Abstract: Solar array drive assembly, as an important part of the spacecraft, the research on its reliability is very important for fault occurs frequently. The fault tree of the solar array drive assembly is established based on the structure and principle of solar array drive assembly. Taking into account the both failure phenomenon of solar array drive assembly and many uncertainties exist in the fault status and fault reasons, fuzzy sets theory is introduced into dynamic fault tree. The failure parameters of bottom events for solar array drive assembly are modeled by triangular fuzzy numbers. Furthermore, the fuzzy dynamic fault tree analysis method for solar array drive assembly based on combination  cut set theory and interval arithmetic is proposed. The system weak parts and key components can be found easily according to the fuzzy probability importance which is comes from the fuzzy probability of system top event and fuzzy probability importance of bottom events. The results show that the bearings and harmonic drive are key components for the solar array drive assembly.

Key words: Fuzzy dynamic fault tree, Fuzzy probability importance, Markov model, Reliability, Solar array drive assembly