A parameter self-calibration method for spatial triangle long-length laser measurement system

Abstract

The invention relates to the field of measurement technology, and discloses a parameter self-calibration method for a space triangle long-length laser measurement system, comprising the following steps: arranging three independent laser interferometers into a space triangle to measure three parallel lights, and introducing a fourth laser interferometer to calibrate the displacement values ​​of the three independent laser interferometers to obtain a displacement value formula of the same-light-path interferometers; calculating the displacement error formula of the same-light-path interferometers and the fourth laser interferometer; obtaining the displacement values ​​of the three independent laser interferometers and the fourth laser interferometer at n measurement points, and constructing an objective function to be optimized; optimizing the objective function to be optimized by using a nonlinear least square method, and obtaining optimal system parameters and the coordinates of the fourth laser interferometer; the method solves the problem of difficulty in measuring the side lengths and coordinates of multiple laser interferometers, and simultaneously improves the measurement accuracy of the space triangle long-length laser measurement system.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, and in particular to a parameter self-calibration method for a space triangle large-length laser measurement system. Background Art

[0002] The long-length laser measurement system can be composed of a single laser interferometer or two, three or more laser interferometers. The standard instrument uses a single laser interferometer as the standard instrument. The measured optical path and the standard optical path adopt a parallel and symmetrical optical path to minimize the Abbe error, but due to environmental factors, the single interferometer has limited improvement on the accuracy of the measuring device. If two laser interferometers are used as standard instruments. The optical paths of these interferometers are symmetrically arranged with the optical paths of the measured object and maintained on the same horizontal plane, thereby eliminating the Abbe errors of the guide rail in the horizontal and vertical directions. However, the measurement structure of the two laser interferometers cannot eliminate or correct the Abbe errors in the vertical and horizontal directions at the same time. If the measurement results of the three-way laser interferometer are used to eliminate the Abbe error, the Abbe error is eliminated through the measurement results of the three-way interferometer and the geometric relationship between the measured instrument and the installation position of the three-way interferometer. However, the system parameters of the spatial triangle laser measurement device, that is, the side length of the triangle composed of the laser interferometers, still affect the accuracy of the measurement system.

[0003] In the daily inspection process, a large number of inspection tasks need to be carried out, and the laser optical path needs to be adjusted at any time, and the position of the instrument will inevitably change. If instruments such as laser trackers are required to measure the position of the laser interferometer every time, the inspection efficiency will be seriously affected. Even if the inspectors measure the coordinate parameters of the interferometer, the accuracy of the measurement needs to be verified. If a standard ruler is used to measure the position coordinates of the laser interferometer, if the interferometer position measurement is inaccurate, for example, the length of each side differs by 3mm, it will cause the measurement result and the calculated result to have an error of more than 0.6μm. In summary, the above method has the defects of difficulty in measuring the side lengths and coordinates of multiple interferometers and low measurement accuracy. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a parameter self-calibration method for a spatial triangle long-length laser measurement system, which is used to solve the problems of difficulty and low accuracy in measuring the side lengths and coordinates of multiple interferometers in the prior art, while improving the measurement accuracy.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A parameter self-calibration method for a spatial triangle long-length laser measurement system comprises the following steps:

[0007] S1. Arrange three independent laser interferometers into a spatial triangle to measure three parallel lights, and introduce a fourth laser interferometer to calibrate the displacement values ​​of the three independent laser interferometers to obtain the displacement value formula of the interferometers on the same optical path;

[0008] The spatial triangle long-length laser measurement system is composed of three independent laser interferometers. According to the three-point coplanar theorem and the fourth laser interferometer is on this plane, a same-optical-path interferometer with the same optical path as the fourth laser interferometer is constructed by combining the three independent laser interferometers. The three independent laser interferometers are standard instruments for the spatial triangle long-length laser measurement system, and the fourth laser interferometer is a laser ranging instrument for the spatial triangle long-length laser measurement system.

[0009] S2. Calculate the displacement error formula between the interferometer on the same optical path and the fourth laser interferometer according to the displacement value formula of the interferometer on the same optical path;

[0010] S3, based on the displacement error formula of the interferometer on the same optical path and the fourth laser interferometer, obtain the displacement error of the three independent laser interferometers and the fourth laser interferometer The displacement values ​​at the measurement points are used to construct the objective function to be optimized;

[0011] S4, using the nonlinear least square method to optimize the objective function to be optimized, and obtaining the optimal system parameters and the coordinates of the fourth laser interferometer;

[0012] Among them, the system parameter is the side length of the space triangle.

[0013] Furthermore, the displacement value formula of the same optical path interferometer in step S1 is:

[0014]

[0015] in, represents the displacement value of the interferometer in the same optical path, , , Respectively represent three independent laser interferometers , , The displacement value of , They represent the fourth laser interferometer Axis coordinates, Axis coordinates, , , They represent the side lengths of the spatial triangle, that is, the distances between the three independent laser interferometers.

[0016] Furthermore, the displacement error formula of the same optical path interferometer and the fourth path laser interferometer in step S2 is:

[0017]

[0018] in, It represents the displacement error between the interferometer on the same optical path and the laser interferometer on the fourth optical path. Indicates the displacement value of the fourth laser interferometer.

[0019] Furthermore, step S3 specifically includes:

[0020] S31. Based on the displacement error formula of the same optical path interferometer and the fourth laser interferometer, To move items, we have:

[0021]

[0022] in, Indicates the error between three independent laser interferometers and the fourth laser interferometer;

[0023] S32, based on , obtain the three independent laser interferometers and the fourth laser interferometer in the The displacement value of each measuring point is:

[0024]

[0025] in, Indicates that the three independent laser interferometers and the fourth laser interferometer are in the The error of the measurement points, , , Respectively represent three independent laser interferometers , , In the The displacement value of each measuring point, Indicates that the same optical path interferometer is Displacement value of each measuring point;

[0026] S33, based on three independent laser interferometers and the fourth laser interferometer The displacement values ​​of the three independent laser interferometers and the fourth laser interferometer are obtained. The displacement values ​​of the measurement points are used to construct the objective function to be optimized, namely:

[0027]

[0028] in, Represents the objective function to be optimized.

[0029] Furthermore, step S4 specifically includes:

[0030] S41, setting upper and lower bounds of unknown parameters in the objective function to be optimized, setting initial guess values ​​of the unknown parameters based on the upper and lower bounds as the starting point of the objective function to be optimized, and setting the number of iterations and the tolerance of the objective function to be optimized;

[0031] Among them, the unknown parameters are the system parameters and the coordinates of the fourth laser interferometer;

[0032] S42, based on the set upper and lower bounds of the unknown parameters, the number of iterations, and the tolerance of the objective function to be optimized, the initial guess value of the unknown parameter, the three-way independent laser interferometer , , exist The displacement value of the measurement point and the fourth laser interferometer The displacement values ​​of the measurement points are used as the input of the nonlinear least square method to optimize the objective function to be optimized;

[0033] S43, calculating the calculated value of the objective function to be optimized in the first iteration;

[0034] S44, calculating the calculated value of the objective function to be optimized during the second iteration;

[0035] S45, performing a difference process on the calculated value of the objective function to be optimized in the second iteration and the calculated value of the objective function to be optimized in the first iteration to obtain a difference value;

[0036] S46, determine whether the difference is less than the set threshold, if so, obtain the optimal system parameters and the coordinates of the fourth laser interferometer, otherwise, add 1 to the number of iterations and repeat steps S43-S46.

[0037] The present invention has the following beneficial effects:

[0038] The present invention proposes a parameter self-calibration method for a spatial triangle long-length laser measurement system. By constructing an objective function to be optimized and using a nonlinear least squares method to perform optimization and solution, the optimal system parameters and the coordinates of a fourth laser interferometer are obtained. The optimal system parameters and the coordinates of the fourth laser interferometer can be used to calculate the displacement values ​​of three independent laser interferometers, i.e., a standard instrument, thereby solving the problem of difficulty in measuring the side lengths and coordinates of multiple laser interferometers and improving the measurement accuracy of the spatial triangle long-length laser measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic flow chart of a parameter self-calibration method for a spatial triangle long-length laser measurement system proposed by the present invention;

[0040] Figure 2 It is a schematic diagram of the structure of the spatial triangle long-length laser measurement system;

[0041] Figure 3 In the embodiment, the measuring surface and , Schematic diagram of the angle error of the surface;

[0042] Figure 4 is the error of the 80m measurement range when the fourth laser interferometer is inside the space triangle;

[0043] Figure 5 is the error of the 80m measurement range when the fourth laser interferometer is outside the spatial triangle. DETAILED DESCRIPTION

[0044] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0045] like Figure 1 As shown, a parameter self-calibration method for a spatial triangle long-length laser measurement system includes the following steps S1-S4:

[0046] S1. Arrange three independent laser interferometers into a spatial triangle to measure three parallel lights. At the same time, introduce a fourth laser interferometer to calibrate the displacement values ​​of the three independent laser interferometers to obtain the displacement value formula of the interferometer with the same optical path.

[0047] In this embodiment, the spatial triangle long-length laser measurement system is composed of three independent laser interferometers. According to the three-point coplanarity theorem and the fourth laser interferometer is on this plane, the three independent laser interferometers are combined to construct an interferometer with the same optical path as the fourth laser interferometer. The three independent laser interferometers are standard instruments for the spatial triangle long-length laser measurement system, and the fourth laser interferometer is a laser ranging instrument for the spatial triangle long-length laser measurement system. In addition, the coordinate positions of the three independent laser interferometers need to be accurately measured. The reason is that if the coordinate positions of the three independent laser interferometers are inaccurate, it will cause a large deviation between the measurement results and the calculation results. Therefore, improving the measurement accuracy of the coordinate positions of the three independent laser interferometers can improve the accuracy and reliability of the measurement and calculation results. At the same time, in this embodiment, the coordinate position of the fourth laser interferometer does not need to be accurately measured. The reason is that the coordinate position of the fourth laser interferometer is optimized in subsequent steps as a parameter to be optimized, that is, in the parameter self-calibration method of the spatial triangle long-length laser measurement system, in addition to optimizing the unknown parameters (system parameters) of the spatial triangle long-length laser measurement system, it is also necessary to optimize the coordinates of the fourth laser interferometer.

[0048] like Figure 2 As shown, Figure 2 It is a schematic diagram of the structure of the spatial triangle long-length laser measurement system; Figure 2 middle It is a three-way independent laser interferometer. is the coordinate of the fourth laser interferometer involved in the calibration, , , are the distances between the three independent laser interferometers, i.e., the spatial triangle , , The length of the side, , , , They are the measurement starting positions of the three independent laser interferometers and the fourth laser interferometer. , , Three independent laser interferometers , , The displacement value of is the displacement value of the fourth laser interferometer, is the displacement value of the same optical path interferometer constructed with three independent laser interferometers, , , are the displacement end points of three independent laser interferometers, is the displacement end point of the fourth laser interferometer; according to the above parameters, the cosine theorem has: , for Angle, and at the measurement starting position, The point coordinates are , The point coordinates are , The point coordinates are ;because , , are in the same plane, then the plane The three-point equation is: ,in , , Represents the three-dimensional coordinate system coordinate, , , They represent the displacement end points of the first independent laser interferometer. coordinate, , , respectively represent the displacement end point of the second independent laser interferometer coordinate, , , They represent the displacement end points of the third independent laser interferometer. Coordinates; Since the point In plane On, we have: ; By solving the above two equations, we can get the displacement value formula of the interferometer with the same optical path.

[0049] Specifically, the displacement value formula of the same optical path interferometer in step S1 is:

[0050]

[0051] in, represents the displacement value of the interferometer in the same optical path, , , Respectively represent three independent laser interferometers , , The displacement value of , They represent the fourth laser interferometer Axis coordinates, Axis coordinates, , , They represent the side lengths of the spatial triangle, that is, the distances between the three independent laser interferometers.

[0052] S2. According to the displacement value formula of the same optical path interferometer, calculate the displacement error formula between the same optical path interferometer and the fourth laser interferometer.

[0053] In this embodiment, the displacement error between the interferometer on the same optical path and the fourth laser interferometer is the system Abbe error, that is, when the displacement error between the interferometer on the same optical path and the fourth laser interferometer is 0 or close to 0, the system error is minimum. Therefore, the displacement error formula between the interferometer on the same optical path and the fourth laser interferometer shows that when the side length of the space triangle, i.e., the distance between the three independent laser interferometers and the length of the fourth laser interferometer, is equal to Axis coordinates, The more accurate the axis coordinates are, the closer the displacement values ​​of the interferometer on the same optical path and the fourth laser interferometer are to zero. At this time, the optimal parameters can be obtained, that is, the side length of the optimal space triangle, that is, the distance between the three independent laser interferometers and the fourth laser interferometer. Axis coordinates, Axis coordinates.

[0054] Specifically, the displacement error formula of the same optical path interferometer and the fourth path laser interferometer in step S2 is:

[0055]

[0056] in, It represents the displacement error between the interferometer on the same optical path and the laser interferometer on the fourth optical path. Indicates the displacement value of the fourth laser interferometer.

[0057] S3, based on the displacement error formula of the interferometer on the same optical path and the fourth laser interferometer, obtain the displacement error of the three independent laser interferometers and the fourth laser interferometer The displacement values ​​at the measurement points are used to construct the objective function to be optimized.

[0058] In this embodiment, the three independent laser interferometers and the fourth laser interferometer are obtained. The purpose of the displacement values ​​at the measuring points is: since the parameter self-calibration of the spatial triangle long-length laser measurement system contains 5 unknown parameters, in principle only 5 equations, that is, 5 measuring points, are needed. However, the displacement values ​​of the three independent laser interferometers and the fourth laser interferometer at the 5 measuring points are different due to the influence of the linearity of the long guide rail. Therefore, it is impossible to determine that the displacement values ​​of the three independent laser interferometers and the fourth laser interferometer at the 5 measuring points are different. Therefore, in order to ensure the accuracy and reliability of the optimization, it is necessary to select a number of measuring points greater than 5.

[0059] Specifically, step S3 specifically includes S31-S33:

[0060] S31. Based on the displacement error formula of the same optical path interferometer and the fourth laser interferometer, To move items, we have:

[0061]

[0062] in, Represents the error between three independent laser interferometers and the fourth laser interferometer.

[0063] S32, based on , obtain the three independent laser interferometers and the fourth laser interferometer in the The displacement value of each measuring point is:

[0064]

[0065] in, Indicates that the three independent laser interferometers and the fourth laser interferometer are in the The error of the measurement points, , , Respectively represent three independent laser interferometers , , In the The displacement value of each measuring point, Indicates that the same optical path interferometer is The displacement value of each measuring point.

[0066] S33, based on three independent laser interferometers and the fourth laser interferometer The displacement values ​​of the three independent laser interferometers and the fourth laser interferometer are obtained. The displacement values ​​of the measurement points are used to construct the objective function to be optimized, namely:

[0067]

[0068] in, Represents the objective function to be optimized.

[0069] In this embodiment, theoretically, when Therefore, in order to obtain the optimal system parameters and the coordinates of the fourth laser interferometer, when the nonlinear least squares method is used for optimization in the subsequent steps, the function value of the objective function to be optimized is made to approach region 0 as much as possible, so as to obtain the optimal system parameters and the coordinates of the fourth laser interferometer.

[0070] S4. The objective function to be optimized is optimized by using a nonlinear least square method to obtain the optimal system parameters and the coordinates of the fourth laser interferometer; wherein the system parameters are the side lengths of the space triangle.

[0071] In this embodiment, during the specific operation, after the initial conditions are set, the LM algorithm (Levenberg-Marquardt algorithm) in the nonlinear least squares method is used for optimization.

[0072] Specifically, step S4 specifically includes S41-S46:

[0073] S41. Set the upper and lower bounds of the unknown parameters in the objective function to be optimized, and set the initial guess values ​​of the unknown parameters based on the upper and lower bounds as the starting point of the objective function to be optimized, and set the number of iterations and the tolerance of the objective function to be optimized; wherein the unknown parameters are the system parameters and the coordinates of the fourth laser interferometer.

[0074] S42, based on the set upper and lower bounds of the unknown parameters, the number of iterations, and the tolerance of the objective function to be optimized, the initial guess value of the unknown parameter, the three-way independent laser interferometer , , exist The displacement value of the measurement point and the fourth laser interferometer The displacement values ​​of the measurement points are used as the input of the nonlinear least squares method to optimize the objective function to be optimized.

[0075] S43, calculating the calculated value of the objective function to be optimized in the first iteration.

[0076] S44. Calculate the calculated value of the objective function to be optimized in the second iteration.

[0077] S45, performing a difference process on the calculated value of the objective function to be optimized in the second iteration and the calculated value of the objective function to be optimized in the first iteration to obtain a difference value.

[0078] S46, determine whether the difference is less than the set threshold, if so, obtain the optimal system parameters and the coordinates of the fourth laser interferometer, otherwise, add 1 to the number of iterations and repeat steps S43-S46.

[0079] In this embodiment, a simulation experiment is conducted based on a measurement process design model of a spatial triangle long-length laser measurement system to verify the effectiveness of a parameter self-calibration method for a spatial triangle long-length laser measurement system proposed in the present invention, as follows:

[0080] The spatial triangle long-length laser measurement system model was established using MATLAB software, in which the outgoing lasers of three independent laser interferometers and the fourth laser interferometer were represented by four parallel straight lines (such as Figure 2 In , , , ), the starting points of the straight line are the four points representing the laser interferometer (such as Figure 2 In , , , ); Since the parameter self-calibration method proposed in the present invention requires taking measurement points at different positions within the measurement range, 19 non-parallel measurement surfaces are generated at different positions of the model, wherein the angles of each surface are as follows: Figure 3 As shown, Figure 3 Middle Angle with horns The measuring surface and noodle, Surface angle, each measuring surface is equivalent to a measuring point. When the four straight lines of the emitted laser pass through each measuring surface, they intersect with the measuring surface to form a line-surface intersection point. Each point is the displacement value of each laser interferometer at this measuring point. Substitute the measured displacement value into the objective function to be optimized to obtain the optimal system parameters and the coordinates of the fourth laser interferometer.

[0081] Among them, the optimized parameters, i.e. the optimal system parameters, the coordinates of the fourth laser interferometer, the measurement parameters and the parameters before optimization are shown in Table 1:

[0082] Table 1 Comparison of optimized parameters

[0083]

[0084] From Table 1, we can see that the error before optimization is [-0.51μm, 0.43μm], and the average error is -0.69μm; the error after optimization is [-0.003μm, 0.005μm], and the average error is 0.0007μm. Therefore, the error is significantly reduced after optimization, indicating the effectiveness of the parameter self-calibration method proposed in the present invention.

[0085] In addition, a fourth laser interferometer was used to conduct experiments on the inside and outside of the spatial triangle. The inside experiment and the outside experiment were conducted three times each. The motion range of the motion platform in the experiment was from 0mm to 80000mm. For both the inside and outside experiments, 28 measurement points were taken within the motion range of the motion platform in the first experiment. The measured values ​​were used as the displacement values ​​of each laser interferometer, and the motion platform remained stationary at each measurement point. Substituting the displacement values ​​of the four-channel laser interferometers into the self-calibration method proposed in the present invention, the system parameters of the inside and outside can be optimized, that is, the side length of the spatial triangle and the coordinate parameters of the fourth laser interferometer. The second and third experiments on the inside and outside were respectively used as verification experiments. In the verification experiment, the optimized system parameters were used to re-take measurement points in the motion range. The measured values ​​were used as the displacement values ​​of each interferometer. The interferometer displacement values ​​and the system parameters optimized in the first experiment were substituted into the formula: ,Mode The displacement error of the same optical path interferometer and the fourth path laser interferometer participating in the parameter self-calibration method is calculated;

[0086] In this embodiment, the experimental results of the fourth laser interferometer on the inner and outer sides of the space triangle are as follows: Figure 4-Figure 5 As shown, Figure 4 is the error of the 80m measurement range when the fourth laser interferometer is inside the space triangle, Figure 5 is the error of the 80m measurement range when the fourth laser interferometer is outside the space triangle. Figure 4 and Figure 5 In the parameters The error of the first group of parameters before optimization, parameter is the error calculated for the first group of optimized parameters, parameters is the error of the second group of parameters before optimization, parameter is the error of the second group of optimized parameters. is the error of the parameter calculation before the third group of optimization, parameter is the error calculated for the third group of optimized parameters. Figure 4 It can be seen that within the 80m measurement range, when the fourth laser interferometer participating in the self-calibration method is on the inner side of the spatial triangle, the maximum errors of the three groups of experiments are reduced from 2.49μm, 2.60μm, and 2.57μm to 0.59μm, 0.75μm, and 0.63μm, respectively, using the optimized system parameters and the coordinates of the fourth laser interferometer. This significantly reduces the error within the measurement range and improves the accuracy of the spatial triangle large-length laser measurement system. Figure 5It can be seen that within the measurement range of 80m, when the fourth laser interferometer participating in the self-calibration method is outside the spatial triangle, the maximum errors of the three groups of experiments are reduced from 4.01μm, 3.46μm, and 3.61μm to 1.62μm, 1.39μm, and 1.79μm, respectively, using the optimized system parameters and the coordinates of the fourth laser interferometer. This significantly reduces the error within the measurement range and improves the accuracy of the large-length laser measurement system for spatial triangles.

[0087] In summary, the parameter self-calibration method of a spatial triangle long-length laser measurement system proposed in the present invention constructs an objective function to be optimized and optimizes the objective function to be optimized using a nonlinear least squares method to obtain the optimal system parameters and the coordinates of the fourth laser interferometer. This method can not only obtain system parameter information in real time, but also improve the measurement accuracy of the spatial triangle long-length laser measurement system and solve the problem of residual Abbe error existing in the spatial triangle long-length laser measurement system.

[0088] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0089] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A parameter self-calibration method for a spatial triangle long-length laser measurement system, characterized in that: The following steps are involved: S1. Arrange three independent laser interferometers into a spatial triangle to measure three parallel lights, and introduce a fourth laser interferometer to calibrate the displacement values ​​of the three independent laser interferometers to obtain the displacement value formula of the interferometers on the same optical path; The spatial triangle long-length laser measurement system is composed of three independent laser interferometers. According to the three-point coplanar theorem and the fourth laser interferometer is on this plane, a same-optical-path interferometer with the same optical path as the fourth laser interferometer is constructed by combining the three independent laser interferometers. The three independent laser interferometers are standard instruments for the spatial triangle long-length laser measurement system, and the fourth laser interferometer is a laser ranging instrument for the spatial triangle long-length laser measurement system. S2. Calculate the displacement error formula between the interferometer on the same optical path and the fourth laser interferometer according to the displacement value formula of the interferometer on the same optical path; S3, based on the displacement error formula of the interferometer on the same optical path and the fourth laser interferometer, obtain the displacement error of the three independent laser interferometers and the fourth laser interferometer The displacement values ​​at the measurement points are used to construct the objective function to be optimized; S4, using the nonlinear least square method to optimize the objective function to be optimized, and obtaining the optimal system parameters and the coordinates of the fourth laser interferometer; Among them, the system parameter is the side length of the space triangle.

2. The parameter self-calibration method of the spatial triangle long-length laser measurement system according to claim 1 is characterized in that: The displacement formula of the interferometer with the same optical path in step S1 is: in, represents the displacement value of the interferometer in the same optical path, , , Respectively represent three independent laser interferometers , , The displacement value of , They represent the fourth laser interferometer Axis coordinates, Axis coordinates, , , They represent the side lengths of the spatial triangle, that is, the distances between the three independent laser interferometers.

3. The parameter self-calibration method of the spatial triangle long-length laser measurement system according to claim 2 is characterized in that: The displacement error formula of the interferometer on the same optical path and the fourth laser interferometer in step S2 is: in, represents the displacement error between the interferometer on the same optical path and the fourth laser interferometer, Indicates the displacement value of the fourth laser interferometer.

4. The parameter self-calibration method of the spatial triangle long-length laser measurement system according to claim 3 is characterized in that: Step S3 specifically includes: S31. Based on the displacement error formula of the same optical path interferometer and the fourth laser interferometer, To move items, we have: in, Indicates the error between three independent laser interferometers and the fourth laser interferometer; S32, based on , obtain the three independent laser interferometers and the fourth laser interferometer in the The displacement value of each measuring point is: in, Indicates that the three independent laser interferometers and the fourth laser interferometer are in the The error of the measurement points, , , Respectively represent three independent laser interferometers , , In the The displacement value of each measuring point, Indicates that the same optical path interferometer is Displacement value of each measuring point; S33, based on three independent laser interferometers and the fourth laser interferometer The displacement values ​​of the three independent laser interferometers and the fourth laser interferometer are obtained. The displacement values ​​of the measurement points are used to construct the objective function to be optimized, namely: in, Represents the objective function to be optimized.

5. The parameter self-calibration method of the spatial triangle long-length laser measurement system according to claim 4 is characterized in that: Step S4 specifically includes: S41, setting upper and lower bounds of unknown parameters in the objective function to be optimized, setting initial guess values ​​of the unknown parameters based on the upper and lower bounds as the starting point of the objective function to be optimized, and setting the number of iterations and the tolerance of the objective function to be optimized; Among them, the unknown parameters are the system parameters and the coordinates of the fourth laser interferometer; S42, based on the set upper and lower bounds of the unknown parameters, the number of iterations, and the tolerance of the objective function to be optimized, the initial guess value of the unknown parameter, the three-way independent laser interferometer , , exist The displacement value of the measurement point and the fourth laser interferometer The displacement values ​​of the measurement points are used as the input of the nonlinear least square method to optimize the objective function to be optimized; S43, calculating the calculated value of the objective function to be optimized in the first iteration; S44, calculating the calculated value of the objective function to be optimized during the second iteration; S45, performing a difference process on the calculated value of the objective function to be optimized in the second iteration and the calculated value of the objective function to be optimized in the first iteration to obtain a difference value; S46, determine whether the difference is less than the set threshold, if so, obtain the optimal system parameters and the coordinates of the fourth laser interferometer, otherwise, add 1 to the number of iterations and repeat steps S43-S46.

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