Line laser installation pose calibration method based on section line method and suitable for series-parallel machine tool

Abstract

The invention discloses a section line method-based line laser installation pose calibration method suitable for a series-parallel machine tool. A standard ball is clamped on a main shaft, it is ensured that the center position of the standard ball is unchanged, the intersection face of the line laser and the standard ball is a circle, and the center coordinate is calculated by fitting the circle center. And establishing an equation by using the invariable position of the center of sphere to obtain a rotation matrix representing the mounting posture of the line laser sensor. The absolute coordinates of the standard ball are obtained by analyzing the relation between coordinate systems on the two sides of the equipment. And adjusting the axis of the machine tool tail end coordinate system to be parallel to the axis of the base coordinate system, translating the machine tool to measure the standard ball, and storing point cloud data. After filtering processing is carried out on the collected point cloud data, sphere center coordinates are obtained by fitting a spherical surface, difference comparison is carried out on the fitted sphere center coordinates and a known sphere center true value, and the deviation between the origin of the coordinates of the line laser sensor and the origin of a tail end coordinate system is solved. In the whole calibration process, calibration of the installation pose of the line laser sensor can be completed without changing the pose of the series-parallel mechanism.

Description

Technical Field

[0001] The present invention belongs to the field of measurement technology, and in particular, relates to a linear laser measurement posture calibration method for a series-parallel machine tool based on a cross-section line method. Background Art

[0002] The line laser sensor is integrated into the end of the actuator of the serial-parallel machine tool. The serial-parallel machine tool drives the line laser sensor to perform scanning and measurement according to the theoretical contour of the workpiece. This can realize the rapid scanning and acquisition of the actual contour of large-sized thin-walled components, which is an effective means to ensure the processing quality of such parts. In practical applications, the installation error and posture deviation of the line laser sensor are inevitable, which leads to the deviation of the measurement system motion chain built based on the theoretical model, resulting in systematic errors in the measurement results of the workpiece surface morphology. These errors will accumulate in the subsequent processing process and seriously affect the processing accuracy. Therefore, it is necessary to calibrate the sensor measurement position and posture after completing the installation of the line laser sensor, and identify the translation matrix and rotation matrix of the measurement system motion chain, so as to effectively eliminate the systematic error and ensure the processing accuracy.

[0003] For the problem of linear laser sensor posture calibration, the existing methods mainly control the linear laser sensor to measure the standard ball from different angles by changing the machine tool posture multiple times. Based on the fact that the position of the standard ball remains unchanged in the machine tool base coordinate system, an equation is established to obtain the translation matrix and rotation matrix that characterize the installation posture of the linear laser sensor, so as to realize the calibration of the linear laser sensor posture. However, this method is mainly applicable to serial machine tools with high positioning accuracy. For serial-parallel machine tools, their positioning accuracy is much lower than that of serial machine tools. By changing the measurement posture of the serial-parallel machine tool multiple times for posture calibration, the positioning error of the serial-parallel machine tool itself will be introduced, and this positioning error cannot be ignored. Therefore, the linear laser sensor posture calibration for serial-parallel machine tools must effectively remove the influence of the serial-parallel machine tool's own positioning error on the posture calibration accuracy.

[0004] Document CN116734730A provides a calibration method and system for machine tool line laser sensors based on a standard sphere, including: scanning the entire standard sphere from different directions by a line laser fixed on a CNC machine tool to collect scanning data; converting the scanning data into three-dimensional point cloud data in the CNC machine tool coordinate system; extracting the sphere center coordinates of each point cloud corresponding to different scanning directions according to the three-dimensional point cloud data; calculating the rotation and translation RT matrix according to the scanning direction and the sphere center coordinates, and obtaining the relative position relationship of the line laser relative to the machine tool spindle, thereby completing the line laser calibration. This method is mainly for machine tools with a series structure, and is not suitable for a series-parallel structure. There is no relevant report on the calibration method directly for series-parallel machine tools. Summary of the invention

[0005] The present invention aims to solve the problem of accurate calibration of the existing serial-parallel machine tool linear laser sensor measurement posture, and invents a linear laser sensor installation posture calibration method based on the cross-section line method suitable for serial-parallel machine tools. This method does not need to change the posture of the serial-parallel mechanism, effectively avoids the influence of the serial-parallel machine tool positioning error on the measurement posture calibration, and effectively improves the calibration accuracy.

[0006] The technical solution of the present invention:

[0007] A line laser installation posture calibration method based on the cross-section line method suitable for serial-parallel machine tools is proposed. The line laser sensor is integrated into the equipment, and the kinematic chain of the measurement system is constructed according to the serial-parallel machine tool. First, the standard ball is clamped on the spindle to ensure that the center position of the standard ball remains unchanged. The geometric characteristics of the intersection of the laser surface of the line laser sensor and the standard ball are circles, and the coordinates of the center of the circle are calculated by fitting the center of the circle. Then, the equation is established to obtain the rotation matrix that characterizes the installation posture of the line laser sensor by using the characteristics of the unchanged center position. The absolute coordinates of the standard ball are obtained by analyzing the relationship between the coordinate systems on both sides of the equipment. Then, the axis of the machine tool end coordinate system is adjusted to be parallel to the axis of the base coordinate system, and the machine tool is translated to measure the standard ball and save the point cloud data. After filtering the collected point cloud data, the coordinates of the center of the ball are obtained by fitting the spherical surface, and the fitted coordinates of the center of the ball are compared with the known true value of the center of the ball, so as to obtain the deviation between the origin of the line laser sensor coordinate and the origin of the end coordinate system. During the entire calibration process, the installation posture of the linear laser sensor can be calibrated without changing the posture of the series-parallel mechanism.

[0008] The specific steps are as follows:

[0009] The first step is to establish the measurement system kinematic chain based on the serial-parallel machine tool

[0010] The serial-parallel machine tool comprises a processing side I and a supporting side II;

[0011] The processing side I is a five-axis gantry milling machine, and the XYZ directions are along the directions of its three guide rails, and the origin is the center of the circle on the upper surface of the turntable 1; the support side II is a series-parallel hybrid mechanism, which is composed of a turntable 1, a first linear axis 2, a second linear axis 3, a third linear axis 4, a three-axis parallel mechanism 5, a line laser sensor 6, a support head 7, a first moving platform 8 and a second moving platform 9, wherein the first linear axis 2 is horizontally installed in the center of the turntable 1 and is connected by a T-slot; the first moving platform 8 is a platform with an isosceles right triangle cross-section, and its right-angled surface is installed on the first linear axis 2 through a ball screw; the second linear axis 3 is installed on the inclined plane of the first moving platform 8, and the third linear axis 4 is perpendicular to the second linear axis 3, and is connected by two mutually perpendicular ball screws on the second moving platform 9; the three-axis parallel mechanism 5 is fixed on the second moving platform 9; the support head 7 is fixed to the end platform of the three-axis parallel mechanism 5; the line laser sensor 6 is installed on the side of the support head 7 of the series-parallel hybrid mechanism;

[0012] (1) Support side II base coordinate system {O B :X B ,Y B ,Z B The origin of the turntable is the center of the upper surface of the turntable 1, and the XYZ direction is consistent with the direction of the guide rail I on the processing side;

[0013] (2) Support side II end coordinate system {O E :X E ,Y E ,Z E} is a coordinate system whose origin is at the positive solution end point of the series-parallel hybrid mechanism, and when the positive solution coordinate angles A2 and B2 of the end of the support side II are zero, the axes of the end coordinate system of the support side II are parallel to the axes of the base coordinate system of the support side (II);

[0014] (3) Line laser measurement coordinate system {O S :X S ,Y S ,Z S} is the coordinate system of the line laser sensor itself, with its origin located at the center of the line laser range, the Z axis along the perpendicular direction of the laser plane, the X axis perpendicular to the Z axis in the light plane, and the Y axis follows the right-hand screw rule;

[0015] (4) Coordinate representation in each coordinate system: Point coordinates P in the line laser measurement coordinate system S , point coordinates P in the machine tool support side II end coordinate system E , point coordinates P in the base coordinate system of support side II B , the transformation relationship between the three is expressed as:

[0016]

[0017] in, For S :X S ,Y S ,Z S}→{O E :X E ,Y E ,Z E} is the homogeneous transformation matrix, For {O S :X S ,Y S ,Z S}→{O E :X E ,Y E ,Z E}, For {O S :X S ,Y S ,Z S}→{O E :X E ,Y E ,Z E}'s translation matrix; For {O E :X E ,Y E ,Z E}→{O B :X B ,Y B ,Z B} is the homogeneous transformation matrix, For {O E :X E ,Y E ,Z E}→{O B :X B ,Y B ,Z B}, For {O E :X E ,Y E ,Z E}→{O B :X B ,Y B ,Z B}'s translation matrix;

[0018] The second step is to obtain the rotation matrix that represents the installation posture of the line laser.

[0019] First, clamp the standard ball to the spindle on the processing side I and obtain the coordinates of the center of the standard ball in the online laser measurement coordinate system. The intersection of the laser surface of the line laser sensor at any angle and the standard ball is a circle, and the center of the intersection circle is O. ′ The line connecting the center O of the standard sphere, the radius r of the intersection circle and the radius R of the standard sphere form a right triangle. Using this characteristic, first obtain the coordinates of the center of the intersection circle in the line laser measurement coordinate system; then obtain the coordinates of the center of the standard sphere in the line laser measurement coordinate system; assume that the laser surface of the line laser sensor intersects with the standard sphere to form an arc, and the coordinates of the points on the arc are the readings of the line laser sensor. Use the least squares method to fit the coordinates of the points on the arc into a circle, and the equation of the obtained circle is expressed as:

[0020] (x) 2 +(zb) 2 =r 2 (2)

[0021] Among them, a and b correspond to the X and B of the online laser measurement coordinate system of the center of the fitting circle, respectively. S Axis and Z S The coordinates of the axes;

[0022] From the geometric characteristics of the sphere, we can see that the straight line OO ′ Perpendicular to the laser plane of the line laser sensor, the absolute value of the coordinates of the center of the standard ball in the line laser measurement coordinate system is |OO ′ |, pay attention to the positive and negative signs in the solution process; then the sphere center coordinate formula is shown in formula (3):

[0023]

[0024] Ensure that the center position of the standard ball remains unchanged, and obtain the following through multiple measurements:

[0025]

[0026] The homogeneous transformation matrix in the above formula is expressed in the form of rotation matrix and translation matrix, then formula (4) is expressed as:

[0027]

[0028] The axis of the line laser measurement coordinate system is installed as parallel as possible to the axis of the support side (II) end coordinate system. The support side serial-parallel hybrid mechanism is controlled to clamp the line laser to perform only translational motion to complete multiple measurements of the standard ball. During the measurement process, the rotation matrix from the support side II end coordinate system to the support side II base coordinate system is is a fixed value, expressed as:

[0029]

[0030] Substituting formula (6) into formula (5) and simplifying it, we get the following formula:

[0031]

[0032] Rotation Matrix There are 9 parameters in total, which are used to solve the unknown quantities. The rotation matrix is ​​solved by multiple measurements using the conditional optimization method. The optimization model established to solve the optimal solution of the rotation matrix is ​​expressed as:

[0033]

[0034] Where n is the number of measurements when solving the rotation matrix, n>4, for The transpose of , I is the unit matrix, det is the rank of the matrix;

[0035] The third step is to obtain the true coordinates of the center of the ball in the support side II base coordinate system

[0036] Use the tool setting instrument to obtain the tool length L 1 , clamp the standard ball to the spindle of the processing side I, make the micrometer probe contact with the standard ball, make the line connecting the contact point and the ball center parallel to the Y axis of the serial-parallel machine tool as much as possible, then rotate the spindle to obtain the circular runout δ between the outer surface of the standard ball and the spindle axis, stop the standard ball at the position where the micrometer reading is the smallest; move the spindle so that the standard ball is within the online laser measurement range, and read the processing side I coordinate [X 1 Y 1 Z 1 ] ′ At this time, the deviation between the center of the standard ball and the main axis in the Y direction is δ / 2. Considering the radius R of the standard ball, the coordinates of the center of the ball are calculated as P B ;

[0037]

[0038] The fourth step is to translate the machine tool to measure the surface of the standard sphere and fit the center of the sphere, compare it with the true value of the center of the sphere, and obtain the deviation between the origin of the line laser measurement coordinate system and the origin of the support side II end coordinate system.

[0039] Adjust the angles of A2 and B2 of the end coordinates of support side II to zero degrees, then translate the serial-parallel machine tool and measure the standard ball. default is 0, the point cloud data representing the spherical surface of the standard sphere is converted from the line laser measurement coordinate system to the support side II end coordinate system, the point cloud data of the standard sphere surface is obtained and filtered, the point cloud data is fitted into a sphere using the least squares method or RANSAC algorithm, the coordinates of the sphere center in the support side II base coordinate system and the fitting error are obtained, and the fitting result with the smaller error is taken as the sphere center coordinates:

[0040]

[0041] Compare with the true value of the spherical center coordinates and make a difference to obtain the deviation between the origin of the line laser measurement coordinate system and the coordinate system of the end of the support side II:

[0042]

[0043] Thus, the rotation matrix and translation matrix characterizing the installation posture of the line laser are obtained.

[0044] Beneficial effects of the present invention: This method aims at the problem that a series-parallel machine tool is prone to large positioning errors when changing its posture. The proposed method can obtain the rotation and translation matrices representing the installation posture of the line laser without changing the posture of the machine tool. The rotation matrix representing the installation posture of the line laser is established by using the characteristic that the center of the standard ball remains unchanged in the machine tool coordinate system. After solving the absolute coordinates of the center of the standard ball, the machine tool support side is controlled to move to measure the surface of the standard ball to obtain the point cloud data of its surface and filter it. After that, a fitting algorithm is used to obtain the fitting center of the point cloud data. By comparing with the true value of the center coordinates, the translation matrix representing the installation position of the line laser is obtained to complete the calibration of the line laser. The operation is simple and convenient with high accuracy, and it has strong practicality and operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the process of the present invention.

[0046] Figure 2 It is a schematic diagram of the series-parallel machine tool in the present invention.

[0047] Figure 3 It is a schematic diagram of obtaining the coordinates of the center of a standard ball in an online laser measurement coordinate system in the present invention.

[0048] Figure 4 Schematic diagram of the kinematic chain of the machine tool support side mechanism and the measurement system in the present invention.

[0049] Figure 5 This is a partial enlarged view of the measurement system's kinematic chain.

[0050] Figure 6 It is a schematic diagram of the positional relationship between the standard ball and the machining side and support side mechanisms of the machine tool and the line laser sensor in the present invention.

[0051] In the figure: I processing side; II supporting side; 1 turntable; 2 first linear axis; 3 second linear axis; 4 third linear axis; 5 three-axis parallel mechanism; 6 line laser sensor; 7 supporting head; 8 first moving platform; 9 second moving platform. DETAILED DESCRIPTION

[0052] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0053] The first step is to install the line laser sensor and the standard ball. Figure 6 As shown, the standard ball 8 is installed on the processing side spindle through a collet, the line laser sensor 6 is a Keyence LJ-X8080 line laser, and the standard ball 8 is a Zeiss ceramic standard ball with a diameter of 29.9869 mm and a roundness of 0.047 μm.

[0054] The second step is to obtain the rotation matrix that characterizes the installation posture of the line laser sensor. Install the axis of the line laser measurement coordinate system as parallel as possible to the axis of the end coordinate system of the support side (II), and then control the machine tool to translate along XYZ to measure the standard ball multiple times. Each measurement records the line laser raw data LaserData and the machine tool coordinate data CNCData as well as the positive and negative Y of the ball center in the line laser measurement coordinate system. The data obtained in the experiment are as follows:

[0055] Table 1 Rotation matrix calibration experimental data (mm)

[0056]

[0057] Formula (2) is used to fit the coordinates of the center of the circle obtained by the intersection of the laser surface of the outgoing laser sensor and the standard sphere in the online laser measurement coordinate system, and then formula (3) is used to obtain the coordinates of the center of the standard sphere in the online laser measurement coordinate system. E :X E ,Y E ,Z E}→{O B :X B ,Y B ,Z B The rotation matrix of {O E :X E ,Y E ,Z E}→{O B :X B ,Y B ,Z B}'s translation matrix Since the end posture of the support side does not change, Formula (8) is used to establish the rotation matrix solution equation that characterizes the installation posture of the line laser sensor.

[0058] The rotation matrix can be obtained from the data in Table 1

[0059] The third step is to measure the surface of the standard sphere and fit the center of the standard sphere, compare it with the true value of the center, and obtain the deviation between the origin of the line laser measurement coordinate system and the end coordinate system of the support side (II). Adjust the end coordinate angles A2 and B2 of the support side to zero degrees. At this time, the axis of the end coordinate system of the support side (II) coincides with the axis of the base coordinate system of the support side (II). Then move along the axis perpendicular to the laser surface of the line laser sensor, measure the standard sphere every unit time, and save the line laser data and machine tool data. The saved data is shown in the following table:

[0060] Table 2 Part of the ball center fitting experimental data (mm)

[0061]

[0062]

[0063] Using the above steps to obtain default 0, transform the point cloud data representing the spherical surface of the standard sphere from the line laser measurement coordinate system to the support side (II) base coordinate system, obtain the point cloud data of the surface of the standard sphere and perform filtering processing on it, use the least squares method or RANSAC algorithm to fit the point cloud data into a sphere, obtain its sphere center coordinates and fitting error, take the fitting result with smaller error as the sphere center coordinates, and use the experimental data in Table 2 to get the fitting sphere center coordinates: Read the machine tool processing side coordinates The tool length of the standard ball obtained by the tool setting instrument is 168.3869 mm, the circular runout δ is 0.05 mm, and the true value coordinates of the ball center obtained by formula (9) are: From formula (11), we can get the translation matrix:

[0064] In this way, the rotation matrix and translation matrix that characterize the installation posture of the line laser sensor are obtained.

[0065] The fourth step is to verify the calibration results. The surface of the standard sphere is measured multiple times, and the coordinates of the center of the standard sphere in the online laser measurement coordinate system are obtained using the sphere center calculation formula. The obtained data are shown in Table 3.

[0066] Table 3 Partial calibration accuracy test experimental data (mm)

[0067]

[0068] 18 sets of data were measured at different positions. The calculated rotation matrix and translation matrix were used to transform the sphere center coordinates in the line laser measurement coordinate system into the support side (II) base coordinate system and to make a difference with the true value of the sphere center coordinates to verify the calibration accuracy.

[0069] The traditional hand-eye calibration method is used to compare with this method. The traditional hand-eye calibration method does not need to obtain the true coordinates of the center of the ball. It only needs to ensure that the coordinates of the center of the ball remain unchanged in the base coordinate system of the support side (II). During the calibration process, the posture of the series-parallel mechanism needs to be frequently changed, and the line laser data and the corresponding machine tool data are obtained at the same time. Based on the fact that the center of the standard ball remains unchanged in the base coordinate system of the support side (II), an equation is established to obtain the rotation and translation matrix that characterizes the installation posture of the line laser sensor. Experimental results show that After obtaining the rotation and translation matrices, several sets of line laser data and corresponding machine tool data are taken in different postures, and the coordinates of the sphere center in the online laser measurement coordinate system are obtained and converted to the support side (II) base coordinate system, and then the average is obtained, which is used as a reference to verify the calibration results. The calibration errors of the method M1 of the present invention and the traditional method M2 in the three directions of XYZ are obtained as follows:

[0070] Table 4 Calibration accuracy test analysis (mm)

[0071]

[0072] By comparison, the proposed method has greatly improved the accuracy compared with the traditional calibration method which requires frequent changes in the posture of the series-parallel mechanism.

[0073] The above is only a specific embodiment of the present invention. The above embodiment is only for describing the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A line laser installation posture calibration method based on the cross-section line method suitable for serial-parallel machine tools, characterized in that: Here are the steps: The first step is to establish the measurement system kinematic chain based on the serial-parallel machine tool The serial-parallel machine tool comprises a processing side (I) and a supporting side (II); The processing side (I) is a five-axis gantry milling machine, the XYZ directions are along the directions of its three guide rails, and the origin is the center of the circle on the upper surface of the turntable (1); the support side (II) is a series-parallel hybrid mechanism, which is composed of a turntable (1), a first linear axis (2), a second linear axis (3), a third linear axis (4), a three-axis parallel mechanism (5), a line laser sensor (6), a support head (7), a first moving platform (8) and a second moving platform (9), wherein the first linear axis (2) is horizontally installed at the center of the turntable (1) and connected via a T-slot; the first moving platform (8) The platform has a cross section of an isosceles right triangle, a right-angled surface of which is mounted on a first linear axis (2) via a ball screw; a second linear axis (3) is mounted on an inclined plane of a first moving platform (8); a third linear axis (4) and the second linear axis (3) are perpendicular to each other and are connected via two mutually perpendicular ball screws on a second moving platform (9); a three-axis parallel mechanism (5) is fixed on the second moving platform (9); a support head (7) is fixed on the end platform of the three-axis parallel mechanism (5); and a line laser sensor (6) is mounted on the side of the support head (7) of the series-parallel hybrid mechanism; (1) Support side (II) Base coordinate system {O B :X B ,Y B ,Z B The origin of the turntable (1) is the center of the upper surface of the turntable, and the XYZ directions are consistent with the directions of the guide rails on the processing side (I); (2) Support side (II) end coordinate system {O E :X E ,Y E ,Z E } is a coordinate system whose origin is at the end point of the positive solution of the series-parallel hybrid mechanism, and when the positive solution coordinate angles A2 and B2 of the end of the support side (II) are zero, the axes of the end coordinate system of the support side (II) are parallel to the axes of the base coordinate system of the support side (II); (3) Line laser measurement coordinate system {O S :X S ,Y S ,Z S } is the coordinate system of the line laser sensor itself, with its origin located at the center of the line laser range, the Z axis along the perpendicular direction of the laser plane, the X axis perpendicular to the Z axis in the light plane, and the Y axis follows the right-hand screw rule; (4) Coordinate representation in each coordinate system: Point coordinates P in the line laser measurement coordinate system S , point coordinates P in the end coordinate system of the machine tool support side (II) E , point coordinates P in the base coordinate system of the support side (II) B , the transformation relationship between the three is expressed as: in, For {O S :X S ,Y S ,Z S }→{O E :X E ,Y E ,Z E } is the homogeneous transformation matrix, For {O S :X S ,Y S ,Z S }→{O E :X E ,Y E ,Z E }, For {O S :X S ,Y S ,Z S }→{O E :X E ,Y E ,Z E }'s translation matrix; For {O E :X E ,Y E ,Z E }→{O B :X B ,Y B ,Z B } is the homogeneous transformation matrix, For {O E :X E ,Y E ,Z E }→{O B :X B ,Y B ,Z B }, For {O E :X E ,Y E ,Z E }→{O B :X B ,Y B ,Z B }'s translation matrix; The second step is to obtain the rotation matrix that represents the installation posture of the line laser. First, clamp the standard ball to the spindle on the processing side (I) and obtain the coordinates of the center of the standard ball in the online laser measurement coordinate system. The intersection of the laser surface of the line laser sensor at any angle and the standard ball is a circle, and the center of the intersection circle is O. ′ The line connecting the center O of the standard sphere, the radius r of the intersection circle and the radius R of the standard sphere form a right triangle. Using this characteristic, first obtain the coordinates of the center of the intersection circle in the line laser measurement coordinate system; then obtain the coordinates of the center of the standard sphere in the line laser measurement coordinate system; assume that the laser surface of the line laser sensor intersects with the standard sphere to form an arc, and the coordinates of the points on the arc are the readings of the line laser sensor. Use the least squares method to fit the coordinates of the points on the arc into a circle, and the equation of the obtained circle is expressed as: (x) 2 +(zb) 2 =r 2 (2) where a and b correspond to the X coordinates of the online laser measurement coordinate system of the center of the fitting circle, S Axis and Z S The coordinates of the axes; From the geometric characteristics of the sphere, we can see that the straight line OO ′ Perpendicular to the laser plane of the line laser sensor, the absolute value of the coordinates of the center of the standard ball in the line laser measurement coordinate system is |OO ′ |, pay attention to the positive and negative signs in the solution process; then the sphere center coordinate formula is shown in formula (3): Ensure that the center position of the standard ball remains unchanged, and obtain the following through multiple measurements: The homogeneous transformation matrix in the above formula is expressed in the form of rotation matrix and translation matrix, then formula (4) is expressed as: The axis of the line laser measurement coordinate system is installed as parallel as possible to the axis of the support side (II) end coordinate system. The support side serial-parallel hybrid mechanism is controlled to clamp the line laser to perform only translational motion to complete multiple measurements of the standard ball. During the measurement process, the rotation matrix from the support side (II) end coordinate system to the support side (II) base coordinate system is is a fixed value, expressed as: Substituting formula (6) into formula (5) and simplifying it, we get the following formula: Rotation Matrix There are 9 parameters in total, which are used to solve the unknown quantities. The rotation matrix is ​​solved by multiple measurements using the conditional optimization method. The optimization model established to solve the optimal solution of the rotation matrix is ​​expressed as: Where n is the number of measurements when solving the rotation matrix, n>4, for The transpose of , I is the unit matrix, det is the rank of the matrix; The third step is to obtain the true coordinates of the center of the ball in the base coordinate system of the support side (II). Use the tool setting instrument to obtain the tool length L1, clamp the standard ball to the spindle on the processing side (I), make the micrometer probe contact the standard ball, and make the line connecting the contact point and the ball center parallel to the Y axis of the serial-parallel machine tool as much as possible. Then rotate the spindle to obtain the circular runout δ between the outer surface of the standard ball and the spindle axis, and stop the standard ball at the position with the smallest micrometer reading; move the spindle so that the standard ball is within the online laser measurement range, and read the processing side (I) coordinates [X1 Y1 Z1] at this time ′ At this time, the deviation between the center of the standard ball and the main axis in the Y direction is δ / 2. Considering the radius R of the standard ball, the coordinates of the center of the ball are calculated as P B ; The fourth step is to translate the machine tool to measure the surface of the standard sphere and fit the sphere center, compare it with the true value of the sphere center, and obtain the deviation between the origin of the line laser measurement coordinate system and the origin of the support side (II) end coordinate system. Adjust the angles of the end coordinates A2 and B2 of the support side (II) to zero, then translate the serial-parallel machine tool and measure the standard ball. default is 0, the point cloud data representing the spherical surface of the standard sphere is converted from the line laser measurement coordinate system to the support side (II) end coordinate system, the point cloud data of the standard sphere surface is obtained and filtered, the point cloud data is fitted into a sphere using the least squares method or RANSAC algorithm, the coordinates of the sphere center in the support side (II) base coordinate system are obtained, and the fitting error is obtained, and the fitting result with the smaller error is taken as the coordinates of the sphere center: Compare with the true value of the spherical center coordinates and make a difference to obtain the deviation between the origin of the line laser measurement coordinate system and the end coordinate system of the support side (II): Thus, the rotation matrix and translation matrix characterizing the installation posture of the line laser are obtained.

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