CN113588654B - Three-dimensional visual detection method for engine heat exchanger interface - Google Patents
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Abstract
The invention discloses a three-dimensional visual detection method of an engine heat exchanger interface, which is characterized in that a calibrated camera shoots images of standard heat exchanger parts from a plurality of preset acquisition angles and positions with equal viewing distances, binarization processing is carried out, the images after the binarization processing are detected, the foreground and the background are segmented by edges, the edges after error expansion are calculated as characteristic parameters, repeated operation is carried out on the parts to be compared, and the parts to be compared are compared with the characteristic parameters of the standard parts, so that the parts with various defects are screened; the method has the advantages that all parts can be detected one by one quickly and efficiently by the detection method, the classification effect is good, the production efficiency can be greatly improved, and the qualification rate of the parts leaving the factory is obviously improved.
Description
Technical Field
The invention belongs to the field of part defect detection, and particularly relates to a three-dimensional visual detection method for an engine heat exchanger interface.
Background
In the production process of the heat exchanger, the produced heat exchanger is limited by various conditions, and certain defects exist in the produced heat exchanger, such as the problems of angle deviation between the central axis of the heat exchanger input tube and the standard central axis, surface deformation of the heat exchanger input tube, error size of the heat exchanger input tube and the like, and the defects seriously affect the surface quality and the physical and mechanical properties of the product, and finally, the whole part may be disqualified.
At present, the quality detection link of a factory mostly adopts manual detection or off-line sampling detection, and the subjective detection method is to manually measure the finished product or the semi-finished product of the heat exchanger by aid of auxiliary tools such as vernier calipers, and the method is flexible, but has strong dependence on the working capacity and fatigue degree of workers, has the defects of low efficiency, low precision, poor stability and the like, and the labor cost of manual detection occupies a considerable proportion in the production cost, so that great difficulty is brought to the cost control of enterprises; while the off-line sampling detection can obtain high-precision detection data, the off-line sampling detection has the defects of slow reaction, low efficiency, small sampling coverage and the like, and the defects of the heat exchanger are difficult to discover in time.
Disclosure of Invention
The invention aims to provide a three-dimensional visual detection method for an engine heat exchanger interface, which is efficient and flexible in detection process and accurate in detection result.
The technical scheme adopted for solving the technical problems is as follows: a three-dimensional visual inspection method for an engine heat exchanger interface, comprising the steps of:
step 1): calibrating the internal parameters and the external parameters of the camera through a calibration plate to obtain a calibrated camera;
step 2): obtaining images with a plurality of preset acquisition angles and equal viewing distances of a standard heat exchanger through a calibrated camera, dividing an image corresponding to an input tube of the standard heat exchanger in each image with the acquisition angles into standard images corresponding to the acquisition angles, performing image binarization processing on the standard images to obtain standard images subjected to the image binarization processing, and extracting image characteristic parameters of the standard images subjected to the image binarization processing to serve as standard characteristic parameters;
step 3): acquiring images of a plurality of preset acquisition angles of a heat exchanger to be compared through a calibrated camera, dividing an image corresponding to an input tube of the heat exchanger to be compared in the images of each acquisition angle to serve as an image to be compared, performing image binarization processing on the image to be compared to obtain an image to be compared after the image binarization processing, and extracting image characteristic parameters of the image to be compared after the image binarization processing to serve as characteristic parameters to be compared;
step 4): and comparing the characteristic parameters to be compared with the standard characteristic parameters, judging the defect condition of the heat exchanger to be compared corresponding to the comparison result, and finishing the detection process.
The specific process of performing image binarization processing on the standard image in the step 2) is as follows: carrying out Gaussian filtering on the standard image, converting the standard image into a standard binary image through an OTSU algorithm, and finally carrying out closed operation on the standard binary image to obtain a standard image after image binarization processing;
the specific process of performing image binarization processing on the images to be compared in the step 3) is as follows: carrying out Gaussian filtering on the images to be compared, converting the images into binary images to be compared through an OTSU algorithm, and finally carrying out closing operation on the binary images to be compared to obtain images to be compared after the binarization processing of the images;
in the step 2), the standard characteristic parameters comprise vertex coordinates of the standard image after the image binarization, the number of pixels occupied by the standard image after the image binarization and the number of pixels occupied by the standard image after the image binarization with specified error expansion;
in the step 3), the feature parameters to be compared include vertex coordinates of the image to be compared after the image binarization process, the number of pixels occupied by the image to be compared after the image binarization process, and the number of pixels occupied by the image to be compared after the image binarization process after the expansion of the specified error.
In the step 2), the process of extracting the vertex coordinates of the standard image after the image binarization processing is as follows:
firstly, suppressing a pseudo edge caused by noise by using a Canny operator, detecting a pixel-level edge of a standard image after image binarization processing, and obtaining a refined standard edge contour image;
secondly, extracting straight lines at two sides of the part from the thinned standard edge contour image by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the standard central axis, acquiring a horizontal image of the part after the central axis is horizontal through the rotation of the thinned standard edge contour image of the rotation matrix, extracting coordinates corresponding to the vertexes of the input tube of the standard heat exchanger in the horizontal image, and taking the coordinates as vertex coordinates of the standard image after the image binarization processing;
the extraction mode of the pixel number occupied by the standard image after the image binarization processing is as follows: filling the inside of the thinned standard edge contour image with white pixels, obtaining the number of pixels of the white pixels and taking the number of pixels of the image corresponding to the input tube of the standard heat exchanger;
the extraction process of the pixel number occupied by the standard image after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating a standard expansion image for edge expansion of the thinned standard edge contour image according to the specified error range;
and secondly, filling white pixels in the standard expansion image to generate a mask image, acquiring the number of pixels of the white pixels in the mask image, and taking the mask image as the standard image after the image binarization processing to specify the number of pixels occupied by the error expansion.
In the step 3), the extraction process of the vertex coordinates of the image corresponding to the input tube of the heat exchanger to be compared is as follows:
firstly, suppressing a false edge caused by noise by using a Canny operator, detecting a pixel-level edge of an image to be compared after image binarization processing, and obtaining a refined edge contour image to be compared;
secondly, extracting straight lines at two sides of the part from the thinned edge profile image to be compared by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the axis to be compared, acquiring a horizontal image of the part after the central axis of the part is horizontal through the rotation matrix rotation thinned profile image of the edge to be compared, extracting coordinates corresponding to the vertex of the input tube of the heat exchanger to be compared in the horizontal image, and taking the coordinates as vertex coordinates of the image to be compared after image binarization processing;
the extraction mode of the pixel number occupied by the image to be compared after the image binarization processing is as follows: filling the interior of the thinned edge contour image to be compared with white pixels, obtaining the number of the pixels of the white pixels and taking the number of the pixels as the number of the pixels occupied by the image corresponding to the input tube of the heat exchanger to be compared;
the extraction process of the pixel number occupied by the image to be compared after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating an expanded image to be compared by expanding the edges of the thinned edge profile image to be compared according to the specified error range;
and secondly, filling white pixels in the expansion image to be compared to generate a mask image, obtaining the number of pixels of the white pixels in the mask image, and taking the mask image as the number of pixels occupied by the expansion image to be compared after the binarization processing of the image with specified errors.
The specific process of the step 4) is as follows:
4) -1 marking the vertex coordinates of the standard image after image binarization as (x, y), and marking the vertex coordinates of the image to be compared after image binarization as (x' p ,y′ p ) Let s= | (x' p -x) 2 +(y′ p -y) 2 I, wherein i is absolute value notation, size tolerance error limit is set and noted as δ p When S is less than or equal to delta p Judging that the input pipe of the heat exchanger to be compared is a size qualified piece, if S is more than delta p Judging that the input pipe of the heat exchanger to be compared is a size disqualified piece;
4) -2, the number of pixels occupied by the standard image after the image binarization is denoted as m, and the number of pixels occupied by the image to be compared after the image binarization is denoted as m p Setting the allowable error limit of the surface defect and recording as delta m When |m p -m|≥δ m When it is judged that the surface defect of the input pipe of the heat exchanger to be compared meets the specification, if |m p -m|<δ m Judging that the surface defect of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
4) -3, marking the number of pixels occupied by the standard image after the image binarization processing after the expansion of the specified error as c, and marking the number of pixels occupied by the image to be compared after the image binarization processing after the expansion of the specified error as c p An angle allowance error limit is set and recorded as delta c When |c p -c|≥δ c When the angle of the input pipe of the heat exchanger to be compared is judged to be in accordance with the specification, when the angle of the input pipe of the heat exchanger to be compared is |c p -c|<δ c And judging that the angle of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
Compared with the prior art, the method has the advantages that the calibrated camera shoots images of the standard heat exchanger parts from the preset positions with the same acquisition angles and the same viewing distance, binarization processing is carried out, the images after the binarization processing are detected, the edges are used for segmenting foreground and background, the edges after error expansion are calculated as characteristic parameters, repeated operation is carried out on the parts to be compared, and the parts to be compared are compared with the characteristic parameters of the standard parts, so that parts with various defects are screened out; compared with the traditional manual detection, the detection method adopted by the invention can rapidly and efficiently detect all the parts one by one, has good classification effect, can greatly improve the production efficiency, and simultaneously remarkably improves the qualification rate of the parts leaving the factory.
Detailed Description
The present invention is described in further detail below.
A three-dimensional visual inspection method for an engine heat exchanger interface, comprising the steps of:
step 1): and calibrating the internal parameters and the external parameters of the camera through the calibration plate to obtain the calibrated camera.
Step 2): obtaining images with a plurality of preset acquisition angles and equal viewing distances of a standard heat exchanger through a calibrated camera, dividing an image corresponding to an input tube of the standard heat exchanger in each image with the acquisition angles into standard images corresponding to the acquisition angles, performing image binarization on the standard images to obtain standard images subjected to image binarization, and extracting image characteristic parameters of the standard images subjected to image binarization as standard characteristic parameters, wherein the standard characteristic parameters comprise vertex coordinates of the standard images subjected to image binarization, the pixel number occupied by the standard images subjected to image binarization and the pixel number occupied by the standard images subjected to image binarization after the appointed error expansion; the specified error is expanded in detection, namely, 2.5mm is expanded according to the central axis, namely, 2.5/0.094=26.5 pixels, and the edge expansion is carried out by combining the calculation of a specific method formula so as to judge whether the part is incomplete;
the specific process of carrying out image binarization processing on the standard image is as follows: carrying out Gaussian filtering on the standard image, converting the standard image into a standard binary image through an OTSU algorithm, and finally carrying out closed operation on the standard binary image to obtain a standard image after image binarization processing;
the extraction process of the vertex coordinates of the standard image after the image binarization processing is as follows:
firstly, suppressing a pseudo edge caused by noise by using a Canny operator, detecting a pixel-level edge of a standard image after image binarization processing, and obtaining a refined standard edge contour image;
secondly, extracting straight lines at two sides of the part from the thinned standard edge contour image by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the standard central axis, acquiring a horizontal image of the part after the central axis is horizontal through the rotation of the thinned standard edge contour image of the rotation matrix, extracting coordinates corresponding to the vertexes of the input tube of the standard heat exchanger in the horizontal image, and taking the coordinates as vertex coordinates of the standard image after the image binarization processing; in the process, the central axis is acquired, the rotation matrix is acquired, the horizontal image is acquired, and the vertex coordinates are obtained by deduction from a mathematical formula of a conventional standard;
the extraction mode of the pixel number occupied by the standard image after the image binarization processing is as follows: filling the inside of the thinned standard edge contour image with white pixels, obtaining the number of pixels of the white pixels and taking the number of pixels of the image corresponding to the input tube of the standard heat exchanger;
the extraction process of the pixel number occupied by the standard image after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating a standard expansion image for edge expansion of the thinned standard edge contour image according to the specified error range;
and secondly, filling white pixels in the standard expansion image to generate a mask image, acquiring the number of pixels of the white pixels in the mask image, and taking the mask image as the standard image after the image binarization processing to specify the number of pixels occupied by the error expansion.
Step 3): obtaining images of a plurality of preset acquisition angles of a heat exchanger to be compared through a calibrated camera, dividing an image corresponding to an input tube of the heat exchanger to be compared in the images of each acquisition angle to serve as an image to be compared, performing image binarization processing on the image to be compared to obtain an image to be compared after the image binarization processing, and extracting image characteristic parameters of the image to be compared after the image binarization processing to serve as the characteristic parameters to be compared, wherein the characteristic parameters to be compared comprise vertex coordinates of the image to be compared after the image binarization processing, the pixel number occupied by the image to be compared after the image binarization processing and the pixel number occupied by the image to be compared after the image binarization processing after the specified error expansion;
the specific process of performing image binarization processing on the images to be compared comprises the following steps: carrying out Gaussian filtering on the images to be compared, converting the images into binary images to be compared through an OTSU algorithm, and finally carrying out closing operation on the binary images to be compared to obtain images to be compared after the binarization processing of the images;
the extraction process of the vertex coordinates of the image corresponding to the input tube of the heat exchanger to be compared is as follows:
firstly, suppressing a false edge caused by noise by using a Canny operator, detecting a pixel-level edge of an image to be compared after image binarization processing, and obtaining a refined edge contour image to be compared;
secondly, extracting straight lines at two sides of the part from the thinned edge profile image to be compared by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the axis to be compared, acquiring a horizontal image of the part after the central axis of the part is horizontal through the rotation matrix rotation thinned profile image of the edge to be compared, extracting coordinates corresponding to the vertex of the input tube of the heat exchanger to be compared in the horizontal image, and taking the coordinates as vertex coordinates of the image to be compared after image binarization processing;
the extraction mode of the pixel number occupied by the image to be compared after the image binarization processing is as follows: filling the interior of the thinned edge contour image to be compared with white pixels, obtaining the number of the pixels of the white pixels and taking the number of the pixels as the number of the pixels occupied by the image corresponding to the input tube of the heat exchanger to be compared;
the extraction process of the pixel number occupied by the image to be compared after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating an expanded image to be compared by expanding the edges of the thinned edge profile image to be compared according to the specified error range;
and secondly, filling white pixels in the expansion image to be compared to generate a mask image, obtaining the number of pixels of the white pixels in the mask image, and taking the mask image as the number of pixels occupied by the expansion image to be compared after the binarization processing of the image with specified errors.
In actual detection, four CCD cameras are respectively positioned at 0,90 degrees, 180 degrees and 270 degrees, and the required standard heat exchanger image and the heat exchanger image to be compared are respectively obtained through fixed-angle and fixed-viewing-distance shooting.
Step 4): comparing the characteristic parameters to be compared with the standard characteristic parameters, judging the defect condition of the heat exchanger to be compared corresponding to the comparison result, and completing the detection process, wherein the specific process is as follows:
4) -1 marking the vertex coordinates of the standard image after image binarization as (x, y), and marking the vertex coordinates of the image to be compared after image binarization as (x' p ,y′ p ) Let s= | (x' p -x) 2 +(y′ p -y) 2 I, wherein i is absolute value notation, size tolerance error limit is set and noted as δ p When S is less than or equal to delta p Judging that the input pipe of the heat exchanger to be compared is a size qualified piece, if S is more than delta p Judging that the input pipe of the heat exchanger to be compared is a size disqualified piece;
4) -2, the number of pixels occupied by the standard image after the image binarization is denoted as m, and the number of pixels occupied by the image to be compared after the image binarization is denoted as m p Setting the allowable error limit of the surface defect and recording as delta m When |m p -m|≥δ m When it is judged that the surface defect of the input pipe of the heat exchanger to be compared meets the specification, if |m p -m|<δ m Judging that the surface defect of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
4) -3, marking the number of pixels occupied by the standard image after the image binarization processing after the expansion of the specified error as c, and marking the number of pixels occupied by the image to be compared after the image binarization processing after the expansion of the specified error as c p An angle allowance error limit is set and recorded as delta c When |c p -c|≥δ c When the angle of the input pipe of the heat exchanger to be compared is judged to be in accordance with the specification, when the angle of the input pipe of the heat exchanger to be compared is |c p -c|<δ c And judging that the angle of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
Claims (2)
1. The three-dimensional visual detection method of the engine heat exchanger interface is characterized by comprising the following steps of:
step 1): calibrating the internal parameters and the external parameters of the camera through a calibration plate to obtain a calibrated camera;
step 2): obtaining images with a plurality of preset acquisition angles and equal viewing distances of a standard heat exchanger through a calibrated camera, dividing an image corresponding to an input tube of the standard heat exchanger in each image with the acquisition angles into standard images corresponding to the acquisition angles, performing image binarization on the standard images to obtain standard images subjected to image binarization, and extracting image characteristic parameters of the standard images subjected to image binarization as standard characteristic parameters, wherein the standard characteristic parameters comprise vertex coordinates of the standard images subjected to image binarization, the pixel number occupied by the standard images subjected to image binarization and the pixel number occupied by the standard images subjected to image binarization after the appointed error expansion;
the extraction process of the vertex coordinates of the standard image after the image binarization processing is as follows:
firstly, suppressing a pseudo edge caused by noise by using a Canny operator, detecting a pixel-level edge of a standard image after image binarization processing, and obtaining a refined standard edge contour image;
secondly, extracting straight lines at two sides of the part from the thinned standard edge contour image by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the standard central axis, acquiring a horizontal image of the part after the central axis is horizontal through the rotation of the thinned standard edge contour image of the rotation matrix, extracting coordinates corresponding to the vertexes of the input tube of the standard heat exchanger in the horizontal image, and taking the coordinates as vertex coordinates of the standard image after the image binarization processing;
the extraction mode of the pixel number occupied by the standard image after the image binarization processing is as follows: filling the inside of the thinned standard edge contour image with white pixels, obtaining the number of pixels of the white pixels and taking the number of pixels of the image corresponding to the input tube of the standard heat exchanger;
the extraction process of the pixel number occupied by the standard image after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating a standard expansion image for edge expansion of the thinned standard edge contour image according to the specified error range;
secondly, filling white pixels in the standard expansion image to generate a mask image, obtaining the number of pixels of the white pixels in the mask image, and taking the mask image as the standard image after the image binarization processing to specify the number of pixels occupied by the error expansion;
step 3): obtaining images of a plurality of preset acquisition angles of a heat exchanger to be compared through a calibrated camera, dividing an image corresponding to an input tube of the heat exchanger to be compared in the images of each acquisition angle to serve as an image to be compared, performing image binarization processing on the image to be compared to obtain an image to be compared after the image binarization processing, and extracting image characteristic parameters of the image to be compared after the image binarization processing to serve as the characteristic parameters to be compared, wherein the characteristic parameters to be compared comprise vertex coordinates of the image to be compared after the image binarization processing, the pixel number occupied by the image to be compared after the image binarization processing and the pixel number occupied by the image to be compared after the image binarization processing after the specified error expansion;
the extraction process of the vertex coordinates of the image corresponding to the input tube of the heat exchanger to be compared is as follows:
firstly, suppressing a false edge caused by noise by using a Canny operator, detecting a pixel-level edge of an image to be compared after image binarization processing, and obtaining a refined edge contour image to be compared;
secondly, extracting straight lines at two sides of the part from the thinned edge profile image to be compared by adopting Hough transformation, and acquiring the central axis of the part according to the straight lines at two sides of the part;
thirdly, acquiring a rotation matrix according to the slope of the axis to be compared, acquiring a horizontal image of the part after the central axis of the part is horizontal through the rotation matrix rotation thinned profile image of the edge to be compared, extracting coordinates corresponding to the vertex of the input tube of the heat exchanger to be compared in the horizontal image, and taking the coordinates as vertex coordinates of the image to be compared after image binarization processing;
the extraction mode of the pixel number occupied by the image to be compared after the image binarization processing is as follows: filling the interior of the thinned edge contour image to be compared with white pixels, obtaining the number of the pixels of the white pixels and taking the number of the pixels as the number of the pixels occupied by the image corresponding to the input tube of the heat exchanger to be compared;
the extraction process of the pixel number occupied by the image to be compared after the image binarization processing after the specified error expansion is as follows:
setting a specified error range, and generating an expanded image to be compared by expanding the edges of the thinned edge profile image to be compared according to the specified error range;
secondly, filling white pixels in the expanded image to be compared to generate a mask image, obtaining the number of pixels of the white pixels in the mask image, and taking the mask image as the number of pixels occupied by the expanded image to be compared after the binarization processing of the image with specified errors;
step 4): comparing the characteristic parameters to be compared with the standard characteristic parameters, judging the defect condition of the heat exchanger to be compared corresponding to the comparison result, and completing the detection process, wherein the specific process is as follows:
4) -1 marking the vertex coordinates of the standard image after image binarization as (x, y), and marking the vertex coordinates of the image to be compared after image binarization as (x' p ，y′ p ) Let s= | (x' p -x) 2 +(y′ p -y) 2 I, wherein i is absolute value notation, size tolerance error limit is set and noted as δ p When S is less than or equal to delta p Judging that the input pipe of the heat exchanger to be compared is a size qualified piece, if s is more than delta p Judging that the input pipe of the heat exchanger to be compared is a size disqualified piece;
4) -2, the number of pixels occupied by the standard image after the image binarization is denoted as m, and the number of pixels occupied by the image to be compared after the image binarization is denoted as m p Setting the allowable error limit of the surface defect and recording as delta m When |m p -m|≥δ m When it is judged that the surface defect of the input pipe of the heat exchanger to be compared meets the specification, if |m p -m|＜δ m Judging that the surface defect of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
4) -3, marking the number of pixels occupied by the standard image after the image binarization processing after the expansion of the specified error as c, and marking the number of pixels occupied by the image to be compared after the image binarization processing after the expansion of the specified error as c p An angle allowance error limit is set and recorded as delta c When |c p -c|≥δ c When the angle of the input pipe of the heat exchanger to be compared is judged to be in accordance with the specification, when the angle of the input pipe of the heat exchanger to be compared is |c p -c|＜δ c And judging that the angle of the input pipe of the heat exchanger to be compared does not accord with the specification, wherein the I.
2. The three-dimensional visual inspection method of an engine heat exchanger interface according to claim 1, wherein the specific process of performing image binarization processing on the standard image in the step 2) is as follows: carrying out Gaussian filtering on the standard image, converting the standard image into a standard binary image through an OTSU algorithm, and finally carrying out closed operation on the standard binary image to obtain a standard image after image binarization processing;
the specific process of performing image binarization processing on the images to be compared in the step 3) is as follows: and carrying out Gaussian filtering on the images to be compared, converting the images into binary images to be compared through an OTSU algorithm, and finally carrying out closing operation on the binary images to be compared to obtain the images to be compared after the image binarization processing.
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