1 Intelligent railway signaling system in the 2T* century BNing Department of Control Engineering School of Electronic and Information Engineering Northern Jiaotong University, Beijing , P.R.China bstract In modern society, railway has been generally recognized to be a safe, comfortable, economical, less-energy consumption and favorable environment transport means on lands. Railway signaling system is still one of the core parts in railway network in the aspect of ensuring train operation safety and raising train operation efficiency. However, traditional railway signaling can not meet the requirements of modern train operation any more, particularly for high-speed passenger trains. The concept and definition of intelligent railway signaling system (IRSS) is put forward in the paper. Control and management are integrated in IRSS, based on necessary information system that is related to modern telecommunication system including mobile data communication, computer network and modern control theory etc. Passenger flow and freight flow on railway network are supported, control by information flow to ensure their efficiency, high-speed and safety. In the paper, the definition of IRSS in the 21st century, its contents, functions, system configuration and its development are described. The relation between IRSS and the existing signaling and the transition from the existing signaling system to IRSS are also involved. 1 Introduction In the future society, on the globe, there are only three flows: people flow, materials flow and information flow . For railways, the three flows will be firstly implemented to be the sequential flows. With development of electronic techniques, based on the existing railway signaling and telecommunication systems, it is possible for an intelligent railway signaling system (IRSS) to be
2 Computers in Railways VII implemented. Since a train runs on rails, it is one of the easiest transport means to be realized by intelligent control, compared with other transport means such as high way system and airline system. On a railway network, passenger flow and freight flow will be firstly controlled by information flow. In IRSS, signaling and telecommunication, control and management are integrated. t a control room, every train position, speed, its destination and other related information are known and commanded by a dispatcher and other concerned person. Meanwhile, IRSS will make it possible that at any time, at any where, any people can know the related train information by internet or other media. In the recent years, intelligent transport system seems to be only for highway traffic. In fact, concept of intelligent transport system appeared firstly in railway system many years ago. The concept and its definition of IRSS are given in this paper, combined modern electronic techniques with tradition railway signaling technique. n overall picture of IRSS in the 21st century is described. The configuration and its main functions of IRSS are also introduced. The relation between IRSS and existing signaling system, the development of IRSS and the key technical issues in the development are involved. 2 Concept and definition of IRSS The definition of intelligent transport system (ITS) has been a controversial topic for years in the areas of academic professionals. Some of people think that ITS is only for highway traffic. In Europe, it has a term " Telematic " which reflects the view that the application of information and communication technology to transport . Nowadays, There are also many words such as smart cars, smart vehicles, smart trains and smart buses etc. which are related to ITS. You can think electric traffic signals to be ITS, or track circuit to be ITS (it could be original ITS), then ITS has been around since the 1930s or the last century. In fact, no matter what you call it, in the view of system theory, ITS is that the advanced technologies such as computers, telecommunication and information technology are applied to transport to solve much better the problems such as safe, congestion, comfort, efficiency, energy and environment etc. Therefore, the concept of ITS has been appeared since the advent of advanced technology. ITS is not brand new. It has been slowly creeping into our lives over many years. ITS is not a patent of road traffic. It definitely includes railway systems. Compared with other transport mode such as road system and aircraft system, railway is the earliest system where advanced automation techniques were applied. Track circuit was invented last century. It also can be said the concept of ITS appeared firstly in railways. Traditional signaling system, including wayside device such as track circuits, automatic switches, automatic block device and signaling, and on-board device such as automatic train stop (TS), automatic train protection (TP), automatic train control (TC) and automatic train operation (TO), even centralized traffic control (CTC), could be a kind of intelligent transport system. It can be said that the concept of intelligent railway signaling system (IRSS) has been around for many years. The key issue is how
3 Computers in Railways S7 the system is intelligent and what kind of advanced technologies are applied in the system. With the development of railway and advanced technology, railway signaling system has approached to IRSS. It is also difficult to give exactly the definition of IRSS. But its content could be described as follows. ll the possible, advanced techniques, for example, computers, telecommunication including mobile communication, information, automation, micro-electronic and advanced sensor techniques, are applied to railway control and management system to make train run faster, more safe, more comfortable, more efficient, less energy consumption, more favorable to environment. IRSS is designed into a system where control and management are integrated, based on a perfect information system. fter implementation of IRSS, for passengers, if they are on the train, they can know at any time the train position and speed of the train, the train arrival time to their destination and the related information. If they are at station, by train information system, they know which train is best for their travel in terms of cost, time and comfort, all the train information they need; for freight deliver customer, they can know what kind of services railway can provided, including price, route and deliver time etc. fter the good is passed to railway, the customer can at any time know where their good is on railway network and what time their good can reach their destination. lso any people can access to the web of railway to have the related railway information by internet, such as booking tickets, train delay information etc. For train driver, they can have all information they need for train operation by MMI of on-board system, such as train permissive speed, actual speed, train graph, train arrival time to its destination etc. and communication with a dispatcher at control center. For train dispatchers, by IRSS, they can dispatch all the trains in their controlled areas by communicating with all train drivers and knowing train speed and position of each train. For railway network managers at each level, for railway network and train maintenance persons, for some of decision-makers, they can have their concerning information from IRSS. For a railway company with IRSS, according to the information of ticket booking and goods deliver requirements, a train making-up plan and us graph for passenger or freight can be automatically produced. When a train graph is disturbed by some reason, it can be recovered automatically by the expert, system in the system. With fixed data base and expert system, IRSS is an intelligent system network that can collect all the dynamic data on railway network, process that data according to the regulations and transmit them to the correspondence subsystems. 3 Configuration of IRSS The configuration of IRSS is shown in the figure 1. It looks like a telecommunication network covering railway network. It can be divided into the
4 1158 Computers in Railways VII three levels. The first level is the fundamental parts which includes the fixed units (or station unit ) and the moving units (or train unit). The first level is to produce the originally dynamic data such as switch position, track state (occupation or clearance), and to receive and execute orders from top level. The railway network and the layout of stations all constitute a data base. In IRSS, each station has a station unit which control all the switches, track circuits, signals and the sensors at the adjacent blocks; each train has a train unit which controls train operation and is responsible to communicate with station and other trains. Other system (Internet) 1 IRSS Center V \/ /\ \/ Subcenter, Subcente^ Subcenter^ /\ \/ v \/ / V V \l/ \/ \/ \; t H^ 82 ^ ^ > ^ Sj '*?"> ^ S, ^ '~ ^ S, ^ <' ' > S, r- ^ ^ ^J S, p /\ t \1 \f V V V ^[ i. r~\ /~\ / \ / \ /~\ /:\ r \. Figure 1 The second level is a sub-center shown in the figure 2. Its task is to control station units and train units. It can be a relay control unit between IRSS control center and station units, train units. If the controlled line is not very long, the sub-center can replace IRSS control center. In other word, if the controlled line is less than 1000 kilometers, there is no need to have sub-center level. If an IRSS is for a underground line or a light rail line in a city, the system only needs the two levels to complish the stipulated functions. For an IRSS, the controlled line is generally longer than 10,000 kilometers, apart from sub-center, there is a top level which is called as control center of IRSS. The top level does not directly control station units and train units. Its main functions are to control sun-centers. t the top level, train plan and train graph are produced, train operation orders are firstly transmitted to its related subcenters. Then the orders are transmitted to the related station and train to establish routes or control train operation. The data about train operation state and station state are transmitted back to sub-center to examine if a train graph is
5 Computers in Railways VII 1159 executed. If a train graph is disturbed, the recovery and adjustment are firstly made at a sub-center. It could be finished at a sub-center. If the disturbed area is very big, the recovery and adjustment could be made at the top level. Finally, all the feedback data must be sent back to the top level where dynamic and static data are processed, then transmitted to the different users for management, statistics and reference. Figure 2 Telecommunication network is the nervous system of IRS S. It can be seen from figure 1 and 2 that there is a fixed communication network along railway network. The network must ensure the data exchange between the IRSS center and its sub-center, between sub-center and its stations. t each station, there is also a local network connecting all the switches, signals and track circuits, the sensors along its adjacent blocks to an interlocking system for the station. In addition, there is also a mobile telecommunication to have data exchange between a station and a moving train, or between two moving trains. From the above description, it can be seen that the transition from the existing signaling system to IRSS is not difficult. From the system configuration view, the telecommunication network improvement, including mobile communication system is the basis of IRSS implementation. Some of the existing device can be used in IRSS. Of course, some of terminal units are required to re-designed. There is a lot of software development to be made for each level, including terminal device. 4 The key technical issues In order to implement an IRSS, the following key technical issues must be solved.
6 1160 Computers in Railways VII (1) Station system. Shown in the figure 3, the main functions of each station are to control all the switches, signals and track circuit, to collect the state data of switches [wi], signals and track circuits [Ci]. n interlocking system based on computers must be realized to establish routes for a train to stop at station, pass station or overtake other train at station, or meet other trains at station. The interlocking system must be high reliable and fail-safe. The station system is responsible to exchange data with its sub-center. It can also transmit related data to its two adjacent stations. ll the trains at station and at its two adjacent blocks can communicate with the station system. In emergent situation, a train can directly communicate with a sub-centers. ll the sensors along the two adjacent blocks are connected to the station system to collect data concerning moving train and lines . The station system is with the functions of data recording and its replaying, fault-test and fault-diagnosis. K) i-o g K) K) a x, w, H C< I I -I signal switch Figure 3 (2) On-board systems Shown in the figure 4, an on-board system consists of the two buses: locomotive bus and car bus. There is data exchange between the two buses, controlled by a switch unit . The buses system is the blood vessel of a train. locomotive bus system is the brain of a train. For a locomotive bus, CUU is its central control unit. MMI is man-machine interface of the on-board system to train driver and related maintenance person. By it, train driver can input data to the on-board system. T&B is a train traction and braking unit which connect to locomotive
7 Computers in Railways VII 1161 engine. The orders from an on-board system can be sent by the unit to engine controller to be executed there. The state data of the engine operation can be sent back to the on-board system by the unit. In.Re.T. is the interface for radio signal receiving and transmitting which ensure data exchange between train and station, train and train. Dia.U is the diagnosis unit to test and diagnose if there is a fault in the on-board system and the engine of a locomotive. P.S.M. is the unit of position and speed measurement of a train. Train speed and position are measured by the unit. TI is an on-board unit of train integrity. Its function is to check train integrity which is done traditionally by track circuit. RECORD is a device similar to a black box for an airplane. It can record all data about the operation of a train and the on-board system . For a car bus, like a locomotive bus, CCU is a central control unit for the car bus. Car ( 1 i) is the interface for car number 1 i. Each car in a fixed making-up train has its corresponding interface. The data for axle temperature and door state ( shut or open ) must be sent to the car bus, then the data are sent to the locomotive bus. The data on the locomotive bus about train position and speed, are sent to the car bus through SW. The information can be displayed for passengers in the car by a car interface. On the car bus, multimedia data such TV programme can transmitted for each car. Diagnosis data can also be sent to wayside system for maintenance preparation by the on-board system. locomotive Car, Car, Car, CJ Q Q Car,, W Locomotive' MM1 RECORD Dia.U. f > f \/ w ) ^ T6&B In.Re.T. P.S.M. TI 4/ engme SW locomotive bu 0 Car, / \ \ / Car, / \) (D Car^ CCU \/ Car ^/ RECORD Figure 4 (3) Sensors systems For an IRSS, track circuits should be removed from blocks. Block sections and
8 i Computers in Railways VII block signals do not exist any more. Moving block system is to be realized to obtain the maximum carrying capacity at block. t the same time, maintenance cost could be reduced greatly. Sensors installed at blocks monitor rails state, train operation etc. It is the eye of IRSS along the line. The sensors should be reliable and intelligent. Most of the sensors should be passive. For example, transponders are a kind of the sensors. Euro-balaise is a European standard transponders which are used in the ETCS ( European Train Control System ). Its main function is a absolute checking point for distance correction, apart from its data transmitting. (4) Control center system lot of software development should be made for control center system. In terms of its hardware and software configuration, it is a fault-tolerant system and high reliable. Software engineering methods must be applied to design the programme at the top level. The software can be classified into the three kinds: Management software, Diagnosis software and pplication software. Management software dispatches the different programme to be executed, manage all the resources including hardware. Since the system is a fault-tolerant structure, there is a lot of redundant resources ( hardware and software) which are needed to be utilized in the optimal way under the conditions of reliability and safety. Diagnosis software is responsible to diagnose if there is a fault or error in the system when it occurs. The functions of application software are to complete the different tasks such as data communication, data processing, train plan making, train graph producing and data statistics etc. pplication software is modular design. (5) Telecommunication system The functions of telecommunication system have been described in the above. The data transmitted over the network can be classified into the two kinds. The first kind of data relate to its control function. The data exchange must be reliable, fail-safe and real time . Particularly, reliability for a digital mobile communication system is a key issue to be solved. To some extent, IRSS is based on a reliable mobile communication network. By mobile communication, a moving train can exchange data with station and another moving train. The second kind of data is nothing to control function. There is no requirement for it to be transmitted in real time. Conclusion From the above description and analysis, it can be seen that IRSS can be implemented by modern techniques. It is not a totally new system, and a new concept. The key issue of IRSS implementation is its system design. IRSS is based the existing signaling and telecommunication system. It is the further development, improvement and perfection to the existing system. In IRSS, signal acquisition, transmitting, processing and application are standardized. rtificial intelligent application can be mainly concentrated on information processing at
9 Computers in Railways each level in the systems. Therefore, IRSS will reflect the direction and tendency of railway control and management system development in the 21* century. In fact, IRSS has been developed in varying degrees for many years in many developed countries. The main objective of the paper is to make the new system IRSS to be standardized. References [ 1 ] Bin Ning, n Intelligent Train Operation Control and Management System - The Railway Signaling System in the 21st Century" Proceedings of ISPECT99, London, pp , Sept  Bob Mcqueen,& Judy Mcqueen, Intelligent Transportation Systems rchitecture, pp , rtech House, Boston & London, 1999  Bin Ning, bsolute braking and relative distance braking train operation control modes in moving block system, Computers in Railways VI, WIT Press, (Comprail' 98) Portugal, pp ,  Bin Ning, nalysis of train braking accuracy and safe protection distance in automatic train protection (TP) systems, Computers in Railways V, WIT Press, (Comprail' 96) Germany, pp ,  Bin Ning, Fault-diagnosis in a new train over-speed protection system based on multi-microprocessors and distributed configuration, Computers in Railways IV, WIT Press, (Comprail' 94) Spain, pp , 1994.