Research On Weak Signal Detection Based On Stochastic Resonance System With Time-delay Feedback And Improved Potential Function

Weak signal detection technology is mainly used for weak signal recognition emerged by strong background noise.It is widely used and applied to fault signal diagnosis,speech recognition,biomedics and so on.So far,it has attracted a large number of attention from worldwide scholars.The core of traditional detection technology research is to study how to inhibit the noise energy to highlight the signal energy.However,while the noise energy is weakened,it is inevitable that the signal energy is weakened which makes the detection effect low.Stochastic resonance(SR)technology,as a new type of weak signal detection technology,takes a different approach to transfer part of the noise energy to the low-frequency signal where the weak signal is located,to improve the system output signal to noise ratio(SNR).The thesis first introduces the relevant basic theories.Then it focuses on the effects of time-delay feedback on the classical monostable SR system and exponential bistable SR system.Finally it studies an improved potential SR system,and the effects of time-delay feedback on the system.Following are the main contents of the thesis:(1)Based on the classical monostable SR system,the influence of time-delay feedback on the system is studied.Under the conditions of adiabatic approximation,using the theory of small delay approximation,the theoretical expressions of the steady-state probability density distribution,the equivalent potential function and the mean first pass time of the system are derived.The effect of parameters on the escape behavior of Brown particles is discussed through simulation experiments.The system's output SNR expression is further obtained using the two-state theory,and the influence of different parameters on the system's SR phenomenon is analyzed.Finally,a comparison test between experimental simulation and numerical simulation is performed,and the correctness of the theoretical derivation results has been verified.(2)The effects of time-delay feedback on exponential bistable SR system are studied.Through theoretical derivation,the theoretical expressions of the system's steady state probability density distribution,equivalent potential function,mean first pass time,and output SNR are obtained.Furthermore,the escape behavior of particles is studied through experimental simulation,and the influence of parameters on the SR phenomena is discussed.And the simulation results show that the introduction of time-delay feedback makes the system produce a more complex non-monotonic SR phenomenon.(3)An improved potential function SR system in weak signal detection technology is studied.Based on the traditional periodic potential function,an improved periodic SR(IPSR)system is obtained,and the IPSR system model under time-delay feedback is studied.The output SNR is used as a measurement index,and the influence of system parameters on the SR phenomenon of the IPSR system is analyzed through numerical simulation.Using the adaptive parameter optimization algorithm,the IPSR system and the IPSR system with time-delay feedback are applied to weak signal detection and the bearing fault detection to verify the effectiveness and engineering practicability of the system.