In-situ calibration device and calibration method for vibration acceleration sensor for bridge monitoring

Abstract

The application discloses a kind of in-situ calibration device and calibration method of vibration acceleration sensor for bridge monitoring.The in-situ calibration device includes portable in-situ calibration vibration table, laser vibration meter, two-axis tiltmeter and photoelectric deflection meter, and the vibration acceleration sensor to be calibrated is installed on the portable in-situ calibration vibration table.The in-situ calibration method using the device includes installing the vibration acceleration sensor to be calibrated, calculating vibration frequency error, calculating vibration displacement indication error and indication repeatability, eliminating error caused by bridge environmental vibration, determining real sensitivity coefficient of the sensor to be calibrated, judging whether the equipment continues to be used, and calibrating sensor frequency.The calibration device can truly reflect the vibration condition of the sensor to be calibrated and the actual displacement of the test table, eliminate the vibration influence caused by the environment itself, improve the calibration accuracy of the equipment through back-to-back calibration, and provide a calibrated environment under vehicle-mounted conditions.

Description

Technical Field

[0001] This invention belongs to the field of vibration calibration technology, specifically relating to an in-situ calibration device and calibration method for a vibration acceleration sensor used in bridge monitoring. Background Technology

[0002] A bridge health monitoring system is a long-term observation system for bridges. The basic function of bridge health monitoring is to monitor and assess the structural condition of bridges, issuing early warning signals when bridges experience abnormal weather, traffic conditions, or severe operational anomalies, thus providing a basis and guidance for bridge maintenance, repair, and management decisions. Bridge health monitoring systems extensively collect and analyze vibration data from bridges using vibration sensors. Therefore, the performance and stability of vibration acceleration sensors greatly determine the overall stability of the bridge health monitoring system. Consequently, vibration acceleration sensors play a crucial role in the entire bridge health monitoring system.

[0003] In bridge health monitoring systems, the normal operation of a bridge, the presence of any abnormal conditions, and the bridge's condition under natural disasters such as earthquakes and hurricanes can all be reflected through vibration data. Vibration sensors, installed long-term at high-frequency vibration points on the bridge, are subjected to rapid temperature changes, strong winds, and high humidity in daily operation. Over time, this can lead to drift and changes in sensitivity coefficients, making calibration of the accelerometers essential.

[0004] Currently, sensor calibration methods both domestically and internationally mainly include control calibration, laboratory calibration, and in-situ calibration. Among these, control calibration is the most intuitive and easiest to implement, but its calibration accuracy is generally low, its error is relatively large, and it requires high-quality control sensors. Laboratory calibration complies with national metrological standards and has high calibration accuracy, but it requires the removal of existing equipment from the health monitoring system, which is time-consuming and labor-intensive, and the transportation process may cause secondary sensor drift. In-situ calibration can be performed on-site, is fast, and has high accuracy, but it lacks good reusable equipment and relevant theoretical support.

[0005] In-situ calibration refers to calibrating equipment in situ within the system while ensuring minimal impact on the structural monitoring system. Because in-situ calibration requires on-site testing, it demands stability of the calibration method and robust data processing. Therefore, it necessitates the development of in-situ calibration equipment and the further development and submission of testing specifications. In-situ calibration was proposed relatively late in the field of bridge structural health monitoring, and prior to this, there was a lack of relevant technical literature and standards. Currently, in-situ calibration primarily utilizes shaking table equipment. However, traditional shaking tables, due to their large size and weight, are difficult to move manually to the vicinity of the bridge for in-situ calibration. While portable shaking tables solve the size and weight issues and achieve portability, the continuous environmental vibration signals present in the bridge system can couple into the standard vibration signals during calibration, significantly affecting the calibration results and preventing in-situ calibration of bridge acceleration sensors. Summary of the Invention

[0006] To address the problems existing in the background technology, the present invention provides an in-situ calibration device and calibration method for a vibration acceleration sensor used in bridge monitoring. The in-situ calibration device is a multi-device combined vibration table formed by combining a laser vibrometer, a small vibration table, and a machine vision measuring instrument. This device can accurately reflect the vibration of the sensor to be calibrated and the actual displacement of the test table surface. The vibration table angle is adjusted by a high-precision dual-axis inclinometer to ensure the excitation direction. Software calculation coupling is used to eliminate the vibration influence caused by the environment itself. At the same time, back-to-back calibration is used to improve the calibration accuracy of the device, and a calibration environment can be provided under vehicle conditions.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] An in-situ calibration device for a vibration acceleration sensor used in bridge monitoring includes a portable in-situ calibration vibration table, a laser vibrometer, a biaxial inclinometer, and a photoelectric deflectometer. The vibration acceleration sensor to be calibrated is mounted on the portable in-situ calibration vibration table.

[0009] A gantry bracket is rigidly connected to the portable in-situ calibration vibration table, and a laser vibration meter is installed above the gantry bracket. The laser vibration meter is installed on the bracket so that it has the same motion characteristics as the vibration table. The laser vibration meter can record the actual displacement of the vibration table and remotely upload it to the calibration test platform for data comparison.

[0010] The biaxial inclinometer is built into a portable in-situ calibration vibration table;

[0011] The photoelectric deflectometer is placed outside the portable in-situ calibration vibration table.

[0012] Furthermore, the laser vibrometer described in this invention is a high-precision laser vibrometer with a vibration measurement accuracy higher than 0.01g and an acceleration resolution higher than 1mg.

[0013] Furthermore, the dual-axis inclinometer described in this invention is a high-precision dual-axis inclinometer with an angle accuracy greater than 0.005°.

[0014] Furthermore, the portable in-situ calibration vibration table of the present invention is provided with four adjustable support threaded columns at the bottom, which fix the vibration table on the horizontal plane.

[0015] Furthermore, the photoelectric deflectometer described in this invention is installed at a stable position 5m to 10m away from the portable in-situ calibration vibration table to measure the vibration of the in-situ calibration vibration table in the horizontal and vertical directions.

[0016] Furthermore, the dual-axis inclinometer described in this invention is fixedly installed at the center of the portable in-situ calibration vibration table for calibrating the angle of the vibration table.

[0017] Furthermore, in the present invention, during calibration, the vibration acceleration sensor to be calibrated is installed in the central vibration zone of the portable in-situ calibration vibration table and tightened to perform calibration.

[0018] Furthermore, the present invention also provides an in-situ calibration method using the above-described device, comprising the following steps:

[0019] (1) Preparation before calibration: First, fix the portable in-situ calibration vibration table on the table or a horizontal plane, and obtain the tilt angle of the vibration table through the dual-axis inclinometer set in the in-situ calibration vibration table. Then, install the vibration sensor to be calibrated onto the vibration table and fix it. Initialize and calibrate the photoelectric deflectometer and the laser vibration meter. The current value is 0, and ensure that the measurement time of the equipment data is the same.

[0020] The portable in-situ calibration vibration table is fixed by four adjustable support threaded columns. The height of the entire vibration table can be adjusted by the matching adjustable nuts. After adjusting the angle of the entire vibration table to be as horizontal as possible, tighten the nuts to ensure the stability of the entire vibration table.

[0021] (2) Vibration frequency error calculation: After installing the calibration device at a horizontal position near the vibration acceleration sensor to be calibrated on the bridge site, select the frequency calibration point according to the actual sensor type as the set vibration frequency value for starting the in-situ calibration vibration table. During vibration, the sensor frequency value is measured by a laser vibrometer. This process is repeated at least 3 times. Before each vibration starts, check the zeroing status of the laser vibrometer and photoelectric deflectometer, and readjust them to zero. Take their arithmetic mean as the arithmetic mean of the frequency measured by the sensor to be calibrated.

[0022] When the sensor is a magnetoelectric accelerometer, the vibration frequency is selected to be between 5 and 10 Hz, and the vibration amplitude is less than 1 g; when the sensor is a piezoelectric accelerometer, the vibration frequency is selected to be between 10 Hz and 20 Hz, and the vibration amplitude is between 1 g and 2 g; the waveforms are all sine waves.

[0023] The sensor vibration frequency measurement indication error σf is calculated by equation (1):

[0024]

[0025] In the formula, σf is the measurement error of the vibration frequency, in Hz; f is the arithmetic mean of the frequencies measured by the sensor to be calibrated, in Hz; r The set vibration frequency value (Hz) for the in-situ calibration vibration table;

[0026] Sensor vibration frequency relative indication error Calculate according to formula (2):

[0027]

[0028] After the vibration table stabilizes, the laser vibration meter is restarted to measure the actual vibration frequency of the sensor. use Substitute f in equations (1) and (2) r The actual measurement error and relative measurement error of the sensor are obtained by calculation:

[0029]

[0030] (3) Calculation of vibration displacement indication error and indication repeatability: During calibration, select no less than 5 calibration points within the range of sensor vibration amplitude measurement, including the upper and lower limits of the range. The points should be roughly evenly distributed. Then, in the vertical direction, calibrate the vibration table in situ and test the vibration amplitude step by step according to the fixed calibration displacement. Read the vibration displacement indication of the vibration acceleration sensor to be calibrated during the vibration process and return process through the laser vibration meter. Repeat this process at least 3 times. Before each start, check the zeroing status of the laser vibration meter and the photoelectric deflectometer and readjust them. Take their arithmetic mean as the arithmetic mean of the amplitude measured by the sensor to be calibrated.

[0031] The error of the sensor vibration amplitude measurement indication is calculated according to formula (5):

[0032]

[0033] In the formula, σd is the measurement error of vibration amplitude, in mm; The arithmetic mean of the amplitude measured by the sensor to be calibrated, in mm; d rThe set vibration amplitude of the in-situ calibration vibration table is in mm; i is the i-th cycle selected in a single vibration cycle.

[0034] The error ratio and repeatability of the indication at each calibration point are calculated according to equations (6) and (7), respectively:

[0035]

[0036] In the formula, dmax is the maximum value of the amplitude reading, in mm; dmin is the minimum value of the amplitude reading, in mm;

[0037] (4) Error elimination caused by bridge environmental vibration: Since the equipment is in the bridge environment during calibration, there is a large amount of fundamental frequency vibration data, which causes the in-situ calibration vibration table itself to have a certain vibration, which will affect the change of vibration amplitude.

[0038] A photoelectric deflectometer was chosen to measure the displacement of the vibration table. However, since the vibration acceleration sensor to be calibrated is rigidly fixed to the vibration table, the displacement reading of the vibration table will be superimposed on the reading of the vibration acceleration sensor to be calibrated. Therefore, the actual error of the sensor's vibration amplitude is shown in equation (8).

[0039]

[0040] In the formula, d s The value in mm represents the amplitude of the vibration in the Y direction generated by the vibration table itself at the current moment, as measured by the photoelectric deflectometer.

[0041] (5) The true sensitivity coefficient of the sensor to be calibrated: Since the amplitude was calculated according to the nominal sensitivity S of the factory at the beginning of calibration, the actual sensitivity s can be obtained according to formula (9) after calibration.

[0042]

[0043] (6) Equipment judgment criteria: According to formulas (1) to (9), the basic data of the vibration acceleration sensor to be calibrated can be obtained. The obtained parameter data is compared with the parameter requirements. If the relative frequency indication error and indication repeatability are ≤2% and the displacement error ratio is ≤3%, the parameter requirements are met, and the next calibration step is carried out. If the parameter data does not meet the parameter requirements, the field sensor should be replaced and the calibrated equipment should be brought back.

[0044] (7) Sensor calibration: The vibration acceleration sensor to be calibrated is reinstalled on the bridge. According to the above formulas, the true vibration frequency F after the field sensor vibration calibration can be obtained. It can be obtained from formula (10).

[0045]

[0046] Where f is the actual acceleration frequency measured after the vibration acceleration sensor to be calibrated is installed on the bridge, and F is the actual vibration frequency of the vibration acceleration sensor to be calibrated.

[0047] In addition, since vibration meters, photoelectric deflectometers and other equipment have certain error values, these errors will cause certain uncertainties in the entire system, which require quantitative analysis.

[0048] Furthermore, to ensure that the overall calibration error is less than 0.02%, the uncertainty caused by each device is calculated as follows:

[0049] Among the angle readings of the biaxial inclinometer, the value in the horizontal X direction is θ. x The value in the horizontal Y direction is θ Y Since the uncertainty introduced by the unevenness of the equipment is θ, the actual horizontal deviation angle θ is obtained from equation (11).

[0050]

[0051] The maximum permissible error of the biaxial inclinometer is ±0.001°, which is uniformly distributed. The uncertainty introduced by the biaxial inclinometer can be obtained from equation (12).

[0052] uθ=θ±0.001° (12)

[0053] The actual vertical displacement ud of the vibration table can be obtained from equation (13).

[0054]

[0055] The uncertainty component d introduced by the laser vibration meter is 0.01%, then according to equations (3) and (4), we can obtain:

[0056] The accuracy of the photoelectric deflectometer is r = 0.01 mm, and the uncertainty uds introduced by the photoelectric deflectometer is obtained according to equation (14):

[0057] ud s =d s ±0.01mm (14).

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The calibration device and method of the present invention can be used in the in-situ calibration of the acceleration sensor in the bridge health monitoring system. After calibration, the calibration error is less than 0.02% after introducing the uncertainty caused by the equipment.

[0060] (2) Compared with other portable calibration platforms, the present invention eliminates the error caused by bridge vibration and greatly improves the accuracy of on-site calibration.

[0061] (3) The in-situ calibration device and calibration method of the present invention can eliminate the vibration effect caused by the environment itself, and improve the calibration accuracy of the equipment by back-to-back calibration, and can provide a calibration environment under vehicle conditions. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the in-situ calibration device described in this invention.

[0063] Figure 1 The following items are labeled as follows: 1. Laser vibration meter, 2. Gantry bracket, 3. Vibration acceleration sensor to be calibrated, 4. Portable in-situ vibration calibration platform, 5. Dual-axis inclinometer, 6. Photoelectric deflectometer, 7. Adjustable support threaded column. Detailed Implementation

[0064] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0065] An in-situ calibration device for a vibration acceleration sensor used in bridge monitoring includes a portable in-situ calibration vibration table 4, a laser vibration meter 1, a biaxial inclinometer 5, and a photoelectric deflectometer 6. The vibration acceleration sensor 3 to be calibrated is mounted on the portable in-situ calibration vibration table 4.

[0066] A gantry bracket 2 is rigidly connected to the portable in-situ calibration vibration table, and a laser vibration meter 1 is installed on the top of the gantry bracket. The laser vibration meter is installed on the bracket so that it has the same motion characteristics as the vibration table. The laser vibration meter can record the actual displacement of the vibration table and remotely upload it to the calibration test platform for data comparison.

[0067] The biaxial inclinometer is built into a portable in-situ calibration vibration table;

[0068] The photoelectric deflectometer is placed outside the portable in-situ calibration vibration table.

[0069] Furthermore, the laser vibrometer described in this invention is a high-precision laser vibrometer with a vibration measurement accuracy higher than 0.01g and an acceleration resolution higher than 1mg.

[0070] Furthermore, the dual-axis inclinometer described in this invention is a high-precision dual-axis inclinometer with an angle accuracy greater than 0.005°.

[0071] Furthermore, the portable in-situ calibration vibration table of the present invention is provided with four adjustable support threaded columns 7 at the bottom, which fix the vibration table on the horizontal plane.

[0072] Furthermore, the photoelectric deflectometer described in this invention is installed at a stable position 5m to 10m away from the portable in-situ calibration vibration table to measure the vibration of the in-situ calibration vibration table in the horizontal and vertical directions.

[0073] Furthermore, the dual-axis inclinometer described in this invention is fixedly installed at the center of the portable in-situ calibration vibration table for calibrating the angle of the vibration table.

[0074] Furthermore, in the present invention, during calibration, the vibration acceleration sensor to be calibrated is installed in the central vibration zone of the portable in-situ calibration vibration table and tightened to perform calibration.

[0075] Furthermore, the present invention also provides an in-situ calibration method using the above-described device, comprising the following steps:

[0076] (1) Preparation before calibration: First, fix the portable in-situ calibration vibration table on the table or a horizontal plane, and obtain the tilt angle of the vibration table through the dual-axis inclinometer set in the in-situ calibration vibration table. Then, install the vibration sensor to be calibrated onto the vibration table and fix it. Initialize and calibrate the photoelectric deflectometer and the laser vibration meter. The current value is 0, and ensure that the measurement time of the equipment data is the same.

[0077] The portable in-situ calibration vibration table is fixed by four adjustable support threaded columns. The height of the entire vibration table can be adjusted by the matching adjustable nuts. After adjusting the angle of the entire vibration table to be as horizontal as possible, tighten the nuts to ensure the stability of the entire vibration table.

[0078] (2) Vibration frequency error calculation: After installing the calibration device at a horizontal position near the vibration acceleration sensor to be calibrated on the bridge site, select the frequency calibration point according to the actual sensor type as the set vibration frequency value for starting the in-situ calibration vibration table. During vibration, the sensor frequency value is measured by a laser vibrometer. This process is repeated at least 3 times. Before each vibration starts, check the zeroing status of the laser vibrometer and photoelectric deflectometer, and readjust them to zero. Take their arithmetic mean as the arithmetic mean of the frequency measured by the sensor to be calibrated.

[0079] When the sensor is a magnetoelectric accelerometer, the vibration frequency is selected to be between 5 and 10 Hz, and the vibration amplitude is less than 1 g; when the sensor is a piezoelectric accelerometer, the vibration frequency is selected to be between 10 Hz and 20 Hz, and the vibration amplitude is between 1 g and 2 g; the waveforms are all sine waves.

[0080] The sensor vibration frequency measurement indication error σf is calculated by equation (1):

[0081]

[0082] In the formula, σf is the measurement error of the vibration frequency, in Hz; f is the arithmetic mean of the frequencies measured by the sensor to be calibrated, in Hz; r The set vibration frequency value (Hz) for the in-situ calibration vibration table;

[0083] Sensor vibration frequency relative indication error Calculate according to formula (2):

[0084]

[0085] After the vibration table stabilizes, the laser vibration meter is restarted to measure the actual vibration frequency of the sensor. use Substitute f in equations (1) and (2) r The actual measurement error and relative measurement error of the sensor are obtained by calculation:

[0086]

[0087] (3) Calculation of vibration displacement indication error and indication repeatability: During calibration, select no less than 5 calibration points within the range of sensor vibration amplitude measurement, including the upper and lower limits of the range. The points should be roughly evenly distributed. Then, in the vertical direction, calibrate the vibration table in situ and test the vibration amplitude step by step according to the fixed calibration displacement. Read the vibration displacement indication of the vibration acceleration sensor to be calibrated during the vibration process and return process through the laser vibration meter. Repeat this process at least 3 times. Before each start, check the zeroing status of the laser vibration meter and the photoelectric deflectometer and readjust them. Take their arithmetic mean as the arithmetic mean of the amplitude measured by the sensor to be calibrated.

[0088] The error of the sensor vibration amplitude measurement indication is calculated according to formula (5):

[0089]

[0090] In the formula, σd is the measurement error of vibration amplitude, in mm; The arithmetic mean of the amplitude measured by the sensor to be calibrated, in mm; d r The set vibration amplitude of the in-situ calibration vibration table is in mm; i is the i-th cycle selected in a single vibration cycle.

[0091] The error ratio and repeatability of the indication at each calibration point are calculated according to equations (6) and (7), respectively:

[0092]

[0093] In the formula, dmax is the maximum value of the amplitude reading, in mm; dmin is the minimum value of the amplitude reading, in mm;

[0094] (4) Error elimination caused by bridge environmental vibration: Since the equipment is in the bridge environment during calibration, there is a large amount of fundamental frequency vibration data, which causes the in-situ calibration vibration table itself to have a certain vibration, which will affect the change of vibration amplitude.

[0095] A photoelectric deflectometer was chosen to measure the displacement of the vibration table. However, since the vibration acceleration sensor to be calibrated is rigidly fixed to the vibration table, the displacement reading of the vibration table will be superimposed on the reading of the vibration acceleration sensor to be calibrated. Therefore, the actual error of the sensor's vibration amplitude is shown in equation (8).

[0096]

[0097] In the formula, d s The value in mm represents the amplitude of the vibration in the Y direction generated by the vibration table itself at the current moment, as measured by the photoelectric deflectometer.

[0098] (5) The true sensitivity coefficient of the sensor to be calibrated: Since the amplitude was calculated according to the nominal sensitivity S of the factory at the beginning of calibration, the actual sensitivity s can be obtained according to formula (9) after calibration.

[0099]

[0100] (6) Equipment judgment criteria: According to formulas (1) to (9), the basic data of the vibration acceleration sensor to be calibrated can be obtained. The obtained parameter data is compared with the parameter requirements. If the relative frequency indication error and indication repeatability are ≤2% and the displacement error ratio is ≤3%, the parameter requirements are met, and the next calibration step is carried out. If the parameter data does not meet the parameter requirements, the field sensor should be replaced and the calibrated equipment should be brought back.

[0101] (7) Sensor calibration: The vibration acceleration sensor to be calibrated is reinstalled on the bridge. According to the above formulas, the true vibration frequency F after the field sensor vibration calibration can be obtained. It can be obtained from formula (10).

[0102]

[0103] Where f is the actual acceleration frequency measured after the vibration acceleration sensor to be calibrated is installed on the bridge, and F is the actual vibration frequency of the vibration acceleration sensor to be calibrated.

[0104] In addition, since vibration meters, photoelectric deflectometers and other equipment have certain error values, these errors will cause certain uncertainties in the entire system, which require quantitative analysis.

[0105] Furthermore, to ensure that the overall calibration error is less than 0.02%, the uncertainty caused by each device is calculated as follows:

[0106] Among the angle readings of the biaxial inclinometer, the value in the horizontal X direction is θ. x The value in the horizontal Y direction is θ YSince the uncertainty introduced by the unevenness of the equipment is θ, the actual horizontal deviation angle θ is obtained from equation (11).

[0107]

[0108] The maximum permissible error of the biaxial inclinometer is ±0.001°, which is uniformly distributed. The uncertainty introduced by the biaxial inclinometer can be obtained from equation (12).

[0109] uθ=θ±0.001° (12)

[0110] The actual vertical displacement ud of the vibration table can be obtained from equation (13).

[0111]

[0112] The uncertainty component d introduced by the laser vibration meter is 0.01%, then according to equations (3) and (4), we can obtain:

[0113] The accuracy of the photoelectric deflectometer is r = 0.01 mm, and the uncertainty uds introduced by the photoelectric deflectometer is obtained according to equation (14):

[0114] ud s =d s ±0.01mm (14).

[0115] Example

[0116] An in-situ calibration device for a vibration acceleration sensor used in bridge monitoring includes a portable in-situ calibration vibration table, a laser vibrometer, a biaxial inclinometer, and a photoelectric deflectometer. The vibration acceleration sensor to be calibrated is mounted on the portable in-situ calibration vibration table.

[0117] A 40cm high and 20cm wide gantry frame is rigidly connected to the portable in-situ calibration vibration table, and a laser vibrometer is installed on top of the gantry frame. The laser vibrometer is mounted on the frame so that it has the same motion characteristics as the vibration table. The laser vibrometer can record the actual displacement of the vibration table and remotely upload the data to the calibration test platform for comparison. The laser vibrometer is a high-precision laser vibrometer with a vibration measurement accuracy higher than 0.01g and an acceleration resolution higher than 1mg.

[0118] The biaxial inclinometer is built into the portable in-situ calibration vibration table. The biaxial inclinometer is a high-precision biaxial inclinometer with an angle accuracy greater than 0.005°. The biaxial inclinometer is fixedly installed at the center of the portable in-situ calibration vibration table and is used to calibrate the angle of the vibration table.

[0119] The photoelectric deflectometer is placed outside the portable in-situ calibration vibration table. The photoelectric deflectometer is installed at a stable position 5m away from the portable in-situ calibration vibration table and is used to measure the vibration of the in-situ calibration vibration table in the horizontal and vertical directions.

[0120] The portable in-situ calibration vibration table is equipped with four adjustable support threaded columns at the bottom, which fix the vibration table on the horizontal plane.

[0121] In this invention, the vibration acceleration sensor to be calibrated is installed in the central vibration zone of the portable in-situ calibration vibration table and tightened during calibration.

[0122] An in-situ calibration method using the above-mentioned device includes the following steps:

[0123] (1) Preparation before calibration: First, fix the portable in-situ calibration vibration table on the table or a horizontal plane, and obtain the tilt angle of the vibration table through the dual-axis inclinometer set in the in-situ calibration vibration table. Then, install the vibration sensor to be calibrated onto the vibration table and fix it. Initialize and calibrate the photoelectric deflectometer and the laser vibration meter. The current value is 0, and ensure that the measurement time of the equipment data is the same.

[0124] The portable in-situ calibration vibration table is fixed by four adjustable support threaded columns. The height of the entire vibration table can be adjusted by the matching adjustable nuts. After adjusting the angle of the entire vibration table to be as horizontal as possible, tighten the nuts to ensure the stability of the entire vibration table.

[0125] (2) Vibration frequency error calculation: After installing the calibration device at a horizontal position near the vibration acceleration sensor to be calibrated on the bridge site, select the frequency calibration point according to the actual sensor type as the set vibration frequency value for starting the in-situ calibration vibration table. During vibration, the sensor frequency value is measured by a laser vibration meter. This process is repeated 3 times. Before each vibration starts, check the zeroing status of the laser vibration meter and photoelectric deflectometer, and readjust them to zero. Take their arithmetic mean as the arithmetic mean of the frequency measured by the sensor to be calibrated.

[0126] When the sensor is a magnetoelectric accelerometer, the vibration frequency is selected to be between 5 and 10 Hz, the vibration amplitude is less than 1g, and the waveform is a sine wave.

[0127] The sensor vibration frequency measurement indication error σf is calculated by equation (1):

[0128]

[0129] In the formula, σf is the measurement error of the vibration frequency, in Hz; f is the arithmetic mean of the frequencies measured by the sensor to be calibrated, in Hz; rThe set vibration frequency value (Hz) for the in-situ calibration vibration table;

[0130] Sensor vibration frequency relative indication error Calculate according to formula (2):

[0131]

[0132] After the vibration table stabilizes, the laser vibration meter is restarted to measure the actual vibration frequency of the sensor. use Substitute f in equations (1) and (2) r The actual measurement error and relative measurement error of the sensor are obtained by calculation:

[0133]

[0134] (3) Calculation of vibration displacement indication error and indication repeatability: During calibration, select 5 calibration points within the range of sensor vibration amplitude measurement, including the upper and lower limits of the range. The points should be roughly evenly distributed. Then, in the vertical direction, calibrate the vibration table in situ and test the vibration amplitude step by step according to the fixed calibration displacement. Read the vibration displacement indication of the vibration acceleration sensor to be calibrated during the vibration process and return process through the laser vibration meter. Repeat this process 3 times. Before each start, check the zeroing status of the laser vibration meter and the photoelectric deflectometer and readjust them to zero. Take their arithmetic mean as the arithmetic mean of the amplitude measured by the sensor to be calibrated.

[0135] The error of the sensor vibration amplitude measurement indication is calculated according to formula (5):

[0136]

[0137] In the formula, σd is the measurement error of vibration amplitude, in mm; The arithmetic mean of the amplitude measured by the sensor to be calibrated, in mm; d r The set vibration amplitude of the in-situ calibration vibration table is in mm; i is the i-th cycle selected in a single vibration cycle.

[0138] The error ratio and repeatability of the indication at each calibration point are calculated according to equations (6) and (7), respectively:

[0139]

[0140] In the formula, dmax is the maximum value of the amplitude reading, in mm; dmin is the minimum value of the amplitude reading, in mm;

[0141] (4) Error elimination caused by bridge environmental vibration: Since the equipment is in the bridge environment during calibration, there is a large amount of fundamental frequency vibration data, which causes the in-situ calibration vibration table itself to have a certain vibration, which will affect the change of vibration amplitude.

[0142] A photoelectric deflectometer was chosen to measure the displacement of the vibration table. However, since the vibration acceleration sensor to be calibrated is rigidly fixed to the vibration table, the displacement reading of the vibration table will be superimposed on the reading of the vibration acceleration sensor to be calibrated. Therefore, the actual error of the sensor's vibration amplitude is shown in equation (8).

[0143]

[0144] In the formula, d s The value in mm represents the amplitude of the vibration in the Y direction generated by the vibration table itself at the current moment, as measured by the photoelectric deflectometer.

[0145] (5) The true sensitivity coefficient of the sensor to be calibrated: Since the amplitude was calculated according to the nominal sensitivity S of the factory at the beginning of calibration, the actual sensitivity s can be obtained according to formula (9) after calibration.

[0146]

[0147] (6) Equipment judgment criteria: According to formulas (1) to (9), the basic data of the vibration acceleration sensor to be calibrated can be obtained. The obtained parameter data is compared with the parameter requirements. If the relative frequency indication error and indication repeatability are ≤2% and the displacement error ratio is ≤3%, the parameter requirements are met, and the next calibration step is carried out. If the parameter data does not meet the parameter requirements, the field sensor should be replaced and the calibrated equipment should be brought back.

[0148] (7) Sensor calibration: The vibration acceleration sensor to be calibrated is reinstalled on the bridge. According to the above formulas, the true vibration frequency F after the field sensor vibration calibration can be obtained. It can be obtained from formula (10).

[0149]

[0150] Where f is the actual acceleration frequency measured after the vibration acceleration sensor to be calibrated is installed on the bridge, and F is the actual vibration frequency of the vibration acceleration sensor to be calibrated.

[0151] In addition, since vibration meters, photoelectric deflectometers and other equipment have certain error values, these errors will cause certain uncertainties in the entire system, which require quantitative analysis.

[0152] Furthermore, to ensure that the overall calibration error is less than 0.02%, the uncertainty caused by each device is calculated as follows:

[0153] Among the angle readings of the biaxial inclinometer, the value in the horizontal X direction is θ. x The value in the horizontal Y direction is θ Y Since the uncertainty introduced by the unevenness of the equipment is θ, the actual horizontal deviation angle θ is obtained from equation (11).

[0154]

[0155] The maximum permissible error of the biaxial inclinometer is ±0.001°, which is uniformly distributed. The uncertainty introduced by the biaxial inclinometer can be obtained from equation (12).

[0156] uθ=θ±0.001° (12)

[0157] The actual vertical displacement ud of the vibration table can be obtained from equation (13).

[0158]

[0159] The uncertainty component d introduced by the laser vibration meter is 0.01%, then according to equations (3) and (4), we can obtain:

[0160] The accuracy of the photoelectric deflectometer is r = 0.01 mm, and the uncertainty uds introduced by the photoelectric deflectometer is obtained according to equation (14):

[0161] ud s =d s ±0.01mm (14).

Claims

1. An in-situ calibration method for a vibration acceleration sensor used in bridge monitoring, characterized in that, Includes the following steps: (1) Preparation before calibration: First, fix the portable in-situ calibration vibration table on a horizontal plane, and obtain the tilt angle of the vibration table through the dual-axis inclinometer set in the in-situ calibration vibration table. Then, install the vibration sensor to be calibrated onto the vibration table and fix it. Initialize and calibrate the photoelectric deflectometer and the laser vibration meter. The current value is 0, and ensure that the measurement time of the equipment data is the same. (2) Vibration frequency error calculation: After installing the calibration device at a horizontal position near the vibration acceleration sensor to be calibrated on the bridge site, select the frequency calibration point according to the actual sensor type as the set vibration frequency value for starting the in-situ calibration vibration table. During vibration, the sensor frequency value is measured by a laser vibration meter. This process is repeated at least 3 times. Before each vibration starts, check the zeroing status of the laser vibration meter and the photoelectric deflectometer, and readjust them to zero. Take their arithmetic mean as the arithmetic mean of the frequency measured by the sensor to be calibrated. Sensor vibration frequency measurement indication error Calculated using equation (1): （1） In the formula, The measurement error for vibration frequency is expressed in Hz. The frequency is the arithmetic mean of the frequencies measured by the sensor to be calibrated, in Hz; The set vibration frequency value (Hz) for the in-situ calibration vibration table; Sensor vibration frequency relative indication error Calculate according to formula (2): （2） After the vibration table stabilizes, the laser vibration meter is restarted to measure the actual vibration frequency of the sensor. ,use Substitute equations (1) and (2) The actual measurement error and relative measurement error of the sensor are obtained by calculation: （3） （4） (3) Calculation of vibration displacement indication error and indication repeatability: During calibration, select no less than 5 calibration points within the range of sensor vibration amplitude measurement, including the upper and lower limits of the range, and distribute the points evenly; then, in the vertical direction, calibrate the vibration table in situ and test the vibration amplitude step by step according to the fixed calibration displacement amount. Read the vibration displacement indication of the vibration acceleration sensor to be calibrated during the vibration process and return process through the laser vibration meter; repeat this process at least 3 times. Before each start, check the zeroing status of the laser vibration meter and the photoelectric deflectometer, and readjust to zero. Take their arithmetic mean as the arithmetic mean of the amplitude measured by the sensor to be calibrated. The error in the sensor vibration amplitude measurement is calculated according to formula (5): （5） In the formula, The measurement error for vibration amplitude is expressed in mm. The amplitude is the arithmetic mean measured by the sensor to be calibrated, in mm; The set vibration amplitude of the in-situ calibration vibration table is in mm; i is the i-th cycle selected in a single vibration cycle. The error ratio and repeatability of the indication at each calibration point are calculated according to equations (6) and (7), respectively: （6） （7） In the formula, dmax is the maximum value of the amplitude reading, in mm; dmin is the minimum value of the amplitude reading, in mm; (4) Error elimination caused by bridge environmental vibration: A photoelectric deflectometer is selected to measure the displacement of the vibration table. The displacement value of the vibration table is superimposed on the value of the vibration acceleration sensor to be calibrated. The actual error of the sensor vibration amplitude is shown in equation (8). （8） In the formula, The value in mm represents the amplitude of the vibration in the Y direction generated by the vibration table itself at the current moment, as measured by the photoelectric deflectometer. (5) The true sensitivity coefficient of the sensor to be calibrated: Since the amplitude was calculated according to the nominal sensitivity S of the factory at the beginning of calibration, the actual sensitivity s is obtained according to formula (9) after calibration. （9） (6) Equipment judgment criteria: According to formulas (1) to (9), obtain the basic data of the vibration acceleration sensor to be calibrated. Compare the obtained parameter data with the parameter requirements. If the frequency relative indication error and indication repeatability are ≤2% and the displacement error ratio is ≤3%, the parameter requirements are met, and the next calibration step is carried out. If the parameter data does not meet the parameter requirements, the field sensor should be replaced and the calibrated equipment should be brought back. (7) Sensor calibration: The vibration acceleration sensor to be calibrated is reinstalled on the bridge, and the true vibration frequency F after field sensor vibration calibration is obtained according to the above formulas as shown in formula (10). （10） Where f is the actual acceleration frequency measured after the vibration acceleration sensor to be calibrated was installed on the bridge, and F is the actual vibration frequency of the vibration acceleration sensor to be calibrated. The in-situ calibration device used includes a portable in-situ calibration vibration table (4), a laser vibrometer (1), a biaxial inclinometer (5) and a photoelectric deflectometer (6). The vibration acceleration sensor (3) to be calibrated is installed on the portable in-situ calibration vibration table (4). A gantry bracket (2) is rigidly connected to the portable in-situ calibration vibration table (4), and a laser vibration meter (1) is installed above the gantry bracket (2). The biaxial inclinometer (5) is built into a portable in-situ calibration vibration table (4); The photoelectric deflectometer (6) is placed outside the portable in-situ calibration vibration table (4).

2. The in-situ calibration method according to claim 1, characterized in that, The laser vibrometer is a high-precision laser vibrometer with a vibration measurement accuracy higher than 0.01g and an acceleration resolution higher than 1mg. The dual-axis inclinometer is a high-precision dual-axis inclinometer with an angle accuracy greater than 0.005°.

3. The in-situ calibration method according to claim 1, characterized in that, The portable in-situ calibration vibration table has four adjustable support threaded columns at the bottom, which fix the vibration table on a horizontal surface.

4. The in-situ calibration method according to claim 1, characterized in that, The photoelectric deflectometer is installed at a stable position 5m to 10m away from the portable in-situ calibration vibration table.

5. The in-situ calibration method according to claim 1, characterized in that, The biaxial inclinometer is fixedly installed at the center of the portable in-situ calibration vibration table.

6. The in-situ calibration method according to claim 1, characterized in that, The vibration acceleration sensor to be calibrated is installed in the central vibration zone of the portable in-situ calibration vibration table and tightened.

7. The in-situ calibration method according to claim 1, characterized in that, The portable in-situ calibration vibration table described in step (1) is fixed by four adjustable support threaded columns. The height of the entire vibration table is adjusted by the matching adjustable nuts. After adjusting the angle of the entire vibration table to be as horizontal as possible, the nuts are tightened to ensure the stability of the entire vibration table.

8. The in-situ calibration method according to claim 1, characterized in that, When the actual sensor in step (2) is a magnetoelectric accelerometer, the vibration frequency is selected to be between 5 and 10 Hz and the vibration amplitude is less than 1 g. The sensor is a piezoelectric accelerometer with a vibration frequency of 10Hz to 20Hz and a vibration amplitude of 1g to 2g; the waveforms are all sine waves.

9. The in-situ calibration method according to claim 1, characterized in that, To ensure that the overall calibration error is less than 0.02%, the uncertainties caused by each device are calculated as follows: Among the angle readings of the biaxial inclinometer, the reading in the horizontal X direction is... The value in the horizontal Y direction is The uncertainty introduced by the unevenness of the equipment is So the actual horizontal offset angle The value is obtained from equation (11). （11） The maximum permissible error of the biaxial inclinometer is ±0.001°, which is uniformly distributed. The uncertainty introduced by the biaxial inclinometer is obtained according to equation (12). （12） The actual vertical displacement ud of the vibration table is obtained according to equation (13). （13） The uncertainty component d introduced by the laser vibration meter is 0.01%, which can be obtained according to equations (3) and (4); The accuracy of the photoelectric deflectometer is r =0.01 mm, the uncertainty ud introduced by the photoelectric deflectometer s Then, according to equation (14), we get: （14）。

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