阅读说明：本技术 基于基准标定板校正位姿的自由曲面测量方法与装置 (Free-form surface measuring method and device based on reference calibration plate correction pose ) 是由 李亚茹 王中宇 程银宝 于 2019-11-14 设计创作，主要内容包括：本发明属于自由曲面测量、机器视觉测量领域,涉及一种基于基准标定板校正位姿的自由曲面测量方法与装置,解决大型自由曲面测量过程中存在的回转工作台回转误差、机械臂空间运动误差和点云拼接基准等问题,可用于提高自由曲面表面形貌的检测精度。本发明通过将被测自由曲面安装在基准标定板表面,在自由曲面测量传感器采集自由曲面表面高度的同时,通过摄像机采集基准标定板的图像,提取基准标定板图像的特征点,从而计算出基准标定板相对于基准标定板摄像机的变换矩阵,进而得到被测自由曲面相对于自由曲面测量传感器之间的位姿变化。解决自由曲面测量过程中存在的回转工作台回转误差和机械臂空间运动误差等问题,为自由曲面多位姿测量提供基准,分离测量过程中的运动误差,实现自由曲面的高精度检测。同时提供被测自由曲面表面高度数据融合和数据拼接的参考基准,从而提高自由曲面的拟合精度。(The invention belongs to the field of free-form surface measurement and machine vision measurement, and relates to a free-form surface measurement method and device for correcting pose based on a reference calibration plate, which solves the problems of rotary error of a rotary worktable, space motion error of a mechanical arm, point cloud splicing reference and the like in the large-scale free-form surface measurement process, and can be used for improving the detection precision of the surface morphology of a free-form surface. According to the invention, the measured free-form surface is arranged on the surface of the reference calibration plate, the camera is used for collecting the image of the reference calibration plate while the free-form surface measuring sensor collects the height of the surface of the free-form surface, and the characteristic points of the image of the reference calibration plate are extracted, so that the transformation matrix of the reference calibration plate relative to the camera of the reference calibration plate is calculated, and the pose change of the measured free-form surface relative to the free-form surface measuring sensor is further obtained. The problems of rotary errors of a rotary worktable, space motion errors of a mechanical arm and the like in the free-form surface measuring process are solved, a reference is provided for free-form surface multi-position measurement, the motion errors in the measuring process are separated, and high-precision detection of the free-form surface is realized. And meanwhile, a reference basis for the surface height data fusion and data splicing of the measured free-form surface is provided, so that the fitting precision of the free-form surface is improved.)

1. The free-form surface measurement method based on the pose correction of the reference calibration plate is characterized by comprising the following steps of:

the method comprises the following steps: installing a free-form surface measuring sensor (6) in the center of an end effector of a mechanical arm (8), installing reference calibration plate cameras (7) at two sides of the end effector of the mechanical arm (8), respectively measuring the pose between the free-form surface measuring sensor (6) and the reference calibration plate cameras (7) through a laser tracker, and calculating to obtain a transformation matrix of the reference calibration plate cameras (7) relative to the free-form surface measuring sensor (6);

step two: the method comprises the following steps of installing a high-precision reference calibration plate (4) on a rotary worktable (3), fixedly installing a measured free-form surface (5) on the surface of the reference calibration plate (4), installing the rotary worktable (3) and a mechanical arm (8) on an optical platform (1), ensuring that the relative pose between the rotary worktable (3) and a base of the mechanical arm (8) is kept unchanged in the measuring process, and simultaneously reducing the influence of random vibration of the earth surface on the measuring process;

step three: acquiring surface height information of a measured free-form surface (5) by using a free-form surface measuring sensor (6), acquiring an image of a reference calibration plate (4) by using a reference calibration plate camera (7), extracting a characteristic angular point of the image of the reference calibration plate (4), calculating the position and posture of the reference calibration plate (4) relative to the reference calibration plate camera (7) at the moment by using an EPnP algorithm, and obtaining a transformation matrix of the reference calibration plate (4) relative to the reference calibration plate camera (7) at the moment;

step four: driving a rotary worktable (3) to rotate through a servo motor (2) or changing the relative pose between a measured free-form surface (5) and a free-form surface measuring sensor (6) through the space motion of a mechanical arm (8), repeating the step three, acquiring the surface height information of the measured free-form surface (5) in different poses by using the free-form surface measuring sensor (6), and simultaneously obtaining a transformation matrix of a reference calibration plate (4) relative to a reference calibration plate camera (7) when the measured free-form surface (5) is in different poses;

step five: carrying out data fusion by using the obtained transformation matrix of the reference calibration plate (4) relative to the reference calibration plate camera (7) in different poses and the rotation angle of the rotary worktable (3), separating errors such as the rotation angle, axial run-out, radial run-out and the like of the rotary worktable (3), and calculating the surface height information of the measured free-form surface (5) in different poses through coordinate transformation to obtain the surface height information of the measured free-form surface (5) in an initial state;

step six: and performing data fusion on the obtained surface information of the measured free-form surface (5) at different poses, fitting the integral surface profile of the measured free-form surface (5), solving a characterization polynomial of the surface profile of the measured free-form surface (5), and realizing high-precision measurement of the free-form surface.

2. The free-form surface measurement method and device based on the reference calibration plate to correct the pose as claimed in claim 1, characterized in that based on the pose correction method of the reference calibration plate (4), the image of the reference calibration plate (4) is collected by the reference calibration plate camera (7), the pose of the reference calibration plate (4) relative to the reference calibration plate camera (7) is calculated, the rotation angle, the axial runout and the radial runout error of the rotary table (3) are separated, a reference is provided for the surface information data fusion of the measured free-form surface (5), and the precision of the surface information data fusion of the measured free-form surface (5) is improved.

3. The free-form surface measurement method based on the reference calibration plate to correct the pose as claimed in claim 1 is characterized in that based on the pose correction method of the reference calibration plate (4), the image of the reference calibration plate (4) is collected through the reference calibration plate camera (7), the pose of the reference calibration plate (4) relative to the reference calibration plate camera (7) is calculated, the space motion error of the mechanical arm (8) is separated, a reference is provided for the surface information data splicing of the measured free-form surface (5), and the accuracy of the surface information data splicing of the measured free-form surface (5) is improved.

4. Free-form surface measuring device based on position appearance is rectified to benchmark calibration plate, its characterized in that includes: the device comprises an optical platform (1), a servo motor (2), a rotary worktable (3), a reference calibration plate (4), a measured free-form surface (5), a free-form surface measuring sensor (6), a reference calibration plate camera (7) and a mechanical arm (8). The measuring device comprises a free-form surface measuring sensor (6), a reference calibration plate camera (7), a high-precision reference calibration plate (4), a rotary worktable (3), a measured free-form surface (5), an optical platform (1), an optical platform (3) and the mechanical arm (8), wherein the free-form surface measuring sensor (6) is arranged in the center of the mechanical arm (8) end actuator, the reference calibration plate camera (7) is arranged on two sides of the mechanical arm (8) end actuator, the rotary worktable (3) and the mechanical arm (8) are arranged on the rotary worktable (3), the relative pose between the rotary worktable (3) and a base of the mechanical arm (8) is kept unchanged in the measuring process, and meanwhile, the influence of random vibration of the earth surface on the measuring process is reduced.

5. The reference mark plate-based pose correction free-form surface measuring apparatus according to claim 4, wherein the pose of the reference mark plate (4) is taken as a reference, an image of the reference mark plate (4) is acquired by the reference mark plate camera (7), the pose of the reference mark plate (4) with respect to the reference mark plate camera (7) is calculated, and a spatial motion error of the rotary table (3) and the robot arm (8) is separated.

6. The free-form surface measurement apparatus for correcting pose based on reference calibration plate according to claim 4, wherein the free-form surface measurement mode of the apparatus comprises: scanning by a rotary worktable (3) and scanning by a mechanical arm (8); the rotary worktable (3) scans and drives the rotary worktable (3) to rotate by using the servo motor (2), changes the relative pose between the measured free-form surface (5) and the free-form surface measuring sensor (6), and realizes the multi-pose surface height data fusion measurement of the free-form surface; the mechanical arm (8) scans and drives the free-form surface measuring sensor (6) to perform spatial motion along a sub-aperture sampling position (9) shown in figure 3 through the mechanical arm (8), the relative pose between the measured free-form surface (5) and the free-form surface measuring sensor (6) is changed, and multi-pose surface height data splicing measurement of the free-form surface is achieved.

Technical Field

The invention belongs to the field of free-form surface measurement and machine vision measurement, relates to a free-form surface measurement method and device for correcting pose based on a reference calibration plate, and solves the problems of rotary error of a rotary worktable, space motion error of a mechanical arm, point cloud splicing reference and the like in the process of measuring a large free-form surface.

Technical Field

The free-form surface is the most complex and frequently encountered surface in engineering, and the shapes of many parts in the departments of aviation, shipbuilding, automobiles, household appliances, mechanical manufacturing and the like, such as the wing of an airplane or the shape of an automobile, the surface of a mold workpiece and the like, are all free-form surfaces. The shape of the free-form surface can be roughly classified into or composed of two types: one is composed of only elementary analytical curved surfaces such as planes, cylindrical surfaces, conical surfaces, spherical surfaces, etc. Most mechanical parts belong to this class. All shape information contained can be fully conveyed and conveyed in a clear manner by drawing geometry and mechanical drawings. The other type of curve surface is a curve surface which cannot be composed of elementary analytical surfaces and can freely change in a complex manner, namely a free curve surface. Such as exterior parts for aircraft, automobiles, and ships. The free-form surface element has the largest degree of freedom of surface appearance, can greatly improve the performance of equipment such as airplanes, automobiles, ships and the like, and has been increasingly emphasized by people in the field of industrial design.

However, the free-form curve surface cannot be clearly defined by drawing geometry and mechanical drawing, higher requirements are provided for design, processing and detection, the difficulty of design and processing of the free-form curve surface is overcome with the increasing maturity of numerical control processing technology, and measurement becomes a bottleneck limiting the wide application of free-form curve surface parts. In-place and on-line visual measurement of free-form surfaces is increasingly emphasized by people, three-dimensional measurement is rapidly and accurately carried out on the free-form surface parts, the production period can be shortened, the feedback can be timely carried out on the production and processing process of products, the processing precision is improved, and the method has a non-replaceable effect on digital manufacturing.

If the traditional three-coordinate measuring machine is adopted for measurement, the defects of low measurement speed, large workload of clamping and measuring and aligning for converting the material object, too few measurement data points, incapability of describing the condition of the material object manufacturing according to the appearance and the like exist. The vision measurement means such as photogrammetry, structured light scanning measurement and the like are novel measurement technologies which are developed rapidly in recent years, have the advantages of high measurement speed, high precision, good field adaptability and the like, and are the preferred method for three-dimensional digital measurement of the free-form surface part. However, when the free-form surface is measured, not only can design element data be required to be rapidly obtained, but also a plurality of problems of large-scale real object data splicing error accumulation, detail description, dark or reflective surface, shallow groove and the like need to be solved, and the high-precision measurement of the free-form surface cannot be realized by a single measurement pose. The free-form surface is arranged on the rotating shaft to rotate or the measuring sensor is arranged on the mechanical arm to move so as to change the relative pose between the measuring sensor and the free-form surface, and then the rotation error of the rotating shaft and the space motion error of the mechanical arm are introduced, so that the measuring reference is changed, and the measuring precision of the free-form surface can be greatly reduced.

The invention provides a free-form surface measuring method and a device for correcting pose based on a reference calibration plate, aiming at the main problem of influencing measuring precision in the existing measuring method.

Disclosure of Invention

The invention aims to: the method and the device for measuring the free-form surface based on the reference calibration plate correction pose overcome the defects of the existing free-form surface detection technology, improve the detection precision of the free-form surface, and provide the method and the device for measuring the free-form surface based on the reference calibration plate correction pose.

The invention belongs to the field of free-form surface measurement, relates to a free-form surface measurement method and device for correcting pose based on a reference calibration plate, and solves the problems of rotary errors of a rotary worktable, space motion errors of a mechanical arm and the like in the free-form surface measurement process.

The technical solution of the invention is as follows: the free-form surface measuring method and device based on the pose correction of the reference calibration plate are realized by the following steps:

the method comprises the following steps: installing a free-form surface measuring sensor in the center of an end effector of the mechanical arm, installing reference calibration plate cameras on two sides of the end effector of the mechanical arm, respectively measuring the poses between the free-form surface measuring sensor and the reference calibration plate cameras through a laser tracker, and calculating to obtain a transformation matrix of the reference calibration plate cameras relative to the free-form surface measuring sensor;

step two: the method comprises the following steps of installing a high-precision reference calibration plate on a rotary worktable, fixedly installing a measured free-form surface on the surface of the reference calibration plate, and installing the rotary worktable and a mechanical arm on an optical platform, so that the relative pose between the rotary worktable and a mechanical arm base is kept unchanged in the measuring process, and the influence of random vibration of the earth surface on the measuring process is reduced;

step three: acquiring surface height information of a measured free-form surface by using a free-form surface measuring sensor, acquiring an image of a reference calibration plate by using a reference calibration plate camera, extracting a characteristic angular point of the image of the reference calibration plate, calculating the pose of the reference calibration plate relative to the reference calibration plate camera at the moment by using an EPnP algorithm, and obtaining a transformation matrix of the reference calibration plate relative to the reference calibration plate camera at the moment;

step four: driving the rotary worktable to rotate through a servo motor or changing the relative pose between the measured free-form surface and the free-form surface measuring sensor through the space motion of the mechanical arm, repeating the step three, acquiring the surface height information of the measured free-form surface at different poses by using the free-form surface measuring sensor, and simultaneously obtaining a transformation matrix of the reference calibration plate relative to the reference calibration plate camera at different poses of the measured free-form surface;

step five: performing data fusion by using the obtained transformation matrix of the reference calibration plate relative to the reference calibration plate camera at different poses and the rotation angle of the rotary worktable, separating errors such as the rotation angle, axial run-out, radial run-out and the like of the rotary worktable or space motion errors of a mechanical arm, and calculating the surface height information of the measured free-form surface at different poses through coordinate transformation to obtain the surface height information of the measured free-form surface at multiple groups of initial poses;

step six: and performing data fusion on the obtained height information of the surface of the measured free-form surface in different poses, fitting the overall surface profile of the measured free-form surface, solving a characterization polynomial of the surface profile of the measured free-form surface, and realizing high-precision measurement of the free-form surface.

The invention relates to a free-form surface measuring device based on a reference calibration plate to correct pose, which comprises: the device comprises an optical platform, a servo motor, a rotary worktable, a reference calibration plate, a measured free-form surface, a free-form surface measuring sensor, a reference calibration plate camera and a mechanical arm. The measuring method comprises the steps of installing a free-form surface measuring sensor in the center of an end effector of a mechanical arm, installing reference calibration plate cameras on two sides of the end effector of the mechanical arm, installing a high-precision reference calibration plate on a rotary worktable, fixedly installing a measured free-form surface on the surface of the reference calibration plate, installing the rotary worktable and the mechanical arm on an optical platform, ensuring that the relative pose between the rotary worktable and a base of the mechanical arm is kept unchanged in the measuring process, and reducing the influence of random vibration of the ground surface on the measuring process.

Drawings

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein the accompanying drawings are included to provide a further understanding of the invention and form a part of this specification, and wherein the illustrated embodiments and descriptions thereof are intended to illustrate and not limit the invention, wherein:

FIG. 1 is a schematic diagram of a free-form surface measurement method and apparatus based on a reference calibration plate to correct pose according to the present invention;

FIG. 2 is a schematic diagram of a spatial sampling position of the free-form surface measurement method and apparatus based on a reference calibration plate to correct pose according to the present invention;

FIG. 3 is a schematic diagram of a reference calibration plate of the free-form surface measurement method and apparatus for correcting pose based on the reference calibration plate according to the present invention;

the reference number in the figure is 1-an optical platform, 2-a servo motor, 3-a rotary worktable, 4-a reference calibration plate, 5-a measured free-form surface, 6-a free-form surface measurement sensor, 7-a reference calibration plate camera, 8-a mechanical arm and 9-a sub-aperture sampling position.

Detailed Description

The invention is further illustrated by the following figures and examples.

The free-form surface measuring method and device based on the reference calibration plate error correction utilize the high-precision reference calibration plate as the reference of the space motion of the rotating shaft and the mechanical arm, correct the motion errors of the rotating shaft and the mechanical arm in real time through the position and posture change of the measurement reference calibration plate, realize the motion error separation in the free-form surface multi-position measurement process, solve the problems of the rotating error of a rotating workbench, the space motion error of the mechanical arm and the like in the free-form surface measurement process, and improve the measurement precision of the free-form surface.