Five-axis machine tool geometric error analysis method, system and equipment and storage medium

Abstract

The invention provides a five-axis machine tool geometric error analysis method, system and device and a storage medium, and the method comprises the steps: carrying out the structural topology of a high-precision five-axis machine tool, obtaining a topological structure, numbering all structures in the topological structure, determining the adjacent low-order body relation of all axes, and carrying out the structural topology of the high-precision five-axis machine tool; setting a corresponding coordinate system for each axis according to the relation of the adjacent low-order bodies; constructing a kinematics positive solution model according to the relation of the adjacent low-sequence bodies and the coordinate system of each axis; substituting the initial position of each shaft into the kinematics positive solution model to obtain theoretical angle transformation corresponding to each shaft, and determining a theoretical motion track of the corresponding shaft according to the theoretical angle transformation; errors between each shaft and a theoretical movement track at multiple positions during use are collected, and the geometric error of each shaft is determined. The method solves the problem that in the prior art, traditional error analysis depends on complex sensor arrangement and expensive equipment, and it is difficult to achieve efficient and accurate geometric error analysis in actual production.

Description

Technical Field

[0001] The present invention relates to the technical field of high-end CNC machine tool state monitoring, and in particular to a five-axis machine tool geometric error analysis method, system, equipment and storage medium. Background Art

[0002] Precision and ultra-precision machining technology has become the most important component of modern machinery manufacturing industry, especially in aerospace, mold manufacturing, automotive industry and electronics industry. Precision machining technology is widely used. These technologies are not only the key to improving product quality and machining accuracy, but also play a vital role in enhancing international competitiveness. Among the various error sources of high-precision five-axis machine tools, geometric errors account for the majority. Geometric errors have become the main error source of high-precision five-axis machine tools, usually accounting for about 35% of the total error.

[0003] The machining accuracy of a high-precision five-axis machine tool ultimately depends on the relative displacement between the tool and the workpiece. The geometric error (i.e., position and orientation error) between the tool and the workpiece directly affects the accuracy of their relative displacement, thereby affecting the accuracy of the final machined part. In order to achieve precision machining of high-precision five-axis machine tools, the geometric errors of the machine tools must be effectively analyzed and compensated. Geometric errors mainly include displacement errors, angle errors, straightness errors, and coaxiality errors of the machine tools, which are derived from factors such as the structure, manufacturing process, installation accuracy, and wear during long-term use of the machine tools.

[0004] In order to improve the machining accuracy of high-precision five-axis machine tools, their geometric errors must be effectively measured and compensated. Based on traditional error analysis methods, the compensation of geometric errors of five-axis machine tools usually needs to be achieved through multi-point measurement and mathematical modeling. However, existing geometric error analysis methods often rely on complex sensor arrangements and expensive equipment, making it difficult to achieve efficient and accurate geometric error analysis in actual production. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a five-axis machine tool geometric error analysis method, system, device and storage medium, which solves the problem that traditional error analysis in the prior art relies on complex sensor arrangements and expensive equipment, making it difficult to achieve efficient and accurate geometric error analysis in actual production.

[0006] According to an embodiment of the present invention, a five-axis machine tool geometric error analysis method includes:

[0007] Perform structural topology on the high-precision five-axis machine tool to obtain the topological structure, number all structures in the topological structure, determine the adjacent low-order body relationship of all axes, and set the corresponding coordinate system for each axis according to the adjacent low-order body relationship;

[0008] According to the relationship between adjacent low-order bodies and the coordinate system of each axis, a kinematics positive solution model is constructed;

[0009] Substitute the initial position of each axis into the kinematics forward solution model to obtain the theoretical angle transformation corresponding to each axis, and determine the theoretical motion trajectory of the corresponding axis based on the theoretical angle transformation;

[0010] The error between each axis and the theoretical motion trajectory at multiple positions during use is collected to determine the geometric error of each axis.

[0011] Preferably, the topological structure includes a bed R, a turning spindle C, a workpiece W, a tool T, a milling spindle S, a B axis, a Y axis, an X axis, a Z axis and a tailstock;

[0012] The geometric error includes a position-independent geometric error and a position-dependent geometric error, wherein the position-independent geometric error is a constant and the position-dependent geometric error is a variable;

[0013] After obtaining the machine tool topology, it is necessary to determine the position-independent geometric error terms and position-dependent geometric error terms of all axes in the topology.

[0014] Preferably, the coordinate origin of the coordinate system corresponding to the turning spindle C is at the center of the end section of the cutting spindle C, and the coordinate system corresponding to the bed R coincides with the coordinate system corresponding to the turning spindle C;

[0015] The coordinate origin of the coordinate system corresponding to the workpiece W, the milling spindle S and the tool T is at their respective centroids;

[0016] The coordinate systems corresponding to the Y-axis, X-axis, Z-axis and B-axis and the coordinate system corresponding to the milling spindle S coincide with each other.

[0017] Preferably, the kinematics forward solution model is as follows:

[0018]

[0019] Among them, (x, y, z) are the initial coordinates of each axis in each coordinate system, (θ b ,θ c ) are the lateral deflection angle and longitudinal deflection angle of each axis, L rzx L is the offset of the coordinate origin between the coordinate system of the bed R and the Z axis in the x direction. cwx L is the offset of the coordinate origin between the turning spindle C and the Z axis in the x direction. tool It is the coordinate origin offset of the coordinate system of tool T and milling spindle S in the z direction.

[0020] Preferably, the theoretical angle transformation is as follows:

[0021]

[0022] Among them, O x ,O y ,O z They are the three-angle rotation angles of each axis respectively.

[0023] Preferably, the errors among the X-axis, the Y-axis and the Z-axis in the vertical direction and the errors among the B-axis and the C-axis in the theoretical vertical direction are all position-independent errors.

[0024] Preferably, the calculation formula of the position-dependent set error is as follows:

[0025]

[0026] Among them, m is the position-related geometric error sequence number, n is the sampling point sequence number, a is the sampling point weight coefficient, and p is the error between each axis and the theoretical motion trajectory at multiple positions when in use.

[0027] On the other hand, according to an embodiment of the present invention, a five-axis machine tool geometric error analysis system is also provided. The system uses the above-mentioned five-axis machine tool geometric error analysis method, including:

[0028] A sampling module, wherein the sampling module is used to measure the error between each axis and the theoretical motion trajectory at multiple positions when each axis is in use;

[0029] A processing module, the processing module is used to generate a topological structure of a high-precision five-axis machine tool and construct a kinematics forward solution model according to the topological structure;

[0030] A calculation module is used to calculate the geometric error of each axis.

[0031] On the other hand, according to an embodiment of the present invention, there is also provided a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the above-mentioned five-axis machine tool geometric error analysis method.

[0032] On the other hand, according to an embodiment of the present invention, there is further provided a computer storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the above-mentioned five-axis machine tool geometric error analysis method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention performs structural topology on a high-precision five-axis machine tool, constructs a kinematic forward solution model based on the topological structure after topology, calculates the theoretical operating trajectory of each axis, and then uses some simple instruments, such as laser interferometers, to collect the errors between the actual operation of each axis and the theoretical operation trajectory, so as to calculate the geometric errors of each axis. It is no longer necessary to rely on complex sensor arrangements and expensive equipment, and can effectively realize efficient and accurate geometric error analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 4 is a flow chart of geometric error analysis according to an embodiment of the present invention.

[0036] Figure 2 This is a topological structure diagram of a high-precision five-axis machine tool according to an embodiment of the present invention.

[0037] Figure 3 FIG. 4 is a position-independent error analysis diagram of an embodiment of the present invention.

[0038] Figure 4 4 is a coordinate system relationship diagram of each structure in the topological structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0040] like Figure 1 As shown, the embodiment of the present invention proposes a five-axis machine tool geometric error analysis method, including:

[0041] Perform structural topology on the high-precision five-axis machine tool to obtain the topological structure, number all structures in the topological structure, determine the adjacent low-order body relationship of all axes, and set the corresponding coordinate system for each axis according to the adjacent low-order body relationship;

[0042] The errors of high-precision five-axis machine tools can be divided into position-related geometric errors and position-independent geometric errors according to the nature of the errors. Position-related errors are due to the presence of gaps in the transmission shafts such as the lead screw of the high-precision five-axis machine tool, which causes the moving axis to deviate during the movement process and cannot reach the actual position. Position-independent errors are irrelevant to the position of the moving axis of the high-precision five-axis machine tool in space. They are generally caused by manufacturing problems or during the installation process and are constant values.

[0043] First, the structural topology of the high-precision five-axis machine tool is carried out, such as Figure 2 As shown in the figure, the topological structure after topology includes bed R, turning spindle C, workpiece W, tool T, milling spindle S, B axis, Y axis, X axis, Z axis and tailstock, among which Y axis, X axis, Z axis and B axis are linear axes, turning spindle C and milling spindle S are rotation axes.

[0044] Taking the X linear axis as an example, when it moves in the X direction, six geometric errors will be generated that vary with the displacement x, including the positioning error δ x (x), straightness error δ y (x) and δ z (x), rolling error ε x (x), pitch error ε y (x) and the runout error ε z (x) (the subscript indicates the direction of rotation or the axis direction around which the axis rotates). For the rotation axis, taking the C axis as an example, due to the six degrees of freedom of the spatial object, six geometric errors that vary with the displacement will be generated during rotation, namely radial runout error δ x (c) and δ y (c) End face runout error δ z (c) Angular positioning error ε z (c) Tilt deviation error ε x (c) and ε y (c).

[0045] First, the position-independent error of the high-precision five-axis machine tool is analyzed, which mainly includes the verticality error of the linear axis and the rotation axis. According to the transmission sequence, the Z axis is connected to the bed R, and it can be considered that there is no position-independent geometric error. The motion axis X is above the Z axis and can be regarded as being located in the xoz plane. It can be considered that it has a verticality error S rotating around the y axis in this plane. xz There are two vertical errors in the Y axis, namely S yx With S yz ,like Figure 3 shown.

[0046] For the rotating axis, due to installation error, the rotation axis direction of the B axis cannot be completely parallel to the y axis, and there are two perpendicularity errors α around the x axis and around the z axis. YBy and γ YBy , α, β, γ correspond to rotations around the x, y, and z axes. The first and second subscripts represent adjacent bodies, and the third subscript represents the corresponding reference world coordinate axis. Similarly, the C axis and the z axis cannot be completely parallel. There are two perpendicularity errors α around the x axis and the y axis respectively. RCz and β RCz Therefore, the high-precision five-axis machine tool has a total of 7 position-independent errors (ignoring 4 installation position errors), totaling 37 error elements, as shown in Table 1.

[0047] Table 1 Geometric error terms

[0048]

[0049] According to the connection relationship between typical bodies, the axes of the high-precision five-axis machine tool are numbered to determine the relationship between adjacent low-order bodies. From the above topological structure diagram of the high-precision five-axis machine tool, it can be seen that body B1 represents the R bed; body B2 represents the C turning spindle; body B3 represents the W workpiece; body B4 represents the tailstock; body B5 represents the Z axis; body B6 represents the X axis; body B7 represents the Y axis; body B8 represents the B axis; body B9 represents the S milling spindle; body B10 represents the T tool. The topological structure of the high-precision five-axis machine tool can be divided into three branches:

[0050] Branch 1: bed, turning spindle, workpiece;

[0051] Branch 2: bed, Z-axis, X-axis, Y-axis, B-axis, S-axis, and tool;

[0052] Branch three: bed and tailstock.

[0053] That is, the end bodies in branch 1 and branch 2 are workpiece and tool respectively. According to the above analysis and Figure 4 An array of lower numbered objects is obtained as shown.

[0054] Table 2 Low-order body array table

[0055]

[0056] According to the relationship between adjacent low-order bodies and the coordinate system of each axis, a kinematics positive solution model is constructed;

[0057] By establishing a five-axis high-precision five-axis machine tool low-order body array, the correlation between each component can be clarified, thereby determining the relative position and posture changes between each component. In order to facilitate the understanding of the relationship between the local coordinate systems fixed on each feature body, it is further simplified as follows Figure 4 The coordinate system relationship diagram is shown.

[0058] The origin of the coordinate system corresponding to the turning spindle C is at the center of the end section of the cutting spindle C, and the coordinate system corresponding to the bed R coincides with the coordinate system corresponding to the turning spindle C;

[0059] The origin of the coordinate system corresponding to the workpiece W, the milling spindle S and the tool T is at their respective centroids;

[0060] The coordinate systems corresponding to the Y-axis, X-axis, Z-axis and B-axis and the coordinate system corresponding to the milling spindle S coincide with each other.

[0061] Since the length of the workpiece and the tool can be changed, the origin of the W coordinate system and the origin of the T coordinate system do not coincide with the origin of the Z, X, Y, B, and S coordinate systems in the initial state.

[0062] Substitute the initial position of each axis into the kinematics forward solution model to obtain the theoretical angle transformation corresponding to each axis, and determine the theoretical motion trajectory of the corresponding axis based on the theoretical angle transformation;

[0063] According to the low-order body array table in Table 2 above, the homogeneous transformation matrix of tool T relative to bed R in milling mode of high-precision five-axis turning and milling composite machine tool can be obtained: And the homogeneous transformation matrix of the workpiece W relative to the bed R (The meanings of other homogeneous matrix algebraic expressions are analogous):

[0064]

[0065] Furthermore, the position transformation matrix of the high-precision five-axis machine tool tool relative to the workpiece coordinate system can be obtained:

[0066]

[0067] Transforming the above formula, we can get:

[0068]

[0069] According to the transformation between adjacent bodies, we can get:

[0070]

[0071] In the tool T coordinate system, the position of the tool tip is represented by Pt. In the initial state, it can be expressed by homogeneous coordinates as (P tx P ty P tz 1) T , during processing, assuming that there is no error, then according to the principle that the tool tip and the cut point coincide, the coordinates of the tool's initial position Pt in the workpiece coordinate system after the spatial motion transformation of each motion axis can be written as follows, where the initial position of the tool tip in the tool coordinate system is: P tx =P ty =P tz = 0, and the kinematics correct solution model can be obtained by substituting:

[0072]

[0073] The command position sequence of the five axes (x, y, z, θ b ,θ c ) is input into the above formula to obtain the theoretical position of the tool tip in the workpiece coordinate system, where (x, y, z) is the initial coordinate of each axis in each coordinate system, (θ b ,θ c ) are the lateral deflection angle and longitudinal deflection angle of each axis respectively. In addition, Figure 4 It can be seen that Lrzx L is the offset of the coordinate origin between the coordinate system of the bed R and the Z axis in the x direction. rzy L is the coordinate origin offset between the bed R and the Z axis coordinate system in the y direction. rzz L is the coordinate origin offset between the coordinate system of the bed R and the Z axis in the z direction, cwx L is the offset of the coordinate origin between the turning spindle C and the Z axis in the x direction. cwy L is the coordinate origin offset between the turning spindle C and Z axis coordinate systems in the y direction. cwz L is the coordinate origin offset between the turning spindle C and the Z axis coordinate system in the z direction. tool It is the coordinate origin offset of the coordinate system of tool T and milling spindle S in the z direction.

[0074] The theoretical position can be used to derive the theoretical angle transformation of each axis:

[0075]

[0076] O x ,O y ,O z They are the three-angle rotation angles of each axis respectively.

[0077] Then, the theoretical motion trajectory of each axis is derived according to the theoretical angle transformation of each axis and the theoretical position of the tool tip.

[0078] The errors between each axis and the theoretical motion trajectory at multiple positions during use are collected to determine the geometric error of each axis.

[0079] (1) Position-independent error

[0080] From the results of geometric error terms in Table 1, it can be seen that there are a total of 7 position-independent errors, which do not change with position and time during the operation of the high-precision five-axis machine tool, so they can be characterized as constants, as shown in the following formula. Among them, c1, c2, and c3 represent the verticality errors between the three moving axes, in units of μm / μm, which are constants; c4-c7 represent the four verticality errors between the B axis, C axis and the corresponding theoretical direction, in units of μm / μm, which are constants.

[0081] f m =c m (m=1,2,...,7)

[0082] (2) Position-related error

[0083] In actual use, a laser interferometer is used to measure the position-related geometric errors throughout the entire stroke, and the error values ​​corresponding to a certain number of equidistant position points between the actual running trajectory of each axis and the theoretical running trajectory are collected throughout the entire stroke.

[0084] For a given (n+1) data point, there is a unique polynomial with the highest order of n that passes through all the data points. Therefore, the collected error values ​​can be used to fit the polynomial to establish the expression of the position-related geometric errors changing with the position, as shown in the following formula. Among them, the subscript m represents the serial number of the 30 position-related errors of the three moving axes and the two rotating axes; n represents the sampling point sequence number, where n < the number of collected data points; a represents the coefficients of the high-order polynomial; p is the error of each axis at multiple positions with the theoretical motion trajectory when in use. Similarly, the position and angle dimensions need to be unified based on the small angle assumption.

[0085] f m =a m,n p m n +a m,n-1 p m n-1 +…+a m,1 p m 1 +a m,0 (m=8,9,...,37)

[0086] By using some simple instruments, such as laser interferometers, to collect the errors between the actual operation of each axis and the theoretical operation trajectory, the geometric errors of each axis can be calculated. This no longer relies on complex sensor arrangements and expensive equipment, and can effectively achieve efficient and accurate geometric error analysis.

[0087] On the other hand, an embodiment of the present invention further provides a five-axis machine tool geometric error analysis system, which uses the above-mentioned five-axis machine tool geometric error analysis method, including:

[0088] Sampling module: The sampling module is used to measure the error between each axis and the theoretical motion trajectory at multiple positions when in use;

[0089] A processing module, which is used to generate a topological structure of a high-precision five-axis machine tool and to construct a kinematics forward solution model according to the topological structure;

[0090] Calculation module,The calculation module is used to calculate the geometric error of each axis.

[0091] On the other hand, an embodiment of the present invention further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the above-mentioned five-axis machine tool geometric error analysis method.

[0092] On the other hand, an embodiment of the present invention further provides a computer storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the above-mentioned five-axis machine tool geometric error analysis method.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A five-axis machine tool geometric error analysis method, characterized in that: include: Perform structural topology on the high-precision five-axis machine tool to obtain the topological structure, number all structures in the topological structure, determine the adjacent low-order body relationship of all axes, and set the corresponding coordinate system for each axis according to the adjacent low-order body relationship; According to the relationship between adjacent low-order bodies and the coordinate system of each axis, a kinematics positive solution model is constructed; Substitute the initial position of each axis into the kinematics forward solution model to obtain the theoretical angle transformation corresponding to each axis, and determine the theoretical motion trajectory of the corresponding axis based on the theoretical angle transformation; The error between each axis and the theoretical motion trajectory at multiple positions during use is collected to determine the geometric error of each axis.

2. A five-axis machine tool geometric error analysis method as claimed in claim 1, characterized in that: The topological structure includes a bed R, a turning spindle C, a workpiece W, a tool T, a milling spindle S, a B axis, a Y axis, an X axis, a Z axis and a tailstock; The geometric error includes a position-independent geometric error and a position-dependent geometric error, wherein the position-independent geometric error is a constant and the position-dependent geometric error is a variable; After obtaining the machine tool topology, it is necessary to determine the position-independent geometric error terms and position-dependent geometric error terms of all axes in the topology.

3. A five-axis machine tool geometric error analysis method as claimed in claim 2, characterized in that: The origin of the coordinate system corresponding to the turning spindle C is at the center of the end section of the cutting spindle C, and the coordinate system corresponding to the bed R coincides with the coordinate system corresponding to the turning spindle C; The coordinate origin of the coordinate system corresponding to the workpiece W, the milling spindle S and the tool T is at their respective centroids; The coordinate systems corresponding to the Y-axis, X-axis, Z-axis and B-axis and the coordinate system corresponding to the milling spindle S coincide with each other.

4. A five-axis machine tool geometric error analysis method as claimed in claim 2, characterized in that: The kinematics positive solution model is as follows: Among them, (x, y, z) are the initial coordinates of each axis in each coordinate system, (θ b ,θ c ) are the lateral deflection angle and longitudinal deflection angle of each axis, L rzx L is the offset of the coordinate origin between the coordinate system of the bed R and the Z axis in the x direction. cwx L is the offset of the coordinate origin between the turning spindle C and the Z axis in the x direction. tool It is the coordinate origin offset of the coordinate system of tool T and milling spindle S in the z direction.

5. A five-axis machine tool geometric error analysis method as claimed in claim 4, characterized in that: The theoretical angle transformation is as follows: Among them, O x ,O y ,O z They are the three-angle rotation angles of each axis respectively.

6. A five-axis machine tool geometric error analysis method as claimed in claim 2, characterized in that: The errors between the X-axis, the Y-axis and the Z-axis in the vertical direction and the errors between the B-axis and the C-axis in the theoretical vertical direction are all position-independent errors.

7. A five-axis machine tool geometric error analysis method as claimed in claim 1, characterized in that: The calculation formula of the position-related set error is as follows: Among them, m is the position-related geometric error sequence number, n is the sampling point sequence number, a is the sampling point weight coefficient, and p is the error between each axis and the theoretical motion trajectory at multiple positions when in use.

8. A five-axis machine tool geometric error analysis system, characterized in that: The system uses a five-axis machine tool geometric error analysis method according to any one of claims 1 to 7, comprising: A sampling module, wherein the sampling module is used to measure the error between each axis and the theoretical motion trajectory at multiple positions when each axis is in use; A processing module, the processing module is used to generate a topological structure of a high-precision five-axis machine tool and construct a kinematics forward solution model according to the topological structure; A calculation module is used to calculate the geometric error of each axis.

9. A computer device, characterized in that: The invention comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes a five-axis machine tool geometric error analysis method as claimed in any one of claims 1 to 7.

10. A computer storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor executes a five-axis machine tool geometric error analysis method as claimed in any one of claims 1 to 7.

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