CN115790383A - Chamfer hole measuring method based on binocular surface structured light and application thereof - Google Patents
Chamfer hole measuring method based on binocular surface structured light and application thereof Download PDFInfo
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- CN115790383A CN115790383A CN202211706325.2A CN202211706325A CN115790383A CN 115790383 A CN115790383 A CN 115790383A CN 202211706325 A CN202211706325 A CN 202211706325A CN 115790383 A CN115790383 A CN 115790383A
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Abstract
The invention discloses a chamfer hole measuring method based on binocular surface structured light, which comprises the steps of synchronously acquiring a two-dimensional image and a point cloud of a chamfer hole by utilizing a sensor, wherein the two-dimensional image comprises a left camera image and a right camera image; respectively acquiring circle center coordinates in the left camera image and the right camera image; constructing a space straight line by using the coordinates of the circle center in the left camera image and the origin of the left camera coordinate system and recording the space straight line as a straight line L1; constructing a space straight line by using the coordinates of the circle center in the right camera image and the origin of the right camera coordinate system and recording the space straight line as a straight line L2; fitting a space plane Q by using the point cloud; the straight lines L1 and L2 are projected onto the spatial plane Q, respectively, and the intersection of the two projected straight lines is recorded as a hole center coordinate. The hole center positioning error of the method is less than 0.2mm, the detection requirement of the precision machining manufacturing industry is met, and the method is suitable for online detection.
Description
Technical Field
The invention relates to the field of visual detection, in particular to a chamfer hole measuring method based on binocular surface structured light and application thereof.
Background
Orifice chamfering (chamfer hole) refers to making a bevel cut in the opening (see fig. 1) for ease of assembly and burr removal. In the precision machining manufacturing industry, holes in a workpiece need to be accurately positioned, and machining position deviation of the holes may cause inaccurate assembly of the workpiece.
Currently, methods for measuring hole characteristics are mainly classified into contact measurement and non-contact measurement.
The contact measurement is measurement by using a three-coordinate measuring machine, the general process is to install a cylinder or a spherical accessory on a chamfer hole and indirectly finish the positioning of the hole by using the three-coordinate measuring machine to measure the ball or the cylinder, and the method has low measurement efficiency and can only perform off-line measurement.
The non-contact measurement is mainly a surface structure light measurement method, and the method comprises the steps of collecting point clouds in a hole area by using a surface structure light sensor, fitting a cylinder and a hole surface point cloud fitting plane by using the point clouds in the inner wall of the hole, and determining the position of a hole center by using the intersection of the axis of the cylinder and the plane. However, the method cannot accurately obtain the position of the chamfer hole, and the main reasons are as follows: chamfer hole is cut on metal machine adds the piece and comes to cutting process has adopted the bright surface cutting, leads to chamfer hole inner wall to demonstrate high reflection characteristic, diffuse reflection relatively poor, and the inner wall point cloud disappearance of gathering is serious, can't effectively fit out the inner wall cylinder through the point cloud. Meanwhile, the method needs to acquire a large amount of point cloud data, is easily influenced by a shooting angle, has poor robustness, has an algorithm error larger than 0.2mm, and cannot meet the measurement requirements of the precision machining and manufacturing industry. Therefore, how to measure the chamfer hole quickly and accurately becomes a problem to be solved urgently.
Disclosure of Invention
Aiming at the problems, the invention provides a method for measuring the chamfer hole of the binocular surface structured light, which is characterized in that the position of the hole center is obtained by utilizing a projection straight line, the method is not easily influenced by point cloud loss of the inner wall of the chamfer hole, the hole center positioning error is less than 0.2mm, the detection requirement of the precision machining and manufacturing industry is met, and the method is suitable for online detection.
The technical scheme is as follows:
a chamfer hole measuring method based on binocular surface structured light is characterized in that a binocular surface structured light sensor is used for synchronously acquiring a two-dimensional image and a point cloud of a chamfer hole, wherein the two-dimensional image comprises a left camera image and a right camera image;
the hole center coordinates of the chamfer holes are obtained by the following steps:
1) Respectively extracting the edge of the chamfer hole from the left camera image and the right camera image and performing edge fitting to obtain the geometric center coordinate of the edge of the chamfer hole, and recording the geometric center coordinate as a circle center coordinate;
constructing a space straight line by using the coordinates of the circle center in the left camera image and the origin of the left camera coordinate system and recording the space straight line as a straight line L1; constructing a space straight line by using the coordinates of the circle center in the right camera image and the origin of the right camera coordinate system and recording the space straight line as a straight line L2;
unifying the straight lines L1 and L2 and the point cloud into the same coordinate system;
fitting a space plane Q by using the point cloud;
2) The straight lines L1 and L2 are projected onto the spatial plane Q, respectively, and the intersection of the two projected straight lines is recorded as a hole center coordinate.
Further, the method for fitting the space plane Q by using the point cloud comprises the following steps:
converting the coordinates of the circle center in the left camera image or the right camera image into a coordinate system where the point cloud is located;
searching point cloud storage within the radius r by taking the converted point as a center; r is 1.3 to 3 times of the theoretical radius of the orifice of the chamfer hole;
the spatial plane Q is fitted with the stored point cloud.
Preferably, in the step 1), an edge ellipse fitting is performed by using a least square method to obtain a major axis and a minor axis of the ellipse, and the intersection point of the major axis and the minor axis is recorded as a circle center coordinate.
Preferably, the method of fitting the spatial plane Q with the point cloud in step 1) is a RANSAC method or a least square method.
And as an application, the hole center coordinate obtained in the step 2) is used as a difference with a theoretical digital-analog hole center coordinate of the chamfer hole, and the machining precision of the chamfer hole is evaluated by using the difference.
Further, when a plurality of chamfer holes to be measured exist in the acquired two-dimensional image and point cloud; respectively framing and selecting an interested area of a single chamfer hole in the two-dimensional image and the point cloud by taking the theoretical hole center position coordinate of each chamfer hole as the center, and obtaining a local two-dimensional image and a local point cloud corresponding to the single chamfer hole to be measured;
and then, respectively utilizing each local two-dimensional image and each local point cloud to carry out the steps 1) and 2), and calculating the hole center of each chamfer hole to be measured.
Preferably, the method of extracting the chamfered hole edge is a canny method or a Sobel method.
The method has the following characteristics:
the method adopts a binocular surface structured light sensor to simultaneously acquire the two-dimensional image and the point cloud, utilizes the original points (0, 0) of the coordinate systems of the left camera and the right camera and the space straight line established by the circle centers on the two-dimensional image to project the straight line to the upper plane of the chamfer hole, and utilizes the projected straight line to acquire the position of the hole center, so that the method is not easily influenced by the point cloud loss on the inner wall of the chamfer hole, can quickly and accurately acquire the coordinates of the hole center, and is suitable for online detection.
The method has the advantages that a large amount of point clouds on the surface of a measured object can be obtained at one time by adopting surface structure light detection, the coverage of a detection area is wide, each chamfer hole area is processed in the whole point cloud, synchronous detection of a plurality of chamfer holes can be realized, point cloud data are processed in parallel, the detection speed is high, and the automation degree is high.
Drawings
FIG. 1 is a schematic cross-sectional view of a chamfered hole;
fig. 2 is a schematic diagram of the positional relationship between the straight lines L1 and L2 and the spatial plane Q.
Detailed Description
The technical scheme of the invention is described in detail in the following with reference to the accompanying drawings and the detailed description.
A method for measuring a chamfer hole based on binocular surface structured light comprises the steps of synchronously acquiring a two-dimensional image and a point cloud of the chamfer hole by using a binocular surface structured light sensor, wherein the two-dimensional image comprises a left camera image and a right camera image;
the hole center coordinates of the chamfer hole (shown in figure 1) are obtained by the following steps:
1) Respectively extracting the edges of the chamfer holes from the left camera image and the right camera image and carrying out edge fitting to obtain the geometric center coordinates of the edges of the chamfer holes, and recording the geometric center coordinates as circle center coordinates;
as a preferred embodiment, the method of extracting the chamfered hole edge is a canny method or a Sobel method.
Constructing a space straight line by using the coordinates of the circle center in the left camera image and the origin of the left camera coordinate system and recording the space straight line as a straight line L1; constructing a space straight line by using the coordinates of the circle center in the right camera image and the origin of the right camera coordinate system and recording the space straight line as a straight line L2;
unifying the straight lines L1 and L2 and the point cloud into the same coordinate system; in specific implementation, the straight lines L1 and L2 and the point cloud are unified into the same coordinate system through internal and external parameters of the left camera and the right camera;
fitting a space plane Q by using the point cloud;
2) The straight lines L1 and L2 are projected onto the spatial plane Q (see fig. 2), respectively, and the intersection of the two projected straight lines is taken as the hole center coordinate.
Specifically, the method for fitting the space plane Q by using the point cloud comprises the following steps:
converting the coordinates of the circle center in the left camera image or the right camera image into a coordinate system where the point cloud is located;
searching point cloud storage within the radius r by taking the converted point as a center; r is 1.3 to 3 times of the theoretical radius of the orifice of the chamfer hole; in the embodiment, the value of r is 1.5 times of the theoretical radius of the orifice of the chamfer hole;
the spatial plane Q is fitted with the stored point cloud. More specifically, the method of fitting the spatial plane Q with the point cloud is the RANSAC method or the least square method.
Because the chamfer holes in the image are stretched and are in an elliptical shape, in the step 1), edge ellipse fitting is carried out by using a least square method to obtain the major axis and the minor axis of the ellipse, and the intersection point of the major axis and the minor axis is recorded as the coordinate of the circle center.
During actual detection, due to the existence of the cutting surface of the chamfer hole and the problem of the shooting angle, two elliptical edges may be fitted in a left camera image/a right camera image (chamfer hole surface image), the inner circle and the outer circle are circular, and the geometric center coordinate of the edge of the inner circle or the geometric center coordinate of the edge of the outer circle is taken and recorded as the circle center coordinate. In this embodiment, the geometric center coordinates of the inner circle edge are taken as the coordinates of the circle center. The inner circle edge point and the outer circle edge point can be distinguished according to the distance between the inner circle edge point and the circle center.
In specific implementation, when a plurality of chamfer holes to be measured exist in the acquired two-dimensional image and point cloud; respectively framing and selecting an interested area of a single chamfer hole in the two-dimensional image and the point cloud by taking the theoretical hole center position coordinate of each chamfer hole as the center, and obtaining a local two-dimensional image and a local point cloud corresponding to the single chamfer hole to be measured;
and respectively carrying out steps 1) and 2) by using each local two-dimensional image and each local point cloud, and calculating the hole center of each chamfer hole to be measured.
The method can realize synchronous detection of a plurality of chamfer holes on the surface of the workpiece, and has high automation degree.
And as an application, the hole center coordinate obtained in the step 2) is used as a difference with a theoretical digital-analog hole center coordinate of the chamfer hole, and the machining precision of the chamfer hole is evaluated by using the difference.
For more intuitive comparison: compared with the traditional method (using point cloud of the inner wall of the hole to fit a cylinder and a point cloud of the surface of the hole to fit a plane, using the intersection of the axis of the cylinder and the plane to determine the position of the center of the hole), the method of the invention carries out a comparison experiment, detects 6 different chamfered holes, respectively detects each chamfered hole by using the method of the invention and the traditional method, compares the detected coordinates of the center of the hole with the coordinates of the center of the hole on a theoretical digital analogy of the chamfered hole, obtains errors, and has the following results:
| chamfer hole | Error/mm of traditional method | Error/mm of the method of the invention |
| 1 | 0.05856 | 0.03356 |
| 2 | 0.110163 | 0.029553 |
| 3 | 0.149344 | 0.031592 |
| 4 | 0.46077 | 0.108961 |
| 5 | 0.257909 | 0.096796 |
| 6 | 0.926759 | 0.108961 |
| Mean error of | 0.3272550833 | 0.068237167 |
As can be seen from the data in the table, the error of the traditional method is obviously higher than that of the method of the invention, and the detection precision of the method is less than 0.2mm, thus meeting the detection precision requirement of the precision machining and manufacturing industry.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable others skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Claims (7)
1. A chamfer hole measuring method based on binocular surface structured light is characterized in that a binocular surface structured light sensor is used for synchronously acquiring a two-dimensional image and a point cloud of a chamfer hole, wherein the two-dimensional image comprises a left camera image and a right camera image;
the hole center coordinates of the chamfer holes are obtained by the following steps:
1) Respectively extracting the edges of the chamfer holes from the left camera image and the right camera image and carrying out edge fitting to obtain the geometric center coordinates of the edges of the chamfer holes, and recording the geometric center coordinates as circle center coordinates;
constructing a space straight line by using the coordinates of the circle center in the left camera image and the origin of the left camera coordinate system and recording the space straight line as a straight line L1; constructing a space straight line by using the coordinates of the circle center in the right camera image and the origin of the right camera coordinate system and recording the space straight line as a straight line L2;
unifying the straight lines L1 and L2 and the point cloud into the same coordinate system;
fitting a space plane Q by using the point cloud;
2) The straight lines L1 and L2 are projected onto the spatial plane Q, respectively, and the intersection of the two projected straight lines is recorded as a hole center coordinate.
2. The binocular surface structured light based chamfer hole measurement method of claim 1, wherein: the method for fitting the space plane Q by using the point cloud comprises the following steps:
converting the coordinates of the circle center in the left camera image or the right camera image into a coordinate system where the point cloud is located;
searching point cloud storage within the radius r by taking the converted point as a center; r is 1.3 to 3 times of the theoretical radius of the orifice of the chamfer hole;
the spatial plane Q is fitted with the stored point cloud.
3. The binocular surface structured light-based chamfer hole measuring method according to claim 1, wherein: in the step 1), performing edge ellipse fitting by using a least square method to obtain a major axis and a minor axis of the ellipse, and recording the intersection point of the major axis and the minor axis as a circle center coordinate.
4. The binocular surface structured light based chamfer hole measurement method of claim 1, wherein: the method for fitting the space plane Q by using the point cloud in the step 1) is a RANSAC method or a least square method.
5. The binocular surface structured light-based chamfer hole measuring method according to claim 1, wherein: and (3) making a difference between the hole center coordinate obtained in the step (2) and the theoretical digital-analog hole center coordinate of the chamfer hole, and evaluating the machining precision of the chamfer hole by using the difference.
6. The binocular surface structured light-based chamfer hole measuring method according to claim 1, wherein: when a plurality of chamfer holes to be measured exist in the collected two-dimensional image and point cloud; respectively framing and selecting an interested area of a single chamfer hole in the two-dimensional image and the point cloud by taking the theoretical hole center position coordinate of each chamfer hole as the center, and obtaining a local two-dimensional image and a local point cloud corresponding to the single chamfer hole to be measured;
and respectively carrying out steps 1) and 2) by using each local two-dimensional image and each local point cloud, and calculating the hole center of each chamfer hole to be measured.
7. The binocular surface structured light-based chamfer hole measuring method according to claim 1, wherein: the method of extracting the chamfered hole edge is the canny method or the Sobel method.
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| CN202211706325.2A CN115790383A (en) | 2022-12-29 | 2022-12-29 | Chamfer hole measuring method based on binocular surface structured light and application thereof |
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| CN202211706325.2A CN115790383A (en) | 2022-12-29 | 2022-12-29 | Chamfer hole measuring method based on binocular surface structured light and application thereof |
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