A method for calculating the pendulum angle of a centrifugal pendulum shock absorber based on machine vision

Abstract

The present invention discloses a method for calculating the angle of a centrifugal pendulum shock absorber based on machine vision. Based on machine vision, a dark-filled circle attached to a central disk and a pendulum block is used as a marker, and a high-speed shooting device is used to shoot the rotation process of the centrifugal pendulum shock absorber, and image preprocessing, edge recognition, circle judgment, and circle center calculation are performed to finally obtain the angle of the pendulum block. The advantages of the present invention are that the calculation of the pendulum block rotation angle during the rotation of the CPVA is performed in a non-contact manner, the angle calculation is performed quickly and conveniently, the installation of cumbersome sensors is omitted, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of shock and vibration, and in particular to a method for calculating the angle of a pendulum block of a centrifugal pendulum shock absorber based on machine vision. Background Art

[0002] The centrifugal pendulum shock absorber (CPVA) is installed between the engine output shaft and the transmission input shaft to reduce the torsional vibration caused by the engine ignition. At present, studying the motion law of the pendulum block on the centrifugal pendulum shock absorber is an important direction for optimizing the shock absorber. By establishing a mathematical model of the centrifugal pendulum shock absorber, the dynamic characteristics of the shock absorber under different structures and masses are analyzed. At this time, it is necessary to observe the actual motion of the pendulum block. In the past, it was usually measured by sensors, which were cumbersome to install, costly, and poor in reusability. Non-contact measurement methods are a good choice to solve this problem. With the continuous development of machine vision technology, the use of machine vision methods to achieve displacement and angle measurement of moving and rotating objects has attracted more and more attention, and related technologies have become more and more mature. Therefore, using machine vision methods and non-contact measurement methods is an effective means to analyze the motion law of the pendulum block of the centrifugal pendulum shock absorber. This is where this application needs to focus on improvement. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for calculating the angle of the pendulum block of a centrifugal pendulum shock absorber based on machine vision, to perform non-contact measurement of the rotation angle of the pendulum block relative to the centrifugal pendulum during the rotation of the centrifugal pendulum shock absorber, and there is no need to install additional sensors during the analysis of the movement law of the pendulum block.

[0004] In order to solve the above technical problems, the present invention provides a method for calculating the pendulum block angle of a centrifugal pendulum shock absorber based on machine vision. Based on machine vision, a dark-filled circle attached to the central disk and the pendulum block is used as a marker, and a high-speed shooting device is used to shoot the rotation process of the centrifugal pendulum shock absorber, and image preprocessing, edge recognition, circle judgment, and circle center calculation are performed to finally obtain the pendulum block angle, including the following steps:

[0005] S1: Arrange multiple circular markers on the centrifugal pendulum and shoot a video;

[0006] S2: Import the video into Matlab to preprocess the image and identify edges;

[0007] S3: edge computing and circle judgment and circle center calculation;

[0008] Calculate the maximum horizontal width and height of the closed figure and determine whether the two are close. The threshold is 0.9. If the two are close, it is judged to be a circle.

[0009] S4: Calculate the angle based on the center of the circle;

[0010] Take out the graphic ID judged as a circle, and calculate the center and area of ​​the circle according to the edge coordinates of the graphic, and determine which pendulum block or central disk the circle is on; calculate the angle based on the obtained circle.

[0011] Preferably, a high-speed camera is used to shoot the rotation process of the centrifugal pendulum shock absorber, with a frame rate of more than 800 frames, so as to capture the movement of the rapidly rotating centrifugal pendulum and the pendulum mass.

[0012] Step S1 specifically includes:

[0013] S11: Arrange four dark circular markers at equal angles on the central disc of the centrifugal pendulum shock absorber, and the circular markers are of the same size;

[0014] S12: a dark circular marker is arranged at the center of each pendulum block, and the diameters of the circular markers are different and different from the diameter of the circular marker on the central disk. A high-speed camera shoots a video of the centrifugal pendulum shock absorber during movement.

[0015] The image preprocessing in step S2 includes image binarization and pixel inversion.

[0016] Step S3 specifically includes:

[0017] S31: Identify the edge of the image, that is, use Matlab's Edge function to determine the coordinates of the pixel value mutation in the image, and store them. Determine whether there is a closed figure based on the continuity of the coordinates, that is, start from a certain coordinate, find the adjacent coordinates in order, and finally return to the coordinate, that is, determine it as a closed figure, calculate the pixel width and pixel height of the figure, and save the graphic ID, corresponding height, width and center data of the two close figures.

[0018] Step S4 specifically includes:

[0019] S41: The sizes of the central disk and the circular markers on each pendulum block are stored in advance, and the position is determined according to the height and width of the saved graphics obtained in step S3, that is, the position is determined according to the size;

[0020] S42: according to the center positions of the four circular markers on the central disk obtained in the above steps, the coordinates of the intersection of the central disk rotation axis and the central disk are calculated as the center coordinates of the disk;

[0021] S43: Calculate the angle according to the coordinates of the center of the circular marker on each pendulum block, the coordinates of the center of the circular marker on the nearest left central disk, and the coordinates of the disk center. Calculate the swing angle by the difference between the maximum and minimum values ​​of the angle. Take the minimum angle value plus half of the swing angle as the angle of the pendulum block at the center. Subtract the angle between the pendulum block and the center from the current angle value to obtain the rotation angle of the pendulum block relative to the centrifugal pendulum.

[0022] The superior effects of the present invention are:

[0023] 1) Using machine vision to calculate the angle of the pendulum during the CPVA rotation process not only makes angle calculation quick and convenient, but also facilitates the analysis and optimization of CPVA;

[0024] 2) The application method is a non-contact measurement, which eliminates the cumbersome installation of sensors and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. 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:

[0026] Figure 1 It is a schematic diagram of a flow chart of an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the arrangement of circular markers according to an embodiment of the present invention;

[0028] Description of the symbols in the figure

[0029] 1—center disk; 101—circular marker A;

[0030] 2—Pendulum block B; 201—Circular marker;

[0031] 3—Pendulum block C; 301—Circular marker;

[0032] 4—Pendulum block D; 401—Circular marker;

[0033] 5—Pendulum block E; 501—Circular marker. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. This specific embodiment takes four pendulum blocks as an example.

[0035] Figure 1 A schematic diagram of a process flow of an embodiment of the present invention is shown; Figure 2 FIG. 2 shows a schematic diagram of the arrangement of circular markers in an embodiment of the present invention. Figure 1 and Figure 2As shown, the present invention provides a method for calculating the pendulum angle of a centrifugal pendulum shock absorber based on machine vision, comprising the following steps:

[0036] S1: Video acquisition of the rotation process of the centrifugal pendulum shock absorber based on markers;

[0037] S11: according to the size of the centrifugal pendulum, stickers are made, including stickers for the central disk of the centrifugal pendulum and stickers for the four pendulum blocks. Four black filled circles A101 of equal size and equiangular spacing are drawn on the sticker of the central disk 1, and black filled circles 201, 301, 401, 501 of different sizes from the circle A101 and of different sizes are drawn at the centers of the stickers of the four pendulum blocks B2, C3, D4, and E5; and the sizes of the circular markers A101, 201, 301, 401, 501 are stored;

[0038] S12: Install the centrifugal pendulum on the engine flywheel, and ensure that the axis of the centrifugal pendulum is consistent with the axis of the flywheel during installation, and the surfaces of the two are in contact during installation; during the movement of the centrifugal pendulum, the center disk 1 rotates with the flywheel, and the four pendulum blocks B2, C3, D4, and E5 rotate around the axis of the center disk 1. The rotation rate of the pendulum blocks is inconsistent with that of the center disk 1, and there is a speed difference. Use a high-speed camera to shoot a video;

[0039] S2: Image import and preprocessing;

[0040] S21: Import the captured video frame by frame into Matlab to preprocess the image;

[0041] To enhance the image, the image is input into Matlab as a matrix. If the average value of the elements in the matrix is ​​less than the threshold value of 90, all the elements of the matrix are multiplied by 1.2 to make the image brighter and clearer.

[0042] S3: edge computing and circle judgment and circle center calculation;

[0043] S31: Use Matlab function Edge to calculate the pixel coordinates of the pixel value mutation in the image and save them;

[0044] S32: Starting from any coordinate, traverse the adjacent pixel coordinates saved above in a clockwise or counterclockwise direction. If the coordinate is finally returned, it is judged as a closed figure. At this time, the maximum horizontal pixel width and height of the figure are calculated. Whether the figure is a circle is determined based on whether the aspect ratio exceeds the threshold value of 0.9. The center coordinates of the circle are calculated based on the edge coordinates of the circle. The center coordinates of the circumscribed circle are calculated based on the coordinates of any three points on the circle, and the pixel width, ID, and center coordinates of the circle are saved.

[0045] S4, calculate the angle based on the circle;

[0046] S41: determining the position of the circle according to the circle size in step 3, the circle ID and its pixel width saved in step 3;

[0047] S42: Calculate the coordinates of the intersection of the disk rotation axis and the disk according to the obtained center positions of the four circles A101 on the central disk 1 as the center coordinates of the disk, that is, select three of the center coordinates of the four circles A101 and calculate the center coordinates of their circumscribed circles;

[0048] S43: Take block B2 as an example. Figure 2 As shown, the center coordinates of the circular marker on the pendulum block B2 and the center coordinates of the circular marker A101 on the nearest left central disk 1 and the disk center coordinates obtain a minimum angle value α3; when the pendulum block B2 centrifugally moves to the extreme position, the maximum angle value α1 is obtained. Figure 2 The dotted line in the figure is the motion trajectory of the pendulum block B2; the difference between the maximum angle value α1 and the minimum angle value α3 is the swing angle θ, and the minimum value α3 plus half of the swing angle 0.5θ is taken as the angle at the center of the pendulum block B2. , minus the current angle value γ As the angle between the pendulum block B2 and the center The angle difference β is β, where β is the rotation angle of the pendulum block B2 relative to the centrifugal pendulum;

[0049] S44: According to the step of S43, the rotation angles of the pendulum blocks C3, D4, and E5 relative to the centrifugal pendulum are calculated. Because the circular markers on the four pendulum blocks are of different sizes, it is possible to accurately locate which pendulum block has the rotation angle relative to the centrifugal pendulum.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating the pendulum angle of a centrifugal pendulum shock absorber based on machine vision, characterized in that: Based on machine vision, the dark-filled circles attached to the center disk and the pendulum block are used as markers. High-speed shooting equipment is used to shoot the rotation process of the centrifugal pendulum shock absorber, and image preprocessing, edge recognition, circle judgment, and circle center calculation are performed to finally obtain the pendulum block angle, including the following steps: S1: Arrange multiple circular markers on the centrifugal pendulum and shoot a video; S11: Arrange four dark circular markers at equal angles on the central disc of the centrifugal pendulum shock absorber, and the circular markers are of the same size; S12: Arranging a dark circular marker at the center of each pendulum block, wherein the diameters of the circular markers are different and are different from the diameter of the circular marker on the central disk; S2: video import, image preprocessing and edge recognition; S3: edge computing and circle judgment and circle center calculation; S4: Calculate the angle based on the center of the circle; S41: The sizes of the central disk and the circular markers on each pendulum block are stored in advance, and the position is determined according to the height and width of the saved graphics obtained in step S3; S42: according to the center positions of the four circular markers on the central disk obtained above, the coordinates of the intersection of the central disk rotation axis and the central disk are calculated as the center coordinates of the disk; S43: Calculate the angle according to the coordinates of the center of the circular marker on each pendulum block, the coordinates of the center of the circular marker on the nearest left central disk, and the coordinates of the center of the disk, and calculate the swing angle according to the maximum and minimum values ​​of the angle, and take the minimum angle value plus half of the swing angle as the angle of the pendulum at the center, and subtract the angle of the pendulum at the center from the current angle value to obtain the rotation angle of the pendulum relative to the centrifugal pendulum.

2. The method for calculating the pendulum block angle of a centrifugal pendulum shock absorber based on machine vision according to claim 1, characterized in that: The step S3 specifically includes: S31: Identify the edge of the image, determine the coordinates of the pixel value mutation in the image and store them; S32: Determine whether there is a closed figure based on the continuity of the coordinates, that is, starting from a certain coordinate, finding the adjacent coordinates in order, and finally returning to the coordinate, and then determining it as a closed figure. S33: Calculate the maximum horizontal pixel width and pixel height of the closed figure, and save the figure ID, corresponding height, width and figure center data of the two close figures.

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