JP2697307B2 - Road surface identification device and its application device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device that is mounted on a vehicle and used to determine the state of a road surface on which the vehicle runs (snow, gravel, asphalt, wet, frozen, etc.) and an application device thereof.

2. Description of the Related Art An anti-lock brake system (ABS) (or anti-skid system) is a system that shortens a vehicle braking distance as much as possible by controlling a brake so as to obtain a slip ratio that maximizes a braking force. It is. Since the slip ratio at which the braking force becomes maximum differs depending on the road surface condition, it is necessary to determine the road surface condition in order to perform the optimal ABS control according to the road surface condition. In addition, in order to absorb the unpleasant vibration and secure the comfortable riding comfort of the vehicle by controlling the suspension according to the unevenness of the road surface, it is necessary to identify the gravel road having large unevenness.

One of the methods for optically determining the road surface state in a non-contact manner is
Toshio Takehana, "Road Condition Sensor Using Polarization Characteristics of Road Reflection", Technical Contact, Vol.27, No.3 (1989), pp.158-1
There is one shown in 64. In this method, a light emitting element and a light receiving element are arranged such that an incident angle and a reflection angle become Brewster angles (53 degrees). This is based on the fact that the degree of polarization approaches 1 on a wet road because it is close to a mirror surface, and the degree of polarization approaches 0 on a dry road due to its diffusion characteristics.

However, this method is for discriminating whether the asphalt road surface is in a wet state or a dry state, and cannot distinguish a gravel road or a snowy road. In addition, since the arrangement angle between the light emitting element and the light receiving element is determined by the Brewster angle, strict alignment is required, and
The light emitting element and the light receiving element must be provided at a considerable distance.

Road surface estimation for application of anti-skid control (Katsuhiro Oba et al. “Road surface estimation using Fuzzy Logic”, Preprints 881. Showa 63-
5,881028), but lacks versatility due to its application to anti-skid systems.

DISCLOSURE OF THE INVENTION The present invention provides a road surface discriminating apparatus which can be applied to discrimination of many kinds of road surface conditions and thereby has many application possibilities.

The basic configuration of the road surface identification device according to the present invention is as follows. That is, this road surface determination device includes a first light source that projects light toward the road surface, a first spatial filter unit, and a first light receiving unit, and reflects the projection light of the first light source from the road surface. A first spatial filter light receiving optical system for receiving light by the first light receiving means through the first spatial filter means and outputting an electric signal representing the received reflected light;
A second light receiving optical system for receiving the reflected light of the projection light of the first light source from the road surface by the second light receiving means and outputting an electric signal representing the received reflected light;
A first signal processing circuit for detecting an intensity of a center frequency component corresponding to a spatial frequency of the first spatial filter means from an electric signal output from the first spatial filter light receiving optical system; A second signal processing circuit for detecting the intensity of a low frequency component corresponding to a spatial frequency lower than the spatial frequency of the first spatial filter means from the electric signal output from the optical system, and the first signal processing A determination unit is provided for determining a road surface state based on the center frequency component detected by the circuit and the low frequency component intensity detected by the second signal processing circuit.

Preferably, the first light source, the first spatial filter light receiving optical system, and the second light receiving optical system are arranged such that the first and second light receiving means receive diffusely reflected light from a road surface. I have.

In the first embodiment of the present invention, the second light receiving optical system is included in the first spatial filter light receiving optical system, and the second light receiving means is the first light receiving means. An electric signal output from the first light receiving means is provided to the first signal processing circuit and the second signal processing circuit.

In a second embodiment, a part of the second light receiving optical system is included in the first spatial filter light receiving optical system, and
Receive the reflected light which does not pass through the spatial filter means.

In a third embodiment, the second light receiving optical system includes a second spatial filter having a spatial frequency lower than the spatial frequency of the first spatial filter means. The second light receiving means receives the reflected light through the second spatial filter.

The spatial frequency characteristics of a road surface (especially for diffused light) have distinct characteristics in its spatial frequency spectrum. In other words, the intensity is high in a region where the spatial frequency is low, and the intensity decreases as the spatial frequency increases. The inventors have found that in the low-frequency region where the intensity is large, the intensity varies depending on the road surface condition. That is, it was found that snow, gravel, (sand), and asphalt (concrete) were in descending order of strength.

The spatial frequency (center frequency component) of the first spatial filter optical system is set to a relatively high part in a detectable spatial frequency region. The spatial frequency of the low frequency component to be extracted is set in a region lower than the center frequency, where the intensity changes as much as possible according to the road surface condition.

The intensity of the low frequency component is normalized (normalized) by the intensity of the center frequency component. As a result, factors such as a change in light amount and a change in reflectance are removed. By comparing the normalized low frequency component intensity with a predetermined threshold value, at least one of snow, gravel, and asphalt can be determined.

The wet state of the road surface, especially the asphalt road surface, is determined based on the specularly reflected light.

In this case, a second light source that projects light toward the road surface and a third light receiving optical system including a third light receiving element are provided. These second light source and third light receiving optical system
The third light receiving element is arranged to receive regular reflection light of the projection light of the second light source from a road surface. The determining means determines the wet state of the road surface based on the output signal of the third light receiving element.

In a preferred embodiment, a light amount detector for detecting the light amount of the projection light of the second light source is further provided. The determining means determines a wet state of the road surface based on a value obtained by normalizing an output signal of the third light receiving element with a light amount detected by the light amount detector.
With this, it is possible to eliminate the adverse effect of the light amount fluctuation of the second light source.

In another preferred embodiment, the third light receiving optical system is included in the first spatial filter light receiving optical system.
The third light receiving element is the first light receiving element.

In this case, the output signal of the first light receiving element is divided into a first signal component caused by the projection light of the first light source and a second signal component caused by the projection light of the second light source. And separating means for separating the two. The first signal processing circuit detects a diffuse light center frequency component intensity from the first signal component separated by the separation means. A third signal processing circuit is provided for detecting the intensity of the central frequency component of the regular reflection light from the second signal component separated by the separation means.

The determining means determines a wet state of the road surface based on a ratio between the intensity of the central frequency component of the regular reflected light and the intensity of the central frequency component of the diffused light. Since this ratio becomes considerably large on a wet road surface, accurate judgment can be expected.

The separation of the above signals can be realized as follows. A drive circuit is provided for driving the first light source and the second light source based on signals having different phases or signals having different frequencies. The separation means is realized by a demodulation circuit that demodulates a signal modulated by a signal having a different phase or a signal modulated by a signal having a different frequency.

Road freeze can also be determined. A temperature sensor for measuring road surface temperature or air temperature is provided. When the determination unit determines that the temperature is wet, if the temperature detected by the temperature sensor is equal to or lower than a predetermined value, the determination unit determines that the temperature is frozen.

A snowy road can also be determined by a diffuse light component. That is, there is provided a fourth signal processing circuit for detecting an extremely low frequency diffused light component from the output signal of the first light receiving element or the second light receiving element. The determining means determines that snow is present when the diffused light component detected by the fourth signal processing circuit exceeds a predetermined value.

Preferably, the first light source includes a plurality of light emitting elements and a plurality of lenses disposed in front of the light emitting elements in correspondence with the light emitting elements. The optical axis of the light emitting element and the optical axis of the corresponding lens are arranged so as to be shifted from each other. Thereby, the spread of the projection light of the first light source is prevented.

As an example, the first signal processing circuit has a tracking circuit.
Includes band pass filter. A signal representing the ground speed is output from the tracking band pass filter. The pass band of the tracking band pass filter is controlled based on the speed signal. This road surface identification device can also detect the ground speed.

As an example, the second signal processing circuit includes a tracking low pass filter whose cutoff frequency is controlled based on the speed signal.

The present invention has a more simplified configuration (in particular, an electrical configuration).
Is provided. This road surface identification device
A light source for projecting light toward a road surface, a spatial filter light receiving optical system for receiving, through a spatial filter, diffusely reflected light of the light projected from the light source from the road surface, and outputting an electric signal representing the received reflected light; A signal processing circuit for detecting a center frequency component corresponding to the spatial frequency of the spatial filter from the electrical signal output from the optical system; a zero-crossing of the center frequency component output from the signal processing circuit;
A first counter for counting points, a second counter for counting zero-cross points of an electric signal output from the spatial filter light receiving optical system, and a count value of the first counter and a count value of the second counter And determining means for determining the road surface condition based on the above.

Also in this configuration, at least one of snow, gravel, and asphalt is determined by the determination means.

In one embodiment, the discriminating means makes a discrimination every predetermined time, and the first and second counters start counting operation. In another embodiment, each time the count value of the first counter reaches a predetermined number, the determination means makes a determination, and the first and second counters start counting.

In still another preferred embodiment, a plurality of pairs of the first counter and the second counter are provided. The first
The start time of the counting operation of the second counter is set differently for each pair. As a result, the accuracy can be maintained and the determination cycle can be shortened.

The above-described simplified road surface identification device can also be developed so as to be able to determine whether it is wet or frozen.

In all of the above-described road surface determination devices, the following configuration is recommended in order to prevent the diffused reflected light from increasing in the case of snow and preventing the processing circuit from being saturated.

That is, there are provided an amplifier circuit for an electric signal including a light receiving signal, and means for controlling the amplification factor of the amplifier circuit in accordance with the result of the determination by the determination circuit.

Instead, control means is provided for changing the amount of light emitted by the first or second light source in accordance with the result of determination by the determination circuit.

The present invention can be developed not only for determining the road surface but also for determining the surface of an object.

The present invention is further applied to slip warning of a vehicle, brake or accelerator control for anti-skid, suspension control of a vehicle, and the like.

The present invention provides a vehicle or a traveling body provided with a road surface identification device.

Further features of the present invention will become more apparent in the description of embodiments with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 show an optical configuration (No. 1) of a road surface discriminating apparatus. FIG. 1 is a perspective view, FIG. 2 is a longitudinal sectional view, and FIG. It is a front view of the optical system for light.

4 and 5 schematically show examples of the configuration of a light source for road illumination. FIG. 4 is a plan view, and FIG. 5 is a sectional view.

FIG. 6 is a sectional view showing a specific example of a light source for road illumination.

 FIG. 7 is a graph showing the measurement results.

FIG. 8 is a block diagram showing an electrical configuration (No. 1) of the road surface identification device.

 FIG. 9 is a circuit diagram showing a specific example of the differential amplifier circuit.

FIG. 10 is a circuit diagram showing a specific example of a tracking band pass filter.

FIG. 11 is a block diagram showing a specific example of the amplitude detection circuit.

FIG. 12 is a flowchart showing a road surface determination algorithm (1).

FIG. 13 is a flowchart showing a road surface determination algorithm (2).

FIG. 14 is a flowchart showing a road surface determination algorithm (3).

FIG. 15 is a flowchart showing a road surface determination algorithm (No. 4).

FIG. 16 is a block diagram showing an electrical configuration (part 2) of the road surface identification device.

FIG. 17 is a block diagram showing an electrical configuration (part 3) of the road surface identification device.

FIG. 18 is a block diagram showing a configuration example of a dual-comb filter.

FIG. 19 is a waveform diagram of the input signal, and FIG. 20 is an enlarged view of a part thereof.

FIG. 21 is a block diagram showing an electrical configuration (part 4) of the road surface identification device.

FIG. 22 is a block diagram showing an electrical configuration (part 5) of the road surface identification device.

FIG. 23 is a perspective view showing an optical configuration (part 2) of the road surface identification device, and FIG. 24 is a front view.

FIG. 25 is a block diagram showing an electrical configuration (part 6) of the road surface identification device.

FIG. 26 is a front view showing an optical configuration (No. 3) of the road surface identification device.

FIG. 27 is a block diagram showing an electrical configuration (part 7) of the road surface identification device.

FIG. 28 is a flowchart showing a road surface determination algorithm (5).

FIG. 29 is a flowchart showing a road surface determination algorithm (6).

FIG. 30 is a flowchart showing a road surface determination algorithm (7).

FIG. 31 is a block diagram showing an electrical configuration (No. 8) of the road surface identification device.

 FIG. 32 is a waveform diagram showing signals on a snowy road.

 FIG. 33 is a waveform diagram showing signals on a gravel road.

FIG. 34 is a block diagram showing an electrical configuration (No. 9) of the road surface identification device.

FIG. 35 is a block diagram showing an electrical configuration (No. 10) of the road surface identification device.

FIG. 36 is a time chart showing the operation of the counter.

FIG. 37 is a block diagram showing an electrical configuration (No. 11) of the road surface identification device.

FIG. 38 is a block diagram showing an electrical configuration (No. 12) of the road surface identification device.

FIG. 39 shows a device that issues a warning according to the road surface determination result.

Figure 40 shows the antilock brake system (ABS)
Is shown.

 FIG. 41 shows an optimum slip ratio table.

 FIG. 42 shows a vehicle equipped with ABS.

FIG. 43 shows a vehicle equipped with a suspension control device.

 FIG. 44 is a cross-sectional view of the shock absorber.

BEST MODE FOR CARRYING OUT THE INVENTION A road surface identification device is generally mounted on a vehicle. Light is projected from the optical system of the road surface identification device toward the road surface, and the reflected light from the road surface is received by the optical system. The road surface state is determined by the signal processing circuit based on the electric signal obtained from the optical system.

In this embodiment, representative examples of the road surface conditions identified are as follows.

Snow Asphalt (or concrete) Gravel (also soil or sand) In this example, it is also determined whether the road surface is frozen.

Further, in this embodiment, the asphalt (concrete) road surface can be subdivided into the following two states.

Wet asphalt (concrete) Dry asphalt (concrete) Accordingly, aspects of the discrimination include identifying any one of the above-mentioned road surface conditions and distinguishing any two or more road surface conditions. . The representative determination modes are as follows.

a. Identification of snowy roads b. Identification of asphalt roads (concrete roads) c. Identification of gravel roads (soil or sandways) d. Identification of frozen road surfaces e. Identification of wet asphalt roads f. Identification of dry asphalt roads g. Distinction between snowy road and asphalt road h. Distinction between snowy road and gravel road i. Distinction between asphalt road and gravel road j. Distinction between snowy road and asphalt road and gravel road k. Above g., I. And j. To judge the asphalt road between wet and dry m. m. To judge the presence or absence of freezing in the above g., h., i., j. and k. The following description focuses on the mode of m. Above, which has the most types of road surface conditions. By extracting only a necessary part of the optical configuration, a required part of the electrical configuration, and a required part of the algorithm, A. ~
Needless to say, a road surface determining apparatus and method capable of determining a road surface in any mode among k.

(1) Optical Configuration of Road Surface Discrimination Device (Part 1) FIGS. 1 to 3 show the first optical configuration of the road surface discrimination device.
This is an example. To reduce the number of drawings,
In this optical system, all the optical elements necessary for actually executing all of several road surface determination algorithms described later are depicted. Conversely, optical elements that are not required to execute a certain road surface identification algorithm are included in this optical system. FIGS. 1 to 3 can be said to represent the optical elements included in the optical systems of some road surface discriminating devices. This also applies to the signal processing circuit shown in FIG. Therefore, if this optical system and the signal processing circuit shown in FIG. 8 are used, the road surface can be distinguished in the above-mentioned m. A.
In order to realize a road surface discrimination device capable of discriminating the road surface in any one of the modes (1) to (k), unnecessary optical elements and electric circuit elements may be removed.

A light source for road illumination 11 and a light source for regular reflection light 12 are included in the optical system. Each of these light sources 11 and 12 is constituted by a light emitting diode. A preferred configuration example of the road illumination light source 11 will be described later. The road illumination light source 11 projects light obliquely downward in the traveling direction of the vehicle. The light source 12 for regular reflection light projects light obliquely downward in a direction orthogonal to the light source. Preferably, the wavelengths of light emitted from these light sources 11 and 12 are different. By this, the road surface of the light of our light source
Light reflected from the LD (the road is also represented by LD) can be separated by an optical filter.

The light receiving optical system for diffusely reflected light from the road surface is a light receiving lens 21,
A slit plate 22 and a collimating lens 24 are included. The focal point of the light receiving lens 21 and the focal point of the collimating lens 24 are at the same position, and the slit (aperture) 22a of the slit plate 22 is located at these focal points. The slit 22a is elongated in a direction perpendicular to the traveling direction of the vehicle. Thus, the optical system is called a telecentric optical system. That is, of the reflected light from the road surface LD, only light that is perpendicular to the road surface LD and parallel to each other (in FIG. 2) is received by the light receiving lens 21.
And is passed through the slit 22a. Slit 2
The light passing through 2a is collimated by the collimating lens 24. Light from the light source 11 is obliquely incident on the road surface LD. Road surface
Only light vertically reflected from the LD passes through the slit 22a. In this way, only the diffusely reflected light from the road surface LD is collimated by the comerite lens 24 and enters the spatial filter optical system (ie, the specularly reflected light from the road surface LD does not enter the spatial filter optical system).

Preferably, the optical filter 23 is arranged at the position of the slit 22a of the slit plate 22. This filter 23 has a wavelength selectivity that allows only the light projected from the road surface illumination light source 11 to pass. This prevents light from the regular reflection light source 12 and other disturbance light (sunlight, light from road lighting, etc.) from entering the spatial filter optical system. The projection light of the light source 11 is preferably infrared light.

Spatial filter optical system is grating plate (slit array) 2
5, including a prism array 26, a condenser lens 27 and two photodetectors (light receiving elements, for example, photodiodes or phototransistors) 31A and 31B. Basically prism
Array 26 performs a spatial filtering action.

The prism array 26 is composed of a number of prisms. These prisms are arranged in the traveling direction of the vehicle and extend in a direction perpendicular to the traveling direction. Preferably, prism array 26 is integrally molded. The light collimated by the collimating lens 24 is separated by refraction by the prisms of the prism array 26 alternately back and forth (based on the traveling direction) by a constant pitch width. These separated lights are respectively condensed by the condenser lens 27, and
Incident on the photodetectors 31A and 31B.

In FIG. 2, light indicated by a dashed line enters the photodetector 31A, and light indicated by a broken line enters the photodetector 31B. The width of these lights depends on the arrangement period of the prism. The arrangement period of the prism defines the characteristic (period) of the spatial filter.

The grid plate (slit array) 25 is formed with a number of slits arranged in the traveling direction of the vehicle and extending in a direction perpendicular to the traveling direction. The arrangement period of these slits is twice the arrangement period of the prisms in the prism array 26. Of the light collimated by the collimating lens 24, the light that has passed through the slit enters the prism array 27 as described above, is separated, and is alternately spatially separated.
The light is received by the photodetectors 31A and 31B. The grating plate 25 prevents stray light from entering the prism array 27.

The photodetectors 31A and 31B are arranged at intervals in the traveling direction of the vehicle. This interval is determined by the period of the prism in the prism array 26 and the magnification of the condenser lens 27. Mirrors 28 are provided on both sides of the photodetectors 31A and 31B, and serve to make the light not condensed on the light receiving surfaces of the photodetectors 31A and 31B by the lens 27 enter the photodetectors 31A and 31B as much as possible.

As described later, the output signals of the two photodetectors 31A and 31B are provided to a differential amplifier circuit, and the difference between them is calculated. The output signal of the differential amplifier circuit includes a frequency component (depending on the speed of the vehicle) corresponding to a spatial frequency component representing a road surface state that causes fluctuations in diffuse reflected light, including road surface irregularities.

The light incident on the photodetector 31A and the light incident on the photodetector 31B are out of phase by a half period of the spatial period selected by the spatial filter. Therefore, both photodetectors 31
By taking the difference between the output signals of A and 31B, the spatial center frequency component is doubled. Mainly direct current (DC) components are canceled by this differential processing.

The light source 12 for specular reflection light and the photodetector 32 for specular reflection light are incident on the photodetector 32 at an incident angle of the light projected from the light source 12 with respect to the road surface LD in a plane orthogonal to the traveling direction of the vehicle. It is arranged so that the reflection angle of the reflected light from the road surface is equal. The angle of incidence and the angle of reflection are the Brewster angle (53
) Can be expected to reduce the size of the optical system. Preferably, on the front surface of the photodetector 12, an optical filter that allows only the light having the wavelength of the projection light of the light source 32 to pass, and a condenser lens are arranged.

The road surface thermometer 33 measures the road surface temperature, and is realized by, for example, an infrared radiation thermometer. Road surface thermometer 33
May not be included in the optical system but may be provided in another appropriate place in the vehicle.

further. A projection light amount monitoring photodetector 34 for receiving a part of the projection light of the regular reflection light source 12 is provided. This light detector 34 will be described later.

FIGS. 4 and 5 show an example of the configuration of the light source 11 for road illumination. The light source 11 has a large number of two-dimensionally arranged light emitting elements (for example, light emitting diodes) 11a and a large number of two-dimensionally arranged convex lenses 13a for condensing and projecting light from these light emitting elements 11a. And a lens array 13. One light emitting element 11a and one lens 1
3a is compatible. Although the optical axes of the light emitting element and the lens pair located near the center are almost the same,
The lens 13a corresponding to the optical axis of the light emitting element 11a as going to the periphery
Is shifted so that the light condensed and projected by the lens 13a approaches the center as much as possible. As a result, the light projected from the light source 11 does not spread so much, and converges in the narrowest possible range to illuminate the road surface LD.
That is, the light use efficiency is improved, and the number of light emitting elements constituting the light source 11 can be reduced.

FIG. 6 shows a more practical form of the light source 11 for road illumination. Many light emitting elements 11a are mounted on a printed wiring board 14 and connected to a wiring pattern on the board 14. The light emitting element 11a is provided on a holder 15 fixed to the substrate 14.
In the recess. A light shielding plate 16 is provided so as to cover the periphery (excluding the front) of each light emitting element 11a. A lens array 13 is disposed in front of the light emitting element 11a, and is fixed to a light shielding plate 16. The optical axis of the lens 13a corresponding to the light emitting element 11a is shifted.

(2) Principle of Road Surface Discrimination FIG. 7 shows an actual measurement example of a spatial frequency spectrum represented by a differential signal between the output signal of the photodetector 31A and the output signal of the photodetector 31B. This graph is obtained by actually measuring three types of road surface conditions, that is, a snowy road, a gravel road and an asphalt road.

The frequency (electrical center frequency) f of the center frequency signal component included in the output differential signals of the photodetectors 31A and 31B is the product of the spatial center frequency μ selected by the configuration of the spatial filter and the vehicle speed v. Is represented by

f = μ × v Expression (1) The spatial center frequency μ is uniquely determined by the configuration of the spatial filter. The road surface period (the period of the road surface state that causes the diffuse reflected light to change including the road surface irregularities) selected by the spatial filter is set to 4 (mm) here.
FIG. 7 shows a frequency spectrum obtained by performing a Fourier transform (FFT: fast Fourier transform) on an electric signal obtained by actual measurement.
This is normalized by the spatial center frequency μ. Data on snow, gravel and asphalt
Normalization is performed so that the peak value (intensity) at the spatial center frequency μ matches.

As can be seen from this graph, there is a large and clear difference between the snowy road, the gravel road and the asphalt road at the intensity of the spatial frequency component lower than the spatial center frequency μ (for example, the band below μ / 4). is there. These differences are around one digit (10 times) or more than one digit. The difference between the intensities in the three types of road surface conditions increases as the spatial frequency decreases.

Therefore, the value obtained by normalizing the low-frequency component intensity of the spatial frequency (for example, at a frequency of μ / 4 or μ / 10) with the center frequency component intensity (this is [low-frequency component intensity / center frequency component intensity] = Db / Da ) Can be distinguished from snowy roads, gravel roads and asphalt roads. The threshold values TH1 and TH2 used for distinguishing these values may be set in the middle of the above value Db / Da in each state. Referring to FIG. 7, if the value Db / Da is larger than threshold value TH1, the road is snowy,
If it is between the threshold values TH1 and TH2, it is determined to be a gravel road, and if it is less than the threshold value TH2, it is determined to be an asphalt road.

Here, the snowy road is fresh snow immediately after snowfall (snow white on all surfaces)
Rather, there is traffic of vehicles and people, the surface of the snow is rough, and there are relatively large (greater than gravel) irregularities (surface conditions that cause a change in the amount of diffuse reflection)
It is.

Gravel-filled dirt roads and sandways have a similar tendency to gravel roads, and the frequency spectrum of concrete roads is almost the same as that of asphalt roads.

(3) Electrical Configuration of Road Surface Discriminating Device (Part 1) FIG. 8 shows an example of the configuration of a signal processing circuit included in the road surface discriminating device.

Output signals of the photodetectors 31A and 31B are supplied to a differential amplifier circuit 51, and a signal representing the difference is output from the circuit 51.

FIG. 9 shows a configuration example of the photodetectors 31A and 31B and the differential amplifier circuit 51. Each of the photodetectors 31A and 31B is constituted by a photodiode, and these photodiodes are connected in series. The differential amplifier circuit 51 includes an operational amplifier 51A having a feedback resistor R. The difference between the current I ₂ flowing in the current I ₁ and the photodiode 31B that flows through the photodiode 31A is calculated at their nodal, this difference current is input to the operational amplifier 51A. The operational amplifier 51A are converts the differential current input to the voltage signal V _0. This output voltage V ₀ is given by the following equation.

V ₀ = R (I ₂ −I ₁ ) Equation (2) The output voltage V ₀ of the differential amplifier circuit 51 is a tracking band pass filter (tracking BPF (C)) 52 and a tracking low pass filter. (Tracking LP
F (L)) 55.

Output signal of tracking BPF52 is frequency / voltage (F / V)
It is provided to the conversion circuit 53. The output signal of the F / V conversion circuit 53 is the speed (ground speed) of the vehicle equipped with the road surface identification device.
V, the output signal of the F / V conversion circuit 53 is the tracking BP
Feedback frequency to F52 and tracking LPF55, cutoff frequency (frequency band) in these filter circuits
Is used to follow the vehicle speed v and change the audience.

The output signal of the tracking BPF 52 is
To enter. The amplitude detection circuit 54 outputs a signal representing the center frequency component intensity Da described above.

The output signal of the tracking LPF 55 is input to the amplitude detection circuit 56. The amplitude detection circuit 56 has the low frequency component intensity Db described above.
Is output.

An example of the configuration of the tracking BPF 52 is shown in FIG. The tracking BPF52 is a high-pass filter (HPF)
And low pass filter (LPF).
And the LPF are connected in series via a buffer amplifier 75. The HPF includes a capacitor 71 and a voltage control variable resistance element 73. The LPF includes a capacitor 72 and a voltage control variable resistance element 74. The voltage control variable resistance elements 73 and 74 are constituted by, for example, FETs. These elements 73 and 74 are supplied with a control voltage from a control voltage generating circuit 76, and the resistance values of the elements 73 and 74 change according to the control voltage. HPF by changing the resistance value of elements 73 and 74
And the cutoff frequency of the LPF changes. The pass band of the tracking BPF 52 is a band between the cut-off frequency of the HPF and the cut-off frequency of the LPF (higher than the cut-off frequency of the HPF). The control voltage generation circuit 76 generates a control voltage according to the output voltage signal (representing the vehicle speed v) of the F / V conversion circuit 53.

For example, assuming that the period of the road surface (the unevenness of the road surface) selected by the spatial filter in the optical system described above is 5 (mm), the space stop frequency μ is 0.2 (mm ⁻¹ ). The speed (ground speed) of the vehicle is assumed to be v (Km / h).

v (Km / h) = 1000 v / 3.6 (mm / s) Equation (3) From equation (1), the center frequency f of the electric signal obtained from the differential amplifier circuit 51 is f = μ × v = 200 v / 3.6 (Hz)) Equation (4) is obtained.

Therefore, the center frequency of the pass band of the tracking BPF 52 may be set to the frequency represented by the equation (4), and may be changed according to the vehicle speed v according to the equation (4).

Tracking LPF55 is LPF in tracking BPF52
It has the same configuration as that of the capacitor 72, the voltage control variable resistance element 74, and the control voltage generation circuit 76 (the cutoff frequency is different), and the cutoff frequency changes according to the vehicle speed v.

When setting the frequency of the low frequency component to be extracted by this tracking LPF 55 to be 1/10 of the center frequency,
Referring to equation (4), the cut-off frequency is
It may be set to 20v to 3.6 (Hz).

A specific configuration example of the amplitude detection circuit 54 is shown in FIG. This circuit 54 includes a half-wave rectifier circuit 77 and a low-pass filter (LPF) 78. Half-wave rectifier circuit 77
Alternatively, a full-wave rectifier circuit can be used. The pass band of the LPF 78 is determined from the viewpoint of the response time required for detecting the road surface. For example, if the response time is 0.1 (S) and the LPF 78 is a first-order low-pass filter, the cutoff frequency is 3.7 (Hz).

The output signal of the photodetector 31B (or the photodetector 31A) passes through a low-pass filter (LPF) 57, and the diffuse reflection light amount Dc
LPF 57 is output as a signal indicating
The purpose of this is to remove the extremely low frequency fluctuations contained in the output signal, and its cutoff frequency is, for example, 1 (Hz) (fixed)
Set to about.

The output signal of the regular reflection light photodetector 32 is a signal representing the regular reflection light amount Dd. A low pass filter having an appropriate pass band may be connected to the output side of the photodetector 32.

The output signal of the road surface thermometer 33 is a signal representing the road surface temperature De. A thermometer (temperature sensing element) that detects the outside air temperature instead of the road surface may be used. In this case, the thermometer is provided at a place where it comes into contact with the outside air.

The light source 11 for road illumination and the light source 12 for specular reflection light are controlled by automatic power control (APC) circuits 61 and 62, respectively. Thus, the amount of light projected from these light sources 11 and 12 is always kept constant.

Center frequency component intensity Da output from amplitude detection circuit 54
A signal indicating the low-frequency component intensity Db output from the amplitude detection circuit 56, a signal indicating the diffuse reflection light amount Dc output from the LPF 57, a signal indicating the regular reflection light amount Dd output from the photodetector 32, The signal indicating the road surface temperature De output from the road surface thermometer 33 is input to the determination circuit 60.

The discrimination circuit 60 uses two or more of these input signals to discriminate or discriminate a road surface state according to a road surface discrimination algorithm described later. The discriminating circuit 60 is preferably a CPU
(For example, a microcomputer), a memory, and other peripheral circuits. In this case, the above-described signals Da to De are converted to digital data by an A / D conversion circuit and then supplied to a discrimination circuit 60.

(4) Road surface determination algorithm (No. 1) FIG. 12 shows the simplest road surface determination algorithm. The processing according to the road surface determination algorithm is executed in the determination circuit 60. This is the same for other road surface identification algorithms.

Ratio Db between low frequency component intensity Db and center frequency component intensity Da
/ Da is calculated, and this ratio is determined by the thresholds TH1 and TH
Compared to 2. If the ratio TDb / Da is greater than the threshold value TH1 (called "large"), if it is between the threshold values TH1 and TH2, it is a gravel road (called "medium"), if it is less than the threshold value TH2 It is determined as an asphalt road (called "small").

Only the threshold value TH1 may be set in the discriminating circuit 60, and only discrimination between snow and gravel may be performed.

Only the threshold value TH2 (or an appropriate value between TH1 and TH2) may be set in the discriminating circuit 60, and only discrimination between snow and asphalt may be performed.

Only the threshold value TH2 may be set in the discriminating circuit 60, and only the discrimination between gravel and asphalt may be performed.

(5) Algorithm for discriminating the road surface (No. 2) FIG. 13 discriminates whether the asphalt road is in a wet state or a dry state by further using a signal representing the regular reflection light amount Dd given from the photodetector 32. 1 shows a road surface determination algorithm to be performed.

If the ratio Db / Da is equal to or less than the threshold value TH2, the road is an asphalt road.

When the surface (road surface) of the asphalt road is wet (wet), the road surface is in a state close to a mirror surface, and the regular reflection light amount Dd is greater than in a dry state. The threshold value is set at a level substantially intermediate between the regular reflection light amount obtained when the asphalt road is in a wet state and the regular reflection light amount obtained when the asphalt road is in a dry state. If the regular reflection light amount Dd is greater than or equal to this threshold value ("large"), it is determined to be wet asphalt,
If it is less than the threshold value ("small"), it is determined to be dry asphalt.

The determination of the gravel road and the snowy road is the same as that by the algorithm shown in FIG.

It is needless to say that only the determination of the wet asphalt road and the dry asphalt road may be performed, the determination of the gravel road may be added thereto, and the determination of the snowy road may be added thereto.

(6) Road Surface Determination Algorithm (Part 3) FIG. 14 shows the road surface condition further utilizing the signal representing the diffused light amount Dc output from the LPF 57 and the signal representing the road surface temperature De output from the road surface thermometer 33. The determination is made in more detail.

Generally, moisture freezes at 0 (° C). Therefore, if the road surface temperature De is 0 (° C.) or less, there is a possibility of freezing. It is determined whether the road surface temperature De is higher than the freezing temperature ("high") or lower than the freezing temperature ("low").

The freezing temperature does not need to be exactly 0 (° C.), but may be determined empirically to an optimum value. When the air temperature is used in place of the road surface temperature, the temperature at which the frozen road surface can remain without melting, the temperature at which the road surface starts to freeze, and the like will be the thresholds for determination.

Since the frozen road surface is close to the mirror surface like the wet road surface, the regular reflection light amount Dd is “large”.

Therefore, the road surface temperature De is “low” and the amount of specular reflection is
If Dd is "large", it is determined that the road is frozen. In this case, the diffuse reflection light amount Dc (which will be described in detail later) is generally “small”.

Even if the road surface temperature De is "low", the regular reflection light amount Dd is "small"
If so, it is not a frozen road. In this case, the road surface condition is determined based on the ratio between the low frequency component intensity Db and the center frequency component intensity Da (dry asphalt road or gravel road). The reason why snow is excluded in this determination is that snow is determined based on the diffuse reflection light amount Dc. However, the ratio is based on Db / Da for snow determination and diffuse reflection
Because the snow condition is slightly different in some cases (there may be the same condition), the snow may be judged based on the ratio Db / Da.

Fresh snow or snow that remains white even when stepped on by a passing object (vehicle, person) diffuses and reflects light. Since the amount of diffuse reflection by snow is extremely large compared to other road conditions,
Snow and other road surface conditions can be determined based on the diffuse reflection light amount Dc. For this determination, the threshold value is set to a level between the amount of diffuse reflection in snow and the amount of diffuse reflection in other road surface conditions.

If the road surface temperature De is “low” and the diffuse reflection light amount Dc is equal to or greater than the threshold value (“high”), it is determined that the snow is present. It goes without saying that the threshold value of the road surface temperature when it is determined to be frozen may be different from the threshold value of the road surface temperature when it is determined to be snow.

The snow determined based on the diffuse reflection light amount Dc is snow having a white surface partially or entirely. On the other hand, the ratio
The snow determined on the basis of Db / Da changes the amount of diffuse reflection at a longer cycle than gravel, and includes not only white snow but also snow that has been crushed and turned black.

The judgment algorithm when the road surface temperature De is "high" is 13th.
It is the same as that shown in the figure.

Only a portion of the determination algorithm shown in FIG. 14 can be used to identify or determine only one or more types of road conditions of frozen, snow, gravel, dry asphalt and wet asphalt. Needless to say.

(7) Road Surface Determination Algorithm (Part 4) The road surface determination algorithm shown in FIG. 15 is similar to the one shown in FIG. Figure 15 distinguishes between gravel and asphalt based on the ratio Db / Da. The point that snow is not determined based on this ratio Db / Da is different from that shown in FIG. No.
The algorithm in FIG. 15 can be considered as a variation of the algorithm in FIG.

(8) Electric Configuration of Road Surface Discriminating Device (Part 2) FIG. 16 is a light detector for projecting light amount monitoring which is provided near the power supply 12 for regular reflection light and detects the amount of light emitted from the light source 12. 34 shows an example of a signal processing circuit using an output signal of an optical system (see the optical system of FIG. 1).

The specular reflection light amount Dd represented by the output signal of the specular reflection detector 32
Is divided (divided) by the value represented by the output signal of the photodetector 34 in the arithmetic circuit 58. This division result Ddd is
It is provided to the discrimination circuit 60 instead of the regular reflection light amount Dd. In the above-described road surface determination algorithm, Ddd is used instead of Dd.

In this way, the projection light of the light source 12 fluctuates (temperature change,
(Due to changes over time, etc.), the variation is corrected by the output of the photodetector 34, so that accurate road surface discrimination can be performed.

In FIG. 16, the light source for regular reflection light 12 is not controlled by the APC circuit, but may be controlled by the APC circuit.

The light amount of the projection light from the road surface illumination light source 11 may be similarly detected, and the output signal (representing the diffuse reflection light amount Dc) of the LPF 57 may be corrected based on the detected light amount.

The operation circuit 58 may be not only a division circuit but also a subtraction circuit.

The other configuration of the processing circuit (a part not shown) is the same as that shown in FIG.

(9) Electrical Configuration of Road Surface Discrimination Device (Part 3) FIG. 17 shows another configuration example of a signal processing circuit devised so as to remove the influence of disturbance light. 1 to 3
It is applied to the optical system shown in the figure.

The pulse oscillating circuit 63 generates a pulse signal of a constant frequency (described later) and supplies the pulse signal to the APC circuit 61A and the dual comb filter 64. The APC circuit 61A drives the road surface illumination light source 11 in synchronization with the applied pulse signal. Therefore.
The light source 11 emits pulsed projection light toward the road surface at a constant cycle.

The light detectors 31A and 31B receive the pulsed diffused reflected light,
The output signal of the differential amplifier circuit 51 is also a pulse signal. This signal can be considered to be a so-called pulse-modulated diffuse reflected light. An example of the output signal of the differential amplifier circuit 51 is shown in FIG.

The output signal of the differential amplifier circuit 51 has a waveform in which a pulse-like signal (its peak value represents the amount of diffusely reflected light) synchronized with the oscillation pulse of the pulse oscillation circuit 63 is superimposed on disturbance light. The dual comb filter 64 removes disturbance light and smoothes a pulse signal.

FIG. 20 is an enlarged view of one pulse shown in FIG. The signal level is sampled and held at a timing SH1 immediately before the rising edge of the pulse signal, at a timing SH3 immediately after the falling edge, and at an intermediate time point SH2 between the rising edge and the falling edge. These sampled and held levels are V1, V3, and V2, respectively. Using these levels, the level of one pulse is calculated according to the following equation, and this level is held until the next pulse. In this way, the influence of disturbance light is removed.

2V2− (V1 + V3) Equation (5) The dual-comb filter 64 performs the above-described sample hold, operation, and output hold, and a specific configuration example is shown in FIG.

The pulse signal generated from the pulse oscillation circuit 63 is supplied to the timing generation circuit 87 as a synchronization signal. The timing generation circuit 87 generates timing signals indicating the above-mentioned timings SH1, SH2, SH3, and performs sample and hold (S / H)
It is given to circuits 81, 82 and 83. The output signal of the differential amplifier circuit 51 is S /
The signals are input to the H circuits 81, 82, and 83, and are sampled and held at the respective timings.

The outputs V1 and V3 of the S / H circuits 81 and 83 are added by an adding circuit 84,
The output V2 of the H circuit 82 is doubled by the doubling circuit 85. Subtraction circuit 8
At 6, the output of the adder 84 is subtracted from the output of the doubling circuit 85, and the result of this subtraction is output as an output signal. This output signal is held until the calculation for the next pulse is completed. The output signal of dual comb filter 64 is provided to tracking BPF 52 and tracking LPF 55.

The timing generation circuit 87 may be provided in the pulse oscillation circuit 63, and a timing signal for sample and hold may be supplied from the pulse oscillation circuit 63 to the dual comb filter 64.

In the above operation, the delay time and the light propagation time in the light source 11 and the photodetectors 31A and 31B can be ignored. The sample / hold timing is not limited to the above example. It is sufficient that the sample and hold are performed at least at two points, that is, the peak point of the pulse and the point before or after the pulse rises.

The frequency f _P of the pulse signal generated by the pulse oscillation circuit 63 is equal to the input signal (differential amplification circuit 51) of the dual comb filter 64.
Output signal) must be at least twice the maximum frequency. That is, f _P ≧ 2 · μ · v _max Equation (6) For example, μ = 0.2 (mm ⁻¹ ) (center spatial frequency), v _max
Assuming that = 100 (Km / h) = 2.78 × 10 ⁴ (mm / s) (maximum ground speed), f _P ≥ 11.1 (KHz).

The other configuration in FIG. 17 is the same as that shown in FIG.

(10) Electric Configuration of Road Surface Discrimination Device (Part 4) FIG. 21 shows still another example of the signal processing circuit. Compared with the signal processing circuit shown in FIG. 17, a sine wave oscillation circuit 65 is used instead of the pulse oscillation circuit 63, and the APC circuit
The projected light amount of the light source 11 is sinusoidally modulated by 61B. A heterodyne demodulation (detection) circuit 66 is used in place of the dual-comb filter 64, and the output signal of the differential amplifier circuit 51 is demodulated, and the tracking BPF 52 and the tracking LPF 55
Given to. This configuration also removes disturbance light and reduces S / N
The ratio can be improved. Other configurations are shown in Figs.
It is the same as that shown in the figure.

(11) Electrical Configuration of Road Surface Discrimination Device (Part 5) FIG. 22 shows still another configuration example of the signal processing circuit.

Both the road illumination light source 11 and the regular reflection light source 12 are pulse-driven. The pulse oscillation circuit 63A has two different phases.
A type of drive pulse 1 and drive pulse 2 are generated. Based on these drive pulses 1 and 2, the APC circuits 61A and 62A drive the light sources 11 and 12 at different timings, respectively.

In addition to the dual-comb filter 64 connected downstream of the differential amplifier circuit 51, a dual-comb filter 67 is also provided downstream of the specular reflection light detector 32. The output signal of the dual Ko filter 67 is given to the discrimination circuit 60 as a signal representing the regular reflection light amount Dd.

These dual-comb filters 64 and 67 receive synchronization signals synchronized with drive pulses 1 and 2 from pulse oscillation circuit 63A, respectively.

With the above configuration, even if the wavelengths of the projection lights of the light sources 11 and 12 have the same or similar values, the diffuse reflection light and the regular reflection light can be separated from each other and detected reliably. Also, the influence of disturbance light can be eliminated.

(12) Optical Configuration (No. 2) and Electrical Configuration (No. 6) of Road Surface Discrimination Device FIGS. 13 and 24 show another example of the optical configuration of the road surface determination device. The same components as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted. The slit plate is denoted by reference numeral 22A, the optical filter is denoted by reference numeral 23A, and the collimating lens is denoted by reference numeral 24A. In FIG. 24, the light sources 11, 12 and the photodetector 32 are not shown.

FIG. 25 shows an electrical configuration (signal processing circuit) suitable for the optical configuration shown in FIGS. 23 and 24. Also in this figure, the same components as those shown in FIG. 8 are denoted by the same reference numerals, and redundant description will be avoided.

The central frequency component intensity Da is obtained based on the differential signal of the output signals of the photodetectors 31A and 31B, as in the configuration shown in FIG. A light receiving optical system including the photodetectors 31A and 31B (including the grating plate 25, the prism array 26, the condenser lens 27, and the mirror 28) is defined as a first light receiving optical system.

Another second light receiving optical system is provided to obtain signals representing the low frequency component intensity Db and the diffuse reflected light amount Dc, respectively. The second light receiving optical system includes a grating plate 4
5. It is composed of a condenser lens 47, a photodetector 41 and a mirror 48.

The road illumination light source 11, the light receiving lens 21, the slit plate 22A, the optical filter 23A, and the collimating lens 24A are first and second.
Are common to the light receiving optical systems.

Therefore, the diffuse reflected light from the road surface LD enters not only the first light receiving optical system but also the second light receiving optical system, and the light detector
Received by 41. The light receiving signal of the photodetector 41 is amplified by the amplifier circuit 42, and then applied to the tracking LPFs 55 and 57. A signal representing the low frequency component intensity Db is obtained based on the output signal of the tracking LPF 55, and a signal representing the diffuse reflection light amount Dc is obtained from the LPF 57.

By taking the difference between the output signals of the two photodetectors 31A and 31B, the center frequency component is amplified about twice as described above. However, low frequency components may be slightly offset by taking the difference. To ensure higher levels of low frequency components, another photodetector 41
Is provided.

If necessary, the second light receiving optical system may be provided with a spatial filter having a center spatial frequency corresponding to a low frequency component to be extracted. At this time, it is preferable that two photodetectors are provided in the second light receiving optical system, and output signals of these photodetectors are supplied to a differential amplifier circuit.

All the above-described ones are used for the road surface determination algorithm. In addition, FIG. 16, FIG. 17, FIG.
The concept of the modification shown in FIG. 22 can also be applied to the circuit in FIG.

(13) The optical configuration (part 3) and the electrical configuration (part 7) of the road surface determination device and the road surface determination algorithm (the
5, 6 and 7) FIG. 26 shows still another example of the optical configuration of the road surface identification device. This optical configuration is basically the same as that shown in FIG. 1 and FIG. The differences are as follows.

The regular reflection light source 12, the regular reflection light detector 32, and the projection light amount monitor 34 shown in FIGS. 1 and 2 (and FIG. 3) are omitted. Instead, a light source 17 for specular reflection light is provided.

Of the light projected from the regular reflection light source 17 to the road surface LD, the regular reflection light from the road surface LD is converted into the light receiving lens 21 and the slit plate 2.
2, Arranged so that it passes through the optical filter 23, collimating lens 24, grating plate (slit array) 25, prism array 26, and condenser lens 27 and enters the photodetectors 31A and 31B for specular reflection light. A light source 17 is provided. Since the amount of specularly reflected light is large when the road surface is wet or frozen,
The light source 17 does not need to be as large as the light source 11 (the number of light emitting diodes constituting the light source is at least good).

FIG. 27 shows a signal processing circuit suitable for the optical system shown in FIG. This circuit is similar to the configuration shown in FIG. 22 in that the light source is driven by two types of pulses having different timings and the received light signal is separated by a dual-comb filter. No.
The same components as those shown in FIG. 22 are denoted by the same reference numerals to avoid repeated description, and only different points will be described.

On the basis of the two types of driving pulses 1 and 2 having different timings, the APC circuits 61A and 62A alternately pulse drive the light source 11 for road surface illumination and the light source 17 for regular reflection light.

Diffuse reflected light and specular reflected light from the road surface LD are detected by the photodetectors 31A and 31.
B, and both detectors 3
The differential output of the output signals of 1A and 31B is obtained. Differential amplifier circuit
The output signal of 51 is supplied to two dual-comb filters 64 and 67.

The dual-comb filter 64 operates in synchronization with a pulse for driving the light source 11, and extracts a signal based on diffuse reflection light. Based on the output signal of the dual-comb filter 64, signals representing the center frequency component intensity (diffuse reflected light) Da and the low frequency component intensity (diffuse reflected light) Db are obtained.

The dual-comb filter 67 operates in synchronization with a pulse for driving the light source 17, and extracts a signal based on specularly reflected light.
The output signal of the filter 67 is provided to the tracking BFP 68. The tracking BPF 68 is the same as the tracking BFP 52, and a voltage signal representing the velocity v is fed back. The output signal of the tracking BPF 68 is provided to the amplitude detection circuit 69. From the amplitude detection circuit 69, a signal representing the center frequency component intensity (specular reflection light) Df is obtained and supplied to the discrimination circuit 60.

By modulating the light sources 11 and 17 with signals of different frequencies, and demodulating the output of the differential amplifier 51 at the modulation frequency, it is also possible to separate the signal into a signal based on diffuse reflection light and a signal based on regular reflection light.

FIG. 28, FIG. 29 and FIG. 30 show the road surface discrimination algorithm (part 5), (part 6) and (part 7), respectively. These are basically the same as those shown in FIG. 13, FIG. 14 and FIG. The difference is the following point.

That is, the regular reflection light amount Dd used in the algorithm shown in FIGS. 13 to 15 is the center frequency component intensity (specular reflection light) Df and the center frequency component intensity (diffuse reflection light).
The ratio with Da is replaced by Df / Da. In a frozen or wet state, the amount of specular reflection increases, so this ratio Df / Da
Increase. Therefore, a frozen or wet state can be determined by discriminating the ratio Df / Da with an appropriate threshold value.

(14) Electrical configuration of road surface identification device (No. 8, No. 9, No. 1)
FIG. 31 shows an example (part 8) of a simplified processing circuit in a road surface identification device. Here, an example will be described in which the road surface condition is distinguished between snow and gravel. The same components as those already described are denoted by the same reference numerals, and redundant description will be avoided.

The output signal of the tracking BPF 52 contains a center frequency component. This output signal is binarized by the binarization circuit 81 as its zero-level threshold level, and input to a counter 82 (referred to as a counter A).

On the other hand, the output signal of the differential amplifier circuit 51 includes not only the center frequency component but also a low frequency component. As described with reference to FIG. 7, the level of the low-frequency component changes according to the road surface condition, and increases in the order of snow, gravel, and asphalt.
This signal is binarized by a binarization circuit 83 using the zero level as a threshold level, and a counter 84 (referred to as a counter B).
To enter.

FIG. 32 shows the output of the differential amplifier circuit 51, the output of the binarization circuit 33, the output of the tracking BPF 52, and the binarization circuit 81 only when the road is snowy and in FIG. 33 only when the road is gravel. The waveform of the output of FIG.

Since the output signal of the tracking BPF 52 is mainly composed of the center frequency component, regardless of the road surface condition,
The counter A counts an almost constant value (constant speed) during a certain period of time.

On the other hand, the output signal of the differential amplifier circuit 51 contains a low frequency component in addition to the center frequency component. When the road surface is snowy, the amplitude of the low frequency component is large, so that the center frequency component is superimposed on the low frequency component. Therefore, the number of pulses formed when this signal is binarized is small, and the count value of the counter B during a certain time is small.

When the road surface is gravel, the amplitude of the low-frequency component is small. Therefore, when the output signal of the differential amplifier circuit 51 is binarized at zero level, the number of pulses formed when the center frequency component is binarized. Approach the number of pulses obtained. The count value of the counter B for a certain period of time is a value close to the count value of the counter A.

Therefore, it is possible to determine whether the road surface condition is snow or gravel by comparing the count values of the counters A and B at a certain time (for example, taking a ratio).

The timing circuit 86 resets the counters A and B at regular intervals and starts counting input pulses. Discrimination circuit 85
Reads the count values of the counters A and B immediately before the counters A and B are reset, and determines the road surface condition based on the ratio of the count values.

According to this concept, the distinction between snow and asphalt,
Can distinguish between asphalt and gravel, and distinguish between snow, asphalt and gravel.

As described above, it is needless to say that wetting, freezing, snow, and the like can be determined by considering the amount of specular reflection, the amount of diffuse reflection, the road surface temperature, and the like.

FIG. 34 shows still another example (No. 9) of the signal processing circuit. In the example shown in FIG. 31, the road surface is determined using the ratio of the count values of the two counters A and B in a certain time. . number 3
In the circuit shown in FIG. 4, a discrimination output is obtained every time the vehicle travels a certain distance.

That is, when the count value of the counter A reaches a predetermined value, the count value of the counter B is
Read to 85. The determination circuit 85 determines the road surface condition based on the count value of the counter B. The determination circuit 85 can omit the calculation of the ratio between the count values of the counters A and B.

When the count value of the counter A reaches a predetermined value, the counters A and B are reset and start counting again.

For example, the center spatial frequency of the road surface selected by the spatial filter is set to 0.25 (mm ^-1 ) (the period is 4 (mm)).
The predetermined value set in the counter A is 250. In this case, each time the vehicle advances 4 (mm) × 250 = 1 (m), one road surface determination is performed.

In the processing circuit shown in FIG.
Since the road surface condition is determined based on the count values of A and B, when the running speed of the vehicle is low, the count values of the counters A and B may be small and the determination accuracy may not be sufficient. No.
In the processing circuit shown in FIG. 34, road surface discrimination is performed for each constant traveling distance of the vehicle, so that the response time becomes longer when the traveling speed is slow.

The signal processing circuit (No. 10) shown in FIG. 35 is an improvement of the processing circuit shown in FIG.
A1 and B1, A2 and B2, A3 and B3, and A4 and B4). As shown in FIG. 36, under the control of the timing control circuit 86A, each set of counters A and B is reset / started at short intervals. For example, each set of counters A,
Assuming that the counting time of B is 0.8 seconds, the counting operation of each set of counters A and B starts every 0.2 seconds. Multiplexers 87 and 88
The set of counters is switched every 0.2 seconds and the count value is given to the discriminating circuit 85. As a result, the road surface determination cycle is 0.2 seconds. Even if the road surface determination cycle is short, the counting time of each set of counters is long (0.8 seconds), so that the determination accuracy does not decrease.

The signal processing circuit (No. 11) shown in FIG. 37 is an improvement of the processing circuit shown in FIG.

According to the count value of the counter A1, counting of each set of the counters A and B starts. For example, the count value set in the counter A is 256. When the count value of the counter A1 is 0, the counters A1 and B1 start counting. Counter A1 counts
At 64, 128 and 192, the counters A2 and B2 and the counter A3
B3 and counters A4 and B4 each start counting.

When the count value of counter A1 reaches 256, counter B1
Is supplied to the half circuit 85 through the multiplexer 88. Similarly, when the count values of the counters A2, A3, and A4 reach 256, respectively, the count values of the counters B2, B3, and B4 are input to the determination circuit 85 via the multiplexer 88.

Even if the set count value of the counter A is the same, the road surface discrimination cycle becomes 1 / counter number of counters and the response speed becomes faster than the circuit of FIG.

FIG. 38 shows an example (part 12) in which the amplification factors of the differential amplifier circuit and other amplifier circuits included in the signal processing circuit are controlled according to the road surface determination result.

For example, when the road surface is snowy, the amount of diffusely reflected light increases, so that the light receiving circuit may be saturated. In order to prevent such a situation, the gain of the amplifier circuit is reduced when it is determined that snow has occurred.

The differential amplifier circuit 51 includes a circuit (for example, a feedback resistor) 91 that determines an effective amplification type in a road surface state other than snow and a circuit 92 that provides a lower amplification factor used in snow. -They are connected via switches 93 and 94, respectively. The gain control circuit 96 controls the analog switch 94 to be turned on in the case of snow and the analog switch 93 to be turned on otherwise in accordance with the road surface discrimination result of the discrimination circuit 85. Reference numeral 95 denotes an inverter. Thus, saturation of the light receiving circuit can be prevented.

Gain control based on road surface reflectance
In the case of a painted (painted) road surface (high reflectivity), the gain will decrease. Although the painted road surface has a high reflectance, the output amplitude of the photodetector of the spatial filter does not become so large. According to the circuit of FIG. 38, the gain is not erroneously reduced even on such a road surface.

On a snowy road, instead of lowering the gain of the amplifier circuit,
The light projection amount of the light source 11 and the like may be reduced.

(15) Application Example of Road Surface Discriminating Apparatus FIG. 39 shows an example of an apparatus for giving a necessary warning to a driver according to a result of the road surface discriminating.

Road surface discriminating device 10 having the above-described configuration mounted on a vehicle
When sand or gravel, or snow or freezing is detected by 0, the vehicle is equipped with an alarm device 102 that notifies the driver that the possibility of slip is high. The road surface discrimination result of the road surface discrimination device 100 is given to an ECU (Electronic Control Unit) 101 for an ABS (anti-lock brake system). When the ECU 101 determines that there is a high possibility of slipping (such as the above-mentioned snow and freezing), the ECU 101 outputs a signal to the alarm device 102 to notify the driver of the signal. This alarm may be realized by audio output, screen display, or indicator lamp lighting.

FIG. 40 shows a configuration of an ABS provided with a road surface discriminating device that outputs a speed and a road surface discrimination result.

The output of the road surface determination device 100 (the ground speed v and the road surface determination result) and the output of the wheel rotation speed sensor 103 (wheel speed v _W )
Provided to the ECU 101.

The wheel rotation speed sensor 103 is mounted on a tire of an automobile, and includes a rotor 104 having a number of magnetic pole teeth around the rotor 104 and an electromagnetic pickup type sensor 105 for outputting a pulse signal having a frequency proportional to the rotation speed of the rotor 104. ing. The frequency of the pulse output from the sensor 105 represents the wheel speed v _W.

ECU101 is according to the following equation from the ground speed v and wheel speed v _W to enter, to calculate a slip ratio lambda.

λ = (v−v _W ) / v Equation (7) The ECU 101 also has a table storing the optimum slip ratio λ _m according to the road surface condition as shown in FIG.
This table is created by preliminary experiments.

ECU101 outputs a braking pressure control signal to read out the optimum slip ratio lambda _m corresponding to the road surface judgment result from the table, the calculated slip ratio lambda and the optimum slip ratio lambda _m matches. This brake control is preferably performed by feedback control.

FIG. 42 shows an automobile equipped with the above-mentioned ABS. By performing the above-described processing based on the output signal of the road surface identification device 100 having a ground speed detection function and the output signal of the wheel rotation speed sensor 103, the ABS can minimize the moving distance on each road surface without locking the tires. Is constructed.

Also, by storing the road surface determination result immediately before the vehicle stops, the traction control system controls the accelerator to prevent tire slip when starting.
A system (TCL) can be built. In TCL, a table storing the optimum engine speed for each type of road surface is created in advance. The ECU 101 refers to this table according to the road surface determination result stored immediately before the vehicle stops, and controls the accelerator so that the optimum engine speed according to the road surface condition is obtained.

The ECU 101 determines whether the vehicle has started normally based on the ground speed. ECU101 if tires are slipping
Controls to reduce the engine speed.

FIG. 43 shows a suspension control device provided with a road surface identification device, and FIG. 44 shows a cross-sectional view of a shock absorber which is a main part of suspension control.

The road surface determination result from the road surface determination device 100 and the ground speed v are E
Provided to CU101. The control signal from the ECU 101
Absorber 106 is given.

Regardless of the road surface condition, it is necessary to control the so-called "hardness" of the suspension according to the road surface condition in order to ensure the maneuverability, stability, and riding comfort of the vehicle. For example, it is better to make the suspension softer for gravel roads and sandy roads with large undulation, and to make the suspension harder for asphalt or concrete roads.

Such a function can be used in response to a shock
This is realized by controlling the opening of the electromagnetic valve in the absorber as described below.

Referring to FIG. 44, piston 115 fixed to the chassis of the vehicle moves up and down in cylinder 111 fixed to the frame of the vehicle with the vibration of the chassis. When the piston 115 moves, the liquid (oil) filled in the liquid chambers 112A and 112B passes through the passage of the electromagnetic valve 116 and the liquid chambers 112A and 11B.
Move between 2B. The electromagnetic valve 116 is driven and controlled by a control signal from the ECU 101. As a result, the electromagnetic valve 116
Since the area of the liquid passage at the time changes, it becomes possible to control the vibration damping force.

When the road surface determination device 100 determines that the road surface is gravel or sand, the electromagnetic valve 116 is widely opened to soften the suspension, and when the road surface is determined to be asphalt or concrete, the electromagnetic valve 116 is opened small to harden the suspension. .

The free piston 114 and the gas chamber 113 are liquid chambers 112A and 112.
This is to absorb the difference in volume change of B. For controlling the opening and closing of the electromagnetic valve 116, not only the road surface discrimination result but also the speed v may be used. For example, when the vehicle is traveling at high speed, even if the road surface is slightly uneven, the impact received is large, so that the suspension may be controlled to be soft.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Sakai 10 Okado Dodocho, Ukyo-ku, Kyoto-shi, Kyoto Omron Corporation (56) References JP-A-59-196402 (JP, A) JP-A-59 JP-A-126230 (JP, A) JP-A-61-283871 (JP, A) JP-A-5-52857 (JP, A) JP-A-5-52858 (JP, A) JP-A-1-168347 (JP, U) )

Claims (44)

(57) [Claims] A first light source for irradiating light toward a road surface; a first spatial filter means; and a first light receiving means, and the light reflected by the first light source from the road surface is reflected by the first light source. A first spatial filter light receiving optical system that receives light by the first light receiving means through the first spatial filter means and outputs an electrical signal representing the received reflected light; and a second light receiving means. A second light receiving optical system for receiving the reflected light of the projection light from the road surface by the second light receiving means, and outputting an electric signal representing the received reflected light; and outputting the electric signal from the first spatial filter light receiving optical system. A first signal processing circuit for detecting the intensity of a center frequency component corresponding to the spatial frequency of the first spatial filter means from the electric signal; the first signal processing circuit detecting the electric signal output from the second light receiving optical system; Of the spatial filter means A second signal processing circuit for detecting the intensity of a low frequency component corresponding to a spatial frequency lower than the wave number; and a center frequency component intensity detected by the first signal processing circuit and detected by the second signal processing circuit. A determination unit configured to determine a road surface state based on the obtained low-frequency component intensity. 2. The optical receiving system according to claim 1, wherein said second light receiving optical system is included in said first spatial filter light receiving optical system, said second light receiving means is said first light receiving means, and an output from said first light receiving means is provided. The electric signal to be transmitted is the first
The road surface determination device according to claim 1, which is provided to a signal processing circuit and a second signal processing circuit. 3. A part of said second light receiving optical system is included in said first spatial filter light receiving optical system, and said second light receiving means receives reflected light which does not pass through said first spatial filter means. The road surface identification device according to claim 1, wherein the road surface identification device performs the operation. 4. The second light receiving optical system includes a second spatial filter having a spatial frequency lower than a spatial frequency of the first spatial filter means, and the second light receiving means includes a second spatial filter. The road surface determining device according to claim 1, wherein the device receives reflected light through a filter. 5. The road surface determination according to claim 1, wherein the road surface state determined by the determination means is at least one of snow, gravel, and asphalt. apparatus. 6. The first light source, the first spatial filter light receiving optical system, and the second light receiving optical system,
The road surface discriminating apparatus according to any one of claims 1 to 4, wherein said light receiving means is arranged to receive diffusely reflected light from the road surface. 7. A third light receiving optical system including a second light source for projecting light toward a road surface, and a third light receiving element, wherein the second light source and the third light receiving optical system include: The third light receiving element is arranged so as to receive regular reflection light of the projection light of the second light source from the road surface, and the discriminating means is provided on the road surface based on an output signal of the third light receiving element. The road surface determining device according to any one of claims 1 to 6, wherein the wet state is determined. 8. A light amount detector for detecting a light amount of the projection light of the second light source, wherein the determination means detects an output signal of the third light receiving element by a light amount detected by the light amount detector. The road surface determining apparatus according to claim 7, wherein the wet state of the road surface is determined based on a value obtained by normalization. 9. The method according to claim 7, wherein said third light receiving optical system is included in said first spatial filter light receiving optical system, and said third light receiving element is said first light receiving element. The road surface discriminating device according to the above. 10. An output signal of the first light receiving element is divided into a first signal component caused by light projected by the first light source and a second signal component caused by light projected by the second light source. A first signal processing circuit for detecting the intensity of a diffused light center frequency component from the first signal component separated by the separating device; and the second signal processing circuit separated by the separating device. A third signal processing circuit for detecting the intensity of the central frequency component of the specular reflected light from the signal component; The road surface determination device according to claim 9, which determines a wet state. 11. A driving circuit for driving the first light source and the second light source based on signals having different phases or signals having different frequencies, respectively, and a signal modulated by a signal having a different phase or a signal having a different frequency. 11. The road surface discriminating apparatus according to claim 10, further comprising: the separation unit, which is a demodulation circuit that demodulates the road surface. 12. A temperature sensor for measuring a road surface temperature or an air temperature, wherein said judging means judges that the temperature is lower than a predetermined value when the temperature detected by said temperature sensor is equal to or lower than a predetermined value. The road surface identification device according to item 7, wherein 13. A fourth detecting means for detecting an extremely low frequency diffuse light component from an output signal of said first light receiving element or said second light receiving element.
7. The signal processing circuit according to claim 1, further comprising a signal processing circuit, wherein the determining means determines that the snow is present when the diffused light component detected by the fourth signal processing circuit exceeds a predetermined value. Road surface identification device. 14. The first light source includes a plurality of light emitting elements, and a plurality of lenses disposed in front of the light emitting elements corresponding to the light emitting elements. The road surface determination device according to claim 1, wherein the road surface is deviated from an optical axis. 15. The first signal processing circuit includes a tracking band pass filter.
The road surface discriminating apparatus according to claim 1, wherein the band pass filter outputs a signal representing a ground speed, and a pass band is controlled based on the speed signal. 16. A road surface discriminating apparatus according to claim 15, wherein said second signal processing circuit includes a tracking low pass filter whose cutoff frequency is controlled based on said speed signal. 17. A driving circuit for driving the first light source based on a time-varying signal, and a demodulation circuit for demodulating output signals of the first and second light receiving means. The road surface determination device according to any one of the first to fourth ranges. 18. A drive circuit for driving the first light source and the second light source based on signals having different phases or signals having different frequencies, output signals of the first and second light receiving means, and The road surface identification device according to claim 7, further comprising: a demodulation circuit that demodulates an output signal of the third light receiving unit. 19. A light source for projecting light toward a road surface, a spatial filter light receiving optical system for receiving diffusely reflected light from the road surface of the light emitted from the light source through a spatial filter and outputting an electric signal representing the received reflected light. A first signal processing circuit for detecting an intensity of a center frequency component corresponding to a spatial frequency of the spatial filter from an electric signal output from the spatial filter light receiving optical system; A second signal processing circuit for detecting, from the signal, the intensity of a low frequency component corresponding to a spatial frequency lower than the spatial frequency of the spatial filter; and a center frequency component intensity detected by the first signal processing circuit and A road surface determining device that determines a road surface state based on the low-frequency component intensity detected by the second signal processing circuit. 20. The road surface determining apparatus according to claim 19, wherein the road surface state determined by said determining means is at least one of snow, gravel, and asphalt. 21. A second light source for projecting light toward a road surface,
And a second light receiving optical system including a second light receiving element,
The second light source and the second light receiving optical system are arranged such that the second light receiving element receives regular reflection light of the projection light of the second light source from the road surface, 21. The road surface discriminating device according to claim 19, wherein the device judges a wet state of the road surface based on an output signal of the second light receiving element. 22. A temperature sensor for measuring a road surface temperature or an air temperature, wherein said judging means judges as freezing when the temperature detected by said temperature sensor is lower than a predetermined value when judging as wet. 22. The road surface identification device according to item 21. 23. A light source for projecting light toward a road surface, a spatial filter light receiving optical system for receiving, through a spatial filter, diffusely reflected light of the projected light of the light source from the road surface and outputting an electric signal representing the received reflected light. A signal processing circuit for detecting a center frequency component corresponding to a spatial frequency of the spatial filter from an electric signal output from the spatial filter light receiving optical system; and a zero cross point of the central frequency component output from the signal processing circuit. First counter means for counting; second counter means for counting a zero-cross point of an electric signal output from the spatial filter light receiving optical system;
And a determining means for determining a road surface state based on the count value of the first counter means and the count value of the second counter means. 24. The road surface determining apparatus according to claim 23, wherein the road surface state determined by said determining means is at least one of snow, gravel, and asphalt. 25. The road surface discriminating apparatus according to claim 23, wherein said discriminating means makes a discrimination at predetermined time intervals, and said first and second counter means start counting operation. 26. Each time the count value of the first counter means reaches a predetermined number, the determination means makes a determination, and the first and second counter means start a counting operation. The road surface identification device according to paragraph 23. 27. A plurality of pairs of said first counter means and second counter means are provided, and the counting start time of said first and second counter means is different for each pair. 27. The road surface identification device according to any one of paragraphs 23 to 26. 28. A second light source for projecting light toward a road surface,
And a second light receiving optical system including a second light receiving element,
The second light source and the second light receiving optical system are arranged such that the second light receiving element receives regular reflection light of the projection light of the second light source from the road surface, 28. The road surface determining device according to claim 23, wherein the device determines a wet state of the road surface based on an output signal of the second light receiving element. 29. A temperature sensor for measuring a road surface temperature or an air temperature, wherein said judging means judges as freezing when the temperature detected by said temperature sensor is equal to or lower than a predetermined value when judging as wet. 29. The road surface identification device according to item 28. 30. An amplifier circuit for an electric signal including a light receiving signal, and means for controlling an amplification factor of the amplifier circuit in accordance with a result of the discrimination by the discriminating means. The road surface determination device according to any one of claims 1 to 4. 31. The projection light amount of the first or second light source is
30. The road surface discriminating apparatus according to claim 1, further comprising control means for changing the value in accordance with a result of the discrimination by said discriminating means. 32. A light source for projecting light toward the surface of an object, comprising: a first spatial filter means; and a first light receiving means, wherein reflected light of the light projected from the first light source from the object surface is provided. Is received by the first light receiving means through the first spatial filter means, and an electric signal representing the received reflected light is output.
A spatial filter light receiving optical system, and a second light receiving means, wherein the reflected light from the object surface of the projection light of the first light source is received by the second light receiving means,
A second light receiving optical system for outputting an electric signal representing the received reflected light, a center frequency corresponding to a spatial frequency of the first spatial filter means from an electric signal output from the first spatial filter light receiving optical system; A first signal processing circuit for detecting the intensity of the component; a second signal corresponding to a spatial frequency lower or higher than the spatial frequency of the first spatial filter means, based on the electric signal output from the second light receiving optical system. A second signal processing circuit for detecting the intensity of the frequency component, and a center frequency component intensity detected by the first signal processing circuit and a second frequency component intensity detected by the second signal processing circuit. An object discriminating device, comprising: discriminating means for discriminating an object surface state based on the following. 33. A light source for projecting light toward an object surface, a spatial filter light receiving means for receiving, through a spatial filter, diffusely reflected light of the light emitted from the light source from the object surface, and outputting an electric signal representing the received reflected light. An optical system, a first signal processing circuit for detecting an intensity of a center frequency component corresponding to a spatial frequency of the spatial filter from an electric signal output from the spatial filter light receiving optical system, and an output from the spatial filter light receiving optical system. A second frequency component for detecting the intensity of a second frequency component corresponding to a spatial frequency lower or higher than the spatial frequency of the spatial filter from the electrical signal.
And a discrimination for discriminating an object surface state based on the center frequency component strength detected by the first signal processing circuit and the second frequency component strength detected by the second signal processing circuit. means. The object discriminating device provided with. 34. A light source for projecting light toward an object surface, a spatial filter light receiving means for receiving, through a spatial filter, diffusely reflected light of the light emitted from the light source from the object surface, and outputting an electric signal representing the received reflected light. An optical system, a signal processing circuit for detecting a center frequency component corresponding to a spatial frequency of the spatial filter from an electric signal output from the spatial filter light receiving optical system, a zero-crossing of the center frequency component output from the signal processing circuit. First counter means for counting points; second counter means for counting zero-cross points of the electric signal output from the spatial filter light receiving optical system;
And a discriminating means for discriminating an object surface state based on the count value of the first counter means and the count value of the second counter means. 35. The road surface discriminating apparatus according to claim 1, further comprising a display device for displaying a result of the road surface discrimination by said discriminating means. 36. A traveling body including a vehicle equipped with the road surface identification device according to any one of claims 1 to 31. 37. A vehicle equipped with the road surface identification device according to any one of claims 1 to 31. 38. A judgment device for judging that the possibility of slip is high based on the result of the road surface judgment device of said road surface judgment device, and a warning device for notifying the judgment result by said judgment device. Item 37 vehicle. 39. The road surface discriminating apparatus according to claim 1, further comprising a speed detecting circuit for outputting a signal representing a ground speed based on the center frequency component. 40. A vehicle equipped with the road surface identification device according to claim 39. 41. A wheel speed sensor for detecting a wheel speed, a brake control means for controlling a brake based on a road surface discrimination result and a ground speed given from the road surface discriminating device, and a wheel speed given from the wheel speed sensor. 41. The vehicle according to claim 40, comprising: 42. The vehicle according to claim 37, further comprising means for controlling an accelerator based on a road surface determination result provided by said road surface determination device. 43. A vehicle according to claim 37, further comprising: a shock absorber provided on the vehicle body, and suspension control means for controlling said shock absorber in accordance with a road surface discrimination result by said road surface discrimination device. A vehicle according to paragraph 40. 44. A shock absorber according to claim 40, further comprising: a shock absorber provided on a vehicle body; and suspension control means for controlling said shock absorber in accordance with a road surface discrimination result by said road surface discrimination device and a ground speed. Vehicle.