A point cloud calibration and stitching method based on five-axis measurement platform

Abstract

The present invention relates to a point cloud calibration and splicing method based on a five-axis measurement platform. The method comprises the following steps: calibrating the rotation axis of a rotating platform and calculating the axis coordinates of the rotating platform axis in the measuring machine coordinate system; calibrating the rotation axis of a surface laser sensor and calculating the perpendicular distance between the axis and the XOY plane of the sensor coordinate system; and, based on the axis coordinates and perpendicular distance, uniformly converting the collected raw point clouds of all workpiece sub-regions from the sensor coordinate system to the measuring machine coordinate system to complete the splicing. This point cloud calibration and splicing method based on a five-axis measurement platform aims to solve the problem of achieving calibration between the measuring platform coordinate system and the sensor coordinate system, and rapidly splicing point clouds.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional shape measurement, and in particular to a point cloud calibration and splicing method based on a five-axis measurement platform. Background Art

[0002] The rapid development of modern science and technology has driven improvements in production efficiency, new measurement needs, and the development of new measurement technologies. Because contact measurement methods directly contact the workpiece surface, they can easily damage measuring tools. Therefore, non-contact, high-speed, and flexible surface laser measurement methods have emerged.

[0003] However, due to the obstruction of objects, the working distance of the area laser sensor and the surface characteristics of the workpiece being measured, only part of the surface point cloud of the workpiece can be obtained in one acquisition. If the complete point cloud of the workpiece being measured is to be collected, it is necessary to adjust the sensor posture or the workpiece posture so that the sensor can collect point clouds of all sub-areas of the workpiece.

[0004] Therefore, the inventors provide a point cloud calibration and stitching method based on a five-axis measurement platform. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] The embodiment of the present invention provides a point cloud calibration and splicing method based on a five-axis measurement platform, which solves the technical problem of how to achieve calibration between the measurement platform coordinate system and the sensor coordinate system where the workpiece is located and fast splicing of point clouds.

[0007] (2) Technical solution

[0008] The present invention provides a point cloud calibration and splicing method based on a five-axis measurement platform, comprising the following steps:

[0009] Calibrate the rotation axis of the rotating platform and calculate the axis coordinates of the rotating platform axis in the measuring machine coordinate system;

[0010] Calibrate the rotation axis of the area laser sensor and calculate the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system;

[0011] According to the axis coordinates and the vertical distance, the collected original point clouds of all workpiece sub-areas are uniformly converted from the sensor coordinate system to the measuring machine coordinate system to complete the splicing.

[0012] Furthermore, the rotation axis of the calibrated rotating platform is calculated by calculating the axis coordinates of the rotating platform axis in the measuring machine coordinate system, specifically:

[0013] The surface laser sensor is used to collect the surface point cloud of the standard sphere directly above the standard sphere located at the center of the rotating platform, and the center of the fitted standard sphere is calculated. The axis coordinates of the axis of the rotating platform in the measuring machine coordinate system are determined based on the center of the standard ball; wherein, the center of the standard ball is located on the rotation axis of the rotating platform.

[0014] Furthermore, the method of using the surface laser sensor to collect a surface point cloud of the standard sphere located directly above the standard sphere at the center of the rotating platform, calculating the center of the fitted standard sphere, and determining the axis coordinates of the axis of the rotating platform in the measuring machine coordinate system based on the center of the standard sphere specifically includes the following steps:

[0015] Move the surface laser sensor to the position directly above the rotating platform using a three-dimensional coordinate measuring machine, and rotate the sensor's rotation axis to the 0 degree position;

[0016] Rotating the rotating platform by 0 degrees, 120 degrees, and 240 degrees respectively, and collecting surface point clouds of the standard sphere;

[0017] Use the RANSAC algorithm to fit the center coordinates of the three balls respectively;

[0018] Calculate the center of the circle formed by the centers of the three spheres.

[0019] Furthermore, the calculating the center of the circle formed by the centers of the three balls specifically includes the following steps:

[0020] Determine the two-dimensional coordinates of the sphere centers fitted from the three spherical point clouds on the XOY plane of the sensor measurement coordinate system;

[0021] The coordinates of the center of the axis on the XOY plane of the sensor measurement coordinate system are determined based on the three two-dimensional coordinates.

[0022] Furthermore, the sensor measurement coordinate system XOY plane is parallel to the measuring machine coordinate system XOY plane, wherein the measuring machine coordinate system XOY plane is a rotating platform coordinate system.

[0023] Furthermore, the calibration of the rotation axis of the area laser sensor and the calculation of the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system specifically include the following steps:

[0024] Keeping the surface laser sensor directly above the rotating platform, with the rotation axis of the rotating sensor at 0 degrees, collecting the surface point cloud of the standard sphere and fitting the first sphere center coordinates;

[0025] The surface laser sensor is moved in the Y direction and the Z direction along the positive direction of the Y axis and the negative direction of the Z axis of the three-dimensional coordinate measuring machine respectively, and the sensor rotation axis is rotated at a set angle to collect the surface point cloud of the standard sphere and fit the coordinates of the second sphere center;

[0026] According to the Y-direction distance, the Z-direction distance and the set angle, the vertical distance between the sensor rotation axis and the XOY plane of the sensor coordinate system is calculated using geometric principles and trigonometric theorems.

[0027] Furthermore, the calculation of the vertical distance between the sensor rotation axis and the XOY plane of the sensor coordinate system based on the Y-direction distance, the Z-direction distance, and the set angle using geometric principles and trigonometric theorems specifically includes the following steps:

[0028] On the YOZ plane of the sensor coordinate system, the first sphere center O C The coordinates of (y a ,z a ), the second sphere center coordinate is (y b ,z b ), the axis points are A and B respectively, and the vertical distance between the sensor coordinate zero point and the sensor rotation axis is d;

[0029] The Y-axis distance and Z-axis distance of the rotation axis of the two acquisition positions are y′ and z′ respectively. Point N is the position after A moves y′ along the Y-axis and before it moves z′ along the Z-axis.

[0030] From O C Draw two lines Oz a and the straight line Oz b Parallel straight lines intersect the straight line Oy′ at points P and Q respectively;

[0031] Line segment O b B extends along the positive direction of the Z axis of the sensor coordinate system and intersects with the straight line Oy′ at point M. The distance between points QM is y p , from point Q to line segment O b Draw a perpendicular line to the line where B is located, and intersect it at point F;.

[0032] According to the principles of geometry and trigonometric theorems, we can get ΔO C PQ is a right triangle;

[0033] According to the right triangle, the vertical distance d is calculated by the tangent theorem.

[0034] Furthermore, the step of uniformly converting the collected original point clouds of all sub-areas of the workpiece from the sensor coordinate system to the measuring machine coordinate system based on the axis coordinates and the vertical distance specifically includes the following steps:

[0035] Move the point cloud by a distance d along the negative Z-axis of the sensor coordinate system, rotate it clockwise around the X-axis of the coordinate system by α degrees, and move it by a corresponding distance along the positive X-axis, Y-axis, and Z-axis.

[0036] Move the point cloud to the top of the axis of the rotating platform in the coordinate system of the measuring machine, and rotate it counterclockwise around the Z axis by γ degrees;

[0037] The zero point position of the point cloud coordinate system is translated from the axis of the rotating platform to the zero point position of the measuring machine coordinate system.

[0038] Furthermore, the original point clouds of all sub-areas of the workpiece collected are uniformly converted from the sensor coordinate system to the measuring machine coordinate system based on the axis coordinates and the vertical distance to complete the splicing, which specifically includes the following steps:

[0039] Move the collected point cloud along the negative direction of the Z axis of the sensor coordinate system by a distance d to obtain a first translation matrix;

[0040] Rotate α degrees clockwise around the X-axis of the coordinate system to obtain the first rotation matrix;

[0041] Assume that the distance between the sensor position of the current acquisition and the sensor position of the first acquisition in the coordinate system of the measuring machine is x, y, and z, and the point cloud is moved by x′, y′, and z′ along the positive direction of the X-axis, Y-axis, and Z-axis, respectively, to obtain the second translation matrix;

[0042] Move the point cloud to the top of the axis of the rotating platform in the coordinate system of the measuring machine. Assume that the coordinates of the sensor zero point on the three-coordinate motion platform during the first acquisition are (x0, y0, z0), and the coordinates of a point on the axis of the rotating platform are (x c ,y c ,z c ), obtain the third translation matrix;

[0043] Assume that the clockwise rotation angle of the workpiece point cloud collected this time around the axis of the rotating platform is γ, then the point cloud should be rotated counterclockwise around the coordinate Z axis by γ to obtain the second rotation matrix;

[0044] translating the zero point position of the point cloud coordinate system from the axis of the rotating platform to the zero point position of the measuring machine coordinate system to obtain a fourth translation matrix;

[0045] determining a transformation matrix according to the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix, and the fourth translation matrix;

[0046] The original point clouds of all workpiece sub-areas are multiplied by the transformation matrix and unified into the coordinate system of the measuring machine to complete the splicing.

[0047] Furthermore, the transformation matrix is the product of the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix and the fourth translation matrix.

[0048] (3) Beneficial effects

[0049] In summary, this method uses the calibration values of the rotating platform and sensor axes to transform the collected raw point cloud from the sensor coordinate system to the CMM coordinate system, thereby achieving point cloud splicing. This method is simple to operate and can quickly calibrate the measurement platform and sensor coordinate systems, allowing each sub-region of the workpiece to be unified under the same coordinate system, enabling rapid acquisition of the complete workpiece surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0051] Figure 1 1 is a flow chart of a point cloud calibration and stitching method based on a five-axis measurement platform provided by an embodiment of the present invention;

[0052] Figure 2 This is a schematic diagram of a rotary platform axis calibration provided by an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of calibrating the vertical distance between the XOY plane of a sensor coordinate system and the sensor rotation axis provided by an embodiment of the present invention;

[0054] Figure 4 It is a flowchart of a point cloud coordinate system conversion method provided by an embodiment of the present invention.

[0055] In the picture:

[0056] 1-rotating platform; 2-standard ball; 3-center of standard ball; 4-axis of rotating platform. DETAILED DESCRIPTION

[0057] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are intended to illustrate the principles of the present invention and are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments and covers any modifications, replacements, and improvements to the parts, components, and connection methods without departing from the spirit of the present invention.

[0058] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0059] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0060] Figure 1 1 is a flow chart of a point cloud calibration and stitching method based on a five-axis measurement platform provided by an embodiment of the present invention. The method may include the following steps:

[0061] S100, calibrating the rotation axis of the rotating platform, and calculating the axis coordinates of the rotating platform axis in the measuring machine coordinate system;

[0062] S200, calibrating the rotation axis of the area laser sensor, and calculating the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system;

[0063] S300: Based on the axis coordinates and vertical distances, the original point clouds of all sub-areas of the workpiece collected are uniformly converted from the sensor coordinate system to the measuring machine coordinate system to complete the stitching.

[0064] In the above implementation, the coordinates of the collected raw point cloud are transformed from the sensor coordinate system to the CMM coordinate system using the calibration values of the rotational axes of the rotating platform and the sensor, thereby achieving point cloud splicing. This method is simple to operate and can quickly complete the calibration of the measurement platform coordinate system and the sensor coordinate system, allowing each sub-region of the workpiece to be unified in the same coordinate system, realizing the function of quickly acquiring the complete workpiece surface.

[0065] As an optional implementation, step S100 is to calibrate the rotation axis of the rotating platform and calculate the axis coordinates of the rotating platform axis in the measuring machine coordinate system, specifically:

[0066] A surface laser sensor is used to collect the surface point cloud of the standard sphere located directly above the standard sphere at the center of the rotating platform, and the center of the fitted standard sphere is calculated. The axis coordinates of the rotating platform axis in the measuring machine coordinate system are determined based on the center of the standard sphere; among them, the center of the standard ball is located on the rotation axis of the rotating platform.

[0067] Specifically, let the sensor measurement coordinate system XOY plane be XOY S , the XOY plane of the measuring machine coordinate system is XOY U , XOY S With the rotating platform, that is, the measuring machine coordinate system XOY UParallel: The X-axis, Y-axis, and Z-axis directions of the sensor measurement coordinate system are respectively the same as and parallel to the X-axis, Y-axis, and Z-axis directions of the measuring machine coordinate system.

[0068] As an optional implementation, in step S100, a surface laser sensor is used to collect a surface point cloud of a standard sphere located directly above the standard sphere at the center of the rotating platform, and the center of the fitted standard sphere is calculated. The axis coordinates of the rotating platform axis in the measuring machine coordinate system are determined based on the center of the standard sphere. Specifically, the steps include:

[0069] S101. Move the surface laser sensor to the top of the rotating platform through the three-dimensional coordinate measuring machine, and rotate the sensor's rotation axis to the 0 degree position;

[0070] S102, rotating the rotating platform by 0 degrees, 120 degrees, and 240 degrees respectively, and collecting the surface point cloud of the standard sphere;

[0071] S103, using the RANSAC algorithm to fit the center coordinates of the three balls respectively;

[0072] S104. Calculate the center of the circle formed by the centers of the three balls.

[0073] Specifically, the center of the standard ball is at XOY U The movement will form a circle with the axis of the rotating platform as the center. Figure 2 As shown, 1 represents the rotating platform, 2 represents the circle formed by the standard sphere when viewed from above, 3 represents the center of the standard sphere, and 4 represents the center of the circle formed by the center of the standard sphere after the rotating platform rotates three times.

[0074] As an optional implementation, in step S104, calculating the center of the circle formed by the centers of the three balls specifically includes the following steps:

[0075] S1041, respectively determine the two-dimensional coordinates of the sphere centers obtained by fitting the three spherical point clouds on the XOY plane of the sensor measurement coordinate system;

[0076] S1042. Determine the center coordinates of the axis on the XOY plane of the sensor measurement coordinate system based on the three two-dimensional coordinates.

[0077] Specifically, suppose the sphere center obtained by fitting the three spherical point clouds collected by the sensor is at XOY S The coordinates on are (x1, y1), (x2, y2), and (x3, y3), then the formula for the circle formed by these three points is as follows:

[0078]

[0079] By calculating the equation group, we can get the coordinates of the center of the axis on XOYS (x S ,y S ),in:

[0080]

[0081] Assume that the calibration values of the coordinate measuring machine on the X-axis and Y-axis are x U 、y U , then the axis of the rotating platform is at XOY U The coordinates (x C ,y C )=(x S +x U ,y S +y U ), the axis direction is the positive direction of the Z axis.

[0082] As an optional implementation, in step S200, calibrating the rotation axis of the area laser sensor and calculating the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system specifically includes the following steps:

[0083] S201, keep the surface laser sensor directly above the rotating platform, keep the rotation axis of the rotation sensor at 0 degrees, collect the surface point cloud of the standard sphere and fit the first sphere center coordinates;

[0084] S202, moving the surface laser sensor along the Y-axis positive direction and the Z-axis negative direction of the three-dimensional coordinate measuring machine by a Y distance and a Z distance, rotating the sensor rotation axis by a set angle, collecting a point cloud on the surface of the standard sphere and fitting the coordinates of the second sphere center;

[0085] S203 , based on the Y-direction distance, the Z-direction distance, and the set angle, use geometric principles and trigonometric theorems to calculate the vertical distance between the sensor rotation axis and the XOY plane of the sensor coordinate system.

[0086] As an optional implementation, in step S203, the vertical distance between the sensor rotation axis and the XOY plane of the sensor coordinate system is calculated based on the Y-direction distance, the Z-direction distance, and the set angle using geometric principles and trigonometric theorems, specifically including the following steps:

[0087] S2031, set on the YOZ plane of the sensor coordinate system, the first sphere center O C The coordinates of (y a ,z a ), the coordinates of the second sphere center are (y b ,z b ), the axis points are A and B respectively, and the vertical distance between the sensor coordinate zero point and the sensor rotation axis is d;

[0088] S2032. The distances along the Y axis and the Z axis between the rotation axes of the two acquisition positions are y′ and z′ respectively. Point N is the position after point A moves y′ along the Y axis and before it moves z′ along the Z axis.

[0089] S2033, from O C Draw two lines Oz a and the straight line Oz b Parallel straight lines intersect the straight line Oy′ at points P and Q respectively;

[0090] S2034, line segment O b B extends along the positive direction of the Z axis of the sensor coordinate system and intersects with the straight line Oy′ at point M. The distance between points QM is y p , from point Q to line segment O b Draw a perpendicular line to the line B, intersecting it at point F;

[0091] S2035. According to geometric principles and trigonometric theorems, we can get ΔO C PQ is a right triangle;

[0092] S2036. Based on the right triangle, calculate the vertical distance d using the tangent theorem.

[0093] Specifically, if Figure 3 As shown, according to the geometric principles and trigonometric theorems, we can get ΔO C PQ is a right triangle, ∠FQM=∠PO C Q = ∠NBM = θ, line segment PQ = y′ + NM - QM, line segment QF = y b From the tangent theorem, we know that The following formula can be listed:

[0094]

[0095] Solving the above system of equations yields:

[0096]

[0097] This completes the calibration of the sensor's rotation axis position.

[0098] As an optional implementation, in step S300, the original point clouds of all sub-areas of the workpiece collected are uniformly converted from the sensor coordinate system to the measuring machine coordinate system based on the axis coordinates and the vertical distance, such as Figure 4 As shown, the specific steps include:

[0099] S301, moving the point cloud along the negative direction of the Z axis of the sensor coordinate system by a distance d;

[0100] S302, rotate α degrees clockwise around the X-axis of the coordinate system;

[0101] S303, moving a corresponding distance along the positive direction of the X-axis, Y-axis, and Z-axis;

[0102] S304, moving the point cloud to above the axis of the rotating platform in the coordinate system of the measuring machine, and rotating it counterclockwise around the coordinate Z axis by γ degrees;

[0103] S305: Translate the zero point of the point cloud coordinate system from the axis of the rotating platform to the zero point of the measuring machine coordinate system.

[0104] As an optional implementation, the original point clouds of all sub-areas of the workpiece are uniformly converted from the sensor coordinate system to the CMM coordinate system based on the axis coordinates and vertical distances to complete the stitching. The specific steps include:

[0105] Move the collected point cloud along the negative direction of the Z axis of the sensor coordinate system by a distance d to obtain a first translation matrix;

[0106] Rotate α degrees clockwise around the X-axis of the coordinate system to obtain the first rotation matrix;

[0107] Assume that the distance between the sensor position of the current acquisition and the sensor position of the first acquisition in the coordinate system of the measuring machine is x, y, and z. Move the point cloud along the positive direction of the X-axis, Y-axis, and Z-axis by x′, y′, and z′ respectively to obtain the second translation matrix.

[0108] Move the point cloud to the top of the axis of the rotating platform in the coordinate system of the measuring machine. Assume that the coordinates of the sensor zero point on the three-coordinate motion platform during the first acquisition are (x0, y0, z0), and the coordinates of a point on the axis of the rotating platform are (x C ,y C ,z C ), obtain the third translation matrix;

[0109] Assume that the clockwise rotation angle of the workpiece point cloud collected this time around the axis of the rotating platform is γ, then the point cloud should be rotated counterclockwise around the coordinate Z axis by γ to obtain the second rotation matrix;

[0110] The zero point position of the point cloud coordinate system is translated from the axis of the rotating platform to the zero point position of the measuring machine coordinate system to obtain the fourth translation matrix;

[0111] Determine a transformation matrix based on the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix, and the fourth translation matrix;

[0112] Multiply the original point clouds of all workpiece sub-areas by the transformation matrix, unify them into the CMM coordinate system, and complete the stitching.

[0113] In the above embodiment, the first translation matrix T d for:

[0114] The first rotation matrix R x (θ) is:

[0115]

[0116] The second translation matrix T u for:

[0117]

[0118] The third translation matrix T c for:

[0119]

[0120] The second rotation matrix R z (γ) is:

[0121]

[0122] The fourth translation matrix T o for:

[0123]

[0124] As an optional implementation, the transformation matrix is the product of the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix and the fourth translation matrix.

[0125] Specifically, the translation and rotation transformation matrix R F For: R F =T d ·R x (θ)·T u ·T c ·R z (γ)·T o , compare the original point clouds of all workpiece sub-areas with R F Multiply and unify them into the coordinate system of the measuring machine to complete the splicing.

[0126] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and technologies are omitted here.

[0127] The above are merely embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A point cloud calibration and splicing method based on a five-axis measurement platform, characterized in that: The method comprises the following steps: Calibrate the rotation axis of the rotating platform and calculate the axis coordinates of the rotating platform axis in the measuring machine coordinate system; Calibrate the rotation axis of the area laser sensor and calculate the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system; According to the axis coordinates and the vertical distance, the original point clouds of all sub-areas of the workpiece collected are uniformly converted from the sensor coordinate system to the measuring machine coordinate system to complete the splicing; The calibration of the rotation axis of the area laser sensor and the calculation of the vertical distance between the rotation axis of the area laser sensor and the XOY plane of the sensor coordinate system specifically include the following steps: Keeping the surface laser sensor directly above the rotating platform, with the rotation axis of the rotating sensor at 0 degrees, collecting the surface point cloud of the standard sphere and fitting the first sphere center coordinates; The surface laser sensor is moved in the Y direction and the Z direction respectively along the positive direction of the Y axis and the negative direction of the Z axis of the measuring machine coordinate system of the three-dimensional coordinate measuring machine, and the sensor rotation axis is rotated by a set angle to collect the surface point cloud of the standard sphere and fit the coordinates of the second sphere center; On the YOZ plane of the sensor coordinate system, the first sphere center The coordinates are , the coordinates of the second sphere center are , the axis points of the sensor rotation axis are A and B , the vertical distance between the zero point of the sensor coordinate system and the sensor rotation axis is d ; The distances of the sensor's rotation axis in the Y-axis direction and the Z-axis direction in the sensor coordinate system when collecting the point cloud of the standard sphere surface twice are respectively y´ and z´ , N Point A Move along the Y axis Then, move along the Z axis Front position; from Draw two lines O a and straight lines O b Parallel straight lines, respectively A The straight line parallel to the Y-axis direction of the sensor coordinate system intersects at P Point and Q point; O a Point is the zero point of the sensor coordinate system when the sensor rotation axis maintains the 0 degree position. O b Point is the coordinate zero point of the sensor coordinate system after the sensor rotation axis rotates by the set angle; Line segment Extend along the positive direction of the Z axis of the sensor coordinate system, A The straight line parallel to the Y-axis direction of the sensor coordinate system intersects at M point, QM The distance between the two points is ,from Q Point-to-point line segment Draw a perpendicular line to the straight line and intersect it at F point; According to the principles of geometry and trigonometric theorems, we can get Δ O C PQ is a right triangle; According to the right triangle, the vertical distance is calculated by the tangent theorem d .

2. The point cloud calibration and splicing method based on the five-axis measurement platform according to claim 1 is characterized in that: The rotation axis of the calibrated rotating platform is calculated by calculating the axis coordinates of the rotating platform axis in the measuring machine coordinate system, specifically: The surface laser sensor is used to collect the surface point cloud of the standard sphere directly above the standard sphere located at the center of the rotating platform, and the center of the fitted standard sphere is calculated. The axis coordinates of the axis of the rotating platform in the measuring machine coordinate system are determined based on the center of the standard ball; wherein, the center of the standard ball is located on the rotation axis of the rotating platform.

3. The point cloud calibration and splicing method based on the five-axis measurement platform according to claim 2 is characterized in that: The method of using the surface laser sensor to collect a surface point cloud of the standard sphere located directly above the standard sphere at the center of the rotating platform, calculating the center of the fitted standard sphere, and determining the axis coordinates of the axis of the rotating platform in the measuring machine coordinate system based on the center of the standard sphere specifically includes the following steps: Move the surface laser sensor to the position directly above the rotating platform using a three-dimensional coordinate measuring machine, and rotate the sensor's rotation axis to the 0 degree position; Rotating the rotating platform by 0 degrees, 120 degrees, and 240 degrees respectively, and collecting surface point clouds of the standard sphere; Use the RANSAC algorithm to fit the center coordinates of the three balls respectively; Calculate the center of the circle formed by the centers of the three spheres.

4. The point cloud calibration and splicing method based on the five-axis measurement platform according to claim 3 is characterized in that: Calculating the center of the circle formed by the centers of the three balls specifically includes the following steps: Determine the two-dimensional coordinates of the sphere centers of the three spherical point clouds fitted on the XOY plane of the sensor coordinate system; The coordinates of the center of the axis on the XOY plane of the sensor coordinate system are determined based on the three two-dimensional coordinates.

5. The point cloud calibration and stitching method based on the five-axis measurement platform according to claim 3 is characterized in that: The sensor coordinate system XOY plane is parallel to the measuring machine coordinate system XOY plane, wherein the measuring machine coordinate system XOY plane is a rotating platform coordinate system.

6. The point cloud calibration and stitching method based on a five-axis measurement platform according to claim 1, characterized in that: The step of uniformly converting the collected original point clouds of all sub-areas of the workpiece from the sensor coordinate system to the measuring machine coordinate system based on the axis coordinates and the vertical distance specifically includes the following steps: Move the point cloud along the negative direction of the Z axis of the sensor coordinate system d , rotates clockwise around the X axis of the sensor coordinate system α Degrees, move the corresponding distance along the positive direction of the X-axis, Y-axis, and Z-axis of the sensor coordinate system; Move the point cloud above the axis of the rotating platform in the measuring machine coordinate system and rotate it counterclockwise around the Z axis of the measuring machine coordinate system γ Spend; The coordinate zero point position of the point cloud coordinate system is translated from the axis of the rotating platform to the coordinate zero point position of the measuring machine coordinate system.

7. The point cloud calibration and stitching method based on a five-axis measurement platform according to claim 6, characterized in that: The step of converting the collected original point clouds of all sub-areas of the workpiece from the sensor coordinate system to the measuring machine coordinate system based on the axis coordinates and the vertical distance to complete the splicing specifically includes the following steps: Move the collected point cloud along the negative direction of the Z axis of the sensor coordinate system d , get the first translation matrix; Clockwise rotation around the sensor coordinate system X axis α Degrees, get the first rotation matrix; Assume that the distance between the sensor position collected this time and the sensor position collected for the first time in the measuring machine coordinate system is x 、 y 、 z , move the point cloud along the positive direction of the X-axis, Y-axis, and Z-axis of the sensor coordinate system x´ 、 y´ 、 z´ , get the second translation matrix; Move the point cloud to the top of the axis of the rotating platform in the coordinate system of the measuring machine. Assume that the coordinate zero point of the sensor coordinate system at the time of the first acquisition on the three-coordinate motion platform is ( x 0, y 0, z 0), the coordinates of a point on the axis of the rotating platform are ( x c , y c , z c ), get the third translation matrix; Assume that the clockwise rotation angle of the workpiece point cloud collected this time around the axis of the rotating platform is γ , then the point cloud should rotate counterclockwise around the coordinate Z axis γ , get the second rotation matrix; The coordinate zero point position of the point cloud coordinate system is translated from the axis of the rotating platform to the coordinate zero point position of the measuring machine coordinate system to obtain a fourth translation matrix; determining a transformation matrix according to the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix, and the fourth translation matrix; The original point clouds of all workpiece sub-areas are multiplied by the transformation matrix and unified into the coordinate system of the measuring machine to complete the splicing.

8. The point cloud calibration and stitching method based on a five-axis measurement platform according to claim 7, characterized in that: The transformation matrix is the product of the first translation matrix, the first rotation matrix, the second translation matrix, the third translation matrix, the second rotation matrix and the fourth translation matrix.

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