Autonomous decentralized control and its application to the rapid transit system

A large scale control system has three intrinsic requirements of fault tolerance, on-line extension and maintenance for non-stop operation. For attaining these requirements, the new design philosophy for autonomous decentralized control system, called HAL (Harmonous, Autonomous and Localities) concept, has been proposed based on the biological analogy. The viewpoint of this concept is that it is quite normal for a system to have failed parts. Sufficient conditions for an autonomous decentralized control system are given that every subsystem is uniform and equal in function and structure, and utilizes only local information for control and coordination. As one of the applications to the system components of this new concept, ADL-Net (Autonomous Decentralized Loop Network) has been developed, where fault tolerance of the system is attained by giving autonomy for fault detection, recovery and transmission to every network control processor. The HAL concept has also been applied to the train traffic control system for subways with three intrinsic requirements for supporting their non-stop operations.