical displacement Environmental modifications are performed using the following formula: ,in, The temperature phase sensitivity coefficient of the millimeter-wave radar is used to obtain the corrected vertical displacement data. .

[0037] Preferably, generating the vertical displacement sequence of the measured structure over time includes:

[0038] Set time window length For continuously generated vertical displacement data Perform sliding window filtering to filter out random noise interference;

[0039] By constructing a time series smoothing function The filtered displacement data is optimized using the following formula: ,in, For the current moment, The number of data points within the smoothing window. The data collection time interval For data points within a smoothing window;

[0040] Based on the optimized displacement data, a vertical displacement sequence is generated by arranging the data in time stamp order. The sequence contains the vertical displacement information of the measured structure at each moment, thus completing the displacement measurement.

[0041] The displacement measurement device based on millimeter-wave radar structure with anti-vibration interference specifically includes:

[0042] The main body of the millimeter-wave radar is equipped with a transmitting antenna array and a receiving antenna array, which are used to transmit radar signals and receive radar echo signals reflected by the structure under test.

[0043] A rigid phase stabilizing frame is fitted onto the outside of the millimeter-wave radar body. Its inner side is provided with positioning slots adapted to the transmitting antenna array and the receiving antenna array. The positioning slots are fixedly connected to the antenna array to maintain the relative position stability of the phase center of the transmitting antenna and the phase center of the receiving antenna.

[0044] The shock-absorbing bracket is fixedly connected to the bottom of the rigid phase stabilizing frame and is used to support the millimeter-wave radar body and suppress the transmission of external vibrations to the radar body.

[0045] The signal processing unit is electrically connected to the main body of the millimeter-wave radar and is used to process the radar echo signal and generate a vertical displacement sequence of the structure under test.

[0046] Preferably, the signal processing unit includes:

[0047] The image generation module is used to focus the radar echo signal using a far-field pseudo-polar format imaging algorithm to generate a two-dimensional single-view complex radar image.

[0048] The image registration module is used to register two-dimensional single-view complex radar images to eliminate minor positional deviations;

[0049] The reference selection module is used to select scattering units with high echo intensity, located at a fixed part of the measured structure and with stable phase as references in the registered two-dimensional single-view complex radar image.

[0050] The phase correction module is used to convert the interference phase into a vertical phase and remove residual vibration interference phase through linear detrending processing.

[0051] The displacement conversion module is used to unwrap the target phase and convert the unwrapped phase into a vertical displacement based on the wavelength of the millimeter-wave radar transmitted signal, generating a vertical displacement sequence.

[0052] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0053] This invention suppresses the transmission of external vibrations to the radar body by configuring a vibration damping bracket and a phase stabilizing frame on the millimeter-wave radar hardware structure. At the same time, it ensures the relative stability of the phase centers of the transmitting and receiving antennas. This eliminates the source of vibration interference to radar phase measurement at the hardware level, laying the foundation for subsequent high-precision displacement inversion. It improves the anti-vibration interference performance of displacement measurement and ensures that stable echo signal phase information can still be obtained in complex vibration environments.

[0054] This invention employs a far-field pseudopolar imaging algorithm to generate two-dimensional single-look complex radar images and introduces a dynamic resolution enhancement function to optimize image quality. Simultaneously, through a precise reference scattering unit selection strategy combined with a phase stability evaluation function, reliable reference points are selected, providing an accurate reference for vibration interference correction of the interferometric phase. This enables the subsequent phase correction process to effectively distinguish between the true displacement phase of the structure and the vibration interference phase, achieving a dual improvement in the spatial resolution of displacement measurement and the reliability of the phase reference.

[0055] This invention converts the interference phase into a vertical phase and combines a phase correction method with linear detrending processing and spatial gradient compensation. This application removes the residual vibration interference phase component and obtains a target phase that only reflects the displacement of the structure. After phase unwrapping and displacement conversion, the vertical displacement data of the measured structure is accurately obtained, realizing a high-precision conversion from radar echo signal to the vertical displacement of the structure, which meets the requirements of the engineering field for sub-millimeter accuracy of displacement measurement.

[0056] This invention generates a vertical displacement sequence of the measured structure over time by performing time-series smoothing on continuously acquired displacement data. This sequence can clearly reflect the dynamic displacement change process of the structure, providing continuous and reliable basic data for structural health status analysis and vibration feature extraction. It realizes the leap from single-point displacement measurement to dynamic displacement sequence monitoring, and provides strong support for safety early warning and status assessment in the operation and maintenance of structures throughout their entire life cycle.

[0057] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0058] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0060] Based on the description of the figures and their corresponding technical content in the document, the titles of the figures are as follows:

[0061] Figure 1 : Schematic diagram of the displacement measurement method based on millimeter-wave radar structure vibration interference resistance;

[0062] Figure 2 Schematic diagram of the anti-vibration interference structure and signal processing unit assembly of millimeter-wave radar;

[0063] Figure 3 : Schematic diagram of the functional modules of a displacement measurement system based on millimeter-wave radar. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0065] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0066] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0067] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0068] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0069] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0070] Example 1

[0071] This embodiment mainly describes a displacement measurement method based on millimeter-wave radar structure vibration interference resistance, such as... Figure 1 As shown, it specifically includes:

[0072] The radar echo signal reflected by the structure under test is collected by a millimeter-wave radar equipped with a vibration-resistant structure.

[0073] The radar echo signal is focused to generate a two-dimensional single-view complex radar image, and registration is performed to eliminate minor positional deviations.

[0074] In the registered two-dimensional single-view complex radar image, the scattering unit with high echo intensity and stable phase at the fixed part of the measured structure is selected as the reference.

[0075] Based on the aforementioned benchmark, the interference phase of the two-dimensional single-view complex radar image is corrected against vibration interference, and the phase component corresponding to the residual vibration interference is removed to obtain the target phase of the structure displacement.

[0076] The target phase is unwrapped to eliminate phase ambiguity, and the unwrapped phase is converted into vertical displacement data of the measured structure.

[0077] Multiple sets of radar echo signals are continuously acquired, and image generation and registration, phase correction, phase unwrapping and displacement conversion operations are repeatedly performed to generate the vertical displacement sequence of the measured structure and obtain the displacement of the measured structure.

[0078] Furthermore, the radar echo signal acquisition specifically includes:

[0079] The millimeter-wave radar is fixedly installed on a pre-set measurement platform. The measurement platform must meet the installation requirement of stable relative position with the structure under test, ensuring that the radar observation angle is not affected by unexpected movement of the platform. The radar observation attitude is adjusted to the upward observation mode, so that the main beam axis of the radar's transmitted signal is precisely aligned with the measurement area of ​​the structure under test, ensuring that the measured area is within the effective observation field of view of the radar antenna, and that there are no obstructions between the radar and the structure under test interfering with signal transmission.

[0080] The millimeter-wave radar is controlled to operate strictly in frequency-modulated continuous wave mode. In this mode, the frequency of the radar's transmitted signal changes linearly with time, and range information is obtained by the frequency difference between the transmitted and received signals. During radar acquisition, the acquisition timestamp corresponding to each set of radar echo signals is recorded synchronously. The recording accuracy of the timestamps must match the radar's signal acquisition frequency to ensure the accuracy of subsequent time series analysis. The acquired radar echo signals must contain both amplitude and phase information.

[0081] Furthermore, the radar echo signal focusing processing and image registration specifically include:

[0082] The acquired radar echo signal is focused using a far-field pseudo-polar imaging algorithm. The algorithm first transforms the echo signal from the polar coordinate domain to the Cartesian coordinate domain, and then achieves spatial focusing of the signal through two-dimensional Fourier transform, thereby improving the spatial resolution of the image.

[0083] Based on the physical parameters of the actual transmitting and receiving antennas of millimeter-wave radar, the signals transmitted and received at different times are equivalent to spatial sampling signals of virtual antenna elements through the phase center approximation principle. The number of virtual antenna elements is determined by the number of channels and signal sampling points of the actual antenna. By utilizing the spatial sampling characteristics of virtual antenna elements, two-dimensional signal processing is transformed into step-by-step processing, which greatly reduces the computational load of signal processing.

[0084] Introducing a dynamic resolution enhancement function during focusing processing , This is the instantaneous frequency of the radar echo signal, and its value range is consistent with the radar's operating frequency bandwidth. The radar's operating center frequency is fixed by the radar hardware design parameters, with an accuracy controlled within ±1MHz. The resolution enhancement factor is determined by the size of the measured structure and the required measurement accuracy; the larger the factor, the more significant the resolution improvement effect. The frequency bandwidth adjustment parameter is positively correlated with the radar signal bandwidth, and its value ranges from 0.1B to 0.3B (B is the radar operating frequency bandwidth). The enhancement function is used to perform weighted optimization on the signal frequency components, enhance the response of the target frequency components, suppress noise frequency components, and generate a two-dimensional single-view complex radar image with a spatial resolution ≥0.5mm. The phase information preservation accuracy of the image is ≤0.01rad.

[0085] A phase correlation-based image registration method is employed to register continuously generated two-dimensional single-view complex radar images. Using the first frame as a reference, the phase correlation coefficient between subsequent frames and the reference frame is calculated. By searching for the positional offset corresponding to the maximum value of the phase correlation coefficient, the image position is obtained. shaft and Minor positional deviations in the axial direction. Based on the obtained positional offset, bilinear interpolation transformation is performed on the image to correct minor positional deviations, ensuring that the pixel coordinates of the same scattering unit are consistent in consecutive frames. The positional deviation of the registered image is controlled within ±0.1 pixels.

[0086] Furthermore, the selection of the reference scattering unit specifically involves: calculating the average intensity of the radar echo signal corresponding to all pixels in a two-dimensional single-view complex radar image. The calculation formula is: (in , These represent the number of rows and columns of the image, respectively. For pixels (echo intensity value); set a preset threshold Set to 1.2× Screening out echo intensity ≥ The scattering units form a preliminary candidate set.

[0087] From the initial candidate set, based on the structural design drawings of the structure under test, scattering units located at fixed locations such as supports and foundation platforms of the structure under test are identified and selected. The criteria for determining fixed locations are: the location is rigidly connected to the ground or fixed foundation, and its displacement is ≤0.001mm during the deformation of the structure under test, ensuring that the selected scattering units are not affected by the deformation displacement of the structure.

[0088] Calculate the phase standard deviation, and for the selected fixed-position scattering units, calculate their phase standard deviation in continuous... Phase standard deviation in two-dimensional single-view complex radar images The calculation formula is: (in For the first Scattering units in frame image phase value, For scattering unit exist (Average phase value in frame image); set preset deviation threshold. =0.05 rad, select the phase standard deviation ≤ The scattering unit enters the secondary evaluation;

[0089] Applying the phase stability evaluation function, by constructing the phase stability evaluation function A secondary evaluation of candidate scattering units is performed, and the function value is positively correlated with phase stability. A preset evaluation threshold is set. Select ≥ The scattering unit is used as a reference to ensure that the phase stability of the reference scattering unit meets the requirements for vibration interference correction.

[0090] Furthermore, the interference phase anti-vibration interference correction specifically involves interference phase acquisition and vertical direction conversion;

[0091] To calculate the interferometric phase, the interferometric phase is obtained by performing complex conjugate multiplication on two adjacent registered two-dimensional single-view complex radar images. ,Right now (in For the first Complex pixel values ​​of a frame image. For the first Complex pixel values ​​of a frame image. (This represents the complex conjugate operation); the interference phase. It includes the phase component corresponding to the displacement of the measured structure and the phase component corresponding to the residual vibration disturbance.

[0092] The vertical phase is converted, and the interferometric phase is adjusted according to the installation angle parameters of the millimeter-wave radar. Convert to vertical phase The transformation relation satisfies ,in The angle between the line-of-sight direction and the vertical direction of the millimeter-wave radar's transmitted signal is determined by attitude measurements during radar installation, with a measurement accuracy ≤0.1°. The calculation precision is retained to four decimal places.

[0093] Perform linear detrending processing to remove the vertical phase corresponding to the residual vibration disturbance. Model as a spatial linear function ,in Pixel coordinates of a two-dimensional single-view complex radar image ), The coefficient of the constant term, , They are respectively The linear coefficients of the direction are determined by the model, which assumes that the residual vibration interference is linearly distributed in the image space. The linear coefficients are solved by selecting at least two known reference scattering units and obtaining the pixel coordinates corresponding to each reference. and vertical phase Substitute it into the spatial linear function, and construct the objective function using ordinary least squares. (in As the baseline quantity, Taking the partial derivatives of the objective function and setting them to zero yields a system of linear equations, which can be solved iteratively using matrix operations. , , ;

[0094] Preliminary phase correction, vertical phase of all pixels in the image. Subtract the corresponding coordinates Residual vibration disturbance phase below The phase after preliminary correction is obtained. The formula is To initially remove the linear components of residual vibration interference;

[0095] Modify spatial gradient compensation by introducing a spatial gradient compensation factor. For the phase after preliminary correction Make corrections, among which For pixels The spatial gradient magnitude at that location, through The operator is calculated and obtained using the following formula: ( , They are respectively (gradient value in direction) The maximum value of the spatial gradient magnitude across all pixels in the image is obtained by traversing all pixels in the image, and the corrected formula is as follows: By correcting and compensating for the spatial nonlinear vibration disturbance component, a target phase that only reflects the displacement of the structure is obtained. .

[0096] Furthermore, the phase unwrapping employs a branch-cutting method for the target phase. Perform phase unwrapping to eliminate Phase blurring; the implementation process of the branching method is as follows: identify phase discontinuities in the target phase image, and then set a phase gradient threshold (the threshold is set to...). Pixels with phase transitions exceeding a threshold are selected as singularities. Then, branch tangents are constructed based on the distribution characteristics of these singularities. These branch tangents connect only singularities of opposite signs and do not intersect or close. Within the region avoiding the branch tangents, the phase is integrated using path integration to obtain the unwrapped phase. The phase error after unwrapping is ≤0.02rad.

[0097] Correcting the vertical displacement conversion based on the wavelength of the millimeter-wave radar transmitted signal. The phase after untangling Convert to vertical displacement The conversion formula is: ;in Radar operating center frequency Confirmed, satisfied ( (The speed at which electromagnetic waves propagate in air).

[0098] Correcting temperature compensation by introducing a temperature compensation coefficient. For vertical displacement Environmental correction is performed, and the correction formula is as follows: ,in The temperature phase sensitivity coefficient of the millimeter-wave radar is determined by the radar's factory calibration test. The temperature change of the radar's operating environment is measured in real time by a temperature sensor mounted on the radar housing, with a measurement accuracy of ≤±0.1℃. Temperature compensation is used to eliminate the influence of ambient temperature changes on the displacement measurement results, yielding corrected vertical displacement data. .

[0099] Furthermore, the generation of the vertical displacement sequence is first processed by sliding window filtering, with a set time window length. Time window length The value is the data acquisition time interval. Integer multiples of ( , (Number of data points within the window). For continuously generated vertical displacement data... A sliding window filtering process is performed, using the median filtering algorithm within each window. The displacement data are sorted, and the median value is taken as the output data of the window. Random noise interference is filtered out, and the signal-to-noise ratio of the filtered displacement data is ≥40dB.

[0100] Time series smoothing is performed by constructing a time series smoothing function. The filtered displacement data is then optimized, whereby... This corresponds one-to-one with the data collection timestamp at the current moment. To ensure the number of data points within the smoothing window remains consistent with the window length of the sliding window filter, The data acquisition time interval is determined by the radar's acquisition frequency (acquisition frequency ≥ 10Hz, i.e.) ≤0.1s), To smooth the data points within the window, For the current moment The previous The corrected vertical displacement data at each acquisition interval is used to reduce the temporal fluctuation of the displacement data and improve the stability of the displacement sequence through this smoothing function.

[0101] A vertical displacement sequence is constructed by arranging the optimized displacement data in chronological order of acquisition timestamps. This sequence is a one-dimensional time series data, where each data point contains timestamp information and the corresponding corrected vertical displacement data. The temporal resolution of the sequence and the data acquisition time interval The sequence is consistent with t, and the vertical displacement information of the measured structure at each moment within the measurement time period is fully presented through this sequence, thus completing the displacement measurement.

[0102] This embodiment details how a combination of anti-vibration interference structure and signal processing technology for millimeter-wave radar effectively suppresses the impact of external vibrations on the radar, ensuring the stability and accuracy of radar echo signal acquisition. Focusing processing and dynamic resolution enhancement improve the spatial resolution of the two-dimensional single-view complex radar image, and registration eliminates positional deviations, laying a precise image foundation for subsequent analysis. By selecting a reference scattering unit and performing phase correction, residual vibration interference phase components are removed. Combined with phase unwrapping and environmental compensation, the vertical displacement data of the structure is accurately acquired. The generated vertical displacement sequence completely and accurately reflects the displacement changes of the measured structure, achieving high-precision and stable measurement of structural displacement and meeting the accuracy and reliability requirements of structural displacement monitoring scenarios.

[0103] Example 2

[0104] This embodiment describes in detail a displacement measurement device based on millimeter-wave radar structure vibration interference resistance, used to realize a displacement measurement method based on millimeter-wave radar structure vibration interference resistance. It includes a millimeter-wave radar body, a rigid phase-stabilized frame, a vibration damping support, and a signal processing unit, such as... Figure 2 As shown, specifically:

[0105] The millimeter-wave radar is the core signal transceiver component of the device, integrating both transmitting and receiving antenna arrays. Both utilize microstrip patch antenna structures, and the number of antenna elements can be flexibly configured according to actual measurement accuracy requirements (typically 8-16 elements). Operating in the 24-77 GHz frequency band, it stably outputs frequency-modulated continuous wave signals. The frequency of this signal changes linearly with time, allowing for precise acquisition of distance information through the frequency difference between the transmitted and received signals. The receiving antenna array possesses high-sensitivity signal acquisition capabilities, simultaneously acquiring radar echo signals reflected from the measured structure, completely preserving the amplitude and phase information of the signal, providing high-quality raw data for subsequent signal processing. Simultaneously, a high-precision temperature sensor is built into the radar body, enabling real-time monitoring of ambient temperature changes, providing accurate environmental parameters for temperature compensation of subsequent displacement data.

[0106] The rigid phase stabilizing frame is made of aerospace-grade high-strength aluminum alloy and is integrally CNC machined into a rectangular frame structure. The frame thickness is designed according to the size and weight of the millimeter-wave radar body to ensure that the frame itself has sufficient rigidity to effectively resist deformation caused by external stress and temperature changes. The inner side of the frame corresponds to the installation position of the transmitting antenna array and the receiving antenna array, and is precisely machined with positioning slots that are perfectly adapted to the shape and size of the antenna array. The inner wall of the slot is sprayed with an anti-slip and wear-resistant coating, which can not only avoid surface wear during antenna array installation, but also enhance connection stability. The transmitting antenna array and the receiving antenna array are rigidly connected to the positioning slots by high-strength hexagonal bolts, ensuring that the relative position deviation between the phase center of the transmitting antenna and the phase center of the receiving antenna is always maintained within ±0.01mm after installation. Structurally, this avoids phase center offset caused by frame deformation, antenna loosening, and other problems, thus ensuring phase stability during radar signal transmission and reception.

[0107] The vibration damping bracket consists of three parts: a base, a damping column, and a connecting plate, forming a multi-level vibration buffer structure. The base is fixedly connected to the pre-set mounting surface of the measuring carrier by expansion bolts, ensuring that the bracket is installed stably without the risk of loosening or displacement. The damping column is the core vibration damping component, which is integrally molded from a high-elasticity damping material and has a cylindrical structure. The connecting plate is made of the same aerospace-grade aluminum alloy as the rigid phase-stabilized frame and is fixedly connected to the pre-set mounting holes at the bottom of the frame by bolts. The two ends of the damping column are respectively bonded to the base and the connecting plate with high-strength structural adhesive, forming a vibration transmission path of base-dampening column-connecting plate-frame. Through the elastic deformation and energy absorption of the damping column, the transmission of external vibration to the millimeter-wave radar body is significantly suppressed, reducing the interference of vibration on the radar signal transmission and reception accuracy.

[0108] The signal processing unit adopts an embedded processor architecture, integrating a high-performance FPGA (Field-Programmable Gate Array) and ARM (Microprocessor), possessing high-speed data processing, logic control, and real-time data processing capabilities. It achieves bidirectional electrical connection with the millimeter-wave radar main body via shielded data lines. On one hand, it can receive raw echo data transmitted by the radar in real time; on the other hand, it can send control commands such as switching operating modes and adjusting the acquisition frequency to the radar main body. Its internal functional modules include an image generation module, an image registration module, a reference selection module, a phase correction module, and a shift conversion module, such as... Figure 3 As shown, specifically:

[0109] The image generation module incorporates a far-field pseudo-polar imaging algorithm. After receiving the raw radar echo data, it first transforms the data from polar coordinates to Cartesian coordinates, converting the non-uniformly sampled echo data into regular grid data. Subsequently, it performs spatial focusing processing on the transformed data through two-dimensional Fourier transform to improve the spatial resolution of the image. At the same time, the module also introduces a dynamic resolution enhancement mechanism, which strengthens the signal response of the target area and suppresses noise interference by weighting and optimizing the signal components of different frequency bands, thereby generating a two-dimensional single-look complex radar image with high spatial resolution, complete phase information, and clear target features.

[0110] The image registration module employs a phase correlation-based image registration algorithm. Using the first frame of the acquired 2D single-view complex radar image as a reference frame, it calculates the phase correlation between each subsequent image frame and the reference frame. By searching for the position coordinates corresponding to the maximum phase correlation coefficient, it determines the position of subsequent images within the reference frame. axis, The image is corrected at the pixel level by using a bilinear interpolation algorithm based on the calculated position deviation. The spatial coordinates of the image pixels are adjusted to keep the pixel coordinates of the same scattering unit consistent in multiple consecutive frames of images. This completely eliminates the image position deviation caused by factors such as small radar jitter and slight displacement of the carrier, and provides a unified spatial coordinate reference for subsequent phase analysis and reference selection.

[0111] The benchmark selection module is as follows:

[0112] Calculate the average echo intensity of all pixels in a two-dimensional single-view complex radar image, set 1.2 times this average value as the intensity screening threshold, and filter out scattering units with echo intensity higher than the threshold to initially exclude scattering units corresponding to weak signals and noise interference.

[0113] Based on the design drawings and structural features of the structure under test, scattering units located at fixed locations such as structural supports and foundation platforms are identified and selected from the initially screened scattering units to ensure that the selected units are not affected by the deformation and displacement of the structure itself.

[0114] Calculate the phase standard deviation of a fixed-location scattering element in multiple consecutive frames of two-dimensional single-view complex radar images, set a phase standard deviation threshold, and select scattering elements with small phase fluctuations and high stability as candidate benchmarks.

[0115] The candidate benchmarks are screened a second time by a phase stability evaluation mechanism. The phase change trend and fluctuation amplitude of the candidate units in consecutive frame images are comprehensively evaluated, and the scattering unit with the best phase stability is selected as the formal benchmark.

[0116] The phase correction module performs complex conjugate operations on two adjacent registered two-dimensional single-view complex radar images to generate an interferometric phase that includes the displacement phase of the measured structure and the residual vibration interference phase. Subsequently, based on the installation angle parameters of the millimeter-wave radar, the interferometric phase is converted into a vertical phase to ensure that the phase information is consistent with the vertical displacement direction of the structure. The vertical phase corresponding to the residual vibration interference is modeled as a spatial linear distribution. At least two determined reference scattering units are selected, and the pixel coordinates and vertical phase of the reference units are obtained. The coefficients of the linear distribution are solved by data fitting. Based on the coefficients, the vertical phase of all pixels in the image is linearly detrended to initially remove the linear component of the residual vibration interference. A spatial gradient compensation mechanism is introduced. By calculating the spatial gradient distribution of the image pixels, the phase after linear detrending is further corrected to compensate for the phase deviation caused by spatial nonlinear vibration interference, thus obtaining the target phase that only reflects the displacement of the measured structure.

[0117] The displacement transformation module employs a branch-cutting method to unwrap the target phase. By identifying phase discontinuities (singularities) in the phase image, it constructs non-intersecting and non-closed branch-cutting lines. Within the region avoiding these branch-cutting lines, the phase is eliminated through path integration. To address the fuzzy problem, continuous unwrapped phase data is obtained. Based on the wavelength parameters of the millimeter-wave radar's transmitted signal, the unwrapped phase data is converted into corresponding vertical displacement data. Combining this with ambient temperature change data collected by the radar's built-in temperature sensor, a temperature compensation mechanism is introduced to correct the converted vertical displacement data, eliminating the impact of temperature changes on the radar's phase measurement accuracy. The continuously acquired vertical displacement data is then subjected to sliding window filtering and time series smoothing to filter out random noise interference. The vertical displacement sequence of the measured structure is generated by arranging the data in timestamp order, fully presenting the displacement changes of the structure during the measurement period.

[0118] This embodiment describes in detail how the interference of vibration on the displacement measurement of millimeter-wave radar is effectively eliminated by using the main body of the millimeter-wave radar, the rigid phase stabilizing frame, the vibration damping bracket and the signal processing unit, thereby improving the measurement accuracy and stability and realizing high-precision, continuous and stable monitoring of the vertical displacement of the measured structure.

[0119] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter changes made to these embodiments within the spirit and principles of the present invention, without departing from the principles and spirit of the present invention, through conventional substitutions or to achieve the same function, fall within the scope of protection of the present invention.

Claims

1. A method for measuring displacement based on a millimeter wave radar structure resistant to vibration interference, characterized in that, include: The radar echo signal reflected by the structure under test is collected by a millimeter-wave radar equipped with a vibration-resistant structure. The radar echo signal is focused to generate a two-dimensional single-view complex radar image, and registration is performed to eliminate minor positional deviations. In the registered two-dimensional single-view complex radar image, the scattering unit with high echo intensity and stable phase at the fixed part of the measured structure is selected as the reference. Based on the aforementioned benchmark, the interference phase of the two-dimensional single-view complex radar image is corrected against vibration interference, and the phase component corresponding to the residual vibration interference is removed to obtain the target phase of the structure displacement. The target phase is unwrapped to eliminate phase ambiguity, and the unwrapped phase is converted into vertical displacement data of the measured structure. Multiple sets of radar echo signals are continuously acquired, and image generation and registration, phase correction, phase unwrapping and displacement conversion operations are repeatedly performed to generate the vertical displacement sequence of the measured structure and obtain the displacement of the measured structure.

2. The method for measuring displacement based on millimeter wave radar structure anti-vibration interference according to claim 1, characterized in that, The acquisition of radar echo signals reflected by the tested structure using a millimeter-wave radar equipped with an anti-vibration interference structure includes: The millimeter-wave radar is deployed on a pre-set measurement platform, and the radar observation attitude is adjusted to upward observation so that the radar signal is aimed at the structure being measured. The millimeter-wave radar is controlled to operate in frequency-modulated continuous wave mode to collect radar echo signals reflected by the structure under test under external load, and the collection timestamp is recorded synchronously. The vibration-damping structure includes a vibration damping component and a phase stabilizing component. The vibration damping component is made of elastic damping material to suppress the transmission of external vibrations to the radar body. The phase stabilizing component fixes the radar's transmitting antenna array and receiving antenna array through a rigid frame to maintain the relative position stability of the phase center of the transmitting antenna and the phase center of the receiving antenna.

3. The method for displacement measurement based on millimeter wave radar structure anti-vibration interference according to claim 1, characterized in that, The step of focusing the radar echo signal to generate a two-dimensional single-view complex radar image includes: The radar echo signal is focused using a far-field pseudo-polar imaging algorithm; Based on the transmitting antenna and receiving antenna of millimeter wave radar, a virtual antenna element is synthesized through phase center approximation principle, and the signal processing calculation amount is reduced by using the spatial sampling characteristics of the virtual antenna element; a dynamic resolution enhancement function is introduced in the focusing processing process , the formula is: , wherein, is the signal frequency, is the radar working center frequency, is the resolution enhancement coefficient, is the frequency bandwidth adjustment parameter, the image spatial resolution is optimized by the enhancement function, and a two-dimensional single-view complex radar image is generated.

4. The displacement measurement method based on millimeter-wave radar structure vibration interference resistance according to claim 1, characterized in that, In the registered two-dimensional single-view complex radar image, a scattering element with high echo intensity and stable phase at a fixed location of the measured structure is selected as a reference, including: In a two-dimensional single-view complex radar image, the average intensity of the radar echo signal is calculated, and values ​​higher than the average intensity are set as a preset threshold. Scattering units with echo intensity higher than the preset threshold are then filtered out. From the selected scattering units, scattering units located at fixed locations such as supports and foundation platforms of the structure under test are chosen; Calculate the phase standard deviation of the selected scattering unit in multiple consecutive two-dimensional single-view complex radar images, and select scattering units whose phase standard deviation is less than a preset deviation threshold. By constructing a phase stability evaluation function The candidate scattering unit is evaluated a second time using the following formula: ,in, As a candidate scattering unit, The number of consecutive image frames. For the first Scattering units in frame image phase, For scattering unit The average phase, selected Scattering units with values ​​greater than a preset evaluation threshold are used as the benchmark.

5. The displacement measurement method based on millimeter-wave radar structure vibration interference resistance according to claim 1, characterized in that, The vibration interference correction of the interferometric phase of the two-dimensional single-view complex radar image based on the reference includes: Obtain the interferometric phase of two adjacent two-dimensional single-view complex radar images The interference phase Includes the structural displacement phase and the residual vibration disturbance phase; The interference phase Convert to vertical phase The transformation relation satisfies: ,in, The angle between the line-of-sight direction and the vertical direction of the millimeter-wave radar's transmitted signal; Vertical phase based on the aforementioned reference For the total number of pixels in the image Linear detrending processing is performed to remove residual vibration interference phase; a spatial gradient compensation factor is introduced. The phase after linear detrending is corrected using the following formula: ,in, Let be the spatial gradient magnitude at pixel (x, y). The maximum value of the gradient magnitude across the entire image is used to obtain the target phase that reflects only the displacement of the structure. .

6. The displacement measurement method based on millimeter-wave radar structure vibration interference resistance according to claim 5, characterized in that, The pixels of the entire image Perform linear detrending processing, including: The vertical phase corresponding to the residual vibration interference Modeled as a spatial linear function, the formula is: ,in, , These are the pixel coordinates of a two-dimensional single-view complex radar image. The coefficient of the constant term, , They are respectively , The linear coefficient of direction; Select at least two of the aforementioned references and obtain the pixel coordinates corresponding to each reference. and vertical phase Substituting the spatial linear function, the objective function is constructed using ordinary least squares. , Using the baseline quantity, iterative calculations are performed to obtain... , , ; The total number of pixels in the image Subtract the corresponding coordinates Below The phase after preliminary correction is obtained. The formula is: .

7. The displacement measurement method based on millimeter-wave radar structure vibration interference resistance according to claim 1 or 5, characterized in that, The step of unwrapping the target phase to eliminate phase ambiguity and converting the unwrapped phase into vertical displacement data of the measured structure includes: Using the branch cutting method to target phase Perform phase unwrapping to eliminate Phase blurring, obtaining the unwrapped phase Based on the wavelength of the millimeter-wave radar signal ,Will Convert to vertical displacement The conversion formula is: Introducing a temperature compensation coefficient For vertical displacement Environmental modifications are performed using the following formula: ,in, The temperature phase sensitivity coefficient of the millimeter-wave radar is used to obtain the corrected vertical displacement data. .

8. The displacement measurement method based on millimeter-wave radar structure vibration interference resistance according to claim 1, characterized in that, The generation of the vertical displacement sequence of the measured structure over time includes: Set time window length For continuously generated vertical displacement data Perform sliding window filtering to filter out random noise interference; By constructing a time series smoothing function The filtered displacement data is optimized using the following formula: ,in, For the current moment, The number of data points within the smoothing window. The data collection time interval For data points within a smoothing window; Based on the optimized displacement data, a vertical displacement sequence is generated by arranging the data in time stamp order. The sequence contains the vertical displacement information of the measured structure at each moment, thus completing the displacement measurement.

9. A displacement measurement device based on millimeter-wave radar structure with anti-vibration interference, applicable to any one of claims 1 to 8, characterized in that, include: The main body of the millimeter-wave radar is equipped with a transmitting antenna array and a receiving antenna array, which are used to transmit radar signals and receive radar echo signals reflected by the structure under test. A rigid phase stabilizing frame is fitted onto the outside of the millimeter-wave radar body. Its inner side is provided with positioning slots adapted to the transmitting antenna array and the receiving antenna array. The positioning slots are fixedly connected to the antenna array to maintain the relative position stability of the phase center of the transmitting antenna and the phase center of the receiving antenna. The shock-absorbing bracket is fixedly connected to the bottom of the rigid phase stabilizing frame and is used to support the millimeter-wave radar body and suppress the transmission of external vibrations to the radar body. The signal processing unit is electrically connected to the main body of the millimeter-wave radar and is used to process the radar echo signal and generate a vertical displacement sequence of the structure under test.

10. The displacement measurement device based on millimeter-wave radar structure with anti-vibration interference according to claim 9, characterized in that, The signal processing unit includes: The image generation module is used to focus the radar echo signal using a far-field pseudo-polar format imaging algorithm to generate a two-dimensional single-view complex radar image. The image registration module is used to register two-dimensional single-view complex radar images to eliminate minor positional deviations; The reference selection module is used to select scattering units with high echo intensity, located at a fixed part of the measured structure and with stable phase as references in the registered two-dimensional single-view complex radar image. The phase correction module is used to convert the interference phase into a vertical phase and remove residual vibration interference phase through linear detrending processing. The displacement conversion module is used to unwrap the target phase and convert the unwrapped phase into a vertical displacement based on the wavelength of the millimeter-wave radar transmitted signal, generating a vertical displacement sequence.

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