An error compensation method for double-end drive gantry machine tools

Abstract

The present invention discloses an error compensation method for a double-end drive gantry machine tool. The present invention comprises the following steps: 1. establishing a theoretical transformation matrix of the tool end of the double-end drive gantry machine tool, comparing it with the actual transformation matrix, and obtaining an error transfer model of the tool end; 2. simultaneously applying instructions to both ends of the double-end drive gantry machine tool to drive the movement of the double-drive X-axis, Y-axis, and Z-axis; 3. installing a laser interferometer probe and a reflector at a specified position of each axis, and obtaining geometric errors through interferometer measurement; 4. substituting the measured geometric errors into the error transfer model to calculate the tool end error; 5. performing error compensation on the tool end based on the calculated tool end error. The method of the present invention can quantitatively evaluate the influence of the double-end drive error on the positioning accuracy of the tool end through the error transfer model, compensate for the position error, improve the machining accuracy of the double-end drive gantry machine tool, and solve the problem of insufficient machining accuracy in actual machining.

Description

Technical Field

[0001] The present invention relates to the technical field of CNC machine tools, and in particular to an error compensation method for a double-ended drive gantry machine tool. The present invention provides a method for modeling an error transmission model for a double-ended drive gantry machine tool, a method for measuring the geometric errors of each motion axis, and a method for compensating tool end errors. Background Art

[0002] With the rapid development of the manufacturing industry, the CNC machine tool industry has also developed rapidly, playing an important role in the production and manufacturing processes of some important industries. As a type of CNC machine tool, the gantry machine tool is able to complete the processing of large parts due to its large span, and its application scenarios are very wide. The mobile gantry machine tool can carry heavy workpieces, and the guide rails wear less during use and the servo motion is stable. Because the moving part of the mobile gantry machine tool has a large mass, the driving force of the traditional single-end drive cannot accurately act on the center of gravity of the gantry, which may cause the gantry structure to deform or even overturn. The symmetrical configuration of the double-end drive allows the driving force to act more accurately on the center of gravity of the gantry, ensuring motion stability and processing accuracy. However, there are inevitable differences in the driving conditions at both ends of the double-end drive and the components in the structure, and double-end drive errors are difficult to avoid.

[0003] Gantry machine tools are large in size and have many sources of errors. Minor errors and disturbances can cause large deviations on the tool processing end. How to detect various errors, obtain specific error information, obtain possible error values in advance by establishing a model, compare the actual error values, and finally optimize the model to obtain more accurate theoretical errors, seek error compensation methods, and improve the accuracy of part processing has become an urgent problem to be solved in the actual engineering process.

[0004] In the process of researching and improving machine tool machining accuracy, major influencing factors such as thermal error and geometric error have been extensively studied, resulting in a series of mature error analysis, modeling, and compensation technologies. However, in existing research on the sources, modeling, measurement, and compensation of gantry machine tools, there is relatively little research on double-end drive gantry machine tools. No clear error model has been established, and there is no widely effective compensation solution for the errors caused during actual use. The machining requirements of gantry machine tools are not only large-scale, but also increasingly demanding machining accuracy. While producing large-scale machine tools, machine tool designers and manufacturers are striving to improve the machining accuracy and efficiency of gantry machine tools, and research on gantry machine tool machining accuracy is also increasing. Therefore, research on error modeling and compensation for double-end drive gantry machine tools is of practical significance. Summary of the Invention

[0005] The purpose of the present invention is to provide an error compensation method for a double-end drive gantry machine tool, which can accurately calculate the tool end position error, effectively compensate for the error, and improve the machining accuracy of the machine tool.

[0006] To achieve the above objectives, the present invention provides an error compensation method for a double-end drive gantry machine tool, comprising: an error transmission model for a double-end drive gantry machine tool, 30 geometric error measurements of the machine tool, and an error compensation method for a double-end drive gantry machine tool on the tool end, comprising the following steps:

[0007] Step 1: Establish a theoretical transformation matrix of the tool end of the double-end drive gantry machine tool, compare it with the actual transformation matrix, and obtain the error transfer model of the tool end;

[0008] Step 2: Simultaneously apply commands to both ends of the double-drive gantry machine tool (X1 axis and X2 axis) to drive the dual-drive X axis (X1 axis and X2 axis), Y axis, and Z axis to move;

[0009] Step 3: Install the laser interferometer probe and reflector at the specified position of each axis, and obtain the geometric error through interferometer measurement;

[0010] Step 4: Substitute the measured geometric error into the error transfer model to calculate the tool end error;

[0011] Step 5: Compensate the tool end error based on the calculated tool end error.

[0012] The double-end drive gantry machine tool mentioned therein is a four-axis gantry machine tool, which consists of dual-drive X1 axis and X2 axis, Y axis and Z axis. The left and right columns on the X1 axis and X2 axis move the gantry as a whole with the crossbeam. The Y-axis slider moves along the Y direction on the crossbeam and moves with the Z axis. The Z-axis slider moves along the Z direction on the Z axis and moves with the tool.

[0013] Furthermore, the geometric error parameters in the error transfer model of the double-end drive gantry machine tool are as follows: the positioning error of the X-axis in the X direction is , the straightness error of the X-axis in the Y direction is , the straightness error of the X-axis in the Z direction is , the tilt error of the X-axis around the X-axis is , the pitch error of the X axis around the Y axis is , the yaw error of the X-axis around the Z-axis is , considering the movement of four motion axes and the center position of a beam, a total of 30 errors have an error effect on the tool end positioning.

[0014] Furthermore, the error transfer model of the double-end drive gantry machine tool first establishes a motion transformation matrix between adjacent moving parts, and comprehensively calculates and derives the actual position transformation matrix of the tool end; then the actual position transformation matrix is compared with the theoretical position transformation matrix to obtain the error transfer model.

[0015] Furthermore, the 30 geometric error measurements of the machine tool in the error compensation method of the double-end drive gantry machine tool are implemented as follows: the laser interferometer probe and the reflector are installed on the moving axis to be measured, one of the laser interferometer probe and the reflector is fixed, and the other moves with the moving axis. During installation, it is ensured that the entire movement process of the moving axis can be measured, the measurement interval is set, and the error data is obtained by multiple measurements. The data is processed to obtain various geometric errors. Considering the inevitable differences between the two ends in the double-end drive, the errors at both ends of the dual drive are measured separately, instead of assuming that the errors at both ends of the dual drive are exactly the same and only measuring the error at one end.

[0016] Furthermore, step 4 is specifically implemented as follows: for the X1 axis, X2 axis, Y axis, and Z axis, the feed value of each axis is set in turn, and the geometric error corresponding to each axis is measured; for the beam center X3, the X1 and X2 axes are set to the same feed value and move the same distance at the same speed and acceleration, and the geometric error corresponding to the beam center is measured.

[0017] The measured geometric errors of each axis and the center of the beam are brought into the error transfer model to calculate the theoretical error value of the tool end. , theoretical error It may be positive or negative, which is determined by the actual measured motion axis error. Multiple measurements are made to build a comparison table between tool end displacement and theoretical error. When the tool end displacement is given, the theoretical error is obtained by querying the comparison table. , with theoretical error As the input value, the error compensation is performed on the motion control command of the machine tool tool end. If the input command of the tool end displacement is , then the displacement controlled by the actual instruction is , which can effectively improve the motion accuracy of the tool end.

[0018] Furthermore, the theoretical error of the tool end caused by the double-end drive of X1 and X2 is:

[0019]

[0020]

[0021]

[0022] in is the theoretical error in the X direction of the tool end caused by the double-end drive, is the theoretical error in the Y direction of the tool end caused by the double-end drive, Theoretical error in the Z direction of the tool end caused by double-end drive.

[0023] Furthermore, the theoretical error of the tool end caused by the Y-axis motion is:

[0024]

[0025]

[0026]

[0027] in is the theoretical error in the X direction of the tool end caused by the Y-axis motion, is the theoretical error in the Y direction of the tool end caused by the Y-axis motion, Theoretical error in the Z direction of the tool end caused by the Y-axis motion.

[0028] Furthermore, the theoretical error of the tool end caused by the Z-axis motion is:

[0029]

[0030]

[0031]

[0032] in is the theoretical error in the X direction of the tool end caused by the Z-axis motion, is the theoretical error in the Y direction of the tool end caused by the Z-axis motion, Theoretical error in the Z direction of the tool end caused by Z-axis motion.

[0033] The beneficial effects of the present invention compared to the prior art are:

[0034] First, the error transfer model established by the present invention fully considers the dual-drive asynchronous situation of the dual-end drive gantry machine tool, and can more accurately predict the tool end error of the dual-end drive gantry machine tool; second, the present invention uses a laser interferometer to install and measure all geometric errors of a moving axis at one time, which can avoid the influence of external errors caused by multiple installations on the accuracy of error prediction; third, the error compensation method provided by the present invention can effectively compensate for the error caused to the tool end of the dual-end drive machine tool during operation, thereby improving the machining accuracy of the machine tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1This is a flow chart of an error compensation method for a double-end drive gantry machine tool according to an embodiment of the present invention;

[0037] Figure 2 This is a structural diagram of a four-axis dual-drive gantry machine tool according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of six geometric errors of a single axis according to an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of a double-ended drive X-direction mark according to an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the component numbers of a double-end drive gantry machine tool according to an embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of the topological structure of the kinematic chain of a double-end drive gantry machine tool according to an embodiment of the present invention;

[0042] Figure 7 Schematic diagram of a method for measuring and installing a laser interferometer for geometric errors of a horizontal motion axis according to an embodiment of the present invention;

[0043] Figure 8 It is a schematic diagram of a method for installing a laser interferometer to measure geometric errors of a vertical motion axis according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions in the present invention, 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 only 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 making creative work should fall within the scope of protection of the present invention. The present invention is described in detail below in conjunction with the drawings and examples.

[0045] like Figure 1 FIG2 shows an error compensation method for a double-end drive gantry machine tool according to an embodiment of the present invention, which includes steps 1 to 5.

[0046] Step 1: Establish a theoretical transformation matrix of the tool end of the double-end drive gantry machine tool, compare it with the actual transformation matrix, and obtain the error transfer model of the tool end;

[0047] Step 2: Simultaneously apply commands to both ends of the double-drive gantry machine tool (X1 axis and X2 axis) to drive the dual-drive X axis (X1 axis and X2 axis), Y axis, and Z axis to move;

[0048] Step 3: Install the laser interferometer probe and reflector at the specified position of each axis, and measure the geometric error through the interferometer;

[0049] Step 4: Substitute the measured geometric error into the error transfer model to calculate the tool end error;

[0050] Step 5: Compensate the tool end error based on the calculated tool end error.

[0051] like Figure 2 As shown, a double-end drive gantry machine tool consists of dual-drive X1 and X2 axes, Y and Z axes. The left and right columns on the X1 and X2 axes move the gantry as a whole with the crossbeam. The crossbeam slider moves along the Y direction on the crossbeam and moves with the Z axis. The Z axis slider moves along the Z direction on the Z axis and moves with the tool.

[0052] like Figure 4 As shown in Figure 1, when establishing the machine tool error transfer model, the two ends of the dual-drive X-axis are labeled X1 and X2, respectively, and the center of the gantry beam is labeled X3. This allows us to obtain the kinematic transformation matrices from the bed to the two ends of the X-axis and the center of the beam. Furthermore, we can obtain the kinematic transformation matrices from the center of the beam to the beam slider, the beam slider to the Z-axis slider, and the Z-axis slider to the tool, as well as the error transfer model from the bed to the tool.

[0053] When modeling based on multi-body system theory, the general double-end drive gantry machine tool is numbered, such as Figure 5 As shown: the bed is 0; the movement of the gantry in the X direction is driven by the left and right sides respectively, and the left and right columns move together with the crossbeam. The movement of the gantry in the X-axis direction is divided into three parts: the left column, the right column, and the center of the crossbeam. The left and right columns are 1 and 2 respectively, and the center of the crossbeam is 3; the slider moving along the Y axis on the crossbeam is 4; the slider moving along the Z axis is 5; and the tool is 6. The topological structure of the machine tool kinematic chain is as follows Figure 6 shown.

[0054] Furthermore, according to the classical multi-body system theory and homogeneous coordinate transformation method, ignoring the high-order infinitesimal quantities, the gantry structure feeds along the X direction. The transformation matrices from bed 0 to left column 1, right column 2, and beam center 3 are:

[0055]

[0056]

[0057]

[0058] in, 、 、 They are respectively left column 1, right column 2, and beam center 3 along The actual displacement in the direction, ignoring the distortion of the gantry structure, does not cause relative rotation between the left column 1, the right column 2, and the beam center 3 during the movement, that is:

[0059]

[0060]

[0061]

[0062]

[0063] Ignoring the stretching or squeezing of the gantry structure, the straightness errors in the same direction are equal, that is:

[0064]

[0065]

[0066]

[0067] The errors of the left column 1 and the right column 2 jointly determine the error of the beam center 3, that is:

[0068]

[0069] The displacement of the left column 1 and the right column 2 jointly determine the displacement of the beam center 3, that is:

[0070]

[0071] Therefore, the transformation matrix from bed 0 to left column 1 and left column 1 to beam center 3 is written as:

[0072]

[0073]

[0074] Similarly, the gantry structure feeds in the Y direction When , the transformation matrix from the beam center 3 to the beam slider 4 is:

[0075]

[0076] Gantry structure feeds in Z direction When , the transformation matrix from the crossbeam slider 4 to the Z-axis slider 5 is:

[0077]

[0078] There is no relative motion between the Z-axis slider 5 and the tool 6, and the transformation matrix is the unit matrix:

[0079]

[0080] Ideally, the transformation matrix from bed 0 to tool 6 is:

[0081]

[0082] In actual situations, the transformation matrix from bed 0 to tool 6 is:

[0083]

[0084] The actual position transformation matrix from bed 0 to tool 6 is derived by comprehensive calculation: , assuming the theoretical position transformation matrix under ideal conditions is , the error transmission model is , then ,in:

[0085]

[0086]

[0087] In step 3, install the reflector and laser interferometer on each motion axis of the machine tool. The installation method of the horizontal motion axis is as follows: Figure 7 As shown, the reflector can be selected to move with the axis or the interferometer can be selected to move with the axis. The present invention selects the reflector to move with the axis. The laser interferometer probe 73 is installed on the machine bed or the mounting surface 71 that remains stationary with the bed through the bracket 72. The reflector 74 is installed on the X1 axis, X2 axis, beam center X3 or Y axis 75 that move along the horizontal plane. The laser starts from the laser interferometer probe 73 and hits the reflector 74, and is reflected back to the laser interferometer probe 73. When the moving axis moves in the horizontal plane in the direction indicated by the arrow, the six geometric errors of the axis can be measured. The Z axis moves in the vertical direction, and the laser direction needs to be changed by the steering mirror 85, as shown in FIG. Figure 8 As shown, a laser interferometer probe 83 is installed on a machine tool bed or a mounting surface 81 that remains stationary with the bed through a bracket 82, a steering mirror 85 is installed through a bracket 84, and a reflector 86 is installed on a Z-axis 87 that moves in the vertical direction. The laser starts from the laser interferometer probe 83 and hits the steering mirror 85, changing the direction of the laser so that the laser hits the reflector 86. The laser is reflected through the steering mirror 85 and returns to the laser interferometer probe 83. When the Z-axis moves in the vertical direction as indicated by the arrow, six geometric errors of the Z-axis can be measured.

[0088] The 30 geometric errors finally measured are shown in Table 1, including 6 geometric errors of the four motion axes X1, X2, Y, and Z and the center of the beam X3.

[0089] Table 1

[0090]

[0091] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for compensating an error of a double-end drive gantry machine tool, characterized in that: The following steps are involved: Step 1: Establish a theoretical transformation matrix of the tool end of the double-end drive gantry machine tool, compare it with the actual transformation matrix, and obtain the error transfer model of the tool end; Step 2: Simultaneously apply commands to both ends of the double-drive gantry machine tool to drive the dual-drive X1 and X2 axes, Y axis, and Z axis to move; Step 3: Install the laser interferometer probe and reflector at the specified position of each axis, and obtain the geometric error through interferometer measurement; Step 4: Substitute the measured geometric error into the error transfer model to calculate the tool end error; Step 5: Compensate the tool end error based on the calculated tool end error; The six geometric errors of the X1 axis are recorded as follows: The positioning error of the X1 axis in the X direction is δ x (x1), the straightness error of the X1 axis in the Y direction is δ y (x1), the straightness error of the X1 axis in the Z direction is δ z (x1), the tilt error of the X1 axis around the X1 axis is ε x (x1), the pitch error of the X1 axis around the Y axis is ε y (x1), the yaw error of the X1 axis around the Z axis is ε z (x1); Since it is necessary to simultaneously consider the six geometric errors of the four motion axes X1, X2, Y, and Z, as well as the six geometric errors of the beam center X3, a total of 30 errors are statistically analyzed to determine the error effects on the tool end positioning; First, the motion transformation matrix between adjacent moving parts is established, and the actual position transformation matrix of the tool end is derived through comprehensive calculation; then the actual position transformation matrix is compared with the theoretical position transformation matrix to obtain the error transmission model; finally, the transformation matrix from the bed to the tool is obtained. In the ideal state, the transformation matrix is The error matrix is And there is in:

2. The error compensation method for a double-end drive gantry machine tool according to claim 1, characterized in that: This double-end drive gantry machine tool consists of dual-drive X1 and X2 axes, Y and Z axes. The left and right columns on the X1 and X2 axes move the gantry as a whole with the crossbeam. The Y-axis slider moves in the Y direction on the crossbeam and moves with the Z axis. The Z-axis slider moves in the Z direction on the Z axis and moves with the tool.

3. The error compensation method for a double-end drive gantry machine tool according to claim 1, characterized in that: The transformation matrix is The specific derivation is as follows: According to the classical multi-body system theory and homogeneous coordinate transformation method, ignoring high-order infinitesimals, the transformation matrices from the bed to the left column, right column, and beam center when the gantry structure feeds x along the X direction are obtained as follows: Among them, x1, x2, and x3 are the actual displacements of the left column, right column, and beam centers along the X direction, respectively. Ignoring the distortion of the gantry structure, there will be no relative rotation between the left column, right column, and beam centers during the movement, that is: e x (x3)=e y (x3)=e z (x3)=0; e x (x1)=e x (x2); e y (x1)=e y (x2); e z (x1)=e z (x2); Ignoring the stretching or squeezing of the gantry structure, the straightness errors in the same direction are equal, that is: δ y (x3)=δ z (x3)=0; d z (x1)=δ z (x2); d y (x1)=δ y (x2); The errors of the left and right columns jointly determine the error of the beam center, that is: The displacement of the left and right columns jointly determine the displacement of the beam center, that is: Therefore, the transformation matrix from the bed to the left column and from the left column to the center of the beam is written as: Similarly, when the gantry structure feeds y in the Y direction, the transformation matrix from the center of the beam to the beam slider is: When the gantry structure feeds z in the Z direction, the transformation matrix from the crossbeam slider to the Z-axis slider is: There is no relative motion between the Z-axis slider and the tool, and the transformation matrix is the unit matrix: Ideally, the transformation matrix from the bed to the tool is: In practice, the transformation matrix from the bed to the tool is:

4. The error compensation method for a double-end drive gantry machine tool according to claim 2 or 3, characterized in that: The 30 geometric errors of the machine tool in this method are measured as follows: the laser interferometer probe and the reflector are installed on the moving axis to be measured. One of the laser interferometer probe and the reflector is fixed, and the other moves with the moving axis. During installation, it is ensured that the entire movement process of the moving axis can be measured. The measurement interval is set, and the error data is obtained by multiple measurements. The data is processed to obtain various geometric errors. Considering the inevitable differences between the two ends of the dual-end drive, the errors at both ends of the dual drive are measured separately.

5. The error compensation method for a double-end drive gantry machine tool according to claim 4, characterized in that: Error compensation for the double-ended drive gantry machine tool at the tool end is as follows: For the X1, X2, Y, and Z axes, the feed values of each axis are set in sequence to measure the corresponding geometric errors of each axis. For the beam center X3, the X1 and X2 axes are set to the same feed value, move the same distance at the same speed and acceleration, and measure the corresponding geometric errors of the beam center. The measured geometric errors of each axis and the geometric errors of the beam center are brought into the error transfer model to calculate the theoretical error value e of the tool end. Whether the theoretical error e is positive or negative is determined by the actual measured motion axis error. Multiple measurements are performed to construct a comparison table of tool end displacement and theoretical error. When the tool end displacement is given, the theoretical error e is obtained by querying the comparison table. The theoretical error e is used as the input value to perform error compensation on the machine tool tool end motion control command. If the input tool end displacement command is x, the displacement controlled by the actual command is x+e, which can effectively improve the tool end motion accuracy.

6. The error compensation method for a double-end drive gantry machine tool according to claim 5, characterized in that: The theoretical error of the tool end caused by the X1 and X2 double-end drive is: E y (x)=2δ y (x1)-zε x (x1); E z (x)62δ z (x1)+yes x (x1) Among them E x (x) is the theoretical error in the X direction of the tool end caused by the double-end drive, E y (x) is the theoretical error in the Y direction of the tool end caused by the double-end drive, E z (x) Theoretical error in the Z direction of the tool end caused by double-end drive.

7. The error compensation method for a double-end drive gantry machine tool according to claim 6, characterized in that: The theoretical positioning error of the tool end caused by the Y-axis motion is: E x (y)=δ x (y)+zε y (y); E y (y)=δ y (y)-zε x (y); AND z (y)=δ z (and); Among them E x (y) is the X-direction positioning error of the tool end caused by the Y-axis motion, E y (y) is the Y-direction positioning error of the tool end caused by the Y-axis motion, E z (y) Z-direction positioning error of the tool end caused by the Y-axis motion.

8. The error compensation method for a double-end drive gantry machine tool according to claim 6, characterized in that: The theoretical positioning error of the tool end caused by Z-axis motion is: E x (z)=δ x (With); E y (y)=δ y (With); E z (z)=δ z (With); Among them E x (z) is the X-direction positioning error of the tool end caused by the Z-axis motion, E y (z) is the Y-direction positioning error of the tool end caused by the Z-axis motion, E z (z) Z-axis positioning error of the tool end caused by Z-axis motion.

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