Method for determining reference temperature and reference thermal expansion coefficient of large-size measurement field

Abstract

The application belongs to the technical field of thermal expansion compensation of large aircraft process equipment, and particularly relates to a large-size measurement field reference temperature and reference thermal expansion coefficient value determination method. The application extracts the temperature of the center material of the measurement field structure as the reference temperature according to the nonlinear thermal expansion characteristics of the temperature change of the large-size measurement field, selects the appropriate reference temperature according to multiple measurements, calculates the relatively close linear thermal expansion coefficient simplified according to the large-range nonlinear thermal expansion according to multiple measurements, comprehensively calculates the reference thermal expansion coefficient of the measurement field in combination with the thermal expansion coefficient of the scale, and finally fits and compensates the measurement field coordinate system by using the interval reference temperature and the reference thermal expansion coefficient, so that the problem of large measurement error caused by the inconsistency of the reference temperature and the reference thermal expansion coefficient of the large-size measurement field is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal expansion compensation of large aircraft process equipment, and particularly relates to a large-size measurement field reference temperature and reference thermal expansion coefficient value determination method. BACKGROUND

[0002] In a large-size high-precision assembly process, especially in an aircraft component assembly process, a measurement reference system needs to be established, and the large-size measurement reference system is referred to as a measurement field. The large-size measurement field is greatly affected by the stability of the foundation and aircraft process equipment, environmental temperature changes, air flow, light changes and the like, especially by environmental temperature changes. For an 80m large-size measurement field, the maximum temperature change in the plane direction can be up to 1℃ / 10m, the maximum temperature change in the height direction can be up to 1℃ / 3m, and the maximum overall temperature change of the large-size measurement field at a certain moment can be up to 5℃, and the temperature difference between the highest and lowest temperatures in a year can be up to 15℃.

[0003] At present, the conventional measurement field is measured and constructed by using a laser tracker. The thermal expansion compensation is mainly performed according to the air temperature at the position of the measurement head of the laser tracker. Based on the large-size measurement field, the temperature change and the thermal expansion of the measurement field reference structure material are affected, and the temperature change and the corresponding thermal expansion process belong to a nonlinear change process. It is difficult to accurately reflect the thermal expansion change of the measurement field by simply using the thermal expansion coefficient measurement and calculation method of the structure material. Therefore, there is a large error in the measurement data of the same large-size structure at different times, by different personnel and in different environments. The accumulated global and local error can be up to about 1mm / 40m. These problems make it very difficult to realize the global assembly of the large aircraft at the sub-millimeter level and the local assembly at the 0.1mm level. At present, the length error of the aircraft assembly is more than 5mm, the relative local object measurement error of the horizontal measurement point of the symmetry representation is more than 0.5mm, and the actual global error of the whole machine is more than 1mm.

[0004] In order to improve the positioning precision of the global assembly of the large aircraft at the sub-millimeter level and the local assembly at the 0.1mm level, temperature compensation and control are needed, and the key lies in determining the reference temperature and the reference thermal expansion coefficient value in the measurement process. It is urgent to explore a method capable of unifying the measurement process of the large-size measurement field and standardizing the reference temperature and the reference thermal expansion coefficient value, so as to improve the construction precision and the standardization level of the large-size measurement field.

[0005] Therefore, there is an urgent need for a technical solution to overcome or alleviate at least one of the above-mentioned defects of the prior art. SUMMARY

[0006] The purpose of the present application is to provide a large-size measurement field reference temperature and reference thermal expansion coefficient value determination method to solve at least one problem existing in the prior art.

[0007] The technical solution of the present application is:

[0008] A large-size measurement field reference temperature and reference thermal expansion coefficient value determination method, comprising:

[0009] Step 1, arranging a measurement reference point on a reference measurement structure;

[0010] Step 2, determining four vertices of the maximum profile of the measurement reference point, and selecting the intersection of the diagonals of the four vertices as a compensation station;

[0011] Step 3, obtaining a scale of the same material as the reference measurement structure, and calibrating the distance between the two endpoints of the scale under standard temperature conditions to obtain a scale calibration value;

[0012] Step 4, selecting multiple time periods from the overall measurement calibration period, selecting multiple measurement times within each time period, taking the surface temperature of the reference measurement structure at the compensation station as the reference temperature, calculating the average of the surface temperatures of the four vertices of the reference measurement structure at each measurement time, and obtaining the instantaneous reference temperature at each measurement time;

[0013] Step 5, calculating the average of each instantaneous reference temperature in the same time period to obtain the interval reference temperature of each time period;

[0014] Step 6, taking the interval reference temperature of each time period as the compensation temperature of the measurement calibration, fitting the measurement field coordinate system, and obtaining the coordinate value of the measurement reference point in each time period;

[0015] Step 7, calculating the thermal expansion coefficient of the reference measurement structure according to the interval reference temperature of each time period and the distance between the two measurement reference points;

[0016] Step 8, selecting an instantaneous reference temperature at a measurement time, setting a laser tracker at the compensation station, arranging the scale on the reference measurement structure, and measuring the distance between the two endpoints of the scale multiple times within a set time fluctuation range through the laser tracker, calculating the average of multiple measurements, and obtaining a scale measurement value;

[0017] Step 9, calculating the thermal expansion coefficient of the scale according to the standard temperature, the selected instantaneous reference temperature, the scale calibration value, and the scale measurement value;

[0018] Step 10, calculating the average of the thermal expansion coefficients of the reference measurement structure and the scale to obtain a reference thermal expansion coefficient.

[0019] In at least one embodiment of the present application, in step 1, the reference measurement structure is a foundation or aircraft process equipment.

[0020] In at least one embodiment of the present application, in step 3, the distance between the two end points of the scale is calibrated when the surface temperature at the center of the scale is the standard temperature.

[0021] In at least one embodiment of the present application, in step 4, the same time interval exists between each measurement time within the same time period.

[0022] In at least one embodiment of the present application, the time interval is not less than 30 minutes and not more than 2 hours.

[0023] In at least one embodiment of the present application, in step 7, the thermal expansion coefficient of the reference measurement structure is:

[0024] α j 1 = (L2 j+1 -L2 j ) / [L2 j × (T2 j+1 -T2 j )];

[0025] α 1 =∑(α j 1 ) / (n);

[0026] j = 1, 2, …, n;

[0027] wherein α j 1 is the thermal expansion coefficient of the reference measurement structure in the jth time period, L2 j+1 is the distance between the two measurement reference points in the j+1th time period, L2 j is the distance between the two measurement reference points in the jth time period, T2 j+1 is the interval reference temperature in the j+1th time period, T2 j is the interval reference temperature in the jth time period, α 1 is the thermal expansion coefficient of the reference measurement structure, and n is the number of time periods.

[0028] In at least one embodiment of the present application, in step 8, the scale is arranged on the reference measurement structure in the following manner:

[0029] The scale is arranged along the length direction of the measurement field, offset by a set distance in the width direction of the measurement field with the compensation station as the symmetrical center, the two end points of the scale form an isosceles triangle with the compensation station, and the set distance is not more than 2m.

[0030] In at least one embodiment of the present application, in step 8, the time fluctuation range is not more than 10 minutes.

[0031] In at least one embodiment of the present application, in step 9, the thermal expansion coefficient of the scale is:

[0032] α 2 = (L1 1 -L1) / [L1 x (T1 i -T1)];

[0033] i = 1, 2, …, k;

[0034] Wherein, α 2 is the thermal expansion coefficient of the scale, L1 1 is the measured value of the scale, L1 is the calibrated value of the scale, T1 i is the instantaneous reference temperature at the i-th selected measurement time, T1 is the standard temperature, and k is the number of measurement times.

[0035] In at least one embodiment of the present application, it further comprises:

[0036] Step 11, selecting a measurement station on the reference measurement structure, fitting a measurement field coordinate system based on the interval reference temperature and the reference thermal expansion coefficient of each time period.

[0037] The present application has at least the following beneficial technical effects:

[0038] The large-size measurement field reference temperature and reference thermal expansion coefficient value method of the present application solves the problem of large measurement error caused by the inconsistency of the large-size measurement field reference temperature and reference thermal expansion coefficient. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a measurement field schematic diagram of an embodiment of the present application.

[0040] Wherein:

[0041] 1-Reference measurement structure; 2-Measurement reference point; 3-Measurement station; 4-Scale; 5-Compensation station; 6-Diagonal line. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0043] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0044] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0045] This application provides a method for determining the reference temperature and reference thermal expansion coefficient of a large-size measurement field, including the following steps:

[0046] Step 1: Arrange measurement reference points 2 on the reference measurement structure 1.

[0047] like Figure 1 As shown, during the assembly of aircraft components, a measurement reference point 2 is set up in the measurement field, which is arranged on the foundation or on the aircraft process equipment.

[0048] Step 2: Determine the four vertices of the maximum contour of the measurement reference point 2, and select the intersection of the diagonals 6 of the four vertices as the compensation station 5.

[0049] The structural average value of the four vertices of the maximum profile of the measurement reference point 2 is taken as the compensation station 5. In one embodiment of this application, the measurement reference point 2 is arranged on the foundation, and the intersection of the diagonals 6 of the four vertices of the maximum profile of the measurement reference point 2 is selected as the compensation station 5. It can be understood that if the measurement reference point 2 is arranged on aircraft manufacturing equipment, the projection point of the intersection of the diagonals 6 of the four vertices of the maximum profile of the measurement reference point 2 onto the foundation can also be selected as the compensation station 5.

[0050] Step 3, obtain a ruler 4 made of the same material as the reference measurement structure 1, and calibrate the distance between the two end points of the ruler 4 under standard temperature conditions to obtain a ruler calibration value.

[0051] In a laboratory environment, the distance between the two end points of the ruler 4 is calibrated when the surface temperature at the center of the ruler 4 is the standard temperature T1 to obtain a ruler calibration value L1. The center of the ruler 4 is the center position in the length direction and the width direction of the ruler 4. In this embodiment, the standard temperature T1 = 20℃, the ruler 4 is selected to be 2m, and the ruler calibration value L1 = 2000.000mm.

[0052] Step 4, select multiple time periods from the overall measurement calibration period, select multiple measurement times within each time period, take the surface temperature of the reference measurement structure 1 of the compensation station 5 as the reference temperature, calculate the average of the surface temperature of the reference measurement structure 1 of the four vertices, and obtain the instantaneous reference temperature at each measurement time.

[0053] Select n time periods from the overall measurement calibration period, and select k measurement times within each time period. Each measurement time in the same time period has the same time interval, and the preferred time interval is not less than 30 minutes and not more than 2 hours.

[0054] In the case of large temperature changes in the entire area of the measurement reference point 2, the average of the surface temperature of the reference measurement structure 1 at the positions of the four vertices of the largest contour is taken as the instantaneous reference temperature, and the instantaneous reference temperature T1 i at the k measurement times of each time period is calculated, i = 1, 2, …, k.

[0055] In this embodiment, four measurement times with the same time interval are selected within each time period, and the instantaneous reference temperatures at the four measurement times of the first time period are calculated, T1 1 = 23℃, T1 2 = 23.5℃, T1 3 = 25℃, and T1 4 = 24.5℃.

[0056] Step 5, calculate the average of each instantaneous reference temperature in the same time period to obtain the interval reference temperature of each time period.

[0057] In this embodiment, the average of the four instantaneous reference temperatures is T2 1 = (23℃ + 23.5℃ + 25℃ + 24.5℃) / 4 = 24℃, and the interval reference temperature of the first time period is 24℃.

[0058] The interval reference temperatures T2 j, j = 1, 2, …, n. In this embodiment, four time periods are selected, and the interval reference temperatures of the four time periods are calculated, T2 1 = 24℃, T2 2 = 24.2℃, T2 3 = 24.5℃, and T2 4 = 24.9℃.

[0059] Step 6, taking the interval reference temperature of each time period as the compensation temperature of the measurement calibration, fitting the measurement field coordinate system, and obtaining the coordinate values of the measurement reference point 2 in each time period.

[0060] Step 7, according to the interval reference temperature of each time period and the distance between the two measurement reference points 2, calculating the thermal expansion coefficient of the reference measurement structure 1.

[0061] The thermal expansion coefficient calculation formula of the reference measurement structure 1 is:

[0062] α j 1 = (L2 j+1 -L2 j ) / [L2 j × (T2 j+1 -T2 j )];

[0063] α 1 =∑(α j 1 ) / (n);

[0064] j = 1, 2, …, n;

[0065] Wherein, α j 1 is the thermal expansion coefficient of the reference measurement structure in the jth time period, L2 j+1 is the distance between the two measurement reference points in the j+1th time period, L2 j is the distance between the two measurement reference points in the jth time period, T2 j+1 is the interval reference temperature in the j+1th time period, T2 j is the interval reference temperature in the jth time period, α 1 is the thermal expansion coefficient of the reference measurement structure, and n is the number of time periods.

[0066] Through measurement, at the interval reference temperatures T2 1 = 24℃, T2 2 = 24.2℃, T2 3 = 24.5℃, and T2 4= 24.9℃, taking the distance between two measurement reference points 2 at a standard distance L2= 76000mm at a standard temperature of 20℃ as an example, the coordinates of the measurement reference points 2 in each time period are obtained by fitting the measurement field coordinate system, and the distance between the two measurement reference points 2 is calculated.

[0067] In this embodiment, the distance between the two measurement reference points 2 in four time periods is obtained, L2 1 = 76003.344mm, L2 2 = 76003.512mm, L2 3 = 76003.763mm, L2 4 = 76004.095mm.

[0068] Then the thermal expansion coefficient of the reference measurement structure 1 in each time period is:

[0069] α1 1 = (L2 2 -L2 1 ) / {L2 1 × (T2 2 -T2 1 )} = 1.105 × 10 -5 / ℃;

[0070] α2 1 = (L2 3 -L2 2 ) / {L2 2 × (T2 3 -T2 2 )} = 1.1008 × 10 -5 / ℃;

[0071] α3 1 = (L2 4 -L2 3 ) / {L2 3 × (T2 4 -T2 3 )} = 1.092 × 10 -5 / ℃;

[0072] α4 1 = (L2 1 -L2 4 ) / {L2 4 × (T2 1 -T2 4 )} = 1.0978 × 10 -5 / ℃;

[0073] Then the thermal expansion coefficient of the reference measurement structure 1 is:

[0074] α 1=∑(1.105×10 -5 +1.1008×10 -5 +1.092×10 -5 +1.0978×10 -5 ) / 4 = 1.0989 × 10 -5 / ℃;

[0075] Step 8: Select an instantaneous reference temperature at a measurement time, set up a laser tracker at compensation station 5, place the scale 4 on the reference measurement structure 1, and within the set time fluctuation range, measure the distance between the two ends of the scale 4 multiple times using the laser tracker, calculate the average value of the multiple measurements, and obtain the scale measurement value.

[0076] In this embodiment, the ruler 4 is arranged on the reference measurement structure 1 as follows: the ruler 4 is arranged along the length of the measurement field, with the compensation station 5 as the center of symmetry, and offset by a set distance in the width direction of the measurement field. The two ends of the ruler 4 and the compensation station 5 form an isosceles triangle, and the set distance does not exceed 2m.

[0077] In a preferred embodiment of this application, the time fluctuation range is no greater than 10 minutes. Using the selected measurement time as a reference, the distance between the two endpoints of the scale 4 is measured multiple times within a time frame no greater than 10 minutes. In this embodiment, the instantaneous reference temperature T1 at one measurement time is selected. 1 =23℃, the distance between the two ends of the scale 4 was measured three times and the average value was taken to obtain the scale measurement value L1. 1 =2000.0726mm.

[0078] Step 9: Calculate the coefficient of thermal expansion of scale 4 based on the standard temperature, the selected instantaneous reference temperature, the scale calibration value, and the scale measurement value.

[0079] The formula for calculating the coefficient of thermal expansion on scale 4 is:

[0080] α 2 =(L1 1 -L1) / [L1×(T1) i -T1)];

[0081] i = 1, 2, ..., k;

[0082] Where, α 2 L1 is the coefficient of thermal expansion of the scale. 1 L1 is the measured value of the scale, and T1 is the calibrated value of the scale. i T1 represents the instantaneous reference temperature at the selected i-th measurement moment, where T1 is the standard temperature and k is the number of measurement moments.

[0083] In this embodiment, α 2= (2000.066mm - 2000.000mm) / (2000.000mm x (23℃ - 20℃)) = 1.100 x 10 -5 / ℃.

[0084] The thermal expansion coefficient of the reference measurement structure 1 is reviewed according to the thermal expansion coefficient of the scale 4.

[0085] Step 10, calculate the average of the thermal expansion coefficient of the reference measurement structure 1 and the thermal expansion coefficient of the scale 4 to obtain the reference thermal expansion coefficient.

[0086] In this embodiment, the reference thermal expansion coefficient is a:

[0087] a = (1.0989 x 10 -5 / ℃ + 1.100 x 10 -5 / ℃) / 2 = 1.09945 x 10 -5 / ℃.

[0088] The method for determining the reference temperature and the reference thermal expansion coefficient of the large-size measurement field also includes:

[0089] Step 11, select a measurement station 3 on the reference measurement structure 1, and fit the measurement field coordinate system based on the interval reference temperature and the reference thermal expansion coefficient of each time period.

[0090] When fitting the measurement field coordinate system, the interval reference temperature and the reference thermal expansion coefficient are used as the reference for global coordinate system compensation, solving the problem of large measurement error caused by the inconsistency of the reference temperature and the reference thermal expansion coefficient of the large-size measurement field.

[0091] The method for determining the reference temperature and the reference thermal expansion coefficient of the large-size measurement field is aimed at the nonlinear characteristics of thermal expansion caused by temperature changes in the large-size measurement field. The temperature of the center material of the measurement field structure is extracted as the reference temperature, and the appropriate reference temperature is selected according to multiple measurements. Meanwhile, the relatively close linear thermal expansion coefficient simplified from the large-range nonlinear thermal expansion is calculated according to multiple measurements. The reference thermal expansion coefficient of the measurement field is obtained by comprehensive calculation combined with the thermal expansion coefficient of the scale 4. Finally, the interval reference temperature and the reference thermal expansion coefficient are used to fit and compensate the measurement field coordinate system. The application determines the selection position of the reference temperature of the large-size measurement field, and combines the thermal expansion coefficient of the on-site structure and the scale 4 to clearly define the calculation method of the large-range thermal expansion coefficient, solving the problem of large measurement error caused by the inconsistency of the reference temperature and the reference thermal expansion coefficient of the large-size measurement field.

[0092] The large-size measurement field reference temperature and reference thermal expansion coefficient value method is suitable for large-size measurement field construction above 30m and product object measurement, has important performance implementation reference value, popularization and application value, performance implementation support guiding significance for large-size high-precision aviation product manufacturing and assembly, and has universal applicability.

[0093] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for determining the values of a reference temperature and a reference coefficient of thermal expansion of a large-scale measurement field, characterized in that The method comprises the following steps: Step 1, arranging a measurement reference point (2) on a reference measurement structure (1); Step 2, determining four vertices of the maximum profile of the measurement reference point (2), and selecting the intersection of the diagonal lines (6) of the four vertices as a compensation station (5); Step 3, obtaining a scale (4) made of the same material as the reference measurement structure (1), and calibrating the distance between the two endpoints of the scale (4) under standard temperature conditions to obtain a scale calibration value; Step 4, selecting multiple time periods from the overall measurement calibration period, selecting multiple measurement times within each time period, taking the surface temperature of the reference measurement structure (1) at the compensation station (5) as the reference temperature, calculating the average surface temperature of the reference measurement structure (1) at the four vertices to obtain the instantaneous reference temperature at each measurement time; Step 5, calculating the average of each instantaneous reference temperature within the same time period to obtain the interval reference temperature of each time period; Step 6, taking the interval reference temperature of each time period as the compensation temperature of the measurement calibration, fitting the measurement field coordinate system to obtain the coordinate value of the measurement reference point (2) in each time period; Step 7, calculating the thermal expansion coefficient of the reference measurement structure (1) according to the interval reference temperature of each time period and the distance between the two measurement reference points (2); Step 8, selecting an instantaneous reference temperature at a measurement time, setting a laser tracker at the compensation station (5), arranging the scale (4) on the reference measurement structure (1), and measuring the distance between the two endpoints of the scale (4) multiple times within a set time fluctuation range through the laser tracker, calculating the average of multiple measurements to obtain a scale measurement value; Step 9, calculating the thermal expansion coefficient of the scale (4) according to the standard temperature, the selected instantaneous reference temperature, the scale calibration value, and the scale measurement value; Step 10, calculating the average of the thermal expansion coefficients of the reference measurement structure (1) and the scale (4) to obtain a reference thermal expansion coefficient.

2. The method of claim 1, wherein the large-scale measurement field reference temperature and reference thermal expansion coefficient are determined by, In step 1, the reference measurement structure (1) is a foundation or aircraft process equipment.

3. The method of claim 2, wherein the large-scale measurement field reference temperature and reference thermal expansion coefficient are determined by, In step 3, the distance between the two endpoints of the scale (4) is calibrated when the surface temperature at the center position of the scale (4) is the standard temperature.

4. The method of claim 3, wherein the large-scale measurement field reference temperature and reference thermal expansion coefficient are determined by, In step 4, each measurement time within the same time period has the same time interval.

5. The method of claim 4, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, The time interval is not less than 30 minutes and not more than 2 hours.

6. The method of claim 5, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, In step 7, the thermal expansion coefficient of the reference measurement structure (1) is: alpha j 1 = (L2 j+1 -L2 j ) / [L2 j × (T2 j+1 -T2 j )] α 1 =∑(α j 1 ) / （n）； j=1, 2, …, n; wherein α j 1 is the thermal expansion coefficient of the reference measurement structure for the jth time interval, L2 j+1 is the distance between the two measurement reference points for the j+1th time interval, L2 j is the distance between the two measurement reference points for the jth time interval, T2 j+1 is the interval reference temperature for the j+1th time interval, T2 j is the interval reference temperature for the jth time interval, α 1 is the thermal expansion coefficient of the reference measurement structure, n is the number of time intervals.

7. The method of claim 6, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, In step 8, the scale (4) is arranged on the reference measurement structure (1) in the following manner: The scale (4) is arranged along the length direction of the measurement field, with the compensation station (5) as the symmetric center, offset by a set distance in the width direction of the measurement field, and the two endpoints of the scale (4) and the compensation station (5) form an isosceles triangle, and the set distance is not more than 2m.

8. The method of claim 7, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, In step 8, the time fluctuation range is not more than 10 minutes.

9. The method of claim 8, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, In step 9, the thermal expansion coefficient of the scale (4) is: a 2 = (L1 1 -L1) / [L1 x (T1 i -T1)]; i=1, 2, …, k; Wherein, α 2 is the thermal expansion coefficient of the scale, L1 1 is the measured value of the scale, L1 is the calibrated value of the scale, T1 i is the selected instantaneous reference temperature at the i th measurement time, T1 is the standard temperature, and k is the number of measurement times.

10. The method of claim 9, wherein the large-scale metrology field reference temperature and reference thermal expansion coefficient are determined by, The method further comprises the following steps: Step 11, selecting a measurement station (3) on the reference measurement structure (1), fitting a measurement field coordinate system based on the interval reference temperature and the reference thermal expansion coefficient of each time period.

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