Safe and Reliable Computer Control Systems Concepts and Methods

The introduction of computers into safety-critical control systems lays a heavy burden on the software designers. The public and the legislators demand reliable and safe computer control systems, equal to or better than the mechanical or electromechanical parts they replace. The designers must have a thorough understanding of the system and more accurate software design and verification techniques than have usually been deemed necessary for software development. This document presents existing concepts and methods, relating to the design of software in safety-critical computer control systems. The concepts and methods dealing with fault avoidance, fault removal, fault tolerance, hazard analysis and safe design will be penetrated in detail. The document will enlighten the reader of what kind of realistic expectations the designer can form regarding the reliability and safety of a system’s software. The author of the document has concluded that it is not enough to, for example, solely rely on formal verification in order to achieve the necessary level of safety and reliability needed, but to use several concepts in union, like formal specification, testing, fault tolerance and hazard analysis.