Applicability of Qualitative Reliability Analysis for Redundant Systems

In this paper we consider the problematic design of safety critical systems for future commercial vehicles. The development of such systems is mainly driven by the social demand that the citizens want to see safer, more reliable vehicles on the roads, which can also handle more complex situations than the human driver can. Redundant electronic systems confront us with new challenges in reliability analysis, since handling and defining their back-up strategies is not a straightforward task by means of using qualitative approaches. It is also questionable whether the well-known approaches of classical reliability theory are appropriate for redundant electronic systems, especially if they are of safety critical nature, such as the electronic brake system that has been used in commercial vehicles in Europe for almost a decade. The paper presents a less widespread and a more widespread technique through reliability theory, which enable the designer organizing functions and subsystems, failures and logical relationships between failures from the system level up-to the last component without missing any of them.