The Computer Integrated Road Construction project - CiteSeerX

Automation in Construction 9 Ž2000. 447–461 www.elsevier.comrlocaterautcon

The Computer Integrated Road Construction project F. Peyret a,) , J. Jurasz b,1, A. Carrel c,2 , E. Zekri c,2 , B. Gorham d,3 a

Laboratoire Central des Ponts et Chaussees, ´ Section Robotique de Chantier (SRC), Centre de Nantes, B.P. 19, 44340 Bouguenais, France b UniÕersity of Karlsruhe, IMB, Am Fasanengarten, 76128 Karlsruhe, Germany c Cap Gemini DiÕision ITMI, 61 Chemin du Vieux Chene, ˆ BP 177, 38 244 Meylan Cedex, France d UniÕersity of East London, Longbridge Road, Dagenham, RM8 2AS Essex, UK

Abstract This paper is about the ‘‘Computer Integrated Road Construction’’ ŽCIRC. project, which is a Brite-EuRam III funded project, lasting 1997–1999, aiming at introducing a new generation of control and monitoring tools for road pavements construction. These new tools are designed to bring on the sites significant improvements by creating a digital link between design office and job site. The first part of the paper describes the background of the project, which gathers seven European partners from five different countries, and gives the objectives of the project, in general and for each of the two targeted products: one for the compactors ŽCIRCOM. and one for the asphalt pavers ŽCIRPAV.. Then, the two prototypes are described, each of them being broken down into three main sub-systems: the ground sub-system ŽGSS., the on-board sub-system ŽOB. and the positioning sub-system ŽPOS.. The expected benefits for the different users are also presented and quantified. The central part of the paper is devoted to the main technical innovations that have been developed in the frame of the project: universal vector database for road equipment guidance, multi-machine functionalities of CIRCOM and the two positioning systems which are actually the technological keys of the systems. Finally, the state of progress of the developments of the two CIRC products and the first commercial success achieved in parallel are presented. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Road construction; CIRCOM; CIRPAV

1. Background

) Corresponding author. Tel.: q33-2-40-84-59-40; fax: q33-240-84-59-92. E-mail addresses: [email protected] ŽF. Peyret., [email protected] ŽJ. Jurasz., [email protected] ŽA. Carrel., [email protected] ŽE. Zekri., [email protected] ŽB. Gorham.. 1 Tel.: q49-721-608-38-84; fax: q49-721-69-52-45. 2 Tel.: q33-4-76-41-40-00; fax: q33-4-76-41-28-05. 3 Tel.: q44-208-223-2513; fax: q44-208-223-2840.

The ‘‘Computer Integrated Road Construction’’ ŽCIRC. project, No. BE-96-3039, is supported by the European Commission, under the Industrial and Materials Technologies Programme Brite-EuRam III, from the fourth Framework Programme. It aims at demonstrating the interest of new tools, based upon the application of state-of-the-art information technologies to road construction sites.

0926-5805r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 6 - 5 8 0 5 Ž 0 0 . 0 0 0 5 7 - 1

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F. Peyret et al.r Automation in Construction 9 (2000) 447–461

Seven partners are involved in the project, each providing complementary skills and abilities: Ø ITMI division of CAP GEMINI France, main activity: information systems, project role: Coordinator, Prime contractor, developer and integrator of positioning systems. Ø The Laboratoire Central des Ponts et Chaussees ´ ŽLCPC., France, main activity: engineering expertise and research within the field of civil engineering, project role: project initiator, trials and project consulting. Ø TEKLA OY, Finland, main activity: geographical information systems, project role: development of mission planning and control system, development of interface to Computer Aided Design ŽCAD. system. Ø Institut fur ¨ Maschinenwesen im Baubetrieb ŽIMB., University of Karlsruhe, Germany, main activity: construction machines and management, automation in building and civil engineering works, project role: development of on-board control systems. Ø University of East London ŽUEL., Great Britain, main activity: metrology, project role: development of the laser-based positioning system. Ø EUROVIA, France, main activity: road and motorway construction, project role: requirements specifications, experimental work-sites. Ø National Land Survey ŽNLS., Sweden, main activity: geography and geodesy research and expertise, project role: work-site surveying consultant. Alongside this consortium, an End-Users’ Club has been created. Its role is to participate in the specifications of requirements and to facilitate the integration of CIRC products into the European market. Major companies of the road building world are members of this club, which represents over 50% of the European equipment manufacturing ŽSvedala, ABG. and over 30% of the European road construction ŽEurovia, Colas, Dragados y Contruccion.. 2. Objectives 2.1. General objectiÕe of CIRC The paradigm of ‘‘Computer Integrated Construction’’ ŽCIC. aims at providing a new methodology,

based upon the sharing of a common numerical geometrical data base from the design, through all the site operations up to the quality control of the geometry of the structure w1,11x. It relies upon the main following technologies: CAD software tools, automatic control, short-range wireless data communication and particularly, the key technology that was the latest to be developed: real-time positioning w4x. The CIRC project aims to develop CIC systems for the real-time control and monitoring of the work performed by road construction equipment, to be integrated, in a first step, into road construction machines like compactors or asphalt pavers. 2.2. Functional objectiÕes of CIRCOM After the spreading of an asphalt course by an asphalt paver, the material needs to be compacted while it is still hot to reach its final degree of compaction and its specified properties. This work is achieved by ‘‘compactors’’ or ‘‘rollers’’. It is essential that the right level of energy should be transmitted to the material, with a uniform distribution w5x. This energy, as far as the settings of the compactor do not vary, depends directly from the number of runs, or passes, of the machine. So, the first and main objective of CIRCOM is to assist the driver in this task, so that he can perform the exact number of passes, at the right speed, everywhere on the surface to be compacted. This assistance is based upon an ergonomic man–machine interface ŽMMI., where simple graphical data and information are displayed to the operator. To perform this task, it is essential to provide the system with an accurate and continuous localisation of the machine. ‘‘Accurate’’ in this case means 10 cm in both transversal and longitudinal directions, ‘‘continuous’’ means that it should work everywhere on the site, whatever the environment Žin very constraining environments, a temporary degradation of the positioning accuracy up to 20 cm is authorised.. When installed on several machines Žgenerally, two to four compactors work together on big sites., CIRCOM, in its multi-compactors version, has to manage the data base globally for all the machines. The second objective of CIRCOM is to record the actual work achieved by the roller, in terms of


trajectory followed and number of passes achieved on every point of the trajectory, in order to feed the site data base and to perform a global quality control at the site level. 2.3. Functional objectiÕes of CIRPAV In Europe, most of the pavement courses are laid by pieces of equipment called asphalt ‘‘pavers’’ or ‘‘finishers’’ Žsee Fig. 1.. This machine moves very slowly Žsome meters per minute., always forward, but has to spread a very smooth and precisely levelled layer of material. The level is directly set by the position of the tool Ža so-called ‘‘floating screed’’ attached to the tractor at two articulations called tow-points by the intermediate of two levelling arms.. The high accuracy in terms of level comes from the contractual tolerances in level and cross-slopes generally required for the upper layers of the pavement, typically "3 cm for the sub-base, "2 cm for the base, "1.5 cm for the binder course and "1 cm for the wearing course. Absolute control in elevation is essential for the spreading of the sub-base Žsometimes base. layer, in order to respect the altitudes and cross-slopes prescribed by the design. This control is currently performed by using string lines Žalso called wire ropes. installed along the road and mechanical deviation sensors. These wires are expensive to install, dangerous for the workers and generate problems for site truck traffic w2x. So, two main functions will be ensured by CIRPAV, from the machine operation point of view: Ø the assistance of the driver in his task of maintaining the paver on its correct trajectory at the right speed,

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Ø the assistance of the screed-man in his task of controlling accurately the position and cross-slope of the screed either automatically or manually. For these two goals, CIRPAV will provide all the position and attitude information of the tractor and of the screed which are necessary, with the respective accuracy required, that is to say "5 cm in both transversal and longitudinal directions, and "1 cm for the height component. The third main objective of CIRPAV, from the site manager’s point of view, is to record the actual work achieved by the paver, in order to feed the site data base and to perform a global quality control at the site level. 2.4. Benefits of CIRC products The main expected economic gains brought by CIRC products are at four levels: Ø saving of tedious labour cost Žan analysis made by EUROVIA showed that an 80 kEuro CIRPAV could be paid off thanks to this saving on a single 30-km-long highway work site., Ø saving of equipment use Žit was calculated that two CIRCOM, of 62 kEuro each, could be paid off by this saving on two 30-km-long highway work sites., Ø saving of material Žaround 3500 Eurosrkm on a 2 = 2 way highway pavement site., Ø improvement of quality Žsuppression of supplementary costs for repairing low-quality works..

3. Deliverables The main deliverables of the project are the two CIRCOM and CIRPAV prototypes. Each of them is broken down into three sub-systems Žsee Fig. 2.: ground sub-system ŽGSS., positioning sub-system ŽPOS., on-board sub-system ŽOB.. 3.1. CIRCOM prototype

Fig. 1. Schematic description of the asphalt paver.

This prototype has been already described in Refs. w9,10x.

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Fig. 2. Global architecture of CIRCOM.

3.1.1. Ground sub-system The role of the CIRCOM GSS, or «ground station», is two-fold: Ø to prepare the mission of the compactors Žin order to provide them geometric data about the worksite, coming from CAD data, as well as guidelines for operation., Ø after the mission is achieved, to compute compacting results and prepare statistics on the work achieved. This task is performed by a specialised software running on a standard office PC, which is used by the supervisor of the work-site. The core of this software package is common to CIRCOM and CIRPAV. The most innovative feature of it is the structure of the data base itself which is 3D, meaning that all the elements of the project, as well as the trajectories, are stored as 3D polylines in a vector data base. An example of GSS’s window is given in Fig. 3. The ground station is used at several stages of the road project: Ž1. feeding of the database of the ground station with the project data Žin this purpose, CIRC offers compatibility with the output format of the most commonly used road design systems., Ž2. each working day, preparation of the mission for each compactor of the fleet, using the user-friendly graphical interface Žchoice of a compactor, of the layer to be compacted, definition of the area concerned by the mission and of the compaction values to apply to this area: number of passes and speed.,

Ž3. at the end of the day, updating of the work-site database with the results of the day Žthe compaction map shows the compacted areas, coded with the user-defined colours for different counts of passes — see Fig. 3.. 3.1.2. Positioning sub-system The role of the POS is to locate precisely and in real-time the compactor by using state-of-the-art Global Positioning System ŽGPS. technology, in real-time kinematic ŽRTK. mode, as well as deadreckoning sensors ŽDoppler radar, encoder and fibre-optical gyrometer.. To get the best from the instruments, an extended Kalman filter has been designed, running at the rate of 25 Hz. This sub-system will be described more in details in Section 4.3. 3.1.3. On-board sub-system The role of the OB embedded on the compactor is to: Ø manage a MMI, which assists the driver in compacting Žcf. Fig. 4., Ø process and memorise instruction data, position data, work done, Ø exchange achieved work data with other compactors working on the same section. These tasks are performed by robust, industrial PC equipped with high brightness colour LCD screen, PCMCIA removable media and reduced keyboard. The achieved work data can be exchanged using one


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Fig. 3. The CIRCOM GSS MMI: map of compaction passes.

of two technologies: radio modems and WaveLANs, depending on the choice of the user.

Specific features of the on-board subsystem internal architecture, namely the vector database and data

Fig. 4. CIRCOM OB main MMI.

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exchange principle, will be discussed in greater depth in Section 4.1 and 4.2. 3.2. CIRPAV prototype 3.2.1. Ground sub-system As for CIRCOM, the role of the CIRPAV GSS is to: Ø provide the paver with geometric data about the work-site, coming from CAD data, as well as guidelines for operation, Ø compute paving results and prepare statistics on the work achieved. This task is performed by a specialised software, which is an extension of the CIRCOM ground station software. In order to prepare the asphalt-paving mission, the user chooses a paver Žand its associated parameters. and defines one or several trajectories. In order to visualise the paving work results, there are three views the user can adopt: the map Õiew shows the differences between the achieved surface and planned surface, the cross-section Õiew shows

the cross-section of the target and achieved surface, at a selected section of the road, and the profile Õiew shows the profile along the road of the target surface and the achieved surface, with a selected offset from the axis. The user can also ask the system to produce statistical results, such as altimetry listings and paver’ speed diagrams. 3.2.2. Positioning sub-system The role of the POS is to locate precisely and in real-time the paver and to get the exact geometrical description of the layer currently being spread. For that purpose, different sub-systems are currently developed and studied, in order to provide the best possible solution, with regards to the specific constraints of the paving site. Mainly two technologies are addressed: Ži. a novel 6D laser-based technology, capable of generating continuously and automatically sets of six spatial co-ordinates Ž «LaserGuide» system from University of East London w3x., with an excellent accuracy in terms of elevation and attitude angles, Žii. the RTK-GPS technology, as for CIRCOM, combined with inclinometer measurements,

Fig. 5. CIRPAV OB MMI.


for paving works less demanding in terms of elevation accuracy. Clearly, the second solution should provide a more automated and industrial solution, thanks to the global aspect of GPS, which brings both spatial coherency and temporal coherency w11x. However, the best accuracy in elevation that it is possible to achieve with a state-of-the-art RTK receiver, under usual site conditions, is "2 cm w8x and this does not meet the requirements for most pavement layers. Furthermore, there are still availability problems with GPS in some environments due to the masking of the satellites signals. Consequently, despite the research efforts in this domain and some encouraging results w6x, the first positioning system to be integrated on CIRPAV is the LaserGuide. This instrument will be described in more detail in Section 4.4. 3.2.3. On-board sub-system The role of the OB, embedded on the paver is to: Ø automatically control the height and the cross slope of the screed Žif the operator chooses the ‘‘automatic control’’ mode., Ø manage two MMI Žsee Fig. 5. which assist the driver and the screed-man in their work, Ø process and memorise instruction data, position data, work achieved. The CIRPAV MMI follows similar principles to that of CIRCOM, but has more functions. Three graphic presentations: work site map, screed view and trajectory display support the driver and screedman in following the 3D trajectory designed for the machine and its tool as well as providing an overview of the achieved and scheduled work. The overview map and curvilinear co-ordinates display help the machine operators to maintain correct orientation on the work site. The colour map of levelling errors and digital displays of screed position give direct visual feedback in manual control mode and provide additional safety checks in the automatic mode.

4. Main technical developments The CIRC products possess some advanced features which could not have been implemented with-

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out several innovative developments. In this paper will be described more particularly: Ø the universal vector database for road machine guidance, Ø the multi-machine functionalities of CIRCOM, Ø the positioning system of CIRCOM, Ø the positioning system of CIRPAV.

4.1. The uniÕersal Õector database for road machine guidance The digital objects of the road construction site, mostly surfaces and polylines Žseries of segments., lie usually along one curve. In other words, in curvilinear representation, there is always a good choice for a dominant axis. That is why special ways of representing road objects are needed, as compared to methods applied in all-purpose CAD and CAM systems. Information systems specialised towards road machine guidance have to deal with several kinds of objects, for example lines and surfaces describing designed road, trajectory of machine tool, actual road surface and additional objects like surveyor monuments, bridges or orientation signs. These items do not necessarily need to be stored as geometrical objects, but most of them can be straightforwardly modelled by smooth 2 or 3D curves, for example polylines, clothoids and parabolas. Considering these circumstances, it has been decided to develop a uniform road model for CIRCOM and CIRPAV on-board subsystems. The main objectives of its design were: exact and fast visualisation, object paradigm, universality and robustness. To meet these needs, a unique approach, called a ‘‘ribbon database’’, has been created. As the smooth curves and surfaces of the road can be well approximated by multiple piecewise-linear structures, a concatenation of quadrilaterals, called ribbon can be used to effectively describe the road features. Ribbon can also be viewed as a polyline with a width, which is oriented in 3D space. This width can be a non-zero constant for ribbon describing the surface treated by the machine, variable for road surface ribbon and zero for line ribbons. The vertices of the polyline are called ribbon nodes. It is optional

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for the nodes to have various attributes, for example time or speed. For the sake of universality, the 3D approach has been used uniformly, also for an apparently 2D CIRCOM system. In Fig. 6, three different kinds of ribbons, used in the CIRCOM application: two null-width ribbons describing road axis and edge, and one ‘‘thick’’ ribbon describing the trace of the compactor’s drum on the road surface, are represented. 4.2. The multi-machine functionalities of CIRCOM 4.2.1. Requirements The multi-machine extension of CIRCOM Žcalled hereafter Multi-CIRCOM. had to meet several stringent requirements. It should allow reliable exchange of work achieved data among 3 . . . 6 mobile stations, at distances of up to 1000 m from each other, each of the stations should be able to present at any time the work performed by its own machine and the whole fleet, the system has to be resistant to difficult conditions of the work site, etc. Two scenarios must be accounted for: continuous exchange of information during the work Žnormal operation. and ‘‘resume mode’’ Žrapid import of relevant information by the machine entering the work site.. In the normal mode, the system should be able to deal with transmission errors and out of range conditions, as well as congestion arising when too many stations want to transmit concurrently, or available band width is low. After resume, it is not realistic to attempt transferring the data gathered during the whole day of work immediately, possibly

Fig. 6. Three sample ribbons.

blocking the medium for the normal traffic. Rather, only the most relevant data should be sent promptly, the rest may then be transferred at lower priority, concurrently with normal mode data. Finally, the architecture should be kept as independent as possible from the actual communication device type and opened for future technology improvements. To fulfil the requirements, several interconnected design decisions had to be made for system architecture, communication technology, devices and their interfaces. 4.2.2. Architecture The major architectural choice was between the ‘‘Client–Server’’ Žalso known as ‘‘Master–Slave’’. design with single main database on one of the machines Žor at the paver system., and ‘‘Peer-toPeer’’ one, where all stations are equal and each one gathers information about all the others on its own. The Client–Server approach is conceptually simpler, but it fails easily if the master compactor system is switched off or malfunctioning. It requires much more band width than the direct connection, because it does not take advantage of broadcast nature of the ether medium: each incoming position has to be first sent to the server, then propagated to the other machines. On the other hand, the Peer-to-Peer solution requires that each of the machines carries the same information, thus multiplying the memory requirements of the system. However, the other machines need anyhow a local copy of the master database to present the results, so this comes at no additional cost and the Peer-to-Peer solution was eventually chosen. 4.2.3. Broadcast scheme Thanks to such distributed storage, the data are more secure, moreover, it is enough if only one station exchanges information with the office. Provided that all stations lie in the range of the transmitter and can receive the message without errors, each position has to be sent only once, thus saving the band width. The acknowledgement of successful delivery should not be used: it leads to ‘‘implosion’’ of positive answers in the case of error-free transmission. If errors occur and some information is miss-


ing, a re-send request has to be issued and answered by the station possessing the required information. Such a broadcast scheme exploits fully the character of the medium: the cost of transmitting a byte is the same, regardless if it is sent to one station or all of them, therefore, it has been chosen for implementation Žcf. Fig. 7.. 4.2.4. Communication protocol This required the devices and interfaces which supported broadcast or, better yet, multicast Žselective broadcast. transmission. One of such interfaces is TCPrIP, commonly used Internet family of protocols. Its main advantage is the fact that, due to the popularity of Internet, TCPrIP is, and will surely remain, universally supported by all major wireless communication technologies. Moreover, the standard tools can be used to browse network, download files, send e-mails or access Web pages — all from the construction machine, independent of the actual communication technology used. While today it is only important during the development process, it is hard to imagine all possible uses of these technologies on the construction site of tomorrow. Therefore, it has been decided to adopt TCPrIP interfaces for Multi-CIRCOM. 4.2.5. Hardware choice Even with TCPrIP interface insulating the system from the communication device choice, it was important to survey feasible solutions. The following

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choices have been considered: Ža. radio modems, developed to prolong rather slow Ž10–20 kbitrs. Peer-to-Peer serial connections over distances of several kilometres, therefore with low networking capabilities, rather robust, requiring licence to operate, Žb. digital cellular devices, originating from personal communication world, currently not supporting broadcasts and relatively slow Ž10 kbitrs., data connection expensive to initiate and paid by time, but with a great investment and development potential, requiring a service provider, and Žc. WaveLAN devices, developed to prolong office network over distances of several hundred meters, not very robust, very fast Ž) 1 Mbitrs., developing very rapidly, but still rather expensive, licence- or provider-free. As of today, none of the mentioned solutions meets the application requirements perfectly, it has been decided to test the system with the WaveLANs, mainly because their speed offers a safety margin for the application and the physical interfacing is the easiest. 4.2.6. Communication scheme Multi-CIRCOM applies a connectionless communication scheme, which can be categorised as reliable multicast ŽPeer-to-All. protocol, with following kinds of messages Ždatagrams.: Ø positioning messages — during normal operation, most of the time,

Fig. 7. Left: multicast principle; right: collision due to message implosion.

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Ø re-send request — when a station misses some information, for example when a new compactor enters the work site or when the office requests a report about current situation, Ø alive messages — periodically, when the medium is free and there is no other data to be sent. The system tries to keep the re-send rate as low as possible. To achieve this, each station keeps record of the missing positions it tries to recover Ž‘‘list of wishes’’. and the requests issued by the other stations, which it may possibly answer Ž‘‘list of assets’’.. Internally these two kinds of items are competing in two priority queues: a ‘‘missing queue’’ and a ‘‘request queue’’. An item with highest priority will be issued first and the priorities change dynamically. In fact Žthis has been confirmed by tests., such architecture operates as software relay, taking into account that stations are mobile and the topology of the possible direct connections may change at any time. 4.3. The positioning system of CIRCOM 4.3.1. Problem statement Localisation software and hardware are key-components of the CIRCOM system. From a preliminarily concept and prototype, localisation was performed using a stand-alone RTK GPS unit w5x. Now, this solution has the main drawback that a lack of

Fig. 8. A typical trajectory.

Fig. 9. Speed profile.

localisation data may arise in the quite frequent situations of ‘‘GPS shadowing’’. In order to solve this problem, it was decided to couple dead-reckoning sensors to the GPS unit, dead-reckoning localisation being mainly activated during ‘‘GPS shadowing’’ phases, and used as complementary information when the GPS works. The sensor configuration and the design of the processing algorithm have already been described in details in Refs. w9,10x. In this paper, we will only recall the final results. 4.3.2. Results Figs. 8–11 show a typical trajectory of the compactor, the corresponding speed over the first 5 min,

Fig. 10. Lateral errors for 11 different masking instants.


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road. To achieve that goal, it is necessary to use optical technologies, capable of very accurate measurements, together with state-of-the-art fusion techniques for data processing w7x. In the frame of the CIRC project, a new laser-based instrument has been developed, called ‘‘LaserGuide’’.

Fig. 11. Absolute error and precision indicator.

lateral error signals for masking situations starting at time instants 40 to 50 s Ž11 curves. and, finally, the absolute error Žsolid line. and precision indicator Ždotted line.. These results come from simulations, but realised with real positioning data, coming from the real configuration. Later full-scale experiments showed that comparable results were obtained in real-time. In Fig. 10, the 11 curves are nearly perfectly superimposed. The error changes sign when the speed is inverted because of our convention. Should the masking periods occur in a curve, the various signals would have been distinguishable. Indeed, the variance of the noise on v has been set to perform optimally in this type of situations since a straight line movement is the standard situation for the compactor. Many tests have been performed on various trajectories. For all standard trajectories, the required precision of 0.2 m has been obtained for more than 100 m. 4.4. The positioning system of CIRPAV 4.4.1. Problem statement Since a pavement surface is a 3D surface, the paving process needs to be accurately controlled in the six dimensions of machine position and spatial orientation, the attitude angles being necessary to control the slopes of the surface, in particular, the roll angle corresponding to the cross-slope of the

4.4.2. LaserGuide principle LaserGuide is essentially a new form of automatic theodolite which has some similarity to a laser level in that it emits a compound laser beam that rotates in azimuth about a vertical axis through the instrument. The compound beam is formed as a pair of diverging fans, and when incident on a flat vertical surface would generate a ‘‘V’’ pattern. The essential features of this design of instrument are that the spatial direction to any suitable target Žphotocell or glass corner-cube prism, called ‘‘beacons’’. which is within the vertical coverage of the beams, and at any azimuth, may be determined for every scanning cycle of the compound laser beam. This is achieved by use of a single angle encoder within the instrument; as compared with both a vertical and horizontal scale of a conventional theodolite. For ranges of up to 150 m, the pointing accuracy per target is of the order of a few arc seconds, and for the current designs the scan rate is between 1 and 2 Hz. 4.4.3. Sensor configuration The system geometry that has been chosen for CIRC involves the placing of the instrument on a trailer Žor trolley. firmly attached and closely following the paver. At regular intervals along the sides of the newly constructed road, a series of beacons are arranged. Their optical centres are at known 3D positions in the local survey control frame. As the paver, and hence its trolley, progresses, the scanning laser beams strike successively the roadside beacons; these ‘‘transpond’’ the occurrence of these events and the geometrical measurements of spatial direction are made on-the-fly at the instrument. This information is used by the LaserGuide computer to determine its own 6D spatial parameters of position and orientation in the site survey co-ordinate frame. This process of dynamic spatial resection has a number of advantages. The main one arises from the

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‘‘long baseline geometry’’ of this technique, maintained throughout the measurements. Further, the measurements data is produced directly at the paver and requires no external data link. Additionally, no fresh set-ups of the instrument are necessary. In Fig. 12, a tripod-mounted prototype LaserGuide instrument produced at UEL for the CIRC project is shown. It has been designed to operate over a vertical range of "158 with full-circle coverage in azimuth. The laser beams scan rate is between 1 and 2 Hz and the repeatability of pointing to a beacon at the maximum design range of 150 m is between 1 and 2 arc seconds. It is shown in the figure with its PC104 computer box linked to a laptop for displaying the test data. The beacons are designed to have identical optical-centre heights above their base points. Each incorporates the feature of automatic tracking of the instrument while the scanning laser beams are operating. Thus the site requirements are restricted to setting-up the beacons on ground points of known XYZ site co-ordinates; levelling them with the inteFig. 13. A LaserGuide transponder beacon.

gral bulls-eye bubble and then leaving them to ‘‘find’’ the laser instrument. At that stage, the beacons will continue to generate automatically the appropriate transponding optical pulses towards the instrument each time they intercept a scanning laser beam. In Fig. 13, one of the transponder beacons attached to a stabilising tripod is shown.

5. Progress and achievements 5.1. CIRCOM

Fig. 12. The LaserGuide prototype and its processing unit.

5.1.1. Mono-CIRCOM The CIRCOM prototype has been developed during the first half of the project in its mono-machine version. Experimentation and validation trials have been organised on the Eurovia A84 motorway ŽNormandy, work-site in Villedieu-Les-Poeles ˆ . France at the beginning of September 1998 ŽFigs. 14 and 15..


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Fig. 14. The compactor used for the full-scale trials.

These trials were successful and showed that the main functions required were fulfilled, in particular the performances of the positioning system, even inside GPS shadow zones, thanks to its innovative fusion between GPS and dead-reckoning sensors measurements. Moreover, the CIRCOM system being used during several days in real conditions by compactors drivers, many remarks were gathered from these users, mainly concerning ergonomics and ease of use. 5.1.2. Multi-CIRCOM The multi-compactors functionalities have been designed and developed between October 1998 and October 1999, as additional work, financially supported by the French Ministry of Transport. To assess the specific multi-compactors features, other field trials, similar to the first ones, were organised on another Eurovia work site in Darnieulles ŽVosges, France., in early October 1999, involving two real compactors and one simulated one. The first compactor has been equipped with a complete CIRCOM system, and the second one with a reduced CIRCOM system Žuse of non-rugged embedded computers and displays, and of a simple GPS receiver as positioning system.. A third system was installed in a stationary van, located on the border of the road, thus allowing to simulate a three-compactors way of working. Fig. 16 shows the experimental configuration.

Two days of demonstration have been organised at the end of the trials, one for the members of the end-users’ club of the project and the other one for representatives from the partner Eurovia. These successful demonstration showed that all the mandatory multi-compactors functionalities, as expressed by the end-users, were fulfilled by the system. When he wishes, the user has the possibility to display a consolidated compaction map, taking into account the work done by all compactors of the fleet, as shown in Fig. 17, shot during the trials.

Fig. 15. The on-board MMI of CIRCOM prototype during compaction.

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Fig. 16. Demonstration with two Multi-CIRCOM-equipped compactors.

Drivers found very satisfying to see their own position compared to the one of their colleague. It helps them in their work especially for minimising the joints between passes, and also of course to continue the work started by the other.

5.1.3. CIRCOM pre-industrialisation In parallel with Multi-CIRCOM-related developments, the CIRCOM system Žin mono-compactor version. has benefit from a pre-industrialisation study. Mainly, with respect to the very first proto-

Fig. 17. On-board display during multi-compactors operation.


type, the pre-industrialised version of CIRCOM takes advantage from: a noticeable enhancement of robustness in terms of hardware, a higher level of integration, a higher quality ergonomics through the use of a specific sensitive keyboard and of a high-brightness LCD display on the on-board MMI. This pre-industrialisation study has allowed the CIRC consortium to enter true commercial negotiations with members of the end-users club, disposing of the key-information tending to show CIRCOM as cost-effective. Issuing these negotiations, a first CIRCOM system has been manufactured and delivered beginning of November 1999 to a well-known machine manufacturer. After preliminarily and successful on-site tests, it is now planned by the manufacturer to organise demonstrations for his own clients in December 1999, his final objective being to integrate as first mount the CIRC devices into the product lines of his compactors and pavers. 5.2. CIRPAV At the end of the year 1999, the CIRPAV prototype is currently in the integration and experimentation phase. After the tests of the LaserGuide system that have been carried out using LCPC’s ‘‘Sessyl’’ facility w8x, the three sub-systems have been integrated in December 1999. In the next steps, CIRPAV will be experimented and tested from a functional and performances points of view. The experiments will be carried out on a real paver, spreading artificial and real bituminous material on the paving test track of LCPC in Nantes, France, during January 2000. Demonstrations to the European community and end-users will be organised in February 2000.

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