SNCF is the French national railway authority. This French Profit Public Body (railway activity) and its subsidiaries employs 200 000 people and had 25.2 billion € in 2008. It is attracted to Wireless sensor Networks (WSN) because installing wired sensors in existing rolling stock or in wide outdoor deployment (along rail track, in maintenance or working sites) or for temporary deployments can be complex and very expensive.1 day of its TGV high speed train downtime costs about 10 k€ (=15 k$). WSN promises:
- Very low power consumption feature:
- No need for wired external power.
- Required for maintenance issues: 1 year up to >10 years
- Mesh Networking multi-hop technologies: automatic and dynamic configuration and routing
- reliable self-healing networks for long-term or wide installations.
- Well adapted to mobility and change in the environment
- Low throughput in mesh networks = well adapted to alarm/detection systems
Various application domains are envisaged, including:
Self diagnostic :
- Intelligent trains
- Intelligent railway infrastructures
- Wire replacement (harsh environment, cost reduction...)
- Mobile instrumentation
- Security (avoid accidents)
- Supervisory control, remote monitoring
- Passengers' comfort (temperature / lighting supervision...)
- Railway safety (avoid aggressions...)
Speaking at the IDTechEx Energy harvesting conference in Denver in November 2009, Oriane Gatin noted the wealth of energy harvesting options and potential benefits in this railway environment including:
- Solar energy for outdoor deployment
- Vibration energy: from train for embedded applications or from passengers walking inside main train stations...
- Huge electromagnetic fields close to catenary (1500V. DC or 25000 V. AC) or dense WiFi traffic in train stations
- Temperature gap for embedded applications
Objectives include increasing WSN battery life and autonomy of the system. SNCF wants energy for all sensors, processing and communication parts to provided from external sources, with no need for maintenance.
Using WSN preferably with energy harvesting there are various specific environments and elements to monitor:
Embedded: freight, urban, regional, high speed
- all-metal
- vibrations, collisions
- in motor coach or locomotive: very high electro-magnetic fiels
- radio transmission from the outside to the inside of the train not obvious
- Important trains heterogeneity
Rail infrastructure: tracks, catenaries, signaling, civil engineering structures: all-metal
- outdoor deployment à temperature & covering (snow, leafs...) issues
- equipment theft issue, ballast collision on equipments
- ballast collision on equipments
- electric arc at catenaries etc
Buildings / facilities: large open areas, inside/outside
- Train stations: many interference in large one, >300 WiFi AP seen from Paris train stations!
Office buildings, maintenance establishment
Control of dangerous goods
Several field experiments have already been carried out using WSN including control of dangerous goods under the French ANR/PREDIT Tr@in-MD project (partners: CEA LIST, INRETS, Senseor...) . here the goal was wagon localization, events detection and remote alerts. Events detection involved gas outflow, temperature, pressure and gate-opening. There was wireless network from sensors to a central element on a wagon. Several WSN solutions and architectures were studied. Two WSN technologies were evaluated on tank cars in motion. More details: http://www.trainmd.fr/
Event detection on commuter trains
Event detection in commuter trains was the focus of another project. This involved the European Eureka/Celtic BOSS project (partners: Thalès Communications, Telefonica, INRETS) . There was an Intelligent Video surveillance system onboard urban and regional trains, the onboard network consisting of a wireless sensor mesh network for event detection and alert transmission + WiFi for video transmission. This 6LowPAN system included in the project final demonstration on a train in commercial use in Spain. For more details see http://www.celtic-boss.org/
Temperature monitoring on high speed trains
An investigation of temperature monitoring on high speed trains involved a mesh network for temperature monitoring on high speed train axle boxes. This application involved alerting the train driver if a threshold is passed. Because this was a safety application, high reliability was required. A ZigBee network was deployed for an experiment on a TGV at 300 km/h.
Future applications
Future applications are foreseen to include:
Fast deployment of measurement systems
- to ripen mathematical simulation models and better understand physical beahaviours (any domain: dynamic, accoustic...)
- to check if a modification on the infrastructure or the train actually needs to be done according to previsions
Indoor location
- In train station for passengers' guidance (accessibility, information) or mobile context-aware applications
Comfort monitoring
- Temperature and lighting control
- In passengers' trains, train stations and buildings
In a long term, basic infrastructure monitoring could be done by any train in commercial usage through low cost embedded networks and WSN deployed along the tracks. Detailed monitoring to optimize maintenance is of particular interest.
SNCF concludes that there are a huge number of potential WSN applications in their system including high reliability safety related uses. Standardisation will be sought. The trend will be to increase local processing to limit data transmission and employ energy harvesting to permit autonomous systems, matching maintenance issues. Clearly there is a need for equipments ruggedized and ratified for specific railway environment and to decrease module size for embedded deployments. This means sensor + processing + energy + TX + packaging. For widespread use, costs will also have to come down.
All images source SNCF
For more read Wireless Sensor Networks 2009-2019
