JP2009222679A - Device and method for detecting vehicle position - Google Patents

Abstract

A position of a test vehicle placed on a chassis dynamometer is easily and accurately detected with an inexpensive and simple device configuration.
In a chassis dynamometer including a roller for placing a wheel of a vehicle, an image of a wheel of a vehicle V on which the wheel is placed on the roller is picked up by an image pickup device. The position of the vehicle V is detected by measuring the brightness and specifying the position of the wheel of the vehicle V based on the change in brightness obtained from the measurement result. Here, the wheel has a portion where the light absorption rate (lightness) is extremely different, that is, the tire and the wheel. Therefore, it is possible to recognize the point at which the brightness is switched extremely as the boundary between the tire and the wheel, and the position of the vehicle V can be detected by observing the boundary.
[Selection] Figure 1

Description

  The present invention relates to a technique for detecting the position of a vehicle placed on a chassis dynamometer.

  In recent years, chassis dynamometers have been used in performance tests of vehicles such as automobiles. In this type of vehicle performance test, a test vehicle is set on a chassis dynamometer, and a test vehicle is simulated in a predetermined driving pattern to simulate an actual driving test. Measurement is possible.

  In the chassis dynamometer, it is necessary to position the wheels of the test vehicle at a desired position on the roller and fix the test vehicle so that it does not move after the start of the test run. Such fixing of the test vehicle is performed by connecting the test vehicle and fixing portions disposed on the pits before and after the test vehicle by a belt or the like and pulling each belt (for example, Patent Document 1). Etc.).

  When the test vehicle is fixed using a belt or the like, the vehicle is pulled while adjusting so that the wheels of the test vehicle do not move from a desired position on the roller. However, there may be some deviation when trying to pull the belt so that the wheels of the test vehicle are not moved from the desired position on the roller. In addition, when the test vehicle starts a test run, a force generated between the roller to be rotated and the wheels of the test vehicle may deviate from a desired position where the test vehicle is initially positioned.

  In view of such a problem, for example, in Patent Document 2, the position of the test vehicle is detected by a position sensor that detects the position of the vehicle, and the belt is appropriately wound up or fed out to be corrected to a desired position. Technology is disclosed.

Japanese Patent Laid-Open No. 10-307082 JP 2007-212152 A

  As in Patent Document 2, it is common to detect the position of a test vehicle in a chassis dynamometer. Conventionally, as a means for performing such position detection, for example, an optical sensor, a laser length measuring device, a wire encoder, a limit switch, and the like have been used.

  However, a plurality of installations are necessary for the optical sensor, and a laser measuring device is limited in the laser light irradiation location in a vehicle having a complicated shape such as a curved surface, or a reflecting member that reflects the laser light. May need to be installed in the vehicle. In addition, since the wire encoder and limit switch involve physical coupling and contact, the apparatus configuration is complicated. As described above, the conventional means for detecting the position in the chassis dynamometer have been difficult to say in terms of usability.

  In view of the actual situation, the present invention provides a vehicle position detection device and a vehicle position detection method that can easily and accurately detect the position of a test vehicle placed on a chassis dynamometer in an inexpensive and simple device configuration. The purpose is to provide.

The vehicle position detection device of the present invention is a vehicle position detection device for detecting the position of a vehicle having wheels mounted on the rollers in a chassis dynamometer having a roller for mounting the wheels of the vehicle. Imaging means for imaging an area including at least a wheel, brightness measurement means for measuring the brightness of a wheel imaged by the imaging means, and identifying the position of the wheel based on a brightness change obtained from a measurement result of the brightness measurement means Thus, a position detecting means for detecting the position of the vehicle is provided.
In the vehicle position detection device of the present invention, the lightness measuring means measures the lightness of at least one point on the boundary between the tire and the wheel of the wheel including its peripheral portion.
In the vehicle position detection apparatus of the present invention, the lightness measuring means measures the lightness of a point located in the vehicle front-rear direction and the diametrical direction on the boundary between the tire and the wheel including the peripheral portion thereof. It is characterized by.
In the vehicle position detection apparatus of the present invention, the lightness measuring means measures the lightness of two points arranged in the horizontal direction on the boundary between the tire and the wheel, including the peripheral portion thereof. Features.
Further, in the vehicle position detection device of the present invention, the lightness measuring means measures the lightness of two points that are spaced apart in the horizontal direction on the boundary between the tire and the wheel of the wheel and that are positioned in the diameter direction. It is characterized by.
In the vehicle position detection apparatus of the present invention, the lightness measuring means measures the lightness along the vehicle front-rear direction at the wheel.
In the vehicle position detection apparatus of the present invention, the lightness measuring means measures the lightness for each unit pixel.
Further, in the vehicle position detection device of the present invention, the position detection means recognizes a boundary between the wheel tire and the wheel based on a difference in brightness measured by the brightness measurement means, thereby determining the position of the wheel. It is characterized by specifying.
Further, in the vehicle position detection device of the present invention, the position detection means observes the lightness measured by the lightness measurement means from the tire side of the wheel, and the point where the height difference occurs in the lightness and the tire. It is characterized by recognizing the boundary with the wheel.
Further, in the vehicle position detection device of the present invention, the position detection means may use any two points that are spaced apart in the horizontal direction in two sections where the height difference is generated as a boundary between the tire and the wheel. It is characterized by recognition.
Further, in the vehicle position detecting device of the present invention, the position detecting means recognizes any two points arranged in the horizontal direction apart from each other as a boundary between the tire and the wheel, and determines the two points recognized as the boundary. The center of the connected straight line is specified as the position of the center of the wheel.
Further, in the vehicle position detection device of the present invention, the position detection means specifies the position of the wheel based on the recognized boundary between the tire and the wheel, and compares the position of the wheel with a predetermined reference position. And detecting the position of the vehicle.
In the vehicle position detection apparatus according to the present invention, the imaging unit includes a telephoto lens in which a conversion deviation amount of a unit pixel caused by a displacement in the optical axis direction of the vehicle falls within a predetermined range. To do.
Further, the vehicle position detection device of the present invention is characterized by comprising notifying means for notifying that when the position of the wheel specified by the position detecting means exceeds the predetermined reference position.
In the vehicle position detection apparatus of the present invention, the position detection means detects the position of the vehicle by comparing the position of the center of the wheel with a predetermined reference position.
Further, in the vehicle position detection device of the present invention, the position detection means obtains a ratio of a distance from a point recognized as the boundary to a predetermined position, and detects the position of the vehicle by comparing with a predetermined ratio. It is characterized by that.
In the vehicle position detection apparatus of the present invention, the imaging unit may include a wide-angle lens that allows the point at which the brightness is measured by the brightness measuring unit to always fall within the angle of view when the vehicle is displaced in the optical axis direction. It is characterized by providing.
Further, the vehicle position detection device of the present invention is characterized by further comprising a notification means for notifying that when the ratio obtained by the position detection means is not within the range of the predetermined ratio.
In the vehicle position detection apparatus of the present invention, the lightness measuring means measures the lightness of the wheel of the wheel and its outer region.
The vehicle position detection method of the present invention is a vehicle position detection method for detecting the position of a vehicle on which wheels are mounted on the rollers in a chassis dynamometer including a roller on which wheels of the vehicle are mounted. Based on an imaging step of imaging an area including at least a wheel of the vehicle by an imaging means, a brightness measurement step of measuring the brightness of the wheel imaged in the imaging step, and a brightness change obtained from a measurement result of the brightness measurement step And a position detecting step of detecting the position of the vehicle by specifying the position of the wheel.

  According to the present invention, the position of a test vehicle placed on a chassis dynamometer can be easily and accurately detected with an inexpensive and simple device configuration.

A preferred embodiment of a vehicle position detection apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of a chassis dynamometer provided with a vehicle position detecting device of the present invention, FIG. 1 (a) is a schematic plan view, and FIG. 1 (b) is a schematic side view.

  In the chassis dynamometer, the test vehicle V to be tested is a four-wheel drive vehicle. A pit floor 1 is laid on the pit where the chassis dynamometer is installed, and the test vehicle V is located at a predetermined position on the pit floor 1. Fixed in place. In this figure, the front-rear direction of the test vehicle V is indicated by arrows Fr and Rr, respectively.

  When the test vehicle V is arranged and fixed at a predetermined position on the pit floor 1, first, the four wheels of the test vehicle V are placed on the rollers 2 corresponding thereto. Next, each wheel is positioned at a predetermined position on the roller 2 using a wheel positioning device 3 provided for each of the four wheels on the front, rear, left and right of the test vehicle V. Each wheel positioning device 3 has the same configuration, and performs positioning by sandwiching the wheel from front and rear obliquely by two pairs of arms 3a. Then, in a state where the wheel positioning device 3 positions the wheels of the test vehicle V, the vehicle fixing device 100 is controlled by the traction control device 5 and the test vehicle V is fixed by pulling the belt 105.

  Four vehicle fixing devices 100 are used in the chassis dynamometer. A pair of vehicle fixing devices 100 are disposed on the front and rear pit floors 1 of the test vehicle V, and each of the pair of vehicle fixing devices 100 disposed on the front and rear sides is the same from the center in the width direction of the test vehicle V. Sorted by distance.

  As shown in FIG. 2, the vehicle fixing device 100 includes a belt winding unit 101 that constitutes a substantial main part. The belt winding unit 101 includes a motor unit 102 disposed and fixed on a base 108, a reduction gear 103 connected to the motor unit 102, and a winding shaft 104 connected to the reduction gear 103. One end of the belt 105 having a certain degree of elasticity is introduced into the take-up shaft 104 while being sandwiched between guides 109, and the belt 105 is taken up by rotating the take-up shaft 104. The other end of the belt 105 is provided with a tow hook 107 for towing in connection with the test vehicle V, and a tension sensor 106 constituted by a load cell or the like is provided at an appropriate position of the belt 105. The guide 109 is supported so as to be movable up and down for a predetermined stroke along a support column 110 erected on the base 108. The guide 109 is screwed with a lead screw 111 attached to the support column 110 and is operated by operating the handle 112. It moves up and down via 111.

In the chassis dynamometer, the test vehicle V is fixed by controlling the vehicle fixing device 100 having such a configuration by the traction control device 5. When the vehicle is fixed, the wheel of the test vehicle V is a roller 2. There is a case where it deviates from the predetermined position above. Further, when the test vehicle V starts a test run, the test vehicle V may deviate from a predetermined position where the test vehicle V is initially positioned due to a force generated between the rotationally driven roller 2 and the wheels of the test vehicle V. .
Therefore, in the chassis dynamometer, the imaging device 6 images the wheels of the test vehicle V, detects the position of the test vehicle V based on the brightness of the wheels imaged by the imaging device 6, typically the brightness change, The test vehicle V is corrected to a predetermined position by controlling the vehicle fixing device 100 as appropriate.

  An imaging apparatus 6 shown in FIG. 1 is a CCD camera or the like having an imaging element such as a CCD. The imaging device 6 obtains an image signal representing a moving image or a still image by driving the imaging device continuously or once, and transmits the image signal to the traction control device 5. In addition, the imaging device 6 is disposed on the side of the wheel of the test vehicle V in the present embodiment in order to image the wheel of the test vehicle V as described above. In the present embodiment, the imaging device 6 is disposed on the side of the left front wheel, but may be disposed on the right front wheel or the side of the right or left rear wheel, or a plurality of devices may be disposed. good. The traction control device 5 measures the lightness of the wheel from the image signal received from the imaging device 6 as described above, and detects the position of the test vehicle V based on the lightness change obtained from the measurement result.

  Hereinafter, details of position detection of the test vehicle V by the imaging device 6 and the traction control device 5 will be described with reference to FIGS. Here, the imaging device 6 corresponds to an example of the configuration of the imaging means referred to in the present invention, and the traction control device 5 includes the brightness measuring means and the position detection means referred to in the present invention. The following description corresponds to one processing example of the lightness measurement means and position detection means in the present invention, but the processing is executed by a CPU, ROM, RAM, etc. (not shown) provided in the traction control device 5. And FIG. 3 is a diagram illustrating an example of the wheel image of the test vehicle V captured by the imaging device 6. In the example of FIG. 3, a case will be described in which the brightness of a portion located on the lower side of the wheel is measured including its peripheral portion.

  In FIG. 3A, an image 301 is an image in a state where the wheels of the test vehicle V are placed at a predetermined position (“P” in the drawing) of the roller 2. In this example, the traction control device 5 receives an electrical signal representing the image 301 and measures the lightness in the region 302 shown in the image 301. Note that the traction control device 5 can also perform predetermined processing on the electrical signal from the imaging device 6 to generate the image 301, but the image is used for position detection of the test vehicle V described in the present embodiment. It is not always necessary to generate 301. The area 302 is illustrated for convenience, but is not actually displayed on the image.

  FIG. 3B is a diagram showing the brightness measured by the traction control device 5 in the region 302 shown in the image 301 as a histogram. The traction control device 5 measures the lightness in the region 302 along the x-axis direction (vehicle front-rear direction). In FIG. 3B, the x-axis indicates the position of the wheel of the test vehicle V in the vehicle front-rear direction. The axis indicates the brightness corresponding to each position on the x-axis. Here, the traction control device 5 uses the minimum unit of the x-axis for measuring the brightness as a unit pixel, and the angle of view and magnification of the lens included in the imaging device 6, the depth distance between the imaging device 6 and the wheel, and the projection in the image 301 Taking into account the area and the like, it calculates and holds how many mm the unit pixel corresponds to (converted value).

  With reference to the brightness histogram in the region 302 shown in FIG. 3B, a sharp change in brightness, that is, a point where an elevation difference occurs (initial position; “init” in the figure) can be observed. This shows a boundary point (FIG. 3A, 303) between a rubber-made black tire with low reflectance and a metal-made wheel with high reflectance such as silver. The traction control device 5 is adapted to identify the position of the wheel by recognizing the point at which such a difference in brightness level changes sharply as a boundary point between the tire and the wheel. Strictly speaking, the boundary between the tire and the wheel is a section where a steep slope on the histogram referred to in FIG. 3B is generated, and has a certain width. In consideration of this, in this example (the same applies to the examples in FIGS. 4 and 5 described later), the point where the brightness increases sharply is recognized as the boundary point (303) (strictly speaking, it is recognized as the edge of the tire) This is used as a reference for position detection. In the position detection in the case where there is a deviation as will be described later, a point where the brightness sharply increases is recognized as a boundary point. By using the same method for recognizing the boundary before and after the shift, even if it is a boundary between the tire and the wheel that has a certain width on the image or data, it is caused by the width. Can be avoided.

  Next, the case where the test vehicle V is deviated from the predetermined position (P) after being fixed by the vehicle fixing device 100 or after starting the test travel will be described with reference to FIGS. In the following description, it is assumed that the traction control device 5 holds the boundary point recognized in FIGS. 3A and 3B as the reference position (init).

  In FIG. 3C, an image 304 is an image in a state where the wheels of the test vehicle V have shifted from a predetermined position (“P” in the figure), and the traction control device 5 displays the image 303 as described above. A representative electrical signal is received and the brightness in region 305 shown in image 304 is measured. Note that the region 305 is located at the same coordinates as the region 302 shown in the image 301.

  FIG. 3D is a diagram showing the lightness measured by the traction control device 5 in the region 305 as a histogram. With reference to the lightness histogram in the region 305 shown in FIG. It can be observed that there is a point (current position; “now” in the figure). Here, the traction control device 5 recognizes this point as a boundary point between the tire and the wheel (FIG. 3C, 306). The traction control device 5 detects the shift amount L3 of the wheel (vehicle) by comparing the held reference position (init) with the point (now) recognized as the boundary point this time. Since the traction control device 5 knows the converted value of how many mm the unit pixel corresponds to, it is possible to calculate the actual shift amount by converting the shift amount L3.

  Thus, the traction control device 5 can detect the amount of deviation of the test vehicle V. In the above description, an example has been described in which the lightness of the part located on the lower side of the wheel is measured. However, as long as the part includes the boundary between the tire and the wheel, the test vehicle is similarly applied to other parts of the wheel. The amount of deviation of V can be detected. Hereinafter, the case where the brightness of the part located in the wheel front-rear direction and the diameter direction on the boundary between the tire and the wheel of the wheel is measured including the peripheral part will be described with reference to FIG.

  FIG. 4 is a diagram for explaining an example of the wheel image of the test vehicle V captured by the imaging device 6, as in FIG. 3. 4A, an image 401 is an image in a state where the wheels of the test vehicle V are placed at a predetermined position (“P” in the figure), and the traction control device 5 outputs an electric signal representing the image 401. The lightness in the area 402 shown in the image 401 is received.

  FIG. 4B is a diagram showing the brightness measured by the traction control device 5 in the region 402 shown in the image 401 as a histogram. Referring to the lightness histogram in the region 402 shown in FIG. 4B, a point where the lightness has a steep height difference (initial position; “init” in the figure) can be observed. No. 5 recognizes such a point where the brightness difference changes sharply as a boundary point between the tire and the wheel (FIGS. 4A and 403).

  Next, the case where the test vehicle V is displaced from the predetermined position (P) after being fixed by the vehicle fixing device 100 or after starting the test travel will be described with reference to FIGS. 4 (c) and 4 (d). In the following description, it is assumed that the traction control device 5 holds the boundary point described in FIGS. 4A and 4B as the reference position (init) as described above.

  In FIG. 4C, an image 404 is an image in a state where the wheels of the test vehicle V have shifted from a predetermined position (“P” in the figure), and the traction control device 5 is an electric signal representing the image 404. And the brightness in the area 405 shown in the image 404 is measured. Note that the area 405 is located at the same coordinates as the area 402 shown in the image 401 as described above.

  FIG. 4D is a diagram showing the brightness measured in the region 405 by the traction control device 5 as a histogram. When referring to the brightness histogram in the region 405 shown in FIG. Is present (current position; “now” in the figure). Here, the traction control device 5 recognizes this point as a boundary point between the tire and the wheel (FIGS. 4C and 406). The traction control device 5 detects the wheel shift amount L4 by comparing the held reference position (init) with the point (now) recognized as the boundary point this time.

As described with reference to FIG. 4, the brightness of the portion located in the vehicle front-rear direction and the diametrical direction on the boundary line between the wheel tire and the wheel is measured including the peripheral portion thereof. When the boundary between the tire and the wheel is recognized, it is possible to suppress the influence of the change in the movement distance of the boundary point between the tire and the wheel caused by the longitudinal movement of the wheel.
If it demonstrates in detail, since the wheel of the test vehicle V is mounted on the cylindrical roller 2, the center will move along the concentric circle of the roller 2. FIG. At this time, the point on the boundary line between the tire and the wheel moves along the trajectory of the outer cycloid curve. Therefore, the movement distance in the vehicle front-rear direction caused by the forward and backward movement of the wheel varies depending on the position of the point on the boundary.
In this embodiment, it is ideal that the predetermined position where the wheel is placed is the top of the roller 2, and the center of the wheel is located on the same vertical line as the center of the roller 2. In such a case, it is preferable to use the vehicle longitudinal direction component of the distance between the predetermined position (P) on the roller 2 and the center of the wheel as a reference for the amount of deviation. In this way, when the vehicle longitudinal component of the distance between the predetermined position (P) on the roller 2 and the center of the wheel is used as a reference for the deviation amount, the boundary point between the tire and the wheel recognized by the traction control device 5 is determined. As shown in FIG. 4, the vehicle front-rear direction according to the position of the boundary point is set as a portion located in the vehicle front-rear direction and diametrical direction on the boundary line between the wheel tire and the wheel, or a portion in the vicinity of the vertical direction. Can be approximated to the vehicle longitudinal component of the distance between the predetermined position (P) and the center of the wheel.
Therefore, when the brightness of the portion located in the vehicle longitudinal direction and the diametrical direction on the boundary line (that is, circular) between the wheel tire and the wheel is measured including the peripheral portion, the front and rear of the wheel The influence of fluctuations in the movement distance of the boundary point caused by the movement can be suppressed, and the position can be detected with high accuracy.

  Further, in FIGS. 3 and 4, the brightness is measured by including one peripheral point on the boundary line between the tire and the wheel so as to include the peripheral portion thereof. However, the brightness of a plurality of points on the boundary line between the tire and the wheel is measured. The measurement may be performed including the peripheral portion. Hereinafter, a case where the brightness of a plurality of points on a boundary line between a wheel tire and a wheel is measured including its peripheral portion will be described with reference to FIG. In the following example, a case will be described in which the brightness of two points aligned in the horizontal direction on the boundary between the wheel tire and the wheel is measured.

  FIG. 5 is a diagram illustrating an example of the wheel image of the test vehicle V captured by the imaging device 6. In FIG. 5A, an image 501 is an image in a state where the wheels of the test vehicle V are placed at a predetermined position (“P” in the figure), and the traction control device 5 is an electric signal representing the image 501. And the brightness in the region 502 shown in the image 501 is measured. Here, the region 502 is set to a range including two horizontally aligned points on the boundary line between the wheel tire and the wheel.

  FIG. 5B is a diagram showing the brightness measured by the traction control device 5 in the region 502 shown in the image 501 as a histogram. Referring to the lightness histogram in the region 502 shown in FIG. 5B, there are two points (“FB” and “RB” in the figure) where the lightness has a steep height difference. Here, the traction control device 5 recognizes these two points as boundary points 503 and 504 between the tire and the wheel, and holds an intermediate point between these positions as a reference position (init).

  Next, the case where the test vehicle V is displaced from the position (P) by a predetermined time when the test vehicle V is fixed by the vehicle fixing device 100 or after starting the test travel will be described with reference to FIGS. In the following description, it is assumed that the traction control device 5 holds the reference position (init) described with reference to FIGS.

  In FIG. 5C, an image 505 is an image in a state where the wheels of the test vehicle V are deviated from a predetermined position (“P” in the figure), and the traction control device 5 is an electric that represents the image 505. A signal is received and the brightness in region 506 shown in image 505 is measured. Note that the region 506 is located at the same coordinates as the region 502 shown in the image 501.

  FIG. 5D is a diagram showing the brightness measured by the traction control device 5 in the region 506 as a histogram. Referring to the brightness histogram in the region 506 shown in FIG. 5D, it can be observed that there are two points (“FB ′” and “RB ′” in the figure) where there is a steep difference in brightness. . The traction control device 5 recognizes these two points as boundary points 507 and 508 between the tire and the wheel. The traction control device 5 calculates the intermediate position (now) as the current position, compares the held reference position (init) with the point (now) determined to be the intermediate position of the current boundary point, and determines the wheel position. The shift amount L5 is detected.

  In this way, the brightness of two points arranged in the horizontal direction on the boundary between the wheel tire and the wheel is measured including the peripheral portion to recognize the boundary point between the wheel tire and the wheel. In such a case, it is possible to suppress the influence of the fluctuation of the movement distance of the boundary point caused by the back and forth movement of the wheel. That is, as described above, the points on the boundary line between the tire and the wheel vary in the moving distance in the vehicle front-rear direction depending on the position, but are separated in the horizontal direction on the boundary line between the wheel tire and the wheel. By measuring the brightness of the two points in a row, including the surrounding area, recognizing the boundary point between the wheel tire and the wheel and specifying the intermediate position, the intermediate position is the center of the wheel in the vehicle longitudinal direction. Match the position. Therefore, when the brightness of two points on the boundary line between the wheel tire and the wheel is measured including its peripheral portion, it is positioned in the vehicle longitudinal direction and the diametrical direction on the boundary line between the tire and the wheel. Similarly to the case where the portion to be measured is measured, it is possible to suppress the influence of the fluctuation of the movement distance of the boundary point caused by the back and forth movement of the wheel, and the position can be detected with high accuracy.

  In the recognition of the boundary between the tire and the wheel in FIGS. 3 to 5, the point where the lightness sharply increases is recognized as the boundary, strictly speaking, the edge of the tire, but the lightness sharply decreases. May be recognized as a boundary (strictly speaking, as an edge of a wheel), and this may be used as a reference for position detection. In such a case, the shift of the wheel can be detected without particularly using the tire as the object of brightness measurement. The details will be described below with reference to FIG.

  FIG. 15 is a diagram illustrating an example of an image of a wheel of the test vehicle V captured by the imaging device 6. Here, in this figure, since tires are not considered for recognizing the boundaries in the wheels, it is assumed that there are no tires for convenience of explanation, and is represented by dotted lines. In FIG. 15A, an image 1501 is an image in a state where the wheels of the test vehicle V are placed at a predetermined position (“P” in the figure). In the image 1501, 1503 represents a wheel. The traction control device 5 receives the electrical signal representing the image 1501 and measures the brightness in the region 1502 shown in the image 1501. Here, the region 1502 is set to a range including two points arranged in the horizontal direction on the wheel boundary of the wheel and the outer region thereof.

  FIG. 15B is a diagram showing the brightness measured by the traction control device 5 in the region 1502 shown in the image 1501 as a histogram. Referring to the lightness histogram in the region 1502 shown in FIG. 15B, there are two points (“FB” and “RB” in the figure) where the lightness has a steep height difference. Here, the traction control device 5 recognizes these two points as the boundary points 1504 and 1505 between the tire and the wheel, and holds an intermediate point between these positions as a reference position (init). Here, the point where the lightness falls steeply is recognized as a boundary point, strictly speaking, as a wheel edge.

  Next, the case where the test vehicle V is deviated from the position (P) by a predetermined time when the test vehicle V is fixed by the vehicle fixing device 100 or after starting the test travel will be described with reference to FIGS. In the following description, it is assumed that the traction control device 5 holds the reference position (init) described in FIGS. 15 (a) and 15 (b).

  In FIG. 15C, an image 1506 is an image in a state where the wheels of the test vehicle V are deviated from a predetermined position (“P” in the figure), and the traction control device 5 is an electric image representing the image 1506. A signal is received and the brightness in region 1507 shown in image 1506 is measured. Note that the region 1507 is located at the same coordinates as the region 1502 shown in the image 1501.

  FIG. 15D is a diagram showing the brightness measured in the region 1507 by the traction control device 5 as a histogram. Referring to the brightness histogram in the region 1507 shown in FIG. 15D, it can be observed that there are two points (“FB ′” and “RB ′” in the figure) where there is a steep difference in brightness. . The traction control device 5 recognizes these two points as boundary points 1508 and 1509 between the tire and the wheel. The traction control device 5 calculates the intermediate position (now) as the current position, compares the held reference position (init) with the point (now) determined to be the intermediate position of the current boundary point, and determines the wheel position. The shift amount L15 is detected.

  As described with reference to FIG. 15, if the point where the lightness falls sharply is recognized as a boundary, the position of the wheel can be detected even in the absence of the tire, in other words, without considering the lightness of the tire. . In other words, the wheel is made of metal and further coated, and the light reflectance is high. On the other hand, the tire house on the body side is usually a dark color, and light hardly reflects. Therefore, as shown in FIG. 15, the light and darkness of the light is clear in the wheel and its outer region, and the boundary between the tire and the wheel can be easily discriminated. Here, the boundary is recognized from the two points horizontally spaced apart on the wheel boundary of the wheel and the range (area) including the outer area, but as in FIG. Needless to say, even when only one point of the boundary is measured for brightness including its peripheral portion, the boundary can be recognized from the point where the brightness decreases.

  Further, as shown in FIG. 5, the brightness of the part including the boundary between the tire and the wheel may be measured as a point that is arranged in the horizontal direction on the boundary line between the wheel and the wheel and is positioned in the diameter direction. Good. Hereinafter, the case where it measures in this way is demonstrated using FIG.

  FIG. 6 is a diagram illustrating an example of the wheel image of the test vehicle V captured by the imaging device 6, as in FIG. 5. In FIG. 6A, an image 601 is an image in a state where the wheels of the test vehicle V are placed at a predetermined position (“P” in the drawing), and the traction control device 5 is an electric signal representing the image 601. And the brightness in the region 602 shown in the image 601 is measured. Here, the region 602 is set to a range including two horizontally aligned points on the boundary between the tire and the wheel of the wheel and passing through the center C (that is, the two points are located in the diameter direction). .

  FIG. 6B is a diagram showing the brightness measured by the traction control device 5 in the region 602 shown in the image 601 as a histogram. Referring to the brightness histogram in the region 602 shown in FIG. 6B, there are two sections where the brightness has a steep height difference (s1, s2). Here, the traction control device 5 arbitrarily selects two points that are separated in the horizontal direction in the two sections, recognizes it as a boundary (FB, RB) between the tire and the wheel, and intermediate points between these positions. Is held as a reference position (init).

  Next, a case where the test vehicle V is deviated from the position (P) by a predetermined time when the test vehicle V is fixed by the vehicle fixing device 100 or after starting the test travel will be described with reference to FIGS. In the following description, it is assumed that the traction control device 5 holds the reference position (init) described in FIGS. 6 (a) and 6 (b).

  In FIG. 6C, an image 603 is an image in a state where the wheels of the test vehicle V are deviated from a predetermined position (“P” in the figure), and the traction control device 5 is an electric that represents the image 603. A signal is received and the brightness in the region 604 shown in the image 603 is measured. Note that the region 604 is located at the same coordinates as the region 602 shown in the image 601.

  FIG. 6D is a diagram showing the brightness measured by the traction control device 5 in the region 604 as a histogram. Referring to the lightness histogram in the region 604 shown in FIG. 6D, it can be observed that there are two sections in which the lightness has a steep height difference (s3, s4). Here, the traction control device 5 arbitrarily selects two points that are separated in the horizontal direction in the two sections and recognizes them as a boundary (FB ′, RB ′) between the tire and the wheel. The traction control device 5 calculates the intermediate position (now) as the current position, compares the held reference position (init) with the point (now) determined to be the intermediate position of the current boundary point, and determines the wheel position. The shift amount L6 is detected.

  Thus, in the example described with reference to FIG. 6, the brightness of two points arranged in the horizontal direction on the boundary between the tire and the wheel of the wheel is measured including the peripheral portion thereof. The boundary point between the tire and the wheel is recognized as two arbitrarily selected points that are horizontally separated in two sections where the brightness is different, and the center of these two points is specified as the center of the wheel. I did it. In such a method, the center of the tire can be accurately identified without strictly extracting the boundary between the tire and the wheel having a certain width on the image or data, and the position of the test vehicle V can be determined based on this. Can be detected.

In the present embodiment, as described above with reference to FIGS. 3 to 6 and FIG. 15, the brightness of the wheel imaged by the imaging device 6 is measured, and the boundary point between the tire and the wheel is recognized based on the difference in brightness. Identify the wheel position. Here, in the case of FIGS. 3 to 5, the traction control device 5 recognizes the boundary point between the tire and the wheel as a point where the lightness sharply increases. The point where the difference in brightness is generated is observed by scanning to the right. That is, the brightness is observed from the end point in the vehicle front-rear direction of the area where the brightness is measured, and a point at which the brightness is switched sharply (a point where the height difference occurs) is recognized as a boundary point between the tire and the wheel.
That is, as shown in FIG. 7, there is a case where a part of the wheel of the wheel is perforated for weight reduction or the like. In such a case, the brightness of the opening portion (the hatched portion in the wheel area in the drawing) penetrating through may be low.
Therefore, when recognizing the boundary between the tire and the wheel, if the point where the difference in brightness occurs is observed by scanning from the tire side to the wheel side (FIG. 6B, arrow), the opening It is possible to prevent the portion from being erroneously recognized as the boundary between the tire and the wheel, and to prevent erroneous detection of the deviation amount of the test vehicle V.

  In the description of FIGS. 3 to 6 and FIG. 15, the traction control device 5 first specifies and holds the reference position (init). However, the reference position (init) is set to a predetermined position. (P) and the tire outer diameter may be calculated and held in advance. In the above description, the brightness is measured in unit pixels. However, the brightness may be measured in the vehicle front-rear direction in units of a plurality of pixels (for example, 4 pixels, 16 pixels, etc.). Absent. In the above description, the example is described in which the brightness is measured in the horizontal component in the vehicle front-rear direction. However, the brightness may be measured in an oblique direction.

  In this way, the traction control device 5 detects the deviation amount of the test vehicle V, and corrects the test vehicle V to a predetermined position by controlling the vehicle fixing device 100 based on the detected deviation amount. Can do. Here, when correcting the test vehicle V to a predetermined position, a threshold value may be provided for the deviation amount, and when the threshold value is exceeded, the vehicle fixing device 100 may be driven to correct the deviation amount. . Hereinafter, an example of the threshold will be described.

  FIG. 8 is an example in which predetermined amounts of thresholds th (F) and th (R) are provided in the vehicle longitudinal direction of “init” in the histogram specified as the reference position in FIG.

  FIGS. 9A and 9B show a predetermined amount in the vehicle front-rear direction of the reference position “init” that is an intermediate position between the boundary points 503 and 504 recognized at two points in FIGS. 5A and 5B. This is an example in which thresholds th (F) and th (R) are provided. 9 (c) and 9 (d), a predetermined amount of threshold value th1 (F) and a predetermined amount in the vehicle longitudinal direction of the boundary points 503 and 504 recognized at two points in FIGS. 5 (a) and 5 (b). In this example, th1 (R), threshold values th2 (F) and th2 (R) are provided.

  By providing the threshold value in this way and correcting the test vehicle V depending on whether or not the reference position is within the threshold value, the traction control device 5 can easily convert the test vehicle V without converting the actual deviation amount. Correction can be made within a predetermined threshold. The predetermined threshold value can be arbitrarily set.

  Further, when the traction control device 5 measures the brightness as described with reference to FIG. 5, the correction of the position of the test vehicle V is also performed with the ratio of the distance from the reference position “init” of the two boundary points recognized. Is possible. Hereinafter, correction of the position based on the ratio of the distance from the reference position of the boundary point will be described with reference to FIG.

First, the traction control device 5 specifies a reference position “init” that is an intermediate position between the boundary points 503 and 504 recognized from the brightness of the image 501 shown in FIG. In this case, the ratio of the distance from the reference position “init” to the points corresponding to the boundary points 503 and 504 (“FB” and “RB” in the figure) is as shown in FIG. 10B. The ratio is “a: b”, which is “1: 1” in this state.
Next, a case where the test vehicle V has shifted to the front or back will be described with reference to FIGS. 10C and 10D. In this case, the traction control device 5 first corresponds to the boundary points 507 and 508. ("FB '" and "RB'" in the figure) are identified from the histogram shown in FIG. 10 (d), and the distance from each reference position "init" is obtained to determine the ratio. Here, it is assumed that “a ′: b ′” is obtained as referred to in FIG. Then, the traction control device 5 compares the obtained “a ′: b ′” with a predetermined ratio range (for example, “4-6: 6-4” etc.) that is held in advance, When a ′: b ′ ”exceeds a predetermined ratio range, the vehicle fixing device 100 is controlled.

  Thus, even when the position of the test vehicle V is corrected by the ratio of the distance from the reference position of the two boundary points recognized from the brightness of the image, the actual deviation amount is not converted, The test vehicle V can be easily corrected within a predetermined threshold.

Further, regarding the correction of the position of the test vehicle V described above, for example, when the position of the test vehicle V is specified with reference to the boundary between the tire and the wheel as shown in FIG. It is possible to suppress the detection error of the shift amount in the vehicle front-rear direction caused by the movement of the imaging device 6 in the optical axis direction (depth direction). This is because the telephoto lens has a relatively narrow angle of view for capturing the subject, so even if the subject moves in the depth direction, the influence of the relative ratio of the subject in the entire image is small. . Therefore, by using a telephoto lens, the accuracy error (the amount of movement of the test vehicle V in the longitudinal direction of the vehicle)
(Which is caused by a shift in the length converted value in the unit pixel) can be reduced. In this case, the angle of view of the telephoto lens may be selected so that the conversion deviation amount of the unit pixel falls within a predetermined allowable range. In addition, even if it is a normal lens, if it has an optical zoom function, it can be used similarly to a telephoto lens.

  Further, for example, as shown in FIGS. 9 (a) and 9 (b), the brightness of two points aligned in the horizontal direction on the boundary line between the tire and the wheel is measured including the peripheral portion thereof, so that the wheel When two boundary points between a tire and a wheel are recognized, the center of the wheel is specified from these two points, and the position of the test vehicle V is detected based on this center, the two points to be observed are always defined. It is preferable to use a wide-angle lens that falls within the corner. When the center of the wheel is specified by recognizing two points of the boundary between the tire and the wheel, the specified center is the movement in the width direction of the test vehicle V, in other words, the optical axis direction (depth direction) of the imaging device 6. Regardless of the amount of deviation in the vehicle longitudinal direction caused by Therefore, if a lens having an angle of view that can measure the brightness of two points to be observed reliably is used, the center of the wheel can always be accurately identified.

  Here, an operation flow of the traction control device 5 having the above-described configuration and function will be described with reference to FIG. FIG. 12A is a flow for correcting the position of the test vehicle V when the test vehicle V is fixed at a predetermined position on the roller 2, and FIG. This is a flow for correcting the position when the test vehicle V deviates from the predetermined position where it was initially positioned when started.

  First, in step S101 of FIG. 12A, the traction control device 5 determines the traction force for fixing the test vehicle V, and proceeds to step S102.

  In step S102, the traction control device 5 starts winding the belt 105 by the vehicle fixing device 100 in order to fix the test vehicle V with the traction force determined in step S101, and proceeds to step S103.

  In step S103, the traction control device 5 monitors whether or not the tension detected by the tension sensor 106 has reached the traction force determined in step S101. If it is determined that the traction force has been reached, the traction control device 5 proceeds to step S104.

  In step S104, the traction control device 5 confirms the position of the wheel of the test vehicle V based on the image signal from the imaging device 6, and if it is within a predetermined position or threshold value, ends the process and completes the fixing. If it is not within the predetermined position or threshold value on the roller 2, position correction is performed in step S105, and the process proceeds to step S103 again.

Next, FIG. 12B will be described. First, when the test vehicle V starts a test run in step S106 in FIG. 12B, the traction control device 5 confirms the position of the wheel of the test vehicle V based on the image signal from the imaging device 6 in step S107. If it is within the predetermined position or threshold value, the position of the wheel of the test vehicle V is always checked during the test run, and if there is no wheel within the predetermined position or threshold value on the roller 2, in step S108. Perform position correction. After the correction, the position of the wheel of the test vehicle V is confirmed again.
Through the processing as described above, in the chassis dynamometer according to the present embodiment, the placed test vehicle V can always be placed at a predetermined position or within an appropriate range thereof.

As described above, in the present embodiment, the imaging device 6 images the wheels of the test vehicle V, measures the brightness of the captured wheels, and recognizes the boundary between the tire and the wheel based on the brightness change obtained from the measurement result. The position of the vehicle V is detected. Thereby, in this embodiment, the position of the test vehicle V can be detected easily and accurately in a relatively inexpensive and simple apparatus configuration.
In other words, the outer part of a tire or a tire house and the wheel and the part where the light absorption rate (lightness) is extremely different are imaged, and the point at which the lightness changes extremely is recognized as the boundary between the tire and the wheel or the wheel edge. In addition, since the position of the test vehicle V can be detected by tracking it, the position of the test vehicle V can be detected in a simple configuration that is non-contact and does not require a reflecting member or the like on the test vehicle V side. Can do. Further, since the imaging device 6 only needs to measure the brightness, complicated image processing or the like is not required, and the position of the test vehicle V can be detected with a relatively inexpensive configuration.
In addition, because the region where the light absorption rate (brightness) is extremely different, such as the outer region of a tire or a tire house and a wheel, is imaged, the brightness measured from there is clear and the optical system is somewhat Even when the focus is shifted, the boundary between the outer region of the tire or the tire house and the wheel can be clearly recognized, and the position of the test vehicle V can be detected with high accuracy. In addition, since any vehicle has tires and wheels, it is possible to easily cope with changes in shape due to differences in vehicles.

  In the above description, the image captured by the imaging device 6 is an image including the entire wheel, but the image captured by the imaging device 6 is, for example, one of the wheels such as the image 1001 shown in FIG. The image may include a part of a tire and a wheel. Even in such a case, the brightness can be measured in the region 1002, and the boundary point between the tire and the wheel can be specified from the point 1004 where the brightness switches. In addition, in Fig.11 (a), 1005 has shown the wheel and 1006 has shown the tire.

  In the above chassis dynamometer, it has been described that the position of the test vehicle V is detected based on the change in brightness in the image. However, the same position can also be detected by measuring the illuminance and luminance in the image. Alternatively, the position of the test vehicle V can be detected with high accuracy even if the position is detected based on the generated image. In the chassis dynamometer shown in FIG. 13, the imaging device 6 is provided behind the test vehicle V, on the left side of the vehicle, and above the vehicle. In such a configuration, the position in the width direction and the vertical direction of the test vehicle V can be detected based on the image from the imaging device 6 provided at the rear of the vehicle. Further, the position of the test vehicle V in the vehicle front-rear direction and the vertical direction can be detected based on the image from the imaging device 6 provided in the width direction. Further, the position of the test vehicle V in the vehicle front-rear direction and the width direction can be detected based on the image from the imaging device 6 provided above.

  For example, an image from the imaging device 6 provided above is shown in FIG. An image 1401 shown in FIG. 14 is an image of the left side portion behind the vehicle. In this configuration, the observation points P1 and P2 are specified in the image 1401, and the position is detected by observing these. To do. In the test vehicle V having a large number of curved surfaces or the like, when position detection is to be performed with a laser length measuring device or the like, the location where the laser light is appropriately reflected may be limited, but the configuration described above In, the position can be easily detected without being restricted by the shape of the test vehicle V. In the configuration described above, the imaging device 6 is provided at the rear of the vehicle, the width direction on the left side of the vehicle, and the upper side of the vehicle. However, any one of them may be provided, or imaging may be performed on a diagonal line in the test vehicle V A device 6 may be provided.

  In the above description, the traction control device 5 receives the image signal from the imaging device 6, performs brightness measurement, and performs position detection (in other words, the traction control device 5 refers to the brightness measurement means in the present invention). However, the device for detecting the position based on the image signal from the imaging device 6 may be separated from the traction control device 5. In this case, the separate apparatus transmits (notifies) the detected position information of the test vehicle V to the traction control apparatus 5. In the above description, the traction control device 5 detects the deviation amount of the test vehicle V and corrects the position based on the detection result. However, the traction control device 5 detects the deviation of the test vehicle V. In such a case, a configuration may be adopted in which the user is notified of the occurrence of a shift by, for example, issuing a warning sound or displaying on a display, and prompting correction.

  In order to realize the present invention, a storage medium in which a program code (computer program) of software that realizes the functions of the above-described embodiments may be used. In this case, the object of the present invention is achieved by supplying the storage medium to the system or apparatus, and the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Needless to say, the OS (basic system or operating system) running on the computer performs part or all of the actual processing based on the instruction of the program code.

  Furthermore, the program code read from the storage medium may be written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. In this case, based on the instruction of the written program code, the CPU or the like provided in the function expansion board or function expansion unit may perform part or all of the actual processing.

It is a figure which shows the chassis dynamometer which concerns on embodiment of this invention. It is a figure which shows the vehicle fixing device used in the chassis dynamometer which concerns on embodiment of this invention. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a figure explaining position correction based on position detection of a test vehicle in an embodiment of the invention. It is a figure explaining position correction based on position detection of a test vehicle in an embodiment of the invention. It is a figure explaining position correction based on position detection of a test vehicle in an embodiment of the invention. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment. It is a flowchart explaining the position detection and position correction of the test vehicle in embodiment of this invention. It is a figure which shows the chassis dynamometer which detects the position of the test vehicle mounted on the chassis dynamometer based on the image. It is a figure which shows the image which the imaging device provided above the test vehicle mounted on the chassis dynamometer imaged. It is a figure explaining the image which the imaging device used in the chassis dynamometer which concerns on embodiment of this invention images, Comprising: It is a figure explaining the position detection of the test vehicle in this Embodiment.

Explanation of symbols

2 Roller 5 Traction control device 6 Imaging device

Claims (20)

In a chassis dynamometer including a roller for mounting a wheel of a vehicle, a vehicle position detection device for detecting a position of the vehicle on which the wheel is mounted on the roller,
Imaging means for imaging an area including at least wheels of the vehicle;
Brightness measuring means for measuring the brightness of the wheel imaged by the imaging means;
A vehicle position detection apparatus comprising: position detection means for detecting the position of the vehicle by specifying the position of the wheel based on a change in brightness obtained from a measurement result of the brightness measurement means.   The vehicle position detection device according to claim 1, wherein the lightness measurement unit measures the lightness of at least one point on a boundary between the tire and the wheel including the peripheral portion thereof.   3. The vehicle according to claim 2, wherein the lightness measuring unit measures the lightness of a point located in a vehicle front-rear direction and a diameter direction on a boundary between the tire and the wheel of the wheel including a peripheral portion thereof. Position detection device.   3. The vehicle position according to claim 2, wherein the lightness measurement means measures the lightness of two points arranged in a horizontal direction on a boundary between the tire and the wheel of the wheel, including a peripheral portion thereof. Detection device.   5. The vehicle according to claim 4, wherein the lightness measurement unit measures lightness of two points arranged in a horizontal direction on the boundary between the tire and the wheel of the wheel and positioned in the diameter direction. Position detection device.   The vehicle position detection device according to claim 1, wherein the lightness measurement unit measures lightness along the vehicle front-rear direction at the wheel.   The vehicle position detection device according to claim 6, wherein the lightness measurement unit measures lightness for each unit pixel.   2. The position detection unit identifies a position of the wheel by recognizing a boundary between a tire and a wheel of the wheel based on a difference in brightness measured by the brightness measurement unit. The vehicle position detection apparatus of any one of -7.   The position detecting means observes the lightness measured by the lightness measuring means from the tire side of the wheel, and recognizes a point where a difference in height occurs in the lightness as a boundary between the tire and the wheel. The vehicle position detection device according to claim 8.   9. The position detecting means recognizes any two points that are separated in the horizontal direction in two sections where a difference in height occurs in brightness as a boundary between the tire and the wheel. The vehicle position detection device described.   The position detecting means recognizes any two points that are separated from each other in the horizontal direction as a boundary between the tire and the wheel, and a center of a straight line connecting the two points recognized as the boundary is a center of the wheel. The vehicle position detection device according to claim 10, wherein the vehicle position detection device is specified as a position.   The position detecting means identifies the position of the wheel on the basis of the recognized boundary between the tire and the wheel, and detects the position of the vehicle by comparing the position of the wheel with a predetermined reference position. The vehicle position detection device according to claim 8 or 9.   13. The vehicle position detection device according to claim 12, wherein the imaging unit includes a telephoto lens so that a conversion deviation amount of a unit pixel caused by a displacement in the optical axis direction of the vehicle falls within a predetermined range. .   13. The vehicle position detection device according to claim 12, further comprising notification means for notifying when the position of the wheel specified by the position detection means exceeds the predetermined reference position.   The vehicle position detection device according to claim 11, wherein the position detection unit detects the position of the vehicle by comparing a position of a center of the wheel with a predetermined reference position.   11. The position detection unit detects a position of the vehicle by obtaining a ratio of a distance to a predetermined position of a point recognized as the boundary and comparing it with a predetermined ratio. Vehicle position detection device.   The image pickup unit includes a wide-angle lens so that when the vehicle is displaced in the optical axis direction, a point at which the lightness is measured by the lightness measurement unit is always within an angle of view. The vehicle position detection device described in 1.   The vehicle position detection device according to claim 16, further comprising a notification means for notifying when the ratio obtained by the position detection means is not within the range of the predetermined ratio.   The vehicle position detection device according to claim 1, wherein the lightness measuring unit measures the lightness of the wheel of the wheel and an outer region thereof. In a chassis dynamometer having a roller for mounting a wheel of a vehicle, a vehicle position detection method for detecting a position of a vehicle having a wheel mounted on the roller,
An imaging step of imaging an area including at least wheels of the vehicle by an imaging means;
A brightness measurement step for measuring the brightness of the wheel imaged in the imaging step;
A vehicle position detection method comprising: a position detection step of detecting a position of the vehicle by specifying a position of the wheel based on a change in brightness obtained from a measurement result of the brightness measurement step.

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