Transduction matrix of AC motor driven mechanical systems : system modelling and fault diagnosis

ABSTRACT In this dissertation, a modelling technique for motor driven system based on transduction matrix is introduced. Transduction matrix describes the relationship between input and output of a system in frequency domain, thus it provides better understanding of the system’s condition. For a motor driven system running at constant frequency, the transduction matrices for induction motor, power transmission system and mechanical loading can be obtained from respective governing equations. Since transduction matrix represents the system’s properties, condition monitoring can be attained by studying these transduction functions. In addition, transduction matrix facilitates the analysis on both impedance propagation and power flow in the motor driven system. Consequently, the electrical input impedance that consists of transduction function is utilized in condition monitoring of induction motor. Studying the frequency components of electrical input impedance allows characteristic frequencies of motor faults to be identified. Therefore, the proposed monitoring signature is used to monitor the change of signature due to broken rotor bar, abnormal air-gap eccentricity and bearing faults. By comparing with the results from conventional monitoring technique, impedance signature proved to have better sensitivity as fault signature is amplified. Furthermore, wavelet packet transform is utilized in order to carry out fault detection in time-frequency analysis, where the signal to noise ratio is improved and make the fault detection easier. School of Mechanical and Aerospace Engineering Nanyang Technological University Acknowledgement ACKNOWLEDGEMENT The author would like to express profound gratitude to his supervisor, Professor Ling Shih-Fu for his invaluable support, encouragement, useful suggestions and supervision he has given to the author throughout the research work. His moral support and continuous guidance enabled the author to complete work successfully. It has been a great honour and pleasure to work with him. The author would also like to extend his appreciation to Assoc Prof Choo Fook Hoong for his precious suggestions in modelling of induction motor. The author also highly appreciates the kindness of Mr James Ee, for his valuable information of experimental setup and motor faults throughout the research. In addition, the author also likes to extend his thanks to Mr Wong Yoke Rong, for his assistances on the programming of signal processing programme. His patience and enthusiasm to help are gratefully acknowledged. The author also likes to extend his appreciation to Mr Ivan Tanra, Ms Felicia Rezanda, Mr Pang Xin and Mr Ju Feng for many fruitful discussions and suggestions. Their suggestion and patience are praiseworthy. The author would like to thank Mr Poon Weng Wai of Mechanic of Machines lab, Mr Cheo Hock Leong and Mrs Halimatun Bte Ma’Arof of Centre of Mechanics of Micro-Systems lab for their technical assistance. Lastly, the author would like to express his appreciation to his family and friends for their understanding and support in his research journey. School of Mechanical and Aerospace Engineering Nanyang Technological University Table of