JP2011179884A - Method and system for measuring tire skid speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a skid speed generated on a tire tread surface when a tire rolls since it is difficult to accurately grasp a phenomenon occurring in the tire in a rolling state on an actual road surface from a measurement result because measurement is performed by artificially creating a state that a wheel is rolled on a road surface in a laboratory or the like including a measuring device. <P>SOLUTION: A tread surface of the tire 11 of a wheel W rolling on a road surface R is formed and an outer peripheral surface 16a and a road surface R of a block 16 positioned at the outermost periphery of the tread surface are photographed as identical screens, a relative distance between respective feature points set to the outer peripheral surface 16a and the road surface R of the block 16 on one screen is calculated from the photographed image, and then a skid speed of the block 16 is calculated based on a change in the relative distance by the comparison of the two screens. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tire slip speed measuring method and system, and in particular, a tire slip speed measuring method for measuring a tire slip speed based on image data obtained by photographing a tire tread surface and a contact surface during wheel rolling, and About the system.

2. Description of the Related Art Conventionally, as a device for measuring the slip amount of a tire in order to examine the slip speed of the tire of a wheel in a vehicle traveling by rolling the wheel on a road surface, for example, “a tire tread contact portion measuring device” (Patent Document) 1) is known.
"Tire tread grounding surface measuring device" is a tire in which rollers are placed side by side on a horizontal frame, the road surface with a transparent plate embedded is moved by a motor for movement, and the test tire is supported below the horizontal frame. By placing a support base and placing a TV camera fixed to the road surface above the transparent plate, a small area (for example, one block) can be photographed to fill the entire screen, and the amount of slip can be increased. Measure with accuracy.

Japanese Patent Laid-Open No. 7-63658

However, in the conventional “treading surface measurement device for tire treads”, measurement is performed by creating a state in which the wheel rolls on the road surface in a laboratory equipped with the measurement device. Therefore, it is difficult to accurately grasp the phenomenon that occurs in the tire that is actually rolling on the road surface, and the slip speed generated on the tire tread when the tire is in the rolling state is accurately measured. I couldn't.
The object of the present invention is to accurately measure the slip speed generated on the tire tread when the tire is in a rolling state by accurately grasping the phenomenon that occurs in the tire that is actually in a rolling state on the road surface. It is to provide a tire slip speed measuring method and system that can be used.

In order to achieve the above object, a tire slip speed measuring method according to the present invention forms a tread surface of a wheel tire that rolls on a road surface, and photographs the side surface of the block located on the outermost periphery of the tread surface and the road surface as the same screen. Processing, processing for calculating the relative distance of each feature point set on the side surface of the block and the road surface on one screen from the captured image, sliding speed of the block based on the change of the relative distance by comparing two screens Each process of the process which calculates is included.
Further, in the tire slip speed measuring method according to another aspect of the present invention, the calculation result obtained by calculating the change of the relative distance by comparing the slip speed of the block with the comparison of the two screens is displayed on the two screens. It is calculated by dividing by the time difference.

In order to achieve the above object, a tire slip speed measuring system according to the present invention includes a marker provided on a side surface of a block that forms a tire tread surface of a wheel that rolls on a road surface and is positioned on the outermost periphery of the tread surface, When rolling, the camera captures the side surface of the block and the road surface on the same screen, and the relative distance between the feature points set on the side surface of the block and the road surface on one screen from the image captured by the camera. A calculation unit that calculates and calculates a sliding speed of the block based on a change in the relative distance by comparing two screens.
Further, a tire slip speed measuring system according to another aspect of the present invention is attached to a vehicle body to which the wheel is mounted, and the camera having a photographing direction directed to a side surface of the block is arranged and held on a side of the wheel. It has a holding member.

According to the tire slip speed measuring method according to the present invention, the side surface and road surface of the block that forms the tire tread surface of the wheel rolling on the road surface and is located on the outermost periphery of the tread surface are photographed as the same screen. Calculate the relative distance between each feature point set on the side of the block and the road surface on one screen, and then calculate the sliding speed of the block based on the change of the relative distance by comparing the two screens. By accurately grasping the phenomenon occurring in the tire in the rolling state, the slip speed generated on the tire tread when the tire is in the rolling state can be accurately measured.
Moreover, the tire slip speed measuring system according to the present invention can realize the tire slip speed measuring method.

It is explanatory drawing which shows roughly the structure of the tire slip speed measuring system which concerns on one embodiment of this invention. It is explanatory drawing which shows the specific example of the tire slip speed measuring system of FIG. FIG. 1 conceptually shows a tire slip speed measuring method by the tire slip speed measuring system of FIG. The calculation method of a tire slip speed is shown notionally, (a) is explanatory drawing before a slip, (b) is explanatory drawing after a slip. FIG. 4 specifically shows a method of calculating the tire slip speed in FIG. 4, (a) is an explanatory diagram of measurement points, (b) is an explanatory diagram at the start of interval measurement, and (c) is an explanatory diagram at the end of interval measurement. .

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram schematically showing a configuration of a tire slip speed measuring system according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a specific example of the tire slip speed measuring system of FIG. FIG. 3 conceptually shows a tire slip speed measuring method by the tire slip speed measuring system of FIG. 1, (a) is an explanatory view of a tire rolling state, and (b) is an explanatory view of a photographed image.

  As shown in FIG. 1 and FIG. 2, the tire slip speed measuring system 10 measures the slip speed of the tire 11 constituting the wheel W in a vehicle C that travels by rolling the wheel W on the road surface R. From the marker 12 provided on the side surface of the tire 11, the high-speed camera 13 that photographs the road surface R together with the side surface of the tire 11, the holding member 14 that positions the high-speed camera 13 on the side of the tire 11, and the high-speed camera 13 A measurement unit 15 that measures tire slip speed based on the image data of the input captured image is provided.

  The marker 12 forms a tire tread surface (tread) in which the tire 11 comes into contact with the road surface R when the wheel W rolls on the road surface R. Is provided. The marker 12 is formed by regularly or randomly marking a plurality of fine dots (dot marks) at one or more locations on the outer surface 16a of the block 16 (see FIG. 2). In addition, you may form the outer surface 16a which marks a dot by the cut surface which cut | disconnected the block 16 along the tire circumferential direction cross section. When forming the marker 12, for example, the dots are painted white or the outer surface 16a excluding the dots is painted white so that the dots can be clearly distinguished from the outer surface 16a as the background.

  The high-speed camera 13 is, for example, a camera that can shoot several hundred to several tens of thousands of high-speed images per second, and the outside of the block 16 in contact with the road surface R when the wheel W rolls on the road surface R while the vehicle C is traveling. The side surface 16a and the road surface R can be photographed as the same screen, are spaced apart from the outer surface side of the wheel W and are arranged close to the road surface R, and the camera lens faces the outer surface 16a and the road surface R. ing. The high-speed camera 13 selects the lens to be used by calculating the required depth of field in order to ensure the shooting conditions necessary for obtaining the image data to be output to the calculation unit 15 under the camera placement conditions. To do.

In addition, lighting equipment (not shown) is installed in the vicinity of the high-speed camera 13 to illuminate the outer surface 16a of the block 16 to which the camera lens is directed and the road surface R to ensure brightness necessary for photographing. ing.
If the necessary shooting conditions can be ensured, shooting is performed with one high-speed camera 13. However, the high-speed camera 13 is not limited to one, for example, panoramic shooting using two cameras. Thus, high-resolution imaging that can obtain twice the resolution may be performed.

  The holding member 14 is attached to a vehicle body to which the wheel W is mounted via a suspension (not shown) that suspends the wheel W, and includes a first holding portion 14a that connects the suspension and the high-speed camera 13, and a first holding member 14a. It has the 2nd holding | maintenance part 14b which connects the holding | maintenance part 14a and the wheel W (refer FIG. 2).

  The first holding unit 14a includes measurement means (not shown) that measures the distance between the high-speed camera 13 and the road surface R, and the vehicle C is based on the measurement data of the camera-road distance obtained by the measurement means. When traveling, the high-speed camera 13 is held at an optimum height with a certain distance from the road surface R. The second holding portion 14b having one end attached to the first holding portion 14a has the other end attached to the wheel Ww of the wheel W via a connecting means 17 having a cross roller ring (see FIG. 2). The high-speed camera 13 can be positioned in an optimum direction corresponding to the turning displacement of the wheel W when the wheel W is steered.

Accordingly, the vehicle is moved by the high-speed camera 13 disposed and held on the side of the wheel W with the shooting direction directed toward the outer surface 16a of the block 16 via the holding member 14 attached to the wheel W and the suspension at two locations. When the wheels W are rolling during C traveling, as shown in FIG. 3, for example, the tire 11 is deformed by constantly photographing the road surface contact state (see (a)) of the block 16 of the tire 11 that is in contact with the road surface R. Even in such a case, the actual tire rolling state can be observed at a fixed point with a highly accurate measurement image (see (b)) that allows image analysis without blurring.
The calculation unit 15 calculates a tire slip speed when the tire 11 rolls on the road surface R based on image data of an image captured by the high speed camera 13 input from the high speed camera 13.

A method for calculating the tire slip speed will be described below.
When calculating the tire slip speed, first, a marker 12 composed of a plurality of dots is formed on the outer surface 16a of the block 16 of the tire 11 (for example, the left front wheel) for which the tire slip speed is to be calculated, and the marker 12 is photographed. The high-speed camera 13 is placed and held via the holding member 14 on the side of the wheel W on which the target tire 11 is mounted with the shooting direction facing the outer surface 16a of the block 16 (see FIG. 2). ). Also, a length measuring tool such as a ruler is photographed, and the length of one pixel of the photographed image is measured.

Next, during traveling of the vehicle C, the outer surface 16a of the block 16 of the tire 11 of the rolling wheel W is photographed by the high-speed camera 13 from the wheel W side surface. At this time, gamma adjustment, contrast adjustment, and brightness adjustment of the photographed image are performed by the image processing software in order to easily identify the marker 12 of the photographed image.
Next, the captured image data captured by the high-speed camera 13 is sent to the calculation unit 15, and the calculation unit 15 determines the feature points on the outer surface 16 a of the block 16 of the tire 11 and the road surface R on the captured image based on the captured image data. Coordinates are calculated with image analysis software.

FIG. 4 conceptually shows a tire slip speed calculation method, where (a) is an explanatory diagram before slipping, and (b) is an explanatory diagram after slipping. FIG. 5 specifically shows a method for calculating the tire slip speed of FIG. 4, (a) is an explanatory diagram of measurement points, (b) is an explanatory diagram at the start of interval measurement, and (c) is an end of interval measurement. It is explanatory drawing.
As shown in FIG. 4, the distance (dot) between the two feature points on the outer surface 16a of the block 16 and the road surface R before the tire slip (see (a)) and after the tire slip (see (b)) on the shooting screen. The tire slip speed (X direction) is calculated from the change in the number) and the travel time (number of shot frames).

  In calculating the tire slip speed, for example, as shown in FIG. 5, on the photographing screen obtained by photographing the outer surface 16a of the block 16, five measurement points (near the center in the tire circumferential direction of the tread and near the base) A reference point (P) for measurement set corresponding to the feature point and one measurement point Q on the road surface R are set (see (a)), and the image before the slip to start measurement, that is, the tread side From the image in which the measurement point P is located at the left end of the shooting screen, the image after the slip is completed, that is, the measurement point Q on the road surface R side is in the image, and the right end of the block 16 is at the right end of the shooting screen. The measurement interval is taken up to the positioned image.

That is, on the shooting screen, the feature point of the block root is extracted from the marker 12 on the outer surface 16a of the block 16, and the feature point is provided on the road surface R that the block 16 contacts, and the longitudinal vehicle body acceleration G is set to 0 to 0.7G. The relative distance between the feature points of the outer surface 16a of the block 16 and the road surface R is calculated for each frame (frame) of the captured image. The feature point of the road surface R is set arbitrarily.
Then, the amount of change in the relative distance between the two shooting screens (shooted images) is calculated, and the sliding speed is calculated by dividing the amount of change in the relative distance by the time difference between the two shooting screens (shot images). The time difference in the shooting screen (captured image) is determined by the difference between the frame rate of the high-speed camera 13 and the number of shot frames (n-th image) of the two shooting screens (captured images).
Difference in number of shots / frame rate = time difference between shot images

In this way, the calculation unit 15 calculates the relative distance between the feature points set on the outer surface 16a and the road surface R of the block 16 on one screen from the image taken by the high-speed camera 13, and the two screens. Based on the change of the relative distance by comparison, the slip speed of the block 16 is calculated.
Tables 1 and 2 show the results of measuring the slipping speed of the block in the actual tire rolling state obtained by the above-described tire slipping speed calculation method.

In the tire 1, five measurement points P1 to P5 of the outer surface 16a of the block 16 and a measurement point Q of the road surface R are set, and the longitudinal vehicle body acceleration G is 0.1 G (21 km) for each measurement point P1 to P5. / H), 0.3 G (21 km / h), and 0.7 G (11 km / h), the sliding speed of the block 16 was calculated, and the average sliding speed was obtained.
The average slip speed of the block 16 in the tire 1 is −307 mm / s at a vehicle body acceleration of 0.1 G, −252 mm / s at 0.3 G (21 km / h), and −230 mm / s at 0.7 G (11 km / h). there were. That is, the sliding speed of the tire 1 is fastest when the vehicle body acceleration is 0.1 G.

In the tire 2, five measurement points P1 to P5 of the outer surface 16a of the block 16 and a measurement point Q of the road surface R are set, and the longitudinal vehicle body acceleration G is 0 G (23 km / h) for each measurement point P1 to P5. ), 0.6 G (22 km / h), 0.7 G (12 km / h), the slip speed of the block 16 was calculated, and the average slip speed was obtained.
The average slip speed of the block 16 in the tire 2 is −110 mm / s at 0 G (23 km / h), −204 mm / s at 0.6 G (22 km / h), and −112 mm / s at 0.7 G (12 km / h). Met. That is, the slip speed of the tire 2 is fastest when the vehicle body acceleration is 0.6G.

  In this way, a plurality of dots are marked on the outer surface 16a of the block 16 of the tire 11, and the relative speed between the block 16 and the road surface R in contact with the block 16 is calculated from the captured image of the high-speed camera 13, and the calculation result Based on the above, the slip speed of the block 16 in the actual tire rolling state is calculated. That is, even if the tire 11 is photographed as it is, the behavior of the block 16 cannot be followed, so the outer surface 16a of the block 16 is marked with fine dots, and the behavior of the block 16 of the tire 11 when the wheel W rolls. To follow.

  As a result, since the behavior of the tire 11 that is actually rolling can be directly photographed by photographing the outer surface 16a and the road surface R of the block 16 of the tire 11, the load, vertical spring, temperature, etc. The measurement conditions relating to the tire 11 can be matched with the tire 11 that actually rolls, and a more accurate tire slip speed can be obtained with higher accuracy than before. In addition, since photographing is performed in units of the blocks 16 of the tire 11, the sliding speed at an arbitrary point can also be calculated.

  This invention forms a tread surface of a wheel tire that rolls on a road surface and shoots the side surface and road surface of the block located on the outermost periphery of the tread surface as the same screen, and from the captured image, the side surface and road surface of the block on one screen Since the relative distance between each set feature point is calculated, and then the block slip speed is calculated based on the change in the relative distance by comparing the two screens, it occurs in the tire that is actually rolling on the road surface. Since it is possible to accurately measure the slipping speed generated on the tire tread when the tire is in a rolling state, it is possible to measure the slipping speed of the tire during wheel rolling. It is most suitable for a tire slip speed measuring system that realizes a speed measuring method and a tire slip speed measuring method.

DESCRIPTION OF SYMBOLS 10 Tire slip speed measuring system 11 Tire 12 Marker 13 High speed camera 14 Holding member 14a 1st holding part 14b 2nd holding part 15 Calculation part 16 Block 16a Outer side surface 17 Connection means C Vehicle P, P1-P5, Q Measurement point R Road surface W wheel Ww wheel

Claims (4)

Processing to form a tread surface of a wheel tire that rolls on the road surface and photograph the side surface of the block located on the outermost periphery of the tread surface and the road surface as the same screen;
A process of calculating a relative distance between each feature point set on the side surface of the block and the road surface on one screen from a captured image;
A tire slip speed measuring method comprising: calculating a slip speed of the block based on a change in the relative distance by comparing two screens.   The tire sliding speed according to claim 1, wherein the sliding speed of the block is calculated by dividing a calculation result obtained by calculating a change in the relative distance by comparing the two screens by a time difference between the two screens. Measuring method. A marker provided on a side surface of a block that forms a tread surface of a wheel tire that rolls on a road surface and is located on the outermost periphery of the tread surface;
When rolling the wheel, a camera that photographs the side surface of the block and the road surface on the same screen;
The relative distance of each feature point set on the side surface of the block and the road surface on one screen is calculated from the image taken by the camera, and the slip of the block is based on the change of the relative distance by comparing two screens. A tire slip speed measurement system comprising: a calculation unit that calculates speed.   The tire slip speed measuring system according to claim 3, further comprising a holding member that is attached to a vehicle body to which the wheel is mounted and that holds the camera with a shooting direction directed to a side surface of the block at a side of the wheel.

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