Three-coordinate measuring machine error identification method and system, medium and product

Abstract

The invention discloses a three-coordinate measuring machine error identification method and system, a medium and a product. The method comprises the following steps: acquiring measurement coordinates of a standard ball in a space diagonal movement process in a preset body space, and establishing an error equation of influence caused by a measuring head error and an error value formed by a polynomial coefficient of a geometric error and a perpendicularity error in each measurement position; after the error equation is expanded, neglecting a second-order small quantity to construct a linear equation set in a matrix form of a plurality of measurement positions; and subtracting the linear equations of the adjacent measurement positions in the matrix form to obtain the linear equations of the adjacent measurement positions in the matrix form, thereby decoupling the influence caused by the measuring head error and obtaining an error value formed by the polynomial coefficient of the geometric error and the perpendicularity error as well as the geometric error and the perpendicularity error. The invention aims to simply and reliably realize accurate identification of the geometric error of the three-coordinate measuring machine so as to realize accurate compensation of the geometric error of the three-coordinate measuring machine.

Description

Technical Field

[0001] The present invention relates to the technical field of error compensation of a three-coordinate measuring machine, and in particular to an error identification method, system, medium and product of a three-coordinate measuring machine. Background Art

[0002] The three-dimensional coordinate measuring machine is a highly efficient precision measuring system with the characteristics of high precision, fast measuring speed and strong adaptability. It plays a vital role in modern production and manufacturing as well as in the fields of aviation and aerospace, and is an indispensable basic measuring equipment in the field of advanced manufacturing. In addition, it also plays a key role in the quality inspection and control of the civil industry. It can measure the three-dimensional coordinates of the geometric elements, curves and surfaces of various parts in space, and supports online inspection and automated measurement. With the advancement of science and technology and the development of ultra-precision machining technology, the measurement accuracy requirements of three-dimensional coordinate measuring machines are constantly increasing. Quickly and accurately calibrating the three-dimensional coordinate measuring machine, detecting and compensating its errors is an important method to improve its measurement accuracy, and it is also a cost-effective technical means. The three-dimensional coordinate measuring machine has three mutually perpendicular axes, each of which has six basic errors: three linear displacement errors and three angular errors, plus the verticality error between the three axes, a total of 21 geometric error sources. The detection methods of geometric errors can be divided into two categories: one is the direct method, which uses instruments such as laser interferometers to directly detect the individual geometric errors of the coordinate measuring machine; the other is the indirect method, which uses ball arrays, ball plates, etc. to detect the comprehensive motion errors of the coordinate measuring machine, and then decomposes the original geometric errors. Directly measuring single geometric errors with laser interferometers can detect these error values ​​with high accuracy. The disadvantage is that laser interferometers are expensive, have high requirements on environmental conditions and the technical level of operators, and cannot detect all 21 geometric errors. Physical benchmarks such as ball arrays and ball plates are placed in multiple positions to reverse the individual errors, but physical benchmarks such as ball plates and ball arrays include sphericity errors, probe errors, calibration errors, etc. during the measurement process. Some benchmarks need to be identified regularly and cannot meet the needs of higher precision measurement. From the above analysis, it can be seen that there is currently no very simple and reliable method for error identification of three-dimensional coordinate measuring machines. For this reason, error identification of three-dimensional coordinate measuring machines is still a hot topic of research. Summary of the invention

[0003] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a three-coordinate measuring machine error identification method, system, medium and product are provided. The present invention aims to simply and reliably realize the accurate identification of the geometric errors of the three-coordinate measuring machine, so as to realize the precise compensation of the geometric errors of the three-coordinate measuring machine.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A three-coordinate measuring machine error identification method comprises the following steps: S1, obtaining the measurement coordinates of the standard ball at multiple measurement positions by the three-dimensional coordinate measuring machine probe during the spatial diagonal movement of the standard ball in the preset body space, and establishing an error equation for each measurement position including the influence of the probe error and the error value composed of the polynomial coefficient of the geometric error and the verticality error; S2, after expanding the error equation, ignore the second-order small quantity to construct a linear equation system in matrix form, and combine multiple measurement positions to obtain a linear equation system in matrix form for multiple measurement positions: S3, subtracting the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of the plurality of measurement positions to obtain the matrix-form linear equations of the differences of adjacent measurement positions, so that the radius of the standard sphere R The influence caused by the probe error is offset as a "common mode input" to decouple the influence caused by the probe error, and an error value composed of the polynomial coefficient of the geometric error and the squareness error as well as the geometric error and the squareness error is obtained.

[0005] Optionally, the function expression of the error equation in step S1 is: , In the above formula, is the measurement coordinate of the coordinate measuring machine, The nominal coordinate position of the center of a known standard sphere, is a known error value, is the radius of the known standard sphere, is the spatial motion error composed of geometric error and verticality error, The influence of the probe error, are the angles between the normal direction and the x, y, and z coordinate axes, respectively, and remain unchanged during the diagonal movement in space, and: , , , in, , , , , and They are the six geometric errors about the x-axis, , , , , and They are the six geometric errors about the y-axis, , , , ,and They are the six geometric errors about the z-axis, are three constant verticality errors, is the probe coordinate.

[0006] Optionally, step S2 includes: S2.1, expand the error equation and ignore the second-order small quantity to obtain the error equation shown in the following formula: , S2.2, after expanding and ignoring the second-order small quantity, the error equation is constructed into a linear equation in the matrix form shown below: , In the above formula, is the error value composed of the polynomial coefficients of the geometric error and the perpendicularity error, A is the Jacobian matrix, , B is the data value on the right side of the error equation after expansion and neglecting the second-order small quantity; S2.3, multiple measurement positions are combined to obtain a linear equation system in matrix form for multiple measurement positions: , In the above formula, ~ are the Jacobian matrices of the N positions of the standard ball during its diagonal movement in the preset volume space, ~ They are respectively the data values ​​on the right side of the error equation corresponding to the N positions of the standard ball in the process of spatial diagonal movement in the preset volume space after the second-order small quantity is ignored after expansion.

[0007] Optionally, step S3 includes: S3.1, subtract the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of multiple measurement positions to obtain the matrix-form linear equations of the differences between adjacent measurement positions: , S3.2, according to the linear equation system in the form of matrix of adjacent measurement position differences, the error value composed of the polynomial coefficients of geometric error and perpendicularity error is obtained , and obtain the geometric error and verticality error.

[0008] Optionally, the geometric error is a cubic polynomial, so that the error value composed of the polynomial coefficient of the geometric error and the perpendicularity error is It includes 54 polynomial coefficients of 18 geometric errors and 3 constant verticality errors, totaling 57 parameters to be solved.

[0009] Optionally, after step S3, the step further includes substituting the obtained geometric error and verticality error into the error equation to obtain the right side of the error equation: , combined with the radius of the standard sphere Get the impact of probe error ; Impact on probe error The probe error distribution in continuous space is obtained through surface fitting or neural network modeling learning.

[0010] Optionally, the standard ball is a standard ball with a nanometer-level sphericity error level, and the standard ball is made of microcrystalline glass material. The preparation of the standard ball includes: polishing the standard ball made of microcrystalline glass material, and then measuring the nanometer-level sphericity error of the standard ball by laser wavefront interferometer, if the nanometer-level sphericity error does not meet the requirements, continuing to polish the standard ball made of microcrystalline glass material until the nanometer-level sphericity error meets the requirements.

[0011] In addition, the present invention also provides a three-coordinate measuring machine error identification system, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the three-coordinate measuring machine error identification method.

[0012] In addition, the present invention also provides a computer-readable storage medium, in which a computer program or instruction is stored. The computer program or instruction is programmed or configured to execute the three-coordinate measuring machine error identification method through a processor.

[0013] In addition, the present invention also provides a computer program product, including a computer program or instructions, wherein the computer program or instructions are programmed or configured to execute the three-coordinate measuring machine error identification method through a processor.

[0014] Compared with the prior art, the present invention can mainly achieve the following beneficial effects: the present invention obtains the measurement coordinates of the standard ball during the spatial diagonal movement in the preset body space through the three-dimensional coordinate measuring machine and establishes the error equation shown in the following formula, expands the error equation and ignores the second-order small quantity to construct the matrix form of linear equations shown in the following formula, subtracts the adjacent positions in the matrix form of linear equations of N positions, and obtains the matrix form of linear equations of the adjacent differences of N positions, so that the radius of the standard ball RThe influence caused by the probe error is offset as a "common mode input", thereby decoupling the influence caused by the probe error. Due to the increase in the amount of data at multiple positions and the more complex distribution, the problem of the Jacobian matrix lacking rank can be solved, so that the geometric error of the three-dimensional coordinate measuring machine can be accurately identified simply and reliably, so as to realize the precise compensation of the geometric error of the three-dimensional coordinate measuring machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the basic flow of the method of the embodiment of the present invention.

[0016] Figure 2 Schematic diagram of the structure of a three-dimensional coordinate measuring machine in an embodiment of the present invention.

[0017] Figure 3 Schematic diagram of translation measurement of a standard ball in an embodiment of the present invention.

[0018] Figure 4 Schematic diagram of the spatial diagonal movement process in an embodiment of the present invention.

[0019] Figure 5 1 is the setting result of the spatial motion error in the embodiment of the present invention, where (a) is the spatial motion error in the x-axis direction, (b) is the spatial motion error in the y-axis direction, and (c) is the spatial motion error in the z-axis direction.

[0020] Figure 6 1 is the identification result of the spatial motion error in the embodiment of the present invention, where (a) is the spatial motion error in the x-axis direction, (b) is the spatial motion error in the y-axis direction, and (c) is the spatial motion error in the z-axis direction. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0022] like Figure 1 As shown, the coordinate measuring machine error identification method of this embodiment includes the following steps: S1, obtaining the measurement coordinates of the standard ball at multiple measurement positions by the three-dimensional coordinate measuring machine probe during the spatial diagonal movement of the standard ball in the preset body space, and establishing an error equation for each measurement position including the influence of the probe error and the error value composed of the polynomial coefficient of the geometric error and the verticality error; S2, after expanding the error equation, ignore the second-order small quantity to construct a linear equation system in matrix form, and combine multiple measurement positions to obtain a linear equation system in matrix form for multiple measurement positions: S3, subtracting the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of the plurality of measurement positions to obtain the matrix-form linear equations of the differences of adjacent measurement positions, so that the radius of the standard sphere R The influence caused by the probe error is offset as a "common mode input" to decouple the influence caused by the probe error, and an error value composed of the polynomial coefficient of the geometric error and the squareness error as well as the geometric error and the squareness error is obtained.

[0023] Since the FXYZ type three-dimensional coordinate measuring machine with a movable bridge structure is a classic structure among three-dimensional coordinate measuring machines, in this embodiment, Figure 2 The FXYZ three-dimensional coordinate measuring machine with a movable bridge structure shown in the figure is taken as the object for analysis. The base of the three-dimensional coordinate measuring machine is provided with a movable bridge that can move along the X-axis direction and is equipped with an X-grating ruler (used to detect displacement in the X-axis direction). The movable bridge is provided with a Y-slider that can slide along the Y direction and a corresponding Y-grating ruler (used to detect displacement in the Y-axis direction). The Y-slider is provided with a measuring column that can move along the Z direction and a corresponding grating ruler (Z-grating ruler, used to detect displacement in the Z-axis direction). During processing, the workpiece is located on the base of the three-dimensional coordinate measuring machine. Through the movement and adjustment of the movable bridge, Y-slider and measuring column, the spatial diagonal movement of the standard ball in the preset body space can be realized. Figure 2 As shown in the figure, four coordinate systems, OXYZ and O, are established on the four relatively moving parts of the base, mobile bridge, Y-slider and measuring column. i X i Y i Z i (i=1,2,3), when the four relatively moving parts are at the origin, it is assumed that the origins of the four coordinate systems coincide with the coordinate axes. For the probe, it is not at the origin and is 3 X 3 Y 3 Z 3 The coordinate system has coordinates ( x p , y p , z p ), this coordinate is determined by the measuring machine structure and the Z-axis grating ruler position. When the moving bridge moves a certain distance in the X direction x , It is expressed as the displacement error along the X, Y, and Z axes when the X axis moves. Then this displacement ( ) can be expressed as follows: , (1) remember is the angular error around the X, Y, and Z axes when the X axis moves. Then the rotation matrix during the movement along the X axis is It can be expressed as follows: , (2) According to the small angle assumption, the angle errors generated during the translation process are all small angle errors, so equation (2) can be written as: , (3) Similarly, the translation can be obtained , , the rotation matrix during movement along the X axis and the rotation matrix during movement along the X axis .

[0024] When the probe tip P( x p , y p , z p ) along the X, Y and Z axes respectively x , y , z If the measuring machine has no geometric errors, the probe will move to P ideal ( x+x p , y+y p , z+z p ). However, under the influence of geometric errors, the probe stylus tip will move to P error ( x', y', z' ). Therefore, P ideal and P error The difference between E ( Δx, Δy, Δz ). In order to obtain the position P in the coordinate system OXYZ error , we will get P in O 3 X 3 Y 3 Z 3 , O 2 X 2 Y 2 Z 2 , O 1 X 1 Y 1 Z 1 Position in O 3 X 3 Y 3 Z 3 The position of O 3 P stands for: , (4) Then, there are two steps to obtain the stylus tip P in coordinate system O. 2 X 2 Y 2 Z 2 The first step is O 3 X 3 Y 3 Z 3 The three axes rotate to 2 X 2 Y 2 Z 2 The three axes are parallel, and the second step is the origin O 3 Move to the origin O 2 Therefore, P is in the coordinate system O 2 X 2 Y 2 Z 2 The position in can be defined as: , (5) Among them, the matrix O 2 O 3 is the linear motion matrix for translation along the Z axis, matrix R( z ) is the rotation matrix during the Z-axis translation process, There are three constant verticality errors. They are expressed as follows: , (6) , (7) Similarly, in order to obtain the coordinate system O 1 X 1 Y 1 Z 1 In the position of P, place O 2 X 2 Y 2 Z 2 The three coordinate axes are rotated to 1 X 1 Y 1 Z 1 The three axes are parallel, and the origin O 2 Move to the origin O 1 Therefore, P in the coordinate system O 1 X 1 Y 1 Z 1 The position in can be expressed as: , (8) Among them, the matrix O 1 O 2 is the linear motion matrix for translation along the Y axis, matrix R(y ) is the rotation matrix during the Y-axis translation process. It is expressed by equation (9) and equation (10) respectively: , (9) , (10) Similarly, in order to obtain the position of P in the coordinate system OXYZ, replace O 1 X 1 Y 1 Z 1 The three coordinate axes of OXYZ are rotated to be parallel to the three axes of OXYZ, and the origin O 1 Move to coincide with the origin O. Therefore, the position of P in the coordinate system OXYZ can be expressed as: , (11) Matrix OO 1 and the matrix R( x ) are respectively expressed by equation (1) and equation (3). Substituting equations (1)-(10) into equation (11), we can obtain: , (12) In the above geometric error model, for the convenience of analysis, it is assumed that the straightness error and angle error of each motion axis are functions of the corresponding displacement (x, y, z), and the corresponding polynomial can be used to fit each single error. In this embodiment, a cubic polynomial is used to fit the geometric error, and the six geometric errors of the single axis are parameterized as follows, taking the X axis as an example: , (13) Similarly, the motion errors of the Y-axis and Z-axis can be parameterized according to equation (13), so that the three constant vertical errors are added. There are 57 parameters to be solved. That is, in this embodiment, the geometric error is a cubic polynomial, so that the error value composed of the polynomial coefficient of the geometric error and the verticality error is It includes 54 polynomial coefficients of 18 geometric errors and 3 constant verticality errors, totaling 57 parameters to be solved.

[0025] In this embodiment, the standard ball is a standard ball with a nanometer-level sphericity error level. The standard ball is made of microcrystalline glass material. Compared with the standard ball made of traditional ceramic material, the advantage is that the standard ball made of microcrystalline glass material can obtain extremely high or even nanometer-level sphericity error by modern polishing technology, and its ball diameter can be directly measured by laser wavefront interferometer to achieve high measurement accuracy. As an optional embodiment, the preparation of the standard ball in this embodiment includes: polishing the standard ball made of microcrystalline glass material, and then measuring the nanometer-level sphericity error of the standard ball by laser wavefront interferometer. If the nanometer-level sphericity error does not meet the requirements, the standard ball made of microcrystalline glass material is polished until the nanometer-level sphericity error meets the requirements.

[0026] like Figure 3 As shown, assuming that the nominal coordinate position of the center of the high-precision standard ball is (can be obtained by fitting the initial measurement data), the error value is , the sum of the radius of the measuring sphere and the radius of the standard sphere is R , the spatial motion error is .like Figure 4 As shown, in this embodiment, the measurement coordinates of the standard ball at multiple measurement positions are obtained by the three-dimensional coordinate measuring machine probe during the spatial diagonal movement of the standard ball in the preset volume space, that is, the measurement coordinates of multiple three-dimensional coordinate measuring machines. , the function expression of the error equation in step S1 of this embodiment is: , (14) In the above formula, is the measurement coordinate of the coordinate measuring machine, The nominal coordinate position of the center of a known standard sphere, is a known error value, is the radius of the known standard sphere, is the spatial motion error composed of geometric error and verticality error, The influence of the probe error, are the angles between the normal direction and the x, y, and z coordinate axes, respectively, and remain unchanged during the diagonal movement in space, such as Figure 3 As shown, there are: , (15) , (16) , (17) in, , , , , and They are the six geometric errors about the x-axis, , , , , and They are the six geometric errors about the y-axis, , , , ,and They are the six geometric errors about the z-axis, are three constant verticality errors, is the probe coordinate.

[0027] In this embodiment, step S2 includes: S2.1, expand the error equation and ignore the second-order small quantity to obtain the error equation shown in the following formula: , (18) S2.2, after expanding and ignoring the second-order small quantity, the error equation is constructed into a linear equation in the matrix form shown below: , (19) In the above formula, is the error value composed of the polynomial coefficients of the geometric error and the perpendicularity error, A is the Jacobian matrix, , B is the data value on the right side of the error equation after expansion and ignoring the second-order small quantity; however, there are still two problems in solving the above equations: the error of the probe is coupled in the measurement data during actual measurement, which makes it impossible to solve the equations; since only the data at one position of the sphere is measured, the distribution of the measurement data is relatively simple, which will lead to the Jacobian matrix in the above formula A Lack of rank, unable to obtain accurate In view of the above problems, this embodiment proposes a method of diagonal movement of a standard ball space to identify geometric error parameters, such as Figure 4 As shown, the standard spheres are evenly distributed on the diagonal of the identified volume space. At the initial position, the normal angle of the measurement area on the sphere surface is determined. The measurement area of ​​the subsequent position is consistent with it, which is designed to make the radius of the standard sphere R The influence caused by the probe error is cancelled as a "common mode input" to decouple the influence caused by the probe error; S2.3, multiple measurement positions are combined to obtain a linear equation system in matrix form for multiple measurement positions: , (20) In the above formula, ~ are the Jacobian matrices of the N positions of the standard ball during its diagonal movement in the preset volume space, ~ They are respectively the data values ​​on the right side of the error equation corresponding to the N positions of the standard ball in the process of spatial diagonal movement in the preset volume space after the second-order small quantity is ignored after expansion.

[0028] In this embodiment, step S3 includes: S3.1, subtract the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of multiple measurement positions to obtain the matrix-form linear equations of the differences between adjacent measurement positions: ,(twenty one) Combining equations (18) and (20) and observing equation (21), we can find that in the data on the right side of equation (21), the radius R Influence of probe error As the "common mode input" is offset, the proposed method can decouple the influence of the probe error. Due to the increase in the amount of data at multiple positions and the complex distribution, the Jacobian matrix can be solved. A The problem of lack of order; S3.2, according to the linear equation system in the form of matrix of adjacent measurement position differences, the error value composed of the polynomial coefficients of geometric error and perpendicularity error is obtained , and obtain the geometric error and verticality error.

[0029] When the error identification is completed, the distribution of the spatial motion error can be generated for error compensation. As an optional implementation, after step S3, the present embodiment further includes substituting the obtained geometric error and verticality error into the error equation to obtain the right side of the error equation , combined with the radius of the standard sphere Get the impact of probe error ; Impact on probe error The probe error distribution in continuous space is obtained through surface fitting or neural network modeling learning.

[0030] In order to verify the error identification method of the three-dimensional coordinate measuring machine in this embodiment, the error identification method of the three-dimensional coordinate measuring machine in this embodiment is simulated and the results are as follows: Figure 5 and Figure 6 shown. Figure 5 The figure shows the spatial motion error distribution (100×100×100mm range) caused by 21 geometric errors in the simulation setting. The measurement data is obtained by measuring the angular position of the standard ball, and its error parameters are obtained according to the error identification model. Figure 6The figure shows the three-dimensional space motion error distribution obtained by synthesizing the error parameters obtained by the error identification method of the three-dimensional coordinate measuring machine in this embodiment. Figure 5 and Figure 6 By comparison, it can be seen that the coordinate measuring machine error identification method of this embodiment can well identify the distribution of spatial errors, can easily and reliably realize accurate identification of the geometric errors of the coordinate measuring machine, and provide a good foundation for subsequent error compensation.

[0031] In addition, the present invention also provides a three-coordinate measuring machine error identification system, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute the three-coordinate measuring machine error identification method.

[0032] In addition, the present invention also provides a computer-readable storage medium, in which a computer program or instruction is stored. The computer program or instruction is programmed or configured to execute the three-coordinate measuring machine error identification method through a processor.

[0033] In addition, the present invention also provides a computer program product, including a computer program or instructions, wherein the computer program or instructions are programmed or configured to execute the three-coordinate measuring machine error identification method through a processor.

[0034] Those skilled in the art should understand that the technical solutions provided by the embodiments of the present application may be in the form of methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0035] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A coordinate measuring machine error identification method, characterized in that: The steps include: S1, obtaining the measurement coordinates of the standard ball at multiple measurement positions by the three-dimensional coordinate measuring machine probe during the spatial diagonal movement of the standard ball in the preset body space, and establishing an error equation for each measurement position including the influence of the probe error and the error value composed of the polynomial coefficient of the geometric error and the verticality error; S2, after expanding the error equation, ignore the second-order small quantity to construct a linear equation system in matrix form, and combine multiple measurement positions to obtain a linear equation system in matrix form for multiple measurement positions: S3, subtracting the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of the plurality of measurement positions to obtain the matrix-form linear equations of the differences of adjacent measurement positions, so that the radius of the standard sphere R The influence caused by the probe error is offset as a "common mode input" to decouple the influence caused by the probe error, and an error value composed of the polynomial coefficient of the geometric error and the squareness error as well as the geometric error and the squareness error is obtained.

2. The error identification method of a three-dimensional coordinate measuring machine according to claim 1, characterized in that: The functional expression of the error equation in step S1 is: ， In the above formula, is the measurement coordinate of the coordinate measuring machine, The nominal coordinate position of the center of a known standard sphere, is a known error value, is the radius of the known standard sphere, is the spatial motion error composed of geometric error and verticality error, The influence of the probe error, are the angles between the normal direction and the x, y, and z coordinate axes, respectively, and remain unchanged during the diagonal movement in space, and: ， ， ， in, , , , , and They are the six geometric errors about the x-axis, , , , , and They are the six geometric errors about the y-axis, , , , ,and They are the six geometric errors about the z-axis, are three constant verticality errors, is the probe coordinate.

3. The error identification method of a three-dimensional coordinate measuring machine according to claim 2, characterized in that: Step S2 includes: S2.1, expand the error equation and ignore the second-order small quantity to obtain the error equation shown in the following formula: ， S2.2, after expanding and ignoring the second-order small quantity, the error equation is constructed into a linear equation in the matrix form shown below: ， In the above formula, is the error value composed of the polynomial coefficients of the geometric error and the perpendicularity error, A is the Jacobian matrix, , B is the data value on the right side of the error equation after expansion and neglecting the second-order small quantity; S2.3, multiple measurement positions are combined to obtain a linear equation system in matrix form for multiple measurement positions: ， In the above formula, ~ are the Jacobian matrices of the N positions of the standard ball during its diagonal movement in the preset volume space, ~ They are respectively the data values ​​on the right side of the error equation corresponding to the N positions of the standard ball in the process of spatial diagonal movement in the preset volume space after the second-order small quantity is ignored after expansion.

4. The error identification method of a three-dimensional coordinate measuring machine according to claim 3, characterized in that: Step S3 includes: S3.1, subtract the matrix-form linear equations of adjacent measurement positions from the matrix-form linear equations of multiple measurement positions to obtain the matrix-form linear equations of the differences between adjacent measurement positions: ， S3.2, according to the linear equation system in the form of matrix of adjacent measurement position differences, the error value composed of the polynomial coefficients of geometric error and perpendicularity error is obtained , and obtain the geometric error and verticality error.

5. The error identification method of a three-dimensional coordinate measuring machine according to claim 4, characterized in that: The geometric error is a cubic polynomial, so that the error value composed of the polynomial coefficient of the geometric error and the verticality error is It includes 54 polynomial coefficients of 18 geometric errors and 3 constant verticality errors, totaling 57 parameters to be solved.

6. The error identification method of a three-dimensional coordinate measuring machine according to claim 2, characterized in that: After step S3, the obtained geometric error and verticality error are substituted into the error equation to obtain the right side of the error equation. , combined with the radius of the standard sphere Get the impact of probe error ; Impact on probe errors The probe error distribution in continuous space is obtained through surface fitting or neural network modeling learning.

7. The error identification method of a three-dimensional coordinate measuring machine according to claim 1, characterized in that: The standard ball is a standard ball with a nanometer-level sphericity error level. The standard ball is made of microcrystalline glass material, and the preparation of the standard ball includes: polishing the standard ball made of microcrystalline glass material, and then measuring the nanometer-level sphericity error of the standard ball by laser wavefront interferometer. If the nanometer-level sphericity error does not meet the requirements, continue to polish the standard ball made of microcrystalline glass material until the nanometer-level sphericity error meets the requirements.

8. A coordinate measuring machine error identification system, comprising a microprocessor and a memory connected to each other, characterized in that: The microprocessor is programmed or configured to execute the coordinate measuring machine error identification method according to any one of claims 1 to 7.

9. A computer-readable storage medium having a computer program or instruction stored therein, characterized in that: The computer program or instruction is programmed or configured to execute the coordinate measuring machine error identification method according to any one of claims 1 to 7 through a processor.

10. A computer program product comprising a computer program or instructions, characterized in that The computer program or instruction is programmed or configured to execute the coordinate measuring machine error identification method according to any one of claims 1 to 7 through a processor.

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