Device detection method, apparatus, equipment, and medium based on frequency domain analysis

Abstract

The present invention relates to a device detection method and apparatus, equipment, and medium based on frequency domain analysis, and relates to the field of visual measurement technology. The present invention uses a frequency domain analysis method to determine the number of teeth of the turbine and the position of the tooth top and tooth bottom, and on this basis can calculate parameters such as the distance from the tooth top or tooth bottom to the center of the circle and the distance difference between adjacent tooth tops and tooth bottoms. Since statistical information is used, slight changes in the contour shape, such as dents, burrs, small defects, etc., will not affect the detection accuracy. The method provided by the present invention is also suitable for the detection of gears. The present invention adopts non-contact measurement, which greatly improves the measurement efficiency compared to contact measurement. Combined with an automatic loading and unloading device, it can achieve full inspection of the product instead of just sampling inspection. Compared with the existing non-contact measurement scheme, since the present invention uses an angle histogram combined with a frequency domain analysis method, it uses all points inside the tooth profile and can be insensitive to noise and defects.

Description

Technical Field

[0001] The present invention relates to the field of visual measurement technology, and in particular to a device detection method, apparatus, equipment, and medium based on frequency domain analysis. Background Art

[0002] Currently, turbine inspection methods can be categorized into contact and visual measurement. Contact measurement is inefficient, limited to spot checks, and relies on subjective judgment. Visual measurement methods typically use the distance from the turbine's outer contour to the center of a circle, or a method that uses a fitted line and its intersection to determine the position of the tooth top and bottom. However, both methods rely on local information when determining the tooth top or bottom, potentially resulting in significant errors. Summary of the Invention

[0003] In order to achieve the above-mentioned purpose and other advantages according to the present invention, a first object of the present invention is to provide a device detection method based on frequency domain analysis, comprising the following steps:

[0004] Acquire a contour image of the device to be inspected;

[0005] Obtaining a spot area from the contour image by using a set threshold;

[0006] The center of the circle obtained by fitting the contour points is the center point of the device to be tested;

[0007] In the spot area, a spot image of the tooth profile is obtained by using a set threshold;

[0008] The vector direction inside the tooth profile is evenly divided by the set angular interval. The vector is a vector determined by taking the center point of the device to be detected as the starting point and each point inside the gear as the end point;

[0009] Scan all points inside the tooth profile, calculate the angle between the points inside the tooth profile and the center point, and obtain the angle statistical histogram of the device to be tested;

[0010] Performing Fourier transform on the angle statistical histogram to obtain a frequency spectrum of the histogram;

[0011] The index of the harmonic with the largest amplitude is obtained from the spectrum diagram of the histogram as the number of teeth of the device to be detected;

[0012] Calculate the angles of all tooth tops and tooth bottoms using the spectrum value corresponding to the harmonic with the largest amplitude;

[0013] A set of rays is obtained through the center point of the device to be detected, the angle of the tooth top and the angle of the tooth bottom. The intersection of the rays corresponding to all tooth tops and the tooth contour is the position of the tooth top, and the intersection of the rays corresponding to all tooth bottoms and the tooth contour is the position of the tooth bottom.

[0014] Furthermore, the step of obtaining the contour image of the device to be inspected comprises the following steps:

[0015] Acquire an outer contour image of the device to be inspected;

[0016] Acquire the tooth profile image of the device to be inspected.

[0017] Furthermore, the acquiring of the spot area map from the contour image by using the set threshold value is specifically acquiring the spot area of ​​the device to be detected from the outer contour image of the device to be detected by using the set threshold value;

[0018] The step of acquiring the spot image of the tooth profile within the spot region by using a set threshold value specifically involves acquiring the spot image of the tooth profile within the spot region of the tooth profile image of the device to be inspected by using a set threshold value.

[0019] Furthermore, obtaining the spot area map from the contour image by setting the threshold value includes setting the pixel points in the contour image with brightness lower than the threshold value as the foreground, and setting the pixel points in the contour image with brightness higher than the threshold value as the background.

[0020] Furthermore, fitting a circle through the contour points to obtain a center point of the circle as the center point of the device to be detected includes the following steps:

[0021] Calculate the zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point;

[0022] The rough position of the circle center is obtained by combining the calculated zero-order moment parameters, first-order moment parameters and second-order moment parameters of the foreground point with the center of gravity calculation formula;

[0023] The rough value of the radius is obtained by combining the calculated zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point with the radius calculation formula;

[0024] Take points at equal angles on the circumference, and measure along the line connecting the point and the center of the circle at each point to obtain the precise edge point of the contour.

[0025] The least square method is used to fit a circle according to the edge points of the contour, and the obtained precise center of the circle is the center of the device to be detected.

[0026] Furthermore, the step of fitting a circle through the contour points to obtain a center point of the circle as the center point of the device to be detected further includes the following steps:

[0027] By setting the ratio of external points, the interference of noise or background dirt is removed to obtain the center point.

[0028] Furthermore, the step of calculating the angles of all tooth tops and tooth bottoms using the spectrum value corresponding to the harmonic with the largest amplitude includes the following steps:

[0029] Get the spectrum value corresponding to the harmonic with the largest amplitude. The angle of the vector is:

[0030]

[0031] Where vecX is the real part of the spectrum value corresponding to the harmonic with the largest amplitude, vecY is the imaginary part of the spectrum value corresponding to the harmonic with the largest amplitude, and maxIndex is the number of teeth;

[0032] Calculate the angles of all tooth tops and bottoms using the angle of the spectrum value corresponding to the harmonic with the largest amplitude and the number of teeth;

[0033] The following steps are also included:

[0034] Combining the magnification of the telecentric lens and the design standards of the device to be tested, the physical distance from each tooth top or tooth bottom to the center of the device to be tested is obtained, which serves as reference data for quality inspection of the device to be tested.

[0035] Determine whether the tooth pitch, tooth thickness and tooth groove width of the device to be tested meet the design standards.

[0036] The second object of the present invention is to provide a device detection apparatus based on frequency domain analysis, comprising: a camera, a telecentric lens, a ring light, a backlight source, and a control device, wherein the backlight source is used to provide a light source from the bottom of the device to be detected, the ring light is used to provide a light source from the top of the device to be detected, the camera and the telecentric lens are used to capture an image of the device to be detected, and the control device is used to execute a device detection method based on frequency domain analysis.

[0037] The third object of the present invention is to provide an electronic device comprising: a memory on which a program code is stored; a processor connected to the memory, and when the program code is executed by the processor, a device detection method based on frequency domain analysis is implemented.

[0038] A fourth object of the present invention is to provide a computer-readable storage medium having program instructions stored thereon, wherein the program instructions are executed to implement a device detection method based on frequency domain analysis.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] This invention provides a method using frequency domain analysis to determine the number of turbine teeth and the locations of tooth tips and tooth bottoms. Based on this, parameters such as the distance from the tooth tip or tooth bottom to the center of a circle and the difference in distance between adjacent tooth tips and tooth bottoms can be calculated. Because statistical information is used, minor changes in the profile shape, such as dents, burrs, and small defects, do not affect detection accuracy. The method provided by this invention is also applicable to gear inspection.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the description, the following preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0043] Figure 1 Schematic diagram of a device detection apparatus based on frequency domain analysis in Example 1;

[0044] Figure 2 Flowchart of the device detection method based on frequency domain analysis of Example 2;

[0045] Figure 3 This is the outer contour image of the turbine in Example 2;

[0046] Figure 4 This is the tooth profile image of the turbine in Example 2;

[0047] Figure 5 is a spot image of the turbine of Example 2;

[0048] Figure 6 The spot area of ​​the tooth profile image of the turbine in Example 2;

[0049] Figure 7 Angular statistical histogram of the turbine in Example 2;

[0050] Figure 8 is the amplitude of the histogram of Example 2;

[0051] Figure 9 Schematic diagram of tooth profile, tooth top position, and tooth bottom position of Example 2;

[0052] Figure 10 This is a schematic diagram of an electronic device according to Example 3;

[0053] Figure 11 Schematic diagram of a computer-readable storage medium of Example 4.

[0054] In the figure: 1. Backlight; 2. Ring light; 3. Telecentric lens; 4. Camera; 5. Turbine. DETAILED DESCRIPTION

[0055] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0056] Example 1

[0057] The device detection device based on frequency domain analysis is used to detect the number of teeth, tooth tops, tooth bottoms and tooth defects of the device to be detected. In order to take a clear outline image of the device to be detected, such as Figure 1 As shown, it includes: a camera 4, a telecentric lens 3, a ring light 2, a backlight source 1, and a control device. The backlight source 1 is used to provide a light source from the bottom of the device to be detected, wherein the device to be detected is a turbine 5 or a gear, etc. The ring light 2 is used to provide a light source from the top of the device to be detected, and the camera 4 and the telecentric lens 3 are used to capture an image of the device to be detected. In this embodiment, the backlight source 1 is a parallel backlight source 1. The backlight source 1 is placed on a horizontal table, the turbine 5 is placed vertically on the backlight source 1, and then the ring light 2 is placed above the turbine 5. The optical axis of the telecentric lens 3 is perpendicular to the plane of the backlight source 1. First, turn off the ring light 2, turn on the backlight source 1, and capture the first image to obtain the outer contour image of the turbine 5 as shown in FIG. Figure 3 Then turn off the backlight source 1, turn on the ring light 2, and take the second image to obtain the tooth profile image of the turbine 5 as shown in Figure 4 The control device is used to execute the device detection method based on frequency domain analysis. For a detailed description of the method, please refer to the corresponding description in the following method embodiment, which will not be repeated here.

[0058] Example 2

[0059] The detection method corresponding to the device detection apparatus based on frequency domain analysis in Example 1 is as follows: Figure 2 As shown, the following steps are included:

[0060] A contour image of a device to be inspected is acquired, wherein the device to be inspected is a turbine or a gear, etc. In this embodiment, a turbine is used as the device to be inspected for exemplary description.

[0061] When the device to be inspected is a turbine, obtaining a contour image of the device to be inspected includes the following steps:

[0062] Get the outer contour image of the turbine. The outer contour image of the turbine is as follows: Figure 3 shown.

[0063] Get the turbine tooth profile image. The turbine tooth profile image is as follows: Figure 4 shown.

[0064] It should be noted that, because the gear teeth are not spiral, the outer contour image captured using backlighting can not only obtain the center of the gear but also the contour of the gear, so there is no need to capture the tooth contour image.

[0065] By setting the threshold, the spot area is obtained from the contour image; Figure 3 In the outer contour image of the turbine shown in the figure, the spot area of ​​the turbine is obtained by setting the threshold. For example, if the threshold is set to 100, the brightness of the pixels inside the turbine is lower than the threshold, and the brightness of the pixels outside the turbine is higher than the threshold. The pixels with brightness lower than the threshold are set as the foreground, and the pixels with brightness higher than the threshold are set as the background. The final effect is as follows: Figure 5 As shown in the gray outline, the inside is the foreground and the outside is the background.

[0066] The center of the circle obtained by fitting the contour points is the center point of the device to be tested; specifically, the following steps are included:

[0067] Calculate the zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point;

[0068] Suppose there are M foreground points, and calculate their 0th to 2nd order moment parameters:

[0069] m00=M

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] The center position of the circle is obtained by combining the calculated zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point with the center of gravity calculation formula;

[0079] The spot is approximately a circle. According to the center of gravity calculation formula, the rough position of the center of the circle (x0, y0) can be obtained:

[0080]

[0081] The rough value of the radius is obtained by combining the calculated zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point with the radius calculation formula;

[0082] The radius can be roughly calculated by the following formula:

[0083]

[0084] Take points at equal angles around the circumference, for example, 360 points. These 360 ​​points are all near the edge of the actual spot's contour. At each point, measure along the line connecting that point and the center of the circle. For example, using a caliper tool, you can obtain the precise edge point of the contour, ultimately obtaining 360 precise contour points.

[0085] Using these precise contour points to fit a circle, the final precise center of the circle is the center of the turbine (x c ,y c In this embodiment, the least square method is used to fit the circle, and the square distance from each contour point (x, y) to the circle is |(xx c ) 2 +(yy c ) 2 -r 2 |, minimize By setting a suitable ratio of external points (e.g. 10%), the interference of noise or background dirt can be removed, and the precise center (x c ,y c ).

[0086] Since the turbine did not move when the outer contour image of the turbine and the tooth contour image of the turbine were taken, the center of the turbine in the tooth contour image of the turbine coincides with the center of the turbine in the outer contour image of the turbine, and the turbine spot area obtained in the outer contour image of the turbine is the turbine spot area in the tooth contour image of the turbine.

[0087] In the spot area, a spot image of the tooth profile is obtained by setting a threshold value; in the spot area of ​​the tooth profile image of the device to be detected, by setting a threshold value, for example, 100, all points with a grayscale less than the threshold value are inside the tooth, and all points with a grayscale greater than the threshold value are outside the tooth, and a spot image of the tooth profile can be obtained, such as Figure 6 shown.

[0088] exist Figure 6In the figure, every pixel in the white area is inside the tooth profile. Taking the center point of the turbine as the starting point and each point inside the gear as the end point, a vector can be determined, and the direction of the vector is within 0 to 360 degrees. By setting a reasonable angle interval, such as 0.05 degrees, 360 degrees can be divided into many parts. Taking the angle interval of 0.05 degrees as an example, 360 degrees are divided into 7200 parts. Create a histogram with a length of 7200 and initialize all elements in the histogram to 0. Scan all pixels inside the tooth profile, calculate the angle between it and the center point, and add 1 to the corresponding element in the histogram. After scanning all points inside the tooth profile, the angular statistical histogram of the turbine is obtained. Due to the periodic distribution of the teeth, the element corresponding to each tooth top in the histogram will be larger than the adjacent position, and the element corresponding to the tooth bottom will be less than the adjacent position, such as Figure 7 shown.

[0089] Perform Fourier transform on the angle statistical histogram to obtain the spectrum of the histogram, whose amplitude is as follows Figure 8 shown.

[0090] In the first half, the index of the harmonic with the largest amplitude (maxIndex) corresponds to the number of teeth of the turbine. Figure 8 In the first half, excluding the fundamental wave, the harmonic with the largest amplitude is the 11th harmonic (maxIndex = 11), so the turbine has 11 teeth. Then determine the vector from the center point of the turbine to the first tooth tip, and take the spectrum value corresponding to the 11th harmonic. The spectrum value corresponding to the 11th harmonic is a complex number. Let its real and imaginary parts be vecX and vecY respectively. Then the angle of the vector is

[0091]

[0092] Using the angle angle and the number of gears maxIndex, the angles of all tooth tops and tooth bottoms can be calculated. The angular interval between two adjacent tooth tops is 360 / maxIndex, and the angular interval between adjacent tooth tops and tooth bottoms is 180 / maxIndex.

[0093] Combining the center point of the turbine and each angle value, a set of rays can be obtained. The intersection of all the rays corresponding to the tooth tops and the tooth profile is the position of the tooth top, and the intersection of all the rays corresponding to the tooth bottoms and the tooth profile is the position of the tooth bottom. Figure 9 As shown, the gray curve represents the tooth profile, the point at the convex position represents the position of the tooth top, and the point at the concave position represents the position of the tooth bottom.

[0094] Combining the magnification of the telecentric lens and the design standards of the turbine, the physical distance from each tooth top or tooth bottom to the turbine center is obtained, which serves as reference data for turbine quality inspection;

[0095] In addition, it is also possible to determine whether the tooth pitch, tooth thickness and tooth groove width of the device to be tested meet the design standards.

[0096] It should be noted that the above method is not only suitable for the detection of turbines, but also for the detection of gears waiting to be detected.

[0097] The present invention adopts contactless measurement. By taking pictures of the turbine, various parameters of the turbine, such as the number of turbine teeth, the distance from the top of the tooth to the center, and the distance from the bottom of the tooth to the center, can be measured. Compared with contact measurement, the measurement efficiency is greatly improved. Combined with the automatic loading and unloading device, it is possible to inspect all products that need to be inspected, rather than just doing sampling inspections. Compared with existing contactless measurement solutions, since the present invention uses the method of combining angle histograms with frequency domain analysis, it uses all points inside the tooth profile and can be insensitive to noise and defects. Existing contactless measurement solutions only use points on the profile, and slight changes in the profile will cause deviations in the measurement results.

[0098] Example 3

[0099] An electronic device, comprising: Figure 10 As shown, a memory stores program code; a processor is connected to the memory, and when the program code is executed by the processor, a device detection method based on frequency domain analysis is implemented. For a detailed description of the method, please refer to the corresponding description in the above method embodiment, and will not be repeated here.

[0100] Example 4

[0101] A computer-readable storage medium such as Figure 11 As shown, program instructions are stored thereon, and when the program instructions are executed, a device detection method based on frequency domain analysis is implemented. For a detailed description of the method, reference can be made to the corresponding description in the above method embodiment, which will not be repeated here.

[0102] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0103] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0104] The above are merely examples of the present invention and are not intended to limit one or more embodiments of the present invention. For those skilled in the art, various changes and modifications may be made to one or more embodiments of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of one or more embodiments of the present invention shall be included within the scope of the claims of one or more embodiments of the present invention.

Claims

1. A device detection method based on frequency domain analysis, characterized in that: The following steps are involved: Acquire a contour image of the device to be inspected; Obtaining a spot area from the contour image by using a set threshold; The center of the circle obtained by fitting the contour points is the center point of the device to be tested; In the spot area, a spot image of the tooth profile is obtained by using a set threshold; The vector direction inside the tooth profile is evenly divided by the set angular interval. The vector is a vector determined by taking the center point of the device to be detected as the starting point and each point inside the gear as the end point; Scan all points inside the tooth profile, calculate the angle between the points inside the tooth profile and the center point, and obtain the angle statistical histogram of the device to be tested; Performing Fourier transform on the angle statistical histogram to obtain a frequency spectrum of the histogram; The index of the harmonic with the largest amplitude is obtained from the spectrum diagram of the histogram as the number of teeth of the device to be detected; Calculate the angles of all tooth tops and tooth bottoms using the spectrum value corresponding to the harmonic with the largest amplitude; A set of rays is obtained by the center point of the device to be tested, the angle of the tooth top and the angle of the tooth bottom. The intersection of the rays corresponding to all tooth tops and the tooth profile is the position of the tooth top, and the intersection of the rays corresponding to all tooth bottoms and the tooth profile is the position of the tooth bottom. The step of obtaining the contour image of the device to be detected comprises the following steps: Acquire an outer contour image of the device to be inspected; Acquire a tooth profile image of the device to be inspected; Calculating the angles of all tooth tops and tooth bottoms using the spectrum value corresponding to the harmonic with the largest amplitude includes the following steps: Get the spectrum value corresponding to the harmonic with the largest amplitude. The angle of the vector is: ， Where vecX is the real part of the spectrum value corresponding to the harmonic with the largest amplitude, vecY is the imaginary part of the spectrum value corresponding to the harmonic with the largest amplitude, and maxIndex is the number of teeth; Calculate the angles of all tooth tops and tooth bottoms based on the angle of the spectrum value corresponding to the harmonic with the largest amplitude and the number of teeth; the angular interval between two adjacent tooth tops is 360 / maxIndex; The following steps are also included: Combining the magnification of the telecentric lens and the design standards of the device to be tested, the physical distance from each tooth top or tooth bottom to the center of the device to be tested is obtained, which serves as reference data for quality inspection of the device to be tested. Determine whether the tooth pitch, tooth thickness and tooth groove width of the device to be tested meet the design standards.

2. The device detection method based on frequency domain analysis according to claim 1, wherein: The acquiring of the spot area map from the contour image by using the set threshold value specifically involves acquiring the spot area of ​​the device to be detected from the outer contour image of the device to be detected by using the set threshold value; The step of acquiring the spot image of the tooth profile within the spot region by using a set threshold value specifically involves acquiring the spot image of the tooth profile within the spot region of the tooth profile image of the device to be inspected by using a set threshold value.

3. The device detection method based on frequency domain analysis according to claim 1, wherein: The step of obtaining the spot area map from the contour image by setting the threshold value includes setting the pixel points in the contour image with brightness lower than the threshold value as the foreground, and setting the pixel points in the contour image with brightness higher than the threshold value as the background.

4. The device detection method based on frequency domain analysis according to claim 3, characterized in that: The method of fitting a circle by contour points to obtain the center of the circle as the center point of the device to be detected comprises the following steps: Calculate the zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point; The rough position of the circle center is obtained by combining the calculated zero-order moment parameters, first-order moment parameters and second-order moment parameters of the foreground point with the center of gravity calculation formula; The rough value of the radius is obtained by combining the calculated zero-order moment parameter, first-order moment parameter and second-order moment parameter of the foreground point with the radius calculation formula; Take points at equal angles on the circumference, and measure along the line connecting each point and the center of the circle to obtain accurate contour edge points. The least square method is used to fit a circle according to the edge points of the contour, and the obtained precise center of the circle is the center of the device to be detected.

5. The device detection method based on frequency domain analysis according to claim 4, characterized in that: The method of fitting a circle by contour points to obtain a center point of the circle as the center point of the device to be detected further comprises the following steps: By setting the ratio of external points, the interference of noise or background dirt is removed to obtain the center point.

6. A device detection device based on frequency domain analysis, characterized in that: include: A camera, a telecentric lens, a ring light, a backlight source, and a control device, wherein the backlight source is used to provide a light source from the bottom of the device to be detected, the ring light is used to provide a light source from the top of the device to be detected, the camera and the telecentric lens are used to capture an image of the device to be detected, and the control device is used to execute the device detection method based on frequency domain analysis as described in claim 1.

7. An electronic device, characterized in that: include: a memory having program code stored therein; A processor is coupled to the memory and implements the method according to any one of claims 1 to 5 when the program code is executed by the processor.

8. A computer-readable storage medium, characterized in that Program instructions are stored thereon, and when the program instructions are executed, the method according to any one of claims 1 to 5 is implemented.

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