Applications Of Coupled, Tri-stable And Power Function Type Stochastic Resonance Systems In Weak Signal Detection

Weak signal detection technology has been widely used in biomedicine,fault diagnosis,and so on,and its detection object are the weak signals which can't be detected by conventional methods.There are many methods to extract weak signals,most of which are realized by suppressing the noise.However,the stochastic resonance method is the opposite.Stochastic resonance(SR)is a nonlinear phenomenon where the weak signal can be enhanced and the noise is weakened through the interaction among a nonlinear dynamic system,weak signal and noise.SR can detect the weak signal effectively.Therefore,SR is the hotspot in weak signal detection technology.On the basis of introducing the basic theory of SR and the achievement which has been made in weak signal detection,from SR system point of view,the weak signal detection methods based on different SR systems are researched mainly in this thesis.The main contents are as following:(1)The coupled bistable stochastic resonance system and its application in weak signal detection are studied.Firstly,the coupled bistable stochastic resonance model and its characteristics are analyzed.Then,the numerical analysis method is studied,and the average signal-to-noise ratio gain is selected as the indicator to measure the stochastic resonance system's performance.The optimal coupled coefficient r can be chosen by adaptive algorithm.Finally,the single-frequency and multi-frequency weak signals can be detected based on this system.(2)The tri-stable stochastic resonance system and its application in weak signal detection are studied.Stochastic resonance system is an effective method to extract weak signal.However,system output is directly influenced by system parameters and noise intensity.Aiming at this,the Levy noise is combined with a tri-stable stochastic resonance system.The average signal-to-noise ratio gain is regarded as an index to measure the stochastic resonance phenomenon.The characteristics of tri-stable stochastic resonance under Levy noise are analyzed in depth.Firstly,the stochastic resonance characteristics of the tri-stable system are introduced in detail,the signal-noise ratio of the system under Gaussian White Noise is derivated and the method of generating Levy noise is explained.Then,the effects of tri-stable system parameters w,a,b,and Levy noise intensity amplification factor D on the resonant output can be explored with different Levy noises.Finally,the tri-stable stochastic resonance system is applied to the bearing fault signal detection.For comparison,the classical bistable stochastic resonance system under the same conditions is chosen.(3)The power function type bistable stochastic resonance system and its application in weak signal detection are studied.Combining the power function type single potential well model and Gaussian Potential model,a novel bistable stochastic resonance system is proposed,which is called power function type bistable stochastic resonance system.Firstly,the average signal-noise ratio gain is taken as the measurement index,an algorithm for searching the optimal system parameter combination is proposed,which makes the weak signal,noise and system produce optimal resonant effect.Then,the power function type bistable stochastic resonance system is used to detect the simulated signal under Levy noise background.For comparison,the classical bistable stochastic resonance system under the same conditions is chosen.(4)Combining wavelet transform and power function type bistable stochastic resonance,a weak signal detection method based on wavelet transform and power function type bistable stochastic resonance system is studied and applied to bearing fault signal detection.Firstly,the bearing fault signals which don't meet adiabatic approximation are pre-processed by twice sampling.Then,the pretreated signals' decomposition and reconstruction are processed based on wavelet transform.Finally,the reconstructed signal is input to power function type bistable stochastic resonance system,and then the fault characteristic frequency can be detected.