Research On Weak Signal Detection Of Stochastic Resonance Based On Modulation And Coupling

Weak signal detection technologies include a series of methods that can detect the weak signal submerged in the strong noise.With the development of the science and technology,weak signal detection technologies have been widely applied in many aspects of scientific research,society and life,such as wireless communication,biological science,medical diagnosis,fault signal detection and so on.Stochastic resonance(SR)is an important technology in the field of weak signal detection.To identify and detect the weak signal,SR transfers the energy of noise to weak characteristic signal based on the cooperation of nonlinear system,noise and signal.Thus,compared with the traditional weak signal detection technologies,the significant advantage of SR is that it can change the noise in signal detection from harmful component to useful component.This is also the reason why SR is worthy of a profund study.Based on the basic theory of SR,this thesis studies the application of SR in weak signal detection from three aspects: the single-sideband modulation method,the strong coupled system and the harmonic oscillator system with damping fluctuation.The main work and innovations are as follows:(1)In order to overcome the limitation of adiabatic approximation in the traditional SR method,a Hilbert single-sideband modulation method combined with the under-damped system is studied.Firstly,the method is analyzed and studied from three aspects: the small sampling frequency,the large sampling frequency and the selection of baseband signal.Then the researched method is applied to the diagnosis of actual bearing fault signals,and it proves that this method can effectively detect the high frequency fault signals of the inner and outer rings of actual bearing.(2)The strong coupled Duffing and Van der Pol oscillators system(hereinafter referred to as D&V strong coupled system)is studied.The study found that,under the background of trichotomous noise,the system parameters have an important effect on the mean signal-to-noise ratio increase(MSNRI)of the system.Finally,the proposed system is used in the fault signal diagnosis of HRB6205 open bearing,and it is found that the D&V strong coupled system can effectively detect the fault signals of the inner and outer rings of the bearing and has better side frequency suppression effect than the classical bistable system.(3)The SR of fractional order coupled harmonic oscillator with damping fluctuation in the binary noise is studied.Firstly,with Shapiro-Loginov equation and Laplace transform method,the theoretical expression of the output amplitude gain(hereinafter referred to as G)of the system is derived.Secondly,the simulation results show that there are abundant SR phenonmena in the system,and changing the system parameters has an important impact on the resonance behavior and the G.Finally,the numerical simulation of the system differential equation was carried out by Euler algorithm,and verifing the accuracy of the theoretical results.