A cradle type five-axis machine tool calibration method based on laser range finder

Abstract

The present invention discloses a mechanical calibration method for a cradle-type five-axis machine based on a laser rangefinder, which obtains the geometric information of the circle rotating around the C axis in the mechanical coordinate system under different A values. The angle γ of the mechanical XY axis is obtained. xy And the actual moving distance ratio of X axis and Y axis ratioXY; get the mechanical Z axis and XZ 参 Angle α between the two planes zx , mechanical Z axis and YZ 参 Angle β between the planes zy The actual X-axis to Z-axis motion ratio (ratioXZ) is calculated and adjusted to obtain the conversion relationship between the mechanical coordinate system and the reference coordinate system. The position and orientation of the AC axis in the reference coordinate system are obtained, completing five-axis coordinate calibration. This method allows the laser to be roughly aligned with the sphere's vertex under a few AC axis positions, automatically measuring the sphere's center coordinates and directly generating them. This approach is simple to operate, greatly simplifies the calibration process, and offers excellent practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical calibration of five-axis machines, and in particular relates to a mechanical calibration method of a cradle-type five-axis machine based on a laser rangefinder. Background Art

[0002] Compared to traditional three-axis machines, five-axis machines offer higher machining accuracy, higher efficiency, and the ability to process more complex workpieces, giving them a competitive advantage in the market. However, the addition of two rotating axes also complicates the mechanical structure of five-axis machines. This, combined with inherent geometric errors in the machine's structure and wear errors during operation, poses significant challenges in calibrating the geometric parameters of five-axis machines and eliminating these errors.

[0003] Most existing technologies use measuring instruments such as laser interferometers, micrometers, and ballbars to perform positioning accuracy detection and calibration on five-axis machines. However, these instruments have the following disadvantages:

[0004] ① The existing five-axis calibration technology has a complicated process, takes more time and is less efficient;

[0005] ② Because the process is complicated, the technical requirements for the technicians who implement the calibration are high;

[0006] ③ Calibration of measuring instruments such as ballbars and laser interferometers is expensive and will increase the manufacturer's cost in actual application.

[0007] ④ The actual movement distance of the translation axis sent by the instruction is affected by human settings. Setting accurate actual movement distance instructions requires high measurement operations and the calibration accuracy is insufficient.

[0008] Therefore, the present invention provides a cradle-type five-axis machine mechanical calibration method based on a laser rangefinder. The present invention only requires the laser rangefinder to obtain the sphere center technology to obtain the mechanical coordinates of the calibration sphere in different positions to complete the five-axis machine calibration, which greatly simplifies the relevant processes and reduces the use cost. Summary of the Invention

[0009] The purpose of the present invention is to provide a mechanical calibration method for a cradle-type five-axis machine based on a laser rangefinder, aiming to solve the above problems.

[0010] The present invention is mainly achieved through the following technical solutions:

[0011] A cradle-type five-axis machine mechanical calibration method based on a laser rangefinder establishes a reference coordinate system with the position of the laser emission at the mechanical coordinate origin as the origin. Due to errors, the mechanical coordinate system is an oblique coordinate system, and the mechanical coordinate data corresponding to the coordinates of the circular trajectory points rotating in actual space are ellipses. Based on the rotation around the C axis under different A values, the ellipse information of the mechanical coordinate data of multiple points in the mechanical coordinate system is fitted to establish a connection between the mechanical coordinate system and the reference coordinate system, and the position and direction of the AC axis in the reference coordinate system are obtained, which is the basis for realizing five-axis linkage machining. The method includes the following steps:

[0012] Step S100: obtaining the center position of the sphere under different postures of the rotation axis;

[0013] Step S200: Get the geometric information of the circle rotating around the C axis under different A values ​​in the mechanical coordinate system: Get the mechanical coordinates of multiple sphere centers that rotate the C axis at different A axis angles. Let the mechanical coordinates of the sphere center include the mechanical coordinates of the XYZ axis coordXYZ M =[X i ,Y i ,Z i ] T , mechanical coordinates of AC axis coordAC M =[A i ,C i ] T ;

[0014] Step S300: When the machine plane is nearly parallel to the mechanical XY plane, the machine C axis rotates, and the coordinates of the sphere center in the mechanical coordinate system are obtained at regular intervals. After one rotation, the coordinates of the sphere center at different C values ​​are obtained. The number of coordinates is greater than or equal to 6. An ellipse can be fitted from these coordinates, and the angle γ of the mechanical XY axis can be obtained from the ellipse information. xy And the ratio of the actual moving distance of the X axis to the Y axis ratioXY;

[0015] Step S400: When the A axis is in different postures, the calibration ball rotates around the C axis to obtain the mechanical coordinates of multiple points, and based on the fitted ellipse, the mechanical Z axis and XZ are obtained. 参 Angle α between the two planes zx , mechanical Z axis and YZ 参 Angle β between the planes zy And the ratio of the actual movement distance between the X axis and the Z axis ratioXZ;

[0016] Step S500: Considering the situation where the actual moving distances of different translation axes are different when the same movement distance instruction is sent, the conversion relationship between the mechanical coordinate system and the reference coordinate system is corrected and adjusted:

[0017] The conversion relationship from the reference coordinate system (x, y, z) to the mechanical coordinate system (x', y', z') is as follows:

[0018] from

[0019] The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0020]

[0021] Step S600: Obtaining the position and direction information of the AC axis in the reference coordinate system: Obtain the rotation circle of the A axis at different postures in the reference coordinate system. From the circle information, obtain the AC axis information, including a point on the A axis and the A axis direction, a point on the C axis and the C axis direction, the ratio ka of the actual rotation angle of the A axis to the change angle of the A axis mechanical coordinate, and the ratio kc of the actual rotation angle of the C axis to the change angle of the C axis mechanical coordinate.

[0022] Step S700: Complete five-axis coordinate calibration.

[0023] In order to better implement the present invention, further, the step S200 includes calibrating the position of the calibration ball in a certain posture:

[0024] a. The laser is placed on the Z axis, the optimal laser measurement distance is set to d, and the calibration sphere radius is r;

[0025] b. Align the laser beam with the vertex of the sphere and ensure that the laser distance is close to the optimal measurement distance d. Assume the current machine coordinates are (x, y, z);

[0026] c. Start from the vertex of an ideal sphere and make a circle every 10 degrees downward. Then, we can get circles of 10 degrees, 20 degrees, 30 degrees, and 40 degrees. Then, we can get corresponding points every 60 degrees on each circle. We can calculate the relative position of all points relative to the vertex (dx j ,dy j ,dz j ),

[0027] Based on the mechanical coordinates (x, y, z) of the ball vertex, move the ball to all (x+dx j ,y+dy j ,z+dz j ) point, and obtain the corresponding laser distance d j激光 ;

[0028] d. Let (x+dx j ,y+dy j ,z+dz j +d j激光) is the virtual mechanical coordinate of the spherical point, all the obtained virtual mechanical coordinates of the spherical points are fitted into a sphere to obtain the center position (centerX1, centerY1, centerZ1), and the actual mechanical coordinate position of the next laser alignment center (centerX1, centerY1, centerZ1-d-r) is obtained, at this time, the laser is more accurately aligned with the center of the sphere, and the distance between the laser and the surface of the sphere is always close to d;

[0029] e. The mechanical coordinate is moved to (centerX1, centerY1, centerZ1-d-r) to make the laser align with the center position of the sphere, and the above steps b-d are repeated to realize the whole calibration of the sphere position.

[0030] In order to better realize the present application, further, in the step S200, since the final obtained laser ranging at different positions of the sphere is not the same, it is affected by the linearity of laser ranging, the inclination of different points of the sphere, and the parallelism of the laser and the z-axis, therefore, it further includes establishing the mapping relationship of different points of the sphere:

[0031] The mapping relationship of the ideal mechanical coordinate and the virtual mechanical coordinate of each point of the sphere is established to obtain the center coordinate of the sphere:

[0032] The following spherical mechanical coordinates are the actual mechanical coordinates (x, y, z) + the virtual mechanical coordinates (0, 0, d) of the spherical points during measurement, and the mapping relationship of different points of the sphere is established:

[0033] A series of virtual mechanical coordinates of the sphere under one posture are fitted into a sphere to obtain the center (ballX, ballY, ballZ), and a series of ideal point coordinates on the sphere when the center is (ballX, ballY, ballZ) under ideal conditions are obtained; the virtual mechanical coordinates are subtracted by the corresponding ideal point coordinates, and the mapping difference values (MapX i , MapY i , MapZ i ) of the corresponding points are obtained.

[0034] After the mapping relationship is established, when a sphere is fitted, the virtual mechanical coordinates on the sphere are first subtracted by the mapping difference values (MapX i , MapY i , MapZ i ) of the corresponding points to obtain new virtual coordinates, and then the new virtual coordinates are used to fit the sphere to obtain the center coordinate, which is the finally obtained center coordinate.

[0035] In order to better realize the present application, further, the step S300 includes the following steps:

[0036] Assume a circle in the XY plane. The circle equation is:

[0037] x 2 +y 2 =r 2 (1)

[0038] When the XY plane is roughly parallel to the machine rotation plane, the deviation between the ideal and actual Z axis has little effect on the calculation of XY axis related parameters. In this case, the Z axis is not considered, and the conversion relationship from the mechanical axis to the ideal coordinate system is:

[0039]

[0040] The k value is the ratio of the actual moving distance of the X axis to the Y axis,

[0041] x, y are the coordinates of the reference system,

[0042] x′, y′ are the coordinates of the mechanical coordinate system,

[0043] Substituting x and y into the circle equation (1), we get the ellipse equation with respect to the mechanical coordinates:

[0044] x′ 2 +2ksinγx′y′+k 2 y′ 2 =r 2

[0045] Assume the general equation of an ellipse:

[0046] Ax 2 +Bxy+Cy 2 +Dx+Ey+1=0

[0047] Then: Long axis inclination

[0048] Axis-length ratio

[0049] in

[0050] Substituting formula (5) into formula (3) and formula (4) yields:

[0051]

[0052]

[0053] A spatial ellipse can be fitted from the several mechanical coordinates obtained above. Then the plane where the spatial ellipse is located is rotated to the XY plane. At this time, the major axis inclination angle θ and the major and minor axis ratio a / b of the ellipse in the XY plane can be obtained, and the XY angle γ in the above formulas (6) and (7) can be solved. xy, and the ratio of the actual moving distance between the X axis and the Y axis ratioXY.

[0054] In order to better implement the present invention, step S400 further includes the following steps:

[0055] Assume that the X, Y, and Z axes send motion commands of equal length and move the same distance. The conversion relationship from the reference coordinate system (x, y, z) to the machine coordinate system (x', y', z') is as follows:

[0056] from

[0057] The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0058]

[0059] Let the parametric equation of the circle be:

[0060]

[0061] Substituting formula (7) into formula (8), we can obtain the corresponding ellipse equation in the mechanical coordinate system:

[0062]

[0063] make

[0064] The solution is:

[0065]

[0066]

[0067]

[0068] Set up the equation:

[0069]

[0070] Observation form, if the angle γ xy =0, then from formula (9)-formula (12) we can get:

[0071]

[0072] If the above (1+(tanα) 2 +(tanβ) 2 )λ 2, λtanα, λtanβ, r, are unknown quantities, (u1, u2, u3) and (v1, v2, v3) are the major axis vector and minor axis vector of the space ellipse, which can be obtained by fitting the measured data;

[0073] Depend on z=z'λ,(1+(tanα) 2 +(tanβ) 2 )γ 2 =1,

[0074] Taking into account the influence of the pulse equivalent setting, the conversion relationship between the mechanical Z axis and the Z value of the reference coordinate system is:

[0075]

[0076] Therefore, (1+(tanα) 2 +(tanβ) 2 )γ 2 =k 2

[0077] Because the above variables are the same for all rotating circles, the overdetermined equations can be established based on the information of the ellipse fitted when A is at different angles;

[0078] In addition, discard equation ① in formula (15),

[0079] The calibration ball rotates around the C axis for a circle when the A axis is in different postures, and the ellipse is fitted using the least squares method. Then, an overdetermined equation is established based on the major and minor axis vectors of these ellipses. The mechanical axis Z and the XZ axis can be solved by the overdetermined equation. 参 Angle α between the two planes zx , Z mechanical axis and YZ 参 Angle β between the planes zy , the ratio of the actual moving distance of the X axis to the Z axis is ratioXZ.

[0080] To better implement the present invention, further, in step S700, in order to keep the relative position of a specific point on the tool or workpiece in space unchanged, it is necessary to obtain the real-time coordinates of the specific point as the AC axis changes. Suppose a certain mechanical coordinate changes from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1):

[0081] Step S710: Obtain the direction ν of the C axis when the A axis is a c1 and a point t on the axis c1 ;

[0082] Step S720: The mechanical coordinates of point A are converted to reference coordinates A 参1 ;

[0083] Step S730: Set the reference coordinate A 参1 Rotate (c1-c)kc around the C axis to get A 参2 ;

[0084] Step S740: A 参2 Rotate (a1-a)ka around axis A to get A 参3 ;

[0085] Step S750: A 参3 Switch to the mechanical coordinate system, which is A1(x1,y1,z1).

[0086] The glossary of the present invention is explained as follows:

[0087] Reference coordinate system: standard Cartesian coordinate system.

[0088] Controlled variable method: This method reduces the error in estimating unknown quantities by understanding known quantities. To determine the center of the calibration sphere, the center is fitted several times. This ensures that the distance from the laser to the calibration sphere surface approaches the set value with each remeasurement, and the laser measurement starting point is increasingly accurately aligned with the sphere's center.

[0089] Repeatability: For a certain mechanical coordinate, if the actual spatial position corresponding to the mechanical coordinate is always basically at the same point after the five-axis machine moves, the repeatability is high. On the contrary, if the actual corresponding spatial position has a large deviation when returning to the same mechanical coordinate, the repeatability is poor.

[0090] Positioning accuracy: For a specific XYZ axis, if the same movement distance command is sent at different positions and the axis moves the same distance, the positioning accuracy is high. If there is a large deviation in the movement distance, the positioning accuracy is insufficient. For a specific AC axis, if the same movement distance command is sent at different positions and the axis rotates the same angle, the positioning accuracy is high. If there is a large deviation in the rotation angle, the positioning accuracy is insufficient.

[0091] Beneficial effects of the present invention:

[0092] (1) The present invention obtains the center position of the sphere by laser ranging using the control variable method; and for a five-axis machine with good repeatability and positioning accuracy and good rigid connection of the rotating axis, based on the rotation trajectory of a point on the machine platform around the C-axis as a good circle, the elliptical geometric information of the mechanical coordinate fitting of the rotating circle around the C-axis in the mechanical coordinate system measured at different A values ​​is used to establish the connection between the machine tool coordinate system and the reference coordinate system, thereby realizing five-axis calibration;

[0093] (2) After simulation testing, the mechanical axis related information obtained above can achieve very high accuracy. Under the premise of good repeatability and positioning accuracy of the AC axis, the calibration accuracy and measurement accuracy are basically consistent. After actual machine verification, after the mechanical calibration is realized in the above way, from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1), the relative position of a specific point on the tool or workpiece in space remains unchanged. For a five-axis machine with good positioning accuracy, very high accuracy can be achieved.

[0094] (3) The laser distance measurement technology of the present invention to obtain the calibration ball center has relatively low performance requirements for the laser rangefinder and high measurement accuracy. For a five-axis machine with high mechanical repeatability and positioning accuracy and good AC axis rigid connection, the calibration of the XYZ axis is realized, the connection between the mechanical XYZ axis coordinate system and the Cartesian reference coordinate system is established, and the direction and position of the C axis and the A axis in the reference coordinate system that changes with the AC mechanical coordinate are obtained, thereby achieving high-precision calibration. All the above information only requires the operator to roughly align the laser with the apex of the ball under a few AC axis postures, and automatically measure the coordinates of the sphere center to directly generate it. The operation is simple, which greatly simplifies the calibration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 is an overall flow chart of the calibration method of the present invention;

[0096] Figure 2 This is a schematic diagram of the structure of the calibration ball in a certain posture;

[0097] Figure 3 A schematic diagram of establishing a reference coordinate system with the mechanical x-axis as the reference axis and the z-axis perpendicular to the plane formed by the x-axis and y-axis;

[0098] Figure 4 Flowchart for real-time coordinate calibration of a specific point as it changes along the AC axis. DETAILED DESCRIPTION

[0099] Example 1:

[0100] A mechanical calibration method for a cradle-type five-axis machine based on a laser rangefinder establishes a reference coordinate system with the position of the laser emission at the mechanical coordinate origin as the origin. Due to errors, the mechanical coordinate system is an oblique coordinate system, and the mechanical coordinate data corresponding to the coordinates of the circular trajectory points rotating in actual space are ellipses. Based on the rotation around the C-axis under different A values, the elliptical information of the mechanical coordinate data of multiple points in the mechanical coordinate system is fitted to establish a connection between the mechanical coordinate system and the reference coordinate system, and the position and direction of the AC axis in the reference coordinate system are obtained, which is the basis for realizing five-axis linkage machining.

[0101] Preferably, if Figure 1As shown, the present invention includes the following steps:

[0102] Step S100: obtaining the center position of the sphere under different postures of the rotation axis;

[0103] Step S200: Get the geometric information of the circle rotating around the C axis under different A values ​​in the mechanical coordinate system: Get the mechanical coordinates of multiple sphere centers that rotate the C axis at different A axis angles. Let the mechanical coordinates of the sphere center include the mechanical coordinates of the XYZ axis coordXYZ M =[X i ,Y i ,Z i ] T , mechanical coordinates of AC axis coordAC M =[A i ,C i ] T ;

[0104] Step S300: When the machine plane is roughly parallel to the mechanical XY plane, the machine C axis rotates, and the coordinates of the sphere center in the mechanical coordinate system are obtained at regular intervals. After one rotation, the coordinates of the sphere center at different C values ​​are obtained. The number of coordinates is greater than or equal to 6. An ellipse can be fitted from these coordinates, and the angle γ of the mechanical XY axis can be obtained from the ellipse information. xy And the ratio of the actual moving distance of the X axis to the Y axis ratioXY;

[0105] Step S400: When the A axis is in different postures, the calibration ball rotates around the C axis to obtain the mechanical coordinates of multiple points, and based on the fitted ellipse, the mechanical Z axis and XZ axis are obtained. 参 Angle α between the two planes zx , mechanical Z axis and YZ 参 Angle β between the planes zy And the ratio of the actual movement distance between the X axis and the Z axis ratioXZ;

[0106] Step S500: Considering the situation where the actual moving distances of different translation axes are different when the same movement distance instruction is sent, the conversion relationship between the mechanical coordinate system and the reference coordinate system is corrected and adjusted:

[0107] The conversion relationship from the reference coordinate system (x, y, z) to the mechanical coordinate system (x', y', z') is as follows:

[0108] from

[0109] The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0110]

[0111] Step S600: Obtaining the position and direction information of the AC axis in the reference coordinate system: Obtain the rotation circle of the A axis at different postures in the reference coordinate system. From the circle information, obtain the AC axis information, including a point on the A axis and the A axis direction, a point on the C axis and the C axis direction, the ratio ka of the actual rotation angle of the A axis to the change angle of the A axis mechanical coordinate, and the ratio kc of the actual rotation angle of the C axis to the change angle of the C axis mechanical coordinate.

[0112] Step S700: Complete five-axis coordinate calibration.

[0113] Preferably, the step S200 includes calibrating the position of the calibration ball in a certain posture:

[0114] a. The laser is placed on the Z axis, the optimal laser measurement distance is set to d, and the calibration sphere radius is r;

[0115] b. Make the laser beam align with the vertex of the sphere and the laser distance close to the optimal measurement distance d, set the current mechanical coordinates

[0116] is (x,y,z);

[0117] c. Start from the vertex of an ideal sphere and make a circle every 10 degrees downward. Then, we can get circles of 10 degrees, 20 degrees, 30 degrees, and 40 degrees. Then, we can get corresponding points every 60 degrees on each circle. We can calculate the relative position of all points relative to the vertex (dx j ,dy j ,dz j ),

[0118] Based on the mechanical coordinates (x, y, z) of the ball vertex, move the ball to all (x+dx j ,y+dy j ,z+dz j ) point, and obtain the corresponding laser distance d j激光 ;

[0119] d. Let (x+dx j ,y+dy j ,z+dz j +d j激光 ) is the virtual mechanical coordinate of the spherical point. All the obtained virtual mechanical coordinates of the spherical points are fitted to the sphere using the least squares method to obtain the center position of the sphere (centerX1, centerY1, centerZ1). The actual mechanical coordinate position of the sphere center when the laser is aimed at the next time is obtained (centerX1, centerY1, centerZ1-dr). At this time, the laser is more accurately aimed at the center of the sphere, and the distance between the laser and the surface of the sphere is always close to d.

[0120] e. Move the mechanical coordinates to (centerX1, centerY1, centerZ1-dr) so that the laser is aligned with the center of the ball, and repeat steps b to complete the calibration of the ball position.

[0121] Preferably, in step S200, since the laser ranging obtained at different positions on the spherical surface is different, it will be affected by the linearity of the laser ranging, the inclination of different points on the spherical surface, and the parallelism of the laser and the z-axis. Therefore, the mapping relationship between different points on the spherical surface is further established:

[0122] Establish the mapping relationship between the ideal mechanical coordinates of each point on the sphere and the virtual mechanical coordinates to obtain the coordinates of the center of the sphere:

[0123] The following spherical mechanical coordinates are the actual mechanical coordinates (x, y, z) + the virtual mechanical coordinates (0, 0, d) of the spherical point during measurement, and the mapping relationship between different points on the sphere is established:

[0124] Use a series of virtual mechanical coordinates obtained by measuring a sphere in a certain posture to fit a sphere, and get the center of the sphere (ballX, ballY, ballZ). In the ideal case, get a series of ideal point coordinates on the sphere when the center of the sphere is (ballX, ballY, ballZ); subtract the corresponding ideal point coordinates from the virtual mechanical coordinates to get the mapping difference of the corresponding points (MapX i ,MapY i ,MapZ i );

[0125] After the mapping relationship is established, when fitting a sphere, first use the virtual mechanical coordinates on the sphere to subtract the mapping difference corresponding to each point (MapX i ,MapY i ,MapZ i ), get the new virtual coordinates, and then use the new virtual coordinates to fit the sphere to get the coordinates of the sphere center, which are the final coordinates of the sphere center.

[0126] Preferably, the step S300 includes the following steps:

[0127] Assume a circle in the XY plane. The circle equation is:

[0128] x 2 +y 2 =r 2 (1)

[0129] When the XY plane is roughly parallel to the machine rotation plane, the deviation between the ideal and actual Z axis has little effect on the calculation of XY axis related parameters. In this case, the Z axis is not considered, and the conversion relationship from the mechanical axis to the ideal coordinate system is:

[0130]

[0131] The k value is the ratio of the actual moving distance of the X axis to the Y axis,

[0132] x,y are the coordinates of the reference system,

[0133] x′, y′ are the coordinates of the mechanical coordinate system,

[0134] Substituting x and y into the circle equation (1), we get the ellipse equation with respect to the mechanical coordinates:

[0135] x′ 2 +2ksinγx′y′+k 2 y′ 2 =r 2

[0136] Assume the general equation of an ellipse:

[0137] Ax 2 +Bxy+Cy 2 +Dx+Ey+1=0

[0138] Then: Long axis inclination

[0139] Axis-length ratio

[0140] in

[0141] Substituting formula (5) into formula (3) and formula (4) yields:

[0142]

[0143]

[0144] A spatial ellipse can be fitted from the several mechanical coordinates obtained above. Then the plane where the spatial ellipse is located is rotated to the XY plane. At this time, the major axis inclination angle θ and the major and minor axis ratio a / b of the ellipse in the XY plane can be obtained, and the XY angle γ in the above formulas (6) and (7) can be solved. xy , and the ratio of the actual moving distance between the X axis and the Y axis ratioXY.

[0145] Preferably, the step S400 includes the following steps:

[0146] Assume that the X, Y, and Z axes send motion commands of equal length and move the same distance. The conversion relationship from the reference coordinate system (x, y, z) to the machine coordinate system (x', y', z') is as follows:

[0147] from

[0148] The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0149]

[0150] Let the parametric equation of the circle be:

[0151]

[0152] Substituting formula (7) into formula (8), we can obtain the corresponding ellipse equation in the mechanical coordinate system:

[0153]

[0154] make The solution is:

[0155]

[0156]

[0157]

[0158] Set up the equation:

[0159]

[0160] Observation form, if the angle γ xy =0, then from formula (9)-formula (12) we can get:

[0161] (15)

[0162] If the above (1+(tanα) 2 +(tanβ) 2 )λ 2 , λtanα, λtanβ, r, are unknown quantities, (u1, u2, u3) and (v1, v2, v3) are the major axis vector and minor axis vector of the space ellipse, which can be obtained by fitting the measured data;

[0163] Depend on z=z'λ,(1+(tanα) 2 +(tanβ) 2 )γ 2 =1,

[0164] Taking into account the influence of the pulse equivalent setting, the conversion relationship between the mechanical Z axis and the Z value of the reference coordinate system is:

[0165]

[0166] Therefore, (1+(tanα)2 +(tanβ) 2 )γ 2 =k 2

[0167] Because the above variables are the same for all rotating circles, the overdetermined equations can be established based on the information of the ellipse fitted when A is at different angles;

[0168] In addition, discard equation ① in formula (15),

[0169] The calibration ball rotates around the C axis for a circle when the A axis is in different postures, and the ellipse is fitted using the least squares method. Then, an overdetermined equation is established based on the major and minor axis vectors of these ellipses. The mechanical axis Z and the XZ axis can be solved by the overdetermined equation. 参 Angle α between the two planes zx , Z mechanical axis and YZ 参 Angle β between the planes zy , the ratio of the actual moving distance of the X axis to the Z axis is ratioXZ.

[0170] Preferably, if Figure 4 As shown, in step S700, in order to keep the relative position of a specific point on the tool or workpiece in space unchanged, it is necessary to obtain the real-time coordinates of the specific point as it changes with the AC axis. Suppose a certain mechanical coordinate changes from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1):

[0171] Step S710: Obtain the direction ν of the C axis when the A axis is a c1 and a point t on the axis c1 ;

[0172] Step S720: The mechanical coordinates of point A are converted to reference coordinates A 参1 ;

[0173] Step S730: Set the reference coordinate A 参1 Rotate (c1-c)kc around the C axis to get A 参2 ;

[0174] Step S740: A 参2 Rotate (a1-a)ka around axis A to get A 参3 ;

[0175] Step S750: A 参3 Switch to the mechanical coordinate system, which is A1(x1,y1,z1).

[0176] The laser ranging of the present application has relatively low performance requirement for the laser ranging instrument, and high measurement precision. For a five-axis machine with high mechanical repeat positioning precision, high positioning precision and good rigidity of AC axis connection, XYZ axis calibration is realized, the relationship between the mechanical XYZ axis coordinate system and the Cartesian reference coordinate system is established, the direction and position of the C axis and the A axis in the reference coordinate system and the AC mechanical coordinate are obtained, and high-precision calibration is realized. All the above information is directly generated after the laser is roughly aligned with the ball top point under a few AC axis postures, and the ball center coordinates are automatically measured, which is simple to operate and greatly simplifies the calibration process.

[0177] Example 2:

[0178] A cradle type five-axis machine mechanical calibration method based on a laser ranging instrument, which is based on the premise that the five-axis repeat positioning precision, the five-axis positioning precision are high, and the AC axis connection rigidity is good. The trajectory of a fixed point on the machine rotating around the C axis is a good circle in space. The principle is to obtain the ball center technology by using a laser ranging instrument. The relationship between the machine tool coordinate system and the reference coordinate system is established by fitting the elliptical geometric information of a series of mechanical coordinates of the calibration ball center rotating around the C axis under different A values. The direction and position information of the AC axis in the reference coordinate system are obtained from the circular data of the measured circle in the reference coordinate system. Finally, the five-axis mechanical calibration is completed, and the basis for five-axis linkage machining is realized.

[0179] I. Calibration principle and purpose:

[0180] The reference coordinate system is established with the position of the laser emission when the mechanical coordinates are (0, 0, 0) as the origin. Since the XYZ axis of the mechanical coordinate system has errors, the mechanical XYZ axis constitutes an inclined coordinate system, and the actual space rotating circular trajectory point coordinates in the inclined coordinate system are an ellipse. The relationship between the mechanical coordinate system and the reference coordinate system can be established according to the elliptical information of the multiple point mechanical coordinate data fitting of the rotating circle around the C axis under different A values, and the position and direction of the AC axis in the reference coordinate system are obtained, which is the basis for five-axis linkage machining. According to the above information, the tracking conversion from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y1, z1, a1, c1) can be realized (a→a1, c→c1, x1, y1, z1 are calculated to make the relative position of a certain point on the tool or workpiece always remain unchanged).

[0181] II. Mechanical structure of five-axis point glue machine:

[0182] The cradle-style five-axis machine primarily consists of a machine base, three translational axes (X, Y, and Z), and two rotational axes (A and C). Linking the machine base to each axis, and connecting the axes to each other, forms a machining kinematic chain, enabling five-axis linkage. During motion, based on the principles of robotic kinematics, the five-axis dispensing machine's machine base, motion axes, needle valve, workpiece, and camera are all considered rigid bodies, thus dividing the rigid-body mechanical structure into two machining kinematic chains.

[0183] 1. Machine tool base → X-axis → Z-axis → needle head.

[0184] 2. Machine tool base → Y axis → A axis → C axis → workpiece coordinate system.

[0185] With the above concepts, you can perform mechanical calibration operations, such as Figure 1 As shown, the main steps are as follows:

[0186] Get the position of the center of the ball under different postures of the rotation axis;

[0187] Get the geometric information of the circle rotating around the C axis in the mechanical coordinate system under different A values;

[0188] Get the verticality of XY axis and the ratio of actual movement distance;

[0189] Obtain the verticality of the mechanical Z axis and the Z axis of the reference coordinate system, as well as the ratio of the actual movement distance;

[0190] Get the transformation relationship between the coordinate system and the reference coordinate system;

[0191] Get the position and direction information of the AC axis in the reference coordinate system;

[0192] Complete five-axis coordinate calibration.

[0193] 3. The detailed steps and related principles are as follows:

[0194] 1. Measurement data and method principles:

[0195] (1) Measurement data:

[0196] Get multiple sphere center mechanical coordinates for rotating the C axis at different A axis angles. Assume that the sphere center mechanical coordinates include the XYZ axis mechanical coordinates coordXYZ M =[X i ,Y i ,Z i ] T , mechanical coordinates of AC axis coordAC M =[A i ,C i ] T .

[0197] (2) Measurement principle:

[0198] Considering factors such as the parallelism between the laser and the Z axis and the poor linearity of the laser, which can affect the mechanical coordinate accuracy of the sphere's center, the control variable method is used to determine the sphere's center position. This method is simple to implement, highly accurate, and requires minimal equipment performance. A standard laser can meet measurement requirements.

[0199] (3) The specific measurement process of the calibration ball position in a certain posture is as follows:

[0200] a. The laser is placed on the Z axis, roughly parallel to the Z axis and pointing vertically downward. Assume that the optimal measurement distance of the laser is d and the radius of the calibration sphere is r.

[0201] b. Roughly align the laser beam with the apex of the sphere and keep the laser distance close to the optimal measurement distance d. Assume the current machine coordinates are (x, y, z).

[0202] c. Press Figure 2 As shown, an ideal sphere is started from the vertex and a circle is obtained every 10 degrees downward, so circles of 10, 20, 30, and 40 degrees are obtained, and corresponding points are obtained every 60 degrees on each circle, as shown in FIG. Figure 2 As shown (the points drawn in the figure).

[0203] Calculate the relative position of all points relative to the vertex (dx j ,dy j ,dz j ), relative position (dx j ,dy j ,dz j ) are all ideal data.

[0204] Based on the mechanical coordinates (x, y, z) roughly aligned with the ball vertex, move the ball to all (x+dx j ,y+dy j ,z+dz j ) point, and obtain the corresponding laser distance d j激光 .

[0205] d. Let (x+dx j ,y+dy j ,z+dz j +d j激光) are the virtual mechanical coordinates of the spherical point. The least squares method is used to fit the obtained virtual mechanical coordinates of all spherical points to a sphere, obtaining the sphere center position (centerX1, centerY1, centerZ1). The actual mechanical coordinate position of the sphere center for the next laser alignment is also obtained (centerX1, centerY1, centerZ1 - dr). At this point, the laser is more accurately aligned with the sphere center, and the distance between the laser and the sphere surface is always close to d.

[0206] e. Move the mechanical coordinates to (centerX1, centerY1, centerZ1-dr) so that the laser is aligned with the center of the sphere and repeat steps b, c, and d above.

[0207] (4) Establish the mapping relationship between the ideal mechanical and virtual mechanical coordinates of each point on the sphere to obtain the coordinates of the center of the sphere:

[0208] Since the final laser distance measurement at different points on the sphere is different, it will be affected by factors such as the laser distance linearity, the inclination of different points on the sphere, and the parallelism of the laser and the z-axis. A mapping relationship between different points on the sphere can be established. (The following spherical mechanical coordinates are the actual mechanical coordinates (x, y, z) + (0, 0, d) during measurement are virtual mechanical coordinates of the spherical point)

[0209] The method to establish the mapping relationship is:

[0210] ① Fit a ball using a series of virtual mechanical coordinates obtained from measurements of a spherical surface in a certain posture to obtain the center of the ball (ballX, ballY, ballZ).

[0211] ② Under ideal conditions, obtain a series of ideal point coordinates on the sphere when the center of the sphere is (ballX, ballY, ballZ). Subtract the virtual mechanical coordinates from the corresponding ideal point coordinates to obtain the mapping difference of the corresponding points (MapX i ,MapY i ,MapZ i ).

[0212] ③ After the mapping relationship is established, when fitting a sphere, first use the virtual mechanical coordinates on the sphere to subtract the mapping difference corresponding to each point (MapX i ,MapY i ,MapZ i ), get the new virtual coordinates, and then use the new virtual coordinates to fit the sphere to get the coordinates of the sphere center, which are the final coordinates of the sphere center.

[0213] The results show that the laser ranging distances measured at different points on the sphere vary significantly, but the distances measured at corresponding points on the sphere at different positions are very close. Using the mapped laser distances corresponding to the spherical points to fit the sphere, the mechanical coordinates of the sphere's center are very accurate.

[0214] 2. Schematic diagram of the mechanical coordinate system and the reference coordinate system.

[0215] like Figure 3 As shown, a reference coordinate system is established with the mechanical x-axis as the reference axis and the z-axis perpendicular to the plane formed by the x-axis and the y-axis.

[0216] γ xy The angle between the Y mechanical axis and the reference axis is positive when it points in the positive x direction.

[0217] α zx The mechanical axis of Z and XZ 参 The angle of the plane, pointing to Y 参 The axis direction is positive; β zy The mechanical axis of Z and YZ 参 The angle of the plane, pointing to X 参 The axis direction is positive.

[0218] Assume that the device sends the same movement distance command, the actual movement distance ratio of the X-axis to the Y-axis is ratioXY, and the actual movement distance ratio of the X-axis to the Z-axis is ratioXZ.

[0219] 3. When the machine plane is roughly parallel to the mechanical XY plane, the angle γ of the mechanical XY axis can be obtained xy The ratio of the actual moving distance between the X-axis and the Y-axis is ratioXY.

[0220] The calculation is as follows:

[0221] When the machine plane is roughly parallel to the mechanical XY plane, the machine C axis rotates, and the coordinates of the sphere center in the mechanical coordinate system are obtained at regular intervals. After one rotation, the coordinates of the sphere center at different C values ​​are obtained (at least 6 point coordinates are obtained). These coordinates can be used to fit an ellipse, and the angle γ of the mechanical XY axis can be obtained from the ellipse information. xy The ratio of the actual moving distance between the X-axis and the Y-axis is ratioXY.

[0222] The formula is derived as follows: Assume that a circle is in the XY plane.

[0223] x 2 +y 2 =r 2 (1)

[0224] When the XY plane is approximately parallel to the machine rotation plane, the deviation between the ideal and actual Z axes has little effect on the calculation of the XY axis-related parameters. In this case, the Z axis is not considered. The conversion relationship between the mechanical axes and the ideal coordinate system is as follows:

[0225]

[0226] (the k value above is the ratio of the actual movement distances of the X and Y axes, ratioXY. Here, x and y are the reference system coordinates, and x' and y' are the mechanical coordinate system coordinates).

[0227] Substituting x and y into the circle equation (1), an elliptical equation about the mechanical coordinates is obtained

[0228] x' 2 +2ksinγx′y′+k 2 y′2=r 2

[0229] Let the general equation of the ellipse be:

[0230] Ax 2 +Bxy+Cy 2 +Dx+Ey+1=0

[0231] The long-axis inclination angle is: The long-to-short axis ratio is:

[0232] wherein, Substituting (5) into (3) and (4) gives

[0233]

[0234]

[0235] From the above, some mechanical coordinates can be fitted into a spatial ellipse. Then, the plane on which the spatial ellipse is located is rotated to the XY plane. At this time, the long-axis inclination angle θ and the long-to-short axis ratio a / b of the ellipse in the XY plane can be obtained. Thus, the XY angle γ (γ xy ) and the actual movement distance ratio k (ratioXY) in the above equations (6) and (7) can be solved.

[0236] After the XY angle γ xy and the actual movement distance ratio ratioXY are obtained, the mechanical XY axis coordinates can be converted to the reference coordinate system. The following content can satisfy the conditions that the XY axes are perpendicular and the actual movement distances are equal when the XY axes are sent equal-length movement instructions.

[0237] 4. Use the ellipse information fitted by the mechanical coordinates of some points when the calibration ball rotates around the C axis when the A axis is in different positions to solve the relevant information of the Z axis.

[0238] The Z-axis related variables derived from the ellipse information are as follows:

[0239] Assume that the XYZ axes send motion instructions of equal length and the motion distances are equal, then the unknown variable to be determined is γ xy (γ), α zx (α), β zy (β)).

[0240] The conversion relationship from the reference coordinate system (x, y, z) to the mechanical coordinate system (x', y', z') is as follows:

[0241] From The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0242]

[0243] Assume the parametric equation of the circle is:

[0244]

[0245] Substituting (7) into (8), we can obtain the corresponding ellipse equation in the mechanical coordinate system:

[0246] Let the equation of the ellipse be make The solution is

[0247]

[0248]

[0249] The above unknown variables include angles α, β, γ, circle radius r, and four unknown quantities.

[0250] Equations can be established

[0251] Observation form, if the angle γ xy =0, the problem is easy to solve.

[0252] If γ xy =0,

[0253] Then from (9)(10)(11)(12) we can get

[0254]

[0255] If the above (1+(tanα) 2+(tanβ) 2 )λ, λtanα, λtanβ, r are unknown quantities, (u1, u2, u3) and (v1, v2, v3) are the major axis vector and minor axis vector of the space ellipse, which can be obtained by fitting the measured data.

[0256] There are 3 equations and 4 unknowns.

[0257] From the front, z=z'λ, originally (1+(tanα) 2 +(tanβ) 2 )γ 2 = 1. However, considering the influence of the pulse equivalent setting (the X and Z axes send the same movement distance instruction, but the actual space movement distance is different), the conversion relationship between the mechanical Z axis and the reference coordinate system Z value is: So we need to convert (1+(tanα) 2 +(tanβ) 2 )γ 2 =k 2 , set as a separate variable.

[0258] At this time, there are 4 variables, and more equations need to be established.

[0259] Because the above variables are the same for all rotating circles, the overdetermined set of equations can be established based on the information of the fitted ellipse when A is at different angles.

[0260] In addition, equation ① in (15) above needs to be discarded. Equation ① requires that the circular vectors corresponding to the ellipse u and v vectors must be perpendicular. In actual calculations, it was found that if this restriction is in place, u and v will have slight fluctuations due to errors, which will have a great impact on the results and may even make no solution possible. After discarding this restriction, the result obtained is very accurate.

[0261] The actual condition required for this step is to use the least square method to fit the ellipse with a series of mechanical coordinates corresponding to the calibration ball rotating around the C axis when the A axis is in different postures. Then, an overdetermined equation can be established based on the major and minor axis vectors of these ellipses, and the mechanical axis Z and XZ can be solved by the overdetermined equation. 参 Angle α between the two planes zx , Z mechanical axis and YZ 参 Angle β between the planes zy , the ratio of the actual moving distance of the X axis to the Z axis is ratioXZ.

[0262] 5. Establish the transformation relationship between the mechanical coordinate system and the reference coordinate system.

[0263] Then, the angle γ between the mechanical axis of Y and the reference axis can be obtained xy , Z mechanical axis and XZ 参 Angle α between the two planeszx , Z mechanical axis and YZ 参 Angle β between the planes zy , and the actual moving distance ratio of the X-axis to the Y-axis when the device sends the same moving distance instruction, the actual moving distance ratio of the X-axis to the Z-axis, the ratioXY. Since (8) and (9) do not take into account the situation where the actual moving distances of different translation axes are different when sending the same moving distance instruction, (8) and (9) need to be adjusted once, and finally

[0264] The conversion relationship from the reference coordinate system (x, y, z) to the mechanical coordinate system (x', y', z') is as follows:

[0265] From The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows:

[0266]

[0267] Formulas (16) and (17) are the relationship between the reference coordinate system and the mechanical coordinate system.

[0268] The above algorithm is based on the following assumptions: high five-axis repeatability and positioning accuracy, and the trajectory of the ball's center rotating about the C-axis forms a well-defined circle in space. After the operation is completed, accurate information can be obtained about the mechanical axis angle and the actual X, Y, and Z axis travel distance ratios. These assumptions are broad and easily met by five-axis machines, making them widely applicable.

[0269] 6. Fit to obtain the spatial position of the AC axis.

[0270] After obtaining all the information about the XYZ axes, the rotation circle of the A-axis in different postures can be obtained in the reference coordinate system. The information about the AC axis can be obtained from the circle information, including a point on the A-axis and the A-axis direction, a point on the C-axis and the C-axis direction, the ratio ka of the actual rotation angle of the A-axis to the change angle of the A-axis mechanical coordinate, and the ratio kc of the actual rotation angle of the C-axis to the change angle of the C-axis mechanical coordinate.

[0271] 7. Implement mechanical calibration

[0272] The reference coordinate system has been established previously, and the relevant information of the XYZ axes and the axis information of the AC axis in the reference coordinate system have been obtained.

[0273] In order to keep the relative position of a specific point on the tool or workpiece in space unchanged, it is necessary to obtain the real-time coordinates of the specific point as the AC axis changes. The process is as follows: Figure 4 As shown:

[0274] ① Get the position and direction of the C-axis before the A-axis rotates;

[0275] 2. The mechanical coordinates of point A are converted into reference coordinates 1.

[0276] 3. Reference coordinates 1 are rotated around C-axis by corresponding angle to obtain reference coordinates 2.

[0277] 4. Reference coordinates 2 are rotated around A-axis by corresponding angle to obtain reference coordinates 3.

[0278] 5. Reference coordinates 3 are converted into mechanical coordinates, which is the output result.

[0279] Preferably, let a mechanical coordinate from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1),

[0280] (a→a1, c→c1, then x1, y1, z1 are calculated), the specific process is as follows:

[0281] a. Obtain the direction v of C-axis when A-axis is a c1 , and a point t c1 on the axis.

[0282] b. The mechanical coordinates of point A are converted into reference coordinates A 参1 (reference coordinates 1).

[0283] c. Rotate A 参1 (reference coordinates 1) around C-axis by (c1-c)kc to obtain A 参2 (reference coordinates 2).

[0284] d. Rotate A 参2 (reference coordinates 2) around A-axis by (a1-a)ka to obtain A 参3 (reference coordinates 3).

[0285] e. Convert A 参3 (reference coordinates 3) into mechanical coordinates, which is A1(x1, y1, z1).

[0286] Four, result inspection.

[0287] Through simulation test, the mechanical axis related information obtained above can achieve high precision. Under the premise of good AC-axis positioning accuracy and positioning accuracy, the calibration accuracy and measurement accuracy are basically consistent. According to the above method, after mechanical calibration, from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1), the relative position of a certain specific point on the tool or workpiece in space is always kept unchanged. For five-axis machine with good positioning accuracy, high precision can be achieved.

[0288] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A mechanical calibration method for a cradle-type five-axis machine based on a laser rangefinder, wherein the cradle-type five-axis machine includes three translation axes (X, Y, and Z) and two rotation axes (A and C); The XYZ axes are the X axis in the horizontal front-to-back direction, the Y axis in the horizontal left-to-right direction, and the Z axis in the vertical up-and-down direction. The AC axis is the A axis rotating around the X axis, and the A value is the mechanical coordinate value of the A axis. The C axis rotates around the Z axis, and the C value is the mechanical coordinate value of the C axis. The mechanical XY axes are the X axis and the Y axis, and the mechanical XY plane is the horizontal plane formed by the X axis and the Y axis. It is characterized in that a reference coordinate system is established with the position of the laser emission at the mechanical coordinate origin as the origin. Due to the error, the mechanical coordinate system is an oblique coordinate system, and the mechanical coordinate data corresponding to the coordinates of the circular trajectory points rotating in the actual space is an ellipse. According to the rotation around the C axis at different A values, the ellipse information of the mechanical coordinate data of multiple points in the mechanical coordinate system is fitted to establish a connection between the mechanical coordinate system and the reference coordinate system, and the position and direction of the AC axis in the reference coordinate system are obtained, which is the basis for realizing five-axis linkage processing. It includes the following steps: Step S100: obtaining the position of the center of the sphere under different postures of the rotating axis; Step S200: Get the geometric information of the circle rotating around the C axis under different A values ​​in the mechanical coordinate system: Get the mechanical coordinates of multiple sphere centers that rotate the C axis at different A axis angles. Let the mechanical coordinates of the sphere center include the mechanical coordinates of the XYZ axis coordXYZ M =[X i ,Y i ,Z i ] T , mechanical coordinates of AC axis coordAC M =[A i ,C i ] T ; Step S300: When the machine plane is nearly parallel to the mechanical XY plane, the machine C axis rotates, and the coordinates of the sphere center in the mechanical coordinate system are obtained at regular intervals. After one rotation, the coordinates of the sphere center at different C values ​​are obtained. The number of coordinates is greater than or equal to 6. An ellipse can be fitted from these coordinates, and the angle γ of the mechanical XY axis can be obtained from the ellipse information. xy And the ratio of the actual moving distance of the X axis to the Y axis ratioXY; Step S400: When the A axis is in different postures, the calibration ball rotates around the C axis to obtain the mechanical coordinates of multiple points, and based on the fitted ellipse, the mechanical Z axis and XZ are obtained. 参 Angle α between the two planes zx , mechanical Z axis and YZ 参 Angle β between the planes zy And the ratio of the actual movement distance between the X axis and the Z axis ratioXZ; Step S500: Considering the situation where the actual moving distances of different translation axes are different when the same movement distance instruction is sent, the conversion relationship between the mechanical coordinate system and the reference coordinate system is corrected and adjusted: The conversion relationship from the reference coordinate system (x, y, z) to the mechanical coordinate system (x', y', z') is as follows: The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows: Where γ is the angle between the mechanical XY axis (γ xy ), that is, the angle between the mechanical Y axis and the Y reference axis of the reference coordinate system; α is the angle between the mechanical Z axis and the XZ reference plane (α zx ), that is, the angle between the mechanical Z axis and the XZ plane of the reference coordinate system; β is the angle between the mechanical Z axis and the YZ reference plane (β zy ), that is, the angle between the mechanical Z axis and the YZ plane of the reference coordinate system; Step S600: Obtaining the position and direction information of the AC axis in the reference coordinate system: Obtain the rotation circle of the A axis at different postures in the reference coordinate system. From the circle information, obtain the AC axis information, including a point on the A axis and the A axis direction, a point on the C axis and the C axis direction, the ratio ka of the actual rotation angle of the A axis to the change angle of the A axis mechanical coordinate, and the ratio kc of the actual rotation angle of the C axis to the change angle of the C axis mechanical coordinate. Step S700: Complete five-axis coordinate calibration.

2. The mechanical calibration method of a cradle-type five-axis machine based on a laser rangefinder according to claim 1, characterized in that: The step S200 includes calibrating the position of the calibration ball in a certain posture: a. The laser is placed on the Z axis, the optimal laser measurement distance is set to d, and the calibration sphere radius is r; b. Align the laser beam with the vertex of the sphere and ensure that the laser distance is close to the optimal measurement distance d. Assume the current machine coordinates are (x, y, z); c. Start from the vertex of an ideal sphere and make a circle every 10 degrees downward. Then, we can get circles of 10 degrees, 20 degrees, 30 degrees, and 40 degrees. Then, we can get corresponding points every 60 degrees on each circle. We can calculate the relative position of all points relative to the vertex (dx j ,dy j ,dz j ), Based on the mechanical coordinates (x, y, z) of the ball vertex, move the ball to all (x+dx j ,y+dy j ,z+dz j ) point, and obtain the corresponding laser distance d j激光 ; d. Let (x+dx j ,y+dy j ,z+dz j +d j激光 ) is the virtual mechanical coordinate of the spherical point. All the obtained virtual mechanical coordinates of the spherical points are fitted to the sphere using the least squares method to obtain the center position of the sphere (centerX1, centerY1, centerZ1). The actual mechanical coordinate position of the sphere center when the laser is aimed at the next time is obtained (centerX1, centerY1, centerZ1-dr). At this time, the laser is more accurately aimed at the center of the sphere, and the distance between the laser and the surface of the sphere is always close to d. e. Move the mechanical coordinates to (centerX1, centerY1, centerZ1-dr) so that the laser is aligned with the center of the ball, and repeat steps b to complete the calibration of the ball position.

3. The mechanical calibration method of a cradle-type five-axis machine based on a laser rangefinder according to claim 2, characterized in that: In step S200, since the final laser ranging at different positions on the spherical surface is different, it will be affected by the linearity of the laser ranging, the inclination of different points on the spherical surface, and the parallelism of the laser and the z-axis. Therefore, the mapping relationship between different points on the spherical surface is also established: Establish the mapping relationship between the ideal mechanical coordinates of each point on the sphere and the virtual mechanical coordinates to obtain the coordinates of the center of the sphere: The following spherical mechanical coordinates are the actual mechanical coordinates (x, y, z) + the virtual mechanical coordinates (0, 0, d) of the spherical point during measurement, and the mapping relationship between different points on the sphere is established: Use a series of virtual mechanical coordinates obtained by measuring a sphere in a certain posture to fit a sphere, and get the center of the sphere (ballX, ballY, ballZ). In the ideal case, get a series of ideal point coordinates on the sphere when the center of the sphere is (ballX, ballY, ballZ); subtract the corresponding ideal point coordinates from the virtual mechanical coordinates to get the mapping difference of the corresponding points (MapX i ,MapY i ,MapZ i ); After the mapping relationship is established, when fitting a sphere, first use the virtual mechanical coordinates on the sphere to subtract the mapping difference corresponding to each point (MapX i ,MapY i ,MapZ i ), get the new virtual coordinates, and then use the new virtual coordinates to fit the sphere to get the coordinates of the sphere center, which are the final coordinates of the sphere center.

4. A cradle-type five-axis machine mechanical calibration method based on a laser rangefinder according to any one of claims 1 to 3, characterized in that: The step S300 includes the following steps: Assume a circle in the XY plane. The circle equation is: x 2 +y 2 =r 2 (1) When the XY plane is roughly parallel to the machine rotation plane, the deviation between the ideal and actual Z axis has little effect on the calculation of XY axis related parameters. In this case, the Z axis is not considered, and the conversion relationship from the mechanical axis to the ideal coordinate system is: The k value is the ratio of the actual moving distance of the X axis to the Y axis, x,y are the coordinates of the reference system, x', y' are the coordinates of the mechanical coordinate system, Substituting x and y into the circle equation (1), we get the ellipse equation with respect to the mechanical coordinates: x’ 2 +2ksinγx’y’+k 2 y′ 2 =r 2 Assume the general equation of an ellipse: Ax 2 +Bxy+Cy 2 +Dx+Ey+1=0 Then: Long axis inclination Axis-length ratio in Substituting formula (5) into formula (3) and formula (4) yields: A spatial ellipse can be fitted from the several mechanical coordinates obtained above. Then the plane where the spatial ellipse is located is rotated to the XY plane. At this time, the major axis inclination angle θ and the major and minor axis ratio a / b of the ellipse in the XY plane can be obtained, and the XY angle γ in the above formulas (6) and (7) can be solved. xy , and the ratio of the actual moving distance between the X axis and the Y axis ratioXY.

5. The mechanical calibration method of a cradle-type five-axis machine based on a laser rangefinder according to claim 4, characterized in that: The step S400 includes the following steps: Assume that the X, Y, and Z axes send motion commands of equal length and move the same distance. The conversion relationship from the reference coordinate system (x, y, z) to the machine coordinate system (x', y', z') is as follows: The transformation relationship from the mechanical coordinate system (x', y', z') to the reference coordinate system (x, y, z) is as follows: Where γ is the angle between the mechanical XY axis (γ xy ), that is, the angle between the mechanical Y axis and the Y reference axis of the reference coordinate system; α is the angle between the mechanical Z axis and the XZ reference plane (α zx ), that is, the angle between the mechanical Z axis and the XZ plane of the reference coordinate system; β is the angle between the mechanical Z axis and the YZ reference plane (β zy ), that is, the angle between the mechanical Z axis and the YZ plane of the reference coordinate system; Let the parametric equation of the circle be: Substituting formula (7) into formula (8), we can obtain the corresponding ellipse equation in the mechanical coordinate system: make The solution is: Set up the equation: Observation form, if the angle γ xy =0, then from formula (9)-formula (12) we can get: If the above (1+(tanα) 2 +(tanβ) 2 )λ 2 , λtanα, λtanβ, r, are unknown quantities, (u1, u2, u3) and (v1, v2, v3) are the major axis vector and minor axis vector of the space ellipse, which can be obtained by fitting the measured data; by z = z'λ, (1 + (tanα) 2 + (tanβ) 2 )γ 2 = 1, Taking into account the influence of the pulse equivalent setting, the conversion relationship between the mechanical Z axis and the Z value of the reference coordinate system is: Therefore, (1+(tanα) 2 +(tanβ) 2 )γ 2 =k 2 Because the above variables are the same for all rotating circles, the overdetermined equations can be established based on the information of the ellipse fitted when A is at different angles; In addition, discard equation ① in formula (15), The calibration ball rotates around the C axis for a circle when the A axis is in different postures, and the ellipse is fitted using the least squares method. Then, an overdetermined equation is established based on the major and minor axis vectors of these ellipses. The mechanical axis Z and the XZ axis can be solved by the overdetermined equation. 参 Angle α between the two planes zx , Z mechanical axis and YZ 参 Angle β between the planes zy , the ratio of the actual moving distance of the X axis to the Z axis is ratioXZ.

6. The mechanical calibration method of a cradle-type five-axis machine based on a laser rangefinder according to claim 1, characterized in that: In step S700, in order to keep the relative position of a specific point on the tool or workpiece in space unchanged, it is necessary to obtain the real-time coordinates of the specific point as it changes with the AC axis. Suppose a certain mechanical coordinate changes from one mechanical coordinate (x, y, z, a, c) to another coordinate (x1, y, 1z1, a1, c1): Step S710: Obtain the direction ν of the C axis when the A axis is a c1 and a point t on the axis c1 ; Step S720: The mechanical coordinates of point A are converted to reference coordinates A 参1 ; Step S730: Set the reference coordinate A 参1 Rotate (c1-c)kc around the C axis to get A 参2 ; Step S740: A 参2 Rotate (a1-a)ka around axis A to get A 参3 ; Step S750: A 参3 Switch to the mechanical coordinate system, which is A1(x1,y1,z1).

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