Research And Implementation Of Fault Diagnosis Of Simulated Circuit In Virtual Experiment System

Recently, research on virtual lab gets more and more concern. Virtual experiment can overcome the shortcomings of traditional experiment, make the procedure of experiment more convenient, make the investment less and make the maintenance easier. This thesis mainly discuss the research and implement of the virtual digital circuit experiment system in our virtual lab system—VLAB. One of the difficulties in virtual digital circuit experiment system is the implement of the fault diagnosis of simulated digital circuit. Fault diagnosis of simulated digital circuit consists of automatic fault diagnosis and manual fault diagnosis. It relates to the modeling of simulated circuit, the modeling of fault and design of virtual instrument. They will directly influence the performance and the convenience of the whole system. In this thesis, simulated circuit refers to software simulation of digital circuit. Through the research and analysis of digital circuit, it is can be found that using Petri net to model the simulated circuit is convenient. Petri net is a kind of combinatorial model which can be presented by graph and it is intuitionistic and easy to understand and use, so it is quite suitable for describing concurrent phenomena. At the same time, Petri net is a strictly defined mathematics object. In virtue of mathematics thinking, Petri net analysis method can be used for static structure analysis and dynamic behavior analysis. These characteristics make Petri net suitable for modeling and analysis of digital circuit.Therefore, we combine Petri net analysis method with software simulated circuit, put forward Petri net based simulated circuit model, Petri net based fault model and related test set generation method, test set simplification method.The traditional method of fault diagnosis is utilizing instrument, therefore, in our virtual digit circuit experiment system, virtual instrument is one of important parts. According to the implement of our system and the characters of virtual instruments, this thesis puts forward a hierarchical object-oriented structure model of virtual instruments, which made the modeling of virtual instrument simple and clear, and this model can be integrated into other parts of the virtual system. So, it simplifies the development of this virtual lab system, and realizes the character of reuse.