Application Of Weak Periodic Signal Detection Based On Stochastic Resonance

Weak signal detection(WSD)technology is widely used in computer image recognition,fault diagnosis,biomedical and other fields.The targets of WSD are the weak signals,which are overwhelmed by strong noise background.The traditional WSD methods are intended to suppress or attenuate noise,but also inevitably weaken the useful signal at the same time,thereby the detection effect is not ideal.Stochastic Resonance(SR)technology was first proposed by Benzi to explain the problems of periodically recurrent ice ages,it makes use of the interaction among the system,noise and signal to transform part of the noise energy to the low-frequency spectrum to enhance the signal,so the noise becomes useful.The unique signal processing method of SR has made it rapidly develop in both theoretical research and engineering applications.Based on a detailed introduction of basic theories and achievements of SR,this thesis studies the application of SR technology from two different application scenarios: fault diagnosis and tumor cell suppression.The main works and innovations of this thesis are as follows:(1)The applications of a new bistable SR system in bearing fault detection are studied.When traditional bistable SR system detects signal with low input SNR,it is difficult to tune the system parameters to the optimum.Aiming at this problem,a new MWS SR based on the combination of single-well potential and Woods-Saxon potential is proposed.Firstly,choosing the signal-to-noise ratio improvement(SNRI)as the measurement index,and the relationship between SNRI and the system parameters is analyzed.Then,the MWS system is applied to detect the high-frequency and low-frequency signals,and the detection effects are compared with the traditional bistable system.Finally,the MWS bistable system is applied to the bearing fault signal detection.The simulation results show that the MWS bistable system can effectively detect weak signals,and the results are better than that of traditional bistable SR system.(2)The SR behavior in a second-order under-damped linear system with nonlinear noise is investigated.By using the Shapiro-Loginov formula and Laplace transform technique,the analytical expression of the average amplitude gain of the system output is obtained.The resonance behaviors of the average amplitude gain are analyzed,and the validity of the theoretical analysis is verified by numerical simulation.Simulation results show that: the system presents more complex resonant behaviors by introducing the nonlinear noise,such as two-peak resonance phenomenon,which is not observed driven only by linear noise.All the results demonstrate that the character of the nonlinear noise plays a key role in system's resonant behavior.Therefore,by introducing nonlinear noise into the linear system,we can control SR in a reasonable range,and it has certain feasibility in practical engineering applications.(3)The SR phenomena in the tumor cell growth system with time delay is analyzed.According to the small time-delay method and adiabatic approximation theory,the expression equations of the mean first-passage time(MFPT)and signal-to-noise ratio(SNR)of the system are derived,and the relationship between SNR,noise intensity and various parameters of the system is analyzed in detail theoretically.Finally,the general intrinsic law of tumor cell growth is obtained by analyzing various SR phenomena,then the concept of treating tumor cells is given at the physical level.