After analyzing the dynamic characteristics of multistage processes

new qualitative description model—process dynamic signed directed graph (PDSDG) was proposed by introducing the stage conditions to unmeasured nodes in SDG.The modeling method and a D matrix-based diagnosis method were given.The proposed model can meet the demand of adjustment along with the conditions

and the diagnosis method disposed the nodes that were not online observed.PDSDG had better resolution than static SDG by comprehensive consideration of different stage diagnosis results.Finally

the fault diagnosis model of an aircraft engine bleed system was built with the proposed method.The case results proved the effectivity and utility of this model.)