Ethernet Train Bus Article

Ethernet as a Train Bus® Article for the Forum Bahntechnik of the CNA Author: Manfred Schmitz, CTO MEN Mikro Elektronik GmbH Nuremberg, February 2010 Railway vehicles – be it railcars or locomotives, underground trains or trams or passenger and freight trains – are equipped with a multitude of single functions which are all interconnected. For the train drive these are the control of the traction and the brakes, the clutches and the gearboxes, the antiskid system and the increase of braking power via sanding. In the driver’s cabin there are the display systems for speed, tank filling level, SIFA (monitoring), GSM as well as the data logger and train safety systems. The motor starter, the pre-heating system or the traction cooling system are connected to the main supply, while the electric equipment and the battery are connected to the auxiliary supply. In a vehicle for passenger traffic there is also the control of the inner and outer doors, the inner and outer lighting system, the air conditioning and the sanitary equipment, the train coupling and possibly the tilting system. Recently passenger information systems and wireless access to Internet services have been increasing traveling comfort. Another trend is to systematically equip trains with monitoring and safety systems for passengers and the train infrastructure. In the past, many of these subsystems could be accessed via point-to-point-connections on the basis of RS232 or RS485. As the number of computer-controlled subsystems increased, it was necessary to switch to higher-performance communication channels so that different fieldbus networks were introduced in railway vehicles. The latest data-intensive innovations like infotainment, web access and other wireless services like GPS and GSM led to solutions based on Ethernet networks. At the moment the whole transport industry is changing rapidly, there are as many approaches as there are vehicle manufacturers. Development of Bus Systems in Trains In the IEC TC 9 WG 22, the Train Communication Network TCN has been created in the 90s as a railway-specific fieldbus according to IEC 61375 in cooperation with the UIC (International Union of Railways). It consists of the Vehicle Bus MVB (Multifunction Vehicle Bus) and the Train Bus WTB (Wire Train Bus). The TCN defines the time and safety critical data transfer in railway vehicles using the complete Layer 7 architecture. The deterministic transfer of time-critical process data is guaranteed by periodic, source-addressed transmission and reliable on-demand transmission of data, either point-to-point or via a multicast transmission protocol. As the main focus for the WTB was on interoperability, the UIC has defined application profiles and a conformance test in the leaflet 556. Since 1995, practically all vehicles delivered by Bombardier and Siemens have been equipped with MVB and in most cases also with WTB. The software stacks have been developed at Bombardier MEN Mikro Elektronik GmbH Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail [email protected] www.men.de Page 1 of 6 Geschäftsführer Manfred Schmitz, Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr. DE 133 528 744 Deutsche Bank AG Kto. Nr. 0390 211, BLZ 760 700 12 HypoVereinsbank Kto. Nr. 1560 224 300, BLZ 760 200 70 In real-time applications. displays in the driver cabin. However. CCTV video monitoring cameras. 1560 224 300.a typical example of building up a barrier for fending off competitors. are used. GSM receivers or WLAN terminals are connected to the Ethernet switch – the IT bus structures become homogeneous.5 Mbits/s via optic fiber cables and/or twisted pair cables. There are no user organizations as for CANopen and Profinet which look after the standard. In addition. The WTB train bus. This entails that dependent on the manufacturer different fieldbuses like CANopen. Some manufacturers have already taken the first step and established Ethernet IP as an information bus beside WTB as the train bus and MVB or CANopen as the vehicle bus. Different Kinds of Ethernet The big technological progresses of Fast. As the MVB controller chips are proprietary and expensive. GPS modules. often other fieldbuses like CANopen or Profibus are used instead of the MVB with the exception of Bombardier. It features exceptional processes such as the automatic numbering of the wagons during train formation or the building up of fritting voltages (very high direct voltage used for cleaning of coupling contacts). Limits of the Conventional Fieldbus Structure Seen from today. EtherCAT. Like in the industry. In more complex trains. Price and bandwidth problems together make it ever more necessary to use highperformance standardized transport protocols like TCP/IP or UDP/IP. Profinet. however. they are not for sale and not completely inter-compatible . DE 133 528 744 Deutsche Bank AG Kto. Bitbus etc. BLZ 760 200 70 MEN Mikro Elektronik GmbH Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel.men. Ethernet seems to be able to win ground as a robust backbone in a train. which makes it possible to replace the fieldbuses used today. switching and collision-free full-duplex transmission as well as time-synchronous protocols and standardized safety protocols on Industrial Ethernet have accelerated development in automation.de . ® Within the TCN network the MVB can be used as a fieldbus inside one vehicle or inside a group of fixedly coupled vehicles. Meanwhile. Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr. content servers.and Siemens. is also extremely expensive in the application. 0390 211. Page 2 of 6 Geschäftsführer Manfred Schmitz. as different fieldbuses require different configuration tools and analyzing devices. It is defined for a data transfer rate of 1. Nr. It is defined for a data transfer rate of 1 Mbit/s over a distance of up to 860 meters via a twisted pair cable and built up redundantly. there are competing standards like Profinet. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail info@men. WorldFIP. a dynamic bus system that was developed for operation of passenger trains with a locomotive. This in turn generates unnecessary costs. the cost per node is ten to one hundred times higher than for CANopen.de www. Nr. BLZ 760 700 12 HypoVereinsbank Kto. real-time data are often transmitted via WTB and fieldbus while the WTB delivers the train topology data via NADI (Node Adress & Attribute Directory). Thus there are implementation differences and differing incompatible physical interfaces which complicate interoperability. passenger information systems. Profibus. EtherNet/IP. Gigabit and 10Gigabit Ethernet. this requires gateways which have to mediate between the different buses and protocols. the bandwidth of TCN and the other fieldbuses is reaching its limit. while investments in automatization are at the same time protected in future system updates. are not sent to each station as a separate telegram. The telegram rather passes all stations which take the data addressed to them and at the same time insert data at the places assigned to them.de www. so that a consistent automatization structure is ensured. but the costs per node should be similar to those of CANopen. In EtherNet/IP a star topology combined with standardized Ethernet infrastructure devices is used. Via this AR. Communication Relations (CR) with different characteristics are defined for the parameter transfer. The names RT and IRT describe the real-time characteristics of the communication.men. The characteristics of a device are described by the device manufacturer in a General Station Description (GSD). The GSD file is used by an engineering system as the basis for planning the configuration of a PROFINET IO System. Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr. This shared usage of one telegram enables the high user data rate of EtherCAT. The concept is modular. including information for control. EtherCAT MEN Mikro Elektronik GmbH The main issue of EtherCAT is that the data for the I/O nodes. The Common Industrial Protocol (CIP™) offers a wide range of messages and services for the acquisition of data from production automatization. Simply speaking. DeviceNet uses CIP. DE 133 528 744 Deutsche Bank AG Kto. cyclic data transfer and error treatment. this is referred to as encapsulation. functional safety. etc. ® Profinet Profinet brings together the knowledge and experience of Profinet and Industrial Ethernet in one technology. drives. An Application Relation (AR) is built up between a Controller and a Device. Which solution will establish itself in railway vehicles remains to be seen. PROFINET IO describes the complete data exchange between Controllers (devices with master functionality) and Devices (devices with slave functionality) as well as parameterization and diagnosis. PROFINET IO has been designed for fast data transfer between Ethernet-based field devices and conforms to the Provider/Consumer model. 0390 211.de . Nr. This opens up new possibilities to build a completely homogeneous network based on Industrial Ethernet onboard a vehicle. PROFINET IO has been created for the real-time communication (RT) and the synchronous communication IRT (IRT= Isochronous Real-Time) with the decentralized periphery. Nr. BLZ 760 700 12 HypoVereinsbank Kto. Ethernet/IP™ EtherNet/IP – CIP on Ethernet Technology EtherNet/IP offers tools for using standardized Ethernet technology for applications with Internet & Enterprise Connectivity. This results in an extremely short processing time per node. synchronization.Ethernet Powerlink and many more. encoders. so that the user can choose the cascadable functionality himself. in EtherNet/IP telecommunication protocols which are also used for DeviceNet are transferred via UPD/IP and TCP/IP. Users benefit from the numerous advantages of open networks. BLZ 760 200 70 Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail info@men. movement and configuration. The main difference is the type of data transfer needed to meet the sometimes very high requirements regarding speed. This makes it possible to access data everywhere. CIP is media-independent and offers users a uniform communication architecture across the whole production process. According to the standardization Page 3 of 6 Geschäftsführer Manfred Schmitz. 1560 224 300. ® Ethernet Powerlink Ethernet Powerlink realizes real-time requirements using extended time slice and polling processes. tree and line topologies as required in the industry. This ECN is based on Standard EthernetIP Stacks. a mother clock can determine the time offset in the logic ring and synchronizes the distributed slave clocks. BLZ 760 200 70 . The address of each node is set in the node itself. A400M and in the Dreamliner. AFDX/ARINC 664 is driven by Airbus and Boeing and is already used in the A380. In the case of the IEC 61375 (TCN and Ethernet) it is also in doubt whether the standard will be adopted in time.g. but it is not completely real-time capable. addresses can be assigned randomly within the 4 GB process image.3 (Electronic Railway Equipment – Train Communication Network) is extended at the moment. One of the nodes in the network is the Managing Node. Here the users are asked to formulate their requirements – concertedly or – as has happened in the past . Networks with Ethernet Powerlink are compatible with other Ethernet applications. The data sequence is independent of the physical sequence of the nodes. Within a Powerlink network only Powerlink-conform slaves may be operated to ensure time-synchronous data transfer.de Page 4 of 6 Geschäftsführer Manfred Schmitz. The structure for each node is fixed in the object register. SERCOS-III is mainly used for fast axis control. to secure network traffic. ECN still only works with the expensive and proprietary TCN stack.alone. Nr. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail info@men. Powerlink can address up to 240 nodes per network segment. FL-Net is driven by Mitsubishi in Japan. the IEC 61375-1 Ed. Nr. Direct access to single nodes is enabled via Network Address Translation. CANopen Standard Device profiles according to EN 50325-4. which allocates the bus rights according to the time slice procedure. Here the optimized EtherCAT protocol is directly transferred within the Ethernet frame. Similar to CANopen single parameters or data sets are accessed via process data objects. Communication with other networks is only carried out via routers. It allocates sending rights to the controlled nodes and reads back data via polling. Powerlink is conform to e.de www. In the most simple case EtherCAT only communicates within its own subnet. Within a network Ethernet Powerlink works with fixed IP addresses (Class C. After this synchronized communication phase additional data can be exchanged asynchronously. BLZ 760 700 12 HypoVereinsbank Kto. It is possible to use star. so that it does not need special hardware. 254 available addresses). MEN Mikro Elektronik GmbH Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel. 0390 211.group user data rates of more than 90% can be reached. At the moment it is still completely unclear which standard will establish itself. In addition there are other real-time Ethernet standards like IEC 1588 (Precision clock synchronization protocol for networked measurement and control) which requires special hardware but is widely supported. is hot-plugcapable and enables direct communication between the slaves. Realtime capability is realized via distributed clocks. 1560 224 300. Unfortunately. Beside TCN. Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr. DE 133 528 744 Deutsche Bank AG Kto. As the communication is built up as a ring structure logically and is based only on hardware. WTB and MVB it integrates not only a CANopen Consist Network but also defines an Ethernet Consist Network (ECN).men. TCN and Ethernet Not least. The driving factor is the big financial gain for the final integrators and end customers or users. i. It is called Ethernet Powerline (also DLAN or Homeplug). ® “Ethernet Only” in the Train of the Future This scenario in which there are still many unanswered questions from today's perspective will probably become reality much faster than expected. The power supply units have to meet special requirements. a current of up to 350 mA may flow.de www. For a supply voltage of 48 V. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail info@men. transients of 1800 V for a duration of 50 µs are specified. 0390 211. These are for example used as an easily exchangeable 19" cassette or as compact devices for spacesaving wall-mounting. the data lines are used for supplying end devices and overlaid with a direct voltage.g. For an easy on-site configuration dongles are usually used.3af divides the participating devices in Power Sourcing Equipment.e.g. There is an alternative for building up train buses in existing trains with couplings without data lines. Gateways – e. No additional lines are necessary. D-Sub connectors and M12 connectors which are now also available for Gigabit Ethernet are used. The theoretical speed of the newer Homeplug AV standard is 200 Mbits/s by now. Also. PSE and Powered Devices. line. The RJ45 connectors often used for Ethernet are not accepted in the railway market. ring and ladder structures. the intercompatibility of the devices. In trains three network topologies are used. cleaning the coupling contacts via current surges. e. Instead.Requirements for Ethernet in a Train Which (real-time) Ethernet will come out on top in trains mainly depends on it being capable of meeting some very special requirements regarding functionality. The requirements for protective circuits also differ from those for standard industry components. Here. environment and maintenance. Nr. Homeplug is safer than WLAN. they have to support wide input ranges from 9 V to 154 V. PD.men. the electromagnetic susceptibility and the temperature range. The IEE 802. This "network via power socket" establishes itself increasingly beside the traditional Ethernet cable and the WLAN network. Ethernet offers the possibility to use Power over Ethernet (PoE according to IEEE 802. They will finally be able to use MEN Mikro Elektronik GmbH Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel. from WTB to Ethernet are complicated and expensive.de Page 5 of 6 Geschäftsführer Manfred Schmitz. 1560 224 300. In addition environmental requirements as prescribed by EN 50155 have to be taken into account. While line structures are chosen for uncritical data. DE 133 528 744 Deutsche Bank AG Kto. For example. A robust connector technology has to be used on the hardware side. An important function is fritting. As the encoded data stream ends at the electricity meter. different demands are made on the maintainability of the Ethernet devices. One of the undisputed advantages is its easy installation. BLZ 760 700 12 HypoVereinsbank Kto. As a simple and cost-effective solution. that means it is faster than WLAN and the usual 100-Mbit LAN for a maximum line length of 200 meters. BLZ 760 200 70 . Nr. Drawbacks of Homeplug are the price. Gateways are indispensable as long as different communication buses are used in the train. Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr.3af). rings are common in real-time environments. ® Ethernet in the Application Ethernet as a backbone for infotainment applications (announcements. 1560 224 300. i. advertising. BLZ 760 200 70 . the problem of the automatic numbering of the wagons during train formation.de .de Page 6 of 6 Geschäftsführer Manfred Schmitz. Often the assemblies are coated against dust and humidity according to EN 50155 and specified for an operating temperature of -40 to +85°C. communication inside the train is carried out via several Fast Ethernet channels. In applications where the UIC 556 does not have to be taken into account. Udo Fuchs Handelsregister Nürnberg HRB 5540 UST-ID-Nr. remains. while wireless interfaces are used for external communication – for example for satellite-based internet access. Access to GPS. BLZ 760 700 12 HypoVereinsbank Kto. Product costs and system costs can be lowered considerably. Likewise. Nr. the vision of an Ethernet-only communication structure could become reality in the next three to five years already. MEN Mikro Elektronik GmbH Neuwieder Straße 5-7 90411 Nürnberg Deutschland Tel. on the other hand) in the train is state-of-the-art even today. games etc. All these functions are typically integrated modularly and maintenance-friendly in CompactPCI systems for 3U boards. For operation of passenger trains with a locomotive. They do not have to care for railway specific proprietary developments. For controlling the system. monitoring systems for the safety of passengers as well as logistic functions communicate via Ethernet. For further information about the CPU. +49-911-99 33 5-0 Fax +49-911-99 33 5-901 E-Mail info@men. They can benefit from the dynamic development in IT – while conforming to the industry standard EN50155.e.men. the need for interoperability.standardized protocols as well as a wide range of OEM devices and assemblies (including the Ethernet backbone with switches. railway-compliant CompactPCI systems as well as the different Ethernet Switches see www. UMTS.men. like for the modern ICE or TGV/AGV in traffic. One or several railway-compliant wide-range PSUs per system complete each solution. one or several Intel-based CPU boards are used which can carry out different functions. films on the one hand – mobile office. I/O and communication assemblies and the individually configured. The same scenario applies to the infrastructure in buses or utility vehicles. so the WTB will probably be used there for a long time still. 0390 211. Nr. GSM or HSDPA is ensured via PCI Express MiniCards on suitable carrier boards. RAID configurations for content servers are housed in similar systems. DE 133 528 744 Deutsche Bank AG Kto.de www. In one of several configuration possibilities for infotainment systems. cables and connectors). In the last instance the vehicle suppliers benefit from the basic developments and uses TCP/IP or UDP/IP as transport protocol. Camera surveillance systems are also often equipped with one or several hard disk slots for building a RAID configuration.