A modern train management system is connected to every intelligent subsystem onboard a vehicle.

These subsystems may be such as: air conditioning, doors, lighting, passenger information systems, brake controllers, traction systems, tilt systems and auxiliary power supplies. In addition, all the vehicles are networked together to provide centralised control. Also non-intelligent sub-systems may be at least monitored during operation.
A train management system combines the non-vital control and diagnostics onboard, as well as train-to-wayside communication and user interface functions. Furthermore, occasionally the functionality of a lower level sub-system can be integrated into the TMS.
The main benefits are: enhanced usability and maintainability, safety and more economic operation, increased passenger comfort.

Centralised control

Centralised control means that there are control points onboard that can be used to control all the similar intelligent subsystems. For example, the user is able to control all the air-conditioning equipment of the train at one point. The same applies to lighting and doors. There can be a user interface panel in every car. With this, the staff can operate the connected subsystems - dim the lights, reduce the cabin temperature etc. The control is not limited to the car the user is in, but the system is able to transmit commands to any of the connected cars, or send a command to all the similar subsystems. The user interface panel also offers real-time information about the status and possible malfunctions of the connected subsystems. Information on each car may be viewed anywhere in the train.

Centralised diagnostics

Centralised diagnostics means that the train management system collects data from the connected subsystems. The data includes status of the equipment, running hours, active faults etc.
The content of this data greatly depends on the kind of device being diagnosed. The data is saved in thenon-volatile memory of the train management system, wherefrom it can be downloaded and transferred to a maintenance system for a detailed analysis. The diagnostics system is at its best when examining the interaction between subsystems, and especially when the root cause of any malfunction needs to be clarified.

The design of a TMS

The design of a train management system can be divided into three parts. The train bus provides a medium for data communication throughout the train. The vehicle bus provides a medium within a car. In addition a vehicle computer is required in order to route the data between the two busses, to store the diagnostic information, and to control the connected subsystems either independently or according to the commands of the user.
For centralised control a data communication bus (train bus) that connects all the cars together is needed. Even though the train bus is like a normal industrial bus, it needs to have a particular characteristic: It must be able to identify new cars at the very instant they are added to the train. This means that when an additional car is coupled to a train, the train bus automatically notices the added vehicle andre-configures the bus in order to facilitate the data communication between all the connected cars. A widely used train bus having this property is defined in the standard IEC61375-1 Train Communication Network: The Wire Train Bus (WTB).
The mentioned standard gives a definition for one type of vehicle bus, namely the Multifunction Vehicle Bus (MVB). This particular bus is especially designed for and used in trains. However, for practical reasons, several types of industrial busses are also used as a vehicle busses onboard a train. These busses include Controller Area Network (CAN), LonWorks network, different types of serial links and train-to-wayside communication systems. A typical configuration contains more than one type of vehicle bus.
The vehicle computer is located in the intersection of all the busses and subsystems. With this, and the wide variety of possible controls, it is highly important that the programming and testing of the vehicle computer is as straightforward as possible. Using the current Programmable Logic Control (PLC) languages based on the IEC 61131-3 standard has proven useful in terms of easy use and self-documenting capabilities.

Benefits of a TMS

A direct benefit is the ease of operating the equipment such as doors, lighting and air conditioning from any point of the train.
The benefits of the collected diagnostic information are realised when the data is analysed. The diagnostic data will almost certainly contain information on any subsystem malfunction. Given time and a large enough fleet, a maintenance system can predict the possible occurrence of future malfunction. With this information the operator can perform preventive maintenance. This in turn leads towards an improved usage ratio of the fleet.
The enhanced usability and maintainability also enables the fleet to carry passengers more safely, more comfortably and more economically, which is of interest to every operator in the business.

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Jyrki Keurulainen is with EKE-Electronics Ltd, Espoo, Finland. www.eke.com