Reliability Modeling Of PMS With Time Redundancy Based On Petri Net

Phased-Mission Systems is an effective tool to describe complex system.With the complexity of engineering applications,complex system not only has the features of multi-phase,but also has time redundancy and phase backup.Therefore,Phased-Mission Systems with time redundancy appears.The system has many phases,complex structure and the feature of time redundancy.Analytical method is difficult to accurately evaluate the task reliability of the system.Petri net has the capability of mathematical analysis and description of complex structure,and can evaluate the reliability of Phased-Mission Systems by simulation.For the reliability modeling problem of Phased-Mission Systems with time redundancy,this paper gives the concept of time redundancy and defines the type of time redundancy.In order to reduce the difficulty of task reliability modeling and provide reliability information input for modeling,this paper establishes the Do DAF-ROD product set that describes the reliability information of system,and gives the UML product template;This paper establishes a Petri net model of "unit-layer,system logic-layer and mission-layer" through hierarchical modeling.Unit-layer Petri net describes the idle state,working state,fault state and condition of state transition of unit.System logic-layer Petri net describes the system logic structure of each phase.Task-layer Petri net model describes the task execution process and the influence of system function fault information on mission success or failure.This paper also studies the mapping rules between the reliability description model and the task reliability model,and the transformation steps of some models.Finally,an example is given to verify the effectiveness of the modeling method.