VLSI implementation for control of critical systems

Abstract

Self-checking integrated circuits, i.e. able to detect its own errors, are not adequate to control the actuators of critical systems used in railway transportation, space, chemical and nuclear industries. Only the conventional fail-safe circuits can apply these needs, unfortunately they cannot be implemented in integrated circuits technologies and thus they cannot be used to realise complex systems.This paper deals with a method to solve this problem. We present briefly the theory of generalized fail-safe systems which includes new, more general definitions, construction conditions and basic properties for fail-safe systems. Then, in order to take into account the problem of undetectable faults, we define strongly fail-safe circuits who achieve the totally fail-safe goal. As an application we propose a fail-safe integrated interface which transforms the outputs of self-checking systems into signal adequate to drive electromechanical actuators and such that the whole system, self checking processing part and interface, implemented in VLSI is strongly fail-safe. Therefore this system can be used for safe drive of complex critical processes.