CAN Newsletter special issue railway vehicles

CANopen profiles for rail vehicle applications

CAN (Controller Area Network) was developed in the 1980s for automotive applications. It is a very robust and flexible network. CAN controller and transceiver chips are available for reasonable prices due to the high quantities required in the automotive industry. These facts have made it attractive to developers of non-automotive systems, too. Also in the application field of rail vehicles, CAN-based systems are used to connect control devices, sensors or drives. Some of the diesel locomotives manufactured by Siemens or Vossloh distribute the control data via CAN. Alstom LHB, Stadler, Vossloh Kiepe and other manufacturers of trams, light rail vehicles, and commuter trains have equipped their vehicles entirely with CAN-based networks. As CAN defines just the physical layer and the data link layer (Layer 1 and 2 of the 7-layer OSI reference model), a higher layer protocol was required. The standardized CANopen application layer and communication profile (EN 50325-4) was chosen by many manufacturers, in order to avoid company-specific solutions. CANopen enables system designers to integrate devices from different manufacturers into one network, thus giving them the option of choosing and comparing cost and functionality of devices. Devices can also be used more flexibly, e.g. they can be re-utilized in different applications. CANopen is a CAN-based higher layer protocol that was developed as a standardized embedded network with highly flexible configuration capabilities. To be able to use common industrial modules and off-the-shelf software a certain degree of standardization is necessary. The further the communication within the CANopen network is standardized, i.e. in CANopen device and application profiles, the simpler the configuration of devices or components of a control system becomes. Such application profiles specify exactly the address space and the communication parameter for the different components (virtual devices) of a control system. Despite the strict rules, CANopen device profiles offer also the possibility to implement manufacturer-specific device behavior. Thus system integrators have the option of adding functions on top of the standardized default behavior.
In order to minimize the effort of system integration, the non-profit users’ and manufacturers’ group CAN in Automation (CiA) has established the CANopen Special Interest Group (SIG) rail vehicles (including Deuta, Knorr-Bremse, Luetze, MTU, Selectron/Schneider, Siemens, Voith, Vossloh Kiepe, etc.), which develops CANopen application profiles specifically for rail vehicles.

Air-conditioning for the engine driver

The series Re 420/620 locomotives taken into service at SBB (Swiss Federal Railways) during 1967 to 1985 are fitted with a static base load heating system as standard. During the summer months, compartment air temperatures in excess of 45 °C are by no means rare. In view of this background, it is sensible to consider retrofitting the driver’s cabs with air-conditioning systems. SBB Cargo Industriewerk based in Bellinzona (Switzerland) was put in charge of overseeing the locomotives’ conversion.
In order for the air-conditioning systems to be operated, it was necessary not only to provide the power supply bus also the automation system as well as a range of peripheral items such as cabling, windows and air ducts in the vehicles. In addition, installation technicalities had to be taken into account and adaptations made to the locomotive body, i.e. making cut-outs in the locomotive side walls, fitting static reinforcements as well as integrating service doors and openings.

Air-conditioning system

Two air-conditioning systems are used in each locomotive. The key components of the air-conditioning system are compact air-conditioning units manufactured by Termogamma SA of Biasca. Fig. 2 and 3 provide an overview of the principles of the air-conditioning systems as well as the technical data for the units. The air-conditioning units were designed to be used not only with energy-saving mixed-air mode but also in a mode referred to as “free-cooling” in which a high proportion of outside air can be used for cooling.

Cooling

Programmable logic controllers (PLCs) are responsible for the open and closed-loop control processes. In addition, each driver’s cab has been provided with an input terminal. This allows the locomotive driver to adjust the preset temperature according to personal requirements, within a ±3-K range. The temperature of the driver’s compartment is adjusted depending on the outside temperature. The set operating modes are automatically switched over between the occupied and unoccupied cabs whenever the driver changes cab several times, something that is typical for shunting. Communication is handled by the CAN vehicle bus that connects the two driver’s cabs together.

“This will have a positive economic effect”

In the following interview, the editors of the CAN Newsletter and Stefan Ingenhorst of the DB (German Rail) Systemtechnik, department of Informationstechnik (TZF 52) discussed the meaning of standardization.
Q: Is the standardization of rail in-vehicle networking an issue for the DB?
A: Because of the long time of ownership of rail vehicles it is often the task of modernizing of vehicles or the integration of new sub systems. For an easy system integration it is very useful to have an open and well specified in-vehicle network like CANopen. Even the replacement of obsolete components is quite difficult if the data-interface is proprietary and not well specified.
Q: What do you expect from the recently started IEC standardization on additional vehicle networks such as CANopen?
A: In fact there are different reasons to use other vehicle networks as the MVB. That’s why it is very useful to open TCN for certain vehicle networks. The approach from the CiA with the CANopen device profiles considering the DIN 25002-2 is very suitable for an open system architecture like we like to have.
Q: Several diesel locomotive and rail vehicle manufacturers use CAN as rail vehicle and embedded networks. Is there a need also to standardize the content of the transmitted data by means of CANopen application profiles?
A: Sure. To standardize the content of the transmitted data using CANopen application profiles will save lot of work on documentation, development and system-integration. It will be much easier to use the same components with the same interface on different vehicles. This will have a positive economic effect.
Q: Which CANopen application profiles have high priority for the DB?
A: The work on the UIC Leaflets for brake control and for door control is not finished jet. For the complete description of the communication on the train network it is very interesting to have soon the profiles for brake control units, slip/slide control system and door control. And others will follow.
Q: Is CANopen also a candidate for train networks in light and commuter trains?
A: No, it isn´t. DB has made the decision to use only WTB (UIC 556) as the train-bus for train-control purpose. An additional train-network with high bandwith will be used for passenger information, entertainment, internet etc. We are supporting the Technical Committee 9 from IEC (International Electrical Commission), which is just working on this item.