Hiroshi Mochizuki

Safety and Reliability Estimation of Automatic Train Protection and Block System

Considering the high maintenance costs of trackside equipment and its vulnerability to natural disasters, a novel railway system named Automatic Train Protection and Block (ATPB) is proposed by the authors to aid in improving the efficiency and reducing the cost of regional train lines. It is a railway radio system based on onboard equipment. In order to ensure its system safety, the paper gives a formal analysis on the functional requirements specification for the system. Specifically, after analyzing the actual requirements, a UML model of the ATPB system is created first to check the functional completeness and structural reasonability. Second, a formal and unambiguous specification of the ATPB system is established by VDM++, i.e. VDM++ model, based on the UML class diagram. Third, the internal consistency and satisfiability of the formal specification is verified and validated. Finally, a simulation is conducted strictly according to the formal specification. Without any runtime errors, collisions or derailments, the results demonstrate the high quality of the simulation and the safety of the specification. Copyright

Modeling a Distributed Railway Interlocking System with Object-Oriented Petri Nets

This paper describes how great progress of distributed technology and intelligent terminals makes it possible to develop a distributed railway interlocking system (DRIS). This paper presents a modeling method of DRIS by using G-nets, which are Petri nets extended with object-oriented concepts. The modeling method improves maintenance and reusability remarkably. Based on the models, the DRIS can be implemented with an object-oriented language such as C++ or JAVA.

Onboard Measurement Method for Signaling Equipment on Probe Trains

This paper describes how an automatic train protection system (ATS) and a track circuit is a fundamental and essential element of a railway signaling system. First, the paper mentions maintenance technology for ATS. For the stable operation of an ATS, the management of the quality factor (Q) of the ground beacon is essential and the Q must be kept its value within a specified level through maintenance. The newly developed measurement method is based on the current ratio between two different frequency levels of a pick-up coil current when the train passes the beacon. And it can provide the correct Q data against the distance-fluctuation. Secondly we develop the onboard method of measuring track circuit. The current of track circuit which is received through a pair of onboard signal receivers is continuously recorded and analyzed. From the analyzed data signal engineers judge the necessity of maintenance of track circuits. These measuring technologies are installed onto the probe train which is one of revenue-earning train with measurement functions. A condition based monitoring system is realized through the result of statistic processing of monitored data which is collected from two or more probe trains.

Formal Analysis of Automatic Train Protection and Block System for Regional Line Using VDM

This paper introduced a novel railway system, Automatic Train Protection and Block (ATPB) briefly, which is proposed to improve the efficiency of existing regional train lines with low cost in Japan. The biggest superiority of ATPB system is a great use of universal and mature technologies, such as GPS and regular mobile telephone networks, so that there is nearly no increment of trackside equipments in the reconstruction. Then in order to guarantee the system safety, a formal model of ATPB is established and analyzed by formal method VDM++. Firstly, the specification is specified by VDM++ formally without ambiguity. Secondly, its internal consistency is proved by discharging the proof obligations. And finally, its satisfiability is checked by systematic testing, which executes specification and checks the outputs against corresponding inputs.

Formal verification of Communication based Train Control system

In the CBTC (Communication-based Train Control) system, the wireless terminals (repeaters) are the communication bridges between the control-center and the on-board system. This paper presents a formal analysis of the train-to-ground communication link verification (TCLV) system. Firstly, this paper lists the requirements and analyzes the necessary system state and operations, then transforms the natural language describing system into a rigorous mathematical described model. At last, for the formal model, the proof obligations are proved to verify its internal consistency, and the validations are proved to verify the states and operations satisfying the expected requirements. The result of proof denotes that the actual system designed as the specification described in this paper would satisfy the requirements under the premise of safety and reliability.

Development of a High-Speed Rail Transmission System using Digital Signal Processors for Railway Signalling

This paper describes how railway signaling systems that transmit control information via rails have been deployed in many applications, for example, digital automatic train control (ATC) systems for controlling train speed. Since the performance of digital ATC systems depends on the signal transmission speed, recently there have been many studies aimed at realizing high-speed data transmission. However, it is difficult to increase the transmission speed because rails have strong attenuation at frequencies above about 10 kHz. Therefore, the present transmission speed limit of digital ATC using rails is about 300 bps. To overcome these limitations, the paper aimed to increase the transmission speed by improving the modulation method. In this paper, we propose a new modulation method combining code-division multiple access (CDMA) and quadrature amplitude modulation (QAM), called the CDMA-QAM method. This method transmits QAM symbols allocated based on a CDMA signal. It has the advantage that QAM errors can be recovered if they are in a range where they can be absorbed by CDMA demodulation. The paper developed a CDMA-QAM rail transmission system based on digital signal processors. The paper conducted a field experiment using an actual rail and verified that the system can achieve favorable constellation characteristics with about 20 dB attenuation of the received signal at a carrier frequency of 3 kHz.

Development of a Railway Signaling Device Based On Mixed Digital and Analog Signals Using Digital Signal Processors

In Japan, automatictrain control(ATC) systems, onetype of railway signaling system, transmit train control informationby using analog signals based on amplitude modulation (AM) in the audio frequency band. To realize highly functional train controlby increasing the data transmission speed, there havebeen many studies on digital ATC that transmits train control information by using digital signals based on phase shift keying (PSK), and these systems are employed in some railway lines. In practice, however, it is difficult to install digital ATC because it is impossible to ensure another transmission band for digital ATC signals due to the existing track circuit configuration and interoperability conditions, and there are many railway lines in which analog ATC is still employed. To overcome this restriction, we proposed a novel railway signaling system using mixed digital and analog signals. We employed quadrature PSK (QPSK) for digital signals and developed a transmission device using digital signal processors. We evaluated the transmission characteristics by conducting a basic experiment.

Blocking Time Reduction for Level Crossings using the Genetic Algorithm

This paper describes how the blocking time of a level crossing influences traffic on a road that crosses a rail line. The blocking time of a level crossing will be especially long on a heavy traffic rail line. The purpose of this paper is to reduce the blocking time of level crossings by optimizing the railroad schedule. The paper proposes an optimal schedule in which the departure time at each station is delayed minutely from the time of the planned schedule. Since there are many trains on a heavy traffic rail line, the number of combinations of minutely adjusted departure times will be enormous. The paper used the genetic algorithm (GA) for searching for an optimal railroad schedule. The delay time for each train at each station is used as a gene value, and a chromosome is composed by connecting the genes for each train. The fitness value is the total blocking time of all level crossings on the model rail line. Results for the computer simulation show that our optimal railroad schedule gives a shorter total blocking time compared with the planned schedule. In addition, the paper examines the composition of the GA calculation with a grid computing technology for the purpose of reducing the GA operation time.