Road surface state estimating system and road surface state measuring apparatus Number:7,197,425 from the United States Patent and Trademark Office (PTO) owispatent

Title: Road surface state estimating system and road surface state measuring apparatus

Abstract: Provided is a road surface state estimating system for carrying out measuring along a plurality of measuring lines on a paved road surface, which improves the reliability of texture estimation of the road surface. A road surface state estimating system (1) includes a laser displacement meter (11) for measuring a distance to the road surface, a stepping motor (120A), rails (12A and 12B), a ball screw (121A), and mounting members (13A and 13B) for causing the laser displacement meter (11) to scan along the measuring lines, and a stepping motor (130), a rail (13), a ball screw (131), and a mounting member (11A) for moving the laser displacement meter (11) in a direction orthogonal to the measuring lines, which allows the laser displacement meter (11) to carry out measurement along the plurality of measuring lines while it is translated two-dimensionally. By determining a mean value of a plurality of texture scores such as MPDs calculated from the result of the measurement along the plurality of measuring lines, the reliability of the texture estimation is improved.

Patent Number: 7,197,425 Issued on 03/27/2007 to Masuyama,   et al.

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Inventors:	Masuyama; Yukiei (Saitama, JP), Katayama; Junnosuke (Tochigi, JP), Kusakari; Noritsugu (Tokyo, JP)
Assignee:	Seikitokyukogyo Co. Ltd. (Tokyo, JP)
Appl. No.:	11/217,353
Filed:	September 2, 2005

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Foreign Application Priority Data

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Sep 03, 2004 [JP]			2004-256715

Current U.S. Class:	702/158 ; 340/436; 702/167
Current International Class:	G01B 5/02 (20060101); G01B 5/14 (20060101)
Field of Search:	702/158,166,167 340/435,436,437,438

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References Cited [Referenced By]

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U.S. Patent Documents

	6023220		February 2000		Dobler et al.

Foreign Patent Documents

	2000-131043		May., 2000		JP
	2002-303514		Oct., 2002		JP

Other References

A Study of the Relationship between Surface Texture and Tire/Road Noise of Porous Asphalt Pavement, Journal of Pavement Engineering, vol. 7, pp. 1-1 to 1-6, 2002, The Japan Society of Civil Engineers (JSCE). cited by other . Predict of Tire/Road Noise from Road Surface Properties, Journal of Pavement Engineering, vol. 7, pp. 2-1 to 2-9, 2002, The Japan Society of Civil Engineers (JSCE). cited by other.

Primary Examiner: Barlow; John
Assistant Examiner: Walling; Meagan S
Attorney, Agent or Firm: Armstrong, Kratz, Quintos, Hanson & Brooks, LLP.

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Claims

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What is claimed is:

1. A road surface state measuring system comprising: a measuring means for measuring a distance to road surface; a scanning means for moving the measuring means to scan measurement positions of the distance to the road surface; the scanning means having a main scanning means and a sub scanning means; the scanning means moving the measuring means two-dimensionally; the main scanning means moving the measuring means in a predetermined main scanning direction to scan the measurement position; the sub scanning means moving the measuring means in a sub scanning direction orthogonal to the main scanning direction; and a calculating means for calculating texture scores used for estimating texture of the road surface based on a measurement data column of the distance to the road surface obtained by the moved measuring means, wherein the sub scanning means moves the position of the measuring means in the sub scanning direction; and the measuring means obtains a plurality of the measurement data columns corresponding to a plurality of positions in the sub scanning direction by continuously measuring the distance at predetermined measurement intervals when the measuring means is moved in the main scanning idrection by the main scanning means at the changed position and by obtaining measurement data column corresponding to the changed position.

2. A road surface state measuring system according to claim 1, wherein the calculating means divides the plurality of measurement data columns obtained by the measuring means into a plurality of subdata columns; the calculating means calculates the texture scores with regard to the subdata columns; and the calculating means calculates a mean value of the texture scores with regard to the subdata columns.

3. A road surface state measuring system according to claim 2, wherein the main scanning means comprises: a principal driving means for driving the measuring means and a principal guiding means for guiding the driven measuring means in the main scanning direction.

4. A road surface state measuring system according to claim 2, wherein the sub scanning means comprises: an auxiliary driving means for driving the measuring means and an auxiliary guiding means for guiding the driven measuring means in the sub scanning direction.

5. A road surface state measuring system according to claim 1, wherein the calculating means calculates the texture scores with regard to the plurality of measurement data columns obtained by the measuring means, and calculates a mean value of the texture scores.

6. A road surface state measuring system according to claim 5, wherein the main scanning means comprises: a principal driving means for driving the measuring means and a principal guiding means for guiding the driven measuring means in the main scanning direction.

7. A road surface state measuring system according to claim 5, wherein the sub scanning means comprises: an auxiliary driving means for driving the measuring means and an auxiliary guiding means for guiding the driven measuring means in the sub scanning direction.

8. A road surface state measuring system according to claim 1, wherein the main scanning means comprises: a principal driving means for driving the measuring means and a principal guiding means for guiding the driven measuring means in the main scanning direction.

9. A road surface state measuring system according to claim 1, wherein the sub scanning means comprises: an auxiliary driving means for driving the measuring means and an auxiliary guiding means for guiding the driven measuring means in the sub scanning direction.

10. A road surface state measuring system according to claim 1, wherein the sub scanning means comprises: an auxiliary driving means for driving the measuring means and an auxiliary guiding means for guiding the driven measuring means in the sub scanning direction.

11. A road surface state measuring system according to claim 1, wherein the main scanning means moves the measuring means in a circumferential direction, substantially in parallel with the road surface; and the sub scanning means moves the measuring means in a radial direction orthogonal to the circumferential direction.

12. A road surface state measuring system according to claim 11, wherein the measuring means changes its position in the radial direction by the sub scanning means, and the measuring means obtains a plurality of the measurement data columns along concentric (concentric-circle-like) measurement lines by measuring the distance at predetermined measurement intervals when the measuring means is moved in the circumferential direction by the main scanning means at the changed position and by obtaining the measurement data column corresponding to the changed position.

13. A road surface state measuring system according to claim 11, wherein the measuring means obtains the measurement data column along a spiral measurement line by measuring the distance at predetermined measurement intervals when the measuring means is moved in the circumferential direction by the main scanning means at predetermined speed and by obtaining the measurement data column.

14. A road surface state measuring system according to claim 13, wherein the plurality of kinds of texture scores include at least one of mean profile depth, accumulated extension ratio of asperities, and contact portion ratio.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a road surface state estimating system and road surface state measuring apparatus for estimating the state of texture of a paved road surface.

2. Description of the Related Art

Noise caused at the interface between a tire and a road surface when a vehicle is running (referred to as, for example, traffic noise) is a conventional problem as noise common nuisance. Traffic noise caused by a vehicle is closely related to the state of a paved road surface. In recent years, low noise pavement having a function of lowering the traffic noise is becoming prevailing, and attracting attention. The noise lowering effect of such low noise pavement is thought to be attributable to sound absorbing action of voids formed on the road surface and sound lowering action of the road surface based on the state of texture thereof. The texture of the road surface is also reflected on the friction between a tire of the running vehicle and the road surface, i.e., skid resistance. In this way, the texture of a road surface is thought to be an important factor for grasping the characteristics of a road surface.

JP 2002-303514 A (paragraphs [0010], [0012] to [0014], and [0030]; FIGS. 1 and 2) (hereinafter referred to simply as "JP 2002-303514 A") discloses a conventional method of measuring the state of the texture of a road surface. The measuring method described in JP 2002-303514 A includes the steps of: horizontally moving a laser displacement meter keeping a predetermined distance from the road surface to generate an original data column having data of measured distances to the road surface at respective positions at predetermined sampling intervals, the data being arranged in the order of measurement; generating a displaced data column having displaced data prepared by displacing the original data column in the direction of the column by a displacement pitch, the displacement pitch being an integral multiple of a sampling interval; determining a regression line of point data group with the original data being an independent variable and the displaced data being a dependent variable and calculating the proportion of variance of the regression line and the point data group to determine a correlated data group of the displacement pitch and the proportion of variance; regressively analyzing the correlated data group to determine an exponential regression curve of the proportion of variance with regard to the displacement pitch; determining the proportion of variance of the exponential regression curve and the correlated data group; and selecting, according to the proportion of variance, a proportion of variance for microscopic definition and a proportion of variance for macroscopic definition and defining the values of the displacement pitches in the exponential regression curve corresponding to the respective proportions of variance as microscopic roughness and macroscopic roughness of the road surface.

In the first step of the measuring method, a measuring apparatus as illustrated in FIG. 2 of the literature is used to measure the state of a road surface. The measuring apparatus has a laser displacement meter of a known structure and moving means for horizontally moving the laser displacement meter keeping a predetermined distance from the road surface. The moving means includes a pair of guide axes horizontally provided between supporting pieces of a body frame, a screw shaft (ball screw) rotatably supported by the supporting pieces and in parallel with the guide axes, and a stepping motor for rotating the screw shaft. The laser displacement meter is horizontally moved by the screw shaft which is driven by the stepping motor to rotate. It is to be noted that the sampling rate of data by a conventional laser displacement meter was on the order of ten samples per second (see, for example, Tsutomu IHARA et al., "A STUDY OF THE RELATIONSHIP BETWEEN SURFACE TEXTURE AND TIRE/ROAD NOISE OF POROUS ASPHALT PAVEMENT", Journal of Pavement Engineering, Vol. 7, pp. 1-1 to 1-6, 2002, The Japan Society of Civil Engineers (JSCE) (hereinafter referred to simply as "Non-Patent Literature 1")).

In such measurement of the state of a road surface, first, in a measurement section (referred to as a "measuring line") of several dozen centimeters to about one meter, the distance to the road surface is measured with the sampling intervals being, for example, about 0.1 millimeters (see, for example, JP 2002-303514 A). More specifically, microscopic asperities (displacement in the height direction) on the road surface are measured. Then, the result of the measurement along the measuring line (suppose it is 1 m in length) is divided into, for example, ten subsections each 10 cm in length, and texture scores in the respective subsections are determined. Here, the length of each subsection is a standard for calculating the scores, and sometimes referred to as a "standard length".

Further, in conventional measurement of the state of a road surface, as disclosed in JP 2002-303514 A, a laser displacement meter is moved in one direction (in the axial direction of the above-described screw shaft) to obtain data along the single measuring line. However, taking into account the fact that the actual texture of a road surface (paved surface) is not uniform depending on the selected aggregate, the way the roller compaction is made during the execution of work, and the like, measurement along only a single measuring line cannot obtain a satisfactory number of data and the measurement range is limited. Thus, it does not follow that the result of the measurement accurately reflects the whole road surface, and therefore, reliability problems may arise in the texture estimation based on the result of measurement according to the conventional method.

JP 2000-131043 A (paragraph [0017]) (hereinafter referred to simply as "JP 2000-131043 A") discloses another conventional method of measuring the state of the texture of a road surface. Disclosed in JP 2000-131043 A is a road surface roughness measuring apparatus used in combination with a rotating kinetic friction coefficient measuring device, the road surface roughness measuring apparatus including a frame having a plurality of legs for positioning the apparatus on a road surface, the frame having a vertically extending rotating shaft provided thereon, the rotating shaft having a rotary encoder attached to an upper end thereof and a rotating plate attached to a lower end thereof, the road surface roughness measuring apparatus further including a motor with a speed reducer for driving the rotating shaft through gears, and a laser displacement meter attached to the rotating plate, the laser displacement meter being positioned to carry out measurement along a measurement circle where the rotating kinetic friction coefficient measuring device measured a coefficient of kinetic friction by rotation of the rotating plate, the measurement circle being divided into a plurality of sections, and the road surface roughness for each of the divided sections being calculated based on signals from the laser displacement meter and the rotary encoder.

The measuring apparatus of JP 2000-131043 A estimates the texture along a measurement circle where a coefficient of kinetic friction of the road surface is measured. Since, similar to JP 2002-303514 A, the texture is estimated based on data on a single measuring line, it is difficult to expect that the result of estimation is sufficiently reliable.

It is to be noted that conventional estimation of the texture of road surface as disclosed in JP 2000-131043 A and JP 2002-303514 A is thought to have a certain extent of reliability when used in estimation of a relatively even road surface with only small asperities such as dense graded pavement. However, the reliability of such conventional estimation is particularly insufficient when applied to estimation of the texture of a road surface with large asperities such as drainage pavement which is becoming popular these days.

Further, in conventional texture estimation, MPD (Mean Profile Depth) described in, for example, JP2000-131043A (paragraph [0017]), accumulated extension ratio of asperities (see, for example, Non-Patent Literature 1), contact portion ratio (see, for example, Yoshimasa HASHIMOTO et al., "PREDICT OF TIRE/ROAD NOISE FROM ROAD SURFACE PROPERTIES", Journal of Pavement Engineering, Vol. 7, pp. 2-1 to 2-9, 2002, The Japan Society of Civil Engineers (JSCE) (hereinafter referred to simply as "Non-Patent Literature 2")), or the like is independently used as the score (hereinafter referred to as the "texture score"). Therefore, comprehensive estimation reflecting texture scores of a plurality of kinds cannot be conducted, and by extension, it is difficult to do reliable estimation.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above. An object of the present invention is to provide a road surface state measuring system and a road surface state measuring apparatus which can, in order to estimate the texture of a paved road surface, carry out measurement along a plurality of measuring lines on the road surface.

Another object of the present invention is to provide a road surface state measuring system and a road surface state measuring apparatus which can improve the reliability of texture estimation of a paved road surface.

In order to achieve the above objects, according to a first aspect of the present invention, there is provided a road surface state measuring system including: measuring means for measuring a distance to road surface; scanning means for moving the measuring means to scan measurement positions of the distance to the road surface; and calculating means for calculating texture scores used for estimating texture of the road surface based on a measurement data column of the distance to the road surface obtained by the moved measuring means, wherein the scanning means moves the measuring means two-dimensionally.

Further, according to a second aspect of the present invention, there is provided a road surface state measuring system according to the first aspect, wherein said scanning means includes: main scanning means for moving the measuring means in a predetermined main scanning direction to scan the measurement positions; and sub scanning means for moving the measuring means in a sub scanning direction orthogonal to the main scanning direction.

Further, according to a third aspect of the present invention, there is provided a road surface state measuring system according to the second aspect, wherein the measuring means changes its position in the sub scanning direction by the sub scanning means, and by continuously measuring the distance at predetermined measurement intervals when the measuring means is moved in the main scanning direction by the main scanning means at the changed position and obtaining the measurement data column corresponding to the position, obtains a plurality of the measurement data columns corresponding to a plurality of positions in the sub scanning direction.

Further, according to a fourth aspect of the present invention, there is provided a road surface state measuring system according to the third aspect, wherein the calculating means divides the plurality of measurement data columns obtained by the measuring means into a plurality of subdata columns, respectively, calculates the texture scores with regard to the respective subdata columns, and calculates a mean value of the texture scores with regard to the respective subdata columns.

Further, according to a fifth aspect of the present invention, there is provided a road surface state measuring system according to the third aspect, wherein the calculating means calculates the texture scores with regard to the plurality of measurement data columns obtained by the measuring means, respectively, and calculates a mean value of the texture scores with regard to the respective calculated plurality of measurement data columns.

Further, according to sixth to ninth aspects of the present invention, there is provided a road surface state measuring system according to any one of the second to fifth aspects, wherein the main scanning means includes: principal driving means for driving the measuring means; and principal guiding means for guiding the driven measuring means in the main scanning direction.

Further, according to tenth to thirteenth aspects of the present invention, there is provided a road surface state measuring system according to any one of the second to fifth aspects, wherein the sub scanning means includes: auxiliary driving means for driving the measuring means; and auxiliary guiding means for guiding the driven measuring means in the sub scanning direction.

Further, according to a fourteenth aspect of the present invention, there is provided a road surface state measuring system according to the second aspect, wherein the main scanning means moves the measuring means in a circumferential direction, substantially in parallel with the road surface, and the sub scanning means moves the measuring means in a radial direction orthogonal to the circumferential direction.

Further, according to a fifteenth aspect of the present invention, there is provided a road surface state measuring system according to the fourteenth aspect, wherein the measuring means changes its position in the radial direction by the sub scanning means, and by measuring the distance at predetermined measurement intervals when the measuring means is moved in the circumferential direction by the main scanning means at the changed position and obtaining the measurement data column corresponding to the position, obtains a plurality of the measurement data columns along concentric (concentric-circle-like) measuring lines.

Further, according to a sixteenth aspect of the present invention, there is provided a road surface state measuring system according to the fourteenth aspect, wherein the measuring means obtains the measurement data column along a spiral measuring line by measuring the distance at predetermined measurement intervals when the measuring means is moved in the circumferential direction by the main scanning means while moved in the radial direction by the sub scanning means at a predetermined speed and obtaining the measurement data column.

Further, according to a seventeenth aspect of the present invention, there is provided a road surface state measuring system according to the first aspect, further including: storing means for storing an acceptable range of the texture scores set in advance; deciding means for deciding whether the texture scores calculated by the calculating means are within the acceptable range or not; and notifying means for making a notification that the deciding means has decided that the texture scores are not within the acceptable range.

Further, according to an eighteenth aspect of the present invention, there is provided a road surface state measuring system according to the seventeenth aspect, wherein: the storing means stores acceptable ranges for the texture scores of a plurality of kinds; the calculating means calculates the texture scores of the plurality of kinds based on the measurement data columns; and the deciding means decides whether the respective calculated texture scores of the plurality of kinds are within the acceptable ranges stored in the storing means.

Further, according to a nineteenth aspect of the present invention, there is provided a road surface state measuring system according to the eighteenth aspect, wherein: the texture scores of the plurality of kinds include at least one of mean profile depth, accumulated extension ratio of asperities, and contact portion ratio.

Further, according to a twentieth aspect of the present invention, there is provided a road surface state measuring apparatus including: measuring means for measuring a distance to road surface; and scanning means for moving the measuring means to scan measurement positions of the distance to the road surface, the road surface state measuring apparatus obtaining a measurement data column of the distance to the road surface used for estimating texture of the road surface by the moved measuring means, wherein the scanning means moves the measuring means two-dimensionally.

The road surface state measuring system and a road surface state measuring apparatus according to the present invention each include the measuring means for measuring the distance to the road surface and the scanning means for two-dimensionally moving the measuring means with respect to the road surface, whereby the measurement can be carried out not only along a single measuring line as in conventional measuring but along a plurality of measuring lines.

Further, even when measuring along only a single measuring line is carried out, by moving the measuring means two-dimensionally, it is possible to make the measurement range by far wider than that of conventional measurement to obtain a large amount of measurement data, which can improve the reliability of texture estimation of a paved road surface.

In particular, the road surface state measuring system according to the fourth or fifth aspect of the present invention is configured to determine the mean value of the plurality of texture scores based on the plurality of measurement data columns corresponding to the plurality of measuring lines, whereby texture estimation can be conducted more accurately reflecting the whole road surface than a conventional system, which can improve the reliability of the estimation.

Further, the road surface state measuring system according to any one of the eleventh to thirteenth aspects of the present invention is configured to decide whether the texture scores are within the acceptable range or not, and if it is decided that they are outside the acceptable range, to make a notification to that effect, whereby it can be easily known that an abnormality has occurred. Then, the cause of the abnormality can be found in situ, feedback can be made in real time, and the execution of work can be corrected. Accordingly, the present invention is effectively utilized in situ.

In particular, the road surface state measuring system according to the twelfth aspect of the present invention can make a decision with regard to the texture scores of the plurality of kinds, whereby comprehensive texture estimation can be effectively conducted in situ.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic perspective view illustrating an exemplary outside structure of a road surface state measuring system according to an embodiment of the present invention;

FIG. 2 is a schematic perspective view illustrating an exemplary structure of a laser displacement meter and rails in the road surface state measuring system according to the embodiment of the present invention;

FIG. 3A is a schematic front view illustrating an exemplary structure for moving the laser displacement meter in the road surface state measuring system according to the embodiment of the present invention;

FIG. 3B is a schematic sectional view illustrating the exemplary structure for moving the laser displacement meter in the road surface state measuring system according to the embodiment of the present invention;

FIG. 4A is a schematic side view illustrating an exemplary structure for moving the laser displacement meter in the road surface state measuring system according to the embodiment of the present invention;

FIG. 4B is a schematic sectional view illustrating the exemplary structure for moving the laser displacement meter in the road surface state measuring system according to the embodiment of the present invention;

FIG. 5 is a schematic side view illustrating an exemplary structure for vertically moving the laser displacement meter and the like in the road surface state measuring system according to the embodiment of the present invention;

FIG. 6 is a schematic plan view illustrating an exemplary structure of a control box in the road surface state measuring system according to the embodiment of the present invention;

FIG. 7 is a block diagram illustrating an exemplary structure of a control system in the road surface state measuring system according to the embodiment of the present invention;

FIG. 8 is an explanatory graph of a method of calculating an MPD performed by the road surface state measuring system according to the embodiment of the present invention;

FIG. 9 is an explanatory graph of a method of calculating an accumulated extension ratio performed by the road surface state measuring system according to the embodiment of the present invention;

FIG. 10 is an explanatory graph of a method of calculating a contact portion ratio performed by the road surface state measuring system according to the embodiment of the present invention;

FIG. 11 is a flow chart illustrating an exemplary workflow using the road surface state measuring system according to the embodiment of the present invention;

FIG. 12 is an explanatory view of a mode of measurement performed by the road surface state measuring system according to the embodiment of the present invention;

FIG. 13 is an explanatory view of a mode of measurement performed by the road surface state measuring system according to the embodiment of the present invention;

FIG. 14A is an explanatory graph illustrating an exemplary state of variation of MPDs obtained based on measurement with regard to various kinds of pavements for reviewing the effectiveness of the texture measuring of a road surface according to the present invention;

FIG. 14B is a table of statistical data calculated from the state of variation of the MPDs for reviewing the effectiveness of the texture measuring of the road surface according to the present invention;

FIG. 15A is a graph illustrating an exemplary state of variation in a traverse direction of the MPDs obtained with regard to a measurement region for reviewing the effectiveness of the texture estimation of a road surface according to the present invention;

FIG. 15B is a graph illustrating an exemplary state of variation in a longitudinal direction of the MPDs obtained with regard to the measurement region for reviewing the effectiveness of the texture estimation of the road surface according to the present invention;

FIG. 16A is a graph showing a distribution of the MPDs obtained with regard to the measurement region for reviewing the number of samples necessary for effectively estimating the texture of a road surface;

FIG. 16B is a table showing the result of calculation of interval estimation for a population mean with regard to the distribution of the MPDs for reviewing the number of samples necessary for effectively measuring the texture of the road surface; and

FIG. 16C is a table showing the accuracy of the estimation when 110 MPDs were used to estimate the texture of a road surface for reviewing the number of samples necessary for effectively estimating the texture of the road surface.

FIG. 17A is a schematic bottom view illustrating an exemplary structure for making the laser displacement meter scan in a road surface state measuring system according to a modified example of the embodiment of the present invention; and

FIG. 17B is a schematic side view illustrating the exemplary structure for making the laser displacement meter scan in the road surface state measuring system according to the modified example of the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

According to the present invention, the texture of a road surface is estimated by carrying out measurement along a plurality of measuring lines as opposed to conventional measurement along only a single measuring line. Further, in the measurement according to the present invention compared with the conventional measurement the measurement is characterized in that a plurality of position within the measuring range is measured. A preferred embodiment of the present invention suitable for materializing such a novel measuring method is now described with reference to the attached drawings.

[Overall Structure of the System and Structures of Units Thereof]

FIG. 1 illustrates a schematic outside structure of a road surface state measuring system 1 according to an embodiment of the present invention. The road surface state measuring system 1 includes a plurality of devices mounted on a carriage 2 for moving the system 1. The carriage 2 has: a frame 3 formed of, for example, metal, and provided with a handle portion; upper and lower device-mounting shelves 4 and 5 fixed to the frame 3; and wheels 6 such as casters provided on the bottom of the lower device-mounting shelf 5. Stoppers for preventing rotation of the wheels 6 may be provided to prevent free movement of the system 1 during measurement or during storage.

The lower device-mounting shelf 5 has a measurement body portion 10 for housing various kinds of devices such as a laser displacement meter described below and a battery 40 for supplying electric power both mounted thereon. A power supply circuit (described below) for controlling power supply to the measurement body portion 10 and the like is connected to the battery 40. Further, the upper device-mounting shelf 4 has a (notebook) computer 20 for controlling operation of units of the system, for analyzing the result of measurement by the measurement body portion 10, and the like, and a control box 30 for operating units of the system both mounted thereon.

The laser displacement meter is a device for measuring the distance to an object to be measured (road surface). Scanning means which will be described below scans measurement positions of the laser displacement meter along measuring lines, thereby obtaining displacement of the distance to the road surface along the measuring lines, that is, displacement of the asperities on the road surface along the measuring lines. The state of the texture of the road surface is estimated based on the state of the displacement of the asperities on the road surface.

The laser displacement meter used in this embodiment has a known structure. For example, the laser displacement meter is configured to include a laser light source such as a semiconductor laser, a condenser lens for condensing laser light from the laser light source, an imaging lens for imaging using laser light reflected from the road surface, a photoreceptor for detecting imaging positions of the laser light such as a position sensitive detector (PSD), an arithmetic circuit for calculating the distance between the laser displacement meter and the road surface based on the result of the detection of the imaging positions using the laser light, and the like. The calculation processing of the distance may be performed by the computer 20. It is to be noted that the measurement positions of the laser displacement meter described above correspond to positions on the road surface where the laser light is reflected.

(Measurement Body Portion)

FIG. 2 illustrates a schematic structure of a laser displacement meter 11 housed in the measurement body portion 10, and of rails 12A, 12B, and 13 for guiding the movement of the laser displacement meter 11. The rails 12A and 12B are provided in parallel with each other while the rail 13 is provided so as to connect the rails 12A and 12B via mounting members 13A and 13B. The rails 12A and 12B and the rail 13 are orthogonal to each other.

Further, at least when the measurement is carried out by the laser displacement meter 11, rails 12A, 12B, and 13 are positioned so as to be in parallel with the road surface. This allows the laser displacement meter 11 to be translated with respect to the road surface. It is preferable that, in this way, the laser displacement meter 11 is translated with respect to the road surface so as not to macroscopically change the distance between the laser displacement meter 11 and the road surface, although the present invention is not limited thereto. For example, the laser displacement meter 11 may be configured to be linearly moved, e.g., the laser displacement meter 11 may be moved in a slanted direction with respect to the road surface. Further, if the laser displacement meter 11 is configured such that its locus of movement can be referred to, it is no longer necessary that the movement of the laser displacement meter 11 is linear. More specifically, the result of the measurement of the distance to the road surface can be corrected based on the locus of movement of the laser displacement meter 11.

The laser displacement meter 11 constitutes "measuring means" of the present invention, and is attached to a side of the rail 13 through amounting member 11A. The mounting member 11A is provided so as to be movable in a longitudinal direction of the rail 13 by being driven by a stepping motor. The laser displacement meter 11 is moved integrally with the mounting member 11A. The longitudinal direction of the rail 13 is herein referred to as "sub scanning direction". The laser displacement meter 11 is controlled so as not to carry out measurement when moved in the sub scanning direction (described in detail below).

The mounting members 13A and 13B are provided so as to be movable in a longitudinal direction of the rails 12A and 12B on the rails 12A and 12B by being driven by a stepping motor. The laser displacement meter 11 is moved in the longitudinal direction of the rails 12A and 12B integrally with the rail 13 and the mounting members 13A and 13B.

The longitudinal direction of the rails 12A and 12B is herein referred to as "main scanning direction". The measurement body portion 10 is positioned such that the main scanning direction is the direction of the measuring lines (in other words, the direction of the measuring lines in this embodiment is the main scanning direction). The laser displacement meter 11 is controlled so as to carry out measurement while it is being moved in the main scanning direction (described in detail below). This allows the measurement positions on the road surface by the laser displacement meter 11 to be scanned in the main scanning direction.

In this way, the road surface state measuring system 1 of this embodiment is characterized by a structure where the laser displacement meter 11 is independently moved in the main scanning direction and in the sub scanning direction orthogonal to the main scanning direction. It is to be noted that, generally, the rails 12A and 12B and the rail 13 may be positioned diagonally with respect to each other such that the main scanning direction and the sub scanning direction are diagonal with respect to each other. In other words, according to the present invention, it is enough that the laser displacement meter 11 is two-dimensionally movable.

FIGS. 3A and 3B illustrate a schematic structure for moving the laser displacement meter 11 in the longitudinal direction of the rail 13 (sub scanning direction). FIG. 3A is a front view of the laser displacement meter 11, the rail 13, and the like, while FIG. 3B is a sectional view taken along the width direction of the rail 13.

The side of the rail 13 on the side of the laser displacement meter 11 is open along its longitudinal direction. A ball screw 131 is provided in the rail 13 along its longitudinal direction. A stepping motor 130 is provided on one end of the rail 13, and one end of the ball screw 131 is connected to a rotating shaft of the stepping motor 130. The other end of the ball screw 131 is rotatably connected to the other end of the rail 13. The ball screw 131 is driven by the stepping motor 130 and rotates about an axis O1.

A protrusion 11a protruding from the above-described opening on the side of the rail 13 toward the inside of the rail 13 is formed on the mounting member 11A. A female thread 11b is provided approximately in the center of the protrusion 11a along the longitudinal direction of the rail 13. The ball screw 131 is engaged in the female thread 11b.

When the ball screw 131 is driven by the stepping motor 130 and rotates about the axis O1, the engagement of the ball screw 131 and the female thread 11b moves the mounting member 11A in the longitudinal direction of the rail 13. The direction of movement of the mounting member 11A is controlled by the direction of rotation of the stepping motor 130. In this way, the laser displacement meter 11 is movable in the sub scanning direction.

The stepping motor 130, the rail 13, the ball screw 131, and the mounting member 11A constitute "sub scanningmeans" of the present invention. The stepping motor 130 constitutes "auxiliary driving means" of the present invention, for driving the laser displacement meter 11. The rail 13, the ball screw 131, and the mounting member 11A constitute "auxiliary guiding means" of the present invention, for guiding in the sub scanning direction the laser displacement meter 11 and the like driven by the stepping motor 130.

FIGS. 4A and 4B illustrate a schematic structure for moving the rail 13 (i.e., the laser displacement meter 11) in the longitudinal direction of the rail 12A (main scanning direction). FIG. 4A is a side view of the rail 12A, the rail 13, and the like, while FIG. 4B is a sectional view taken along the width direction of the rail 12A. If necessary, a mechanism similar to the one illustrated in FIGS. 4A and 4B may be provided on the side of the rail 12B.

A top face of the rail 12A is open along its longitudinal direction. A ball screw 121A is provided in the rail 12A along its longitudinal direction. A stepping motor 120A is provided on one end of the rail 12A, and one end of the ball screw 121A is connected to a rotating shaft of the stepping motor 120A. The other end of the ball screw 121A is rotatably connected to the other end of the rail 12A. The ball screw 121A is driven by the stepping motor 120A and rotates about an axis O2.

A protrusion 13a protruding from the above-described opening on the top face of the rail 12A toward the inside of the rail 12A is formed on the mounting member 13A. A female thread 13b is provided approximately in the center of the protrusion 13a along the longitudinal direction of the rail 12A. The ball screw 121A is engaged in the female thread 13b.

When the ball screw 121A is driven by the stepping motor 120A and rotates about the axis O2, the engagement of the ball screw 121A and the female thread 13b moves the mounting member 13A in the longitudinal direction of the rail 12A. The direction of movement of the mounting member 13A is controlled by the direction of rotation of the stepping motor 120A. In this way, the laser displacement meter 11 is movable in the main scanning direction.

The stepping motor 120A, the rails 12A and 12B, the ball screw 121A, and the mounting members 13A and 13B constitute "main scanning means" of the present invention. The stepping motor 120A constitutes "principal driving means" of the present invention, for driving the laser displacement meter 11. The rails 12A and 12B, the ball screw 121A, and the mounting members 13A and 13B constitute "principal guiding means" of the present invention, for guiding in the main scanning direction of the laser displacement meter 11 and the like driven by the stepping motor 120A. When a stepping motor and a ball screw are also provided on the side of the rail 12B, they are also included in the main scanning means, and the stepping motor is included in the principal driving means while the ball screw is included in the principal guiding means.

The stepping motor 120A, the rails 12A and 12B, the ball screw 121A, and the mounting members 13A and 13B which constitute the main scanning means and the stepping motor 130, the rail 13, the ball screw 131, and the mounting member 11A which constitute the sub scanning means together constitute the "scanning means" of the present invention.

It is to be noted that the structure illustrated in FIG. 2 to FIG. 4 constitutes an exemplary "road surface state measuring apparatus" of the present invention.

(Elevator/Mechanism)

An elevator mechanism for vertically moving the laser displacement meter 11 and a moving mechanism for moving the laser displacement meter 11 (the rails 12A, 12B, and 13, the stepping motors 120A and 130, and the like) is provided in the measurement body portion 10. The lower device-mounting shelf 5 has an opening (not shown) formed therein the area of which is smaller than that of a bottom surface of the measurement body portion 10. The elevator mechanism vertically moves the laser displacement meter 11 and the above-described moving mechanism through the opening. The laser displacement meter 11 and the like descend to a predetermined position near the road surface when the state of the texture of the road surface is estimated, and are housed in the measurement body portion 10 when the road surface state measuring system 1 is moved. The vertical movement of the laser displacement meter 11 and the like is carried out according to operation by an operator (described in detail below). Such an elevator mechanism can prevent the laser displacement meter 11 and the like from hitting or rubbing on bumps on the road surface when the system 1 is moved. Further, with a structure where the bottom surface of the moving mechanism or the like comes in contact with the road surface when the laser displacement meter 11 and the like descend, the stability of the laser displacement meter 11 during measurement is enhanced. In other words, even without the above-described stoppers for preventing rotation of the wheels 6, the laser displacement meter 11 can be prevented from freely moving during measurement.

FIG. 5 is a schematic illustration of an exemplary elevator mechanism. An elevator mechanism 50A illustrated in the figure directly moves the rail 12A vertically, and a similar elevator mechanism 50B is provided on the side of the rail 12B. The operation of the elevator mechanism 50A and the operation of the elevator mechanism 50B are simultaneously controlled. The laser displacement meter 11, the rail 13, the stepping motors 120A and 130, and the like are driven by the pair of elevator mechanisms 50A and 50B and vertically moved integrally with the rails 12A and 12B.

The elevator mechanism 50A illustrated in FIG. 5 includes a motor 51A fixedly provided on an inner wall of the housing of the measurement body portion 10 or the like, a gear 53A coaxially connected to a rotating shaft 52A of the motor 51A to rotate integrally with the rotating shaft 52A, and an arm 54A an end of which is fixed to the rail 12A by screws 56A with its longitudinal direction being the vertical direction. An engaging portion 55A for engaging with the gear 53A is formed on one side of the arm 54A.

When the motor 51A rotates the rotating shaft 52A, the rotational movement of the gear 53A which rotates integrally with the rotating shaft 52A is converted to vertical movement of the arm 54A by the engagement of the gear 53A and the engaging portion 55A, which vertically moves the rail 12A.

The direction of the movement of the rail 12A is switched by switching the direction of rotation of the motor 51A. In FIG. 5, when the motor 51A rotates the rotating shaft 52A clockwise, the rail 12A is moved downward, while when the motor 51A rotates the rotating shaft 52A counterclockwise, the rail 12A is moved upward.

It is to be noted that the elevator mechanism of the present invention is not limited to the structure illustrated in FIG. 5, and an arbitrary structure can be applied so far as the laser displacement meter 11 and the like can ascend/descend. For example, an elevator mechanism may be applied where the rails 12A and 12B are rotatably connected to one end of a pair of arms, respectively, and stepping motors are provided on the respective other ends, such that the arms are horizontally positioned when the laser displacement meter 11 and the like are housed in the measurement body portion 10 and the arms are rotated downward in a vertical plane by the stepping motors when the laser displacement meter 11 and the like descend to the vicinity of the road surface.

Further, a mechanism where an operator manually makes the laser displacement meter 11 and the like ascend/descend may also be applied.

Further, the elevator mechanism is not required to be housed in the measurement body portion 10. For example, when a structure where the measurement body portion 10 itself is vertically moved is adopted, the elevator mechanism can be provided outside the measurement body portion 10. In this case, the above-described opening of the lower device-mounting shelf 5 is formed such that its area is larger than that of the bottom surface of the measurement body portion 10.

(Control Box)

FIG. 6 is a plan view illustrating a schematic structure of the control box 30. A power button 31 for switching on/off the system 1, a voltage indicator 32A for indicating power source voltage supplied by the battery 40, a current indicator 32B for indicating power source current, an up button 33A operated to make the laser displacement meter 11 and the like ascend using the elevator mechanisms 50A and 50B, a down button 33B operated to make the laser displacement meter 11 and the like descend using the elevator mechanisms 50A and 50B, a measurement start button 34A operated to start measurement using the laser displacement meter 11, and a measurement stop button 34B operated to stop the measurement are provided on an operating panel of the control box 30.

It is to be noted that, when the above-described operation is effected using a keyboard, a mouse, or the like of the computer 20, it is not necessary to provide the control box 30. Further, when necessary, means (e.g., buttons) for effecting operation other than the above-described operation may be provided. Still further, when, for example, the computer 20 has a dedicated battery mounted thereon, the computer 20 may be switched on/off not with the power button 31 but with a power button of the computer 20 itself or the like.

[Structure of Control System]

Next, a structure of a control system of the road surface state measuring system 1 of this embodiment is described with reference to a block diagram of FIG. 7. As described above, the system 1 is controlled by the computer 20.

It is to be noted that, in this embodiment, in order to move with stability the rail 13 in the longitudinal direction of the rails 12A and 12B (main scanning direction), the structure illustrated in FIG. 4 is also provided on the side of the rail 12B, and a stepping motor on the side of the rail 12B is designated by reference symbol 120B.

As illustrated in FIG. 7, the laser displacement meter 11, the stepping motors 120A, 120B, and 130, the motors 51A and 51B, and the control box 30 of the measurement body portion 10 are connected to the computer 20. The stepping motors 120A, 120B, and 130 and the motors 51A and 51B are connected to the computer 20 through a power supply circuit 60.

(Computer)

The computer 20 includes a CPU 21, a hard disk drive (HDD) 22, a display unit 23, an audio output unit 24, a ROM 25, a RAM 26, and a transmitting/receiving interface (I/F) 27.

It is to be noted that, instead of HDD 22, a drive (for reading from and writing to an arbitrary storage medium such as a CD-ROM, a CD-R (W), a DVD-ROM, a DVD-RAM, an MO, and a floppy (registered trademark) disk) accessible by the computer 20 may be used. In this case, necessary information is stored in advance in the storage medium.

The CPU 21 controls the units of the system 1 and analyzes the result of measurement by the laser displacement meter 11 by decompressing on the RAM 26 and executing a computer program (not shown) stored in the HDD 22 or the ROM 25.

Such computer programs include: system control programs for causing the CPU 21 to control, for example, the measurement using the laser displacement meter 11, the movement of the laser displacement meter 11 in the main scanning direction and in the sub scanning direction, the ascent/descent operation of the laser displacement meter 11 and the like using the elevator mechanism 50A; score calculation programs for causing the CPU 21 to calculate the texture scores of the road surface; and decision programs for causing the CPU 21 to decide whether the calculated texture scores are appropriate or not. The CPU 21 operates as a control unit 211, a score calculation unit 212, a score decision unit 213, and the like in this order by executing the above programs, respectively.

The control unit 211 controls the units of the system according to processing flows of the system control programs. When a button on the control box 30 is operated, an operation signal is sent to the computer 20 and the control unit 211 controls the system based on the operation signal.

The score calculation unit 212 corresponds to "calculating means" of the present invention, and calculates the texture scores of the road surface based on the measurement data obtained by the laser displacement meter 11. In this embodiment, as a texture score, at least one of a mean profile depth (MPD), an accumulated extension ratio of asperities (sometimes referred to simply as an accumulated extension ratio), and a contact portion ratio is used. Those texture scores are briefly described below.

The score decision unit 213 corresponds to "deciding means" of the present invention, and decides whether the texture scores calculated by the score calculation unit 212 fall within a predetermined acceptable range or not. At this time, the score decision unit 213 makes a decision referring to information which is stored in the HDD 22 and described below.

A directory for storing information indicating the acceptable range of the texture scores is set in the HDD 22. The directory is referred to as a score information memory unit 221. Information indicating the acceptable range of the respective texture scores set in advance is stored in the score information memory unit 221 prior to actual measurement. The score information memory unit 221 (HDD 22) constitutes "storing means" of the present invention.

In this embodiment, an MPD acceptable range information 221A indicating an acceptable range of an MPD, an accumulated extension ratio acceptable range information 221B indicating an acceptable range of an accumulated extension ratio, and a contact portion ratio acceptable range information 221C indicating an acceptable range of a contact portion ratio are stored in the score information memory unit 221.

It is preferable that the acceptable range information of the respective texture scores be set for each kind of a road surface. For example, by setting the acceptable range information for each kind of pavement such as drainage pavement or dense graded pavement, or by setting the acceptable range information for each characteristic of the composition of the pavement such as maximum particle size (e.g., 13 mm or 5 mm) of aggregate in the asphalt mixture, the texture of various kinds of paved road surfaces can be evaluated. Further, the acceptable range information may be set for each combination of the kind of pavement and the characteristic of the composition of the pavement.

The display unit 23 is formed of a monitor of the (notebook) computer 20, and the audio output unit 24 is formed of a speaker or the like. The display unit 23 and the audio output unit 24 constitute "notifying means" of the present invention. The transmitting/receiving I/F 27 is formed of an interface circuit for transmitting/receiving data and the like.

The power supply circuit 60 is connected to the battery 40. The power supply circuit 60 receives a control signal from the computer 20 to supply power from the battery 40 to the stepping motors 120A, 120B, and 130 and the motors 51A and 51B.

To the stepping motors 120A, 120B, and 130, the power is pulsed, and the stepping motors 120A, 120B, and 130 are rotated by an angle corresponding to the number of the pulses to move the laser displacement meter 11.

To the motors 51A and 51B, the power is supplied for a predetermined period of time to make the laser displacement meter 11 and the like ascend/descend. When stepping motors are used as the motors 51A and 51B, the power is pulsed by a predetermined number to make the laser displacement meter 11 and the like ascend/descend by a predetermined distance.

[Texture Score]

Texture scores of a road surface used in this embodiment are now described in brief. In this embodiment, at least one of an MPD, an accumulated extension ratio, and a contact portion ratio is used as the score. In the following, the three kinds of texture scores are described with reference to FIG. 8 to FIG. 10. It is to be noted that, according to the present invention, an arbitrary score other than those may also be applied.

(MPD)

First, a mean profile depth (MPD) is described. An MPD is commonly used in a method for analyzing the texture of a road surface, and how to calculate an MPD is specified in ISO (see CHARACTERIZATION OF PAVEMENT TEXTURE UTILIZING SURFACE PROFILES PART-1: DETERMINATION OF MEAN PROFILE DEPTH, International Organization for Standardization, International Standard ISO 13473-1, 1996).

An MPD is calculated in the following way for each section (standard length section) determined by dividing each measuring line in measurement using the laser displacement meter 11 by a predetermined length (standard length). First, an average height in the standard length section is determined, the standard length section is divided into two at the center, and the maximum height is determined with regard to each of the divided sections. Then, the difference between the maximum height in each divided section and the average height of the standard length section is calculated, and arithmetic mean of the two differences is determined. The result of the calculation is defined as the MPD of the standard length section.

More specifically, as illustrated in FIG. 8, when the average height of the standard length section is denoted by H.sub.MEAN and the maximum heights in the first and second divided sections are denoted by H.sub.MAX1 and H.sub.MAX2, respectively, the MPD of the standard length section is expressed as follows: MPD={H.sub.MAX1-H.sub.MEAN}/2+{H.sub.MAX2-H.sub.MEAN}/2 Here, the graph illustrated in FIG. 8 shows displacement in the distance to the road surface (the height of the road surface) in the standard length section measured by the laser displacement meter 11. Therefore, the graph in the figure is a sectional view of the shape of the road surface in the standard length section. It is to be noted that the graph is illustrated with the asperities emphasized.

Suppose that the length of the measuring line in the measurement by the laser displacement meter 11 is 1 m and the standard length is 10 cm. Since the measuring line is divided into ten standard length sections, ten MPDs are obtained with regard to the measuring line.

(Accumulated Extension Ratio)

An accumulated extension ratio is described in, for example, Non-Patent Literature 1. The accumulated extension ratio is now described with reference to FIG. 9. The graph illustrated in the figure shows, similarly to the graph illustrated in FIG. 8, displacement in the height of the road surface (the shape of the road surface) in the standard length sections measured by the laser displacement meter 11. The graph is also illustrated with the asperities emphasized.

An accumulated extension ratio is calculated in the following way. First, the maximum height in each standard length section of the measuring line is determined, and height lower than the maximum height by a predetermined length (hereinafter referred to as lower limit height) is determined. Then, in each standard length section, the length of the road surface (including asperities) within a measurement range where the height exceeds the lower limit height is determined, and the determined lengths are summed up with regard to all the standard length sections. Further, the result of the calculation is divided by the length of the measuring line, which is defined as the accumulated extension ratio of the measuring line.

The calculation illustrated in FIG. 9 is now specifically described. First, one measuring line is divided into a first standard length section, a second standard length section, a third standard length section, . . . , and the above-described predetermined length from the maximum height to the lower limit height is set as .times.mm (for example, 2 mm). The maximum heights H1.sub.MAX, H2.sub.MAX, H3.sub.MAX, . . . in the standard length sections are respectively determined, and the lower limit heights H1.sub.LOW, H2.sub.LOW, H3.sub.LOW, . . . in the standard length sections are respectively determined.

With regard to the first standard length section, a length L11 of the road surface in a measurement range where the height exceeds the lower limit height H1.sub.LOW is determined. More specifically, in the first standard length section of the graph of FIG. 9, the length L11 of the graph in the measurement range where the value is between H1.sub.MAX and H1.sub.LOW is determined. With regard to the second standard length section, since there are four measurement ranges where the height exceeds the lower limit height H2.sub.LOW, lengths L21, L22, L23, and L24 of the road surface of the four measurement ranges are determined.