Detection And Circuit Realization Of Weak Periodic Signal Based On Chaos Oscillator In Mechanical Fault Diagnosis

Chaos is common in nature, in recent years, chaos theory has been concerned in variousfields for its unique performance. Chaos system can detect the weak periodic signal under strongnoise based on its sensitivity to small periodic signal and its immunity to noise, thus makes itsfoundation in the field of signal detection. This paper is carried through according to the study ofchaos theory and supported by natural science foundation of China (50875070):“The weak signaldetection and processing technology in mechanical fault diagnosis based on nonlinear theory”.The main contents of this paper are as follows:The first chapter details the significance and background of the subject, introducing theorigin and development of chaos theory and the history and current status of weak signaldetection, bringing up the main problem researched and solved in this paper at last.The second chapter introduces the basic concepts of chaos briefly, then introduces severaltypical chaotic models and the basic characteristics of chaotic motion. Besides that, this chapterintroduces several research methods about chaos and analyses the criteria of chaos. Through theintroduction of the knowledge of chaos theory, we have a clearer understanding of chaos theory,laying foundation for weak signal detection involved in the following chapters.The third chapter details the theory of weak signal detection based on chaos theory. We selectDuffing oscillator as chaos model and analyses its internal dynamics. We testify its sensitivity tosmall periodic signal and its immunity to noise through simulation and calculation. Then, wemodify Duffing oscillator equation to enable it adapt to detect weak sine signals with differentfrequency under strong noise. We design simulation circuit with EWB according to the improvedequation and make a detection circuit based on the success in the simulation, building anexperimental platform. We do control experiments to the system with different frequencies sinesignals respectively and detect weak sine signal under strong noise, achieving the detection ofperiodic harmonic signal through sweeping with LabVIEW.In the fourth chapter, we get a mathematical model which can detect periodic pulse signalthrough modifying typical Duffing equation. Then we construct simulation model of chaossystems which can detect periodic pulse signal according to the modified equation. That showstheoretically that the system can detect weak periodic pulse signal under strong noise.