THE SNCF GAUGE ISSUE In a context of competition and conquest of FREIGHT traffic, the European networks will have to adapt to the demand for larger rail gauges. The SNCF runs a network that for the most part was completed at the end of the last century, and one peculiarity of this network is that the gauge is often less than GB. To improve the commercial offer and make use of modern infrastructure maintenance techniques it is necessary to constantly monitor the physical outlet and position of the tracks. For some years this monitoring has been impeded by a lack of modern, suitable, high performance diagnosis tools, whether in the measurement field or in the field of simulation software, both in Europe and world-wide. It has therefore been decided to equip the French network with two types of diagnosis tool: the OBSERVEUR measurement wagon which will carry out national programmed recordings at 120/160 kph, over a cycle lasting approximately 3 years. the portable EPSILON lorries, available to the regions, providing additional functionalities (obstacle installation, laser pointer to detect obstacles, recording of complete profile in real time), functioning at 3 kph with better precision. Fig-1 In parallel, the creation of a national gauge database and the rewriting of gauge simulation software in a more user-friendly environment perfectly compatible with exploitation of OBSERVEUR and EPSILON data, should allow greater reactivity in the setting up of new traffic and make it possible to maintain a high level of safety in circulation in the network as a whole.
OBSERVEUR The Infrastructure Division has been put in charge of designing, building and carrying out experimentation on new tools required for gauge management. A needs inventory was carried out with all the different players, together with a survey of the products existing on the market and the feasible techniques. So it was that various laser telemeters and photoprofile cameras were tested to replace the previous technological processes (argentic photo) and meet a recording speed requirement of 160 kph with a minimum precision less than 3 cm. A feasibility test was conducted on the new PARIS - LYON line to measure the distances between centres of lines, which emerged as the most difficult parameter to master. This experiment used a 5 W rotating ARGON laser and two 400-600 cameras. The precision obtained at 110 kph, in ideal recording conditions it has to be said, was 2 cm for more than 5,000 profiles, which convinced the SNCF to opt for the laser photoprofile system. The European call for tenders issued in 2000 for construction of the OBSERVEUR led to selection of the solution presented by the CYBERNETIX/TECHNOGAMA grouping, which is explained below. In addition, the SNCF plans to bring in to the project an expert from the former German company METRONOM to contribute their expertise with the LIMETZ 2 vehicle. We can therefore state that the creation of the OBSERVEUR, above and beyond its technical prowess, represents an example of European co-operation in a field of HIGH-TECH development. The SNCF wishes to acquire a gauge inspection system (OBSERVEUR) operating at a speed of 120-160 kph. The SNCF has awarded to Cybernétix the contract for designing and manufacturing such a system in its entirety, which will be integrated onto an SNCF vehicle. This system will make it possible to measure the geometry of any obstacle in relation to the tracks, in particular the catenary heights and localise the 2 rails on the adjacent track, and to define the gauge within a maximum radius of 8 metres around the vehicle. The OBSERVEUR system is divided into 3 main functions: Measurement of the running track reference Localisation of the 2 rails on the adjacent track, and measurement of the ballast track profile on each side Obstacle detection around the vehicle To detect obstacles less than 1.5 cm in size at a speed of 120-160 kph, the basis for OBSERVEUR system is an optical solution integrating the new generation of CMOS technology laser sheet profilometres. This makes it possible to perform acquisition of 1024 x 1024 pixel images at a throughput of 500 images per second (sensor developed by Tecnogamma IN Italy), which requires more than 22 sensors.
All the sensors are therefore mounted on a specific tubular structure (optimised by a structure design software), in order to maintain control over their position in the OBSERVEUR's external working range. This solution makes it easy to integrate the OBSERVEUR system into any railway vehicle with a platform 8 metres long. 1. Running track reference Measurement of the running track reference is based on the conventional 3 points method to measure deflection using the laser sheet profilometres positioned at each end and in the middle of the vehicle. This configuration comprising 3 boxes each equipped with 2 profilometres makes it possible to: localize the track reference measure the curvature radius of both rails measure the rail gap and the super elevation measure all the track geometrical parameters N.B.: to compensate for any elastic structural deformation, the boxes will be fitted with optical deformation sensors to correct the geometric measurements. Fig-2
Performance Rail position: 0.3 mm Measurement of super elevation: < Measurement of deflection: < 0.3 mm minimum curvature radius: 150 metres 1 mm 2. Ballast profile and adjacent track Measurement of the ballast track profile on each side and localisation of the 2 rails on the adjacent track is based on laser sheet triangulation. The system consists of 3 laser sheet profilometre wide field sensors on each side, incorporating 3 high resolution 1024 x 1024 pixel CMOS cameras, to measure the track profile in a field of 0.6 to 5.4 metres from the track centreline, and to automatically localize the 2 rails in the adjacent track. Fig-3
2.1 Performance Profile measurement from 0.7 to 5.4 metres from the track centreline, with an acquisition rate of 200 images per second Vehicle measuring speed: 120 kph Localisation of the 2 rails to within 4 mm 3. Obstacle detection This function detects obstacles and overhead wires in an analysis zone around the vehicle corresponding to an angular field of 270 and a maximum distance of 7-8 metres. The OBSERVEUR system consists of wide field laser sheet profilometres incorporating 6 high resolution 1024 x 1024 pixel cameras and 4W laser diodes to produce a light sheet 8 metres in radius, perpendicular to the rail. Fig-4
3.1 Performance The OBSERVEUR system is used to: detect overhead wires with an accuracy of 1 cm in the track reference, detect obstacles having thickness down to 20 mm (minimum value) generate the gauge profile with 1600 points resolution, in the rail reference. Fig-5 4. Gauge exploitation software The exploitation software makes it possible to recover the file of 1600 points giving the optimal representation of the environment around the vehicle and all the obstacles. In the post-processing phase, the operator can automatically check the clearance along a line has been maintained.
Minimum clearance checking is carried by performing various gauge study simulations, and the operator can verify for example whether it is possible to run vehicles with non standard gauges on the track. Fig-6 5. Conclusion The OBSERVEUR system will be operational at the end of 2001. OBSERVEUR will enable high precision measurement of track gauges at more than 120 kph, and automatic detection of any obstacle having thickness down to 20 mm. This will generate a national gauge database, making it possible to perform automatic user-friendly gauge simulations. The OBSERVEUR system, incorporating the latest generation of laser sheet profilometres, is currently the most effective system for carrying out readings of 3D gauge measurements at high speeds (120-160 kph).