A method for obtaining the absolute calibration value and absolute elevation of an absolute hydrostatic level.

Abstract

A method for obtaining the absolute calibration value and absolute elevation of an absolute static level, relating to the field of measurement technology. The method involves obtaining the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target sphere. k When calibrating the absolute hydrostatic level to be calibrated, the hydrostatic level reading R at this liquid level height is obtained. k ; Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated k This will give you the absolute calibration value A for each absolute hydrostatic level to be calibrated. k A k =MD k -W k -R k Multiple absolute hydrostatic levels to be calibrated are connected to form an absolute hydrostatic leveling system, and the absolute hydrostatic level readings R are obtained during the measurement of the absolute hydrostatic levels to be calibrated. i_k The absolute elevation of the absolute hydrostatic level is calculated using the following formula: H i_k =A k +R i_k , where H i_k This indicates the absolute elevation of the static level to be measured. This application can directly calculate the absolute elevation of the current point without obtaining the elevation through elevation transfer, making the calculation result of the absolute elevation more accurate.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, specifically to a method for obtaining the absolute calibration value and absolute elevation of an absolute hydrostatic level. Background Technology

[0002] Currently, tunnel elevation measurement mainly relies on geometric leveling, with common methods including leveling instruments and laser trackers. When measuring the elevation of tunnel network points, the elevation of the current network point is first calculated, and then the elevation of the next network point is calculated using the elevation of the current network point. That is, elevation is transferred through relay stations. However, as the number of relay stations and the leveling distance increase, the error also accumulates.

[0003] To reduce errors, foreign countries have proposed a linear tunnel benchmark method based on lasers and tension wires, which can simultaneously improve the accuracy of tunnel control networks in both horizontal and vertical directions. However, this method is very difficult to apply when dealing with ring-shaped tunnels because the multi-segment overlap of the tension wires and laser collimation system is difficult, and it involves the adjustment of optical components, deflection and overlap of optical paths, which can easily introduce unknown errors. Summary of the Invention

[0004] The main technical problem solved by this invention is that the excessive number of overlapping geometric leveling stations leads to large errors in elevation calculation results.

[0005] According to the first aspect, one embodiment provides a method for obtaining the absolute calibration value of an absolute hydrostatic level, comprising:

[0006] Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k ;

[0007] Obtain the absolute hydrostatic level reading R during calibration. k ;

[0008] Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated k ;

[0009] The absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula:

[0010] A k =MD k -R k -W k

[0011] Among them, A k This indicates the absolute calibration value of the absolute hydrostatic level to be calibrated.

[0012] In one embodiment, the distance MD from the bottom surface of the lower bowl of the absolute hydrostatic level to be calibrated to the center of the top target ball is obtained.k ,include:

[0013] Obtain the measurement point on the bottom surface of the lower bowl of the absolute static level to be calibrated;

[0014] A coordinate system is fitted based on the measurement points;

[0015] Obtain the target ball boundary coordinates in the coordinate system;

[0016] Fit the target ball center coordinates based on the target ball boundary coordinates;

[0017] The distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball is determined based on the coordinates of the target ball's center. k .

[0018] In one embodiment, the absolute hydrostatic level reading R is obtained during the calibration of the absolute hydrostatic level to be calibrated. k ,include:

[0019] During the calibration of the absolute static level, the liquid level inside the absolute static level is within the measurement range of the absolute static level.

[0020] After the liquid inside the absolute hydrostatic level to be calibrated has stabilized, the reading R of the absolute hydrostatic level to be calibrated is obtained. k .

[0021] In one embodiment, the liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include:

[0022] The distance the multimeter needle moves from the design reference surface of the lower bowl of the absolute hydrostatic level to be calibrated to the liquid surface in contact with the liquid inside the lower bowl of the absolute hydrostatic level to be calibrated.

[0023] Based on the distance from the design reference plane of the lower bowl of the absolute hydrostatic level to be calibrated to the bottom surface of the lower bowl, and the movement distance of the multimeter needle, determine the liquid depth W inside the absolute hydrostatic level to be calibrated. k .

[0024] In one embodiment, the movement distance of the multimeter needle is determined by a coordinate measuring machine or a displacement stage.

[0025] In one embodiment, the liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include:

[0026] The first liquid depth, determined by the coaxial displacement sensor at a first predetermined distance from the middle depth of the liquid, is obtained.

[0027] The second liquid depth, determined by the coaxial displacement sensor at a second predetermined distance from the middle depth of the liquid, is obtained.

[0028] A third liquid depth is obtained by a coaxial displacement sensor at a third predetermined distance from the middle depth of the liquid; wherein the first predetermined distance is less than the second predetermined distance, the second predetermined distance is less than the third predetermined distance; and the difference between the second predetermined distance and the first predetermined distance is equal to the difference between the third predetermined distance and the second predetermined distance.

[0029] The liquid depth W inside the absolute hydrostatic level to be calibrated is determined based on the first liquid depth, the second liquid depth, and the third liquid depth. k .

[0030] In one embodiment, the liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include:

[0031] The first distance from the bottom surface of the lower bowl of the absolute static level to the probe of the coaxial displacement sensor is determined by the coaxial displacement sensor when no liquid is added to the absolute static level to be calibrated.

[0032] The second distance from the liquid level in the lower bowl of the absolute static level to the probe of the coaxial displacement sensor is determined by the coaxial displacement sensor when liquid is added to the absolute static level to be calibrated.

[0033] The liquid depth W inside the absolute hydrostatic level to be calibrated is determined based on the first distance and the second distance. k .

[0034] In one embodiment, the liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include:

[0035] When the liquid level in the lower bowl of the absolute static level to be calibrated is less than the set value of the measurement range of the liquid in the absolute static level to be calibrated, a standard heightening pad is placed in the lower bowl of the absolute static level to be calibrated, so that the liquid depth is within the range of the coaxial displacement sensor and the liquid level is within the range of the absolute static level to be calibrated.

[0036] According to the second aspect, one embodiment provides a method for obtaining the absolute elevation of an absolute hydrostatic level, comprising:

[0037] Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k ;

[0038] Obtain the absolute hydrostatic level reading R during calibration. k ;

[0039] Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated k ;

[0040] The absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula:

[0041] A k =MD k -R k -W k

[0042] Among them, A k This represents the absolute calibration value of the absolute hydrostatic level to be calibrated;

[0043] Obtain the absolute static level reading R during the measurement of the absolute static level to be calibrated. i_k ;

[0044] The absolute elevation of the absolute hydrostatic level to be calibrated is calculated using the following formula:

[0045] H i_k =A k +R i_k

[0046] Among them, H i_k This indicates the absolute elevation of the static level to be calibrated.

[0047] According to the above embodiment, a method for obtaining the absolute calibration value and absolute elevation of an absolute static level can be used to directly calculate the absolute calibration value of the absolute static level by obtaining the distance from the bottom surface of the lower bowl of the absolute static level to the center of the top target ball, the absolute static level reading during calibration, and the liquid depth inside the absolute static level. Furthermore, by obtaining the absolute static level reading during measurement, the absolute elevation of the current point can be directly calculated. This eliminates the need for elevation transfer in the elevation calculation, resulting in more accurate absolute elevation calculations. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a non-contact hydrostatic level.

[0049] Figure 2 This is a schematic diagram of an absolute static leveling system in one embodiment;

[0050] Figure 3 This is a schematic diagram of absolute elevation calculation using an absolute hydrostatic level in one embodiment. Figure 1 ;

[0051] Figure 4 This is a schematic diagram of absolute elevation calculation using an absolute hydrostatic level in one embodiment. Figure 2 ;

[0052] Figure 5 A flowchart of a method for obtaining the absolute calibration value of an absolute hydrostatic level in one embodiment. Figure 1 ;

[0053] Figure 6 A flowchart of a method for obtaining the absolute calibration value of an absolute hydrostatic level in one embodiment. Figure 2 ;

[0054] Figure 7 This is a schematic diagram illustrating the distance calibration from the bottom surface of the lower bowl to the center of the top target ball in one embodiment;

[0055] Figure 8 A line graph showing the repeatability reading test results of an absolute hydrostatic level during disassembly and assembly in one embodiment;

[0056] Figure 9 A flowchart of a method for obtaining the absolute calibration value of an absolute hydrostatic level in one embodiment. Figure 3 ;

[0057] Figure 10 This is a schematic diagram of liquid depth measurement in one embodiment. Figure 1 ;

[0058] Figure 11 A flowchart of a method for obtaining the absolute calibration value of an absolute hydrostatic level in one embodiment. Figure 4 ;

[0059] Figure 12 This is a schematic diagram illustrating the principle of spectral confocal measurement and liquid level depth measurement in one embodiment;

[0060] Figure 13 This is a schematic diagram of liquid depth measurement in one embodiment. Figure 2 ;

[0061] Figure 14 A flowchart of a method for obtaining the absolute calibration value of an absolute hydrostatic level in one embodiment. Figure 5 ;

[0062] Figure 15 This is a schematic diagram of liquid depth measurement in one embodiment. Figure 3 ;

[0063] Figure 16 This is a schematic diagram of liquid depth measurement in one embodiment. Figure 4 ;

[0064] Figure 17 This is a flowchart of a method for obtaining the absolute elevation of an absolute hydrostatic level in one embodiment;

[0065] Figure 18 This is a schematic diagram for verifying the absolute elevation accuracy.

[0066] Figure 19 A scatter plot comparing the absolute elevation difference of AHLS and the elevation difference of the tracker;

[0067] Figure 20 This is a schematic diagram of an elevation datum based on a hydrostatic leveling system. Detailed Implementation

[0068] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0069] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0070] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0071] Hydrostatic levels are generally classified into two types based on their monitoring method: contact and non-contact. For elevation measurement, if a contact hydrostatic level is used, the external reference point derived from the level must be located at the center of the top of the level. However, most contact hydrostatic levels use differential measurement, and their signal and power supply devices are located in protruding positions on the top of the equipment, leaving no suitable design location for the external reference point. Furthermore, calibrating the absolute elevation of a contact hydrostatic level requires measuring the liquid level inside the basin, but this process involves separating the upper and lower basins. The separation of the float from the liquid causes changes in the liquid level inside the basin, making calibration difficult. If a non-contact hydrostatic level is used, please refer to [the relevant documentation / reference needed]. Figure 1 This non-contact hydrostatic level employs a micron-level monopole capacitive hydrostatic level. It utilizes a monopole capacitive sensor to detect liquid level changes and incorporates a 1.5-inch tracking target ball reference base at the top center of the level. This allows the liquid level within the hydrostatic level to be traced to the top reference point, thus meeting the absolute calibration conditions for the hydrostatic level. This type of hydrostatic level is also known as an absolute hydrostatic level, and the system it forms is called an Absolute Hydrostatic Leveling System (AHLS). In an AHLS, each monitoring point of the absolute hydrostatic level is an absolute elevation point. These points can serve as elevation reference points for elevation adjustment, improving the accuracy of the overall absolute elevation of the system, and also as elevation adjustment reference points for nearby equipment, enabling high-precision alignment of critical equipment.

[0072] As the analysis shows, after the absolute static leveling system stabilizes, please refer to... Figure 2 This level surface serves as a unified absolute elevation reference surface. Using this level surface as the elevation reference surface, the absolute elevation of a point is its height above the liquid surface. Since the liquid surface is inside the hydrostatic level and cannot be directly measured, the liquid is led out to the laser tracker target sphere (target sphere) at the top center of the absolute hydrostatic level. The height from the point to the laser tracker target sphere is calculated, and this height is added to the absolute elevation from the liquid surface to the laser tracker target sphere to calculate the absolute elevation of the point. Therefore, this absolute hydrostatic level can be used as an absolute elevation reference point. Specifically, when calibrating the absolute elevation, it can be calculated using the following formula:

[0073] H i_k =A k +(R i_k +C k )

[0074] H i_k This indicates the absolute elevation of the hydrostatic level, i.e. Figure 3 Distance with the number 1 in the middle; A k This represents the distance from the zero point of the single-plate capacitive sensor to the center of the laser tracker target ball at the top center of the hydrostatic level, which is the absolute calibration value of the absolute hydrostatic level. Figure 3 Distance with the symbol 2; R i_k This represents the distance from the zero point of the single-plate capacitive sensor in the k-th absolute hydrostatic level at time i to the liquid surface, i.e. Figure 3 The distance designated as 3 can be obtained from the reading of an absolute hydrostatic level. This reading is determined by the relative calibration performed on the absolute hydrostatic level at the factory. The obtained reading distance is not an absolute distance; there is a constant C between it and the absolute distance. k The deviation, the constant C of each absolute hydrostatic level. k The values ​​are different. In summary, it is only necessary to determine the value of each absolute hydrostatic level A. k and C k The value of can determine the absolute elevation of the absolute static level.

[0075] In determining A k When the value is , it is obtained by calculating using the following formula:

[0076] A k =MD k -W k -S k

[0077] MD k This indicates the distance from the bottom surface of the lower bowl body to the center of the top target ball, i.e. Figure 4 The distance with the central label number 21; W k Indicates the depth of the liquid, i.e. Figure 4 The distance with the central label number 22; S k This indicates the distance from the zero point of the single-plate capacitive sensor to the liquid surface, i.e. Figure 4 The distance with the number 23.

[0078] In the formula, S k This can be expressed by the following formula:

[0079] S k =R k +C k

[0080] R k This indicates the absolute hydrostatic level reading during absolute calibration. The liquid depth in the absolute hydrostatic level during calibration differs from that during measurement, resulting in a difference between the calibration and measurement readings. (C) k This represents the deviation constant.

[0081] Therefore, the formula for calculating the absolute elevation of an absolute hydrostatic level is:

[0082] H i_k =A k +(R i_k +Ck )

[0083] =MD k -W k -(R k +C k )+(R i_k +C k )

[0084] =MD k -W k -R k +R i_k

[0085] Therefore, when calculating the absolute calibration value of an absolute hydrostatic level during calibration, it is only necessary to determine the distance MD from the bottom surface of the lower bowl to the center of the top target ball. k , reading R of the static level during calibration k Liquid depth W k That's sufficient. When calculating the absolute elevation of an absolute static level, it is only necessary to determine the distance MD from the bottom surface of the lower bowl to the center of the top target ball. k , reading R of the hydrostatic level during calibration k Liquid depth W k And the static level reading R during measurement i_k That's all.

[0086] Please refer to Figure 5 This application discloses a method for obtaining the absolute calibration value of an absolute hydrostatic level in some embodiments, including the following steps:

[0087] Step S100: Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k .

[0088] Please refer to Figure 6 In some embodiments, step S100 obtains the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k Includes the following steps:

[0089] Step S101: Obtain the measurement point on the bottom surface of the lower bowl of the absolute static level to be calibrated.

[0090] Step S102: Fit a coordinate system based on the measurement points.

[0091] Step S103: Obtain the target ball boundary coordinates in the coordinate system.

[0092] Step S104: Fit the target ball center coordinates based on the target ball boundary coordinates.

[0093] Step S105: Determine the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball based on the center coordinates of the target ball. k .

[0094] In some embodiments, the distance MD from the bottom surface of the lower bowl of the absolute hydrostatic level to be calibrated to the center of the top target ball is... k Determined using a coordinate measuring machine.

[0095] Please refer to Figure 7 The lower bowl of the absolute static level is fixed on the platform of a coordinate measuring machine. First, the inner bottom surface of the lower bowl is measured. A horizontal coordinate system is established by fitting a plane through the measurement points on the inner bottom surface. Then, the upper and lower bowls of the absolute static level are assembled in place. The top target ball is measured, and the coordinates of the target ball boundary in the horizontal coordinate system are obtained. The coordinates of the target ball center are fitted based on the target ball boundary coordinates. Thus, the distance from the inner bottom surface of the lower bowl to the center of the top target ball is obtained through the coordinate measuring machine. When verifying the method for determining the distance from the inner bottom surface of the lower bowl to the center of the top target ball of the absolute static level provided in some embodiments of this application, measurements were taken on two absolute static levels respectively, and the measurement deviation was within 7 μm.

[0096] Step S200: Obtain the absolute hydrostatic level reading R during calibration. k .

[0097] In some embodiments, during calibration, the liquid level inside the absolute hydrostatic level to be calibrated is within the measurement range of the level. After the liquid inside the level stabilizes, the reading R of the absolute hydrostatic level is obtained. k .

[0098] When liquid is poured into the lower bowl of the absolute hydrostatic level, the liquid level should not exceed the measuring range. After the liquid stabilizes, the absolute hydrostatic level reading is recorded. As is known from the principle of absolute elevation measurement, the measurement process of the absolute hydrostatic level involves multiple disassemblies and reassemblies of the upper and lower bowls. Therefore, the repeatability error of the absolute hydrostatic level for measuring liquid levels of equal height must not exceed the instrument's measurement error. The repeatability accuracy is mainly determined by the installation accuracy of the upper and lower bowls of the absolute hydrostatic level and the measurement stability of the sensor. To verify the error accuracy of the absolute hydrostatic level readings provided in some embodiments of this application, multiple disassembly and reassembly experiments of the upper and lower bowls of the absolute hydrostatic level were conducted without changing the internal liquid height. Please refer to... Figure 8 This indicates that the reading deviation between two adjacent measurements is within 4 μm, and the overall liquid level shows a downward trend. Analysis shows that this is due to liquid evaporation during disassembly. The results show that the repeatability error of the absolute hydrostatic level measurement of the liquid level before and after disassembly does not exceed 4 μm.

[0099] Step S300: Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated. k .

[0100] Please refer to Figure 9 In some embodiments, step S300 obtains the liquid depth W inside the absolute hydrostatic level to be calibrated. k Includes the following steps:

[0101] Step S311: Obtain the distance the multimeter needle moves from the design reference surface of the lower bowl of the absolute static level to be calibrated to the liquid surface inside the lower bowl of the absolute static level to be calibrated.

[0102] Step S312: Based on the distance from the design reference plane of the lower bowl of the absolute static level to be calibrated to the bottom surface of the lower bowl, and the movement distance of the multimeter needle, determine the liquid depth W inside the absolute static level to be calibrated. k .

[0103] In some embodiments, the distance the multimeter needle moves is determined by a coordinate measuring machine or a displacement stage.

[0104] The multimeter needle is fixed to a precision displacement device. This device moves the needle from a reference plane to the liquid surface. The moment the needle touches the liquid, the multimeter will display a resistance value due to the liquid's conductivity. The vertical displacement of the multimeter at this point represents the distance from the liquid surface to the reference plane. Furthermore, the distance from the reference plane to the bottom surface of the lower container can be precisely measured. Therefore, the liquid depth can be indirectly obtained by the difference between the distance from the liquid surface to the reference plane and the distance from the reference plane to the bottom surface of the lower container.

[0105] Please refer to Figure 10 The multimeter is fixed on the coordinate measuring machine, and the precise distance from the reference surface of the lower bowl of the absolute static level to the liquid surface is obtained by the motion value of the coordinate measuring machine.

[0106] Please refer to Figure 11 In some embodiments, step S300 obtains the liquid depth W inside the absolute hydrostatic level to be calibrated. k Includes the following steps:

[0107] Step S321: Obtain the first liquid depth determined by the coaxial displacement sensor at a first set distance from the middle depth of the liquid.

[0108] Step S322: Obtain the second liquid depth determined by the coaxial displacement sensor at a second set distance from the middle depth of the liquid.

[0109] Step S323: Obtain the third liquid depth determined by the coaxial displacement sensor at a third set distance from the middle depth of the liquid.

[0110] Wherein, the first set distance is less than the second set distance, the second set distance is less than the third set distance; and the difference between the second set distance and the first set distance is equal to the difference between the third set distance and the second set distance.

[0111] Step 324: Determine the liquid depth W inside the absolute hydrostatic level to be calibrated based on the first liquid depth, the second liquid depth, and the third liquid depth. k .

[0112] In some embodiments, when the liquid level in the lower bowl of the absolute static level to be calibrated is outside the measurement range of the liquid in the absolute static level to be calibrated, a standard heightening pad is placed in the lower bowl of the absolute static level to be calibrated, so that the liquid depth is within the range of the coaxial displacement sensor, and the liquid level is within the range of the absolute static level to be calibrated.

[0113] Please refer to Figure 12 In some embodiments, the Keyence Laser Color CL-700 coaxial displacement sensor is used to measure the liquid depth within the absolute hydrostatic level to be calibrated. Based on the principle of spectral confocality, the Keyence Laser Color CL-700 coaxial displacement sensor can directly obtain the absolute thickness of a transparent object. The instrument incorporates a beam splitter to delimit the light emitted from a white light point source, focusing different spectral wavelengths of light onto a single axis through different optical paths, forming a focal axis. Since different cross-sections of the measured object reflect different wavelengths of light differently, the thickness information of the measured object can ultimately be obtained through imaging on a CCD camera.

[0114] Please refer to Figure 13 In some embodiments, when the liquid level in the lower bowl of the absolute static level is too low, it will exceed the range of the level. Therefore, in order to ensure that the liquid level is within the range of the coaxial displacement sensor and the absolute static level, a standard heightening pad is placed at the bottom of the bowl of the absolute static level so that the liquid level in the bowl is within the range of the two sensors.

[0115] In some embodiments, the coaxial displacement sensor measures the liquid depth at three predetermined distances. The second predetermined distance is approximately 70 mm from the center depth of the liquid. The first predetermined distance is 1.5 mm lower than the first predetermined distance, and the third predetermined distance is 1.5 mm higher than the first predetermined distance. At these three locations, both the upper and lower surfaces of the liquid are within the instrument's measurement range. The average liquid depth measurement at the three locations is taken as the absolute value of the water depth. Through multiple tests, the liquid depth measurement accuracy is verified to be within 0.03 mm.

[0116] Please refer to Figure 14In some embodiments, step S300 obtains the liquid depth W inside the absolute hydrostatic level to be calibrated. k Includes the following steps:

[0117] Step S331: Determine the first distance from the bottom surface of the lower bowl of the absolute static level to be calibrated to the probe of the coaxial displacement sensor when no liquid is added to the absolute static level to be calibrated, based on the coaxial displacement sensor.

[0118] Step S332: Determine the second distance from the liquid level in the lower bowl of the absolute static level to the probe of the coaxial displacement sensor when liquid is added to the absolute static level to be calibrated, based on the coaxial displacement sensor.

[0119] Step S333: Determine the liquid depth W inside the absolute hydrostatic level to be calibrated based on the first distance and the second distance. k .

[0120] In some embodiments, when the liquid level in the lower bowl of the absolute static level to be calibrated is outside the measurement range of the liquid in the absolute static level to be calibrated, a standard heightening pad is placed in the lower bowl of the absolute static level to be calibrated, so that the liquid depth is within the range of the coaxial displacement sensor, and the liquid level is within the range of the absolute static level to be calibrated.

[0121] Please refer to Figure 15 The coaxial displacement sensor directly measures the first distance h1 between the top surface of the standard raised pad and the probe of the coaxial displacement sensor; please refer to... Figure 16 With the coaxial displacement sensor stationary, liquid within the range of both the absolute hydrostatic level and the coaxial displacement sensor is added into the bowl. The coaxial displacement sensor measures a first distance h2 between the liquid surface and the sensor probe; therefore, the liquid depth is obtained by the difference between the first and second distances. In some embodiments, if the liquid level and depth are both within the range of the hydrostatic level and the coaxial displacement sensor after water is added, a standard heightening pad is not required.

[0122] In some embodiments, when obtaining the absolute hydrostatic level reading R during calibration, k Then, obtain the liquid depth W inside the absolute hydrostatic level to be calibrated. k .

[0123] Step S400: Calculate the absolute calibration value of the absolute static level to be calibrated.

[0124] In some embodiments, the absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula:

[0125] A k =MDk -R k -W k

[0126] Among them, A k This indicates the absolute calibration value of the absolute hydrostatic level to be calibrated.

[0127] By measuring the three parameters provided in the embodiments of this application during calibration, the absolute calibration value of the absolute static level to be calibrated can be obtained. Specifically, the measurement accuracy of the distance from the bottom surface of the lower bowl to the center of the top target ball is 7 μm, the liquid depth measurement accuracy is 0.03 mm, and the measurement accuracy of the static level reading is 4 μm. Considering factors such as multiple installation errors of the bowl, the absolute calibration value accuracy of a single absolute static level is within 0.04 mm, that is:

[0128]

[0129] M 标定 This indicates the absolute calibration accuracy of the absolute static level to be calibrated.

[0130] Please refer to Figure 17 Some embodiments of this application also disclose a method for obtaining the absolute elevation of an absolute hydrostatic level, including the following steps:

[0131] Step S10: Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k .

[0132] Step S20: Obtain the absolute hydrostatic level reading R during calibration. k .

[0133] Step S30: Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated. k .

[0134] Step S40: Calculate the absolute calibration value of the absolute static level to be calibrated.

[0135] In some embodiments, the absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula:

[0136] A k =MD k -R k -W k

[0137] Among them, A k This indicates the absolute calibration value of the absolute hydrostatic level to be calibrated.

[0138] Step S50: Connect multiple absolute static levels to form an absolute static leveling system, and obtain the absolute static level reading R during the measurement of the absolute static level to be calibrated. i_k .

[0139] Step S60: Calculate the absolute elevation of the absolute hydrostatic level to be calibrated. The absolute elevation of the absolute hydrostatic level to be measured is obtained by calculating the following formula:

[0140] H i_k =A k +R i_k

[0141] Among them, H i_k This indicates the absolute elevation of the static level to be measured.

[0142] Using the absolute elevation calculation method for absolute static levels provided in this application, after calibrating two absolute static levels, they can be connected in series to form a simple two-point absolute static leveling system. The absolute elevation established by this system can be verified in principle and its accuracy checked using existing laser trackers and displacement stages.

[0143] The laser tracker, based on the principle of polar coordinate measurement, obtains the three-dimensional coordinates of a point by measuring distance, horizontal angle, and vertical angle. The laser tracker has a built-in electronic level. During measurement, the instrument is leveled, and horizontal measurements are performed at a single station. The electronic level obtains the deviation information of the instrument's vertical axis and vertical direction. After the measurement is completed, the leveling elevation information between the points is obtained. Domestic research has been conducted on the elevation measurement accuracy of the laser tracker, and the single-station, short-range elevation measurement accuracy of the laser tracker is reliable.

[0144] Please refer to Figure 18 Two absolute hydrostatic levels are placed on two micrometer-level displacement stages, connected by water pipes, air pipes, and related acquisition equipment to form a two-point AHLS monitoring system. First, a laser tracker measures the target sphere at the top of the level to obtain the elevations of hydrostatic levels 1# and 2# in the laser tracker's horizontal coordinate system. Simultaneously, the absolute elevation of the target sphere below the current liquid surface (level surface) can be directly obtained using the absolute elevation calculation method described in some embodiments of this application. Elevations are obtained through both methods. Using hydrostatic level 1# as a reference, the absolute height difference of hydrostatic level 2# relative to hydrostatic level 1# and the absolute height difference of the absolute hydrostatic leveling system are obtained.

[0145] During the test, the two heavy displacement stages were 10m apart. Static level 1# remained stationary, and the heavy displacement stage first moved static level 2# upwards, measuring a total of 11 times; then the displacement stage moved static level 2# vertically downwards, measuring a total of 11 times; the upward and downward movement of the displacement stage each time was 250μm.

[0146] According to the method for calculating the absolute elevation of the static level provided in this application, the absolute elevations of static level 1# and static level 2# are expressed as follows:

[0147] H 1水 =h i,1水 +A1

[0148] H 2水 =h i,2水 +A2

[0149] H 1水 Indicates the absolute elevation of hydrostatic level #1; H 2水 This indicates the absolute elevation of hydrostatic level #2; h i,1水 This represents the reading of the hydrostatic level #1 after i movements; h i,2水 A1 represents the reading of static level 2# after i movements; A2 represents the absolute calibration value of static level 1#; A2 represents the absolute calibration value of static level 2#.

[0150] After i movements, the absolute elevation difference between the water in hydrostatic level 2 and hydrostatic level 1 is expressed as follows:

[0151] H i,2_1水 =(h i,2水 -h i,1水 )+(A2-A1)

[0152] H i,2_1水 This indicates the absolute elevation difference between the water in hydrostatic level #2 and hydrostatic level #1.

[0153] The elevation difference between static level 2# and static level 1# after i movements, obtained by laser tracking, is expressed as follows:

[0154] H i,2_1跟 =h i,2跟 -h i,1跟

[0155] H i,2_1跟 This represents the elevation difference between static level 2# and static level 1#, as measured by the laser tracker; h i,2跟 This represents the elevation of the hydrostatic level 2# obtained by the laser tracker in the horizontal coordinate system after i movements; h i,1跟 This indicates the elevation of the static level 1# obtained by the laser tracker in the horizontal coordinate system after i movements.

[0156] The change in elevation difference between static level 2# and static level 1# obtained by the laser tracker was compared with the motion of the displacement stage. The error range was -31μm to 9μm, and the measurement results were consistent with the nominal accuracy of the laser tracker.

[0157] Please refer to Figure 19 The absolute elevation difference between static level 2# and static level 1#, determined by the absolute elevation calculation method provided in this application, is compared with the elevation difference between static level 2# and static level 1# obtained by laser tracking. It can be seen that among the 22 measurement points (ascent and descent), only two points have a deviation exceeding 0.05mm, with a maximum of 0.08mm. The deviations of the remaining 20 monitoring points are all within 0.05mm. Therefore, using a laser tracking device to verify the absolute elevation calculation method provided in this application, after eliminating gross errors, the absolute elevation deviation of the levels obtained within a 10m range is no higher than 0.05mm.

[0158] To comprehensively improve the elevation accuracy of the tunnel control network and the alignment accuracy of the equipment, a high-precision absolute elevation leveling system, namely the absolute static leveling system, is proposed based on the traditional static leveling system. Based on the absolute static level instrument in this system, this application creatively provides a method for the absolute calibration and absolute elevation calculation of the absolute static level instrument. This method is completely different from geometric leveling, has no cumulative error, and can obtain high-precision absolute elevation in real time. Please refer to [reference needed]. Figure 20 Each static level serves as both a height deformation monitoring point and a benchmark point, directly applicable to the establishment of height benchmarks for tunnel control networks and equipment alignment. This represents a novel method for establishing high-precision absolute height benchmarks. Experiments have demonstrated the ability to acquire absolute elevations with an accuracy of 0.05mm within a 10-meter range online and in real-time.

[0159] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for obtaining the absolute calibration value of an absolute hydrostatic level, characterized in that, include: Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k ; Obtain the absolute hydrostatic level reading R during calibration. k ; Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated k The method for obtaining the liquid depth W inside the absolute hydrostatic level to be calibrated k This includes: obtaining the distance the multimeter needle moves from the design reference surface of the lower bowl of the absolute hydrostatic level to the liquid surface in contact with the liquid inside the lower bowl; and determining the liquid depth W inside the absolute hydrostatic level based on the distance from the design reference surface of the lower bowl to the bottom surface of the lower bowl and the distance the multimeter needle moves. k ; The absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula: A k =MD k -R k -W k Wherein, Ak represents the absolute calibration value of the absolute hydrostatic level to be calibrated.

2. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, The distance MD from the bottom surface of the lower bowl of the absolute hydrostatic level to be calibrated to the center of the top target ball is obtained. k ,include: Obtain the measurement point on the bottom surface of the lower bowl of the absolute static level to be calibrated; A coordinate system is fitted based on the measurement points; Obtain the target ball boundary coordinates in the coordinate system; Fit the target ball center coordinates based on the target ball boundary coordinates; The distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball is determined based on the coordinates of the target ball's center. k .

3. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, The absolute hydrostatic level reading R is obtained during the calibration process. k ,include: During the calibration of the absolute static level, the liquid level inside the absolute static level is within the measurement range of the absolute static level. After the liquid inside the absolute hydrostatic level to be calibrated has stabilized, the reading R of the absolute hydrostatic level to be calibrated is obtained. k .

4. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, The movement distance of the multimeter needle is determined by a coordinate measuring machine or a displacement stage.

5. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, The liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include: The first liquid depth, determined by the coaxial displacement sensor at a first predetermined distance from the middle depth of the liquid, is obtained. The second liquid depth, determined by the coaxial displacement sensor at a second predetermined distance from the middle depth of the liquid, is obtained. A third liquid depth is obtained by a coaxial displacement sensor at a third predetermined distance from the middle depth of the liquid; wherein the first predetermined distance is less than the second predetermined distance, the second predetermined distance is less than the third predetermined distance; and the difference between the second predetermined distance and the first predetermined distance is equal to the difference between the third predetermined distance and the second predetermined distance. The liquid depth W inside the absolute hydrostatic level to be calibrated is determined based on the first liquid depth, the second liquid depth, and the third liquid depth. k .

6. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, The liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include: The first distance from the bottom surface of the lower bowl of the absolute static level to the probe of the coaxial displacement sensor is determined by the coaxial displacement sensor when no liquid is added to the absolute static level to be calibrated. The second distance from the liquid level in the lower bowl of the absolute static level to the probe of the coaxial displacement sensor is determined by the coaxial displacement sensor when liquid is added to the absolute static level to be calibrated. The liquid depth W inside the absolute hydrostatic level to be calibrated is determined based on the first distance and the second distance. k .

7. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 5 or 6, characterized in that, The liquid depth W inside the absolute hydrostatic level to be calibrated is obtained. k ,include: When the liquid level in the lower bowl of the absolute static level to be calibrated is not within the set value of the measurement range of the liquid in the absolute static level to be calibrated, a standard heightening pad is placed in the lower bowl of the absolute static level to be calibrated, so that the liquid depth is within the range of the coaxial displacement sensor, and the liquid level is within the range of the absolute static level to be calibrated.

8. The method for obtaining the absolute calibration value of an absolute hydrostatic level as described in claim 1, characterized in that, When obtaining the absolute static level reading R during calibration, k Then, obtain the liquid depth W inside the absolute hydrostatic level to be calibrated. k .

9. A method for obtaining the absolute elevation of an absolute hydrostatic level, characterized in that, include: Obtain the distance MD from the bottom surface of the lower bowl of the absolute static level to be calibrated to the center of the top target ball. k ; Obtain the absolute hydrostatic level reading R during calibration. k ; Obtain the liquid depth W inside the absolute hydrostatic level to be calibrated k ; The absolute calibration value of the absolute hydrostatic level to be calibrated is calculated using the following formula: A k =MD k -R k -W k Among them, A k This indicates the absolute calibration value of the absolute hydrostatic level to be calibrated. Obtain the absolute static level reading R during the measurement of the absolute static level to be calibrated. i_k ; The absolute elevation of the absolute hydrostatic level to be calibrated is calculated using the following formula: H i_k =A k +R i_k Wherein, Hi_k represents the absolute elevation of the absolute hydrostatic level to be calibrated.

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