Reliability Assessment of Control Systems

Actually modern systems have to ensure higher and higher operating standards, thus including monitoring and control subsystems for their achievement. In safety critical systems control is a crucial task in order to satisfy strict reliability requirements. But it is also necessary that the control system is itself reliable. As a consequence, adequate techniques are necessary in order to perform reliability evaluation of both the controlled and the control systems. Techniques that therefore should avoid over-simplistic assumptions and/or approximations that, for example, are usually introduced when dependencies, interferences and other dynamic reliability aspects are not taken into the right consideration. In this paper, a technique for carefully evaluating the reliability of such systems, also considering dynamic aspects and behaviors, is proposed. Firstly the technique is detailed through the specification of the dynamic reliability block diagrams notation, and therefore in order to demonstrate its effectiveness, it is applied to an example of a computing-based control system taken from literature, thus providing guidelines for the reliability representation and evaluation through DRBD.