Fumio Kitahara

Widely-distributed train-traffic computer control system and its step-by-step construction

In a large scale mission critical real time control system, such as the Tokyo metropolitan area train traffic system, it is very difficult to construct the entire system at once. Moreover economic considerations makes year by year investment inevitable for developing the system. The new Tokyo metropolitan area train traffic computer control system, supplying service to 19 train lines, 300 stations and 6200 trains per day, has been constructed step by step over 8 years without halting train operations. Here the computer system is required to be expandable online during system operation and without disrupting already constructed subsystems. To enable testing during system operation, an autonomous decentralized online expansion technique is proposed. Then the effectiveness of the technique is demonstrated in a real system.<<ETX>>

Phased-in construction method of ATOS

ATOS (Autonomous Decentralized Transport Operation Control System) is a high density railway transport management system of an unprecedented scale. The system has been continuously built up in stages after the online operation of its first station commenced in 1994 and successfully operating since then. In this paper we will discuss phased-in construction techniques by line system. We intend to demonstrate the results of our proving examination of the proposed technology using practical examples. We will also discuss new requirements emerged as the result of improvements made in the network infrastructure for information systems such as information terminals and the extension method thereof. This system, now operating with first and second lines, may be termed the largest of such systems to implement the autonomous decentralization system technology.

Distributed management for software maintenance in a wide-area railway system

In a large scale real time control system, functions of subsystems differ slightly although they seem to be identical. Functions change when hardware is replaced or when the function itself is upgraded. If the standard system is generated by merging the differences and is installed then to each subsystem, subsystems become different with maintenance being carried out in each subsystem to fit its operational conditions. Furthermore, subsystems are distributed in a wide area. Software maintenance therefore becomes very difficult. The paper describes a distributed management for software maintenance in the Tokyo metropolitan area railway system. This management has two phases: generating programs for making maintenance easy and executing programs for increasing the reliability of the system. There it contributes to the effectiveness of maintenance and increases the reliability of the total system.

Assurance technologies for growing systems and their application to large-scale transport operation control systems

Recently, system needs of growing large-scale systems including heterogeneous functions and operations are increased. An assurance system that achieves high reliability and high availability is very important for such systems. In order to realize an assurance system, we developed the assurance technology based on ADS (Autonomous Decentralized System). When a growing large-scale system changes or grows, its reliability may be lowered. We clarify the risk factors which lower the reliability and quality of a growing system when the system is modified. We then examine the methods to eliminate or ease those risk factors, and propose adaptable assurance technology that can minimize the risk under restrictive conditions such as cost, resource, periods, etc. We also describe ATOS as an example that has applied the assurance technique and its effectiveness as a really changing and growing system.