Calibration method and system for magneto-rheological polishing machine tool with underneath fixed polishing wheel

Abstract

The invention discloses a calibration method and system for a magneto-rheological polishing machine tool with an underneath fixed polishing wheel, relates to the technical field of machine tool structure parameter measurement, provides an automatic calibration process for the structure of the magneto-rheological polishing machine tool with the underneath fixed polishing wheel, and solves the problem of multi-parameter coupling calibration of the magneto-rheological polishing machine tool with the underneath fixed polishing wheel. A contact type measuring head and non-contact type laser measurement are fused, and the measurement efficiency and precision are both considered; and high-precision inverse solution of parameters is realized through analysis of a spherical surface fitting algorithm and a spatial geometrical relationship.

Description

Technical Field

[0001] This invention relates to the field of machine tool structural parameter measurement technology, specifically to a calibration method and system for a magnetorheological polishing machine tool with a fixed lower polishing wheel. Background Technology

[0002] Complex curved surface optical elements are increasingly widely used in high-precision optical systems such as astronomical telescopes, optical microscopes, and photolithography machines. With the rapid development of various optical systems, the requirements for the surface quality of optical elements are constantly increasing, especially for the processing accuracy and efficiency of complex curved surface optical elements (such as photolithography objectives). Magnetorheological polishing is an advanced optical processing technology with advantages such as high processing accuracy, good surface quality, high processing efficiency, and no pressure-induced surface damage. It utilizes the rheological effect of magnetorheological fluids under the action of a magnetic field to achieve high-precision polishing and shaping of workpiece surfaces. It is widely used in the field of optical element manufacturing and has become one of the key processes in optical element manufacturing. However, the core prerequisite for the deterministic removal of material from the workpiece surface using magnetorheological polishing technology is that the polishing point and the point to be processed on the workpiece surface must always maintain constant normal contact during the polishing process. Therefore, it places extremely high demands on the movement trajectory and posture control of the polishing wheel or workpiece.

[0003] Currently, most magnetorheological polishing machines in China adopt a top-mounted, moving polishing wheel structure. However, related research indicates that this structure faces two major challenges when machining highly steep and complex curved optical components: limited ability to shape highly steep workpieces and difficulty in ensuring the stability of the polishing wheel ribbon during machine movement. A bottom-mounted, fixed polishing wheel structure offers higher rigidity and ribbon stability, and combined with virtual axis technology, is particularly suitable for high-precision machining of highly steep and complex curved surfaces. However, this structure faces unique challenges in machine calibration.

[0004] The actual installation position of the workpiece needs to be measured by the workpiece probe and accurately converted to the highest point of the polishing wheel (polishing point). Therefore, the relative positional relationship between the workpiece probe and the highest point of the polishing wheel needs to be precisely calibrated. When the workpiece is clamped on the worktable and polishing complex curved surfaces, the B-axis needs to be linked. However, due to errors in machine tool design, manufacturing, and equipment processes, the positional relationship between the B-axis and the center of the worktable also needs to be accurately calibrated. Existing calibration methods for magnetorheological polishing machines mostly rely on manual measurement using a dial indicator. This method has the following obvious drawbacks:

[0005] The automation level is low, relying on operator experience; the calibration efficiency is low, with a single calibration taking up to 12 hours; the accuracy is greatly affected by human factors, making it difficult to guarantee micron-level accuracy and repeatability; it cannot be used for relative position calibration on machine tools with a fixed polishing wheel at the bottom, limiting the application of this structure in high-precision machining; and existing magnetorheological machine tool calibration methods are not applicable to structures with a fixed polishing wheel at the bottom. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a calibration method and system for a magnetorheological polishing machine tool with a fixed polishing wheel at the bottom. This method provides an automated calibration process for the structure of the machine tool, solving the challenge of multi-parameter coupling calibration. It integrates contact probes and non-contact laser measurement, balancing measurement efficiency and accuracy. Furthermore, it achieves high-precision inverse solution of parameters through a spherical fitting algorithm and spatial geometric relationship analysis.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0008] This solution provides a calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel. The method includes:

[0009] Install the first standard ball on the machine tool worktable, set the swing axis B to zero, adjust the rotating axis C to make the rotating axis C concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C is concentric with the first standard ball;

[0010] Move the machine tool to position A, adjust the swing axis B, fit the positional relationship between the swing axis B and the center of the first standard ball, and solve for the structural parameters of the swing axis B; and determine the position B of the machine tool when the workpiece probe and the rotating axis C are concentric.

[0011] Install a second standard ball at the workpiece probe position, set the swing axis B to zero, adjust the rotating axis C to make the rotating axis C concentric with the second standard ball, and determine the position C of the machine tool when the rotating axis C is concentric with the second standard ball.

[0012] The relative positional relationship between the workpiece probe and the second standard ball is determined by combining positions B and C;

[0013] The coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel are determined based on the laser displacement sensor on the machine tool worktable. The relative positional relationship between the second standard sphere and the highest point of the polishing wheel is determined by combining the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel.

[0014] Based on the relative positional relationship between the workpiece probe and the second standard ball, and the relative positional relationship between the second standard ball and the highest point of the polishing wheel, the relative positional relationship between the workpiece probe and the highest point of the polishing wheel is determined.

[0015] A further optimized solution is that the method for determining location A includes:

[0016] S1, the workpiece probe measures the point cloud data of multiple points on the surface of the first standard sphere. Based on the point cloud data and the radius R of the first standard sphere, the coordinates of the center of the first standard sphere (X0, Y0, Z0) are fitted using the least squares method. sphere1 Ysphere1 Z sphere1 ), and based on the sphere center coordinates (X0, Y0, Z0), obtain the machine tool position (X1, Y1) = (X0, Y0) when the C-axis of the rotating shaft is concentric with the first standard sphere;

[0017] S2, the machine tool moves to the position (X1, Y1) where the B-axis of the swing axis is zeroed, and the Z-axis coordinate value of the lowest point of the first standard ball is measured. sphere0 Adjust the C-axis to any angle θ, and measure the Z-axis coordinate value Z of the lowest point of the first standard sphere at this time. sphereθ ;

[0018] S3, calculate Z sphere0 With Z sphereθ The difference between them, with a preset difference threshold, when Z sphere0 With Z sphereθ If the difference between the two values ​​is less than the difference threshold, output the current machine tool position (X1, Y1) = (X0, Y0) as position A; otherwise, return to step S1.

[0019] A further optimization scheme involves fitting the positional relationship between the pendulum axis B and the center of the first standard sphere, and solving for the structural parameters of the pendulum axis B; including the following methods:

[0020] Adjust the pendulum axis B to an angle of ±θ i Fit the B-axis of the pendulum axis at angle ±θ i The center of the first standard ball According to the first standard ball at the angle ±θ from the B-axis of the pendulum. i The following spatial geometric positional relationships are:

[0021] ;

[0022] ;

[0023] ;

[0024] Where a represents the eccentricity of the swing axis B; b represents the vertical distance between the swing axis B and the machine tool table in the Z-axis direction; and h represents the vertical distance between the center of the first standard ball and the end face of the machine tool table in the Z-axis direction. and This represents the change in position of the center of the first standard sphere in the xoz plane at any angle θ between the center of the first standard sphere and the B-axis of the pendulum when the B-axis is set to zero.

[0025] Solve for the structural parameters a and b of the pendulum axis B.

[0026] A further optimized solution involves determining the position B of the machine tool when the workpiece probe is concentric with the C-axis, including:

[0027] Remove the first standard ball and set the B-axis of the swing axis to zero. Measure the Z-axis coordinate value Z of the machine tool table end face based on the workpiece probe. workbench By combining the coordinates (X0, Y0, Z0) of the center of the first standard sphere, the position B (X1, Y1, Z1) of the machine tool when the workpiece probe is concentric with the C-axis is obtained:

[0028] ;

[0029] .

[0030] A further optimization scheme involves determining the position C of the machine tool when the rotating shaft C-axis is concentric with the second standard sphere, including:

[0031] T1. Install a dial indicator on the machine tool table and a second standard ball at the workpiece probe position. Rotate the machine tool table to measure the extreme points around the second standard ball based on the dial indicator: the leftmost point X. left The rightmost point X right The foremost point Y front and the last side point Y back ;

[0032] T2, based on the extreme points around the second standard sphere, combined with the geometric symmetry relationship, the position C coordinate (X2, Y2) of the machine is obtained when the rotation axis C is concentric with the second standard sphere;

[0033] T3, move the machine tool to coordinate (X2, Y2), continuously rotate the C-axis, measure the fluctuation value of the second standard ball based on the dial indicator, preset the fluctuation threshold, when the fluctuation value is less than the fluctuation threshold, take the current machine tool position (X2, Y2) as position C, and determine the Z-axis coordinate Z2 when the end face of the worktable coincides with the highest point of the second standard ball; otherwise, return to step T1.

[0034] A further optimized solution is to calculate the Z-axis coordinate Z2 when the end face of the worktable coincides with the highest point of the second standard sphere using the following formula:

[0035] ;

[0036] Among them, Z gauge Represents the Z-axis coordinate value of the machine tool; L gauge This indicates the closest distance between the end face of the worktable and the second standard ball.

[0037] A further optimized solution involves using a laser displacement sensor on the machine tool worktable to determine the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel; including the following method:

[0038] The center coordinates (X and Y) of the second standard sphere are obtained based on the laser displacement sensor on the machine tool table. sphere2 Ysphere2 Z sphere2 Using the radius R of the second standard sphere, coordinate transformation is performed to obtain the coordinates (X3, Y3, Z3) of the highest point of the second standard sphere as measured by the laser displacement sensor:

[0039] ;

[0040] The coordinates (X, X) of the polishing wheel's center are obtained using a laser displacement sensor on the machine tool's worktable. wheel Y wheel Z wheel and the radius R of the polishing wheel wheel The coordinates of the highest point of the lower polishing wheel measured by the laser displacement sensor are (X4, Y4, Z4):

[0041] .

[0042] A further optimized scheme is that the relative positional relationship between the workpiece probe and the second standard ball is determined according to the following formula:

[0043] ;

[0044] Where (X1, Y1, Z1) represents the position B coordinate of the machine tool when the workpiece probe is concentric with the C-axis; (X2, Y2, Z2) represents the position C coordinate of the machine tool when the C-axis is concentric with the second standard ball; (dX1, dY1, dZ1) represents the relative positional relationship between the workpiece probe and the second standard ball.

[0045] The relative positional relationship between the second standard ball and the highest point of the polishing wheel is determined by the following formula:

[0046] ;

[0047] Where (X4, Y4, Z4) represents the position B coordinate of the machine tool when the workpiece probe is concentric with the C-axis; (X3, Y3, Z3) represents the position C coordinate of the machine tool when the C-axis is concentric with the second standard ball; (dX2, dY2, dZ2) represents the relative position relationship between the second standard ball and the highest point of the polishing wheel.

[0048] A further optimized approach involves determining the relative positional relationship between the workpiece probe and the highest point of the polishing wheel, including:

[0049] ;

[0050] Where (dX, dY, dZ) represents the relative positional relationship between the workpiece probe and the highest point of the polishing wheel.

[0051] This solution also provides a calibration system for a magnetorheological polishing machine tool with a fixed lower polishing wheel, used to implement the above-mentioned calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel. The system includes:

[0052] The first calculation module is used to install the first standard ball on the machine tool worktable, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C axis is concentric with the first standard ball;

[0053] The second calculation module is used to move the machine tool to position A, adjust the swing axis B, fit the positional relationship between the swing axis B and the center of the first standard ball, and solve for the structural parameters of the swing axis B; and determine the position B of the machine tool when the workpiece probe and the rotating axis C are concentric.

[0054] The third calculation module is used to install the second standard ball at the workpiece probe position, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the second standard ball, and determine the position C of the machine tool when the rotating axis C axis is concentric with the second standard ball;

[0055] The fourth calculation module is used to determine the relative positional relationship between the workpiece probe and the second standard ball by combining position B and position C;

[0056] The fifth calculation module is used to determine the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel based on the laser displacement sensor on the machine tool workbench, and to determine the relative positional relationship between the second standard sphere and the highest point of the polishing wheel by combining the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel.

[0057] The sixth calculation module is used to determine the relative positional relationship between the workpiece probe and the highest point of the polishing wheel based on the relative positional relationship between the workpiece probe and the second standard ball, and the relative positional relationship between the second standard ball and the highest point of the polishing wheel.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1. This solution provides a calibration method and system for a magnetorheological polishing machine tool with a fixed polishing wheel at the bottom. It offers an automated calibration process tailored to the structure of this type of machine, solving the challenge of multi-parameter coupling calibration. It integrates contact probes and non-contact laser measurement, balancing measurement efficiency and accuracy. High-precision inverse solution of parameters is achieved through a spherical fitting algorithm and spatial geometric relationship analysis.

[0060] 2. This solution provides a calibration method and system for a fixed-bottom-mounted magnetorheological polishing machine. By combining multi-axis linkage control with CNC code and a spherical fitting algorithm, it achieves high-precision, automated calibration of the relative position between the workpiece probe and the highest point of the polishing wheel, as well as the structural parameters of the B-axis of the swing axis, in the fixed-bottom-mounted magnetorheological polishing machine. This reduces manual intervention and significantly shortens the calibration time compared to traditional manual calibration. Based on a dual-reference design, only local recalibration is required after changing the probe or polishing wheel, greatly improving calibration efficiency. Attached Figure Description

[0061] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0062] Figure 1 A schematic diagram of the calibration method for a magnetorheological polishing machine tool with a fixed polishing wheel at the bottom;

[0063] Figure 2 A schematic diagram illustrating the calibration principle of a magnetorheological polishing machine tool with a fixed lower polishing wheel.

[0064] Figure 3 A schematic diagram of the calibration method for the B-axis parameters of a fixed-bottom magnetorheological polishing machine with a polishing wheel;

[0065] Figure 4 Schematic diagram A of a fixed-position magnetorheological polishing machine with a polishing wheel at the bottom;

[0066] Figure 5 Schematic diagram B of a fixed-position magnetorheological polishing machine with a polishing wheel at the bottom;

[0067] Figure 6 Schematic diagram C of a fixed magnetorheological polishing machine tool with a polishing wheel at the bottom.

[0068] The attached diagram shows the markings and corresponding component names:

[0069] 1-Workpiece probe, 2-Second standard ball, 3-Swing axis B-axis, 4-Rotation axis C-axis, 5-First standard ball, 6-Polishing wheel,

[0070] 7 - Dial gauge, 8 - Laser displacement sensor. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0072] Compared to the widely adopted upper-mounted, moving polishing wheel structure, the lower-mounted, fixed polishing wheel configuration exhibits superior processing capabilities and ribbon stability in the high-precision shaping of complex curved optical elements. However, this structure also presents unique calibration challenges: the relative positional relationship between the workpiece probe and the highest point of the polishing wheel, as well as the structural parameters of the B-axis of the balance shaft, must be accurately calibrated. Traditional calibration methods rely on manual measurement with a dial indicator, which has significant limitations: on the one hand, calibration efficiency is low and accuracy is significantly affected by the operator's experience; on the other hand, due to the limitations of the dial indicator's working principle, traditional methods cannot achieve accurate calibration of the relative position between the workpiece probe and the highest point of the polishing wheel. Therefore, this solution provides the following embodiments to address the aforementioned technical problems:

[0073] Example 1

[0074] This embodiment provides a calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel. The following is a description of such a method. Figures 4-6 The diagram illustrates a portion of the structure of a magnetorheological polishing machine with a fixed lower polishing wheel. The machine's worktable is connected to the swing axis B, and the center of the worktable is the adjustment axis C. The workpiece probe 1, the second standard ball 2, and the laser displacement sensor 8 have relatively fixed positional relationships. The method is as follows: Figure 1 and Figure 2 As shown, it specifically includes:

[0075] Step 1: Install the first standard ball 5 on the machine tool worktable, set the swing axis B axis 3 to zero, adjust the rotating axis C axis 4 so that the rotating axis C axis is concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C axis 4 is concentric with the first standard ball 5;

[0076] The methods for determining location A include:

[0077] S1, the workpiece probe 1 measures the point cloud data of multiple points on the surface of the first standard sphere. Based on the point cloud data and the radius R of the first standard sphere 5, the coordinates of the center of the first standard sphere (X0, Y0, Z0) are fitted using the least squares method. sphere1 Y sphere1 Z sphere1 ), and based on the sphere center coordinates (X0, Y0, Z0), the machine tool position (X1, Y1) = (X0, Y0) when the rotating shaft C axis 4 is concentric with the first standard sphere 5;

[0078] Specifically, the n point cloud data of the surface of the first standard sphere 5 are represented as follows: , Represent the spatial coordinates of the i-th point; fit the first standard sphere as:

[0079] ;

[0080] S2, the machine tool moves to the position (X1, Y1) where the swing axis B axis 3 is zeroed, and the Z-axis coordinate value of the lowest point of the first standard ball 5 is measured. sphere0 Adjust the C-axis rotation to any angle θ, and measure the Z-axis coordinate value Z of the lowest point of the first standard sphere at this time. sphereθ ;

[0081] S3, calculate Z sphere0 With Z sphereθ The difference between them, with a preset difference threshold, when Z sphere0 With Z sphereθ If the difference between the values ​​is less than the difference threshold, output the current machine tool position (X1, Y1) = (X0, Y0) as position A; otherwise, return to step S1. Specifically, ensure that the concentricity error between the C-axis and the first standard ball 5 is <5µm.

[0082] Step 2: Move the machine tool to position A, adjust the swing axis B axis 3, fit the positional relationship between the swing axis B axis 3 and the center of the first standard ball 5, and solve for the structural parameters of the swing axis B axis 3; and determine the position B of the machine tool when the workpiece probe 1 and the rotating axis C axis 4 are concentric.

[0083] The method involves fitting the positional relationship between the pendulum axis B-axis 3 and the center of the first standard sphere 5, and solving for the structural parameters of the pendulum axis B-axis 3; including the following methods:

[0084] like Figure 3 As shown, adjust the pendulum axis B-axis 3 to an angle ±θ. i Fit the pendulum axis B-axis 3 at angle ±θ i The center of the first standard ball According to the first standard ball 5, at the angle ±θ from the pendulum axis B axis 3. i The following spatial geometric positional relationships are:

[0085] ;

[0086] ;

[0087] ;

[0088] Where a represents the eccentricity of the swing axis B axis 3; b represents the vertical distance between the swing axis B axis 3 and the machine tool table in the Z-axis direction; h represents the vertical distance between the center of the first standard ball 5 and the end face of the machine tool table in the Z-axis direction. and This represents the change in position of the center of the first standard sphere in the xoz plane at any angle θ between the center of the first standard sphere and the B-axis of the pendulum when the B-axis is set to zero.

[0089] Solve for the structural parameters a and b of the pendulum axis B axis 3.

[0090] Since the position of the workpiece probe is fixed, according to Figure 3 The B-axis is shown with different θ values. i The center of the standard sphere 1 at 0° and the center of the sphere at 0° have the above spatial positional relationship. The structural parameters a and b of the pendulum axis B are obtained by inverse solution.

[0091] The methods for determining the position B of the machine tool when the workpiece probe 1 is concentric with the rotating axis C-axis 4 include:

[0092] Remove the first standard ball 5 and set the swing axis B axis 3 to zero. Measure the Z-axis coordinate value Z of the machine tool table end face based on the workpiece probe 1. workbench By combining the center coordinates (X0, Y0, Z0) of the first standard sphere 5, the position B (X1, Y1, Z1) of the machine tool when the workpiece probe 1 is concentric with the rotating axis C-axis 4 is obtained:

[0093]

[0094] .

[0095] The method for determining the position C of the machine tool when the rotating shaft C4 is concentric with the second standard ball 2 includes:

[0096] T1. Install a dial indicator 7 on the machine tool worktable and a second standard ball 2 at the workpiece probe position. Rotate the machine tool worktable to measure the extreme points around the second standard ball based on the dial indicator: the leftmost point X. left The rightmost point X right The foremost point Y front and the last side point Y back Ensure the dial indicator reading remains the same during each press, such as 20µm.

[0097] T2, based on the extreme points around the second standard sphere, combined with the geometric symmetry relationship, the position C coordinate (X2, Y2) of the machine is obtained when the rotation axis C is concentric with the second standard sphere;

[0098] T3, move the machine tool to coordinate (X2, Y2), continuously rotate the C-axis, and measure the fluctuation value of the second standard ball using a dial indicator. A preset fluctuation threshold is set. When the fluctuation value is less than the threshold (specifically, in this embodiment, the fluctuation threshold is set to 10µm), the current machine tool position (X2, Y2) is taken as position C, and the Z-axis coordinate Z2 is determined when the worktable end face coincides with the highest point of the second standard ball; otherwise, return to step T1.

[0099] The Z-axis coordinate Z2 when the end face of the worktable coincides with the highest point of the second standard sphere is calculated according to the following formula:

[0100] ;

[0101] Among them, Z gauge Represents the Z-axis coordinate value of the machine tool; L gauge This indicates the closest distance between the end face of the worktable and the second standard ball.

[0102] Specifically, L gauge You can remove the dial indicator, move the machine tool to position (X2, Y2), slowly lower the machine tool's Z-axis, and continuously insert gauge blocks and plug gauges into the worktable end face and between the second standard ball until no more plug gauges can be inserted. The total length of the gauge blocks and plug gauges used is L. gauge .

[0103] Step 3: Install the second standard ball 2 at the workpiece probe 1 position, set the swing axis B axis 3 to zero, adjust the rotating axis C axis 4 so that the rotating axis C axis is concentric with the second standard ball 2, and determine the position C of the machine tool when the rotating axis C axis 4 is concentric with the second standard ball 2;

[0104] Step four: Determine the relative positional relationship between the workpiece probe 1 and the second standard ball 2 by combining position B and position C;

[0105] The relative positional relationship between the workpiece probe 1 and the second standard ball 2 is determined according to the following formula:

[0106] ;

[0107] Where (X1, Y1, Z1) represents the position B coordinate of the machine tool when the workpiece probe 1 is concentric with the rotating axis C4; (X2, Y2, Z2) represents the position C coordinate of the machine tool when the rotating axis C4 is concentric with the second standard ball 2; (dX1, dY1, dZ1) represents the relative positional relationship between the workpiece probe 1 and the second standard ball 2.

[0108] Step 5: Based on the laser displacement sensor 8 on the machine tool worktable, determine the coordinates of the highest point of the second standard ball 2 and the highest point of the polishing wheel 6, and combine the coordinates of the highest point of the second standard ball 2 and the highest point of the polishing wheel 6 to determine the relative positional relationship between the highest point of the second standard ball 2 and the highest point of the polishing wheel 6.

[0109] In step five, the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel are determined based on the laser displacement sensor 8 on the machine tool worktable; including the following methods:

[0110] The coordinates (X, X) of the center of the second standard sphere 2 are obtained based on the laser displacement sensor 8 on the machine tool worktable. sphere2 Y sphere2 Z sphere2Specifically, the machine tool automatically rotates the swing axis B to -90° and moves to the position where the laser displacement sensor measures the second standard sphere. The laser displacement sensor measures the surface of the second standard sphere, and the actual point cloud data measured by the machine tool is recorded. And laser displacement sensor readings Based on point cloud data and the readings measured by the laser displacement sensor By performing a fixed-radius sphere center fitting, the coordinates (X3, Y3, Z3) of the highest point of the second standard sphere measured by the laser displacement sensor are obtained; then, by combining the radius R of the second standard sphere 2, a coordinate transformation is performed to obtain the coordinates (X3, Y3, Z3) of the highest point of the second standard sphere 2 measured by the laser displacement sensor 8.

[0111] ;

[0112] The coordinates (X, X) of the center of the polishing wheel 6 are obtained by the laser displacement sensor 8 on the machine tool worktable. wheel Y wheel Z wheel ) and the radius R of polishing wheel 6 wheel Then, the laser displacement sensor measures the coordinates (X4, Y4, Z4) of the highest point of the lower polishing wheel:

[0113] .

[0114] Step 6: Based on the relative positional relationship between the workpiece probe 1 and the second standard ball 2, and the relative positional relationship between the second standard ball 2 and the highest point of the polishing wheel 6, determine the relative positional relationship between the workpiece probe 1 and the highest point of the polishing wheel 6.

[0115] In step six, the relative positional relationship between the second standard ball 2 and the highest point of the polishing wheel 6 is determined according to the following formula:

[0116] ;

[0117] Where (X4, Y4, Z4) represents the position B coordinate of the machine tool when the workpiece probe is concentric with the rotating axis C; (X3, Y3, Z3) represents the position C coordinate of the machine tool when the rotating axis C is concentric with the second standard ball; (dX2, dY2, dZ2) represents the relative position relationship between the second standard ball 2 and the highest point of the polishing wheel 6.

[0118] The methods for determining the relative positional relationship between the workpiece probe 1 and the highest point of the polishing wheel 6 include:

[0119] ;

[0120] Where (dX, dY, dZ) represents the relative positional relationship between the workpiece probe and the highest point of the polishing wheel.

[0121] In this embodiment, the accuracy class of the first and second standard spheres is ±0.5 μm; the repeatability of the laser displacement sensor is <0.05 µm.

[0122] This solution achieves high-precision, automated calibration of the relative position between the workpiece probe and the highest point of the polishing wheel, as well as the structural parameters of the swing axis B-axis, in a fixed magnetorheological polishing machine with a lower polishing wheel by combining multi-axis linkage control of CNC code with spherical fitting algorithm. This reduces manual intervention and significantly shortens the calibration time compared to traditional manual calibration. Based on the dual-reference design, only local recalibration is required after replacing the probe or polishing wheel, greatly improving calibration efficiency.

[0123] Example 2

[0124] This embodiment provides a calibration system for a magnetorheological polishing machine tool with a fixed lower polishing wheel, used to implement the calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel described in Embodiment 1. The system includes:

[0125] The first calculation module is used to install the first standard ball on the machine tool worktable, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C axis is concentric with the first standard ball;

[0126] The second calculation module is used to move the machine tool to position A, adjust the swing axis B, fit the positional relationship between the swing axis B and the center of the first standard ball, and solve for the structural parameters of the swing axis B; and determine the position B of the machine tool when the workpiece probe and the rotating axis C are concentric.

[0127] The third calculation module is used to install the second standard ball at the workpiece probe position, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the second standard ball, and determine the position C of the machine tool when the rotating axis C axis is concentric with the second standard ball;

[0128] The fourth calculation module is used to determine the relative positional relationship between the workpiece probe and the second standard ball by combining position B and position C;

[0129] The fifth calculation module is used to determine the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel based on the laser displacement sensor on the machine tool workbench, and to determine the relative positional relationship between the second standard sphere and the highest point of the polishing wheel by combining the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel.

[0130] The sixth calculation module is used to determine the relative positional relationship between the workpiece probe and the highest point of the polishing wheel based on the relative positional relationship between the workpiece probe and the second standard ball, and the relative positional relationship between the second standard ball and the highest point of the polishing wheel.

[0131] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel, characterized in that the method... include: Install the first standard ball on the machine tool worktable, set the swing axis B to zero, adjust the rotating axis C to make the rotating axis C concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C is concentric with the first standard ball; Move the machine tool to position A, adjust the swing axis B, fit the positional relationship between the swing axis B and the center of the first standard ball, and solve for the structural parameters of the swing axis B; and determine the position B of the machine tool when the workpiece probe and the rotating axis C are concentric. Install a second standard ball at the workpiece probe position, set the swing axis B to zero, adjust the rotating axis C to make the rotating axis C concentric with the second standard ball, and determine the position C of the machine tool when the rotating axis C is concentric with the second standard ball. The relative positional relationship between the workpiece probe and the second standard ball is determined by combining positions B and C; The coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel are determined based on the laser displacement sensor on the machine tool worktable. The relative positional relationship between the second standard sphere and the highest point of the polishing wheel is determined by combining the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel. Based on the relative positional relationship between the workpiece probe and the second standard ball, and the relative positional relationship between the second standard ball and the highest point of the polishing wheel, the relative positional relationship between the workpiece probe and the highest point of the polishing wheel is determined.

2. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 1, characterized in that, The methods for determining location A include: S1, the workpiece probe measures the point cloud data of multiple points on the surface of the first standard sphere. Based on the point cloud data and the radius R of the first standard sphere, the coordinates of the center of the first standard sphere (X0, Y0, Z0) are fitted using the least squares method. sphere1 Y sphere1 Z sphere1 ), and based on the sphere center coordinates (X0, Y0, Z0), obtain the machine tool position (X1, Y1) = (X0, Y0) when the C-axis of the rotating shaft is concentric with the first standard sphere; S2, the machine tool moves to the position (X1, Y1) where the B-axis of the swing axis is zeroed, and the Z-axis coordinate value of the lowest point of the first standard ball is measured. sphere0 Adjust the C-axis to any angle θ, and measure the Z-axis coordinate value Z of the lowest point of the first standard sphere at this time. sphereθ ; S3, calculate Z sphere0 With Z sphereθ The difference between them, with a preset difference threshold, when Z sphere0 With Z sphereθ If the difference between the two values ​​is less than the difference threshold, output the current machine tool position (X1, Y1) = (X0, Y0) as position A; otherwise, return to step S1.

3. The calibration method for a fixed-position polishing wheel magnetorheological polishing machine tool according to claim 2, characterized in that, The positional relationship between the pendulum axis B and the center of the first standard sphere is fitted, and the structural parameters of the pendulum axis B are solved; including method: Adjust the pendulum axis B to an angle of ±θ i Fit the B-axis of the pendulum axis at angle ±θ i The center of the first standard ball According to the first standard ball at the angle ±θ from the B-axis of the pendulum. i The following spatial geometric positional relationships are: ； ； ； Where a represents the eccentricity of the swing axis B; b represents the vertical distance between the swing axis B and the machine tool table in the Z-axis direction; and h represents the vertical distance between the center of the first standard ball and the end face of the machine tool table in the Z-axis direction. and This represents the change in position of the center of the first standard sphere in the xoz plane at any angle θ between the center of the first standard sphere and the B-axis of the pendulum when the B-axis is set to zero. Solve for the structural parameters a and b of the pendulum axis B.

4. The calibration method for a fixed-position polishing wheel magnetorheological polishing machine tool according to claim 3, characterized in that, The methods for determining the position B of the machine tool when the workpiece probe is concentric with the C-axis include: Remove the first standard ball and set the B-axis of the swing axis to zero. Measure the Z-axis coordinate value Z of the machine tool table end face based on the workpiece probe. workbench By combining the coordinates (X0, Y0, Z0) of the center of the first standard sphere, the position B (X1, Y1, Z1) of the machine tool when the workpiece probe is concentric with the C-axis is obtained: ； 。 5. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 1, characterized in that, The methods for determining the position C of the machine tool when the rotating shaft C-axis is concentric with the second standard sphere include: T1. Install a dial indicator on the machine tool table and a second standard ball at the workpiece probe position. Rotate the machine tool table to measure the extreme points around the second standard ball based on the dial indicator: the leftmost point X. left The rightmost point X right The foremost point Y front and the last side point Y back ; T2, based on the extreme points around the second standard sphere, combined with the geometric symmetry relationship, the position C coordinate (X2, Y2) of the machine is obtained when the rotation axis C is concentric with the second standard sphere; T3, move the machine tool to coordinate (X2, Y2), continuously rotate the C-axis, measure the fluctuation value of the second standard ball based on the dial indicator, preset the fluctuation threshold, when the fluctuation value is less than the fluctuation threshold, take the current machine tool position (X2, Y2) as position C, and determine the Z-axis coordinate Z2 when the end face of the worktable coincides with the highest point of the second standard ball; otherwise, return to step T1.

6. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 5, characterized in that, The Z-axis coordinate Z2 when the end face of the worktable coincides with the highest point of the second standard sphere is calculated according to the following formula: ； Among them, Z gauge Indicates the Z-axis coordinate value of the machine tool; L gauge This indicates the closest distance between the end face of the worktable and the second standard ball.

7. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 1, characterized in that, The laser displacement sensor on the machine tool worktable determines the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel; including the following method: The center coordinates (X and Y) of the second standard sphere are obtained based on the laser displacement sensor on the machine tool table. sphere2 Y sphere2 Z sphere2 Using the radius R of the second standard sphere, coordinate transformation is performed to obtain the coordinates (X3, Y3, Z3) of the highest point of the second standard sphere as measured by the laser displacement sensor: ； The coordinates (X, X) of the polishing wheel's center are obtained using a laser displacement sensor on the machine tool's worktable. wheel Y wheel Z wheel and the radius R of the polishing wheel wheel The coordinates of the highest point of the lower polishing wheel measured by the laser displacement sensor are (X4, Y4, Z4): 。 8. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 1, characterized in that, The relative positional relationship between the workpiece probe and the second standard ball is determined according to the following formula: ； Where (X1, Y1, Z1) represents the position B coordinate of the machine tool when the workpiece probe is concentric with the C-axis; (X2, Y2, Z2) represents the position C coordinate of the machine tool when the C-axis is concentric with the second standard ball; (dX1, dY1, dZ1) represents the relative positional relationship between the workpiece probe and the second standard ball. The relative positional relationship between the second standard ball and the highest point of the polishing wheel is determined by the following formula: ； Where (X4, Y4, Z4) represents the position B coordinate of the machine tool when the workpiece probe is concentric with the C-axis; (X3, Y3, Z3) represents the position C coordinate of the machine tool when the C-axis is concentric with the second standard ball; (dX2, dY2, dZ2) represents the relative position relationship between the second standard ball and the highest point of the polishing wheel.

9. The calibration method for a magnetorheological polishing machine tool with a fixed lower polishing wheel according to claim 1, characterized in that, Methods for determining the relative positional relationship between the workpiece probe and the highest point of the polishing wheel include: ； Where (dX, dY, dZ) represents the relative positional relationship between the workpiece probe and the highest point of the polishing wheel.

10. A calibration system for a magnetorheological polishing machine tool with a fixed lower polishing wheel, characterized in that, A system for implementing the calibration method of a magnetorheological polishing machine tool with a fixed lower polishing wheel as described in any one of claims 1-9, the system comprising: The first calculation module is used to install the first standard ball on the machine tool worktable, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the first standard ball, and determine the position A of the machine tool when the rotating axis C axis is concentric with the first standard ball; The second calculation module is used to move the machine tool to position A, adjust the swing axis B, fit the positional relationship between the swing axis B and the center of the first standard ball, and solve for the structural parameters of the swing axis B; and determine the position B of the machine tool when the workpiece probe and the rotating axis C are concentric. The third calculation module is used to install the second standard ball at the workpiece probe position, set the swing axis B axis to zero, adjust the rotating axis C axis to make the rotating axis C axis concentric with the second standard ball, and determine the position C of the machine tool when the rotating axis C axis is concentric with the second standard ball; The fourth calculation module is used to determine the relative positional relationship between the workpiece probe and the second standard ball by combining position B and position C; The fifth calculation module is used to determine the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel based on the laser displacement sensor on the machine tool workbench, and to determine the relative positional relationship between the second standard sphere and the highest point of the polishing wheel by combining the coordinates of the highest point of the second standard sphere and the highest point of the polishing wheel. The sixth calculation module is used to determine the relative positional relationship between the workpiece probe and the highest point of the polishing wheel based on the relative positional relationship between the workpiece probe and the second standard ball, and the relative positional relationship between the second standard ball and the highest point of the polishing wheel.

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