“A fault tolerant architecture for brake-by-wire in railway cars”

Abstract

In this paper we will present a computer architecture suitable for distributed control systems where fault tolerance is desired. Today these are commonly referred to as "brake by wire" or "steer by wire" -systems. The architecture is designed for implementation mainly with standard components “off the shelf” (COTS). In particular there is only a comparable small device called FTCC (Fault Tolerant Communication Control) that requires extensive redundancy.

The FTCC is used to close control loops as tight to the controlled physical device as possible, gaining from the excess computing capacity that a distributed system offers but at the same time remove impact of increased fault intensity from an increased number of processing elements.

The architecture preferences applications where there is some kind of natural, inherent, redundancy. As a starting point, and a case, we consider a state of the art brake control system for railway vehicles. We recapture common computer architectures designed to handle safety critical applications and arrive at a feasible solution in the shape of a slightly modified distributed architecture. We then apply this revised distributed architecture and describe a revised brake control system.

The FTCC device has been implemented, however without redundancy, with standard VHDLtools and tested in a simulator environment. Results are promising and indicate that the FTCC-device has a great potential in future "control-by-wire" designs.

Keywords:

Control by Wire, Inherent redundancy, Fault Tolerance, Hard Real-Time requirements