Reliability Modeling And Assessment Of Phased-Mission System With Performance Balancing And Failure Competing Mechanisms

Phased-mission systems(PMSs)with sophisticated failure modes could behave with diverse mission performance levels.With the increasing complexity and diversity of customer requirements,engineers have become increasingly interested in the reliability of each mission.However,two difficulties of reliability assessing of phased-mission systems arise:(1)multiple competing failure modes of components occur in the same phase and vary across phases,and(2)different subsystems need to satisfy performance balancing requirements phase by phase.Conventional phased-mission system reliability models often make single-phase competing assumptions that do not satisfy the requirements of practical applications.To remedy the limitations of traditional methods,this thesis aims to address the reliability modeling and assessment of PMSs with the competing failure and balancing mechanisms.Meanwhile,the proposed method is to be extended to assess the mission reliability of a multi-sensor target tracking system.The contributions and innovations of this thesis are summarized below:(1)A reliability modeling and assessment approach of phased-mission system by state space model is introduced.A phased continuous-time Markov chain(CTMC)is used to model the system state degradation process and determine the cross-phase state mapping relationship.The state transfer equation is solved by the Laplace method,and the state probability distribution is calculated phase by phase to obtain system’s mission reliability.Two cases indicate that the method can be applied on small scale phasedmission systems.(2)A reliability modeling and assessment method of phased-mission systems with cross-phase competing failures is proposed.The system reliability model is constructed by the phase-equivalent binary decision diagram,and together with the divide-andconquer strategy.The complexity of the model is effectively reduced by reusing the intermediate results of the previous phase.The results show that the proposed mission performance analysis method has higher computational efficiency than existing combinatorial models.(3)A reliability modeling and evaluation method for phased-mission systems including performance balanced requirements is proposed.Three balanced criteria are defined for the performance balance requirements of phased-mission systems with multiple functional sectors.The competing imbalance modes of the system in each phase can be established based on the criteria,and the CTMC imbedding model is constructed in each phase.An unrestricted rebalanced mechanism is introduced to guarantee the dynamic balance and improve the system reliability.The results show that the method can effectively model and evaluate the reliability of a phased-mission system with performance balanced requirements.