Investigation On The Order Based Modal Analysis Of Rotating Machinery And Software Implementation

Rotating machinery is widely used in various industrial occasions.Identifying the modal parameters of the rotating machinery in the operating state is helpful to solve the problems of fault diagnosis,vibration reduction and product optimization.The traditional Operational Modal Analysis(OMA),based on the assumption of white noise excitation,does not need to measure the excitation force,and only needs to measure the vibration response signal of the structure in the operating state to identify modal parameters.However,the excitation of rotating machinery in the operating state is mainly excited by harmonics with frequency multiplies of its rotating speed.The assumption of white noise excitation is not satisfied.The OMA method is limited in the modal parameters identification of rotating machinery.The Order Based Modal Analysis(OBMA)method is researched in this paper.The OBMA method considers that the measured response is mainly caused by rotational excitation during a run-up or run-down test.The order tracking method is combined with OMA to identify modal parameters of rotating machinery.The thesis finished the following work:(1)The basic theory of Order Based Modal Analysis is studied.This method combines the order tracking method with the OMA method to identify modal parameters.Two order tracking methods are studied: angular domain sampling based order tracking(AD-OT),Vold-Kalman filter order tracking(VKF-OT);and the basic principles of the Poly-reference Least-Squares Complex Frequencydomain method(Poly MAX)is studied.(2)The software named OBMA is developed,including functions of pre-processing of timedomain data,AD-OT,VKF-OT,the establishment of structure's geometric model,Poly MAX modal parameter identification,mode animation display and modal verification.In addition,the low-pass variable frequency band filtering of the signal is realized by using the stationary wavelet transform,and the problem of averaging or combing of multiples test data is also solved.The software interface is neat and human-computer interaction is good.(3)The OBMA method is performed on the acceleration response of a thin plate with known modal parameters under harmonic excitation,and the modal parameters of the thin plate are compared with the simulation values to verify the correctness and effectiveness of the OBMA method.All functions of the software are applied,and the results prove that the software runs stably and the results are reliable,which can be easily applied to the modal analysis of rotating machinery.(4)The influence of the sweep rate on the resonance peak is studied to determine how to select the angular acceleration during experiment.How to choose the speed increment,order resolution in AD-OT and the filter order,bandwidth in VKF-OT is studied.The application occasions of the two order tracking methods is researched,providing a reference for the parameter selection in experimental data analysis and processing.(5)The vibration test of the blade rotor test rig is performed.The acceleration signals of a total of84 channels are measured and the OBMA method is performed on these signals.The modal parameters of the blade rotor test rig are obtained.