A method for measuring the pinion of a double gear or a multi-gear

Abstract

The present invention relates to the field of gear measurement technology, and in particular to a method for measuring the pinion of a duplex gear or a multi-gear. The method comprises the following steps: S1, illumination adjustment; S2, image acquisition and processing; S3, image stitching; S4, light source change, changing the position of the light source to rotate it around the gear axis at any angle; S5, multi-view synthesis and repeating the previous steps, collecting high-contrast pinion images at different viewing angles, and stitching them into an overall high-contrast image. S6, brightness balance, calculating and applying brightness compensation. The side-light controllable rotating illumination light source correction method proposed in the present invention can eliminate the problem of inaccurate gear contour extraction caused by the grayscale difference in the synthesized image caused by the different brightness of the same light source rotated to different positions around the gear axis and different light sources at different positions, thereby achieving more accurate machine vision measurement of the pinion of the duplex gear.

Description

Technical Field

[0001] The invention relates to the technical field of gear measurement, and in particular to a method for measuring a pinion of a double gear or a multi-gear. Background Art

[0002] Gears are the most widely used key basic parts. The quality of gears often directly determines the operating performance, service life, safety and reliability of equipment. Measurement is an important means to evaluate the performance of gears, find the source of gear errors, and improve the quality of gear products. Dual gears refer to two gears made into one piece. They are mainly used in speed change mechanisms and can make the structure more compact. When the structure allows, more than two gears can also be made into one piece to form a multi-gear.

[0003] Machine vision technology can easily measure the large gear of a spur gear duplex gear, but machine vision measurement of the small gear of a duplex gear has always been a technical problem. When measuring the large gear of a spur gear duplex gear, backlighting is usually used. Backlighting, also known as bottom lighting or transmitted lighting, is a lighting method commonly used for precise measurement of geometric dimensions. Under backlighting, the gear teeth of the large gear of a spur gear duplex gear can be clearly imaged, and analytical measurements of multiple single errors such as tooth profile deviation, pitch deviation, normal length, and ring runout can be achieved. However, the gear teeth of the small gear will be blocked by the large gear and cannot be imaged on the photosensitive element of the industrial camera through the lens, so it is difficult to achieve machine vision measurement. If the top light illumination method is used, the contrast of the small gear image of the duplex gear obtained at the edge of the gear teeth is basically the same, but the contrast is not high, so it is difficult to achieve accurate contour extraction and gear error measurement. The method of using side lighting to enhance the local contrast of the contour of the gear to be measured and using the high-contrast contour area to synthesize the complete gear image can obtain an image of the pinion of the double gear with high contour contrast of each tooth. However, due to the difference in brightness of the same light source or different light sources at different positions rotated around the gear axis, when illuminating the gear to be measured, there are grayscale differences in the multiple gear image areas with local high contrast collected for synthesizing the gear image. When the contour of the image synthesized by these images is extracted, stripes that interfere with the gear contour will appear, resulting in inaccurate measurement results. Summary of the invention

[0004] In order to overcome the problems existing in the prior art, the present invention provides a method for measuring the pinion of a duplex gear or a multi-gear. Based on the side-light controllable rotating illumination light source correction method, the inaccurate gear contour extraction problem caused by the grayscale difference in the synthetic image caused by the different brightness of the same light source rotated to different positions around the gear axis and different light sources at different positions can be eliminated, thereby achieving more accurate machine vision measurement of the pinion of the duplex gear.

[0005] A method for measuring a pinion of a double gear or a multi-gear, comprising the following steps:

[0006] S1. Select an illumination light source for image acquisition and adjust the position, illumination direction, and initial brightness parameters of the light source so that the end face and tooth surface of the pinion gear being measured are illuminated unevenly, and adjust the contrast of the local position of the pinion gear tooth edge in the acquired image to a state where the contrast is greater than that of other positions;

[0007] S2, collect images and extract the tooth profile area with high contrast from the image; use the image acquisition device to obtain the small gear image under the current conditions, make a polygon so that the shadow of the small gear is wrapped by the polygon, let the upper right corner point away from the gear center be B, and the lower right corner point be C; take the gear center as the origin O, connect the rays OB and OC; then extract the small gear image in the ∠BOC range as the image with high contrast in the current image; make a ray OE through point O, E is a point on the polygon, take OE as the starting edge, take the OE edge of the first collected image as the starting edge, take the preset direction as the positive direction of the angle, calculate and record the angle values ​​of ∠BOE, ∠EOC and ∠BOC corresponding to each image;

[0008] S3, synthesize the image; assign the grayscale value of the pixel within the range of ∠BOC in the current image to the same position of the image to be stitched with the same resolution. The value of ∠BOC is equal to the absolute value of ∠BOE minus ∠EOC;

[0009] S4. Adjust the position of the light source; rotate the light source around the axis of the gear to be measured to any angle between 0 and 360°;

[0010] S5, repeating steps S2, S3 and S4, using a plurality of local images of the pinions of the double gears with high contrast to synthesize a complete high-contrast image;

[0011] S6. Perform light source brightness compensation on the synthesized image. Step 1: Take the median of the pixel grayscale values ​​of the hub part in the range of ∠BOE~∠EOC, i.e., ∠BOC, of ​​n collected images as the G value reflecting the brightness index of the light source when collecting images; Step 2: Take the maximum value of the n G values ​​as the reference, add the grayscale values ​​of the pixels in n different ∠BOC ranges of the synthesized image to the difference between the reference G value and the G value in the corresponding interval, and obtain the image after compensating for the light source brightness difference.

[0012] Furthermore, the polygon in S2 includes any one of a rectangle, a triangle, a trapezoid or a pentagon.

[0013] Furthermore, in S2, the clockwise or counterclockwise direction is the positive direction.

[0014] Furthermore, in S6, any one of the median, mode or average of the grayscale values ​​of pixels inside the axial hole or outside the tooth profile in the ∠BOC region is used as the index G value reflecting the brightness of the light source.

[0015] Furthermore, in S6, any one of the n G values ​​is used as a reference.

[0016] The beneficial effects of the present invention are as follows: the technical solution proposed in the present invention can eliminate the problem of uneven grayscale of the synthetic image caused by differences in the position and brightness of the light source, and realize more accurate measurement of the size of the small gear of the double gear based on machine vision. In combination with other existing technologies, the large gear and the small gear of the double gear can also be measured simultaneously on the same instrument, thereby achieving a better effect of evaluating the performance of the gear and analyzing the source of the gear process error. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart of a method for measuring a pinion of a double gear or a multi-gear according to the present invention;

[0018] Figure 2 It is a schematic diagram of the side-lighting of a double gear image;

[0019] Figure 3 It is an example of a division scheme that reflects the area of ​​the point taken by the brightness of the light source;

[0020] Figure 4 It is an image composed of multiple images of pinions of a duplex gear with local high contrast that are not corrected for light sources;

[0021] Figure 5 The image of the pinion of the double gear is synthesized after eliminating the influence of the brightness of the light source by the method of the present invention.

[0022] The names and serial numbers of the parts in the figure are: 1-image acquisition device, 2-light source for illumination, 3-double gear to be measured, 4-shadow produced by the pinion of the double gear, 5-gear base, 6-light source base, 7-acquisition device base, 8-instrument base. DETAILED DESCRIPTION

[0023] The advantages, features and specific implementation methods of the present invention are described in a technical solution in conjunction with the accompanying drawings. These embodiments are given as examples only with reference to the accompanying drawings and are non-limiting descriptions, illustrations and explanations of the present invention.

[0024] In the prior art, the method based on machine vision technology and using side lighting to enhance the local contrast of the gear contour to be measured, and synthesizing the complete gear image using the high-contrast contour area can obtain an image of the pinion of the double gear with high contour contrast of each tooth. However, due to the difference in brightness of the same light source rotated to different positions around the gear axis or different light sources at different positions, the gear image synthesized using these images has grayscale differences, such as Figure 4 As shown in the figure, when this image is used for contour extraction, stripes will appear that interfere with the gear contour, resulting in inaccurate measurement results.

[0025] The present invention proposes a side-light controllable rotating illumination light source correction method. The pixel grayscale value of a specific area of ​​a double gear image collected under different side-light illumination conditions is used to reflect the brightness of the light source, and the brightness of the light source is adjusted to solve the problem of large grayscale differences in images collected under the same light source at different positions and different light sources at different positions when the end face and tooth surface of the pinion are illuminated unevenly, that is, the contrast of other parts of the image at the edge of the pinion tooth under the sacrifice of the local clarity of the image is enhanced.

[0026] refer to Figure 2 The lighting collection device shown in the figure has a collection device base 7, a light source base 6 and a gear base 5 for placing the measured double gear 3 on the upper part of the instrument base 8, an image collection device 1 is provided on the collection device base 7, and a lighting light source 2 is provided on the light source base 6, wherein the light source base 6 is rotatably arranged on the collection device base 7, and is used to adjust the lighting light source 2 at different lighting angles, and the shadow 4 produced by the pinion of the double gear can be formed by turning on the lighting light source 2; in the embodiment of the present invention, a high-brightness LED with 8 annular distributions that can rotate along the gear axis by a certain angle and control the brightness respectively is used to illuminate the pinion of the double gear from 30 different angles, and a software compensation method that eliminates the influence of the light source on the machine vision measurement of the pinion of the double gear is used to collect and synthesize images, refer to Figure 1 As shown, the method consists of the following steps:

[0027] S1: Select a green high-brightness LED with a 120° illumination range, evenly distribute the LED along the axis of the camera and illuminate vertically downward, and place the double pinion gear in the center of the camera field of view. Make the end face and tooth surface of the pinion gear under test receive uneven illumination, adjust the contrast of the local position of the pinion gear tooth edge in the captured image to be greater than the contrast of other positions, and adjust the initial brightness so that the median grayscale value of the image in the high-contrast hub area reaches 30;

[0028] S2: Capture an image and extract a tooth profile area with a high contrast from the image; use an image acquisition device to obtain an image of the pinion under the current conditions, such as Figure 3As shown, draw a rectangle ABCD so that the shadow of the pinion is wrapped in the rectangle, let the upper left corner point close to the center of the gear be A and the lower left corner point be D, the upper right corner point far from the center of the gear be B, and the lower right corner point be C; take the center of the gear as the origin O, connect the rays OB and OC; then extract the pinion image in the ∠BOC range as the image with higher contrast in the current image; draw a horizontal ray OE through point O, E is the intersection of the ray and the BC edge, take the OE edge of the first collected image as the starting edge, let the clockwise direction be the positive direction of the angle, calculate and record the angle values ​​of ∠BOE, ∠EOC and ∠BOC corresponding to each image;

[0029] S3: Synthesize images; assign the grayscale values ​​of pixels within the ∠BOC range to the same positions of the images to be stitched with the same resolution; the value of ∠BOC is equal to the absolute value of ∠BOE minus ∠EOC. Extract the grayscale values ​​of all pixels within the ∠BOC range in the current acquired image, and assign the grayscale values ​​of these pixels to the pixels at the same coordinate positions of the image to be synthesized;

[0030] S4: Adjust the position of the light source; rotate the lighting source 12° around the axis of the gear being tested;

[0031] S5: repeating steps S2, S3 and S4, and synthesizing a complete high-contrast image using the partial images of the pinions of the multiple double gears with high contrast;

[0032] S6: Compensate the brightness of the light source for the synthesized image; 1) Take the median of the pixel grayscale values ​​of the hub part in the range of ∠BOE~∠EOC, i.e., ∠BOC, of ​​n collected images as the G value reflecting the brightness index of the light source when collecting the image; 2) Take the maximum value of the n G values ​​as the reference, add the grayscale values ​​of the pixels in n different ∠BOC ranges of the synthesized image to the difference between the reference G value and the G value in the corresponding interval, and obtain the image after compensating the brightness difference of the light source, as shown in Figure 5 The image shown is a small gear image of a double gear synthesized after eliminating the influence of the brightness of the light source using the method of the present invention.

[0033] It should be noted that in step S2 of the method for eliminating the influence of light source on the machine vision measurement of the pinion of a duplex gear and the compensation method for eliminating the influence of light source on the machine vision measurement of the pinion of a duplex gear, other polygons can also be used to select the shadow of the pinion, such as a triangle, a trapezoid, a pentagon, etc.; when the position of the light source or the angle of the light source that needs to rotate around the camera axis is fixed and the order is certain, the area for correcting the brightness of the light source can be directly selected based on experience, thereby improving the efficiency of correcting the brightness.

[0034] In the method of eliminating the influence of light source on the machine vision measurement of the pinion of the duplex gear, the position of the light source is adjusted. When the lighting light source is rotated around the axis of the gear to be measured or the axis of the camera at an angle between 0 and 360 degrees, it can be rotated in either clockwise or counterclockwise direction. The effect of a rotation angle exceeding 360 degrees is equivalent to that between 0 and 360 degrees. It is acceptable for the rotation angle to be equal each time or unequal each time. The smaller the rotation angle, the better the correction effect.

[0035] In the method of eliminating the influence of light source on the machine vision measurement of the pinion of a duplex gear, the median, mode and mean of the grayscale values ​​of pixels inside the shaft hole or outside the tooth profile on the high-contrast area image can be used as index values ​​reflecting the brightness of the light source. The closer the selected area is to the local high-contrast gear image, the better the effect.

[0036] In the method of eliminating the influence of light source on the machine vision measurement of the pinion of a duplex gear, the median, mode and mean of the grayscale value of pixels in an area of ​​any position and shape within the camera's field of view can be selected as index values ​​reflecting the brightness of the light source. The closer the selected area is to the target tooth profile, the better the effect.

[0037] In addition to the above-mentioned embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent reasoning transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for measuring a pinion of a double gear or a multi-gear, characterized in that: The following steps are involved: S1. Select an illumination light source for image acquisition and adjust the position, illumination direction, and initial brightness parameters of the light source so that the end face and tooth surface of the pinion gear being measured are illuminated unevenly, and adjust the contrast of the local position of the pinion gear tooth edge in the acquired image to a state where the contrast is greater than that of other positions; S2, collect images and extract the tooth profile area with high contrast from the images; use the image acquisition device to obtain the image of the pinion under the current conditions, make a polygon so that the shadow of the pinion is wrapped by the polygon, and let the upper right corner point away from the center of the gear be B, and the lower right corner point be C; Take the gear center as the origin O, connect the rays OB and OC; then extract the small gear image in the ∠BOC range as the image with higher contrast in the current image; make a ray OE through point O, E is a point on the polygon, take the OE edge of the first captured image as the starting edge, take the preset direction as the positive direction of the angle, calculate and record the angle values ​​of ∠BOE, ∠EOC and ∠BOC corresponding to each image; S3, synthesizing the image; assigning the grayscale values ​​of pixels within the range of ∠BOC in the current image to the same positions of the image to be stitched with the same resolution, wherein the value of ∠BOC is equal to the absolute value of ∠BOE minus ∠EOC; S4. Adjust the position of the light source; rotate the light source around the axis of the gear to be measured to any angle between 0 and 360°; S5, repeating steps S2, S3 and S4, using a plurality of local images of the pinions of the double gears with high contrast to synthesize a complete high-contrast image; S6. Perform light source brightness compensation on the synthesized image; Step 1: Use the median of the pixel grayscale values ​​of the hub part in the range of ∠BOE~∠EOC, i.e., ∠BOC, of ​​n acquired images as the G value reflecting the brightness index of the light source when acquiring the image; Step 2: Use the maximum value of the n G values ​​as the reference, add the grayscale values ​​of the pixels in n different ∠BOC ranges of the synthesized image to the difference between the reference G value and the G value in the corresponding interval, and obtain the image after compensating for the light source brightness difference.

2. A method for measuring a pinion of a double gear or a multi-gear according to claim 1, characterized in that: The polygon in S2 includes any one of a rectangle, a triangle, a trapezoid or a pentagon.

3. A method for measuring a pinion of a double gear or a multi-gear according to claim 1, characterized in that: In S2, the clockwise or counterclockwise direction is the positive direction.

4. A method for measuring a pinion of a double gear or a multi-gear according to claim 1, characterized in that: In S6, any one of the median, mode or average of the grayscale values ​​of pixels inside the axial hole or outside the tooth profile in the ∠BOC region is used as the index G value reflecting the brightness of the light source.

5. A method for measuring a pinion of a double gear or a multi-gear according to claim 4, characterized in that: In the above S6, any one of the n G values ​​is used as a reference.

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