CN113945159B - Bolt diameter measurement method based on contour matching - Google Patents
Bolt diameter measurement method based on contour matching Download PDFInfo
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- CN113945159B CN113945159B CN202111247879.6A CN202111247879A CN113945159B CN 113945159 B CN113945159 B CN 113945159B CN 202111247879 A CN202111247879 A CN 202111247879A CN 113945159 B CN113945159 B CN 113945159B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
- G06T7/13—Edge detection
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
- G06T7/73—Determining position or orientation of objects or cameras using feature-based methods
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10028—Range image; Depth image; 3D point clouds
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30244—Camera pose
Abstract
The invention discloses a bolt diameter measuring method based on contour matching, which simulates a simulated contour mapped on a visible light camera image when a bolt conforming to the drawing size is positioned at a target bolt position according to the bolt position, calibration information of a visible light camera and a depth camera and the rotation angle of the camera relative to the bolt. And dividing the points on the simulated contour into a plurality of areas according to the straight line and the arc line, and calculating the matching degree of the two contours according to the distance information of the pixel points on the simulated contour and the target contour. Performing cyclic traversal on the four dimensions of the x axis, the y axis, the contour plane rotation angle and the drawing bolt diameter of the image pixel plane, calculating the matching degree, and obtaining the drawing bolt diameter corresponding to the simulation contour with the highest matching degree, namely the bolt diameter measurement result. The method has the advantages of small measurement error, high efficiency, no need of strictly placing equipment in a static state, no need of strictly setting shooting distance and angle, remote unmanned non-contact operation, light equipment, quick operation and the like.
Description
Technical Field
The invention relates to a bolt diameter measurement method based on contour matching, and belongs to the field of industrial intelligent measurement.
Background
In the fields of industrial manufacturing, engineering construction and the like, it is often necessary to accurately measure the dimensions of a field bolt, in particular the diameter, in millimeter order. The existing method is mainly divided into two types, wherein the first type is unmanned operation, equipment such as an industrial-level high-precision depth camera or a high-resolution visible light camera with a calibrated position in advance is arranged nearby a measurement target for measurement in advance under the scene of allowing static placement of large-volume measurement equipment, and the second type is manual operation, and a measurement tool is carried manually for measuring the target. However, under some special scenes, the two existing methods are not suitable, such as a railway high-large bridge pier bolt measurement scene, the efficiency is low because repeated climbing is needed during manual operation, meanwhile, potential safety hazards exist, unmanned operation needs to be carried around a target through carrying measuring equipment by unmanned aerial vehicles, unmanned dollies and other carriers for measurement, but the volume of an industrial-level high-precision depth camera capable of realizing millimeter-level accurate measurement is too large to carry flexibly at present, and a small-volume high-resolution visible light camera can be carried, but the requirement that positions are calibrated in advance each time cannot be met. Therefore, there is a need for a method that can achieve high efficiency, low error bolt diameter measurements by an unmanned vehicle carrying a lightweight device.
Disclosure of Invention
The invention aims to provide a bolt diameter measuring method based on contour matching aiming at the defects of the prior art.
The technical scheme for solving the technical problems is as follows: a method for measuring bolt diameter based on contour matching, comprising the following steps:
(1) The generation of the bolt simulation contour comprises the following steps:
(1.1) generating a three-dimensional point cloud conforming to the size of a drawing bolt;
(1.2) acquiring the position of a target bolt by using a depth camera, and moving the generated three-dimensional point cloud to the same position;
(1.3) mapping the moved three-dimensional point cloud onto a visible light camera image to obtain a bolt simulation contour;
(2) The matching degree calculation of the bolt simulation contour and the target contour comprises the following steps:
(2.1) translating the bolt simulation profile to near the target profile;
(2.2) dividing the points on the simulated contour into a plurality of areas according to the straight line and the arc line, and calculating the sum of the nearest distances from each point on the target contour to the simulated contour by the areas, wherein the matching degree is the negative correlation of the total distances;
(3) The cyclic traversal of the bolt simulation profile in four dimensions, including: and performing cyclic traversal on the four dimensions of the x-axis, the y-axis, the profile plane rotation angle and the drawing bolt diameter of the image pixel plane, searching the simulation profile with the highest matching degree, and obtaining the corresponding diameter of the simulation profile as the bolt diameter measurement result.
Further, the step (1.1) includes: and establishing a three-dimensional rectangular coordinate system with a visible light camera as an origin, and generating a point cloud at any position of the coordinate system to form a three-dimensional cylindrical shell which accords with the diameter and the height of the drawing bolt.
Further, the step (1.2) includes: according to the position coordinates of the target bolt in the depth camera point cloud data, the visible light camera, the external parameter matrix marked by the depth camera and the integral shooting rotation angle of the two cameras, the position of the target bolt under the three-dimensional rectangular coordinate system of the visible light camera is calculated, and then the generated cylindrical shell point cloud is moved to the position.
Further, the step (1.3) includes: according to the internal reference matrix marked by the visible light camera, mapping the cylindrical shell point cloud under the three-dimensional rectangular coordinate system of the visible light camera to the pixel coordinate system of the visible light camera image, and obtaining a series of pixel points which are the simulated contours.
Further, in the step (2.1), the bolt simulation contour is translated to the vicinity of the target contour according to the pixel coordinates of the minimum circumscribed rectangle of the target contour.
Further, the step (2.2) includes: dividing the points on the simulated contour into a nine-square lattice according to four boundary points of straight lines and arc line parts, and then calculating the Loss value in a region to reflect the contour matching degree, wherein the Loss value of each region is the sum of the nearest distances from each point on the target contour of the region to the simulated contour, the total Loss is the sum of the Loss values of each region, and the lower the total Loss is, the higher the matching degree is.
In the step (3), firstly, traversing the outline with the highest matching degree by a larger step length, then reducing the step length on the basis of the outline and traversing the outline again, and circulating until the step length is the smallest; and after the circulation is finished, the diameter corresponding to the simulated contour with the highest matching degree is the final bolt diameter measurement result.
The beneficial effects of the invention are as follows: the data obtained by the two measuring devices of the visible light camera and the depth camera are fused and calculated, so that the hardware performance deficiency of the measuring device can be made up, the performance requirement on the device is reduced, the defects of overlarge volume, static placement, advance calibration and the like of the device caused by high-performance equipment are avoided, the portability of the device is realized while the low error is met, and the requirement of unmanned aerial vehicle carrying is met. Meanwhile, the method has no strict requirements on the shooting distance and angle of the equipment, and the diameters of all bolts contained in the data can be measured at the same time according to the data obtained by single shooting, so that the method has the advantages of rapidness and high efficiency.
Drawings
FIG. 1 is a flow chart of a bolt diameter measurement method based on contour matching provided by an embodiment of the invention;
FIG. 2 is a schematic diagram of bolt profile matching calculation according to an embodiment of the present invention, wherein a thick solid line is a target profile, and a thin dotted line is a simulated profile;
fig. 3 is a schematic view of a partition of a bolt simulation profile provided by an embodiment of the present invention.
Detailed Description
The principles and specific implementations of the present invention are described below with reference to the drawings.
The invention provides a bolt diameter measuring method based on contour matching, which can be applied to unmanned accurate measuring scenes of bolt diameters in the fields of industrial manufacture, engineering construction, building construction and the like, as shown in fig. 1, and the specific flow comprises the following steps:
step A: generating a bolt simulation contour;
and (B) step (B): calculating the matching degree of the bolt simulation contour and the target contour;
step C: the bolts simulate a cyclic traversal of the profile in four dimensions.
Further, the step a includes:
and checking whether a pre-condition is met, wherein the pre-condition is that a pair of side-by-side visible light cameras and depth cameras acquire images and point cloud data of a target bolt with a fixed installation angle at an unspecified inclination angle, and bolt profile information in the images and bolt position information in the point cloud are acquired through preprocessing. The performance requirements of the two cameras are related to the final diameter measurement error, taking the bolt error requirement of measuring 40mm diameter as an example, which is less than 1.5 mm, a visible light camera with 1200 ten thousand pixels and a horizontal view angle of 80 degrees can be adopted, the shooting distance is regulated to be 0.8 m to 1.2 m, the included angle between the optical axis of the camera and the central line of the bolt cylinder is regulated to be 45 degrees to 90 degrees, the depth camera can be a model with a ranging error of less than 10 mm and a horizontal view angle of about 80 degrees in the regulated shooting distance range, in addition, the exposure time of the two cameras is generally in microsecond level, and the imaging time difference of the two cameras can be eliminated to a large extent through hardware measurement, so that the camera is allowed to shake with a speed of less than 1 m per second when shooting. The preprocessing is divided into two parts, namely extracting bolt contour information from image data and extracting bolt position information from point cloud data, and the specific method is not included in the invention, and only the format of preprocessing output is required to be defined. Outputting bolt contour information, namely target contour pixel points, calculating a binary image with the same resolution as an original image in advance, wherein the image is obtained by setting 1 pixel point positioned on the target bolt contour in the original image and setting 0 pixel point in the original image on the basis of the original image, then cutting the binary image into a small-size image which only retains the target bolt and the periphery thereof by about one bolt diameter width, and taking the small-size image as an output image. In addition, in order to shorten the calculation time of the subsequent steps, the bolt contour pixel points can be respectively and equally sampled along the x axis and the y axis of the image so as to reduce the data volume. When the bolt position information is output, the bolt position information is a three-dimensional coordinate point under an output point cloud data coordinate system, and the point needs to reasonably reflect the mass center position of an actual target bolt.
After the precondition is met, a three-dimensional space rectangular coordinate system taking a visible light camera as an original point is established, the coordinate system is called as the visible light camera coordinate system for short, a series of points are generated at any position of the coordinate system, and a three-dimensional cylindrical shell which accords with the diameter and the height of a drawing bolt is formed. Then the cylindrical shell needs to be moved to the position where the actual target bolt is located under the visible light camera coordinate system, and the three-dimensional coordinate and the rotation angle of the cylinder are required to be completely consistent with the target bolt. According to the bolt position coordinates in the depth camera point cloud data, the three-dimensional coordinates of the mass center of the target bolt under the depth camera coordinate system can be obtained, according to the visible light camera and the external parameter matrix marked by the depth camera, the conversion relation between the depth camera coordinate system and the visible light camera coordinate system can be obtained, according to the integral shooting rotation angle of the two cameras and the fixed installation angle of the target bolt, the self rotation angle of the target bolt under the depth camera coordinate system can be obtained, the mass center position of the target bolt under the depth camera coordinate system can be converted under the visible light camera coordinate system by integrating the information, the self rotation angle of the target bolt cylinder is determined, and then the cylindrical shell point which is generated under the visible light camera coordinate system is moved to the position of the target bolt and the self rotation with the same angle as the target bolt is executed. And finally, according to an internal reference matrix marked by the visible light camera, mapping cylindrical shell points under a three-dimensional coordinate system of the visible light camera to two-dimensional pixel coordinate systems of the visible light camera image, wherein the obtained series of pixel points are simulated contours.
Further, the step B includes:
and superposing the simulated contour pixel points into an image of the target contour pixel points, and translating the simulated contour to the vicinity of the target contour according to the pixel coordinates of the minimum circumscribed rectangle of the target contour, as shown in fig. 2. Points on the simulated contour are divided into 9 areas according to four boundary points of straight lines and arc line parts, as shown in fig. 3, and then a Loss value is calculated by the areas to reflect the contour matching degree. Regarding target contour points in the areas 1,3,7 and 9, taking the sum of distances from each point to the boundary point between the straight line part and the arc part of the simulated contour in the area where the points are located as Loss1; for the target contour points on areas 2 and 8, taking the sum of the nearest distances from each point to the simulated contour arcs in the areas where the points are located as Loss2; for the target points on areas 4,5,6, the sum of the closest distances of the points to the two straight lines of the simulated contour is taken as Loss3. The distances involved in the calculation of the Loss are all Euclidean distances among the pixel points. The total Loss is the sum of all the partitions, and the lower the Loss is, the higher the matching degree of the simulated contour and the target contour is reflected.
Further, the step C includes:
the bolt simulation outline is circularly traversed in four dimensions of an image pixel plane x-axis, a contour plane y-axis, an outline plane rotation angle and a drawing bolt diameter. The minimum step length of traversing on the x axis and the y axis of the image pixel plane is 1 pixel size, the traversing process is that the pixel points of the simulated contour are integrally translated on the x axis and the y axis, and the traversing range can approximately cover the width of about one bolt radius around the pixel points of the simulated contour; the minimum step length of traversing on the rotation angle of the contour plane is 0.1 degree, the traversing process is to simulate the integral rotation of the contour pixel point on the pixel plane, and the traversing range is plus or minus 3 degrees; and C, traversing the diameter of the drawing bolt by the minimum step length of 0.1 millimeter, wherein the traversing process is to adjust the diameter of the cylindrical shell generated in the step A, then generating new simulated contour pixel points for subsequent calculation, and the traversing range is plus or minus 2 millimeters. In order to reduce the calculated amount in the traversal process, a coarse-to-fine traversal strategy is adopted, namely, a simulated contour with highest matching degree is firstly traversed once by a larger step length, then the step length is reduced on the basis of the contour and then traversed once again, and the process is repeated until the step length is reduced to the minimum step length for the last traversal. The diameter corresponding to the simulated contour with the highest matching degree found in the last traversal is the final bolt diameter measurement result.
The measuring method can achieve high-precision bolt diameter measurement, taking a bolt with a diameter of 40mm as an example, the error is less than 1.5 mm, and the test result is shown in Table 1. Regarding the overall calculation time, taking the camera option described in step A and the processor Ruilong eight kernel R7-4800H as an example, the single bolt calculation time is about 20 seconds.
TABLE 1 bolt diameter measurement test (true diameter 40 mm)
| Bolt numbering | Diameter measurement (mm) |
| 1 | 39.81 |
| 2 | 39.96 |
| 3 | 38.73 |
| 4 | 39.02 |
| 5 | 40.21 |
| 6 | 40.35 |
| 7 | 39.67 |
| 8 | 38.68 |
| 9 | 38.88 |
| 10 | 38.87 |
It can be seen from the above description that the measuring method of the invention uses the position information of the target bolt obtained by the depth camera, combines the relative position relation between the visible light camera and the depth camera and the integral rotation angle of the two cameras and the bolt installation angle, simulates the outline of the bolt with the same size as the drawing bolt at the position of the target bolt on the visible light camera image, namely, the simulated outline, and finds the simulated outline with the highest matching degree with the target outline on the visible light camera image by adjusting the translation, rotation and diameter of the simulated outline, and takes the diameter corresponding to the simulated outline as the final bolt diameter measuring result.
The above-described embodiments are intended to illustrate the present invention, not to limit it, and any modifications and variations made thereto are within the spirit of the invention and the scope of the appended claims.
Claims (5)
1. The bolt diameter measuring method based on contour matching is characterized by comprising the following steps of:
(1) The generation of the bolt simulation contour comprises the following steps:
(1.1) checking whether a pre-condition is satisfied, wherein the pre-condition is that a pair of side-by-side visible light cameras and depth cameras acquire images and point cloud data for a target bolt with a fixed installation angle at an unspecified inclination angle, and bolt profile information in the images and bolt position information in the point cloud are acquired through preprocessing;
(1.2) after the preconditions are met, generating a three-dimensional point cloud conforming to the size of the drawing bolt, comprising: establishing a three-dimensional rectangular coordinate system with a visible light camera as an origin, and generating a point cloud at any position of the coordinate system to form a three-dimensional cylindrical shell which accords with the diameter and the height of a drawing bolt;
(1.3) acquiring a target bolt position by using a depth camera, and moving the generated three-dimensional point cloud to the same position, including: according to the position coordinates of the target bolt in the point cloud data of the depth camera, the visible light camera, the external parameter matrix marked by the depth camera and the integral shooting rotation angle of the two cameras, calculating the position of the target bolt under the three-dimensional rectangular coordinate system of the visible light camera, and then moving the generated cylindrical shell point cloud to the position;
(1.4) mapping the moved three-dimensional point cloud onto a visible light camera image to obtain a bolt simulation contour;
(2) The matching degree calculation of the bolt simulation contour and the target contour comprises the following steps:
(2.1) translating the bolt simulation profile to near the target profile;
(2.2) dividing the points on the simulated contour into a plurality of areas according to the straight line and the arc line, and calculating the sum of the nearest distances from each point on the target contour to the simulated contour by the areas, wherein the matching degree is the negative correlation of the total distances;
(3) The cyclic traversal of the bolt simulation profile in four dimensions, including: and performing cyclic traversal on the four dimensions of the x-axis, the y-axis, the profile plane rotation angle and the drawing bolt diameter of the image pixel plane, searching the simulation profile with the highest matching degree, and obtaining the corresponding diameter of the simulation profile as the bolt diameter measurement result.
2. The method for measuring the diameter of a bolt based on contour matching according to claim 1, wherein said step (1.3) comprises: according to the internal reference matrix marked by the visible light camera, mapping the cylindrical shell point cloud under the three-dimensional rectangular coordinate system of the visible light camera to the pixel coordinate system of the visible light camera image, and obtaining a series of pixel points which are the simulated contours.
3. The method of claim 1, wherein in the step (2.1), the simulated contour of the bolt is translated to the vicinity of the target contour based on the pixel coordinates of the minimum bounding rectangle of the target contour.
4. The method for measuring the diameter of a bolt based on contour matching according to claim 1, wherein said step (2.2) comprises: dividing the points on the simulated contour into a nine-square lattice according to four boundary points of straight lines and arc line parts, and then calculating the Loss value in a region to reflect the contour matching degree, wherein the Loss value of each region is the sum of the nearest distances from each point on the target contour of the region to the simulated contour, the total Loss is the sum of the Loss values of each region, and the lower the total Loss is, the higher the matching degree is.
5. The method for measuring the diameter of the bolt based on contour matching according to claim 1, wherein in the step (3), firstly, a larger step is traversed to find the simulated contour with highest matching degree, then, the step is reduced on the basis of the contour and then traversed again, and the cycle is repeated until the step is the smallest; and after the circulation is finished, the diameter corresponding to the simulated contour with the highest matching degree is the final bolt diameter measurement result.
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