A method and system for identifying geometric errors of a five-axis CNC machine tool swing head

Abstract

The present invention discloses a method and system for identifying the geometric error of a five-axis CNC machine tool swing head, establishes a measurement coordinate system, tracks the moving reflector on the five-axis CNC machine tool in real time, obtains the distance between the machine tool measuring point and the base station and the distance between each measuring point; calibrates the three-dimensional coordinate values ​​of the laser tracking interferometer base station position and the machine tool measuring point in the measurement coordinate system according to the distance, determines the measurement coordinate system, and performs homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems; converts the three-dimensional coordinates of the measuring point in the measurement coordinate system into the three-dimensional coordinates in the machine tool coordinate system; solves the measurement point spatial error caused by the geometric error of the machine tool rotating axis in the machine tool coordinate system, determines the identification model of the geometric error related to the rotating axis position, and uses the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head. The present invention reduces the influence of random error on the measurement accuracy, and improves the measurement efficiency and measurement accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field, and in particular relates to a method and system for identifying geometric errors of a swing head of a five-axis CNC machine tool. Background Art

[0002] Precision and ultra-precision machining and manufacturing technologies have an increasing demand for high-end multi-axis CNC machine tools with ultra-high precision rotating axes, especially in the field of manufacturing large-aperture optical free-form surface components for inertial confinement nuclear fusion, earth observation, lidar, EUV lithography, etc. The geometric accuracy of the rotating axis directly affects the key optical performance indicators of the processed large optical lens, such as the axis position, surface shape accuracy, and surface roughness. In addition, the off-axis processing of large-aperture optical components places more stringent requirements on the geometric accuracy and performance of the rotating axis of the CNC machine tool.

[0003] At present, the commonly used rotary axis geometric error measurement methods mainly include laser interferometer and ballbar measurement methods. Laser interferometer is mostly used to measure the positioning error of the turntable, and it is difficult to adjust the optical path during the measurement process, which is highly dependent on the operator's level and has low measurement efficiency; the ballbar method requires multiple installations to achieve the separation of geometric errors, and the test process requires the adjustment of eccentricity, which is time-consuming and has a small test range and low measurement accuracy. The traditional measurement method is limited by the installation position and cannot measure and identify the geometric errors of the rotary axis of any type of machine tool (such as a five-axis CNC machine tool with AB swing axis). Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a five-axis CNC machine tool swing head geometric error identification method and system in view of the deficiencies in the above-mentioned prior art, which is used to solve the technical problems of low measurement efficiency and low measurement accuracy of the rotating axis of the five-axis machine tool and the installation of the measuring instrument being limited by the machine tool workspace.

[0005] The present invention adopts the following technical solutions:

[0006] A method for identifying geometric errors of a five-axis CNC machine tool swing head comprises the following steps:

[0007] S1. Use the laser tracking interferometer base station position to establish the measurement coordinate system ( L X, L Y, L Z), using a laser tracking interferometer to track the moving reflector on a five-axis CNC machine tool in real time, and obtaining the distance between the machine tool measuring point and the base station and the distance between each measuring point;

[0008] S2. Calibrate the three-dimensional coordinates of the laser tracking interferometer base station position and the machine tool measurement point in the measurement coordinate system according to the distance obtained in step S1, determine the measurement coordinate system, and perform homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems.

[0009] S3, using the homogeneous transformation matrix obtained in step S2 Set the measurement coordinate system ( L X, L Y, L Z) convert the three-dimensional coordinates of the measuring point into the three-dimensional coordinates of the machine tool coordinate system;

[0010] S4, solving the measuring point spatial error caused by the geometric error of the machine tool rotation axis in the machine tool coordinate system obtained in step S3, determining the identification model of the geometric error related to the rotation axis position, and using the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head.

[0011] Specifically, step S1 is as follows:

[0012] S101. Place the laser tracking interferometer on the five-axis CNC machine tool workbench and install the reflector in the tool coordinate system T-CS. j The position of j represents the jth initial installation position of the reflector j = 1, ..., J, and the three linear axes of the five-axis CNC machine tool are moved so that the laser tracking interferometer is located at LT of the machine tool workspace. i Position, i represents the position of the i-th base station i=1,…,I, the laser tracking interferometer adjusts its own yaw and pitch angles and tracks the moving reflector in real time;

[0013] S102, B axis rotation angle b k , k represents the kth measuring point k = 1, ..., K, the laser tracking interferometer measures and records the relative distance change L ijk ;

[0014] S103, laser tracking interferometer moves to the next position LT i+1 , repeat the process of step S102 until all preset laser tracking interferometer base station positions are measured;

[0015] S104, install the reflector to the next initial position t j+1 , the laser tracking interferometer re-aims and locks the reflector, and repeats steps S102 and S103 until all the machine tool space measurement points arranged in the experiment are measured.

[0016] Specifically, in step S2, according to the least squares principle and using the measurement residual u ijk and the residual error r of the rigid body motion constraint condition q , solve the least squares problem by minimizing the residual sum of squares; calculate the optimal solution using the Levenberg-Marquardt nonlinear least squares method Determine the spatial position coordinates of the laser tracking interferometer base station, the actual spatial three-dimensional coordinates of the measuring point and the dead zone length.

[0017] Furthermore, the least squares function is solved as follows:

[0018]

[0019] Among them, K is the number of measurement points during the rotation of the rotating axis, V is the unknown vector, F is the least squares function, and Q is the number of residual equations.

[0020] Specifically, in step S3, the homogeneous transformation matrix Specifically:

[0021]

[0022] Among them, I 3×3 is the third-order identity matrix, M [LT i ] is the theoretical coordinate value of the base station position in the machine tool coordinate system, L [LT i,a ] is the actual position of the base station in the measurement coordinate system.

[0023] Specifically, step S4 is as follows:

[0024] Determine the transformation matrix from the rotation axis coordinate system to the five-axis CNC machine tool coordinate system, and establish the relationship between the measuring point coordinates and the reflector installation position; solve the actual initial installation position of the reflector in the B-axis coordinate system under the condition that the geometric error of the initial position of the rotation axis is set to 0 B [t j,a ]; solve the measuring point geometric error caused by the rotation axis geometric error in the five-axis CNC machine tool coordinate system, and determine the identification model of the rotation axis position related geometric error.

[0025] Furthermore, the relationship between the measuring point coordinates and the reflector installation position is specifically:

[0026]

[0027] in, M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual initial installation position of the reflector in the B-axis coordinate system.

[0028] Furthermore, the geometric error of the measuring point caused by the geometric error of the rotating axis in the coordinate system of the five-axis CNC machine tool is solved as follows:

[0029]

[0030] in,M [ΔP jk,GE ] is the spatial position deviation of the measuring point caused by the B-axis geometric error in the machine tool coordinate system; M [P jk,a ] is the actual three-dimensional coordinate of the measuring point in the machine tool coordinate system; M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual installation position coordinate of the reflector in the B-axis coordinate system.

[0031] Furthermore, the identification model of the rotation axis position related geometric error is specifically:

[0032]

[0033] in, M [ΔP jk,PDGE ] is the position-related geometric error matrix generated by the machine tool during the measurement process in the machine tool coordinate system, B jk,PDGE is the coefficient matrix related to the initial installation position of the reflector and the B-axis rotation angle, E AB (b k ) is the angular error of the B axis around the X axis when the rotation axis rotates to the kth position, E BB (b k ) is the positioning error of the B axis when the rotating axis rotates to the kth position, E CB (b k ) is the angular error of the B axis around the Z axis when the rotating axis rotates to the kth position, E XB (b k ) is the straightness error of the B axis in the X-axis direction when the rotating axis rotates to the kth position, E YB (b k ) is the straightness error of the B axis in the Y axis direction when the rotating axis rotates to the kth position, E ZB (b k ) is the straightness error of the B-axis in the Z-axis direction when the rotating axis rotates to the kth position.

[0034] In a second aspect, an embodiment of the present invention provides a five-axis CNC machine tool swing head geometric error identification system, characterized in that it includes:

[0035] The measurement module uses the laser tracking interferometer base station position to establish the measurement coordinate system ( L X, L Y, LZ), using a laser tracking interferometer to track the moving reflector on a five-axis CNC machine tool in real time, and obtaining the distance between the machine tool measuring point and the base station and the distance between each measuring point;

[0036] The calibration module calibrates the laser tracking interferometer base station position and the three-dimensional coordinate value of the machine tool measurement point in the measurement coordinate system according to the distance obtained by the measurement module, determines the measurement coordinate system, and performs homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems.

[0037] Conversion module, using the homogeneous transformation matrix obtained by the calibration module Set the measurement coordinate system ( L X, L Y, L Z) convert the three-dimensional coordinates of the measuring point into the three-dimensional coordinates of the machine tool coordinate system;

[0038] The identification module solves the spatial error of the measuring point caused by the geometric error of the machine tool rotation axis in the machine tool coordinate system obtained by the conversion module, determines the identification model of the geometric error related to the rotation axis position, and uses the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] The invention discloses a method for identifying geometric errors of a five-axis CNC machine tool swing head. The base station is installed only once, and its position change is achieved by moving a workbench, thereby reducing the time spent on multiple installations of the base station and greatly improving measurement efficiency. The rigid body rotation motion constraint theory is introduced to greatly reduce random measurement errors.

[0041] Furthermore, the laser tracker is used to measure the geometric error of the yaw axis, using length data instead of angle data, thereby improving measurement accuracy; the laser tracker uses four base stations to measure and establish a measurement coordinate system independent of the machine tool coordinate system. The spatial coordinate information of the measuring points does not need to be converted during collection, thereby improving measurement efficiency.

[0042] Furthermore, the rigid body rotation constraint theory is introduced, and the least squares principle is used to solve the base station position and the measuring point spatial coordinates, so as to determine the transformation matrix between the measurement coordinate system and the machine tool coordinate system; the MATLAB program can be used to realize the rapid transformation of the measuring point coordinates, laying the foundation for the next step of error identification.

[0043] Furthermore, according to the rigid body rotation constraint theory, when two reflectors at different positions fixed on the rotation axis rotate at any angle, the distance between them remains unchanged; the least squares principle is used to solve the minimum distance between the measuring points, thereby determining the base station position and the spatial coordinates of the measuring points, reducing the measurement uncertainty caused by random errors.

[0044] Furthermore, the transformation matrix between the two coordinate systems can be directly obtained according to the principle of homogeneous coordinate transformation, but such a solution will be greatly affected by random errors. A more accurate coordinate transformation matrix can be determined by using the least squares method to determine the coordinate transformation matrix.

[0045] Furthermore, the actual spatial error of the measuring point is used to separate and solve the geometric error that is independent of the position of the rotating axis. The actual spatial error of the measuring point is subtracted from the spatial error caused by the theoretical error that is independent of the position of the rotating axis, thereby obtaining the spatial position error caused by the error related to the position of the rotating axis, and further solving the error related to the position of the rotating axis; the separation and identification of the geometric error of the rotating axis is achieved.

[0046] Furthermore, by using the three different installation positions of the reflector and the coordinates of the measuring points corresponding to the positions of the reflector, multiple sets of equations can be constructed according to the constraint theory of rigid body rotation, thereby forming hyperstatic equations, which is conducive to the accurate solution of the base station coordinates.

[0047] Furthermore, solving the measuring point error caused by the geometric error of the rotating axis in the machine tool coordinate system is conducive to evaluating the change of the machine tool spatial accuracy under the influence of the geometric error, and the geometric error of the machine tool can be separated through the error identification model established by the theoretical coordinate change.

[0048] Furthermore, the separation algorithm of the position-related geometric errors of the rotating axis is encapsulated into an identification model using MATLAB, which can improve the efficiency of data processing and thus save measurement costs; the separation and identification of the position-related errors of the machine tool can be achieved by simply importing the spatial error vector caused by the position-related errors in the measurement data into the identification model.

[0049] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0050] In summary, the present invention utilizes the additional rigid body motion constraint theory to calibrate the laser tracker base station position, dead zone length, and measurement point coordinates, thereby reducing the impact of random errors on measurement accuracy and improving measurement efficiency and measurement accuracy.

[0051] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic diagram of laser tracking interferometer measurement;

[0053] Figure 2 A schematic diagram of a measurement coordinate system composed of a laser tracking interferometer of the present invention;

[0054] Figure 3It is a schematic diagram of the laser tracking interferometer base station and measurement point position solution of the present invention. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0057] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0058] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects are in an "or" relationship.

[0059] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0060] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0061] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0062] The present invention provides a method for identifying the geometric error of the swing head of a five-axis CNC machine tool. It uses a four-base station laser tracking interferometer for time-sharing measurement to reduce the measurement cost while ensuring the measurement accuracy; it introduces a rotational rigid body motion constraint in the measurement algorithm, thereby effectively reducing the measurement uncertainty. At the same time, the measurement is performed based on the self-calibration coordinate system of the four-base station laser tracking interferometer, which gets rid of the limitation of the CNC machine tool's own coordinate system and has a wider range of applications. In addition, the present invention has the advantages of short detection time, high detection accuracy, and low detection uncertainty. The detection accuracy meets the detection requirements of precision CNC machine tools and can be used for the detection of rotation axis errors of precision CNC machine tools.

[0063] The present invention provides a five-axis CNC machine tool swing head geometric error identification method, including a measurement scheme and measurement data processing, and the specific steps are as follows:

[0064] S1. Measurement

[0065] See also Figure 2 During measurement, the measurement coordinate system is established by tracking the position of the laser interferometer base station. Before measuring the geometric error of the rotary axis of a five-axis machine tool, it is necessary to first measure the geometric error of the linear axis to ensure that the linear axis accuracy is within the required range; thereby ensuring the measurement accuracy of the rotary axis geometric error term.

[0066] See also Figure 1 , the measurement process is as follows:

[0067] S101. Place a single laser tracking interferometer on the workbench of a five-axis CNC machine tool, and install the reflector near the spindle end face, i.e., the tool coordinate system T-CS. j The position of the reflector (j represents the jth initial installation position of the reflector j = 1, ..., J), the three linear axes of the machine tool are moved so that the laser tracking interferometer is located at the LT of the machine tool workspace. i Position (i represents the position of the i-th base station i=1,...,I), the laser tracking interferometer adjusts its own yaw and pitch angles and tracks the moving reflector in real time;

[0068] S102, B axis rotation angle b k(k represents the kth measuring point k=1,……,K), the laser tracking interferometer measures and records the relative distance change L ijk (indicates that the base station is at the i-th position, the reflector is at the j-th initial installation position, and the B-axis rotation angle b k , the relative distance between the measuring point and the base station);

[0069] Every time the B-axis rotates an angle, the machine tool stops for a certain period of time, and the laser tracking interferometer measures and records the relative distance change.

[0070] S103, laser tracking interferometer moves to the next position LT i+1 , repeat the process of step S102 until all preset base station positions are measured;

[0071] S104, install the reflector to the next initial position t j+1 , the laser tracking interferometer re-aims and locks the reflector, and repeats steps S102 and S103 until all measuring points are measured.

[0072] The measurement coordinate system is established using the mutual position relationship between the four measurement base stations ( L X, L Y, L Z); Set the reference point of base station LT1 as the origin of the coordinate system, and the line connecting the reference point of base station LT1 and the reference point of base station LT2 as the coordinate system of the measurement. L X-axis, measuring coordinate system L The Y axis is perpendicular to L X axis, and the reference point of base station LT3 is located at L X L On the Y plane, according to the right-hand screw rule, the measurement coordinate system can be determined L The Z axis. The constructed measurement coordinate system constrains six system parameters. In this measurement coordinate system, the base station position coordinates and the actual three-dimensional coordinates of the measurement point have definite solutions.

[0073] According to the above conditions, set the location coordinates of the four base stations L [LT i ]for:

[0074]

[0075] In this measurement coordinate system, the base station position coordinates and the actual three-dimensional coordinate values ​​of the measurement point are expressed as L [LT i,a ]and represents the initial installation position of the jth reflector, and the rotation angle of the rotation axis is b k The coordinate value of the measuring point at that time.

[0076] S2. Calibration of tracking interferometer base station position and measuring point three-dimensional coordinates

[0077] According to the ranging principle of laser tracking interferometer and the definition of dead zone length, the nonlinear equations of the base station position and the actual three-dimensional coordinate values ​​of the measuring point are listed, as shown in formula (2). For two different points in the same coordinate system, when they move the same angle around the same rotation axis, the distance between the two points remains unchanged; the rigid body motion constraint condition is introduced when the reflector rotates around the rotation axis, as shown in formula (4).

[0078] || L [LT i,a ]- L [P jk,a ]||=L ijk +l j (2)

[0079]

[0080]

[0081] Among them, L ijk is the base station at the i-th position, the reflector at the j-th initial installation position, and the rotation axis angle b k The relative distance between the measuring point and the base station.

[0082] According to the least squares principle and using the measurement residual u ijk and the residual error r of the rigid body motion constraint condition q , solve the least squares problem by minimizing the residual sum of squares, as shown in formula (5); use the Levenberg-Marquardt nonlinear least squares method to find the optimal solution Thus, the spatial position coordinates of the base station, the actual spatial three-dimensional coordinates of the measuring point and the dead zone length are determined.

[0083]

[0084]

[0085]

[0086]

[0087] Among them, K is the number of measurement points during the rotation of the rotating axis, and V is the unknown vector ( L [LT a ], T [P a ],l) T, respectively represent the unknown vectors of the base station position coordinates, the actual three-dimensional coordinates of the measuring point and the dead zone length in the measurement coordinate system, F is the least squares function, and Q is the number of residual equations.

[0088] S3. Conversion between measurement coordinate system and machine tool coordinate system

[0089] The corresponding homogeneous transformation matrix is ​​used to realize the conversion between the measurement coordinate system and the machine tool coordinate system. The conversion relationship between the laser tracking interferometer base station position and the measuring point space coordinates in the two coordinate systems is shown in formulas (6) and (7).

[0090]

[0091] in, M [P jk ,a] is the actual three-dimensional coordinate value of the measuring point in the five-axis CNC machine tool coordinate system, It is the homogeneous coordinate transformation matrix from the measurement coordinate system to the five-axis CNC machine tool coordinate system.

[0092]

[0093] in, M [LT i ] is the theoretical coordinate value of the base station position in the machine tool coordinate system, which is obtained from the CNC system; M [LT i,a ] is the actual coordinate of the base station position in the measurement coordinate system.

[0094] Formula (6) is rewritten into a formula for solving the least squares function, as shown in formula (8); by solving the least squares function, the homogeneous coordinate transformation matrix from the measurement coordinate system to the machine tool coordinate system is determined:

[0095]

[0096] S4, solving the measuring point spatial error caused by the geometric error of the machine tool rotating axis (swing head) in the machine tool coordinate system;

[0097] According to the topological structure of the five-axis machine tool, the transformation matrix from the rotation axis coordinate system to the machine tool coordinate system is determined; thus, the relationship between the measurement point coordinates and the reflector installation position is established, see formula (9). Under the condition that the geometric error of the initial position of the rotation axis is set to 0, the actual initial installation position of the reflector in the B-axis coordinate system is obtained. B [t j,a ]; According to formula (10), the geometric error of the measuring point caused by the geometric error of the rotating axis in the machine tool coordinate system is solved.

[0098]

[0099] in,M [P jk,n ] is the coordinate of the measuring point in the machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the machine tool coordinate system under ideal conditions; B [t j,a ] is the actual initial installation position of the reflector in the B-axis coordinate system.

[0100]

[0101] in, M [ΔP jk,GE ] is the spatial position deviation of the measuring point caused by the B-axis geometric error in the machine tool coordinate system; M [P jk,a ] is the actual three-dimensional coordinate of the measuring point in the machine tool coordinate system; M [P jk,n ] is the coordinate of the measuring point in the machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the machine tool coordinate system under ideal conditions; B [t j,a ] is the actual installation position coordinate of the reflector in the B-axis coordinate system.

[0102] According to the spatial position error caused by the geometric error of the rotating axis obtained above, the geometric error of the rotating axis is separated and identified through step S401 and step S402, as follows:

[0103] Separation and identification of geometric errors of rotating axis (swing head)

[0104] S401, Separation and identification of position-independent errors of the rotating axis (swing head)

[0105] All the measurement point models are grouped into a mode group, that is, formula (11); the solution is M [ΔP jk,GE ]replace M [ΔP jk,PIGE ], and use the least squares principle to solve formula (11), thereby separating the four PIGEs (E AOB ,E COB ,E XOB ,E ZOB ).

[0106] Substitute the four PIGEs of the desired rotation axis into formula (11) to solve the position-independent geometric error caused by the geometric error of the rotation axis: M [ΔP PIGE ].

[0107]

[0108]

[0109]

[0110] in, M [ΔP PIGE ] is the spatial error matrix caused by position-independent errors at all measuring points in the machine tool coordinate system; B PIGE It is the coefficient matrix related to the initial installation position of the reflector and the B-axis rotation angle at all measuring points.

[0111] S402, separation and identification of rotation axis (swing head) position-related errors;

[0112] According to the machine tool coordinate transformation matrix and the definition of the position-related error of the machine tool rotation axis, the identification model of the swing head position-related geometric error is determined, as shown in formula (14). Formula (15) is substituted into formula (14) and the six PDGEs (E AB (b k ),E BB (b k ),E CB (b k ),E XB (b k ),E YB (b k ), E ZB (b k )).

[0113]

[0114] M [ΔP GE-PIGE ]= M [ΔP GE ]- M [ΔP PIGE ] (15)

[0115] Among them, B jk,PDGE is the coefficient matrix related to the initial installation position of the reflector and the B-axis rotation angle.

[0116] In another embodiment of the present invention, a five-axis CNC machine tool swing head geometric error identification system is provided, which can be used to implement the above-mentioned five-axis CNC machine tool swing head geometric error identification method. Specifically, the five-axis CNC machine tool swing head geometric error identification system includes a measurement module, a calibration module, a conversion module and an identification module.

[0117] Among them, the measurement module uses the laser tracking interferometer base station position to establish a measurement coordinate system ( L X, L Y, LZ), using a laser tracking interferometer to track the moving reflector on a five-axis CNC machine tool in real time, and obtaining the distance between the machine tool measuring point and the base station and the distance between each measuring point;

[0118] The calibration module calibrates the laser tracking interferometer base station position and the three-dimensional coordinate value of the machine tool measurement point in the measurement coordinate system according to the distance obtained by the measurement module, determines the measurement coordinate system, and performs homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems.

[0119] Conversion module, using the homogeneous transformation matrix obtained by the calibration module Set the measurement coordinate system ( L X, L Y, L Z) convert the three-dimensional coordinates of the measuring point into the three-dimensional coordinates of the machine tool coordinate system;

[0120] The identification module solves the spatial error of the measuring point caused by the geometric error of the machine tool rotation axis in the machine tool coordinate system obtained by the conversion module, determines the identification model of the geometric error related to the rotation axis position, and uses the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head.

[0121] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0122] Example

[0123] See also Figure 3 In this embodiment, four base stations are used to measure the geometric error of the rotation axis in a time-sharing manner; when each base station is measuring, three reflectors at different positions are installed in sequence to measure the geometric error of the rotation axis; and the measurement coordinate system is calibrated using the rotation rigid body constraint theory.

[0124] The measurement took 100 minutes. By substituting the test data into the calculation program written in MTALAB, 4 PIGEs and 6 PDGEs of different rotation axes of the five-axis CNC machine tool can be obtained, with a total of 20 rotation axis geometric errors. The detection efficiency is extremely high. While ensuring the measurement accuracy, the measurement efficiency of the CNC turntable geometric error is greatly improved, indicating that the five-axis CNC machine tool rotation axis geometric error detection in the present invention has broad engineering application prospects and practical application value.

[0125] In summary, the five-axis CNC machine tool swing head geometric error identification method and system of the present invention greatly improves the measurement efficiency and measurement accuracy, and can reduce the machine tool maintenance cost, improve the machine tool utilization efficiency, and reduce the production cost in engineering applications.

[0126] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0127] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0128] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0129] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0130] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for identifying geometric errors of a five-axis CNC machine tool swing head, characterized in that: The following steps are involved: S1. Use the laser tracking interferometer base station position to establish the measurement coordinate system ( L X, L Y, L Z), using a laser tracking interferometer to track the moving reflector on a five-axis CNC machine tool in real time, and obtaining the distance between the machine tool measuring point and the base station and the distance between each measuring point; S2. Calibrate the three-dimensional coordinates of the laser tracking interferometer base station position and the machine tool measurement point in the measurement coordinate system according to the distance obtained in step S1, determine the measurement coordinate system, and perform homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems. S3, using the homogeneous transformation matrix obtained in step S2 Set the measurement coordinate system ( L X, L Y, L Z) convert the three-dimensional coordinates of the measuring point into the three-dimensional coordinates of the machine tool coordinate system; S4, solving the measuring point spatial error caused by the geometric error of the machine tool rotation axis in the machine tool coordinate system obtained in step S3, determining the identification model of the geometric error related to the rotation axis position, and using the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head, specifically: Determine the transformation matrix from the rotation axis coordinate system to the five-axis CNC machine tool coordinate system, and establish the relationship between the measuring point coordinates and the reflector installation position; solve the actual initial installation position of the reflector in the B-axis coordinate system under the condition that the geometric error of the initial position of the rotation axis is set to 0 B [t j,a ]; solve the geometric error of the measuring point caused by the geometric error of the rotating axis in the coordinate system of the five-axis CNC machine tool, and determine the identification model of the geometric error related to the position of the rotating axis; The relationship between the measuring point coordinates and the reflector installation position is as follows: in, M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual initial installation position of the reflector in the B-axis coordinate system; The specific solution to the geometric error of the measuring point caused by the geometric error of the rotating axis in the coordinate system of the five-axis CNC machine tool is: in, M [ΔP jk,GE ] is the spatial position deviation of the measuring point caused by the B-axis geometric error in the machine tool coordinate system; M [P jk,a ] is the actual three-dimensional coordinate of the measuring point in the machine tool coordinate system; M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual installation position coordinate of the reflector in the B-axis coordinate system; The identification model of the rotation axis position related geometric error is as follows: in, M [ΔP jk,PDGE ] is the position-related geometric error matrix generated by the machine tool during the measurement process in the machine tool coordinate system, B jk,PDGE is the coefficient matrix related to the initial installation position of the reflector and the B-axis rotation angle, E AB (b k ) is the angular error of the B axis around the X axis when the rotation axis rotates to the kth position, E BB (b k ) is the positioning error of the B axis when the rotating axis rotates to the kth position, E CB (b k ) is the angular error of the B axis around the Z axis when the rotating axis rotates to the kth position, E XB (b k ) is the straightness error of the B axis in the X-axis direction when the rotating axis rotates to the kth position, E YB (b k ) is the straightness error of the B axis in the Y axis direction when the rotating axis rotates to the kth position, E ZB (b k ) is the straightness error of the B-axis in the Z-axis direction when the rotating axis rotates to the kth position.

2. The five-axis CNC machine tool swing head geometric error identification method according to claim 1 is characterized in that: Step S1 is specifically as follows: S101. Place the laser tracking interferometer on the five-axis CNC machine tool workbench and install the reflector in the tool coordinate system T-CS. j The position of j represents the jth initial installation position of the reflector j = 1, ..., J, and the three linear axes of the five-axis CNC machine tool are moved so that the laser tracking interferometer is located at LT of the machine tool workspace. i Position, i represents the position of the i-th base station i=1,…,I, the laser tracking interferometer adjusts its own yaw and pitch angles and tracks the moving reflector in real time; S102, B axis rotation angle b k , k represents the kth measuring point k = 1, ..., K, the laser tracking interferometer measures and records the relative distance change L ijk ; S103, laser tracking interferometer moves to the next position LT i+1 , repeat the process of step S102 until all preset laser tracking interferometer base station positions are measured; S104, install the reflector to the next initial position t j+1 , the laser tracking interferometer re-aims and locks the reflector, and repeats steps S102 and S103 until all the machine tool space measurement points arranged in the experiment are measured.

3. The five-axis CNC machine tool swing head geometric error identification method according to claim 1 is characterized in that: In step S2, according to the least squares principle and using the measurement residual u ijk and the residual error r of the rigid body motion constraint condition q , solve the least squares problem by minimizing the residual sum of squares; calculate the optimal solution using the Levenberg-Marquardt nonlinear least squares method Determine the spatial position coordinates of the laser tracking interferometer base station, the actual spatial three-dimensional coordinates of the measuring point and the dead zone length.

4. The five-axis CNC machine tool swing head geometric error identification method according to claim 3 is characterized in that: Solving the least squares function is specifically: Among them, K is the number of measurement points during the rotation of the rotating axis, V is the unknown vector, F is the least squares function, and Q is the number of residual equations.

5. The five-axis CNC machine tool swing head geometric error identification method according to claim 1 is characterized in that: In step S3, the homogeneous transformation matrix Specifically: Among them, I 3×3 is the third-order identity matrix, M [LT i ] is the theoretical coordinate value of the base station position in the machine tool coordinate system, L [LT i,a ] is the actual position of the base station in the measurement coordinate system.

6. A five-axis CNC machine tool swing head geometric error identification system, characterized in that: include: The measurement module uses the laser tracking interferometer base station position to establish the measurement coordinate system ( L X, L Y, L Z), using a laser tracking interferometer to track the moving reflector on a five-axis CNC machine tool in real time, and obtaining the distance between the machine tool measuring point and the base station and the distance between each measuring point; The calibration module calibrates the laser tracking interferometer base station position and the three-dimensional coordinate value of the machine tool measurement point in the measurement coordinate system according to the distance obtained by the measurement module, determines the measurement coordinate system, and performs homogeneous coordinate transformation with the machine tool coordinate system to obtain the homogeneous transformation matrix between the two coordinate systems. Conversion module, using the homogeneous transformation matrix obtained by the calibration module Set the measurement coordinate system ( L X, L Y, L Z) convert the three-dimensional coordinates of the measuring point into the three-dimensional coordinates of the machine tool coordinate system; The identification module solves the spatial error of the measuring point caused by the geometric error of the machine tool rotation axis in the machine tool coordinate system obtained by the conversion module, determines the identification model of the geometric error related to the rotation axis position, and uses the identification model to realize the identification of the geometric error of the five-axis CNC machine tool swing head. Specifically: Determine the transformation matrix from the rotation axis coordinate system to the five-axis CNC machine tool coordinate system, and establish the relationship between the measuring point coordinates and the reflector installation position; solve the actual initial installation position of the reflector in the B-axis coordinate system under the condition that the geometric error of the initial position of the rotation axis is set to 0 B [t j,a ]; solve the geometric error of the measuring point caused by the geometric error of the rotating axis in the coordinate system of the five-axis CNC machine tool, and determine the identification model of the geometric error related to the position of the rotating axis; The relationship between the measuring point coordinates and the reflector installation position is as follows: in, M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual initial installation position of the reflector in the B-axis coordinate system; The specific solution to the geometric error of the measuring point caused by the geometric error of the rotating axis in the coordinate system of the five-axis CNC machine tool is: in, M [ΔP jk,GE ] is the spatial position deviation of the measuring point caused by the B-axis geometric error in the machine tool coordinate system; M [P jk,a ] is the actual three-dimensional coordinate of the measuring point in the machine tool coordinate system; M [P jk,n ] is the coordinate of the measuring point in the five-axis CNC machine tool coordinate system under ideal conditions; is the transformation matrix from the B-axis coordinate system to the five-axis CNC machine tool coordinate system under ideal conditions; B [t j,a ] is the actual installation position coordinate of the reflector in the B-axis coordinate system; The identification model of the rotation axis position related geometric error is as follows: in, M [ΔP jk,PDGE ] is the position-related geometric error matrix generated by the machine tool during the measurement process in the machine tool coordinate system, B jk,PDGE is the coefficient matrix related to the initial installation position of the reflector and the B-axis rotation angle, E AB (b k ) is the angular error of the B axis around the X axis when the rotation axis rotates to the kth position, E BB (b k ) is the positioning error of the B axis when the rotating axis rotates to the kth position, E CB (b k ) is the angular error of the B axis around the Z axis when the rotating axis rotates to the kth position, E XB (b k ) is the straightness error of the B axis in the X-axis direction when the rotating axis rotates to the kth position, E YB (b k ) is the straightness error of the B axis in the Y axis direction when the rotating axis rotates to the kth position, E ZB (b k ) is the straightness error of the B-axis in the Z-axis direction when the rotating axis rotates to the kth position.

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