A Petri Net Modeling Approach for Reliability of PMS with Time Redundancy

Abstract

Phased-mission system (PMS) has been widely used as mission reliability evaluation model of many engineering mission-critical systems. In practice, PMS can have two kinds of time redundancy. The first kind refers to the case that the time duration of a phase is longer than the minimum required operational time length, and the second kind occurs when a mission task failed in a phase can be executed once more in its following phase. Based on the Petri net, this paper proposes a general modeling procedure for reliability evaluation of PMS, which is capable of considering both kinds of the time redundancy in relatively intuitive way. Our proposed approach includes four main steps. First, we construct Petri net describing all possible execution paths of PMS to consider the redundancy by re-execution of a failed mission task. Second, we model the state evolution processes of system components. Based on the results, we then develop Petri nets depicting the change processes of system state for each phase and address the first kind of time redundancy. Finally, we complete the whole modeling procedure by integrating the previously obtained Petri net models. The approach is demonstrated with a simplified example system, and the resulting integrated model has clear modular structure, and can be evaluated by use of simulation.