Abstract:  Behavior in the time domain is critical to safety critical systems, if there was a fault, a large number of fault descriptions were related to the time between events. While the traditional fault tree does not have the ability to describe and analyse the time factor. On the basis of original definition of fault tree, semantic description of time constraint fault tree was added, a time constraint fault tree analysis method was put forward based on the extended semantic of the fault tree. The calculation rules of the time constraint logic gate and the event average transfer rate, the input event to the output event propagation rate and the intermediate event arrival rate are given. The propagation rate and arrival rate of the basic event and the minimum cut set of the fault tree were designed, and the algorithm was proposed to obtain the basic event time importance and the minimum cut set arrival rate for each node in the fault tree. The experimental results showed that the proposed timing analysis method can provide theoretical basis for fault diagnosis and prevention.

Key words: time constraint, fault tree, propagation rate, time importance