Phase Differential Encoder Theory And Its Application On Planetary Gear Set Fault Diagnosis

Instantaneous angular speed(IAS)is directly related to the mechanical dynamic behaviors,and reflects the inherent signatures such as posture,operating status,and characteristic frequencies.Comparing to traditional vibration signal analysis methods,the IAS analysis methods overcome the complex modulation and frequency-aliasing phenomenon due to the non-stationary operating conditions.Therefore,the mechanical fault diagnosis theory and method based on IAS are popular,especially in the planetary gear set fault diagnosis.However,the measured IAS signal contains the “real” IAS components due to mechanical dynamic behaviors,besides,it also contains the full frequency-domain "false" IAS components due to width error of pulse and "false" IAS components at rotating order harmonics due to the encoder manufacture and installation errors.These "false" IAS components usually mask the weak “real” IAS mechanical dynamic behaviors,and restrict the recognition accuracy of planetary gear train fault diagnosisThis dissertation aims to solve the problem that the IAS based fault diagnosis accuracy is influenced by full frequency-domain and rotating harmonics “false” IAS components,the phase differential encoder(PDE)theory,IAS measurement error mechanism,IAS error suppress algorithm and IAS based fault diagnosis method are investigated.This PDE and its IAS measurement system are validated by experiments,it recognizes the planetary gear set fault locations and severities.The main research works of the paper include:(1)Aiming to the problem that conventional encoder IAS measurement has errors,considering the encoder errors and different IAS estimation approaches,IAS error mechanisms of time counting method and Analog-to-digital Convert(ADC)based method are investigated;an IAS mathematical model is developed to reveal the IAS error mechanism;quantitatively analyzed the IAS errors due to the low-pass effect,quantization error,frequency integration and aliasing phenomenon of time counting method and frequency demodulation method,and IAS errors due to encoder eccentric error,tilt axis error and randomly distributed gratings.A performance curve of frequency demodulation IAS estimation noise level is acquired.An encoder error model is developed considering manufacture and installation errors.The IAS error signatures are validated by the simulations and experiments,which provides a theoretical guide to IAS accurate measurement based on the encoder.(2)Aiming to the problem that the encoder manufacture and installation errors deteriorate the measurement accuracy,a dual detector PDE is debeloped considering the angular periodical “false” components due to encoder errors.Moreover,phasedifferential IAS estimation method and encoder error self-correction method are proposed based on the PDF.It suppresses the periodical “false” IAS components due to encoder errors.A modulation signal model is built to investigate the performance of the proposed PDE and corresponding IAS measurment method,besides,the frequency-amplitude characteristic of PDE dual detector interval angle are analysed.The PDE experiment results validate the PDE IAS measurement correctness and effectiveness.The proposed PDE IAS measurment method has lower Signal-to-Noise Ratio(SNR),less error,and higher IAS measurement accuracy comparing with Resor method and Diamond method.(3)Aiming to the IAS based planetary gear set fault recognition accuracy problem,factors such as planar translation and rotating degrees of freedom,floating sun gear,timevarying mesh stiffness and damping are considered to build a planetary gear(PG)set dynamic model.The influences of time-varying transmission paths,nonlinear energy attenuation and multi-source multi-path superimposed attenuation are investigated based on the PG vibration responses and planetary gear set vibration signal analytical model.A PDE IAS based planetary gear fault diagnosis method is proposed,which recognize the PG faults at different locations and severities.The accuracy of PDE-IAS based fault diagnosis method is compaed with the conventional vibration based method.(4)The relationship between the fault order amplitude and the PG load are studied;based on the researches about IAS measurement error mechanism,the PDE IAS accurate measurement method and the Lab Windows / CVI,a PDE based PG fault diagnosis system is built to achieve accurate measurement of IAS.Besides,it measures temperature,vibration,motor speed,current and load.This new system allows the real-time PG monitoring and fault diagnosis.The experiment results show that the proposed method is effectiveness,which has wider application in sophisticated equipment's IAS measurement and fault diagnosis.