A static level measuring system calibration device and calibration method

Abstract

The application discloses a static level measuring system calibration device and method, which comprises a rack, a fixed table and a water tank, wherein the rack is provided with a moving table, the moving table moves up and down through a linear displacement module on the rack, the moving table and the fixed table are respectively provided with a first static level and a second static level, the first static level is connected with the second static level through a flexible pipeline, and the second static level is connected with the water tank through a first pipeline; in the calibration process, the height value of the first static level is obtained through formula (4). Compared with the prior art, the position value of the first static level on the guide rail is automatically corrected through formula (4), the perpendicularity deviation existing in the installation environment is solved, and the calibration accuracy is ensured; the correction method is high in efficiency, and the height of the first static level does not need to be measured by using a laser interferometer after the first static level is moved each time.

Description

Technical Field

[0001] This invention relates to the field of hydrostatic level calibration technology, and in particular to a calibration device and calibration method for a hydrostatic level measurement system. Background Technology

[0002] A hydrostatic level is an instrument that measures the relative height change between two or more points based on the principle of communicating vessels. For example... Figure 2 As shown, in a monitoring site, a measurement system typically consists of two or more hydrostatic levels of the same type. One hydrostatic level serves as the reference point, while the remaining hydrostatic levels serve as monitoring points. It is mainly used for settlement monitoring of infrastructure or buildings such as dams, high-rise buildings, foundation pits, tunnels, and bridges.

[0003] Currently, the calibration technology for hydrostatic levels mainly relies on traditional manual methods or semi-automatic devices. While these methods can meet basic metrological requirements, they still have the following significant shortcomings in practical applications:

[0004] 1. Single-unit calibration mode affects the accuracy of metrological traceability.

[0005] Existing calibration methods typically involve independent calibration of a single hydrostatic level. This "point-to-point" calibration model disrupts the essential characteristic of hydrostatic leveling systems—multiple instruments working collaboratively and conducting interconnected measurements in practical applications. Due to the lack of consideration for the overall system error, the calibration results of a single instrument cannot accurately reflect its comprehensive performance in a connected state, thus affecting the accuracy and reliability of measurement traceability.

[0006] 2. Mechanical installation errors affect calibration accuracy.

[0007] Regarding system error control, existing devices have unavoidable deviations in the mechanical installation process, mainly manifested as verticality deviations, which directly affect the accuracy of calibration. Secondly, vibrations in the environment also affect calibration. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] Based on this, the present invention proposes a calibration device and calibration method for a static level measurement system, in order to solve the problem that the calibration of a single static level is difficult to reflect the actual working conditions of the measurement system and that there are installation errors.

[0010] (II) Technical Solution

[0011] To overcome or at least partially solve the above problems, this invention provides a calibration device for a hydrostatic leveling system, comprising: a frame, a fixed platform, and a water tank. A movable platform is mounted on the frame, and the movable platform moves up and down via a linear displacement module on the frame. A first hydrostatic level and a second hydrostatic level are respectively mounted on the movable platform and the fixed platform. The first hydrostatic level is connected to the second hydrostatic level via a flexible conduit, and the second hydrostatic level is connected to the water tank via a first conduit. A column is mounted on the frame and fixed to a wall.

[0012] Preferably, the column is fixed to the wall surface by expansion bolts.

[0013] Preferably, the linear displacement module is fixed to the column by an L-shaped plate.

[0014] Preferably, the fixing platform is made of cast concrete.

[0015] Preferably, the linear displacement module includes a ball screw, a guide rail, a motor, and a photoelectric encoder. The motor drives the ball screw to rotate, the movable stage is threadedly connected to the ball screw, the movable stage slides up and down along the guide rail, and the photoelectric encoder is connected to the output shaft of the motor.

[0016] The present invention also provides a calibration method including the above-described hydrostatic level measurement system calibration device, comprising the following steps:

[0017] S1: Close the switch on the flexible pipeline on the water tank, move the first static level through the linear displacement module to balance the liquid level of the first static level and the liquid level of the second static level, so that the difference between the readings of the first static level and the second static level is 0, and the height of the first static level is the zero position of the linear displacement module.

[0018] S2: Forward stroke measurement. Move the first static level from zero to full scale. Once the first static level reaches the first calibration point, record its height value L1. At the first calibration point, the reading of the first static level is... The reading of the second static level is The measured value of the instrument being calibrated at the first calibration point. Then, through measured values Calculate the deviation value of the instrument being calibrated at the first calibration point. Following the steps outlined above, the first static level is moved sequentially to the remaining calibration points. At the i-th calibration point, the height of the first static level is Li, and the reading of the first static level is... The reading of the second static level is The measured value of the calibrated instrument at the i-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the i-th calibration point. Where 1≤i≤n, and n is an odd number;

[0019] S3: Reverse travel measurement. After the forward travel measurement is completed, move the first static level upwards a predetermined distance, and then move the first static level from full scale to zero. At the j-th calibration point, the height value of the first static level is Lj, and the reading of the first static level is [value missing]. The reading of the second static level is The measured value of the calibrated instrument at the j-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the j-th calibration point. Where 1≤j≤n, and n is an odd number;

[0020] S3: Calculate the relative error of the indicated value of the instrument being calibrated using formula (1):

[0021] (1)

[0022] Where δmax is the maximum deviation of the instrument being calibrated, and X is the range of the first static level.

[0023] In steps S2 and S3, the height value of the first hydrostatic level is... Calculated using formula (4):

[0024] (4)

[0025] in, This represents the displacement value of the first static level on the guide rail of the linear displacement module. Here, θ is the temperature compensation coefficient, and θ is the angle between the guide rail of the linear displacement module and the vertical direction. This is the difference between the ambient temperature and the reference temperature.

[0026] In step S1, both the first static level and the second static level are liquid surface type static levels.

[0027] Preferably, after step S4, calibration point hysteresis error calibration is further included, wherein the calibration point hysteresis error... The standard is obtained by calculation using formula (2):

[0028] (2)

[0029] Among them, full-range hysteresis error The maximum value of the hysteresis error at the calibration point. .

[0030] Preferably, after step S4, a repeatability calibration is further included, which includes the following steps:

[0031] Repeat the measurement 7 times at half the range of the first static level, with each measurement containing a complete A→B→A motion cycle;

[0032] Calculate repeatability according to formula (3):

[0033] (3)

[0034] Where R is the range of the 7 measurements. =2.704.

[0035] Preferably, θ is obtained through the following steps:

[0036] Install the reflector of the laser interferometer on the moving stage to establish a measurement reference point;

[0037] The absolute vertical direction in the laboratory environment is set as the Z-axis reference;

[0038] Record ambient temperature for thermal expansion compensation;

[0039] The moving stage is driven along the guide rail of the linear displacement module to multiple preset calibration points. The laser interferometer obtains the direction vector of the guide rail by measuring the three-dimensional spatial coordinates of the reflector at each calibration point. ;

[0040] Calculate the unit vector of the guide rail: ;

[0041] Calculate the angle between the guide rail and the Z-axis. :

[0042] in, It is the unit vector along the Z-axis.

[0043] Preferably, when both the first and second static levels in step S1 are differential pressure static levels, the process in step S2... In step S3 .

[0044] (III) Beneficial Effects

[0045] Compared with existing technologies, this invention automatically corrects the position value of the first static level on the guide rail using formula (4), solving the verticality deviation in the installation environment and ensuring calibration accuracy. This correction method is highly efficient and does not require measuring the height of the first static level with a laser interferometer after each movement. Secondly, the measurement path of "forward stroke + additional displacement + reverse stroke" effectively eliminates the influence of the return clearance of the transmission system and improves the accuracy of the reverse stroke measurement. Thirdly, the calibration is performed by using two static levels of the same type to form a measurement system, which allows the calibration method to reproduce the working conditions of the static level and better fit the actual use, further ensuring the accuracy of traceability of measurement values. Fourthly, using the wall as a rigid foundation can effectively isolate the transmission of ground vibration and provide a stable environment for high-precision displacement measurement. Attached Figure Description

[0046] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the drawings:

[0047] Figure 1 This is a schematic diagram of the structure of the present invention;

[0048] Figure 2 This is a schematic diagram of the operation of a conventional hydrostatic leveling system.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. Platform, 2. Fixed platform, 3. Water tank, 4. Moving platform, 5. Linear displacement module, 6. First static level, 7. Second static level, 8. Flexible pipeline, 9. First pipeline, 100. Wall, 11. Column, 12. Expansion bolt, 13. L-shaped plate, 51. Ball screw, 52. Guide rail. Detailed Implementation

[0051] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0052] See attached document Figure 1This embodiment provides a calibration device for a static level measurement system, including: a frame 1, a fixed platform 2, and a water tank 3. A movable platform 4 is mounted on the frame 1, and the movable platform 4 moves up and down via a linear displacement module 5 on the frame 1. A first static level 6 and a second static level 7 are respectively mounted on the movable platform 4 and the fixed platform 2. The first static level 6 is connected to the second static level 7 via a flexible conduit 8, and the second static level 7 is connected to the water tank 3 via a first conduit 9. A column 11 is mounted on the frame 1 and fixed to a wall 100. This invention uses two identical static levels to form a measurement system for calibration. This calibration method can reproduce the working conditions of the static level and ensure the accuracy of measurement traceability. Secondly, the first static level 6 is installed on the moving platform 4 of the linear displacement module 5, which is mounted on the frame 1. The frame 1 is fixed to the wall 100 via the column 11, using the wall 100 as a rigid foundation to effectively isolate ground vibration transmission and provide a stable environment for high-precision displacement measurement. Actual measurements show that this structure can reduce the influence of external vibration to below 0.1 μm. Thirdly, installation on the wall 100 saves floor space, facilitates operator access to the equipment, and makes the layout of connecting pipes simpler and more rational, reducing the impact of hydraulic resistance caused by pipe bends. Fourthly, the concrete wall has a large heat capacity and low temperature drift, providing a long-term stable installation reference for the device and avoiding deformation errors caused by temperature changes in the independent frame 1.

[0053] In another embodiment of the present invention, the column 11 is fixed to the wall 100 by expansion bolts 12.

[0054] In another embodiment of the present invention, the linear displacement module 5 is fixed to the column 11 by the L-shaped plate 13.

[0055] Specifically, column 11 is made of channel steel.

[0056] In another embodiment of the present invention, the fixed platform 2 is made of concrete.

[0057] In another embodiment of the present invention, the first pipeline 9 is a flexible pipeline.

[0058] In another embodiment of the present invention, the linear displacement module 5 includes a ball screw 51, a guide rail 52, a motor, and a photoelectric encoder. The motor drives the ball screw 51 to rotate. The moving stage 4 is threadedly connected to the ball screw 51 and slides up and down along the guide rail 52. The photoelectric encoder is connected to the output shaft of the motor. The linear displacement module 5 uses a high-precision ball screw 51, which can achieve smooth acceleration and deceleration control while ensuring a resolution of 0.5μm, thus avoiding violent fluctuations in the liquid surface.

[0059] As another embodiment of the present invention: a horizontal adjustment mechanism is provided between the moving platform 4 and the first static level 6, and the horizontal adjustment mechanism is used to adjust the levelness of the first static level 6.

[0060] The present invention also provides a calibration method for a hydrostatic leveling system calibration device as described above, comprising the following steps:

[0061] S1: Close the switch of the flexible pipe 8 on the water tank 3, move the first static level 6 through the linear displacement module 5 to balance the liquid level of the first static level 6 and the liquid level of the second static level 7, so that the difference between the readings of the first static level 6 and the second static level 7 is 0, and the height of the first static level 6 is the zero position of the linear displacement module 5.

[0062] S2: Forward stroke measurement. Move the first static level 6 from zero position to full scale. The first static level 6 moves to the first calibration point, and the displacement value L1 of the first static level 6 is recorded. At the first calibration point, the reading of the first static level 6 is... The reading of the second static level 7 is The measured value of the instrument being calibrated at the first calibration point. Then, through measured values Calculate the deviation value of the instrument being calibrated at the first calibration point. Following the steps described above, the first static level 6 is moved sequentially to the remaining calibration points. At the i-th calibration point, the displacement value of the first static level 6 is Li, and the reading of the first static level 6 is... The reading of the second static level 7 is The measured value of the calibrated instrument at the i-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the i-th calibration point. , where 1≤i≤n, and n is an odd number; where the first static level 6 and the second static level 7 constitute the instruments to be calibrated.

[0063] S3: Reverse travel measurement. After the forward travel measurement is completed, move the first static level 6 upwards by 5mm, then move the first static level 6 from full scale to zero. At the j-th calibration point, the displacement value of the first static level 6 is Lj, and the reading of the first static level 6 is [value missing]. The reading of the second static level 7 is The measured value of the calibrated instrument at the j-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the j-th calibration point. Where 1≤j≤n, and n is an odd number;

[0064] S3: Calculate the relative error of the indicated value of the instrument being calibrated using formula (1):

[0065] (1)

[0066] Where δmax is the maximum deviation value of the instrument being calibrated, and X is the range of the first static level 6;

[0067] In steps S2 and S3, the height value of the first static level 6 Calculated using formula (4):

[0068] (4)

[0069] in, This represents the displacement value of the first static level 6 on the guide rail 52 of the linear displacement module 5. Here, θ is the temperature compensation coefficient, and θ is the angle between the guide rail 52 of the linear displacement module 5 and the vertical direction. The difference between the ambient temperature and the reference temperature is used. The displacement value of the first static level 6 on the guide rail 52 and the ambient temperature are collected in real time. Then, the projection calculation and temperature compensation are automatically performed by formula (4), and finally the compensated height value is output.

[0070] To ensure the metrological traceability of calibration results, this invention adopts a geometric compensation method based on vector projection to establish a precise mapping relationship between the motion of the moving stage 4 and the vertical direction, thereby achieving true value traceability of height changes.

[0071] This invention employs spatial vector projection technology to establish a mathematical model of the relationship between the actual motion trajectory of the mobile platform 4 and the ideal vertical direction by accurately measuring the trajectory. The basic principle is as follows:

[0072] Vector projection compensation: The actual displacement vector of the moving stage 4 is projected onto the absolute vertical direction (Z-axis) to eliminate the system error introduced by the installation deviation.

[0073] Least square fitting: Based on multi-point calibration data, the laser interferometer fits the direction vector of guide rail 52.

[0074] Real-time coordinate transformation: Coordinate transformation is performed in real time during the measurement process, and the compensated height value is output.

[0075] The mathematical model expression is:

[0076]

[0077] in For true height variation, This is the actual displacement vector of the moving stage 4 on the guide rail 52. It is the unit vector along the Z-axis.

[0078] θ is obtained through the following steps:

[0079] A reflector of the laser interferometer is installed at the center of the moving stage 4 to establish a measurement reference point; a traceable laser interferometer system is used, with a measurement uncertainty better than 0.1 μm;

[0080] The absolute vertical direction in the laboratory environment is set as the Z-axis reference;

[0081] The driving stage 4 is moved along the guide rail 52 of the linear displacement module 5 to five preset calibration points (0mm, 375mm, 750mm, 1125mm, 1500mm). At each calibration point, the laser interferometer measures the three-dimensional spatial coordinates of the reflector. Repeat the measurement three times at each calibration point and take the average value as the final calibration value.

[0082] The built-in vector fitting algorithm of the laser interferometer:

[0083]

[0084] The laser interferometer uses the least squares method to fit the direction vector.

[0085] Calculate the unit vector of guide rail 52: ;

[0086] Calculate the angle between guide rail 52 and the Z-axis direction. :

[0087] Record ambient temperature and humidity parameters for thermal expansion compensation.

[0088] In step S1, both the first static level 6 and the second static level 7 are liquid surface type static levels.

[0089] As another embodiment of the present invention: after step S4, calibration point hysteresis error calibration is further included, and calibration point hysteresis error... The standard is obtained by calculation using formula (2):

[0090] (2)

[0091] Among them, full-range hysteresis error The maximum value of the hysteresis error at the calibration point. .

[0092] In another embodiment of the present invention: after step S4, a repeatability calibration is further included, which includes the following steps:

[0093] Repeat the measurement 7 times at half the range of the first static level 6, each measurement containing a complete A→B→A motion cycle;

[0094] Calculate repeatability according to formula (3):

[0095] (3)

[0096] Where R is the range of the 7 measurements. =2.704.

[0097] As another embodiment of the present invention: when both the first static level 6 and the second static level 7 are differential pressure static level instruments, in step S2... In step S3 .

[0098] In steps S2 and S3, n is 11, meaning there are 11 calibration points.

[0099] The following steps are included before step S1:

[0100] Environmental equilibration: The two hydrostatic levels should be equilibrated in the laboratory for at least 4 hours.

[0101] Equipment warm-up: The hydrostatic level should be warmed up for 30 minutes before calibration can begin;

[0102] System check: Check the sealing of connecting pipelines to confirm that there are no air bubbles or leaks in the liquid system;

[0103] This invention automatically corrects the position value of the first static level 6 on the guide rail 52 using formula (4), solving the verticality deviation existing in the installation environment and ensuring calibration accuracy. This correction method is highly efficient, eliminating the need to measure the height of the first static level 6 with a laser interferometer after each movement. Secondly, the use of a measurement path of "forward stroke + additional displacement + reverse stroke" effectively eliminates the influence of the return clearance of the transmission system, improving the accuracy of the reverse stroke measurement. Thirdly, the use of two static levels of the same type to form a measurement system for calibration allows the calibration method to reproduce the working conditions of the static level, making it more consistent with actual use and further ensuring the accuracy of traceability of measurement values.

[0104] Considering the economy, applicability, and scalability of the calibration method, the calibration device and calibration method of the present invention are mainly for measurement systems consisting of two hydrostatic levels of the same type; at the same time, based on the consideration of scalability, the calibration device and calibration method of the present invention can also be extended to the calibration and traceability of measurement values ​​of measurement systems consisting of more than two hydrostatic levels of the same type.

[0105] Finally, the method described in this application is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0106] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A calibration device for a hydrostatic leveling instrument measurement system, characterized in that, include: The system comprises a frame, a fixed platform, and a water tank. A movable platform is mounted on the frame, which moves up and down via a linear displacement module on the frame. A first static level and a second static level are mounted on the movable platform and the fixed platform, respectively. The first static level is connected to the second static level via a flexible pipe, and the second static level is connected to the water tank via a first pipe. A column is mounted on the frame and fixed to a wall.

2. The calibration device for the hydrostatic leveling system according to claim 1, characterized in that, The column is fixed to the wall with expansion bolts.

3. The calibration device for the hydrostatic leveling system according to claim 2, characterized in that, The linear displacement module is fixed to the column by an L-shaped plate.

4. The calibration device for the hydrostatic leveling system according to claim 3, characterized in that, The fixed platform is made of concrete.

5. The calibration device for the hydrostatic leveling system according to claim 4, characterized in that, The linear displacement module includes a ball screw, a guide rail, a motor, and a photoelectric encoder. The motor drives the ball screw to rotate. The moving stage is threadedly connected to the ball screw. The moving stage slides up and down along the guide rail. The photoelectric encoder is connected to the output shaft of the motor.

6. A calibration method for a hydrostatic leveling instrument measurement system calibration device comprising any one of claims 1-5, characterized in that, Includes the following steps: S1: Close the switch on the flexible pipeline on the water tank, move the first static level through the linear displacement module to balance the liquid level of the first static level and the liquid level of the second static level, so that the difference between the readings of the first static level and the second static level is 0, and the height of the first static level is the zero position of the linear displacement module. S2: Forward stroke measurement. Move the first static level from zero to full scale. Once the first static level reaches the first calibration point, record its height value L1. At the first calibration point, the reading of the first static level is... The reading of the second static level is The measured value of the instrument being calibrated at the first calibration point. Then, through measured values Calculate the deviation value of the instrument being calibrated at the first calibration point. Following the steps outlined above, the first static level is moved sequentially to the remaining calibration points. At the i-th calibration point, the height of the first static level is Li, and the reading of the first static level is... The reading of the second static level is The measured value of the calibrated instrument at the i-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the i-th calibration point. Where 1≤i≤n, and n is an odd number; S3: Reverse travel measurement. After the forward travel measurement is completed, move the first static level upwards a predetermined distance, and then move the first static level from full scale to zero. At the j-th calibration point, the height value of the first static level is Lj, and the reading of the first static level is [value missing]. The reading of the second static level is The measured value of the calibrated instrument at the j-th calibration point is then... Then, through measured values Calculate the deviation value of the instrument being calibrated at the j-th calibration point. Where 1≤j≤n, and n is an odd number; S3: Calculate the relative error of the indicated value of the instrument being calibrated using formula (1): （1） Where δmax is the maximum deviation of the instrument being calibrated, and X is the range of the first static level. In steps S2 and S3, the height value of the first hydrostatic level is... Calculated using formula (4): （4） in, This represents the displacement value of the first static level on the guide rail of the linear displacement module. Here, θ is the temperature compensation coefficient, and θ is the angle between the guide rail of the linear displacement module and the vertical direction. This is the difference between the ambient temperature and the reference temperature. In step S1, both the first static level and the second static level are liquid surface type static levels.

7. The calibration method according to claim 6, characterized in that, Step S4 is followed by calibration point hysteresis error calibration, wherein the calibration point hysteresis error The standard is obtained by calculation using formula (2): （2） Among them, full-range hysteresis error The maximum value of the hysteresis error at the calibration point. .

8. The calibration method according to claim 7, characterized in that, Following step S4, a repeatability calibration is performed, which includes the following steps: Repeat the measurement 7 times at half the range of the first static level, with each measurement containing a complete A→B→A motion cycle; Calculate repeatability according to formula (3): （3） Where R is the range of the 7 measurements. =2.

704.

9. The calibration method according to claim 8, characterized in that, The θ is obtained through the following steps: Install the reflector of the laser interferometer on the moving stage to establish a measurement reference point; The absolute vertical direction in the laboratory environment is set as the Z-axis reference; Record ambient temperature for thermal expansion compensation; The moving stage is driven along the guide rail of the linear displacement module to multiple preset calibration points. The laser interferometer obtains the direction vector of the guide rail by measuring the three-dimensional spatial coordinates of the reflector at each calibration point. ; Calculate the unit vector of the guide rail: ; Calculate the angle between the guide rail and the Z-axis. : in, It is the unit vector along the Z-axis.

10. The calibration method according to claim 9, characterized in that, When both the first and second static levels in step S1 are differential pressure static levels, in step S2... In step S3 .

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