Design Of Analog Circuit Fault Diagnosis System Based On Fault Dictionary Technology

With the rapid development of Electronic information age,the transistors and large-scale integrated circuits also have a great and fast evolution.This kind of high-speed development made integrated circuits smaller and smaller,testing and inspection of integrated circuits more and more arduous,and the fee of testing and inspection to integrated circuits become more and more immense.At present,most of integrated circuits’ constitution are digital circuits and analog circuits,and in some field,analog circuits maybe comprise integrated circuits.In comparison to digital circuits fault diagnosis,analog circuits fault diagnosis is more abstruse,the reason is that when components in a fault state of digital circuits,the corresponding circuit pin will output high level or low level.In analog circuits,unfortunately,is totally different,even though one of the components is not effective,the output still work,and the signal of output doesn’t change significantly.Now there is mainly two research strategies on analog circuits fault diagnosis which are Simulation Before Test and Simulation After Test,this dissertation studied analog circuits fault diagnosis problem intensively based on fault dictionary technology that belong to Simulation Before Test.Firstly,the problem of test point selection to fault dictionary technology is proposed,and introduced several classical strategies which are Entropy Based Strategy,Graph Search Based Strategy,Genetic Algorithm and Particle Swarm Optimization algorithm on this problem,then analysed merits and defects of these approaches with circuits simulation experiments and static experiments.Then based on the experiments results,this dissertation proposed Artificial Immune Algorithm method to test points selection problem,and the simulation results indicate that Artificial Immune Algorithm not only get the global optimal solution of test point selection but the time overhead of the selection progress has descended.In order to realize fault diagnosis in real circuits,the rational Print Circuit Board with Micro Control Unit STM32F103ZET6 is designed,then Embedded Real Time Operation System μC/OS-Ⅱ is chosen to be the system of the MCU.In this dissertation the reasons thatμC/OS-Ⅱ with fine real-time are analysed based on μC/OS-Ⅱ program core.Then effective human machine interface is designed with STemWin based on μC/OS-Ⅱ,with the human machine interface,the progress of circuits fault diagnosis became more intuitive and friendly.Aiming at the problem of obtaining alternating voltage’s amplitude,Fast Fourier Transform Algorithm is introduced in this dissertation.The formula of FFT is deduced firstly and the time saving reason of FFT is given,the effectiveness of FFT is verified with Matlab simulation and practical signal dealing.Finally,the Correlation Coefficient is introduced to solve the problem of existing deviation between practical voltage sequence and simulation voltage sequence,the Correlation Coefficient could quantificate the relationship of them,then the fault diagnosis system output the result from the consequence of quantification.The testing experiments demonstrate that the fault diagnosis system could diagnose the state of circuit accurately and effectively.