Rigorous development of a safety-critical system based on coordinated atomic actions

Abstract

This paper describes our experience using coordinated atomic (CA) actions as a system structuring tool to and validate a sophisticated control system for a complex industrial application that has high reliability and safety requirements. Our study is based on the Fault-Tolerant Production Cell, which represents a manufacturing process involving redundant mechanical devices (provided in order to enable continued production in the presence of machine faults). The challenge posed by the model specification is to a control system that maintains specified safety and liveness properties even in the presence of a large number and variety of device and sensor failures. We discuss in this paper: i) a for a control program that uses CA actions to deal with both safety-related and fault tolerance concerns, and ii) the formal verification of this based on the use of model-checking. We found that CA action structuring facilitated both the and verification tasks by enabling the various safety problems (e.g. clashes of moving machinery) to be treated independently. The formal verification activity was performed in parallel with the activity the interaction between them resulted in a combined exercise in design for validation.