The role of a train management system onboard modern rolling stock is to provide data communication and enhanced co-operation between the systems, as well as centralised control and diagnostics of the connected subsystems.qqqJyrki Keurulainen reports.

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 the
non-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 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 and re-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 IEC
61375-1 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.

Enquiry details

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