JPS61257310A - Surface state sensor for road - Google Patents

Abstract

PURPOSE:To make discrimination of a surface state ever so accurate, by receiving a surface reflected light of light beams to the front of a car forward direction with two light receiving elements, while constituting it so as to judge the surface state from the ratio of a light receiving output level. CONSTITUTION:A light emitting element A is modulated by output of a pulse generator 10 and emits a light beam to a car forward direction. And, reflected light out of a road surface is received by light receiving elements B1 and B2, while these light receiving output values V1 and V2 are selected by a multiplexer MPX11, digitized by an analog-digital converter 12, and inputted into a central processing unit 13. This CPU 13 processes these values in accordance with the specified program, and if either of both output values V1 and V2 exceeds the specified threshold value Vth and V1/V2 is within the range of (1 - allowable value epsilon)-(1 + allowable value epsilon), it judges as a diffuse reflection pattern, but if it is not within the range, judges as a regular reflection pattern, respectively. If it is V1, V2<Vth, no judgement takes place. With this constitution, surface judgement becomes accurate enough.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical road surface condition sensor that detects unevenness on a road surface, distinguishing it from a change in color.

[Conventional technology]

Vehicle suspension control systems reduce the spring constant of the suspension on uneven roads to absorb vibrations caused by the road surface, and increase the spring constant on flat roads to improve running stability around corners. If it can be detected automatically, the switching of the spring constant can be automated.

Optical sensors used as this type of road surface condition sensor generally distinguish road surface conditions from differences in reflection patterns as shown in FIG. In the figure, 1 is a vehicle, 2 is an optical road surface sensor attached to the front end of the vehicle, and 3 is a road surface. (a) shows a case where the road surface 3 is flat, the light beam L+ from the sensor 2 is diffused on the road surface 3, and a portion of the diffused light L2 is incident on the sensor 2. The reflection putter 72 plates at this time become a diffuse reflection pattern. On the other hand, if there is a convex part 31 on the road surface 3 as in b), a part L3 of the light beam L+ is transmitted to the convex part 31.
Since it is specularly reflected on the slope of the sensor 2 and enters the sensor 2,
The level of light received by the sensor increases significantly. Such a reflection pattern P
2 is called a specular reflection pattern, and is clearly distinguished from the diffuse reflection pattern P+ in (a).

FIG. 6 shows this fact confirmed by experiment.

In the same figure (al indicates a measurement system, 4 is a reflector, 5 is a light emitting element having an optical axis inclined at 60 degrees with respect to the normal line 41, and 6 is an angle θ with the normal line 41 of 0° to 90°. This is an optical power meter that can be varied within a range of 2. Figure 4) shows a reflection pattern using an aluminum plate as the reflection plate 4 and a reflection pattern using cardboard. In both cases, a specular reflection pattern P2 appears at θ=60°, and the remaining area becomes a diffuse reflection pattern P1.

Since the received light level obtained from the specular reflection pattern P2 and the received light level obtained from the diffuse reflection pattern P1 are in a relationship such that the former is large and the latter is small, this can be used to optically distinguish between a flat road surface and an uneven road surface. Available.

[Problem that the invention seeks to solve]

However, there are other factors that change the received light level, such as differences in the color of the road surface (differences in reflectance), and changes in the received light level due to this, for example, an increase in the received light level due to a crosswalk can be treated as regular reflection from a convex part of the road surface. Processing will result in malfunction. The present invention attempts to distinguish this point and identify the road surface condition.

Means for Solving Problem C] FIG. 1 is a diagram explaining the principle of the present invention, in which the sensor section 2 includes a light emitting element A and two light receiving elements Bl, B2.
B2 is arranged so that the optical axis of the light receiving element B1 and the optical axis of the light receiving element B2 are separated from each other.

[Effect]

The specular reflection pattern due to the road surface convexity not only has a strong light reception level, but also has a sharp pattern shape as shown in FIG. On the other hand, the diffuse reflection pattern from a flat road surface has a broad pattern shape even though there are level differences due to different colors.

Therefore, instead of distinguishing whether it is specular reflection or diffuse reflection from the level, if you distinguish from the shape characteristics of the pattern,
Since level differences due to color differences are treated as a type of diffuse reflection pattern, they are not mistaken for road surface irregularities that cause specular reflection patterns.

In the present invention, in order to identify the shape characteristics of the reflection pattern,
The ratio of the light receiving levels V1 and V2 of the two light receiving elements B1 and B2 arranged as shown in FIG. 1 is utilized. In other words, the same figure (
In the case of diffuse reflection pattern P1 as in a), V +
/V 2 #1, whereas in the case of the specular reflection pattern P2 as shown in FIG. 2B, V1/v2 (1 or V + /V 2 >> 1).

This will be explained in detail below with reference to illustrated embodiments.

〔Example〕

FIG. 2 is a block diagram showing one embodiment of the present invention, and FIG. 3 is a flow chart showing its operation.

The light emitting element A is provided with a pulse oscillator 10 to distinguish it from ambient light.
It is modulated by the output of the light receiving elements Bl and B2, and the output Vl of the light receiving elements Bl and B2
, V2 is selected by multiplexer (MPX) 11 and A
/D converter (ADC) 12 converts it into a digital value. The CPU (microcomputer) 13 operates according to the flow shown in FIG. 3 to determine the road surface condition.

Since the output of the pulse oscillator 10 is input to the CPU 13, it is possible to know whether the light emitting element A is turned on from this. When the light emitting element A is turned on, the level 1 of the light receiving element B1 and the level v2 of the light receiving element B2 are read and stored in the RAM. Then Vl.

(2) If either one of 2 exceeds a predetermined threshold value VTH, the level ratio V + /V 2 is calculated. At this time Vl
.

No judgment is made when any of v2 is below VTR.

This is a noise countermeasure. When the ratio V+/v2 is calculated, it is determined whether it is within the range of (1-ε) to (1+ε). ε is a tolerance value; if it is within this range, it is determined to be a diffuse reflection pattern, otherwise it is determined to be a regular reflection pattern. If it is a diffuse reflection pattern (Y), nothing is done, but if it is a regular reflection pattern (N), the actuator control program is activated to temporarily loosen the suspension.

In this way, even if the color changes on a flat road surface, V +
/V2 is always close to 1, so it is determined to be a diffuse reflection pattern, and a malfunction in which the suspension is loosened due to misidentification as unevenness is avoided.

FIG. 4 shows a specific example, in which +a) is a detailed block diagram of the processing circuit, and middle) is a configuration diagram of the sensor. The processing circuit includes a drive circuit 14 that drives the light emitting element A in synchronization with the output of the pulse oscillator 10, amplifiers 15 and 16 that amplify the outputs of the light receiving elements Bl and B2, and a pulse modulation component only from the output of the up. Bandpass filters 17 and 18 are added to extract the . On the other hand, on the sensor side, the light emitting element A is housed in the light emitting part 20, and the light receiving elements Bl and B2 are housed in the light receiving part 20.
122, and the optical axis of the light-receiving element B1 is close to the optical axis of the light-receiving element A, and the optical axis of the light-receiving element B2 is arranged away from the optical axis to the light-emitting element.

1ozl12 is a lens for each part.

Note that one set of this type of road surface condition sensor may be provided at the front end of the vehicle, or two sets may be provided on the left and right sides. In the latter case, the left and right suspensions can be controlled individually.

〔Effect of the invention〕

As described above, according to the present invention, uneven road surfaces and flat road surfaces can be accurately distinguished, so that, for example, when automating suspension spring constant switching, it is possible to prevent malfunctions due to differences in the color of the road surface. There are advantages.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a block diagram showing an embodiment of the invention, Fig. 3 is a flowchart showing the processing contents, and Fig. 4 is a configuration diagram showing a specific example of the invention. , FIG. 5 is an explanatory diagram of the reflection pattern on the road surface, and FIG. 6 is a characteristic diagram of the reflection pattern based on actual measurements. In the figure, ■ is a vehicle body, 2 is a road surface condition sensor, 3 is a road surface, A is a light emitting element, and Bl and B2 are light receiving elements. Applicant: Fujitsu Ten Ltd. Applicant: Toyota Motor Corporation Patent Attorney Minoru Aoyagi 70-÷Yard Figure 3 (4) ■! Mouth t()0・Tsuku diagram (tl) tnη 1st 8th mouth B-th Jil stoppage example Figure 4

Claims (1)

[Claims] It includes a light emitting element that illuminates the road surface in front of the vehicle in the direction of travel, and first and second light receiving elements that receive reflected light from the road surface of the light beam emitted from the light emitting element. A road surface condition sensor characterized in that the output is input to a processing circuit and the road surface condition is determined from the level ratio thereof.