Reliability of phased mission systems with warm standby subsystems

Abstract

With the development of technology, sensor networks, and non-conventional power generators, weapon equipments become more and more complex, and their missions become more and more diversified. Further, many real world systems operate in phased-missions where the system requirements and success criteria vary over consecutive time periods, known as phases. For mission success, all phases must be completed without failure. In order to ensure accomplishing missions successfully, many subsystems adopt redundancy techniques to improve the mission reliability. Particularly, redundancy is an effective method to improve the reliability of mission critical systems. Hence, there is a great need for accurate and efficient reliability evaluation of phased mission systems with phase dependent redundancy configurations and requirements. This paper presents a new method for reliability analysis of phased-mission systems with warm standby subsystems. In the analysis, multiple sub-systems were considered where each sub-system uses warm standby redundancy. The operational and standby failure rates of a component can vary with the phases. Similarly, the configuration of each subsystem can vary with the phases. The proposed algorithm is developed based on: (1) a modularization technique, (2) an easily computable closed-form expressions for conditional reliability of warm standby sub-systems with phased dependent success criteria, and (3) a recursive formula for accounting the dependencies of sub-systems across the phases. As cold and hot standby configurations are special cases of warm standby configuration, the proposed method is also applicable for analyzing the phased mission systems with cold and hot standby redundancies. The reliability evaluation algorithm is illustrated using an example of fault tolerant computing system.