Common cause failure analysis of fault tolerance systems with diversity defense mechanism

Common cause failures (CCF) are a serious threat to redundant system reliability. It is therefore important to quantify and model CCF in reliability assessments. Design diversity has long been used to protect redundant systems against CCF. However, it is difficult to quantify the effects of diversity on system reliability. Therefore, a novel method based on Root Cause (RC) and Coupling Factor (CF) is proposed to assess diverse redundancy system reliability in this paper. The key idea of the novel method is to classify the RCs into (sub-)categories and then assess the corresponding CFs between redundant components respectively based characteristics of diversity. A novel CCF model is proposed to describe the relationship between CCF probability and diversity. Finally, aiming at the CCF induced by external environment stress an example is given to illustrate the usage of the novel method.