JP2014130084A - Tire analysis system and analysis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire analysis system enabling highly accurate analysis, and an analysis method.SOLUTION: An analysis method includes: a step ST2 of photographing an image at the time when a plurality of grating patterns engraved on a tire are respectively at predetermined positions; a step ST7 of calculating a space coordinate of the grating pattern by performing shape analysis with a photographed image; a step of detecting variation of the arrangement of the grating pattern on the basis of the space coordinate; and a step ST8 of correcting the arrangement of the grating pattern on the basis of the variation.

Description

  The present invention relates to a tire analysis system and an analysis method, and more particularly to a tire analysis system and an analysis method capable of realizing a highly accurate analysis.

  Conventional tire analysis systems perform tire shape analysis using digital images obtained by continuously photographing test tires using a high-speed video camera. As such conventional tire analysis apparatuses, techniques described in Patent Documents 1 and 2 are known.

JP 2011-27509 A JP 2011-237258 A

  An object of the present invention is to provide a tire analysis system and an analysis method capable of realizing a highly accurate analysis.

  In one aspect, the analysis system performs shape analysis using an imaging unit that captures an image when each of the plurality of lattice patterns attached to the tire is at a predetermined position, and an image captured by the imaging unit. A spatial coordinate calculation unit that calculates a spatial coordinate of the lattice pattern by performing a variation detection unit that detects a variation in the arrangement of the lattice pattern based on the spatial coordinate, and an arrangement of the lattice pattern based on the variation. A correction unit for correcting.

  In another aspect, the analysis method includes a step of taking an image when each of the plurality of lattice patterns attached to the tire is in a predetermined position, and performing shape analysis using the image to thereby analyze the lattice pattern. Calculating a spatial coordinate; detecting a variation in the arrangement of the lattice pattern based on the spatial coordinate; and correcting the arrangement of the lattice pattern based on the variation.

  The analysis system and the analysis method can realize highly accurate analysis in one aspect.

FIG. 1 is a configuration diagram illustrating a tire analysis system according to an embodiment. FIG. 2 is a block diagram illustrating functions of the tire analysis apparatus described in FIG. 1. FIG. 3 is a diagram illustrating an example of variation in the arrangement of the analysis lattice plane. FIG. 4 is a flowchart showing an analysis method by the tire analysis system. FIG. 5 is a diagram illustrating an example of values obtained by an analysis method using a tire analysis system. FIG. 6 is a diagram illustrating an example of fluctuations in the Y coordinate of the center of the lattice of the analysis lattice plane before correction. FIG. 7 is a diagram illustrating an example of fluctuations in the Y coordinate of the center of the lattice of the analytical lattice plane after correction.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Tire analysis system]
FIG. 1 is a configuration diagram showing a tire analysis system according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating functions of the tire analysis device of the tire analysis system illustrated in FIG. 1. In these drawings, FIG. 1 schematically shows the overall configuration of the tire analysis system, and FIG. 2 shows the main functions of the tire analysis apparatus.

  The tire analysis system 1 performs tire behavior analysis (for example, vibration measurement) by measuring a displacement applied to the tire central axis when a predetermined condition is input, a change in tire shape, a change in tire surface distortion, and the like. Applies to the system. The tire analysis system 1 includes a tire testing machine 2, an imaging device 3, and a tire analysis device 4 (see FIG. 1).

  The tire testing machine 2 is an apparatus that imparts test conditions to the test tire, and includes, for example, a drum type tire testing machine, a belt type tire testing machine, and the like. In the configuration of FIG. 1, the tire testing machine 2 is a drum type tire testing machine, and includes a support device 21 and a driving device 22. The support device 21 is a device that rotatably supports the test tire 10 and includes a rim 211 on which the test tire 10 is mounted. The driving device 22 is a device that applies a driving force to the test tire 10, and includes a rotating drum 221, a motor 222 that drives the rotating drum 221, and a motor control device 223 that drives and controls the motor 222.

  In the tire testing machine 2, the support device 21 mounts and supports the test tire 10 on the rim 211, and presses the test tire 10 against the rotating drum 221 of the driving device 22 to apply a load to the test tire 10. In addition, the support device 21 displaces the rim 211 to adjust the positional relationship between the test tire 10 and the rotating drum 221, thereby giving the test tire 10 a slip angle or an angle angle. Further, the drive device 22 drives the motor 222 by the motor control device 223 to rotate the rotating drum 221, thereby giving the test tire 10 a rotational speed. As a result, the rolling state of the tire during vehicle travel is reproduced with the circumferential surface of the rotating drum 221 as the road surface. In addition, the test conditions can be changed by the support device 21 and the drive device 22 adjusting the load, rotation speed, slip angle, angle angle, and the like.

  The imaging device 3 includes a pair of cameras 31 and 31 and a pair of illumination lamps 32 and 32. The camera 31 is a means for imaging the test tire 10, and is constituted by, for example, a CCD (Charge Coupled Device) camera. The camera 31 is, for example, a high speed camera. Moreover, a pair of cameras 31 and 31 are arrange | positioned in the position which can image the test tire 10 from a mutually different direction. These cameras 31 and 31 simultaneously image the test tire 10 from the left-right direction to generate a tire image (digital image data of the test tire 10). The illumination lamp 32 is a lamp that illuminates the imaging range of the camera 31, and is composed of, for example, a halogen lamp. These illumination lamps 32 may be a constantly lit type or a flash lit type.

  The tire analysis device 4 is, for example, a PC (personal computer) in which a predetermined analysis program is installed, and performs tire analysis processing by performing image processing on the tire image from the imaging device 3 (see FIG. 2). The tire analysis device 4 includes a spatial coordinate calculation unit 41, a variation detection unit 42, an analysis unit 43, and a correction unit 44. The spatial coordinate calculation unit 41 calculates the spatial coordinates of the analysis lattice plane (lattice pattern) S attached to the test tire 10 in a circle by performing shape analysis using the tire image. The variation detector 42 detects variations in the arrangement of the analysis lattice plane S based on the calculated spatial coordinates. The analysis unit 43 performs a predetermined tire analysis process. The correction unit 44 corrects the arrangement of the analysis lattice plane S based on the variation detected by the variation detection unit 42 in order to improve the accuracy of analysis by the analysis unit 43.

[Tire analysis method]
Conventionally, a sampling moire method is known as a method for analyzing a tire shape at the time of tire rolling.

  The sampling moire method is a mathematical method for generating a moire fringe from a digital image and calculating a three-dimensional shape of an imaging target. This sampling moire method has an advantage that a highly accurate shape analysis can be performed.

  The tire analysis system 1 analyzes vibration (displacement with respect to the tire center axis) of the test tire 10 using shape analysis using a sampling moire method. Specifically, as shown in FIG. 1, a plurality of analysis lattice planes S (S # 1 to S # n) are provided in a circular shape on the tire circumference of the test tire 10. By applying the shape analysis using the sampling moire method to the image photographed while rotating the test tire 10, the spatial coordinates of the analysis lattice plane S at the time of tire rolling are calculated. By comparing the spatial coordinates thus calculated, the vibration of the test tire 10 can be analyzed.

  However, since there is a limit to the accuracy of the human pasting position, there may be variations in the arrangement of the analysis lattice plane S attached to the test tire 10. FIG. 3 is a diagram illustrating an example of variation in the arrangement of the analysis lattice plane S. FIG. FIG. 3 shows an image of the analysis lattice plane S # 1 in the tire image when the analysis lattice plane S # 1 is in a predetermined position and an analysis in the tire image when the analysis lattice plane S # 2 is in a predetermined position. The image of the lattice plane S # 2 for use is shown side by side.

  The analysis lattice plane S is a sheet on which marks having substantially the same shape are arranged with periodicity. On the analysis lattice plane S, at least two marks are arranged in the vertical direction and the horizontal direction, respectively. For example, the analysis lattice plane S has a plurality of circular marks arranged in a matrix at intervals of 2.5 [mm]. The shape, size, and interval of the marks are not limited to the example in FIG. The analysis lattice plane S is attached to the test tire 10 at substantially equal intervals so that a straight line connecting the center of each analysis lattice plane S and the test tire 10 is parallel to one of the mark arrangement directions. The

  In the example shown in FIG. 3, there is a Y-direction deviation (radial deviation) between the lattice center C1 of the analysis lattice plane S # 1 and the lattice center C2 of the analysis lattice plane S # 2. . The variation in arrangement may occur not only in the Y direction but also in the X direction (circumferential direction) and the Z-axis direction (width direction). The variation in arrangement may include an inclination component. Such variation in the arrangement affects the comparison of the calculated spatial coordinates, and reduces the accuracy of the analysis based on the comparison.

  In order to attach the analysis lattice plane S to the tire circumference of the test tire 10, the analysis lattice plane S is fixed to the rim 211 or an annular disk 212 attached to the end of the rim 211 at a relatively small deformation portion. May be. In this case, as compared with the case where the analysis lattice plane S is fixed to the rubber portion of the test tire 10, the displacement of the analysis lattice plane S relative to the tire central axis when the test tire 10 is rotated is relatively small. In order to perform highly accurate analysis based on such a small displacement, it is very important to eliminate as much as possible the influence of variation in the arrangement of the analysis lattice plane S.

  Therefore, the tire analysis system 1 detects a variation in the arrangement of the analysis lattice plane S, and corrects the calculated spatial coordinates based on the detected variation.

  FIG. 4 is a flowchart showing an analysis method by the tire analysis system 1. FIG. 5 is a diagram illustrating an example of values obtained by the analysis method by the tire analysis system 1.

  In step ST1, the tire testing machine 2 rotates the test tire 10 provided with a plurality of analysis lattice planes S on the tire circumference without applying a load. If the test tire 10 is rotated without applying a load, the test tire 10 does not vibrate.

  In this state, in step ST2, the imaging device 3 uses the pair of cameras 31 and 31 to simultaneously image the analysis lattice plane S attached to the test tire 10 from the left and right directions. Specifically, the imaging device 3 each time each of the turning analysis lattice planes S reaches a predetermined position (for example, a position where the test tire 10 and the road surface or a surface imitating the road surface contact). Photographing is performed to obtain a pair of tire images.

  In this way, by photographing the analysis lattice plane S from different angles with a plurality of cameras, the coordinates in the tire width direction (depth direction) can also be measured. Furthermore, by using a plurality of cameras, it is possible to correct measurement errors due to distortion of camera lens.

  In step ST3, the spatial coordinate calculation unit 41 performs shape analysis using the sampling moire method for each pair of tire images, and calculates the spatial coordinates of the analysis lattice plane S in the image. In step ST <b> 4, the variation detection unit 42 detects variations in the arrangement of the respective analysis lattice planes S based on the spatial coordinates calculated by the spatial coordinate calculation unit 41.

  In the present embodiment, as shown in FIG. 3, the spatial coordinate calculation unit 41 detects the Y-direction deviation as a variation based on the coordinates of the center of the lattice of the analysis lattice plane S. In the example shown in FIG. 5, based on the spatial coordinates calculated by the spatial coordinate calculation unit 41, the Y coordinate of the center of the lattice of each analysis lattice plane S is calculated. Then, the displacement in the Y direction with respect to the Y coordinate at the center of the analysis lattice plane S # 1 is calculated as the Y direction displacement. The Y coordinate of the center of the lattice of each analysis lattice plane S may be an average value of Y coordinates calculated from a plurality of images.

  The method of detecting the variation in arrangement is not limited to this. The spatial coordinate calculation unit 41 may detect a deviation in the X direction (circumferential direction), the Z direction (width direction), or an arbitrary direction as a variation. The spatial coordinate calculation unit 41 may detect a deviation in a plurality of directions as variations. The spatial coordinate calculation unit 41 may detect a variation in inclination in addition to or instead of such a positional deviation.

  The reference position for detecting the variation in arrangement is not limited to the center of the lattice of the analysis lattice plane S. The reference position may be a position where the spatial coordinates can be calculated with high accuracy by shape analysis. Specifically, as long as the number of pixels per period of the grid does not change suddenly, a position other than the center may be used as a reference in the area inside the grid of the analysis grid plane S.

  After the variation in arrangement is thus detected, in step ST5, the tire testing machine 2 rotates the test tire 10 with a load applied. The load to be applied is determined according to the purpose of analysis.

  In this state, in step ST6, the imaging device 3 uses the pair of cameras 31 and 31 to simultaneously image the analysis lattice plane S attached to the test tire 10 from the left and right directions. Specifically, the imaging device 3 each time each of the turning analysis lattice planes S reaches a predetermined position (for example, a position where the test tire 10 and the road surface or a surface imitating the road surface contact). Photographing is performed to obtain a pair of tire images.

  In step ST7, the spatial coordinate calculation unit 41 performs shape analysis using the sampling moire method for each pair of tire images, and calculates the spatial coordinates of the analysis lattice plane S in the image. In step ST8, the correction unit 44 corrects the spatial coordinates of each analysis lattice plane S based on the variation detected in step ST4.

  In the example shown in FIG. 5, based on the spatial coordinates calculated in step ST3 and the spatial coordinates calculated in step ST7, a value indicating the displacement of the Y coordinate at the center of the lattice when a load is applied is analyzed. It is calculated for each lattice plane S. And the value which shows a displacement is correct | amended by subtracting the Y direction shift | offset | difference calculated by step ST4 from the value which shows a displacement. From the value indicating the displacement of the Y coordinate of the center of the lattice of the analysis lattice plane S # 1, the Y-direction shift of the center of the lattice of the analysis lattice plane S # 1 is subtracted, and the lattice of the analysis lattice plane S # n From the value indicating the displacement of the Y coordinate at the center of Y, the Y direction deviation of the center of the lattice of the analysis lattice plane S # n is subtracted.

  In step ST9, the analysis unit 43 performs a predetermined analysis based on the spatial coordinates of the analysis lattice plane S after correction.

  In the above embodiment, an example in which the sampling moire method is used to calculate the spatial coordinates of the analysis lattice plane S has been described. However, the method for calculating the spatial coordinates of the analysis lattice plane S is not limited to this. The tire analysis system 1 may calculate the spatial coordinates of the analysis lattice plane S using a shape analysis method other than the sampling moire method. Examples of the shape analysis method other than the sampling moire method include a Fourier transform method and a digital image correlation method.

  In the above embodiment, an example in which the analysis method by the tire analysis system 1 is used for analysis of tire vibration has been described. However, the analysis applicable to the analysis method by the tire analysis system 1 is not limited to this. The analysis method by the tire analysis system 1 can be applied to any analysis related to the displacement or deformation of the tire.

  In the above embodiment, an example in which the imaging device 3 includes two cameras 31 has been described. However, the number of cameras 31 included in the imaging device 3 is not limited to this. For example, the number of cameras 31 included in the imaging device 3 may be one. That is, the tire analysis system 1 may capture an image with only one high-speed camera, and calculate the spatial coordinates of the analysis lattice plane S using a shape analysis method (sampling moire method, Fourier transform method, etc.).

[effect]
As described above, the tire analysis system 1 uses the imaging device 3 that captures an image when each of the plurality of lattice patterns attached to the tire is at a predetermined position, and the image captured by the imaging device 3. The spatial coordinate calculation unit 41 that calculates the spatial coordinates of the lattice pattern by performing shape analysis, a variation detection unit 42 that detects the variation in the arrangement of the lattice pattern based on the spatial coordinates, and the arrangement of the lattice pattern based on the variation The correction part 44 which correct | amends is provided.

  The spatial coordinate calculation unit 41 performs the shape analysis by a sampling moire method, for example.

  In such a configuration, the arrangement of the lattice pattern is accurately corrected based on the shape analysis, so that a highly accurate analysis is possible.

  6 and 7 are diagrams illustrating the effect of correcting the variation in arrangement. FIG. 6 shows an example of the fluctuation of the Y coordinate of the center of the lattice of the analysis lattice plane S before correction. FIG. 7 shows an example of fluctuations in the Y coordinate of the center of the lattice of the analytical lattice plane S after correction. As shown in FIG. 6, the fluctuation of the Y coordinate before correction has a large amplitude and a short period. On the other hand, as shown in FIG. 7, the Y-coordinate variation after correction has a small amplitude and a long period. In the example shown in FIG. 7, the amplitude of the fluctuation is reduced by about 80% compared to the example shown in FIG. Further, in the example shown in FIG. 7, the cycle of fluctuation matches the cycle of rotation of the test tire 10. As described above, the influence of the pasting position accuracy of the analysis lattice plane S is almost eliminated by correcting the variation in arrangement.

  In addition, the imaging device 3 includes a plurality of cameras that capture the lattice pattern from different angles, and the spatial coordinate calculation unit 41 performs lattice analysis by performing shape analysis using a plurality of images that are simultaneously captured by the plurality of cameras. Calculate the spatial coordinates of the pattern. Thereby, variation in arrangement in an arbitrary direction can be detected. Furthermore, the influence of distortion of the camera lens can be reduced.

  In addition, the variation detection unit 42 detects a variation in the arrangement of the grid pattern based on the spatial coordinates calculated by the spatial coordinate calculation unit 41 using an image taken in a state where no load is applied to the tire. Thereby, the variation in the arrangement of the lattice pattern can be detected with high accuracy.

  The lattice pattern is a pattern in which at least two marks are arranged in the first direction and the second direction, respectively. Thereby, a spatial coordinate can be calculated with high accuracy using shape analysis.

  1: tire analysis system, 2: tire testing machine, 21: support device, 211: rim, 212: annular disc, 22: drive device, 221: rotating drum, 222: motor, 223: motor control device, 3: imaging device , 31: camera, 32: illumination lamp, 4: tire analysis device, 41: spatial coordinate calculation unit, 42: variation detection unit, 43: analysis unit, 44: correction unit, 10: test tire

Claims (6)

An imaging unit that captures an image when each of the plurality of lattice patterns attached to the tire is in a predetermined position;
A spatial coordinate calculation unit that calculates a spatial coordinate of the lattice pattern by performing shape analysis using an image captured by the imaging unit;
A variation detecting unit that detects variations in the arrangement of the lattice pattern based on the spatial coordinates;
A correction unit that corrects the arrangement of the lattice pattern based on the variation;
An analysis system comprising:   The analysis system according to claim 1, wherein the spatial coordinate calculation unit performs the shape analysis by a sampling moire method. The imaging unit has a plurality of cameras that capture the lattice pattern from different angles,
The analysis system according to claim 1, wherein the spatial coordinate calculation unit calculates the spatial coordinates of the lattice pattern by performing shape analysis using a plurality of images simultaneously captured by the plurality of cameras.   2. The variation detection unit detects variation in the arrangement of the lattice pattern based on the spatial coordinates calculated by the spatial coordinate calculation unit using the image taken in a state where no load is applied to the tire. 4. The analysis system according to any one of items 1 to 3.   The analysis system according to any one of claims 1 to 4, wherein the lattice pattern is a pattern in which at least two marks are arranged in each of the first direction and the second direction. Capturing an image when each of the plurality of lattice patterns attached to the tire is in a predetermined position;
Calculating spatial coordinates of the lattice pattern by performing shape analysis using the captured image;
Detecting a variation in the arrangement of the lattice pattern based on the spatial coordinates;
Correcting the arrangement of the lattice pattern based on the variation;
An analysis method comprising:

Images