JP2007046949A - Vehicle-mounted ground speed measuring apparatus and ground-speed measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a vehicle speed with high precision without being affected by irregularities of road surfaces. <P>SOLUTION: The ground speed measuring apparatus 10, which is mounted on a vehicle C for measuring the traveling speed of the vehicle with respect to the ground G, comprises a laser transmitter 11 for marking spot-like heated points P1 to P3 on the ground G with a predetermined time interval; a far-infrared camera 12 for photographing the heated points P1 to P3 marked on the ground G by the laser transmitter 11; and a calculation means 13 for calculating the vehicle speed V, by dividing the distance l between a plurality of heated-point images Q1 to Q3 on an image 20 photographed by the far-infrared camera 12 by a transmission time interval t of the laser transmitter 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an on-vehicle ground speed measuring device and a ground speed measuring method, and more particularly to an apparatus for accurately measuring a ground speed of a vehicle and using it for ABS, VSC, or the like.

  Technologies such as ABS (Anti-lock Brake System) and VSC (Vehicle Stability Control) have already been implemented as systems for improving the running stability of automobiles. A vehicle speed measuring device used in these systems generally calculates a vehicle speed from the number of rotations of a wheel. In reality, however, running wheels are subject to slipping, deformation, air pressure fluctuation, etc., so the ground speed at the center of gravity of the car body may not be measured accurately. A method to estimate the ground speed will be used. Then, if there is a difference between the estimated ground speed and the speed of each wheel, it is determined that a slip has occurred, and there is a possibility that the determination error will increase. Accurate measurement of the actual vehicle traveling speed (ground speed) is indispensable for improving the performance of the safety system, and it is desired that the vehicle speed can be accurately measured without being affected by wheel slip or deformation. .

For example, in Japanese Patent Application Laid-Open No. 5-273346, an ultrasonic wave is applied to the road surface, and the vehicle speed is measured from the frequency fluctuation due to the velocity of the reflected wave (Patent Document 1). In Japanese Patent Application Laid-Open No. 7-120554, an electromagnetic wave beam is transmitted toward the ground, and the vehicle speed is estimated from a change in the frequency difference or pulse width of the reflected beam (Patent Document 2). In Japanese Patent Application Laid-Open No. 9-178854, a laser is irradiated on the ground, and the vehicle speed is measured by the Doppler effect of reflected waves (Patent Document 3).
However, as described in each of the above publications, when a technique for measuring reflection when an ultrasonic wave, a beam, or a laser is irradiated on the ground is used, the reflection is disturbed due to the unevenness of the ground, and in some cases, the reflection The traveling direction may change, and there is a problem that a frequency change or the like is erroneously recognized.
JP-A-5-273346 JP-A-7-120554 JP-A-9-178854

  The present invention has been made in view of the above problems, and an object thereof is to enable accurate measurement of the ground speed of a vehicle without being affected by road surface unevenness.

In order to solve the above-mentioned problem, the present invention firstly is an in-vehicle ground speed measuring device for measuring a traveling speed (ground speed) of a vehicle with respect to a road surface,
Marking means for performing spot-like marking on the road surface at predetermined time intervals;
Photographing means for photographing the road surface marked by the marking means;
An in-vehicle device, comprising: an arithmetic unit that calculates a ground speed of a vehicle by dividing a distance between a plurality of markings on an image photographed by the photographing unit by a marking time interval of the marking unit. A ground speed measuring device is provided.

With the above configuration, since the speed relative to the road surface of the vehicle is obtained using an image obtained by photographing the marking attached to the road surface by the marking means, the distance between the markings on the image is affected even if the road surface is uneven. It is possible to prevent the occurrence of measurement errors due to road surface irregularities.
In addition, when the afterimage has arisen in the image | photographed marking, it is good to use the distance between the one ends of each marking for the distance between each said marking. Examples of the marking means include a heat source irradiation means, which will be described later, and a color material discharge means for discharging paint or the like in a spot shape.

The marking means is connected to a control means for controlling the marking time interval,
The control means preferably has a function of changing the marking time interval in accordance with a distance value between a plurality of markings acquired by the calculation means.

  Specifically, the control unit shortens the marking time interval of the marking unit when the distance between the plurality of markings acquired by the calculation unit is equal to or greater than a predetermined threshold, while the distance is a predetermined level. When it becomes less than a threshold value, it is good to perform control which extends a marking time interval.

  With the above configuration, when the traveling speed of the vehicle increases, there is a possibility that a plurality of markings may not be included in the image captured by the imaging means. In this case, control is performed to shorten the marking time interval. Thus, a plurality of markings can be taken in one image. On the other hand, when the traveling speed of the vehicle decreases, there may be a possibility that a large number of markings are captured in the image captured by the imaging means and the distance between the markings cannot be sufficiently secured. By performing control to extend the time interval, an appropriate number of markings can be taken in one image.

The computing means has a function of calculating a radius of curvature of a virtual circle on which a plurality of markings on an image photographed by the photographing means are on the circumference, or / and
It is preferable to have a function of calculating the peripheral speed by dividing the peripheral length between the markings on the virtual circle by the marking time interval.

  With the above configuration, the turning radius and the peripheral speed can be easily obtained simply by obtaining a virtual circle that connects a plurality of markings on the image photographed when the vehicle turns. By using these pieces of information, the vehicle side grasps the slip of each wheel of the vehicle, or detects whether the vehicle is driving along the corner angle on the map acquired from the car navigation system. Can contribute to high-accuracy running stability.

Secondly, the present invention is an in-vehicle ground speed measuring device for measuring a traveling speed (ground speed) of a vehicle with respect to a road surface,
Marking means for performing spot-like marking on the road surface at predetermined time intervals;
Photographing means for photographing the road surface marked by the marking means;
An on-vehicle ground speed comprising: an arithmetic means for calculating a ground speed by dividing a marking length displayed on an image photographed by the photographing means by an exposure time of the photographing means A measuring device is provided.

  With the above configuration, since the speed with respect to the road surface of the vehicle is obtained using an image obtained by photographing the marking applied to the road surface by the marking means in the same manner as described above, the marking length on the image is obtained even if there is unevenness on the road surface. Has no effect, and it is possible to prevent the occurrence of measurement errors due to road surface irregularities.

Control means for controlling the marking time interval is connected to the marking means,
The control means preferably has a function of changing the exposure time of the photographing means in accordance with the marking length acquired by the calculating means.

  Specifically, the control unit shortens the exposure time of the photographing unit when the marking length acquired by the calculation unit is equal to or greater than a predetermined threshold, while the marking length is less than the predetermined threshold. In such a case, it is preferable to perform control to extend the exposure time.

  With the above configuration, there is a possibility that the full length of the marking afterimage will not fit within the image captured by the imaging means when the vehicle traveling speed increases. In this case, control is performed to reduce the exposure time. Thus, an afterimage of marking can be contained in one image. On the other hand, if the running speed of the vehicle decreases, there is a possibility that an afterimage of the marking on the image taken by the photographing means cannot be secured sufficiently. In that case, by performing control to extend the exposure time. An afterimage having an appropriate length can be generated on the image.

The calculation means has a function of calculating a radius of curvature of a virtual circle on which a marking on an image photographed by the photographing means is on the circumference, or / and
It is preferable to have a function of calculating a peripheral speed by dividing the marking length on the virtual circle by an exposure time.
With the above configuration, the turning radius and the peripheral speed can be easily obtained simply by obtaining the virtual circle on which the marking on the image photographed when the vehicle turns.

  Preferably, the marking means is a heat source irradiation means, and the imaging means is a heat distribution imaging means.

  With the above configuration, a spot-like heating point can be generated on the road surface by irradiating the road surface with a heat source having a temperature higher than the road surface using the heat source irradiating means. A marking that is a heating point can be recognized from an image obtained by photographing the distribution. Further, since the heating point only recovers to the normal road surface temperature with time, there is an advantage that the road surface is not soiled or damaged. The heat source irradiation means may irradiate a cold medium having a temperature lower than that of the road surface.

Specifically, it is preferable that the heat source irradiation unit is a laser transmitter and the heat distribution photographing unit is a far infrared camera.
When a laser transmitter is used as in the above configuration, since the laser has good directivity, there is an advantage that a heating point can be accurately generated at a target point on the road surface and the shape of the heating point is stabilized. Further, since a tank for storing a heat source, paint, or the like for marking is not required, an increase in the weight of the vehicle can be suppressed, fuel efficiency can be improved, and the vehicle can be downsized.

Thirdly, the present invention is a ground speed measurement method for measuring a traveling speed of a vehicle with respect to a road surface,
Performing spot-shaped markings at predetermined time intervals on the road surface from the vehicle side;
A step of photographing a plurality of markings attached to the road surface with a photographing means mounted on a vehicle;
And a method of calculating a ground speed of the vehicle by dividing a distance between a plurality of markings on the captured image by a marking time interval. .

Fourthly, the present invention is a ground speed measurement method for measuring a traveling speed of a vehicle with respect to a road surface,
Performing spot-shaped markings at predetermined time intervals on the road surface from the vehicle side;
A step of photographing the marking attached to the road surface with an on-vehicle photographing means;
And a step of calculating a ground speed of the vehicle by dividing a marking length displayed on the photographed image by an exposure time of the photographing means. ing.

  As is clear from the above description, according to the present invention, the speed relative to the road surface of the vehicle is obtained using an image obtained by photographing the marking attached to the road surface by the marking means. The distance between markings on the image is not affected, and measurement errors due to road surface unevenness can be prevented.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a ground speed measuring device 10 mounted on a vehicle C.
The ground speed measuring device 10 includes a laser transmitter 11 (marking means) installed under the floor of the vehicle C and a far infrared camera 12 exposed under the floor of the vehicle C and installed immediately behind the laser transmitter 11. (Imaging means), calculation means 13 for calculating the traveling speed of the vehicle with respect to the road surface G based on the image taken by the far-infrared camera 12, laser control means 14 for controlling the transmission timing of the laser transmitter 11, and calculation And an output unit 15 that outputs the vehicle speed, which is the calculation result of the means 13, to an external device.

The laser transmitter 11 is configured to intermittently irradiate a road surface G with a laser heat source at predetermined time intervals to generate point-like heating points P1, P2, and P3 (marking) on the road surface G.
The far-infrared camera 12 captures a road surface G irradiated with a laser heat source from the laser transmitter 11 and captures an image range composed of L × W pixels. Note that L is the length of the vehicle C in the front-rear direction, and W is the length of the vehicle C in the width direction.

As shown in FIG. 2, the calculation means 13 divides the distance l between the plurality of heating point images Q 1, Q 2, Q 3 on the image 20 taken by the far-infrared camera 12 by the transmission time interval of the laser transmitter 11. Thus, the vehicle speed is calculated.
The laser control unit 14 shortens the laser irradiation time interval t of the laser transmitter 11 when the distance l between the plurality of heating point images Q1, Q2, and Q3 acquired by the calculation unit 13 is equal to or greater than a predetermined threshold value. On the other hand, control is performed to extend the laser irradiation time interval t when the distance l is less than a predetermined threshold.
The output unit 15 outputs the vehicle speed data calculated by the calculation means 13 to an external system such as ABS or VSC.

Next, the operation of the ground speed measuring device 10 will be described based on FIG.
While the vehicle C is traveling, the laser transmitter 11 intermittently irradiates the road surface G with a laser at a transmission time interval t so that n + 1 heating points P1, P2, and P3 are included in one image. (Step S1). At this time, the laser irradiation time of one time is sufficiently shortened so that the heating points P1, P2, and P3 generated when the laser hits the road surface G are formed in a dot shape.
When the road surface G irradiated with the laser is photographed by the far-infrared camera 12, an image 20 as shown in FIG. 2 is acquired (step S2). Image 20 has been captured during straight of the vehicle C, far afterimage length l _s which is dependent on the exposure time T (frame capture time) of the infrared camera 12 is generated, a line-shaped heating point image Q1, Q2 , Q3 are displayed at intervals. Therefore, in order to acquire the distance between the heating points P1, P2, and P2, the distance l between the one ends of the heating point images Q1, Q2, and Q3 is acquired.

Consider a case where t> T and V _max × nt <α × L, that is, a case where the exposure time T is sufficiently short and the entire distance to be measured l falls within a predetermined area of the image 20.
Note that n is the number of distances 1 to be averaged, α is an effective coefficient (<1) that gives a margin to the image area, V _max is the maximum measurable speed, and V is the vehicle speed.
First, the heating point images Q1, Q2, and Q3 of the image 20 are recognized by image processing, and a distance l _i (i = 1, 2 in the present embodiment) between one end of each heating point image Q1, Q2, and Q3 is acquired. , The average distance l is calculated by Equation 1.

Next, the vehicle speed V can be calculated by dividing the distance l by the laser transmission time interval t according to Equation 2 (step S3).

Here, when the distance l previously obtained by the computing means 13 satisfies the condition of l <(αL / 2n) (step S4), the control means 14 determines the longitudinal length L of the image 20 It is determined that the distance l is too narrow, and control is performed to extend the laser transmission time interval t to t = 2t (step S5).
Further, when the distance l previously obtained by the computing means 13 does not satisfy the condition of l <(αL / 2n) (step S4), and satisfies the condition of l <(αL / n) In step S6, it is determined that the distance l is within an appropriate range with respect to the longitudinal length L of the image 20, and the laser transmission time interval t is not changed to t = t (step S7).
If the distance l previously obtained by the computing means 13 does not satisfy the condition of l <(αL / n) (step S6), the distance l becomes too large with respect to the longitudinal length L of the image 20. Then, control is performed to shorten the laser transmission time interval t to t = t / 2 (step S8).

Next, a procedure for calculating the turning radius r and the peripheral speed V ₁ when the vehicle C is traveling on a curve will be described.
As shown in FIG. 4, when the vehicle C is curved, the heating point images Q4, Q5, and Q6 are imaged side by side in a virtual arc shape on the image 21 photographed by the far infrared camera 12. At this time, the computing means 13 can determine the radius of curvature of the virtual circle as the turning radius r by setting a virtual circle in which the three heating point images Q4, Q5, and Q6 are arranged on the circumference.
For the peripheral speed V ₁ of the vehicle C, first, the peripheral length l of the virtual arc connecting the adjacent heating point images Q4 and Q5 is calculated by the following Equation 3.

Next, the peripheral speed V ₁ can be calculated by dividing the peripheral length l by the laser transmission time interval t in the following Equation 4.

According to the above configuration, spot-like heating points P1, P2, and P3 are generated on the road surface G by the laser transmitter 11, and the image 20 obtained by photographing them is used to obtain the speed V with respect to the road surface G of the vehicle C. Therefore, even if the road surface G has irregularities or the like, the distance l between the heating point images Q1, Q2 and Q3 on the image is not affected, and measurement errors due to the irregularities on the road surface G are prevented.
Further, since the laser transmitter 11 is employed as a marking means for the road surface G, the heating points P1, P2, and P3 only recover to the normal road surface temperature over time, and the merit that the road surface is not soiled or damaged. There is.

  Furthermore, when the traveling speed of the vehicle C increases, there is a possibility that all the heating point images Q1, Q2, Q3 will not fit in the image 20 taken by the far-infrared camera 12, but in that case, the laser Since the control means 14 performs control to shorten the laser transmission time interval t, a plurality of heating points P1, P2, and P3 can be photographed in one image. On the other hand, when the traveling speed of the vehicle C decreases, there is a possibility that a large number of heating points P1, P2, and P3 are captured in the image 20 captured by the far-infrared camera 12, and the distance between them cannot be sufficiently secured. In such a case, an appropriate number of heating points P1, P2, and P3 can be photographed in one image by performing control to extend the laser transmission time interval t.

Further, since the far-infrared camera 12 only needs to be able to sense a certain range of temperatures of the heating points P1, P2, and P3, the sensitivity of the image sensor does not necessarily have to be high performance, and is realized with an inexpensive configuration. be able to.
The far-infrared camera 12 may be a line sensor in which the number of pixels in the vehicle width direction W of the captured image is 1. That is, in order to measure the distance l between the heating point images Q1, Q2, and Q3 when traveling straight, at least one row of pixels in the width direction may be used, so the distance l can be measured with an inexpensive line sensor. However, in that case, the straight vehicle speed can be obtained, but the peripheral speed and turning radius cannot be obtained.

As a modification, it is preferable that the laser intensity of the laser transmitter 11 is adjusted by the laser control means 14 in accordance with the temperature of the road surface G.
That is, since the far-infrared camera 12 can also detect road surface temperatures other than the heating points P1, P2, and P3, the laser control means 14 reduces the laser intensity when the road surface temperature is low in winter according to the road surface temperature obtained by the arithmetic means 13. On the other hand, if the control is performed to increase the laser intensity when the road surface temperature is high in summer, an optimum imaging result can be obtained and the load of image processing can be reduced.

5 to 7 show a second embodiment.
The difference from the first embodiment is that the vehicle speed is calculated based on the afterimage length l _s (marking length) of the heating point image Q7 in the photographed image.

While the vehicle C is traveling, the laser transmitter 11 intermittently irradiates the road surface G with a laser at a transmission time interval t so that one heating point P1 is included in one image. Then, when the road surface G irradiated with the laser is photographed by the far-infrared camera 12 with the exposure time T, an image 30 as shown in FIG. 5 is acquired (step S11). Image 30 has been captured during straight of the vehicle C, far afterimage length l _s which is dependent on the exposure time T (frame capture time) of the infrared camera 12 is generated, a line-shaped heating point image Q7 is displayed Is done.

t <T, when the _{V max × T <α × L} , i.e., longer exposure time T, the case where the total length of the afterimage length l _s to be measured within a predetermined area of the image 30 are taken to fit Think.
First, recognize heated point image Q7 image 30 in the image processing, to obtain a residual image length l _s of the heating point image Q7. Then, by dividing the exposure time T of the laser oscillator 11 the distance _{l s} by Equation 5, and calculates the vehicle speed V (step S12).

When the afterimage length l _s previously acquired by the calculation unit 13 satisfies the condition of l _s <(αL / 2) (step S13), the control unit 14 determines the front-rear length L of the image 30. It determines that the residual image length l _s is too short Te, performs control for extending the exposure time T as T = 2T (step S14).
Further, the afterimage length l _s previously acquired by the computing means 13 does not satisfy the condition of l _s <(αL / 2) (step S13), and satisfies the condition of l _s <(αL). if it is (step S15), and afterimage length l _s with respect to the longitudinal length L of the image 30 is judged to be appropriate range, without changing the exposure time T as T = T (step S16).
If the afterimage length l _s previously obtained by the computing means 13 does not satisfy the condition of l _s <(αL) (step S15), the afterimage length l with respect to the longitudinal length L of the image 30 is determined. It is determined that _s is too large, and control is performed to shorten the exposure time T to T = T / 2 (step S17).

Next, a procedure for calculating the turning radius r and the peripheral speed V ₁ when the vehicle C is traveling on a curve will be described.
When the vehicle C is curved, the heating point image Q8 is captured in an arc shape on the image 31 captured by the far-infrared camera 12, as shown in FIG. At this time, the calculation means 13 can determine the radius of curvature of the virtual circle as the turning radius r by setting a virtual circle in which the heating point image Q8 is arranged on the circumference.
As for the peripheral velocity V _l of the vehicle C, as shown in Equation 5 below, by dividing the circumferential length l of the heating point image Q8 exposure time T, it can be calculated peripheral velocity V _l.

FIG. 8 shows a third embodiment.
The difference from the first and second embodiments is that instead of irradiating the road surface G with laser, exhaust heat generated by the engine 43 is used.

The ground speed measurement device 40 of the present embodiment includes an exhaust separation compression means 42 that separates and compresses exhaust gas from an engine 43 mounted on the vehicle from an exhaust passage, and an exhaust injection means 41 (exposed under the floor of the vehicle C) ( Heat source irradiation means).
The exhaust injection means 41 generates spot-like heating points P1, P2, and P3 on the road surface G by intermittently injecting high-pressure and high-temperature exhaust gas supplied from the exhaust separation and compression means 42 by opening and closing a valve or the like. ing.
With the above configuration, since the waste heat generated in the vehicle C is effectively used as a heating source for the road surface G, there is an advantage that it is not necessary to prepare a separate heat source and the cost can be reduced. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

It is a block diagram which shows the ground speed measuring apparatus of 1st Embodiment of this invention. It is drawing which shows the picked-up image at the time of straight advance of 1st Embodiment. It is a flowchart which shows the control flow of 1st Embodiment. It is drawing which shows the picked-up image at the time of turning of 1st Embodiment. It is drawing which shows the picked-up image at the time of straight ahead of 2nd Embodiment. It is a flowchart which shows the control flow of 2nd Embodiment. It is drawing which shows the picked-up image at the time of turning of 2nd Embodiment. It is a block diagram which shows the ground speed measuring apparatus of 3rd Embodiment.

Explanation of symbols

10 Ground speed measuring device 11 Laser transmitter (marking means)
12 Far-infrared camera (photographing means)
13 Laser control means 14 Calculation means 15 Output unit 20, 21, 30, 31 Photographed image 41 Exhaust injection means 42 Exhaust separation compression means 43 Engine C Vehicles P1 to P3 Heating points S1 to S8 Heating point images

Claims (10)

An on-vehicle ground speed measuring device that measures the traveling speed (ground speed) of a vehicle with respect to a road surface,
Marking means for performing spot-like marking on the road surface at predetermined time intervals;
Photographing means for photographing the road surface marked by the marking means;
An in-vehicle device, comprising: an arithmetic unit that calculates a ground speed of a vehicle by dividing a distance between a plurality of markings on an image photographed by the photographing unit by a marking time interval of the marking unit. Ground speed measuring device. The marking means is connected to a control means for controlling the marking time interval,
The on-vehicle ground speed measuring device according to claim 1, wherein the control unit has a function of changing the marking time interval according to a distance value between a plurality of markings acquired by the calculation unit. The computing means has a function of calculating a radius of curvature of a virtual circle on which a plurality of markings on an image photographed by the photographing means are on the circumference, or / and
The in-vehicle ground speed measuring device according to claim 1 or 2, further comprising a function of calculating a peripheral speed by dividing a peripheral length between the markings on the virtual circle by a marking time interval. An on-vehicle ground speed measuring device that measures the traveling speed (ground speed) of a vehicle with respect to a road surface,
Marking means for performing spot-like marking on the road surface at predetermined time intervals;
Photographing means for photographing the road surface marked by the marking means;
An on-vehicle ground speed comprising: an arithmetic means for calculating a ground speed by dividing a marking length displayed on an image photographed by the photographing means by an exposure time of the photographing means Measuring device. Control means for controlling the marking time interval is connected to the marking means,
The in-vehicle ground speed measuring device according to claim 4, wherein the control unit has a function of changing an exposure time of the imaging unit according to a marking length acquired by the calculation unit. The calculation means has a function of calculating a radius of curvature of a virtual circle on which a marking on an image photographed by the photographing means is on the circumference, or / and
The in-vehicle ground speed measuring device according to claim 4 or 5, further comprising a function of calculating a peripheral speed by dividing the marking length on the virtual circle by an exposure time.   The in-vehicle apparatus according to any one of claims 1 to 6, wherein the marking means is a heat source irradiation means for heating the road surface in a spot shape, and the imaging means is a heat distribution imaging means for visualizing a heat distribution on the road surface. Ground speed measuring device for use.   The on-vehicle ground speed measuring device according to claim 7, wherein the heat source irradiating means is a laser transmitter, and the heat distribution photographing means is a far-infrared camera. A ground speed measurement method for measuring a traveling speed of a vehicle with respect to a road surface,
Performing spot-shaped markings at predetermined time intervals on the road surface from the vehicle side;
A step of photographing a plurality of markings attached to the road surface with a photographing means mounted on a vehicle;
And calculating a ground speed of the vehicle by dividing a distance between a plurality of markings on the photographed image by a marking time interval. A ground speed measurement method for measuring a traveling speed of a vehicle with respect to a road surface,
Performing spot-shaped markings at predetermined time intervals on the road surface from the vehicle side;
A step of photographing the marking attached to the road surface with an on-vehicle photographing means;
And a step of calculating a ground speed of the vehicle by dividing a marking length displayed on the photographed image by an exposure time of the photographing means.

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