Intelligent solutions for intelligent transportation systems
SPEED, reliability and safety are important to operate railways systems efficiently and economically. Here, automation technology can be used to lower labour costs and create a more “real-time environment” for communication and data transfer.
However, railway transportation systems consist of many complex sub-systems that together form a distributed architecture requiring centralised control and monitoring. Because of the complexity involved, an open, reliable network that can connect to and communicate with all sub-systems is required to ensure that management and operation is carried out in the most intelligent way.
System description
RAILWAY systems contain many subsystems. These include control and dispatching (signalling), environment monitoring, video networking surveillance and electric power supply. Such subsystems are generally located at remote locations, namely railway stations.
A layered network is often used to integrate these subsystems into one complete system.
The device-level control network is a fieldbus network that uses gateways to communicate with the Ethernet network. All information transmitted from the field is forwarded to the upper layer network via the Ethernet.
The station-wide control network connects the main subsystems of each railway station with the Ethernet network. The station-wide networks are then integrated via the backbone network to transmit operations information between stations.
The backbone network collects and transmits operations information from each station to the central control room. In this way, the control room has sufficient information for further control and analysis.
The device level network collects operations information from devices such as PLCs, DCS systems, field I/O devices and SCADA and CCTV systems. This information passes through the gateways, after which it is sent to the Ethernet network. The backbone uses a Gigabit Ethernet network, which provides enough bandwidth to handle data and video communication from station to station easily.
The three layers of networks connect all of the stations together, and integrate all the information required to keep the system operating smoothly. The end result is a railway control system that is fast enough to respond in real time, and that runs more efficiently.
Requirements
RAILWAY transportation systems are characterised by mission-critical requirements and the need to provide on-time service non-stop.
For this reason, the networks that connect to subsystems should satisfy the following primary requirements:
High reliability: Network devices must have a high MTBF and use redundancy to ensure non-stop operation.
High bandwidth: A large volume of data (including images) is transmitted over the network. Thus sufficient bandwidth is needed (this is especially true for the backbone network).
Rugged design: Railway systems may need to operate reliably in different types of environment, including those that experience extreme temperatures, and sites that are subject to incessant vibrations.
Long-haul transmission: Railway systems consist of many stations, some of which could be separated by hundreds of kilometres. A network used to integrate operation information from that many stations must be capable of transmitting data over long distances.
Free from interference: Since railway environments are subject to various types of interference that may effect the operation of the electronics, the devices making up the railway systems need to be free from interference.
Real-time network: In order to provide real-time information for railway operations, a railway system requires an open and fast-transmission network.
Networking solutions
THE stability and reliability of network communication are at the core of constructing an intelligent railway transportation system, according to Moxa.
Its networking products include industrial Ethernet switches, serial device servers, embedded computers, media converters and video servers.
Moxa Ethernet switches support media redundancy, support from 10/100 Mbps to Gigabit transmission speed, have a high MTBF for network reliability (e.g. Moxa’s EDS-508 series has an MTBF of 260,000 hours), and operate under extreme temperatures (from -40 to 75 degrees C). Moxa’s EDS-508-SS/405-SS series supports long-haul transmission of up to 80 kilometres.
* Crisp Technologies is Moxa’s technical support centre in Australia.
6-Feb-2006