Reliability Of Phased-mission Systems Research Articles

Reliability modeling and configuration optimization of a photovoltaic based electric power generation system

Existing research on phased-mission system reliability has mainly focused on internal failures. However, some practical phased-mission systems such as photovoltaic based electric power generation systems can also be subjected to external impacts. This paper models the reliability of a photovoltaic based electric power generation system considering both internal failures and external impacts that affect the failure rate of photovoltaic modules. Two different cases are considered when modeling the system reliability, where the number of elements required during different phases are the same in the first case and the number of elements required during different phases are different in the second case. The configuration of photovoltaic arrays as well as protection efforts on each photovoltaic module are further optimized to improve the system reliability. Moreover, the expected system loss is also modeled and optimized when the system demand is not satisfied. Examples are presented to illustrate the applications of proposed models.

Reliability Analysis of Phased Mission Systems When Components Can Be Swapped Upon Failure

Abstract This paper proposes a new strategy to improve the reliability of phased mission systems (PMS), namely, by swapping of components. In the proposed strategy, when a component fails, it can be swapped by another one in the system which is still functioning. We consider both the options to swap components at any time and for swaps to be possible only at phase transitions. This paper also discusses the strategy of swapping components according to structure importance. The structure importance is used to measure the importance level of the components in contributing to system reliability. Then, when a component with high importance fails, it is swapped by another component with lower importance from the system which has not yet failed. The survival signature methodology is implemented to assess the reliability of PMS when there is a possibility of components swapping. In addition, we consider the cost effectiveness of component swapping through two models (time independent and time dependent) of penalty costs for PMS.

A Reliability Synthesis Method for Complicated Phased Mission Systems

Phased mission systems are very common in engineering practices. It has been a challenging task to effectively estimate the reliability of phased mission systems. In the paper, a new reliability synthesis method for phased mission systems is proposed for addressing the challenge. Based on the existed reliability block diagram, the hierarchical synthesis framework of the reliability can be built. The reliability synthesis algorithms for the same level and hierarchical level are respectively presented. Component reliability is the input of the reliability synthesis as the lowest level of the framework, which can be obtained by data-driven method or physics of failure method. The reliability estimation method for three lifetime distribution types is given. The effectiveness of the proposed method is testified and demonstrated by a complicated phased mission system.

Variance-based importance analysis measure for mission reliability of phased mission system

ABSTRACTImportance measures are used to estimate the relative importance of components to system reliability. Phased mission systems (PMS) have many components working in several phases with different success criteria, and their component structural importance is distinct in different phases. Additionally, reliability parameters of components in PMS always have uncertainty in practice. Therefore, existing component importance measures based on either the partial derivative of system structure function or component structural importance may have difficulties in PMS importance analysis. This paper presents a simulation method to evaluate the component global importance for PMS based on the variance-based method and the Monte-Carlo method. To facilitate the practical use, we further discuss the correlation relationship between the component global importance and its possible influence factors, and present here a fitting model for evaluating component global importance. Finally, two examples are given to show that the fitting model displays quite reasonable component importance.

Bayesian Networks Based Reliability Analysis of Phased-Mission Systems

The paper presents a Bayesian networks(BN) framework for the reliability analysis of phased-mission systems(PMS),named PMS-BN model.A PMS consists of consecutive and non-overlapping time periods,with system configuration,success criteria,and component behavior varying from phase to phase.Firstly,each phase is represented by a BN framework,named phase-BN.Then,in order to figure the dependences across the phases,all the phase-BN are combined by connecting the root nodes that represent the same component but belong to different phases,and connecting the leaf nodes of phase-BN with a new node representing the whole PMS mission.The new constructed BN is called PMS-BN.In PMS-BN model,each phase time is divided into m segment,and the reliability analysis of PMS is performed by a discrete-time BN model acting on PMS-BN.Two examples are used to expatiate on the proposed approach.The PMS-BN based method provides a new efficient way to analyze the reliability of PMS,especially for those with dynamic phases.Moreover,it is also applicable to system diagnosis and sensitivity analysis.If all the non-root nodes in constructed PMS-BN own not more than 2 father nodes,the computational complexity of evaluating the PMS reliability is O(Nm3),where N is the number of non-root nodes.

Phased-mission system reliability under Markov environment

The authors show how to determine the reliability of a multi-phase mission system whose configuration changes during consecutive time periods, assuming failure and repair times of components are exponentially distributed and redundant components are repairable as long as the system is operational. The mission reliability is obtained for 3 cases, based on a Markov model. (1) Phase durations are deterministic; the computational compact set model is formulated and a programmable solution is developed using eigenvalues of reduced transition-rate matrices. (2) Phase durations are random variables of exponential distributions and the mission is required to be completed within a time limit; the solution is derived as a recursive formula, using the result of case 1 and mathematical treatment-a closed-form solution would be prohibitively complex and laborious to program. (3) Phase durations are random variables and there is no completion time requirement; the solution is derived similarly to case 1 using moment generating functions of phase durations. Generally, reliability problems of phased-mission systems are complex. The authors' method provides exact solutions which can be easily implemented on a computer. >

Reliability evaluation of a phased mission system with time varying redundancy and failure probability

An attempt is made to derive the closed-form mathematical expression of a phased mission system reliability. A system is considered, where failure probability of a component and number of added redundancy change during the mission time. Several performance measures are also suggested.