Study On Fault Diagnosis Of Rolling Bearing Based On Angle-domain Cyclostationary

With the development of science and technology,mechanical equipment is becoming more and more large,complex and precise which playing an important role in people's life.In the rotating machinery,the bearing and gear as the key parts of shaft play important roles in rotating machinery.The normal operation of rotating machinery is largely dependent on the normal operation of bearings and gears.Early detection and prediction of bearing and gear failure will bring great benefits and it can avoid the loss of life and property caused by mechanical failure at the same time.Therefore,it is very important to monitor and diagnose the running state of the bearing and gear.In this paper,the vibration of the bearing and the gear is taken as the research object,after consulting a large number of domestic and foreign literatures and analyzing the actual data,it is found that the rotating machinery is always in a state of unstable rotation speed,especially when there is a defect.However,the time based acquisition method is based on the stable experimental object,which will affect the measurement results and the accuracy of the data analysis.Therefore,combined with the unstable motion of rotating machinery,this paper presents a data acquisition and analysis method based on angle-domain,in order to correct the error.Furthermore,the signal is reconstructed from angle-domain to time-domain signal by the method of equivalent rotation speed,so that the signal is universal.At the same time,it is found that after angle-domain resampling,the vibration signals have the cyclostationary property.Then,by combining the angle-domain resampling method and cyclostationary theory,a new model of bearing and gear based on angle-domain is established.By analyzing the characteristics of the bearing and gear cyclostationary,we can recognize the early fault.Finally,the accuracy and correctness of the method based on the angle domain is verified by the simulation signal,rotating machinery fault diagnosis platform and engineering examples.The result shows that the method can realize the early fault diagnosis of bearings and gears,and summarize a set of diagnostic procedures for cyclostationary methods.First,this paper introduces the definition of cyclostationary signal,and gives the first order and two order analytic function theory and calculation method,this paper also gives some properties of cyclic spectral correlation density function,include support field of cyclic spectrum and sampling theorem based on cyclostationary signal.These provide theoretical basis for the subsequent theoretical analysis and experimental analysis.Second,this paper analyzes the operation state of bearing,gear and rotating equipment.It is found that there are some limitations in the current acquisition method based on time-domain.In order to solve this unstable state,a data acquisition method based on angle-domain is proposed.And then with an experimental comparison,discusses the data acquisition method based on angle-domain is better than that based on time-domain in vibration signal acquisition process.It is proved that this method is more reliable.It is an effective method to avoid the non-stationary signal in the time-domain and it can be applied in practice.Third,by analyzing the characteristic of rotating fault,it is found that the characteristic consistent with the cyclostationary,and then a stochastic model is established.By using Wold isomorphism,we prove the completeness and periodicity of cyclostationary.After consulting a large number of literature and experimental analysis,we found that the frequency modulation and amplitude modulation may occur when the rotating machinery is in vibration,especially when the fault occurs,and there may be a number of modulation sources.In view of this situation,the superiority of the cyclostationary method is proved by the simulation signal.Finally,a mathematical model of the cyclostationary of bearing and gear is established.Combined with its characteristic frequency and fault characteristics,this paper presents the characteristics of cyclostationary density spectrum of bearing and gear fault,which provides a theoretical basis for fault diagnosis.By comparing the data of the fault bearing,the rolling bearing fault bearing,the inner ring fault bearing and the outer ring fault bearing,and the comparison of the data of no fault gear,gear broken,gear crack,gear wearing and cyclostationary analysis of engineering signal after resampling.The feasibility,reliability and accuracy of the cyclostationary analysis method are verified.It is proved that the fault diagnosis method based on cyclostationary is reliable and accurate,and can be widely used in the fault diagnosis of shafting.By using cyclostationary theory,rotating machinery fault mechanism,angle-domain re-sampling method,modulation signal simulation analysis,bearing and gear cyclostationary modeling,fault diagnosis platform for experimental analysis and engineering examples,cyclostationary method is proved suitable for the fault diagnosis of rotating machinery and this method can identify of fault characteristics early,accurate and reliable.With the rapid development of Computer Science,in the future this method will certainly be able to be applied to the state monitoring and fault diagnosis of rotating machinery in order to provide security for machinery and equipment and the safety of life and property.