Decoupling Method and Measuring Device for Geometric Error and Thermal Error of Rotary Axes of Double Swivel Table Five-Axis Machine Tools

Abstract

The present invention proposes a decoupling method and a measuring device for geometric errors and thermal errors of the rotating axes of a double-turntable five-axis machine tool, belonging to the field of machine tool error detection. The problem of decoupling the geometric errors and thermal errors of the rotating axes of a double-turntable five-axis machine tool is solved by using a variable-angle "S"-shaped specimen. The method includes the following steps: 1) After the machine tool is turned on for 10 minutes, use a probe to measure the coordinate values of the upper and lower wire measurement points on the variable-angle "S"-shaped specimen; 2) After the machine tool is turned on for 0.5 hour, measure the machine tool temperature once every half hour, and measure 4 times in total to obtain the stable temperature change range of the machine tool; 3) Measure the coordinate values of the upper and lower wire measurement points when the machine tool temperature is stably changing; 4) Calculate the corresponding center coordinates of the specimen arc from the measurement points; 5) Substitute the center coordinates into the machine tool geometric error model to obtain the geometric error value, and then compare the theoretical center coordinates with the actual center coordinates to obtain the comprehensive error value; 6) Substitute the obtained comprehensive error value and geometric error value into the comprehensive error decoupling and separation model to obtain the thermal error value of the machine tool.

Description

Technical Field

[0001] The present invention relates to the field of machine tool error detection, and particularly to a decoupling method and measuring device for geometric error and thermal error of a five-axis numerically controlled machine tool. Background Art

[0002] With the continuous innovation of machining technology, five-axis numerically controlled machine tools are increasingly widely used in the machining of complex parts. There are many errors in the machining of parts by five-axis numerically controlled machine tools, and these errors can be mainly divided into: thermal error, geometric error, dynamic cutting force error, servo control error, etc. Geometric error and thermal error have a greater impact on the machining accuracy of the machine tool among several errors. Among them, geometric error is mainly caused by the errors generated during the manufacturing and assembly of machine tool components. There are many geometric error items of the machine tool, and the current research on the geometric error of the machine tool mainly focuses on aspects such as modeling and measurement identification. Thermal error is mainly caused by the thermal deformation generated by machine tool components during operation and the cutting heat generated during the cutting process of the machine tool.

[0003] The measurement of machine tool geometric error is generally divided into direct measurement methods and indirect measurement methods. Direct measurement methods generally use some measuring devices, such as laser interferometers. Indirect measurement methods can indirectly identify geometric errors by using test pieces, and can also measure errors based on laser tracking interferometers and ballbar testers. For the decoupling analysis of machine tool thermal error, generally, a machine tool thermal error model is first established, but the accuracy of the model will directly affect the decoupling accuracy of machine tool thermal error. At present, there is less research on indirectly measuring and decoupling machine tool thermal error by using test pieces.

[0004] Therefore, a decoupling method and measuring device for the geometric error and thermal error of the rotating axes of a double rotary table five-axis machine tool based on a variable-angle "S"-shaped test piece are proposed. The geometric error of the rotating axes of the double rotary table five-axis machine tool can be quickly obtained through the indirect measurement of the "S"-shaped test piece, and then the thermal error of the machine tool can be further obtained by a comprehensive error decoupling model, so as to complete the decoupling of the geometric error and thermal error of the rotating axes of the machine tool. Summary of the Invention

[0005] The purpose of the present invention is to provide a decoupling method and measuring device for the geometric error and thermal error of the rotating axes of a double rotary table five-axis machine tool. By using the indirect measurement of the "S"-shaped test piece, the geometric error and thermal error of the rotating axes of the double rotary table five-axis machine tool are quickly decoupled.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a decoupling method and measuring device for geometric error and thermal error of the rotating axes of a double rotary table five-axis machine tool. First, a stable machine tool temperature change range is measured, and within this change range, the machining error of the machine tool will remain stable; secondly, when the machine tool temperature changes stably, a ruby probe is used to measure the coordinate points of the "S"-shaped specimen to obtain the measurement point data; then, measurement points are selected, and the corresponding center coordinates of the arc of the "S"-shaped specimen are obtained according to the principle of "determining the center of a circle with three points"; thirdly, a decoupling separation model for the geometric error of the machine tool is established, and the center coordinate points are substituted into the geometric error decoupling model of the machine tool to calculate the geometric error value; then, the theoretical center coordinate points are subtracted from the actual center coordinate points to calculate the comprehensive error value; finally, a comprehensive error decoupling separation model is established, and the obtained comprehensive error value and geometric error value are substituted into the comprehensive error decoupling model of the machine tool to obtain the thermal error value of the machine tool.

[0007] A decoupling method and measuring device for geometric error and thermal error of the rotating axes of a double rotary table five-axis machine tool, comprising the following steps:

[0008] Step 1. Turn on the machine tool and immediately measure the coordinate values of all coordinate points on the upper and lower wires of the "S"-shaped specimen;

[0009] Ten minutes after the machine tool starts, immediately measure and record the coordinate points of the specimen. At this time, the heat generated by the operation of the machine tool has a relatively small impact on the overall comprehensive error, and the geometric error accounts for a relatively large proportion.

[0010] Step 2. Measure all coordinate points on the upper and lower wires of the "S"-shaped specimen when the rotating axes A and C rotate at different angles;

[0011] The "S"-shaped specimen has two wires, upper and lower. According to the relevant standards of the "S"-shaped specimen, 50 measurement points are distributed on each of the upper and lower wires, and the specific coordinate positions of the 100 measurement points in total on the upper and lower wires are specified in the standards. When the rotating axis A rotates 0°, 30°, 60°, 90° respectively, and the rotating axis C rotates 0°, 30°, 60°, 90° respectively, measure 100 measurement points on the upper and lower wires of the "S"-shaped specimen in the machine according to the standards.

[0012] Step 3. Select several measurement points, determine the actual center coordinates to obtain the geometric error of the machine tool;

[0013] Select several measurement points from the 100 actual measurement points obtained in Step 2. The specific actual coordinates of 2 centers on each of the upper and lower wires are obtained by the method of determining the center of a circle with three points. Substitute the 4 center coordinates into the geometric error decoupling separation model to calculate the geometric error of the double rotary table five-axis machine tool when the rotating axes A and C rotate at different angles.

[0014] Step 4. Arrange temperature sensors to measure the temperature of the machine tool;

[0015] Four temperature measuring sensors are arranged at the connection of the rotating shaft and the corresponding parts of the machine tool. The specific distribution is as follows: T1, T2, T3, and T4 are respectively placed at the lower edge of the turntable, the left end of the A-axis, and the right end of the A-axis. During the test, the ambient temperature is 20°C. To accurately measure the temperature at each point, the circulating cooling pump of the machine tool is turned off to eliminate the influence of the cutting fluid on the temperature value.

[0016] Step 5. Repeat the measurement of the temperature change of the machine tool to determine the stable temperature change range of the machine tool;

[0017] Measure the temperature of the machine tool once after the machine tool runs for 0.5 hours, 1 hour, 1.5 hours, and 2 hours respectively. After 4 measurements, the stable temperature change range of the machine tool is determined.

[0018] Step 6. Repeat Step 2 and separately record the coordinate values of the coordinate points corresponding to the upper and lower wires of the specimen measured;

[0019] Step 7. Select several measurement points from the 100 actual measurement points obtained in Step 6 to determine the actual center coordinates;

[0020] Step 8. Select the corresponding measurement points from the standard to determine the theoretical center coordinate values;

[0021] Select the measurement points used in Step 6 from the standard accordingly, query the specific theoretical coordinate values of each measurement point, and obtain the theoretical coordinate values of 4 centers by the method of determining the center by three points.

[0022] Step 9. Calculate the comprehensive error of the machine tool;

[0023] Subtract the actual center coordinate values obtained in Step 7 from the theoretical center coordinate values obtained in Step 8 to obtain the comprehensive error of the machine tool. This comprehensive error includes the geometric error and thermal error of the machine tool.

[0024] Step 10. Perform decoupling of the comprehensive error to obtain the thermal error of the machine tool;

[0025] Substitute the geometric error values and the comprehensive error values of the machine tool obtained in the above steps into the machine tool comprehensive error decoupling model for error decoupling calculation to obtain the thermal error of the machine tool.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention indirectly decouples the geometric error and thermal error of the machine tool by measuring the standard "S"-shaped specimen, without the need to use precision and expensive measuring instruments such as laser interferometers and ball bar testers. The decoupling method and measuring device proposed by the present invention are economical and practical and can meet the detection accuracy requirements.

[0028] 2. By using the decoupling method proposed in the present invention, after establishing the machine tool comprehensive error decoupling model and the machine tool geometric error decoupling and separation model, the coordinate values of the actual measurement points are obtained by measuring the "S"-shaped specimen, and the actual center coordinates are calculated through calculation. After substituting the coordinate values into the machine tool comprehensive error decoupling model and the machine tool geometric error decoupling and separation model, the geometric error and thermal error of the machine tool rotation axis can be quickly obtained, and the decoupling process is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart for decoupling the geometric error and thermal error of the rotation axis of a five-axis machine tool with a double swing table based on a single "S"-shaped specimen

[0030] Figure 2 It is a flow chart for measuring the geometric error of the rotation axis of a double swing table five-axis machine tool

[0031] Figure 3 It is a flow chart for constructing virtual center points at the upper and lower wire arcs of a single "S"-shaped specimen

[0032] Figure 4 It is a schematic diagram of the measurement point distribution and area distribution of the "S"-shaped specimen

[0033] 1 - Upper wire of the "S"-shaped specimen, 2 - Measurement points on the upper wire of the "S"-shaped specimen, 3 - Lower wire of the "S"-shaped specimen, 4 - Measurement points on the lower wire of the "S"-shaped specimen, 5 - Constant curvature area of the "S"-shaped specimen, 6 - Variable curvature area of the "S"-shaped specimen, 7 - Non-twisted area of the "S"-shaped specimen, 8 - Twisted area of the "S"-shaped specimen, 9 - Constant curvature area of the "S"-shaped specimen, 10 - Variable curvature area of the "S"-shaped specimen, 11 - Non-twisted area of the "S"-shaped specimen.

[0034] Figure 5 It is a schematic diagram of the center point distribution of the "S"-shaped specimen

[0035] Figure 6 It is a general layout diagram of the measuring device

[0036] 21 - "S"-shaped specimen with variable angle, 22 - Ruby contact probe, 23 - Temperature measurement sensor, 24 - Rotation axis A, 25 - Rotation axis C, 26 - Computer.

[0037] Figure 7 It is a cloud map of the geometric error field distribution of a double swing table five-axis machine tool SPECIFIC EMBODIMENTS

[0038] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0039] As Figure 6As shown in the figure, the decoupling method and measuring device for geometric error and thermal error of the rotary axes of a dual-turntable five-axis machine tool proposed by the present invention include a variable-angle "S"-shaped specimen (21), a ruby contact probe (22), a temperature measuring sensor (23), a rotary axis A (24), a rotary axis C (25), and a computer (26).

[0040] As Figure 1 shown, the decoupling method and measuring device for geometric error and thermal error of the rotary axes of a dual-turntable five-axis machine tool proposed by the present invention include the following steps:

[0041] Step 1. Turn on the machine tool and immediately measure the coordinate values of all coordinate points on the upper and lower wires of the "S"-shaped specimen.

[0042] Ten minutes after the machine tool starts, immediately start measuring and recording the coordinate points of the specimen. At this time, the influence of the heat generated by the operation of the machine tool on the overall comprehensive error is relatively small, and the geometric error accounts for a relatively large proportion.

[0043] Step 2. Measure all coordinate points on the upper and lower wires of the "S"-shaped specimen when the rotary axes A and C rotate at different angles.

[0044] The "S"-shaped specimen has two wires, the upper and the lower. According to the relevant standards of the "S"-shaped specimen, there are 50 measurement points on each of the upper and lower wires, and the specific coordinate positions of a total of 100 measurement points on the upper and lower wires are specified in the standards. When the rotary axis A rotates 0°, 30°, 60°, and 90° respectively, and the rotary axis C rotates 0°, 30°, 60°, and 90° respectively, on-machine measurement of a total of 100 measurement points on the upper and lower wires of the "S"-shaped specimen is carried out according to the standards.

[0045] Step 3. Select several measurement points, determine the actual center coordinates, and obtain the geometric error of the machine tool.

[0046] Select several measurement points from the 100 actual measurement points obtained in Step 2. The specific actual coordinates of 2 centers on each of the upper and lower wires are obtained by the method of determining the center by three points. Substitute the 4 center coordinates into the geometric error decoupling and separation model to calculate the geometric errors of the dual-turntable five-axis machine tool when the rotary axes A and C rotate at different angles.

[0047] Step 3.1 Establish a geometric error decoupling and separation model for the machine tool.

[0048] The five-axis numerical control machine tool includes two rotary axes A and C. Each of the rotary axes A and C includes 2 types of geometric error elements, namely translational error and angular error. The translational error includes 3 error elements, and the angular error also includes 3 error elements. Therefore, each of the two rotary axes A and C includes 6 geometric error elements, as shown in Table 1 specifically:

[0049] Table 1. Geometric error elements of A and C rotation axes

[0050]

[0051] According to the coordinate transformation relationship between the moving axes of the machine tool, using X, Y, and Z to represent the position coordinates of the tool tip point in three directions in the set workpiece coordinate system (WCS), and I, J, and K to represent the attitude vectors of the tool in the WCS, the position of the tool tip point in the ideal state is obtained.

[0052] When the position of the starting tool tip point p1 = (0, 0, 0, 1) T , and the attitude of the starting tool v1 = (0, 0, 1, 0) T , the position and attitude of the tool in the ideal case are obtained after coordinate transformation.

[0053] In the actual state, use X', Y', and Z' to represent the actual position coordinates of the tool tip point in three directions in the WCS, and I', J', and K' to represent the actual attitude vectors of the tool in the WCS. Due to the existence of geometric errors of the rotation axes, the transformation matrix of the actual position and attitude of the tool in the WCS is obtained by multiplying the error-free basis by the error transformation matrices E A and E C . Based on the small error assumption, after neglecting the high-order terms, E A , E C are obtained:

[0054]

[0055] When the starting tool tip point position p1 = (0, 0, 0, 1) T , and the attitude of the starting tool s1 = (0, 0, 1, 0) T , after coordinate transformation, the tool position expression p′ = (X′, Y′, Z′, 1) T and the tool attitude expression v′ = (I′, J′, K′, 0) T in the actual case are obtained.

[0056] Step 3.2 Determine the actual center coordinates

[0057] The "S"-shaped specimen can be divided into 7 regions according to its curve twist angle: constant curvature region 1, variable curvature region 2, non-twist region 3, twist region 4, non-twist region 5, variable curvature region 6, and constant curvature region 7. Three measurement points are selected respectively based on regions 1, 2, and 3 at the upper wire, and one center coordinate is obtained by the principle of "determining the center by three points". Similarly, three measurement points are selected respectively based on regions 5, 6, and 7, and another center coordinate is obtained. The steps for the lower wire to determine the center coordinates are the same as those for the upper wire, and a total of 4 center coordinates are obtained for the upper and lower wires.

[0058] Step 3.3 Identification of Geometric Errors of Rotation Axis A

[0059] The established theoretical coordinate system of axis A is W iA , and its coordinate origin is located at the theoretical intersection of axis A and axis C. W rA is the actual coordinate system of axis A in the presence of errors. The "S"-shaped specimen is installed on the rotary table, and there are three detection points on each of the two arcs. The three detection points need to be on the same plane and the probe is perpendicular to the tangential plane at the measurement point.

[0060] Step 3.4 Identification of Geometric Errors of Rotation Axis C

[0061] W iC is the theoretical coordinate system of axis C, which coincides with the theoretical coordinate system W iA of axis A. The actual coordinate system in the presence of axis C errors is W rC . Assuming that the two center points O = [xyz 1] T and O' = [x'y'z'1] T are obtained by solving after the probe measurement in the machine tool coordinate system (MCS). The center point coordinates O and O' are transformed through the transformation matrix T AC , and the coordinates in the theoretical coordinate system W iC can be obtained as S. Then the coordinate transformation relationship between them is: O = T AC 1 S.

[0062] According to the coordinate transformation relationship between the coordinates P1 of the center point in W rC under the condition of errors and the two sets of center point coordinates S1, S1' and S2, S2', the formula (1) is obtained:

[0063]

[0064] In the formula:

[0065]

[0066] Further expand and subtract the two equations to obtain the following C-axis position error solution formula (2):

[0067]

[0068] After matrix operation, two tilt errors ε αC and ε βC of axis C are obtained, as shown in formulas (3) and (4), where the position error of axis A is substituted as a known constant.

[0069]

[0070] It can be seen from Equation (5) that the magnitude of the tilting error of the C-axis rotating around the Z-axis is related to the other two tilting errors of the C-axis. The two key linear errors δ xC1 and δ yC1 of the C-axis are obtained from Equations (6) and (7) as follows:

[0071] δ xc1 = [(y1 + y'1 + Δx1)·ε γc - (z1 + z'1)·ε βc - Δz1·ε αc - C5] / 2 (8)

[0072] δ yc1 = [(y'1 - y1 - x'1 - x1)·ε γc - Δz1·ε βc + Δz1·ε αc + C7] / 2 (9)

[0073] In the formula, C5, C6, and C7 are as shown in Equation (8):

[0074]

[0075] Using the "S"-shaped specimen, the numerical values of the measurement points can be obtained through the above identification method. Then, by using these points and the principle of forming a center point with three points, the actual center point can be constructed. By substituting the numerical values of this center point into the above geometric error identification model, the geometric error values of the machine tool can be identified. Finally, the geometric error field distribution color map of the double rotary table five-axis machine tool as shown in Figure 7 can be obtained.

[0076] Step 4. Arrange temperature sensors to measure the temperature of the machine tool;

[0077] Four temperature measurement sensors are arranged at the connection of the rotating shafts and on the corresponding components of the machine tool. The specific distribution is as follows: T1, T2, T3, and T4 are respectively placed at the lower edge of the rotary table, the left end of the A-axis, and the right end of the A-axis. During the experiment, the ambient temperature is 20°C. To accurately measure the temperature at each point, the machine tool shuts down the circulating cooling pump to eliminate the influence of the cutting fluid on the temperature value.

[0078] Step 5. Repeat the measurement of the temperature change of the machine tool to determine the stable temperature change interval of the machine tool;

[0079] Measure the temperature of the machine tool once after 0.5 hours, 1 hour, 1.5 hours, and 2 hours of the machine tool operation respectively. After 4 measurements, the stable temperature change interval of the machine tool can be determined.

[0080] Step 6. Repeat Step 2 and separately record the coordinate values of the coordinate points corresponding to the upper and lower wires of the specimen measured;

[0081] Step 7. Select several measurement points from the 100 actual measurement points obtained in Step 6 to determine the actual center coordinates;

[0082] Step 8. Select corresponding measurement points from the standard to determine the theoretical center coordinate values;

[0083] Select the measurement points adopted in Step 6 from the standard correspondingly, query the specific theoretical coordinate values of each measurement point, and obtain the theoretical coordinate values of 4 centers by the method of determining the center by three points.

[0084] Step 9. Calculate the comprehensive error of the machine tool;

[0085] Subtract the actual center coordinate values obtained in Step 7 from the theoretical center coordinate values obtained in Step 8 to obtain the comprehensive error of the machine tool. This comprehensive error includes the geometric error and thermal error of the machine tool.

[0086] Step 9.1 Establish an error decoupling and separation model;

[0087] σ se =α1σ ge +α2σ te (11)

[0088] In the formula: α1 and α2 are weight coefficients, σ se is the comprehensive error value of the machine tool, σ ge is the geometric error value of the machine tool, σ te is the thermal error value of the machine tool.

[0089] Step 9.2 Substitute the geometric error of the machine tool rotation axis obtained in Step 3 and the comprehensive error of the machine tool obtained in Step 9 into Equation (9) to obtain the thermal error value.

[0090] Step 10. Perform comprehensive error decoupling to obtain the thermal error of the machine tool;

[0091] Substitute the geometric error value and the comprehensive error value of the machine tool obtained in the above steps into the machine tool comprehensive error decoupling model for error decoupling calculation to obtain the thermal error of the machine tool.

Claims

1. A decoupling method for geometric error and thermal error of the rotary axes of a double-pendulum five-axis machine tool, characterized in that: Measurement The measuring device includes a variable-angle "S"-shaped specimen (21), a ruby contact probe (22), a temperature measuring sensor (23), a rotating shaft A-axis (24), a rotating shaft C-axis (25), and a computer (26). The geometric errors of a five-axis CNC machine tool are quickly measured using the "S"-shaped specimen, and then the thermal error of the machine tool is obtained through the decoupling and separation model of the comprehensive error of the machine tool, thus completing the decoupling of the comprehensive error of the machine tool. The variable-angle "S"-shaped specimen (21) used for measurement consists of two "S"-shaped specimens with inclination angles of 0° and 30° respectively. One of the "S"-shaped specimens with a certain angle can be selected for measurement during measurement. The decoupling method and measuring device for the geometric errors and thermal errors of the rotating axes of a double rotary table five-axis machine tool include the following steps: Step 1. Turn on the machine tool and immediately measure the coordinate values of all coordinate points on the upper and lower wires of the "S"-shaped specimen. Ten minutes after the machine tool starts, immediately start measuring and recording the coordinate points of the specimen. At this time, the heat generated by the operation of the machine tool has a relatively small impact on the overall comprehensive error, and the geometric error accounts for a relatively large proportion. Step 2. Measure all coordinate points on the upper and lower wires of the "S"-shaped specimen when the rotating axes A and C rotate at different angles. The "S"-shaped specimen has two wires, the upper and the lower. According to the relevant standards of the "S"-shaped specimen, there are 50 measurement points on each of the upper and lower wires, and the specific coordinate positions of a total of 100 measurement points on the upper and lower wires are specified in the standards. When the rotating shaft A rotates 0°, 30°, 60°, 90° respectively, and the rotating shaft C rotates 0°, 30°, 60°, 90° respectively, on-machine measurement of a total of 100 measurement points on the upper and lower wires of the "S"-shaped specimen is carried out according to the standards. Step 3. Select several measurement points, determine the actual center coordinates, and obtain the geometric error of the machine tool. Select several measurement points from the 100 actual measurement points obtained in Step 2. The specific actual coordinates of 2 centers on each of the upper and lower wires are obtained by the method of determining the center from three points. Substitute the 4 center coordinates into the geometric error decoupling and separation model to calculate the geometric errors of the double rotary table five-axis machine tool when the rotating axes A and C rotate at different angles. Step 4. Arrange temperature sensors to measure the temperature of the machine tool. Four temperature measuring sensors are arranged at the rotating shaft connection and the corresponding parts of the machine tool. The specific distribution is as follows: T1, T2, T3, and T4 are placed at the lower edge of the rotary table, the left end of the A-axis, and the right end of the A-axis respectively. The ambient temperature during the test is 20°C. To accurately measure the temperature at each point, the machine tool shuts down the circulating cooling pump to eliminate the influence of the cutting fluid on the temperature value. Step 5. Repeat measuring the temperature change of the machine tool to determine the stable temperature change interval of the machine tool. Measure the temperature of the machine tool once after 0.5 hour, 1 hour, 1.5 hours, and 2 hours of the machine tool operation respectively. After 4 measurements, determine the stable temperature change interval of the machine tool. Step 6. Repeat Step 2 and separately record the coordinate values of the corresponding coordinate points on the upper and lower wires of the measured specimen. Step 7. Select several measurement points from the 100 actual measurement points obtained in Step 6 and determine the actual center coordinates. Step 8. Select the corresponding measurement points from the standards and determine the theoretical center coordinate values. Select the measurement points used in step 6 from the standard accordingly, query the specific theoretical coordinate values of each measurement point, and obtain the theoretical coordinate values of 4 centers by the method of determining the center by three points; Step 9. Calculate the comprehensive error of the machine tool; Subtract the actual center coordinate values obtained in step 7 from the theoretical center coordinate values obtained in step 8 to obtain the comprehensive error of the machine tool. This comprehensive error includes the geometric error and thermal error of the machine tool; Step 10. Decouple the comprehensive error to obtain the thermal error of the machine tool; Substitute the geometric error values and the comprehensive error values of the machine tool obtained in the above steps into the machine tool comprehensive error decoupling model for error decoupling calculation to obtain the thermal error of the machine tool.

2. The decoupling method for geometric error and thermal error of the rotary axes of a double-pendulum five-axis machine tool according to claim 1, characterized in that: The variable-angle "S"-shaped specimen (21) used for measurement is machined by a five-axis CNC machine tool with higher precision and can be used as a standard part during the test.

3. The decoupling method for geometric error and thermal error of the rotary axes of a double-pendulum five-axis machine tool according to claim 1, characterized in that: The variable-angle "S"-shaped specimen (21) used for measurement is composed of two "S"-shaped specimens with inclination angles of 0° and 30° respectively. One of the "S"-shaped specimens at a certain angle can be selected for measurement during measurement.

4. The decoupling method for geometric error and thermal error of the rotary axes of a double-pendulum five-axis machine tool according to claim 1, characterized in that The specific content of step 3 is as follows: Step 3.1 Establish a decoupling separation model for the geometric error of the machine tool; The five-axis CNC machine tool contains two rotary axes, A and C. Each of the A and C rotary axes contains 2 types of geometric error elements, namely translational error and angular error. The translational error contains 3 error elements, and the angular error also contains 3 error elements. Therefore, each of the A and C rotary axes contains 6 geometric error elements. Among them, the translational error of rotary axis A includes δ xA , δ yA , δ zA , the angular error of rotary axis A includes ε xA , ε yA , ε zA , the translational error of rotary axis C includes δ xC , δ yC , δ zC , the angular error of rotary axis C includes ε xC , ε yC , ε zC ; According to the coordinate transformation relationship between the moving axes of the machine tool, use X, Y, and Z to represent the position coordinates of the tool tip point in three directions in the set workpiece coordinate system (WCS), and I, J, and K to represent the attitude vectors of the tool in the WCS, and obtain the position of the tool tip point in the ideal state; When the position p1 of the starting tool tip point is (0, 0, 0, 1) T , and the attitude v1 of the starting tool is (0, 0, 1, 0) T , the position and attitude of the tool in the ideal case are obtained after coordinate transformation; In the actual state, X', Y', and Z' are used to represent the actual position coordinates of the tool tip point in three directions in the WCS, and I', J', and K' represent the actual attitude vectors of the tool in the WCS; due to the existence of geometric errors of the rotary axes, the transformation matrix of the actual position and attitude of the tool in the WCS is obtained by multiplying the transformation matrix without errors by the error transformation matrices E A and E C Based on the small error assumption, after neglecting the high-order terms, E A and E C are obtained as follows: When the starting tip point position p1 = (0, 0, 0, 1) T , the attitude s1 of the starting tool = (0, 0, 1, 0) T , after coordinate transformation, the tool position expression p' = (X', Y', Z', 1)T and the tool attitude expression v' = (I', J', K', 0) in the actual situation are obtained T ; Step 3.2 Determine the actual center coordinates The "S"-shaped specimen can be divided into 7 regions according to its curve twist angle: constant curvature region 1, variable curvature region 2, non-twisted region 3, twisted region 4, non-twisted region 5, variable curvature region 6, constant curvature region 7; 3 measurement points are respectively selected based on regions 1, 2, and 3 at the upper wire, and 1 center coordinate is obtained by the principle of "determining the center by three points"; similarly, 3 measurement points are respectively selected based on regions 5, 6, and 7 to obtain another center coordinate; the steps for determining the center coordinates of the lower wire are the same as those of the upper wire, and a total of 4 center coordinates are obtained for the upper and lower wires; Step 3.3 Identification of the geometric error of the rotating axis A-axis The established theoretical coordinate system of the A-axis is W iA , and its coordinate origin is located at the theoretical intersection of the axes of the A-axis and the C-axis. W rA is the actual coordinate system of the A-axis in the presence of errors; the "S"-shaped specimen is installed on the rotating table, and there are three detection points on each of the two arcs. The three detection points need to be on the same plane and the probe is perpendicular to the tangential plane at the measurement point; Step 3.4 Identification of the geometric error of the rotating axis C-axis W iC is the theoretical coordinate system of the C-axis and the theoretical coordinate system of the A-axis W iA coincide. The actual coordinate system in the presence of C-axis error is W rC . Assume that the two center points O = [x y z 1] T and O' = [x' y' z' 1] T are obtained by solving after probe measurement in the machine coordinate system (MCS); the center point coordinates O and O' are transformed by the transformation matrix T AC to obtain the coordinates in the theoretical coordinate system W iC as S. Then the coordinate transformation relationship between them is: O = T AC -1 · S; Using the "S"-shaped specimen, the numerical values of the measurement points can be obtained through the identification methods in step 3.3 and step 3.4, and then these points are used to construct the actual center point by the principle of forming a center by three points. By substituting the numerical values of this center point into the geometric error identification model, the geometric error values of the machine tool can be identified.

5. The decoupling method for geometric error and thermal error of the rotary axis of a double-pendulum five-axis machine tool according to claim 1, characterized in that, The specific content of step 9 is as follows: Step 9.1 Assume that the geometric error and thermal error are weakly correlated and establish an error decoupling separation model: σ se = α1σ ge + α2σ te (3) Where: α1 and α2 are weighting coefficients, and σ se is the comprehensive error value of the machine tool, and σ ge is the geometric error value of the machine tool, and σ te is the thermal error value of the machine tool; Step 9.2 Substitute the geometric error of the rotating axis of the machine tool obtained in step 3 and the comprehensive error of the machine tool obtained in step 9 into the error decoupling separation model to obtain the thermal error value.

6. The decoupling method for geometric errors and thermal errors of the rotary axes of a double-turret five-axis machine tool according to claim 1, wherein: The geometric error values can be used to draw the distribution cloud map of the geometric error field of the double rotary table five-axis machine tool, so as to facilitate the quantitative analysis of the spatial distribution of geometric errors and the change trend in the machining space.

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