On-machine measurement method for geometric error of three-axis numerical control machine tool based on feature sample pose transformation

Abstract

A three-axis numerical control machine tool geometric error on-machine measurement method based on feature sample piece pose transformation comprises the steps that feature sample pieces are designed, feature point sets are planned, after accurate calibration, the feature sample pieces are placed on a machine tool workbench for on-machine measurement, and by measuring feature points of combinations of different poses of the feature sample pieces on a machine tool, a geometric error on-machine measurement result is obtained. And establishing a plurality of identification models aiming at different types of geometric error terms, and quickly identifying all 21 geometric errors of the three-axis machine tool. According to the method, the geometric error can be quickly measured without precise measuring equipment or instrument, the numerical control program for measuring the feature points of the sample piece can be repeatedly used for a long time after being compiled, the measurement efficiency of the geometric error is greatly improved, and the method can be used for quickly and efficiently performing periodic recheck detection and precision calibration on the machine tool.

Description

Technical Field

[0001] The present invention relates to a technology in the field of three-axis CNC machine tools, in particular to an on-machine measurement method for geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation. Background Art

[0002] There are 21 geometric errors in three-axis machine tools. Currently, laser interferometers are usually used to directly or indirectly measure these geometric errors. The equipment installation and debugging is time-consuming and laborious, and requires a certain level of professional measurement operation. It is difficult to achieve automated measurement, and the overall measurement efficiency is low. The existing technology can only identify nine linear motion errors of the XYZ axis, and the error compensation accuracy of machine tool motion needs to be improved. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes an on-machine measurement method for the geometric errors of three-axis CNC machine tools based on the position and posture transformation of characteristic samples. The geometric errors can be measured quickly without the need for precise measuring equipment or instruments. Once the CNC program for measuring the characteristic points of the sample is compiled, it can be reused for a long time. While greatly improving the measurement efficiency of the geometric errors, it can identify the angular errors of the linear axes of the three-axis CNC machine tools, including the pitch, yaw and roll errors in the three directions of XYZ, as well as the verticality error between the XYZ axes, thereby greatly improving the compensation accuracy of the spatial errors of the machine tools.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to an on-machine measurement method for geometric errors of a three-axis CNC machine tool based on the position and posture transformation of a feature sample. The feature sample is designed and a feature point group is planned. After accurate calibration, the feature sample is placed on a machine tool workbench for on-machine measurement. By measuring the combined feature points of the feature sample at different positions and postures on the machine tool, a plurality of identification models for different types of geometric error items are established, and all 21 geometric errors of the three-axis machine tool are quickly identified.

[0006] The characteristic sample is a type of metal product with multiple steps and the steps have at least one ascending direction.

[0007] The feature point group is a point group to be measured when identifying 21 geometric errors, specifically including:

[0008] ① Positioning error identification point group, that is, the combination of points on different step surfaces on the characteristic sample;

[0009] ② Straightness error identification point group, that is, equidistant characteristic points distributed on a straight line on the same step surface of the characteristic sample;

[0010] ③ Angle error point group, that is, the combination of characteristic points distributed on multiple straight lines on multiple step surfaces of the characteristic sample;

[0011] ④Verticality error point group, that is, the combination of characteristic points distributed on two straight lines on two step surfaces.

[0012] The on-machine measurement refers to: directly connecting the probe to the spindle of the three-axis CNC machine tool, and measuring the parts directly on the machine tool workbench by moving the spindle of the three-axis CNC machine tool together with the probe.

[0013] The total of 21 geometric errors include: 1 positioning error, 2 straightness errors, 3 angular errors, and perpendicularity errors between the three translation axes. For example, for the x-axis, there is 1 positioning error δ xx , 2 straightness errors δ yx and δ zx , 3 angle errors: pitch angle error ε yx , the yaw angle error ε zx , roll angle error ε xx And the perpendicularity error S between the x-axis and the y-axis xy .

[0014] The combination of different postures means that according to the zero position of the machine tool table coordinate system, different postures of the sample on the machine tool table correspond to different types of geometric errors, that is, the 7 characteristic samples placed on the table posture correspond to the identification of 21 geometric errors, specifically including: pos1 corresponds to the x-axis positioning error δ xx and z-axis positioning error δ zz , pos2 corresponds to the straightness error ε of the x-axis in the z-direction zx , the straightness error of the x-axis in the y-direction ε yx , the verticality error S between the x-axis and the y-axis xy , x-axis runout error ε zx 、z-axis pitch error ε yz and z-axis runout error ε xz , pos3 corresponds to the x-axis rolling error ε xx and y-axis positioning error δ yy , pos4 corresponds to the straightness error δ of the y-axis in the z-direction zy , the straightness error of the y-axis in the x-direction δ xy and y-axis runout error ε zy , pos5 corresponds to the y-axis rolling error ε yy , pos6 corresponds to the x-axis pitch error ε yx , z-axis straightness error in x direction δ xz , the verticality error S between the x-axis and the z-axis xz , the straightness error of the z-axis in the y direction δyz and z-axis roll error ε zz , pos7 corresponds to the y-axis pitch error ε xy and the perpendicularity error S between the y-axis and the z-axis yz , where: pos1, pos2, pos3, pos4, pos5, pos6 and pos7 are the positions of the first to seventh feature samples placed on the workbench respectively.

[0015] The identification models include: a positioning error identification model, a straightness error identification model, a pitch angle error identification model, a yaw angle error identification model, a roll angle error identification model and a verticality error identification model.

[0016] The positioning error identification model specifically refers to: x-axis positioning error Y-axis positioning error z-axis positioning error Where: P xi ,P yi ,P zi is the distance between the step surface in the x, y, and z directions of the characteristic sample and the reference step surface measured at the characteristic point on the machine, p xi ,p yi ,p zi is the calibration value of the distance between the step surface and the reference step surface in the x, y, and z directions, For x = x i ,y=y i , z=z i The corresponding positioning error when the coordinate position is measured.

[0017] The straightness error identification model specifically refers to: the x-axis in the y direction and the z direction are respectively The y-axis is in the x-direction and the z-direction respectively. The z-axis is in the x-direction and the y-direction respectively Among them: STRA xi,y The feature points distributed on a straight line during machine measurement are fitted into the reference line in the x direction. The distance between the feature points and the reference line in the y direction, and the rest are similar; xi,y Fit the same feature point to the reference line in the x direction, and calibrate the distance between the feature point and the reference line in the y direction. The rest is similar. For x = x i The straightness error in the y direction corresponding to the coordinate position, and the rest are similar.

[0018] The pitch angle error identification model specifically refers to: x-axis pitch error Y-axis pitch error Z-axis pitch error Among them: the characteristic points linearly distributed on multiple step surfaces measured by the machine are fitted with multiple straight lines perpendicular to the x direction. The straight line corresponding to the zero point of the coordinate is the reference straight line, and the angle between other straight lines and the reference straight line around the y axis is PITC xi,y , the rest is similar; the same feature points are fitted into multiple straight lines perpendicular to the x-direction, and the calibration value of the angle between other straight lines and the reference straight line rotated around the y-axis is pitc xi,y , the rest is similar; For x = x i ,y=y i or z=z i The pitch angle error corresponding to the coordinate position.

[0019] The deflection angle error identification model specifically refers to: x-axis deflection error Y-axis runout error z-axis runout error Among them: the linearly distributed feature points on the multiple step surfaces measured by the machine are fitted into multiple straight lines perpendicular to the x direction, the straight line corresponding to the coordinate zero point is the reference straight line, and the angle between other straight lines and the reference straight line around the z axis is YAW xi,z , the rest is similar; the same feature point is fitted to multiple straight lines perpendicular to the x direction, and the calibration value of the angle between other straight lines and the reference straight line around the z axis is yaw xi,z , the rest is similar; For x = x i ,y=y i or z=z i The yaw angle error corresponding to the coordinate position. The principle of the yaw angle error identification model is similar to that of the pitch angle error identification model, but in essence, the feature points required by the former and the latter are different feature point combinations, and the direction of the fitting line and the direction of the rotation axis are also different.

[0020] The roll angle error identification model specifically refers to: x-axis roll error Y-axis rolling error Z-axis rolling error Where: Δz xi,y＝h For x = x i , at the coordinate position of y=h, the difference between the measured value and the calibrated value of the point in the z direction, and the rest is similar; For x = x i ,y=y i or z=z i The roll angle error corresponding to the coordinate position.

[0021] The verticality error identification model specifically refers to: S xy=angle+K1-K2-pi / 2, where: K1=arctank1, K2=arctank2, k1, k2 are the slopes of the straight line fitted by the feature points in the x-axis and y-axis directions, angle is the calibration value of the angle between the straight lines fitted by the same feature points in the x-axis and y-axis directions, S xy is the perpendicularity error between the x-axis and the y-axis. yz and S xz The verticality error identification method is similar to S xy . Technical Effects

[0022] Compared with the existing three-axis machine tool geometric error measurement method, the present invention considers using feature samples after accurate calibration, planning multiple groups of feature points on different step surfaces of the sample, and measuring these different combinations of feature points on the machine in different directions and lengths by performing posture transformation on the sample on the machine tool workbench, and establishing an identification model for all 21 geometric errors of the three-axis machine tool, thereby quickly and efficiently measuring the geometric errors. Compared with the existing method, this method does not require high-precision measuring equipment and instruments, thereby eliminating the time for installing and debugging instruments. Once the CNC program for measuring the feature points of the sample is compiled, it can be reused for a long time. Compared with identifying partial geometric errors to compensate for the position accuracy of the machine tool, the present invention can quickly identify all 21 geometric errors of the three-axis machine tool while greatly improving the accuracy of the machine tool spatial error compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the present invention;

[0024] Figure 2 A schematic diagram of the geometric errors included in the machine tool under test in the embodiment;

[0025] Figure 3 A schematic diagram of a characteristic sample in the embodiment;

[0026] Figure 4 Schematic diagram of different placement positions of characteristic samples on the machine tool workbench in the embodiment;

[0027] Figure 5-Figure 11 Schematic diagram of feature points required for on-machine measurement of geometric error terms corresponding to pos1-pos7 postures in the embodiment;

[0028] Fig.12 Schematic diagram of a pitch angle error identification model in an embodiment;

[0029] Fig.13 It is a schematic diagram of a yaw angle error identification model in an embodiment;

[0030] Fig.14 Schematic diagram of a roll angle error identification model in an embodiment;

[0031] Fig.15 It is a schematic diagram of a verticality error identification model in an embodiment;

[0032] Figure 16-Figure 18 They are schematic diagrams of on-machine measurement results of x-, y-, and z-axis geometric errors in the embodiments;

[0033] Fig.19 This is a diagram showing the effect of machine tool geometric error identification and machine tool error compensation in the embodiment;

[0034] Fig. 20 This is a diagram showing the effect of error measurement and compensation in the embodiment;

[0035] Fig.21 This is a scene diagram of the detection of the embodiment. DETAILED DESCRIPTION

[0036] like Figure 1 As shown, this embodiment involves an on-machine measurement method for geometric errors of a three-axis CNC machine tool based on the position and posture transformation of a feature sample, including: designing multiple groups of feature points corresponding to different geometric error terms on the planning surface of the feature sample, and accurately calibrating the feature points of the sample; compiling a CNC on-machine measurement program according to the planned feature points; transforming the different positions of the feature sample on the machine tool workbench to execute the measurement program to obtain feature point coordinate data; establishing an identification model for different geometric error terms, and obtaining all 21 geometric errors of the three-axis machine tool, specifically including:

[0037] The first step is to design multiple groups of feature points on the surface of the feature sample corresponding to different geometric error terms. Different combinations of feature points correspond to 21 geometric errors, and the feature points of the sample are accurately calibrated.

[0038] like Figure 2 As shown in the figure, the 21 geometric errors are error indicators that reflect the geometric motion accuracy of the three translation axes of the three-axis machine tool, specifically including: each translation axis has 1 positioning error, 2 straightness errors, and 3 angle errors. For example, for the x-axis, there is 1 positioning error δ xx , 2 straightness errors, δ yx and δ zx , 3 angle errors: pitch angle error ε yx , the yaw angle error ε zx , roll angle error ε xx ; There is a vertical error between the three translation axes, such as the vertical error S between the x-axis and the y-axis xy .

[0039] like Figure 3 As shown, the characteristic sample is a type of metal product with multiple steps, and the steps have more than one ascending direction.

[0040] The multiple groups of feature points correspond to the point groups to be measured during the identification of 21 geometric errors. Specifically, the point group required for positioning error identification is a combination of points on different step surfaces on the feature sample; the point group required for straightness error identification is an equidistant feature point distributed on a straight line on the same step surface of the feature sample; the point group required for angle error is a combination of feature points distributed on multiple straight lines on multiple step surfaces of the feature sample; the point group required for verticality error is a combination of feature points distributed on two straight lines on two step surfaces. Figure 6 Different geometric error terms corresponding to the linear geometric error and angular geometric error are shown.

[0041] The second step is to compile a NC program based on the planned feature points for on-machine measurement;

[0042] The on-machine measurement is to connect the probe directly to the machine tool spindle, and then the machine tool motion control system drives the spindle and the probe to move together, so that the parts are measured directly on the machine tool workbench.

[0043] The third step is to change the different postures of the characteristic sample on the machine tool workbench to execute the measurement program and obtain the coordinate data of the characteristic point;

[0044] like Figure 4 As shown in FIG. 1 , the characteristic sample described in the embodiment is placed in different positions on the machine tool workbench; Figures 5 to 11 As shown, a schematic diagram of different geometric error terms corresponding to different postures described in the embodiment corresponds to pos1 to pos7 respectively.

[0045] The different postures refer to: according to the zero position of the machine tool table coordinate system, different postures of the sample on the machine tool table correspond to different types of geometric errors, including: 7 postures corresponding to the identification of 21 geometric errors, pos1 corresponding to the x-axis positioning error δ xx and z-axis positioning error δ zz ; pos2 corresponds to the straightness error δ of the x-axis in the z-direction zx , the straightness error of the x-axis in the y-direction δ yx , the verticality error S between the x-axis and the y-axis xy , x-axis runout error ε zx 、z-axis pitch error ε yz and z-axis runout error ε xz ;pos3 corresponds to the x-axis rolling error ε xx and y-axis positioning error δ yy ; pos4 corresponds to the straightness error δ of the y-axis in the z-direction zy , the straightness error of the y-axis in the x-direction δ xy and y-axis runout error ε zy ;pos5 corresponds to the y-axis rolling error ε yy; pos6 corresponds to the x-axis pitch error ε yx , z-axis straightness error in x direction δ xz , the verticality error S between the x-axis and the z-axis xz 、The straightness error of z-axis in y direction ε yz and z-axis roll error ε zz ; pos7 corresponds to the y-axis pitch error ε xy and the perpendicularity error S between the y-axis and the z-axis yz Among them: pos1, pos2, pos3, pos4, pos5, pos6 and pos7 are the characteristic samples placed on the workbench position 1, position 2, position 3, position 4, position 5, position 6 and position 7 respectively.

[0046] The fourth step is to establish identification models for different geometric error terms and obtain all 21 geometric errors of the three-axis machine tool.

[0047] The identification models of different geometric error terms are divided into positioning error identification model, straightness error identification model, pitch angle error identification model, yaw angle error identification model, roll angle error identification model and verticality error identification model.

[0048] The positioning error identification model, x-axis positioning error Y-axis positioning error z-axis positioning error Where: P xi ,P yi ,P zi is the distance between the step surface in the x, y, and z directions of the characteristic sample and the reference step surface measured at the characteristic point on the machine, p xi ,p yi ,p zi is the calibration value of the distance between the step surface and the reference step surface in the x, y, and z directions, For x = x i ,y=y i , z=z i The corresponding positioning error when the coordinate position is measured.

[0049] The straightness error identification model described above has the x-axis in the y-direction and the z-direction respectively. The y-axis is in the x-direction and the z-direction respectively. The z-axis is in the x-direction and the y-direction respectively Among them: STRA xi,yThe feature points distributed on a straight line during machine measurement are fitted into the reference line in the x direction. The distance between the feature points and the reference line in the y direction, and the rest are similar; xi,y Fit the same feature point to the reference line in the x direction, and calibrate the distance between the feature point and the reference line in the y direction. The rest is similar. For x = x i The straightness error in the y direction corresponding to the coordinate position, and the rest are similar.

[0050] like Fig.12 As shown, the x-axis pitch angle error identification model, the x-axis pitch error Y-axis pitch error Z-axis pitch error Among them: the characteristic points linearly distributed on multiple step surfaces measured by the machine are fitted with multiple straight lines perpendicular to the x direction. The straight line corresponding to the zero point of the coordinate is the reference straight line, and the angle between other straight lines and the reference straight line around the y axis is PITC xi,y , the rest is similar; the same feature points are fitted into multiple straight lines perpendicular to the x-direction, and the calibration value of the angle between other straight lines and the reference straight line rotated around the y-axis is pitc xi,y , the rest is similar; For x = x i ,y=y i or z=z i The pitch angle error corresponding to the coordinate position.

[0051] like Fig.13 As shown, the x-axis deflection angle error identification model, the x-axis deflection error Y-axis runout error z-axis runout error Among them: the linearly distributed feature points on the multiple step surfaces measured by the machine are fitted into multiple straight lines perpendicular to the x direction, the straight line corresponding to the coordinate zero point is the reference straight line, and the angle between other straight lines and the reference straight line around the z axis is YAW xi,z , the rest is similar; the same feature point is fitted to multiple straight lines perpendicular to the x direction, and the calibration value of the angle between other straight lines and the reference straight line around the z axis is yaw xi,z , the rest is similar; For x = x i ,y=y i or z=z i The yaw angle error corresponding to the coordinate position. The principle of the yaw angle error identification model is similar to that of the pitch angle error identification model, but in essence, the feature points required by the former and the latter are different feature point combinations, and the direction of the fitting line and the direction of the rotation axis are also different.

[0052] like Fig.14 As shown, the x-axis roll angle error identification model, the x-axis roll error Y-axis rolling error Z-axis rolling error Where: Δz xi,y＝h For x = x i , at the coordinate position of y=h, the difference between the measured value and the calibrated value of the point in the z direction, and the rest is similar; For x = x i ,y=y i or z=z i The roll angle error corresponding to the coordinate position.

[0053] like Fig.16 17a-f, 17a-f, 18a-f show the six geometric errors of the x, y, and z axes identified in this embodiment.

[0054] like Fig.15 As shown, the x-axis and y-axis verticality error identification model, S xy = anlge + K1-K2-pi / 2, where: K1 = arctank1, K2 = arctank2, k1, k2 are the slopes of the straight line fitted by the feature points in the x-axis and y-axis directions, angle is the calibration value of the angle between the straight lines fitted by the same feature points in the x-axis and y-axis directions, S xy is the perpendicularity error between the x-axis and the y-axis. yz and S xz The verticality error identification method is similar to S xy Specifically, the identification result is: S xy =320.59urad, S xz =-88.73urad, S yz =56.39urad.

[0055] Through specific practical experiments, it was found that after the machine tool has run for a period of time, the characteristic sample of the present invention can be placed on the machine tool workbench, and the CNC program that does not need to be modified once compiled can be run in conjunction with the on-machine measuring device to measure the machine tool geometric error. In this way, all 21 geometric errors of the three-axis machine tool can be obtained in a relatively short time, thus preparing for the machine tool precision compensation.

[0056] like Fig.19 As shown, it is a scene picture of on-machine measurement of characteristic samples in the embodiment.

[0057] Compared with the prior art, this method can quickly obtain all 21 geometric errors of a three-axis machine tool. Compared with the method that can only identify some geometric error items, the present invention can improve the accuracy of machine tool error compensation, thereby improving the machining accuracy of the machine tool and ensuring the consistency of part machining quality.

[0058] like Fig. 20 As shown in the figure, it is the effect diagram after error measurement and compensation in this embodiment, wherein the dotted line part represents the result diagram of the machine tool length error measurement after measuring the linear geometric error of some straight axis and compensating it by the prior art, and the solid line part represents the result diagram of the machine tool length measurement error after measuring all machine tool geometric errors including angle errors and compensating them by the measurement method in the present invention, and the length measurement error of the machine tool on the machine is detected on the X, Y and four diagonal lines of the measurement space. After measuring and compensating the error by the method of the present invention, the machine tool length measurement error is greatly reduced, that is, the position accuracy is greatly improved, and the accuracy of compensation is greatly improved.

[0059] like Fig.21 As shown, this is a scene diagram of using a ball bar standard sample to detect the length measurement error of a machine tool after the machine tool geometric error is compensated in this embodiment. The ball bar standard sample is placed on the X, Y and four diagonal lines of the measurement space, and the machine tool is used to measure its length error on the machine. The figure shows a scene diagram when measuring on a certain diagonal line.

[0060] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for measuring geometric errors of three-axis CNC machine tools on-machine based on characteristic sample pose transformation, characterized in that: By designing feature samples and planning feature point groups, the feature samples are placed on the machine tool workbench for on-machine measurement after precise calibration. By measuring the feature points of the feature samples at different positions on the machine tool, multiple identification models for different types of geometric error terms are established to quickly identify all 21 geometric errors of the three-axis machine tool. The characteristic sample is a type of metal product with multiple steps and the steps have at least one ascending direction; The feature point group is a point group to be measured when identifying 21 geometric errors, specifically including: ① Positioning error identification point group, that is, the combination of points on different step surfaces on the characteristic sample; ② Straightness error identification point group, that is, equidistant characteristic points distributed on a straight line on the same step surface of the characteristic sample; ③ Angle error point group, that is, the combination of characteristic points distributed on multiple straight lines on multiple step surfaces of the characteristic sample; ④ The verticality error point group, that is, the combination of characteristic points distributed on two straight lines on two step surfaces; The identification models include: a positioning error identification model, a straightness error identification model, a pitch angle error identification model, a yaw angle error identification model, a roll angle error identification model and a verticality error identification model.

2. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The on-machine measurement refers to: directly connecting the probe to the spindle of the three-axis CNC machine tool, and measuring the parts directly on the machine tool workbench by moving the spindle of the three-axis CNC machine tool together with the probe.

3. The on-machine measurement method for geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The total of 21 geometric errors include: 1 positioning error, 2 straightness errors, 3 angular errors, and perpendicularity errors between the three translation axes. For example, for the x-axis, there is 1 positioning error δ xx , 2 straightness errors δ yx and δ zx , 3 angle errors: pitch angle error ε yx , the yaw angle error ε zx , roll angle error ε xx And the perpendicularity error S between the x-axis and the y-axis xy .

4. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The combination of different postures means that according to the zero position of the machine tool table coordinate system, different postures of the sample on the machine tool table correspond to different types of geometric errors, that is, the 7 characteristic samples placed on the table posture correspond to the identification of 21 geometric errors, specifically including: pos1 corresponds to the x-axis positioning error δ xx and z-axis positioning error δ zz , pos2 corresponds to the straightness error δ of the x-axis in the z-direction zx , the straightness error of the x-axis in the y-direction δ yx , the verticality error S between the x-axis and the y-axis xy , x-axis runout error ε zx 、z-axis pitch error ε yz and z-axis runout error ε xz , pos3 corresponds to the x-axis rolling error ε xx and y-axis positioning error δ yy , pos4 corresponds to the straightness error δ of the y-axis in the z-direction zy , the straightness error of the y-axis in the x-direction δ xy and y-axis runout error ε zy , pos5 corresponds to the y-axis rolling error ε yy , pos6 corresponds to the x-axis pitch error ε yx , z-axis straightness error in x direction δ xz , the verticality error S between the x-axis and the z-axis xz , the straightness error of the z-axis in the y direction δ yz and z-axis roll error ε zz , pos7 corresponds to the y-axis pitch error ε xy and the perpendicularity error S between the y-axis and the z-axis yz , where: pos1, pos2, pos3, pos4, pos5, pos6 and pos7 are the positions of the first to seventh feature samples placed on the workbench respectively.

5. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The positioning error identification model specifically refers to: x-axis positioning error Y-axis positioning error z-axis positioning error Where: P xi ,P yi ,P zi is the distance between the step surface in the x, y, and z directions of the characteristic sample and the reference step surface measured at the characteristic point on the machine, p xi ,p yi ,p zi is the calibration value of the distance between the step surface and the reference step surface in the x, y, and z directions, For x = x i ,y=y i , z=z i The corresponding positioning error when the coordinate position is measured.

6. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The straightness error identification model specifically refers to: the x-axis in the y direction and the z direction are respectively The y-axis is in the x-direction and the z-direction respectively. The z-axis is in the x-direction and the y-direction respectively Among them: S embarrassment RA xi，y The feature points distributed on a straight line during machine measurement are fitted into the reference line in the x direction. The distance between the feature points and the reference line in the y direction, and the rest are similar; xi，y Fit the same feature point to the reference line in the x direction, and calibrate the distance between the feature point and the reference line in the y direction. The rest is similar. For x = x i The straightness error in the y direction corresponding to the coordinate position, and the rest are similar.

7. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The pitch angle error identification model specifically refers to: x-axis pitch error Y-axis pitch error Z-axis pitch error Among them: the characteristic points linearly distributed on multiple step surfaces measured by the machine are fitted with multiple straight lines perpendicular to the x direction. The straight line corresponding to the coordinate zero point is the reference straight line, and the angle between other straight lines and the reference straight line around the y axis is PITC xi，y , the rest is similar; the same feature points are fitted into multiple straight lines perpendicular to the x-direction, and the calibration value of the angle between other straight lines and the reference straight line rotated around the y-axis is pitc xi，y , the rest is similar; For x = x i ,y=y i or z=z i The pitch angle error corresponding to the coordinate position.

8. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1 is characterized in that: The deflection angle error identification model specifically refers to: x-axis deflection error Y-axis runout error z-axis runout error Among them: the linearly distributed feature points on the multiple step surfaces measured by the machine are fitted into multiple straight lines perpendicular to the x direction, the straight line corresponding to the coordinate zero point is the reference straight line, and the angle between other straight lines and the reference straight line around the z axis is YAW xi，z , the rest is similar; the same feature point is fitted to multiple straight lines perpendicular to the x direction, and the calibration value of the angle between other straight lines and the reference straight line around the z axis is yaw xi，z , the rest is similar; For x = x i ,y=y i or z=z i The yaw angle error corresponding to the coordinate position, the principle of the yaw angle error identification model is similar to the principle of the pitch angle error identification model, but in essence the feature points required by the former and the latter are different feature point combinations, and the direction of the fitting line and the direction of the rotation axis are also different.

9. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1, characterized in that: The roll angle error identification model specifically refers to: x-axis roll error Y-axis rolling error Z-axis roll error Where: Δz xi，y＝h For x = x i , at the coordinate position of y=h, the difference between the measured value and the calibrated value of the point in the z direction, and the rest is similar; For x = x i ,y=y i or z=z i The roll angle error corresponding to the coordinate position.

10. The method for measuring geometric errors of three-axis CNC machine tools based on characteristic sample pose transformation according to claim 1, characterized in that: The verticality error identification model specifically refers to: S xy =angle+K1-K2-pi / 2, where: K1=arctank1, K2=arctank2, k1, k2 are the slopes of the straight line fitted by the feature points in the x-axis and y-axis directions, angle is the calibration value of the angle between the straight lines fitted by the same feature points in the x-axis and y-axis directions, S xy is the perpendicularity error between the x-axis and the y-axis, S yz and S xz The verticality error identification method is similar to S xy .

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