Solar Wing On The Driving Mechanism Of Dynamic Fault Tree Analysis

Long lifetime and high reliability of spacecrafts is pursued unremittingly in the booming space technology. It is of engineering practical significance to research the reliability of the solar array driving assembly (SADA), which is a vital component of spacecrafts. The fault tree method provides a compact and graphical reliability analysis. A limited number of research works have been devoted to the systematic fault tree analysis to SADA. The conventional fault tree theory cannot model the SADA system, which employs spares and dynamic redundancy management to achieve high level of reliability. In this paper, the dynamic fault tree analysis to SADA is investigated considering the following aspects.First, based on the detailed analysis of the basic functions, working principle, and structure, SADA model is constructed using a dynamic fault tree. A modified module searching algorithm is proposed, which can be used to modularize the dynamic fault tree of SADA in order to reduce the time complexity of dynamic fault tree analysis. The minimal cut sequences/sets of the dynamic/static modules are generated using Markov chain or binary decision diagram, respectively. The minimal cut sequences of the system, generated by the modular synthesis algorithm of the minimal cut sequences/sets, are analyzed according to the proposed comparison principle of the minimal cut sequences/sets.Second, the dynamic fault tree of SADA is quantitatively analyzed. The general formula of the Markov chain with different lengths is deduced under normal circumstances. The warm spare model based on the condition probability is proposed, to which the cold spare model is deduced accordingly. The top event occurrence probability of dynamic/static modules is solved by various methods and the algorithm to solve the top event occurrence probability of dynamic fault tree is proposed through comparing various methods. Using this method, every sub-tree of dynamic fault tree can be solved immediately. The probability importance, structure importance, and critical importance of all basic events in the system are analyzed, the components to improve are identified, and how to improve the system is suggested.Finally, taking the uncertainty of the failure rates of the basic events and the top event occurrence probability into account, the fuzzy sets theory is introduced for dynamic fault tree analysis. The triangular fuzzy numbers are used instead of crisp values to represent the input parameters in the system. Combining A-cuts and interval operators, the top event fuzzy occurrence probability of the system and the fuzzy probability importance of every basic event are calculated. The fuzzy probability importance is ranked according the comparison of fuzzy numbers, the components to improve are identified and how to improve the system is suggested.