GB2382939A - Mesurement of surface shape - Google Patents

Mesurement of surface shape Download PDF

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Publication number
GB2382939A
GB2382939A GB0122083A GB0122083A GB2382939A GB 2382939 A GB2382939 A GB 2382939A GB 0122083 A GB0122083 A GB 0122083A GB 0122083 A GB0122083 A GB 0122083A GB 2382939 A GB2382939 A GB 2382939A
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GB
United Kingdom
Prior art keywords
theodolite
measurement
automatic
road
instrument
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0122083A
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GB0122083D0 (en
Inventor
Barry James Gorham
Original Assignee
Barry James Gorham
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Barry James Gorham filed Critical Barry James Gorham
Priority to GB0122083A priority Critical patent/GB2382939A/en
Publication of GB0122083D0 publication Critical patent/GB0122083D0/en
Publication of GB2382939A publication Critical patent/GB2382939A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • EFIXED CONSTRUCTIONS
    • E01CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01CCONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
    • E01C19/00Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
    • E01C19/004Devices for guiding or controlling the machines along a predetermined path
    • EFIXED CONSTRUCTIONS
    • E01CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01CCONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
    • E01C19/00Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
    • E01C19/004Devices for guiding or controlling the machines along a predetermined path
    • E01C19/006Devices for guiding or controlling the machines along a predetermined path by laser or ultrasound
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01CMEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C15/00Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
    • G01C15/002Active optical surveying means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06Systems determining position data of a target
    • G01S17/42Simultaneous measurement of distance and other co-ordinates
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/16Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves
    • G01S5/163Determination of attitude

Abstract

This invention is directed towards civil engineering applications such as road paving and tunnel walls surveying. The system proposed comprises two instruments, a theodolite and a scanning range-finder, which are rigidly connected together within a fixed frame, one or more field beacons (targets) and means for computing the shape of a local surface from fusion of the measurements data from the two instruments. One embodiment of the invention refers to the process of road paving (Fig. 1). Here, an automatic 'V' beam scanning laser theodolite combined with a downward facing, angularly scanning, pulsed laser-range-finder is fitted to the frame of a road paver such that the profile of the road surface immediately behind the screed is continuously measured. The spatial data of the profile is referenced through the automatic 6-D fixation of the theodolite by spatial resection from the pre-surveyed field beacons.

Description

<Desc/Clms Page number 1>

Apparatus for the measurement of surface shape This invention relates to apparatus for the measurement of surface shape. It is concerned mainly, but not exclusively, with the measurement of road surfaces and of tunnel walls.

One purpose of the invention is to provide full spatial data for a surface in terms of the local survey reference frame both automatically and effectively in real-time.

According to the invention there is provided: a first instrument comprising a theodolite able to measure directions in azimuth and elevation to a plurality of targets disposed in its local environment ; at least one target designed to be observed from the theodolite for the purpose of direction measurement; a second instrument capable of determining the linear distance from an internal <img class="EMIRef" id="024168793-00010001" />

reference point to a plurality of points on the surface whose shape is to be measured ; p 3 means for rigidly attaching the two instruments together such that the relative positions of the respective internal reference points of measurement and the relative orientation of the two sets of measurement axes are known and maintained ; means for computing the shape of the surface through processing of the directional data from the theodolite in combination with the range data from the distance measuring instrument.

Modem road pavers are capable of responding to spatial data provided by a suitable guidance system to the following accuracy; +/-50 mm in X and Y, +/-5 mm in Z, +/- 0. 05 in pitch and roll, and +/-0. 1 in heading. Currently, no system can reliably provide this accuracy for the paver screed position in real-time.

A current system of guidance available for pavers is provided by the GPS satellites. By this means, real-time 3-D position information is generated for each satellite receiver mounted on the paver. The use of a pair of receivers, say one forward left and the other rear and right, enables the roll, pitch and heading parameters to be determined. However, use of such a system has a number of significant drawbacks in addition to the significant high cost of multiple receivers plus a Base Station. The most significant of these is dependence of the system on the field of view of its receivers and this seldom can be

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guaranteed without interruption during a day's operations. In some circumstances that prevail, in Scandinavian countries for instance, where a roadway is to be constructed through forests or in cuttings, the satellite receivers are unable to detect sufficient satellites to obtain a fix over periods of several hours. Guidance is left in that event to older more traditional methods.

In addition to shadow zones where insufficient signals are received, multi-path errors can be significant in the environment of a work-site. These effects allow measurements data to be produced but the noise factor associated with the position data can become unacceptably high Furthermore, and following a loss of lock between an individual mobile receiver and the Base Station, there can be a significant delay in restoring the full communication ability of the system. This is particularly relevant to operation of a paver which cannot pause whilst guidance information is interrupted.

Practical accuracy quoted for 3-D co-ordinates from a GPS receiver in this dynamic <img class="EMIRef" id="024168793-00020001" />

mode are between +/-5 and +/-10 mm for both X and Y, and between +/-20 and +/-30 mm in the Z parameter (height)-well short of the requirements of the new control systems for paving.

The other main commercial system available for automatic guidance of a paver is a Robotic Total Station (RTS). This instrument integrates the functions of a theodolite with an electronic distance meter and is operated under automatic control. It will sweep the horizon until it finds a suitable target and then proceeds to measure the vector, instrument-target, in order to generate target co-ordinates. The attainable dynamic accuracy of the respective commercial systems are very similar. They are generally equivalent to a standard error in direction of +/-5 arc seconds, and in distance measured, to +/-6 mm.

The only mode of use for RTS instruments in vehicle guidance so far reported is that where the instrument is established in a fixed position at the rear and to one side of the vehicle. The measurements are automatically undertaken to a single target prism rigidly fixed to part of the vehicle chassis, or in the case of a road paver, to part of the'screed'.

With an update rate for the measurements of less than one second, the dynamic accuracy requirements in respect off, Y and Z for any normal site vehicle control is easily met.

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However, there are two significant limitations in using a RTS for guiding road pavers.

The first is that since measures are made to but a single target, there is no externally generated information on the tilts of the screed (roll, pitch and heading). To obtain these, it is necessary to integrate a number of additional sensors into the fabric of the paver and to combine their outputs with that of the RTS, usually provided by a remote radio link.

The second limitation arises through the geometrical disposition of the RTS instrument with respect to the paver. It is usually sited in a fixed position to the rear of the paving machine and to one side of the newly paved road. The critical measure of screed height deteriorates as the distance between paver and RTS increases. Once this separation reaches some two or three hundred metres, it is necessary to re-site and to re-initialise the RTS instrument with the consequent loss of guidance information for the paver. The only reliable solution to this is to use two RTS instruments, one forward looking and the other facing the rear of the paver, and to pass over guidance control at the required times. This adds significantly to both system complexity and to cost.

A system, comprising a mobile instrument and a number of field targets, which has been demonstrated to generate real-time guidance for a paver with the required maximum usable accuracy is LASERGUIDE. This represented a radical departure from the approach of other guidance systems in that instead of the position and attitude of the paver screed being monitored, the new road surface created behind the paver was measured so that it could be compared with that of the theoretical design surface of the road.

The instrument of LASERGUIDE is based on an automatic laser theodolite which formed the subject of UK Patent GB 2090096B. The essential features of the theodolite, which are significant to this present invention, are as follows. The theodolite operates by continuous scanning of a compound laser beam comprising a pair of mutually inclined fans. The rotation of the beam is monitored internally by a single electronic angle encoder. When either of the fan beam components strikes an electronic or passive retroreflecting target, the instantaneous reading of the encoder is latched and recorded. At the completion of every full 360 sweep, the pairs of encoder readings corresponding to each

<Desc/Clms Page number 4>

target in the instruments field of view are used to compute its respective full spatial direction vector There is almost no limit to the number of targets whose directions can be measured per sweep of the laser beams. For site vehicle guidance, the sweep rate is 1 or 2 Hz, and for short-range position monitoring, it can be increased to some 30 Hz. The repeatable pointing accuracy per target is between 1 and 2 arc seconds for ranges up to 100 metres in good optical sight conditions, and in this respect, compares favourably with current performance of commercial RTS instruments.

In the application of road-paver guidance, a theodolite of this design was mounted on a trolley towed immediately behind the paver. An array of pre-surveyed points along the sides of the road trajectory were occupied each by an identical beacon (target), which used the azimuth scanning beams from the theodolite to maintain their pointing toward it. This guaranteed that when the beacons were struck by any arm of the'V'beam, and they emitted their transponding short optical pulses, these would be received by the theodolite.

By a process of spatial resection, the instrument was able to determine its own 6-D coordinates (XYZ, roll, pitch and heading) from vectors measured to any three beacon stations whose XYZ co-ordinates were known in the system co-ordinate reference frame.

Thus from a knowledge of the relative positions of the effective geometrical measurement centre of the instrument and of the points of contact of the trolley wheels with the road surface, and of the relative orientation of the instrument axes and trolley frame, it was possible to generate position co-ordinates for the road surface at the wheel points, and hence deduce the shape of the road surface.

Although offering significant improvements to the paver guidance process over other commercial systems, LASERGUIDE does suffer from two practical drawbacks that directly affect its maintenance of accuracy. The first arises through the dependence of performance on the geometrical stability of the mounting of the instrument on the trolley frame. More specifically, in maintaining during operation the orientation of the instrument internal axes of measurement to less than one arc minute with respect to the plane defined by the lower edges of the trolley wheels in contact with the road.

<Desc/Clms Page number 5>

The second drawback arises through uneven sinking of the trolley wheels in the newly laid, and uncompacted, road surface.

It is an aim of the present invention to overcome both of these practical limitations. It is accepted that, during the paving process, the instrument will relax in its mount on the paver. The relationship therefore between the instrument axes and the underlying road surface will then be unknown and different from those prevailing at the start. The link of information between position of the underlying road profile and the position and orientation of the theodolite instrument on the paver is now provided by some form of scanning range-finder. The paver now becomes merely a carrier of the road profiler system, and a knowledge of the geometry of its mounting with respect to the mechanical axes of the paver is no longer required. The feedback information to the driver of the paver on the geometrical properties of the new road surface being laid will still enable suitable corrections of heading or screed tilts and height to be made, either manually or by automatic control.

Having divorced the spatial measurement system from the vehicle which carries it, the system may now be carried by any form of motor vehicle and used to survey road surfaces, both before and after paving. This may be applied also to a quality assessment of the state of a road surface for estimating any necessary road repairs. In similar fashion, the central axis of measurement for the scanning range-finder may be set approximately horizontal so as to provide spatial data through a series of profiles of a wall surface to the side of the vehicle. When set vertically upwards, a ceiling or roof profile may be obtained. Thus, in addition to measurements made on road surfaces, the system may, without modification, equally be applied to the surveying of existing road or rail tunnels.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which :- Figure 1 shows in schematic form operation of a road paving machine provided with apparatus constructed according to the invention.

Figure 2 represents a form of the measurement system according to the invention wherein the two instrument components are integrated into a single housing.

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Figure 3 illustrates the main features of a laser pulsed range-finder which could constitute the second instrument integrated into the measurement system according to the invention.

In Fig. 1 a paving machine has mounted on its frame an instrument'I'which contains a theodolite which preferably, but not necessarily, is of a type that operates automatically by continuous scanning of a'V'shaped laser beam. Also contained within the housing of the instrument'I'is a downward-facing range-finder producing a beam which continuously scans across the section of road surface immediately behind the screed of the paver. The range-finder is preferably one which operates through the timed emissions of narrow laser pulses, but may be based on acoustic radiation rather than electromagnetic. The other main component on the paver is a system computer (not shown) which processes the measurements data.

Direction measures made by the theodolite to at least three of the field targets, each of known 3-D co-ordinates, provide 6-D spatial information for the theodolite, XYZ, pitch, roll and heading. The range-finder beam scans across the road profile immediately behind the paver screed and generates both range and corresponding direction values normal to the negative Y-axis (main axis direction for the road) of the theodolite instrument. Each end-point of the beam defined by internal range and direction is ascribed'local'co-ordinates, that is, local to the internal axes of the range-finder. The system computer then converts these to global site co-ordinates through transformations determined from the known and fixed geometry that exists between the measurement frames of the individual theodolite and range-finder instruments.

A redundancy of field beacons would be provided in practice and, as the paver moves forward and its range from the rear beacons becomes extended, these would be moved forward, perhaps in pairs, to fresh pre-surveyed positions. By applying Kalman filtering to the measurements data, updates of the temporarily absent information for the theodolite while the beacons are being moved, may be maintained without significant loss of accuracy.

Fig. 2 shows a schematic of the axial relationship between the theodolite unit'L' (with its scanning fan laser beams), the scan direction of the range-finder'R'and the road axis.

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The instrument mount'M'is preferably such that the effects of vibration from the paver are minimise.

The main components of a design of laser pulsed range-finder, suitable for use in the present invention, are shown in Fig. 3. Here, the laser source'R'provides a linear beam in a direction'D'. This is intercepted by a prism mirror'P', which is rotatable about the primary axis of the laser beam so as to produce the required scan. The beam direction within the arc of the scan (normally set to the width of the paver screed) is continuously monitored by use of an electronic angle encoder'E'. The encoder output is latched each time a range measure is made by the beam so as to produce a set of vectors with end points at the surface of the road.

Claims (6)

1. Apparatus for the automatic measurement of surface shape comprising, an automatic theodolite instrument capable of measuring directions in azimuth and elevation to a plurality of targets disposed in its local environment; at least one target designed to be observed by the theodolite for the purpose of direction measurement; a continuously scanning automatic distance measuring instrument, which determines the linear distance from an internal reference point to each of a plurality of points on the surface whose shape is to be measured; means for rigidly connecting the two instruments together such that the relative positions of the respective internal reference points of measurement and the relative orientation of the two sets of measurement axes are maintained ; means for computing the shape of the surface through processing of the directional data from the theodolite in combination with the range data from the distance measuring instrument.
2. Apparatus according to Claim 1 wherein the theodolite instrument emits a compound beam of light having an'X'or'V shape in cross-section and which is continuously scanning in its azimuth.
3. Apparatus according to Claim 1 or Claim 2 wherein the target is designed to automatically track and maintain its pointing towards the theodolite.
4. Apparatus according to any preceding claim wherein the scanning distance measuring instrument uses pulsed laser radiation in the measurement process.
5. Apparatus according to Claims 1, 2 or 3 wherein the scanning distance measuring instrument uses acoustic radiation in the measurement process.
6. Apparatus for the automatic measurement of surface shape substantially as described herein with reference to the accompanying drawings.
GB0122083A 2001-09-13 2001-09-13 Mesurement of surface shape Withdrawn GB2382939A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0122083A GB2382939A (en) 2001-09-13 2001-09-13 Mesurement of surface shape

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0122083A GB2382939A (en) 2001-09-13 2001-09-13 Mesurement of surface shape

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GB0122083D0 GB0122083D0 (en) 2001-10-31
GB2382939A true GB2382939A (en) 2003-06-11

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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2090096A (en) * 1979-10-16 1982-06-30 Nat Res Dev Method and Apparatus for Determining Position
GB2151872A (en) * 1983-12-23 1985-07-24 Honda Motor Co Ltd Detecting road surface condtion
EP0215948A1 (en) * 1984-06-05 1987-04-01 Kokusai Kogyo Co. Ltd. Vehicle for evaluating properties of road surfaces
WO1990012282A1 (en) * 1989-04-06 1990-10-18 Geotronics Ab An arrangement for establishing or defining the position of a measuring point
GB2264184A (en) * 1992-01-12 1993-08-18 Israel State Large area movement robots
GB2308256A (en) * 1995-05-02 1997-06-18 Tokimec Inc Road surface profilometer
WO1998008112A1 (en) * 1996-08-22 1998-02-26 Synthes Ag Chur 3d ultrasound recording device
WO2000063719A1 (en) * 1999-04-20 2000-10-26 Synthes Ag Chur Device for the percutaneous obtainment of 3d-coordinates on the surface of a human or animal organ
GB2360891A (en) * 1998-10-21 2001-10-03 Omron Tateisi Electronics Co Mine detector and inspection apparatus
GB2369511A (en) * 2000-11-17 2002-05-29 Samsung Kwangju Electronics Co Mobile robot location and control

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2090096A (en) * 1979-10-16 1982-06-30 Nat Res Dev Method and Apparatus for Determining Position
GB2151872A (en) * 1983-12-23 1985-07-24 Honda Motor Co Ltd Detecting road surface condtion
EP0215948A1 (en) * 1984-06-05 1987-04-01 Kokusai Kogyo Co. Ltd. Vehicle for evaluating properties of road surfaces
WO1990012282A1 (en) * 1989-04-06 1990-10-18 Geotronics Ab An arrangement for establishing or defining the position of a measuring point
GB2264184A (en) * 1992-01-12 1993-08-18 Israel State Large area movement robots
GB2308256A (en) * 1995-05-02 1997-06-18 Tokimec Inc Road surface profilometer
WO1998008112A1 (en) * 1996-08-22 1998-02-26 Synthes Ag Chur 3d ultrasound recording device
GB2360891A (en) * 1998-10-21 2001-10-03 Omron Tateisi Electronics Co Mine detector and inspection apparatus
WO2000063719A1 (en) * 1999-04-20 2000-10-26 Synthes Ag Chur Device for the percutaneous obtainment of 3d-coordinates on the surface of a human or animal organ
GB2369511A (en) * 2000-11-17 2002-05-29 Samsung Kwangju Electronics Co Mobile robot location and control

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Publication number Publication date
GB0122083D0 (en) 2001-10-31

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