Research On Extraction And Fault Diagnosis Of Fluctuating Speed Components Of Hydraulic Equipment

With the advantages of fast response,stable output,high power density,easy to realize stepless speed regulation and strong adaptability to complex working conditions,hydraulic equipment has been widely used in engineering construction,national defense,metallurgical mines,material processing and other equipment with complex working conditions.In recent years,in order to meet the requirements of high precision and intellectualization in modern industrial production process,hydraulic equipment has begun to develop in the direction of refinement,complexity,integration and informatization.Under the influence of strong coupling and strong ambient noise,the traditional analysis method will make the feature information very weak and difficult to identify,which makes the research of operation condition monitoring and fault diagnosis technology of hydraulic equipment become a hot spot nowadays.The instantaneous speed signal of hydraulic equipment has the advantages of not interfering with the operation of the system,high signal-to-noise ratio and directly reflecting the kinematics information of the system.The research team found that the coupling effect of environmental conditions leads to the change of system parameters.These changes affect the change of dynamic stiffness of the system internally,and the change of instantaneous speed fluctuation externally.Therefore,this paper takes the hydraulic power system as the research object,studies the extraction method of the instantaneous speed fluctuation component based on Vold-Kalman time-varying filter,reveals the relationship between the performance state of hydraulic equipment and the speed fluctuation component,and provides a new method for the study of the monitoring technology of the hydraulic equipment operation condition with the speed fluctuation signal as the information source.The main contents of this paper are as follows:(1)Vold-Kalman time-varying filtering mathematical model and fast algorithm research.By constructing signal model,building structural equation and data equation,decoupling with least square filtering method,and then solving complex matrix equation by PCG method,the Vold-Kalman time-varying filtering method and algorithm are studied,and the design of VoldKalman time-varying filter is realized by MATLAB.Then,the validity and accuracy of VoldKalman time-varying filter are verified by simulation experiments,which lays a theoretical foundation for subsequent research.(2)Research on extraction method of speed fluctuation component based on Vold-Kalman time-varying filter.Combining STFT,time-frequency ridge extraction and binary refinement search,the instantaneous frequency estimation method is realized.On this basis,the feature extraction of speed fluctuation component based on Vold-Kalman time-varying filter is realized.By combining simulation with experiment,the validity and accuracy of this method are verified,which provides technical support for the following test of speed fluctuation component extraction aiming at condition monitoring of hydraulic equipment.(3)Comparing the performance of the methods studied in this paper with the existing methods based on zero phase order filter.The two extraction methods were compared in principle,process,parameter selection and actual effect.It is concluded that the method based on Vold-Kalman time-varying filter can retain more detailed information related to the operation status of hydraulic system and has higher accuracy.(4)Experimental study on extracting the fluctuation component of the speed of hydraulic power system.The validity of the method proposed in this paper is verified by experiments under constant and variable working conditions on the test platform of variable speed pumpcontrolled hydraulic motor.The results show that the rotational speed fluctuations caused by the unbalance of the rotor of the plunger motor and the plunger pump and the wear of the valve plate of the plunger pump can be extracted by the proposed method.The variation of these three components with speed and load is analyzed,which provides a new method for monitoring and fault diagnosis of hydraulic equipment with instantaneous speed fluctuation as signal source.