Petri Nets-based Fault Diagnosis Techniques With Applications To Hydraulic System

As the technique development of modern computer, test and measurement, signal analysis and artificial intelligence, the technology of mechanical equipments state inspecting and fault diagnosis (FD) come into a new phase. Petri-based fault diagnosis technique of equipments just start, its theory system is not set up integrally and practical applications are few. So a systematic and deep study on Petri nets-based fault diagnosis techniques is made in this dissertationThis paper integrates Petri nets, knowledge-based intelligent diagnosis and module design theory after summarizing domestic and overseas research, study the FD system structure from the point of integration, provides theory guidance for fault diagnosis of complicated equipments system, develops a intelligent diagnosis software based on Petri nets and promote the development of FD system to standardization, intelligentize modularization and integration. The following research has been done.According to the characteristic of equipments fault propagation, model of Petri nets is innovated and mathematics description is given for FD field. Fault Petri nets is pure net without conflict and contact; also modeling methods of Fault Petri nets is discussed, this paper adopts indirect modeling method that translating the production rules system to Petri nets model. Some literatures have not considered the fact that fault symptoms do not disappear after fault propagate when using the traditional Petri nets way to transform the fault tree model into Petri nets model, it is not congruous with fault propagation. This Paper transform fault tree model with Fault Petri nets and the result show that Fault Petri nets are suitable for the dynamic analysis.Anomaly rules problem in rule-based system is discussed and its verification criterions are presented for diagnosis system based on the colored Petri nets (CPN). The modeling and analyzing methods can also apply in other domains though the validating example belongs to hydraulic knowledge base.