WO2003106924A1

WO2003106924A1 - A device for measuring the profile of a roadway

Info

Publication number: WO2003106924A1
Application number: PCT/SE2003/000581
Authority: WO
Inventors: Hans HEDSTRÖM
Original assignee: Digatech AB
Current assignee: Digatech AB
Priority date: 2002-04-26
Filing date: 2003-04-10
Publication date: 2003-12-24
Anticipated expiration: 2004-10-26
Also published as: SE0201264L; SE0201264D0; SE520280C2; AU2003222555A1

Abstract

The present invention relates to an arrangement for measuring the transverse profile of a roadway, wherein the arrangement comprises a laser unit (1, 1) carried by a vehicle (10) which is intended to be driven along said roadway, wherein the laser unit is adapted to illuminate the roadway (4) vertically, and wherein a vehicle-carried sensor (3) is adapted to detect the distance to the roadway illuminated by the laser unit. The laser unit is adapted to illuminate the roadway along a line (11) that extends transversely of the vehicle and the roadway, said laser light being directed generally in a vertical plane. Also included is a vehicle-carried generally horizontal extending reference line (5). The sensor (3) includes an electronic camera which is mounted on the vehicle at a longitudinal distance (t) from the laser light plane and which views the laser line (11) projected onto the roadway (4) and also the reference line (5) at one and the same time. The arrangement includes register means (8) adapted to register the angle detected by the camera between the projected laser line (11) and the reference line (5) at a plurality of positions along the projected laser line (11).

Description

A DEVICE FOR MEASURING THE PROFILE OF A ROADWAY

The present invention relates to an arrangement for measuring the cross-profile of a roadway of the kind defined in the preamble of the accompanying Claim 1.

It is known to measure or determine the profile of a roadway with the aid of a number of distance measuring devices that are disposed along a vehicle-mounted bar which extends transversely to the direction in which the vehicle is driven. Each measuring device is comprised of a laser unit that directs a narrower laser beam vertically onto the surface of the road, and an optical position sensor spaced horizontally from the laser unit. The position sensor functions to detect a light spot projected by the laser onto the road surface. The vertical distance from the distance measuring device to the laser spot projected onto the road surface can be calculated with the aid of the known direction from the position sensor to the laser projected spot and with knowledge of the distance between the position sensor and said spot. A distance measuring device is required for each measuring position transversely of the driven direction of the vehicle. In order to achieve an accurate cross profile, it is necessary to place the measuring points along the bar relatively close together. The costs involved by an arrangement of this nature are highly dependent on the number of measuring points provided. Moreover, it is very difficult in practice to achieve such small spacing between respective measuring points along the beam. Because the distances measured are dependent on dynamic variations in the distance of the measuring devices from the road surface, it is normally necessary to mount an acceleration sensor at respective ends of the bar so as to detect vertical movement of said ends. It is also normally necessary to include an inclination sensor, for instance a gyroscope, for sensing the slope of the bar, particularly in its longitudinal direction, so that the distances measured by the distance measuring devices can also be combined to provide road profile curves in the longitudinal direction of the road and so that the road camber or lateral slope can also be shown.

Another known technique applied in practice is one in which a laser unit is used to project a line of laser light onto the road surface transversely to the direction in which the vehicle is driven, and to image the profile of the line with the aid of a camera that is mounted on the vehicle at a significant distance from said line and to consider the image in a direction that has but a small deviation from the driven direction of the vehicle. One difficulty with this technique resides in the sensitivity of the camera to shakes and vibrations, caused by the long distance of the camera from said line.

Consequently there are a large number of desiderata regarding the measurement of a' road profile. For instance, it is, of course, desirable to enable profile measurements to be made with the vehicle carrying the measuring equipment travelling at a relatively high speed, for instance at normal traffic speeds.

It is also desirable to measure the cross profile of a roadway from a very large number of measuring points, and also with a large number of measurement values when measuring or determining the length profile of said roadway.

It is also desirable that the road camber or slope of the road can be determined in its transverse direction.

It is also desirable to be able to extend transverse measurement of the road profile to include accurate evaluation of the road profile in the longitudinal direction of the roadway.

It is also desirable to be able to carry out measurement in the transverse direction of the roadway over a distance that exceeds the width of the vehicle.

Accordingly, it is an object of the present invention to provide an arrangement with which these desiderata can be satisfied either totally or in part.

This object is achieved by means of the invention.

The invention is defined in the accompanying independent Claim

Further embodiments of the invention have been made apparent in the depending claims.

According to one embodiment of the invention preferred in practice at present, the arrangement includes an electronic camera, e.g. a CCD-camera, which is mounted on the vehicle, suitably on its underside, in longitudinally spaced relationship with a vehicle- earned element that extends transversely across the vehicle.

The element carries one or more laser units that establish a vertical laser light plane which extends along the element and which projects a line of laser light onto the roadway. The element also includes a reference line. The camera views or detects the distance between the reference line and the line projected onto the roadway by the laser unit or units at a selected number of points along the reference line. The reference line may, for instance, consist of an illuminated strip of reflex tape placed on the element, or may include special characteristic features along its length, for example interruptions or locally varying line heights. These characteristic features enable the camera to localise predetermined positions along the reference line. When using several cameras side-by-side, so that each camera will have a correspondingly small viewing angle in the horizontal plane, the characteristic features can be used to define the horizontal viewing angles of the different cameras.

The extension of the reference line can be corrected horizontally or vertically, so that the respective cameras will detect a constant vertical angle between the reference line and the line projected onto a horizontal (road) - surface.

The reference line and/or the projected line may consist of a series of mutually separated points.

In the vertical plane, the laser unit or units is/are able to project laser light transversely outwards of the vehicle and also outwards of the ends of the element/bar. The reference line may be extrapolated in the calculating equipment of the arrangement, so as to collect roadway measurement values also transversely outwards of the bar.

By providing an additional vertically orientated laser plane that is parallel with the first laser plane but spaced therefrom at a well defined distance in the length direction of the vehicle, it is possible to achieve the projection of a further laser line on the roadway being measured. The camera sees this additional laser line at a distance above the first projected laser line. This enables two profile measurements to be made at the same time and therewith obtain a good basis for calculating the profile of the roadway in its longitudinal direction. In order to establish a particularly high degree of measuring accuracy, accelerometers for detecting vertical bar movements can be mounted on or in the proximity of the bar, so as to enable length profiles of the roadway to be calculated with good accuracy.

The invention will now be described in more detail by way of example and with reference to the accompanying drawing, in which

Figure 1 is a schematic longitudinal section view of a vehicle equipped with an arrangement according to the present invention, and

Figure 2 is a view taken on the line II-II in Fig. 1.

Shown in Fig. 1 is a vehicle frame or vehicle chassis 10 that stably supports a bar 2 and a CCD - camera 3. The bar 2 extends at right angles to the longitudinal axis of the vehicle 10 and supports a pair of laser units 1, 1; V, 1 ' on each side of the bar. Each pair of laser units 1, 1; 1 ', 1 ' emits laser light in a vertical plane, either as a broad laser light plane or as a laser line that sweeps rapidly in the vertical plane. The pairs of laser units illuminate the roadway 4 with overlapping light planes so as to project a line 11 onto the roadway, said line extending along at least the full length of the bar 2 and preferably also beyond each end of the bar. Although the laser units 1 of respective pairs have a limited fixed angle of laser light, they can, nevertheless, be adjusted angularly in the vertical plane so as to intersect mutually in their main directions and thereby provide a line length 11 that is at least equal to the length of the bar 2.

Correspondingly, the pairs of laser units 1 ' project light in a vertical plane that is parallel with the plane for the unit 1 and therewith projects a line 11 ' onto the roadway 4 at a distance s in front of the line 11 as seen in the direction of movement of the vehicle 10.

It will be seen that the bottom edge of the bar 2 carries a reference line 5, which may consist of light reflecting tape 5 that is illuminated by a light source not shown.

As will be apparent from Fig. 1, the camera 3 is carried on the underside of the vehicle 10 at a relatively long distance t behind the bar 2. The distance t is chosen to ensure that the camera 3 having a factual field angle will be able to observe the line 4, 4' along the whole of its length.

It will also be seen from Fig. 1 that as a result of the distance s between the reference line 5 and respective lines 11, 11 ' the vertical field angle from the camera 3 between the reference line 5 and respective lines 11, 11 ' will be different, therewith enabling both lines to be observed by the camera 3 at the same time. The camera 3 can view a multiple of positions along the line 5 and detect in each such position the reference line 5 and the line 11 respectively and is able to determine the local vertical distance between the line 5 and the line 11 subsequent to calibration or measurement. These distances in said chosen positions along the bar 2 can be registered in a register 7 and therewith define the profile of the roadway 4 on each measuring occasion. The camera 3 is able to measure said distance at a large number of points along the bar 2 generally at one and the same time.

Measuring can also be effected directly between the lines.

The camera 3 may also measure the distance to the line 11 ' at mutually different positions along the bar 2 at one and the same time, so as to enable the slope of the roadway 4 longitudinally between the lines 11, 11 ' to be registered in said selected positions along the bar 2. With regard to the longitudinal inclination of the roadway 4, a still better result can be achieved by mounting accelerometers (not shown) on the bar 2 in a known manner, for instance on the ends of said bar, wherewith the values measured by the accelerometers can be used to calculate the vertical movements of the vehicle, so that said movements can be compensated for when necessary. The measuring result can also be improved with the aid of a gyroscope, by measuring changes in the orientation of the bar 2 in relation to a reference plane, for example the horizontal plane.

Figure 2 shows that the reference line 5 of the bar 2 has a contemplated continuation 6 at each end of the bar 2. This continuation line is an extrapolated extension of the line 5 and can be arrived at as a reference line with a starting point from the straight line 5 as discerned by the camera 3. Thus, the line 6 can be calculated in the devices 7 connected to the camera 3, including appropriate register means 8 for registering the values concerned. As will be apparent from Figs 1 and 2, the transverse profile of a roadway can be measured readily at right angles to the direction in which the vehicle is driven with the aid of very simple equipment comprising a CCD-camera 3, a bar 2 that carries a reference line 5 and at least one laser 1, even when the vehicle is driven at high speed. By projecting a further laser 11 ' onto the roadway 4 parallel with the laser line 11 but at a distance therefrom in the longitudinal direction of the vehicle drive path, this relatively simple equipment can be used also to register the longitudinal profile of said drive path at a large number of points across the width of said path.

It will be understood that several variants are conceivable within the scope of the invention. For example, several cameras can be used side-by-side to measure larger areas in a lateral direction or so that respective cameras will view requisite areas in a lateral direction. A camera that includes a PSD-element may be used instead of a CCD-camera. The reference line can be created with laser light that is projected onto an element. Alternatively, the reference line can be built-up of a series of light points, for instance light emitting diodes, or of small reflectors mounted on the reference element. Another alternative is to use the bottom edge of the reference element/bar as a reference line. The laser line projected onto the road surface may be established by a rapidly sweeping beam from a laser unit, or by fixed beams from one or more laser units. By constructing the lines with the aid of discrete points affords the advantage of enabling the points to be distinguished as measuring points that have a predetermined position. The points will also give a relatively higher degree of brightness.

If only one single camera is used, the reference line on a straight reference element /bar can be given a vertical curvature to compensate for variations between the camera and measuring points. Alternatively, the reference line may be curved in the horizontal plane so that the distance to the camera will be generally constant. Speaking generally, the arrangement can be readily calibrated by providing a horizontal measuring surface, for instance a reflective free-liquid-surface, beneath the reference line, for instance when the line is straight and horizontal, so that it will be known that the vertical distance between the reference line and the road line 11 is constant along the length of the reference line. The vertical angles read-off by the camera or cameras between the measuring surface and the reference surface can then be corrected with adjustments that ensure that the camera output signal will be uniform in different viewing directions in the horizontal plane after said adjustments. The reference element/bar can be resiliently suspended relative to the chassis when movement of the reference element relative to the chassis is calculated or read off continuously so that the net result of the camera can be corrected with reference to movement of the reference element.

Claims

1. An arrangement for measuring the transverse profile of a roadway, wherein the arrangement comprises a laser unit (1, 1) carried by a vehicle (10) which is intended to be driven along said roadway, wherein the laser unit is adapted to illuminate the roadway (4) vertically, and wherein a vehicle-carried sensor (3) is adapted to detect the distance to the roadway illuminated by the laser unit, characterised in that the laser unit is adapted to illuminate the roadway along a line (11) that extends transversely of the vehicle and the roadway, said laser light being directed generally in a vertical plane; in that the vehicle carries a generally horizontally extending reference line (5); in that the sensor (3) includes an electronic camera which is mounted on the vehicle at a longitudinal distance (t) from the laser light plane and which views the laser line (11) projected onto the roadway (4) and also the reference line (5) at one and the same time; and in that the arrangement includes register means

(8) adapted to register the angle detected by the camera between the projected laser line (11) and the reference line (5) at a plurality of positions along the projected laser line (11).

2. An arrangement according to Claim 1, characterised in that the laser unit is adapted to also project said line (11) onto the roadway outwardly of at least one end of the reference line (5).

3. An arrangement according to Claim 1 or 2, characterised in that the arrangement also includes a calculating device (7) that is adapted to extrapolate the reference line detected by the camera as a calculated reference (6) to detection of the camera of the projected laser light line on the roadway in positions outwardly of the ends of said element.

4. An arrangement according to any one of Claims 1 - 3, characterised in that the reference line (5) is an illuminated reflective structure on a vehicle-carried reference element (2).

5. An arrangement according to any one of Claims 1 - 3, characterised in that the reference line (5) is laser light line projected onto a vehicle-carried reference element (2).

6. An arrangement according to Claims 1 - 3, characterised in that the reference line (5) is a structural edge of a vehicle-carried reference element (2).

7. An arrangement according to any one of Claims 1 - 6, characterised in that the laser unit (1 , 1 : 1 ' 1 ') is adapted to illuminate the roadway along a further line (11 ') which is generally parallel with the first mentioned line (11) and spaced therefrom through a distance (s) in the longitudinal direction of the vehicle, said further line (11 ') also being established with the aid of laser light that spreads in the vertical plane; and in that the calculating device (7) is adapted to evaluate the longitudinal profile of the roadway on the basis of the simultaneous measuring result of the laser line associated transverse profiles at a series of positions along said laser lines.

8. An arrangement according to any one of Claims 1 - 7, characterised in that the reference line (5) is located on a vehicle-carried bar (2) which extends transversely of the vehicle; in that the bar (2) and the camera (3) are coupled rigidly to the frame or chassis (10) of the vehicle; and in that the bar carries said laser unit.

9. An arrangement according to Claim 7 or 8, characterised by accelerometers coupled to the ends of the bar (2) for evaluation of any vertical movement of the bar (2) between mutually sequential transverse profile registrations, so as to achieve improved evaluation of the longitudinal profile of said roadway.

10. An arrangement according to any one of Claims 4 - 9, characterised in that the reference element (2) has discrete camera discernible markings spaced along its length.

11. An arrangement according to any one of Claims 1 - 10, characterised in that two or more cameras are placed side-by-side and adapted to view transversely separated longitudinal sections of the reference line and the laser light line.

2. An arrangement according to any one of Claims 1 - 11, characterised in that the reference line and or the laser light line are formed by a series of mutually separate points along said line.