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Latest Developments for Safe and Reliable Railways
Whereas the primary function of TCMSs when they were initially introduced was to transmit and display fault information of onboard equipment, the systems have since undergone progressive functional enhancements including not only powering and braking commands during train operation, but also commands for passenger information, air conditioning, and other service equipment. Hitachi was an early adopter of broadband communication standards and developed the Synaptra series as a TCMS capable of satisfying a wide range of requirements, incorporating the system into a variety of trains supplied in both Japan and other countries over recent years. This article describes the history of TCMS development and where the systems have been used, also summarizing their current specifications and functions and reviewing directions for future development.
Hitachi's train control and management system (TCMS) has undergone ongoing enhancements to its functions and performance since it first entered commercial use in 1990, a trend that has only been accelerated by the advance and spread of information technology (IT) over recent years. Moreover, in addition to the onboard systems themselves, further functional improvements are also being made through cooperation with trackside systems using wireless and other forms of communication.
This article describes the history of TCMS development, summarizes current TCMS specifications and functions, and reviews directions for future development.
The transmission speeds achieved by the train backbone network that TCMSs use to send information between vehicles have increased over the years in step with the expansion in functional requirements, typically rising by a factor of 10 every five years (see Figure 1).
The transmission speed of the train backbone used by the monitoring systems first installed in 1990 was 9.6 kbit/s. The main function of these systems was to display information about onboard equipment faults on the cab screen. As further enhancements were added aimed at reducing the amount of wiring and consolidating onboard equipment, including control commands for operations such as powering and braking, and commands for passenger information, air conditioning, and other service equipment, and also more extensive fault detection and automatic testing, the name “autonomous decentralized train integrated system” (ATI) was applied.
The transmission speed of the ATI train backbone was 3.2 Mbit/s, and while this was initially considered to be comparatively fast for a metal-wired system that can operate in the environment found on trains, the required transmission speeds progressively increased toward the limit as the functional requirements expanded and more equipment was connected. Meanwhile, debate continued about using an Ethernet-based onboard communication standard (currently IEC 61375) and Hitachi was among the first to adopt this technology, developing a TCMS that used 100-Mbit/s Ethernet.
Since commencing trial operation of a prototype in 2010, Hitachi has developed versions of the product using a variety of equipment configurations with a number of different customers in Japan and other countries and applications in mind, with the first product deliveries occurring in 2015. Called “Synaptra” (an amalgamation of “synapse” and “train”), the system is being used in a number of applications in Japan and other countries (see Figure 2 and Figure 3).
The current version of Synaptra is a general-purpose system (Synaptra-T) capable of transmitting a variety of different data packets (for control commands, monitoring, and services) over the same hardware. The train backbone is primarily designed to have a dual-network configuration for redundancy, with one network being used exclusively for control commands and the other carrying packets for both control commands and monitoring. It can also be configured, however, as a single-network train backbone that only carries monitoring data packets, with an additional (100 Mbit/s) network for services, or with separate control and monitoring networks.
Hitachi is also working on developing Synaptra into a series of different products to allow for detailed customization to suit the different uses and circumstances of each application. This product range includes Synaptra-M (100 Mbit/s), which is designed specifically for monitoring applications and has a simplified configuration while still providing all of the monitoring functions available on the current Synaptra system, and Synaptra-S (1 Gbit/s or 10 Gbit/s), which supports the transmission of large volumes of service data such as videos and transmission logs. These different versions have the flexibility to suit a variety of different requirements, including the ability to be used alongside the current Synaptra-T system.
Figure 1—History of TCMS Development by HitachiThe incorporation of new functions has increased the speed of train backbone networks over the years at the approximate rate of a 10-fold increase every five years. It is anticipated that this trend will continue.
Figure 4—Class 800/801 Trains for UK Intercity Express Programme (IEP)The trains incorporate a large number of data-driven functions that work using databases received from offboard servers. Similarly, fault and status information from the train is transmitted to trackside systems in real time and used to support operations and maintenance.
Figure 5—Class 385 EMU for Abellio ScotRail (ASR) in the UKThe development period was shortened by using software to handle the differences between the functional requirements and connected equipment on these commuter trains and those on the IEP express trains.
Figure 6—20000 Series EMU for Sagami Railway Co., Ltd.The cabs were kept simple by designing them with the aim of consolidating, in the display unit, the various indicators that will be needed for the shared sections of track in future city center services.
This section describes some typical examples of Synaptra installations supplied over recent years.
Measures for reducing the load on the environment are also important for trains. Whereas efforts to date have sought to improve energy efficiency by reducing the weight or improving the efficiency of individual items of equipment, work is now progressing on energy savings achieved through system interoperation, taking advantage of the ease of exchanging information between the TCMS and trackside systems made possible by advances in information and communications technology. One example is the implementation of functions for ensuring energy efficiency that work by sending information to each train about train movement commands derived from the integrated operation of traffic management and power system management so that each train's TCMS can use this information as a basis for generating its speed profiles (see Figure 8).
The primary approach to maintenance in the past has been to conduct periodic inspections to ensure that equipment satisfies the requirements of various laws and directives, and to maintain the equipment to ensure that it remains up to standard.
However, by utilizing advances in TCMSs and in information and communication technology, Hitachi is already operating onboard-trackside integration systems that collect important data from onboard equipment in a server on the train and then forward it to an offboard server for storage (see Figure 9).
Being able to continuously acquire operational data from in-service equipment has the potential to reduce maintenance costs by using recently collected operational data for inspection results and to prevent service interruptions due to faults by using condition monitoring to deal promptly with performance degradation. Plans for the future include functions that make it easy for knowledgeable staff to use the collected data to identify what maintenance work is needed and improvements to the human-machine interface. Hitachi also plans to achieve reliable operation and further reliability improvements through measures such as the use of artificial intelligence (AI) and the development of techniques for structuring knowledge that involve the systematic collection of information on how to go about fault analysis and response rather than just rules of thumb (see Figure 10).
Figure 9—Block Diagram of Online Monitoring SystemCondition and fault information for onboard equipment sent via wireless communications to trackside systems can be used to support operation and make maintenance more efficient.
It is anticipated that TCMSs will become even more important in the future as a means of implementing train functions and as a portal to a wide variety of functions connected to trackside systems. Hitachi intends to continue developing systems and functions that meet the needs of the market to contribute to operations and maintenance at railway companies and to improving service to passengers.