Non-contact concrete deformation testing system and method based on laser ranging technology

Abstract

The invention is applicable to the technical field of concrete deformation measurement, and particularly relates to a non-contact concrete deformation testing system and method based on a laser ranging technology, and the system comprises a laser ranging unit which is provided with a double-frequency phase modulation laser, an optical transceiver antenna and a phase detection circuit; the environmental parameter acquisition unit comprises a temperature sensor, a humidity sensor and an air pressure sensor; and the data processing unit carries an atmospheric refractive index calculation module, a Kalman filtering algorithm and a three-level early warning module, and supports wired / wireless data transmission. The distance measurement precision is high, and the concrete micro-deformation monitoring requirement is met; non-contact characteristic: non-damage monitoring on the concrete surface is realized through a diffuse reflection target; intelligent data processing: structural deformation and environmental noise are effectively distinguished, and the early warning reliability is improved; automatic monitoring is achieved, and the manual inspection cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete deformation measurement, and in particular relates to a non-contact concrete deformation testing system and method based on laser ranging technology. Background Art

[0002] In civil engineering, deformation monitoring of concrete structures is a key component in assessing structural safety. Traditional contact measurement methods (such as dial indicators and strain gauges) suffer from cumbersome installation, susceptibility to environmental interference, and inability to monitor real-time dynamic conditions, making them inadequate for monitoring large, complex structures. Non-contact measurement technologies, offering advantages such as high precision, automation, and remote monitoring, have become a research hotspot. Phase-shifted laser ranging technology, with its millimeter-level measurement accuracy and non-contact nature, demonstrates significant potential for structural deformation monitoring.

[0003] The current application of phase-based ranging technology in concrete deformation monitoring faces the following technical bottlenecks: (1) multipath effects lead to phase detection errors; (2) the influence of environmental parameters (temperature, humidity, atmospheric refractive index) on laser propagation velocity is not effectively compensated; and (3) the diffuse reflection characteristics of the concrete surface weaken the echo signal strength. Therefore, it is urgent to propose a concrete deformation testing method that integrates high-precision phase detection, environmental parameter compensation, and signal enhancement technology. Summary of the Invention

[0004] The purpose of the present invention is to provide a non-contact concrete deformation testing system based on laser ranging technology, aiming to solve the problem of phase detection error caused by multipath effect in the application of current phase ranging technology in concrete deformation monitoring.

[0005] The present invention is implemented as follows: a non-contact concrete deformation testing system based on laser ranging technology, the system comprising: A laser ranging unit, wherein the laser ranging unit is configured with a dual-frequency phase-modulated laser, an optical transceiver antenna, and a phase detection circuit; An environmental parameter acquisition unit, comprising a temperature sensor, a humidity sensor, and an air pressure sensor; The data processing unit is equipped with an atmospheric refractive index calculation module, a Kalman filter algorithm and a three-level warning module, and supports wired / wireless data transmission.

[0006] Preferably, the laser ranging unit has a ranging accuracy of 1 mm, a measuring range of 0.1 to 100 m, supports autofocus and diffuse reflection signal enhancement, and an avalanche photodiode is used at the receiving end.

[0007] Another object of the present application is to provide a non-contact concrete deformation testing method based on laser ranging technology, which is applied to the non-contact concrete deformation testing system based on laser ranging technology as described above, and the method comprises the following steps: System construction and measuring point arrangement: setting a reference point outside the deformation influence range of the concrete structure, installing an angle reflector at the reference point; pasting a diffuse reflection target as a measured point at the measured part of the concrete structure, the diffuse reflection target has a reflectivity of ≥80% and a surface set position mark; Initial data calibration: measuring the distance between the reference point and the measured point, collecting environmental parameters, calculating the atmospheric refractive index, correcting the laser propagation speed, repeatedly measuring, and taking the average value after removing the abnormal value as the initial distance; Real-time deformation monitoring: emitting a dual-frequency modulated light signal at a fixed frequency, measuring the phase difference between the emitted signal and the received signal through quadrature demodulation technology, correcting the speed of light based on real-time atmospheric parameters, calculating the real-time distance through the distance formula, eliminating distance ambiguity through multi-frequency combination algorithm, and calculating the deformation amount of the measuring point through the distance difference value; Data processing and early warning: denoising the deformation sequence, constructing a deformation-time curve, predicting the deformation trend through polynomial fitting, setting an early warning threshold, and issuing an early warning signal according to the early warning threshold.

[0008] Preferably, a dual-frequency phase laser range finder is used to measure the distance between the reference point and the measured point, and the dual-frequency phase laser range finder emits a modulated light signal with a frequency of f 1 and f 2, and the frequency is 50-100MHz.

[0009] Preferably, the environmental parameters include temperature, humidity and air pressure.

[0010] Preferably, the reference point is set on a stable bedrock or a fixed structure, the measured point is arranged in a crack-prone area, a stress concentration area or a key stress part of the concrete structure, and the distance between the measured point and the reference point is less than 100m.

[0011] Preferably, the temperature error is not more than 0.5°C, the humidity error is not more than 2%RH, the air pressure error is not more than 0.3hPa, and the atmospheric refractive index calculation error is less than .

[0012] Preferably, in the step of measuring the phase difference between the emitted signal and the received signal through quadrature demodulation technology, the quadrature demodulation technology adopts I / Q dual-channel phase detection, the phase difference is calculated through an inverse tangent function, the resolution is 0.001°, and the corresponding distance measurement accuracy is less than 0.3mm.

[0013] Preferably, the diffuse reflection target is an aluminum alloy plate with sandblasting treatment on the surface, the size is 100x100mm, a positioning circular hole is arranged at the center, and the aluminum alloy plate is bonded to the concrete surface through epoxy resin glue.

[0014] Preferably, the early warning signal includes on-site sound and light alarm, remote SMS notification and platform pop-up prompt, the early warning signal contains early warning information, the early warning information contains measuring point number, real-time deformation, early warning level and occurrence time.

[0015] The non-contact concrete deformation test system based on laser ranging technology provided by the application has ranging precision of , meets the demand of concrete micro-deformation monitoring, has non-contact property, realizes non-damage monitoring on the surface of concrete through diffuse reflection targets, is suitable for existing structures and newly-built projects, has intelligent data processing, integrates Kalman filtering and trend prediction algorithm, effectively distinguishes structural deformation from environmental noise, and improves early warning reliability, and has automatic monitoring, supports 24-hour continuous monitoring and remote data transmission, and greatly reduces manual inspection cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The structural diagram of the non-contact concrete deformation test system based on laser ranging technology provided by the embodiment of the application is shown in the figure. Figure 2 The phase modulation signal waveform diagram provided by the embodiment of the application is shown in the figure. Figure 3 The measuring point arrangement schematic diagram provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0018] As shown in the figure, the structural diagram of the non-contact concrete deformation test system based on laser ranging technology provided by the embodiment of the application is shown in the figure. Figure 1 The system comprises: A laser ranging unit, the laser ranging unit is configured with a dual-frequency phase modulation laser, an optical transceiver antenna and a phase detection circuit; An environmental parameter acquisition unit, the environmental parameter acquisition unit comprises a temperature sensor, a humidity sensor and a barometric pressure sensor; A data processing unit, the data processing unit is equipped with an atmospheric refractive index calculation module, a Kalman filtering algorithm and a three-level early warning module, and supports wired / wireless data transmission.

[0019] The application provides a non-contact concrete deformation test method based on laser ranging technology, which is applied to the non-contact concrete deformation test system based on laser ranging technology as described above. System architecture: A complete test system is constructed, which consists of the following three core modules to realize accurate monitoring of concrete structure deformation.

[0020] Laser ranging unit: As a key part of the system, it is equipped with a phase modulation laser, and the phase modulation signal is as shown in Figure 2 . The modulation frequency is carefully combined, for example, two different frequency modulation light signals of f 1 and f 2 are used. This dual-frequency design can effectively improve the ranging accuracy and eliminate distance ambiguity. The optical transmitting / receiving antenna is responsible for accurately transmitting the modulated light signal and efficiently receiving the return signal returned by the reflecting device. The high-precision phase detection circuit is used to accurately measure the phase difference between the transmitted signal and the received signal.

[0021] Environmental parameter acquisition unit: It integrates high-precision temperature sensor, humidity sensor and air pressure sensor. The temperature sensor has an accuracy of , which can accurately measure the change of environmental temperature; the humidity sensor has an accuracy of , which can accurately obtain real-time environmental humidity information; the air pressure sensor has an accuracy of , which is used to accurately measure atmospheric pressure. These sensors work together to collect real-time environmental parameters, providing key data support for subsequent calculation of atmospheric refractive index and correction of laser propagation speed.

[0022] Data processing unit: It is equipped with various advanced algorithms and functional modules. Among them, the deformation solving algorithm accurately calculates the deformation of the concrete structure according to the distance data measured by the laser ranging unit and the real-time environmental parameters provided by the environmental parameter acquisition unit. The warning module analyzes and judges the deformation data in real time according to the preset warning threshold. This unit supports wired / wireless data transmission, and can transmit measurement data and analysis results to remote monitoring terminals or other data processing equipment in a timely and stable manner, facilitating real-time monitoring and data analysis by staff.

[0023] Measurement point arrangement: Reference point setting: The selection of reference point is crucial and should be set on a stable bedrock or fixed structure outside the deformation influence range of the concrete structure. This is because the stable bedrock or fixed structure has minimal deformation, which can provide a reliable reference for the entire measurement system. Install an angle reflector on the reference point, which has high reflectivity and can efficiently reflect the light signal emitted by the laser ranging unit back to the receiving end, ensuring the strength and stability of the measurement signal. For example, in bridge engineering, a stable mountain bedrock near the bridge site is often chosen as the reference point, and a high-precision right-angle prism is installed as the angle reflector, with an angle error of ≤5″ to ensure the accuracy of the reflected light.

[0024] Test point arrangement: Test points should be arranged at key positions of the concrete structure, such as areas prone to cracking, stress concentration areas, or key stress positions. The deformation of these positions is of great significance for evaluating the safety and stability of the concrete structure. Paste the diffuse reflection target at the test point, which requires a reflectivity of more than 80% and a size of 100x100mm. Set the positioning mark in the center of the target to facilitate accurate determination of the measurement position. Take the box girder web as an example, paste the sandblasted aluminum alloy diffuse reflection target on the crack monitoring area, and firmly bond it with the concrete surface through epoxy resin glue to ensure that the target closely matches the concrete surface, conformal, and ensure the accuracy of the measurement.

[0025] Initial data calibration: atmospheric parameter calibration: atmospheric parameters have a significant impact on the speed of laser propagation, so it is necessary to accurately calculate the atmospheric refractive index to correct the speed of laser propagation. According to the formula, the atmospheric refractive index is calculated n : (Formula 1) where, T is the temperature (K), P is the air pressure (hPa), e is the water vapor pressure (hPa), , (T is the Celsius temperature).

[0026] Distance calibration: multiple repeated measurements are made on the reference point and the test point, and the average value is taken as the initial distance , the standard deviation is calculated, and the abnormal value exceeding is removed.

[0027] Real-time deformation monitoring: phase laser ranging principle: the distance is calculated by measuring the phase change of the modulated light in the measured distance. The modulated light emitted by the laser range finder encounters a reflection device (such as the corner reflector of the reference point and the diffuse reflection target of the test point) and returns to the range finder. Due to the time delay of light in the propagation process, a phase difference is generated between the emitted light and the received light. This phase difference is proportional to the distance of light propagation, and by measuring the phase difference and combining the wavelength of the modulated light and other parameters, the distance of light propagation can be calculated.

[0028] Dynamic ranging: the laser ranging unit continuously emits double-frequency modulated light at a fixed frequency set. At the same time of emitting light signals, the environmental parameter acquisition unit synchronously acquires the current temperature, humidity, air pressure and other environmental parameters, providing real-time data for subsequent light speed correction.

[0029] Phase calculation: Adopting quadrature demodulation technology (I / Q demodulation) to process the transmitted signal and the received signal, accurately measuring the phase difference between them. This technology decomposes the received complex signal into in-phase component (I) and quadrature component (Q) through I / Q dual-channel phase detection, and then calculates the phase difference using the arctangent function, with a resolution of 0.001°, corresponding to extremely high distance measurement accuracy.

[0030] Error compensation: According to the real-time collected environmental parameters, combined with the formula for calculating the atmospheric refractive index before, the propagation speed of laser in the atmosphere is corrected in real time. Using the corrected speed of light, the real-time distance is calculated through the accurate distance formula. In the calculation process, the multi-frequency combination algorithm is used to eliminate the distance ambiguity phenomenon. Based on the characteristics of dual-frequency modulated light signal, through the analysis and combination of measurement results at different frequencies, the problem of distance measurement uncertainty caused by phase ambiguity is effectively solved.

[0031] Deformation calculation: Comparing the real-time calculated distance with the initial distance determined in the initial data calibration stage, the difference between the two is the displacement of the measuring point relative to the reference point, which is the deformation of the measuring point. By continuously monitoring and calculating the deformation, the deformation of the concrete structure can be monitored in real time.

[0032] Data processing and early warning: Noise suppression: Kalman filter algorithm is used to process the collected displacement sequence. Kalman filter algorithm is a kind of efficient recursive filter algorithm, which can make optimal estimation of system state according to dynamic model and measurement data of system. In this invention, by reasonably setting the parameters of Kalman filter algorithm, such as process noise covariance and measurement noise covariance, random noise such as environmental vibration and electromagnetic interference is effectively filtered out, and the quality and stability of deformation data are improved.

[0033] Trend analysis: According to the noise-reduced deformation data, the deformation-time curve is constructed. Through the analysis of deformation-time curve, the deformation trend is predicted by using polynomial fitting and other mathematical methods. Polynomial fitting can find the polynomial function that best describes the deformation trend according to the characteristics of historical deformation data, so as to reasonably predict the deformation of concrete structure in the future, and provide important basis for structure safety evaluation.

[0034] Threshold early warning: Three-level early warning mechanism is set, including yellow early warning, orange early warning and red early warning. According to different types of concrete structures and engineering requirements, according to the design allowable deformation range of structure, historical monitoring data and relevant specification standards, the early warning thresholds of each level are set scientifically and reasonably (such as yellow early warning: ; orange early warning: ; red early warning: Once the monitored deformation reaches or exceeds the early warning threshold, the system immediately sends out early warning signals through multiple channels such as audible and visual alarms, SMS notifications, and platform pop-up prompts. The early warning information contains key information such as measurement point number, real-time deformation, early warning level, and occurrence time, so that staff can take appropriate measures in a timely manner to ensure the safety of the concrete structure.

[0035] In the embodiment of the present application, the equipment selection is as follows: Laser range finder: Z-Laser ZM100 phase range finder (modulation frequency 50 / 100 MHz, range finding accuracy ±1mm, measurement range 0.1-100m) is selected; Environmental sensor: integrated SHT30 temperature and humidity module (temperature accuracy ±0.3°C, humidity accuracy ±2%RH) and MS5611 barometric module (accuracy ±0.12 hPa); Data collector: UNO-2184G industrial computer from Advantech is used, which is equipped with LabVIEW data processing software.

[0036] As shown in Figure 3 , the field implementation steps are as follows: target installation: reference point: aluminum alloy support is fixed on the side of the bridge pile cap, and a right-angle prism (angle error ≤5″) is installed; measured point: diffuse reflection target with sandblasted surface treatment is pasted in the crack monitoring area of the box girder web, and is fixed with epoxy resin glue to ensure that the target is conformal with the concrete surface.

[0037] System calibration: warm up for 30 minutes after starting, and wait for the equipment to be stable; collect reference environmental parameters (temperature 25°C, humidity 60%RH, air pressure 1013 hPa), calculate the atmospheric refractive index ; measure the distance of the reference point for 20 times, the average value , and the standard deviation ; the initial distance measurement average value of the measured point is recorded in the table.

[0038] Continuous monitoring: set the monitoring frequency to 1 time / minute, and the data collector receives the distance measurement data and environmental parameters in real time; the software automatically executes the following processing procedures: correct the speed of light according to the current temperature T: ; solve the double-frequency phase difference and eliminate distance ambiguity; calculate the displacement ; draw the deformation curve, and trigger a yellow early warning when .

[0039] Data processing example: after 24 hours of continuous monitoring data of a measured point is filtered by Kalman filter, the deformation curve shows that the shrinkage displacement is 0.8mm due to temperature drop at night, and the expansion displacement is 0.5mm after temperature rises in the daytime, the overall deformation is within ±1mm, which is normal temperature deformation, and no early warning is triggered.

[0040] The above merely provides the preferred embodiment of the present application, and not intended to limit the present application. Accordingly, any modification, equivalent replacement, and improvement made without departing from the spirit and principle of the present application shall fall in the scope of protection of the present application.

Claims

1. Non-contact concrete deformation testing system based on laser ranging technology, characterized by: The system comprises: A laser ranging unit, wherein the laser ranging unit is configured with a dual-frequency phase-modulated laser, an optical transceiver antenna, and a phase detection circuit; An environmental parameter acquisition unit, comprising a temperature sensor, a humidity sensor, and an air pressure sensor; The data processing unit is equipped with an atmospheric refractive index calculation module, a Kalman filter algorithm and a three-level warning module, and supports wired / wireless data transmission.

2. The non-contact concrete deformation testing system based on laser ranging technology according to claim 1 is characterized in that: The laser ranging unit has a ranging accuracy of 1mm and a measurement range of 0.1 to 100m. It supports autofocus and diffuse reflection signal enhancement, and the receiving end uses an avalanche photodiode.

3. Non-contact concrete deformation testing method based on laser ranging technology, characterized in that: Applied to the non-contact concrete deformation testing system based on laser ranging technology as claimed in claim 1 or 2, the method comprises: System construction and measurement point arrangement: Set a reference point outside the range affected by the deformation of the concrete structure and install a corner reflector at the reference point; affix a diffuse reflection target to the part of the concrete structure to be measured as the measurement point. The diffuse reflection target has a reflectivity of ≥80% and a position mark is set on the surface; Initial data calibration: measure the distance between the reference point and the point to be measured, collect environmental parameters, calculate the atmospheric refractive index, correct the laser propagation speed, repeat the measurement, eliminate outliers and take the average value as the initial distance; Real-time deformation monitoring: Dual-frequency modulated optical signals are transmitted at a fixed frequency. The phase difference between the transmitted and received signals is measured using orthogonal demodulation technology. The speed of light is corrected based on real-time atmospheric parameters. The real-time distance is calculated using the distance formula. Distance ambiguity is eliminated using a multi-frequency combination algorithm. The deformation of the measuring point is calculated using the distance difference. Data processing and early warning: Denoise the deformation sequence, construct a deformation-time curve, predict the deformation trend through polynomial fitting, set the early warning threshold, and issue an early warning signal based on the early warning threshold.

4. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3 is characterized in that: A dual-frequency phase laser rangefinder is used to measure the distance between the reference point and the point to be measured. The emission frequency of the dual-frequency phase laser rangefinder is f 1 and f 2 modulated optical signal with a frequency of 50-100MHz.

5. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3 is characterized in that: Environmental parameters include temperature, humidity, and air pressure.

6. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3 is characterized in that: The benchmark point is set on a stable bedrock or fixed structure, and the test point is arranged in the crack-prone area, stress concentration area or key stress-bearing part of the concrete structure, and the distance between the test point and the benchmark point is less than 100m.

7. The non-contact concrete deformation testing method based on laser ranging technology according to claim 5 is characterized in that: The temperature error does not exceed 0.5°C, the humidity error does not exceed 2%RH, the pressure error does not exceed 0.3hPa, and the atmospheric refractive index calculation error is less than .

8. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3 is characterized in that: In the step of measuring the phase difference between the transmitted signal and the received signal through orthogonal demodulation technology, the orthogonal demodulation technology adopts I / Q dual-channel phase detection and calculates the phase difference through the inverse tangent function with a resolution of 0.001°, corresponding to a distance measurement accuracy of less than 0.3mm.

9. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3 is characterized in that: The diffuse reflection target is a sandblasted aluminum alloy plate with a size of 100×100 mm and a positioning circular hole in the center. It is bonded to the concrete surface with epoxy resin glue.

10. The non-contact concrete deformation testing method based on laser ranging technology according to claim 3, characterized in that: The early warning signals include on-site sound and light alarms, remote SMS notifications and platform pop-up prompts. The early warning signals contain early warning information, which includes the measuring point number, real-time deformation, warning level and occurrence time.

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