Error compensation method for double-end driving gantry machine tool

Abstract

The invention discloses an error compensation method for a double-end driving gantry machine tool. The method comprises the following steps: 1, establishing a theoretical transformation matrix of a double-end driving gantry machine tool cutter end, and comparing the theoretical transformation matrix with an actual transformation matrix to obtain an error transmission model of the cutter end; 2, instructions are applied to the two ends of the double-end-drive gantry machine tool at the same time, and a double-drive X-axis, a Y-axis and a Z-axis are driven to move; 3, installing a laser interferometer probe and a reflector at a specified position of each shaft, and measuring by an interferometer to obtain a geometric error; 4, substituting the measured geometric error into the error transfer model, and calculating to obtain a cutter end error; and 5, performing error compensation on the cutter end according to the calculated cutter end error. According to the method, the influence of the double-end driving error on the positioning precision of the tail end of the cutter can be quantitatively evaluated through the error transfer model, the position error is compensated, the machining precision of the double-end driving gantry machine tool is improved, and the problem that the machining precision is insufficient in actual machining is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of numerically controlled machine tools, and particularly to an error compensation method for a double-end drive gantry machine tool. The present invention provides a method for modeling an error transfer model of a double-end drive gantry machine tool, a method for measuring geometric errors of each moving axis, and a tool end error compensation method. Background Art

[0002] With the rapid development of the manufacturing industry, the numerically controlled machine tool industry has also developed rapidly and played an important role in the production and manufacturing processes of some important industries. As a type of numerically controlled machine tool, the gantry machine tool can complete the machining of large parts due to its large span and has a very wide range of application scenarios. The mobile gantry machine tool can carry heavy workpieces, and the guide rails have little wear and the servo motion is stable during use. 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 deformation of the gantry structure or even overturning. However, the symmetric configuration of the double-end drive enables the driving force to act more accurately on the center of gravity of the gantry, ensuring the motion stability and machining 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 the double-end drive error is inevitable.

[0003] The gantry machine tool has a large size and many error sources. Subtle errors and disturbances will cause large deviations at the tool machining end. How to detect various errors, obtain specific error information, obtain the possible error values in advance by establishing a model, compare with the actual error values, and finally optimize the model to obtain more accurate theoretical errors, and seek error compensation methods to improve the machining accuracy of parts has become an urgent problem to be solved in the actual engineering process.

[0004] In the research and improvement of the machining accuracy of machine tools, main influencing factors such as thermal error and geometric error have been widely studied, and a series of mature error analysis, modeling, and compensation technologies have been formed. However, in the existing research on the error sources, modeling, measurement, and compensation of gantry machine tools, there are few studies on double-end drive gantry machine tools, and no clear error model has been established, and there is no wide and effective compensation scheme for the errors caused in the actual use process. In view of the machining requirements of gantry machine tools, not only large machining scales are required, but also the requirements for machining accuracy are getting higher and higher. Machine tool design and manufacturing manufacturers are working hard to improve the machining accuracy and machining efficiency of gantry machine tools while producing large-scale machine tools, and there are more and more studies on the machining accuracy of gantry machine tools. Therefore, the research on error modeling and compensation of double-end drive gantry machine tools has 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 the error, and improve the machining accuracy of the machine tool.

[0006] To achieve the above object, the present invention provides an error compensation method for a double-end drive gantry machine tool, including: an error transfer model of the double-end drive gantry machine tool, measurement of 30 geometric errors of the machine tool, and an error compensation method for the double-end drive gantry machine tool at the tool end, including the following steps: Step 1: Establish a theoretical transformation matrix at the tool end of the double-end drive gantry machine tool, compare it with the actual transformation matrix, and obtain an error transfer model at the tool end; Step 2: Apply commands to both ends (X1 axis and X2 axis) of the double-end drive gantry machine tool simultaneously to drive the double-drive X axis (X1 axis and X2 axis), Y axis, and Z axis to move; Step 3: Install laser interferometer probes and reflectors at specified positions on each axis, and measure the geometric errors through the interferometer; Step 4: Substitute the measured geometric errors into the error transfer model to calculate the tool end errors; Step 5: Perform error compensation on the tool end according to the calculated tool end errors.

[0007] The double-end drive gantry machine tool mentioned above is a four-axis gantry machine tool, which consists of a double-drive X1 axis and X2 axis, Y axis, and Z axis. The left and right columns on the X1 axis and X2 axis drive the crossbeam to move the entire gantry together. The Y-axis slider moves along the Y direction on the crossbeam, driving the Z axis to move together. The Z-axis slider moves along the Z direction on the Z axis, driving the tool to move together.

[0008] Further, for the geometric error parameters in the error transfer model of the double-end drive gantry machine tool, taking the X axis as an example, the six geometric errors of the moving axis are respectively denoted as: 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 moving axes and the movement of the center position of one crossbeam, a total of 30 errors have an error impact on the tool end positioning.

[0009] Further, for the error transfer model of the double-end drive gantry machine tool, first establish a movement transformation matrix between adjacent moving components, and comprehensively calculate and deduce the actual position transformation matrix at the tool end; then compare the actual position transformation matrix with the theoretical position transformation matrix to obtain the error transfer model.

[0010] Further, the 30 geometric error measurements of the machine tool in the error compensation method of the double-end drive gantry machine tool are realized as follows: Install the laser interferometer probe and the reflector 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. Ensure that the entire movement process of the moving axis can be measured during installation. Set the measurement interval, measure the error data multiple times, process the data to obtain various geometric errors, and consider the inevitable differences at both ends in the double-end drive. Measure the errors at both ends of the double drive separately, rather than defaulting that the errors existing at both ends of the double drive are exactly the same and only measuring the error at one end.

[0011] Further, step 4 is specifically realized as follows: For the X1 axis, X2 axis, Y axis, and Z axis, measure the corresponding geometric errors of each axis by sequentially setting the feed values of each axis; for the X3 at the center of the crossbeam, set the X1 and X2 axes to the same feed value, move the same distance at the same speed and acceleration, and measure the corresponding geometric errors at the center of the crossbeam.

[0012] Substitute the geometric errors of each axis and the geometric errors at the center of the crossbeam measured into the error transfer model to calculate the theoretical error value at the tool end , the theoretical error may be positive or negative, which is specifically determined by the errors of the moving axes actually measured. Measure multiple times to construct a comparison table of the tool end displacement and the theoretical error. When a given tool end displacement is given, query the theoretical error through the comparison table , with the theoretical error as the input value, perform error compensation on the motion control instruction of the machine tool tool end. If the instruction for inputting the tool end displacement is , then the actually commanded displacement is , which can effectively improve the motion accuracy of the tool end.

[0013] Further, the theoretical error at the tool end caused by the double-end drive of X1 and X2 is:

[0014]

[0015]

[0016] Where is the theoretical error in the X direction at the tool end caused by the double-end drive, is the theoretical error in the Y direction at the tool end caused by the double-end drive, is the theoretical error in the Z direction at the tool end caused by the double-end drive.

[0017] Further, the theoretical error at the tool end caused by the movement of the Y axis is:

[0018]

[0019]

[0020] Among them is the theoretical error in the X direction of the tool tip caused by the movement of the Y axis, is the theoretical error in the Y direction of the tool tip caused by the movement of the Y axis, is the theoretical error in the Z direction of the tool tip caused by the movement of the Y axis.

[0021] Furthermore, the theoretical error of the tool tip caused by the movement of the Z axis is:

[0022]

[0023]

[0024] Among them is the theoretical error in the X direction of the tool tip caused by the movement of the Z axis, is the theoretical error in the Y direction of the tool tip caused by the movement of the Z axis, is the theoretical error in the Z direction of the tool tip caused by the movement of the Z axis.

[0025] The beneficial effects of the present invention compared with the prior art are as follows: First, the error transfer model established by the present invention fully considers the asynchronous situation of the dual drives of the gantry machine tool with dual-end drives, and can more accurately predict the tool tip error of the gantry machine tool with dual-end drives; second, the present invention uses a laser interferometer to measure all geometric errors of one moving axis with one installation, 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 errors generated at the tool tip during the operation of the dual-end drive machine tool, and improve the machining accuracy of the machine tool. Description of the Drawings

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is the flowchart of the error compensation method for the gantry machine tool with dual-end drives according to an embodiment of the present invention; Figure 2Schematic diagram of the structure of a four-axis double-drive gantry machine tool according to an embodiment of the present invention; Figure 3 Schematic diagram of the six geometric errors of a single axis according to an embodiment of the present invention; Figure 4 Schematic diagram of the double-end drive X-direction marking according to an embodiment of the present invention; Figure 5 Schematic diagram of the component numbers of each part of a double-end drive gantry machine tool according to an embodiment of the present invention; Figure 6 Schematic diagram of the topological structure of the motion chain of a double-end drive gantry machine tool according to an embodiment of the present invention; Figure 7 Schematic diagram of the installation method of a laser interferometer for measuring the geometric errors of a horizontal motion axis according to an embodiment of the present invention; Figure 8 Schematic diagram of the installation method of a laser interferometer for measuring the geometric errors of a vertical motion axis according to an embodiment of the present invention. Detailed implementation manners

[0028] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The following will specifically describe the present invention in conjunction with the drawings and embodiments.

[0029] As Figure 1 shown is an error compensation method for a double-end drive gantry machine tool according to an embodiment of the present invention, and this method includes Step 1 to Step 5.

[0030] Step 1: Establish a theoretical transformation matrix at the tool end of the double-end drive gantry machine tool, compare it with the actual transformation matrix, and obtain the error transfer model at the tool end; Step 2: Apply commands to both ends (X1 axis and X2 axis) of the double-end drive gantry machine tool simultaneously to drive the double-drive X axis (X1 axis and X2 axis), Y axis, and Z axis to move; Step 3: Install laser interferometer probes and reflectors at specified positions on each axis, and measure the geometric errors through the interferometer; Step 4: Substitute the measured geometric errors into the error transfer model to calculate the tool end errors; Step 5: Perform error compensation on the tool end according to the calculated tool end errors.

[0031] As Figure 2As shown in the figure, a double-end drive gantry machine tool is composed of a double-driven X1 axis, an X2 axis, a Y axis, and a Z axis. The left and right columns on the X1 axis and the X2 axis drive the crossbeam to move the entire gantry together. The crossbeam slider moves along the Y direction on the crossbeam, driving the Z axis to move together. The Z axis slider moves along the Z direction on the Z axis, driving the tool to move together.

[0032] As Figure 4 shown, when establishing the machine tool error transfer model, the two ends of the double-driven X axis are respectively marked as X1 and X2, and the center of the gantry crossbeam is marked as X3. The motion transformation matrices from the bed to the two ends of the X axis and the crossbeam center can be obtained, and then the motion transformation matrices from the crossbeam center to the crossbeam slider, from the crossbeam slider to the Z axis slider, and from the Z axis slider to the tool, as well as the error transfer model from the bed to the tool, can be obtained.

[0033] When modeling based on the multi-body system theory, a general double-end drive gantry machine tool is numbered, as Figure 5 shown: the bed is 0; the movement of the entire gantry in the X direction is driven separately on both sides. The left and right columns drive the crossbeam to move together. The movement of the entire gantry in the X axis direction is divided into three parts: the left column, the right column, and the crossbeam center. The left and right columns are 1 and 2 respectively, and the crossbeam center is 3; the slider moving along the Y axis on the crossbeam is 4; the slider moving along the Z axis is 5; the tool is 6. The topological structure of the machine tool motion chain is as Figure 6 shown.

[0034] Furthermore, according to the classical multi-body system theory and the homogeneous coordinate transformation method, ignoring higher-order infinitesimals, the transformation matrices from the bed 0 to the left column 1, the right column 2, and the crossbeam center 3 when the gantry structure feeds in the X direction are respectively:

[0035]

[0036]

[0037] Among them, , , are the actual displacements of the left column 1, the right column 2, and the crossbeam center 3 along the direction respectively. Ignoring the torsional deformation of the gantry structure, there will be no relative rotation between the left column 1, the right column 2, and the crossbeam center 3 during the movement, that is:

[0038]

[0039]

[0040]

[0041] Ignoring the tension or compression of the gantry structure, the straightness errors in the same direction are equal, i.e.:

[0042]

[0043]

[0044] The errors of the left column 1 and the right column 2 jointly determine the error of the crossbeam center 3, i.e.:

[0045] The displacements of the left column 1 and the right column 2 jointly determine the displacement of the crossbeam center 3, i.e.:

[0046] Therefore, the transformation matrix from the bed 0 to the left column 1 and from the left column 1 to the crossbeam center 3 is written as:

[0047]

[0048] Similarly, when the gantry structure feeds in the Y direction the transformation matrix from the crossbeam center 3 to the crossbeam slider 4 is:

[0049] When the gantry structure feeds in the Z direction the transformation matrix from the crossbeam slider 4 to the Z-axis slider 5 is:

[0050] There is no relative movement between the Z-axis slider 5 and the tool 6, and the transformation matrix is the identity matrix:

[0051] Under ideal conditions, the transformation matrix from the bed 0 to the tool 6 is:

[0052] In actual situations, the transformation matrix from the bed 0 to the tool 6 is:

[0053] Through comprehensive calculation and derivation, the actual position transformation matrix from the bed 0 to the tool 6 is Let the theoretical position transformation matrix under ideal conditions be and the error transfer model be then there is where:

[0054]

[0055] In step 3, reflectors and laser interferometers are installed on each moving axis of the machine tool. The installation method for the horizontal moving axis is as follows Figure 7 shown. It is possible to choose to move the reflector along with the axis or move the interferometer along with the axis. In the present invention, it is chosen to move the reflector along with the axis. The laser interferometer probe 73 is installed on the machine tool bed or the mounting surface 71 that remains stationary with the bed through the bracket 72. Reflectors 74 are installed on the X1 axis, X2 axis, the center X3 of the crossbeam, or the Y axis 75 that move along the horizontal plane. The laser starts from the laser interferometer probe 73, 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 shown by the arrow, six geometric errors of this axis can be measured. The Z axis moves in the vertical direction, and it is necessary to change the laser direction through the turning mirror 85. As Figure 8 shown, the laser interferometer probe 83 is installed on the machine tool bed or the mounting surface 81 that remains stationary with the bed through the bracket 82. The turning mirror 85 is installed through the bracket 84. Reflectors 86 are installed on the Z axis 87 that moves along the vertical direction. The laser starts from the laser interferometer probe 83, hits the turning mirror 85, changes the laser direction, so that the laser hits the reflector 86, and the laser is reflected back to the laser interferometer probe 83 through the turning mirror 85. When the Z axis moves in the vertical direction in the direction shown by the arrow, six geometric errors of the Z axis can be measured.

[0056] The finally measured 30 geometric errors are shown in Table 1, including six geometric errors for each of the four moving axes X1, X2, Y, Z and the center X3 of one crossbeam.

[0057] Table 1

[0058] The embodiments described above are only a preferred solution of the present invention, but it is not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. An error compensation method for 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: Apply instructions to both ends of the double-end drive gantry machine tool at the same time to drive the double-drive X-axis, Y-axis, and Z-axis to move; Step 3: Install the laser interferometer probe and the 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: According to the calculated tool end error, perform error compensation on the tool end.

2. The error compensation method for a double-end drive gantry machine tool according to claim 1, characterized in that: The 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 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.

3. The error compensation method for a double-end drive gantry machine tool according to claim 1, characterized in that: The six geometric errors of the X-axis are recorded 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 runout error of the X-axis around the Z-axis is ; Based on the need to consider the movement of four motion axes and a center position at the same time, a total of 30 errors that affect the tool end positioning are statistically analyzed.

4. The error compensation method for a double-end drive gantry machine tool according to claim 3, characterized in that: First, the motion transformation matrix between adjacent moving parts is established, and the actual position transformation matrix of the tool end is derived by 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. , the ideal transformation matrix is , the error matrix is , and there is ; in: ； 。 5. The error compensation method for a double-end drive gantry machine tool according to claim 4, 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 the high-order infinitesimal quantities, the gantry structure feeds along the X direction. The transformation matrices from the bed to the left column, right column, and beam center are: ； ； ； in, , , They are the left column, right column, and the center edge of the beam. The actual displacement in the direction, ignoring the distortion of the gantry structure, will not cause relative rotation between the left column, the right column and the center of the beam during the movement, that is: ； ； ； ； Ignoring the stretching or squeezing of the gantry structure, the straightness errors in the same direction are equal, that is: ； ； ； The errors of the left and right columns jointly determine the error of the beam center, that is: ； The displacement of the left column and the right column jointly determine the displacement of the center of the beam, 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, the gantry structure feeds in the Y direction When , the transformation matrix from the center of the beam to the beam slider is: ； Gantry structure feeds in Z direction When , the transformation matrix from the crossbar 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 bed 0 to tool 6 is: ； In actual situations, the transformation matrix from bed 0 to tool 6 is: 。 6. The error compensation method of the double-end drive gantry machine tool according to claim 3, 4 or 5, 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 that needs 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 double-ended drive, the errors at both ends of the double-ended drive are measured separately.

7. The error compensation method for a double-end drive gantry machine tool according to claim 6, characterized in that: The error compensation of the double-end drive gantry machine tool at the tool end is as follows: For the X1 axis, X2 axis, Y axis, and Z axis, the feed value of each axis is set in turn to measure the corresponding geometric error of each axis; 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 corresponding geometric error of the beam center is measured; The measured geometric errors of each axis and the center of the beam are introduced into the error transfer model to calculate the theoretical error value of the tool end. , theoretical error Positive or negative, it is determined by the actual measured motion axis error; multiple measurements are made to build a comparison table of 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 command is , which can effectively improve the motion accuracy of the tool end.

8. The error compensation method for a double-end drive gantry machine tool according to claim 7, characterized in that: The theoretical tool end error caused by the X1 and X2 double-end drive is: ； ； ； 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.

9. The error compensation method for a double-end drive gantry machine tool according to claim 7, characterized in that: The theoretical positioning error of the tool end caused by the Y-axis motion is: ； ； ； in is the positioning error of the tool end in the X direction caused by the Y-axis motion, is the Y-direction positioning error of the tool end caused by the Y-axis motion, The Z-direction positioning error of the tool end caused by the Y-axis motion.

10. The error compensation method for a double-end drive gantry machine tool according to claim 7, characterized in that: The theoretical positioning error of the tool end caused by the Z-axis motion is: ； ； ； in is the tool end X-direction positioning error caused by Z-axis motion, is the Y-direction positioning error of the tool end caused by the Z-axis motion, The Z-axis positioning error of the tool end caused by the Z-axis motion.

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