Complex Demodulation for Bearing Fault Detection PDF Download

Author: I. M. Howard
Publisher:
ISBN: 9780731696888
Category : Airplanes
Languages : en
Pages : 16

View

Book Description
Vibration analysis using the high frequency resonance technique has been used successfully to detect incipient failure in rolling element bearings. This memo outlines a new method of obtaining the demodulated narrow band envelope of a bearing vibration signal from the high frequency resonant response. Previous techniques have used an analogue envelope where the raw analogue signal is bandpass filtered and enveloped before digitising. The method outlined in this document first digitises the vibration signal, performs a complex demodulation operation, then computes the envelope followed by its spectrum. Fault repetition frequencies can be identified in the demodulated spectrum of the high frequency resonant response. Keywords: Vibration tests; Demodulation; Bearing stress; Resonant frequency; Australia. (jhd).

Author: Juanjuan SHI
Publisher:
ISBN:
Category : University of Ottawa theses
Languages : en
Pages :

View

Book Description
As the failure of a bearing could cause cascading breakdowns of the mechanical system and then lead to costly repairs and production delays, bearing condition monitoring has received much attention for decades. One of the primary methods for this purpose is based on the analysis of vibration signal measured by accelerometers because such data are information-rich. The vibration signal collected from a defective bearing is, however, a mixture of several signal components including the fault-generated impulses, interferences from other machine components, and background noise, where fault-induced impulses are further modulated by various low frequency signal contents. The compounded effects of interferences, background noise and the combined modulation effects make it difficult to detect bearing faults. This is further complicated by the nonstationary nature of vibration signals due to speed variations in some cases, such as the bearings in a wind turbine. As such, the main challenges in the vibration-based bearing monitoring are how to address the modulation, noise, interference, and nonstationarity matters. Over the past few decades, considerable research activities have been carried out to deal with the first three issues. Recently, the nonstationarity matter has also attracted strong interests from both industry and academic community. Nevertheless, the existing techniques still have problems (deficiencies) as listed below: (1) The existing enveloping methods for bearing fault feature extraction are often adversely affected by multiple interferences. To eliminate the effect of interferences, the prefiltering is required, which is often parameter-dependent and knowledge-demanding. The selection of proper filter parameters is challenging and even more so in a time-varying environment. (2) Even though filters are properly designed, they are of little use in handling in-band noise and interferences which are also barriers for bearing fault detection, particularly for incipient bearing faults with weak signatures. (3) Conventional approaches for bearing fault detection under constant speed are no longer applicable to the variable speed case because such speed fluctuations may cause zsmearingy of the discrete frequencies in the frequency representation. Most current methods for rotating machinery condition monitoring under time-varying speed require signal resampling based on the shaft rotating frequency. For the bearing case, the shaft rotating frequency is, however, often unavailable as it is coupled with the instantaneous fault characteristic frequency (IFCF) by a fault characteristic coefficient (FCC) which cannot be determined without knowing the fault type. Additionally, the effectiveness of resampling-based methods is largely dependent on the accuracy of resampling procedure which, even if reliable, can complicate the entire fault detection process substantially. (4) Time-frequency analysis (TFA) has proved to be a powerful tool in analyzing nonstationary signal and moreover does not require resampling for bearing fault identification. However, the diffusion of time-frequency representation (TFR) along time and frequency axes caused by lack of energy concentration would handicap the application of the TFA. In fact, the reported TFA applications in bearing fault diagnosis are still very limited. To address the first two aforementioned problems, i.e., (1) and (2), for constant speed cases, two morphology-based methods are proposed to extract bearing fault feature without prefiltering. Another two methods are developed to specifically handle the remaining problems for the bearing fault detection under time-varying speed conditions. These methods are itemized as follows: (1) An efficient enveloping method based on signal Fractal Dimension (FD) for bearing fault feature extraction without prefiltering, (2) A signal decomposition technique based on oscillatory behaviors for noise reduction and interferences removal (including in-band ones), (3) A prefiltering-free and resampling-free approach for bearing fault diagnosis under variable speed condition via the joint application of FD-based envelope demodulation and generalized demodulation (GD), and (4) A combined dual-demodulation transform (DDT) and synchrosqueezing approach for TFR energy concentration level enhancement and bearing fault identification. With respect to constant speed cases, the FD-based enveloping method, where a short time Fractal dimension (STFD) transform is proposed, can suppress interferences and highlight the fault-induced impulsive signature by transforming the vibration signal into a STFD representation. Its effectiveness, however, deteriorates with the increased complexity of the interference frequencies, particularly for multiple interferences with high frequencies. As such, the second method, which isolates fault-induced transients from interferences and noise via oscillatory behavior analysis, is then developed to complement the FD-based enveloping approach. Both methods are independent of frequency information and free from prefiltering, hence eliminating the tedious process for filter parameter specification. The in-band vibration interferences can also be suppressed mainly by the second approach. For the nonstationary cases, a prefiltering-free and resampling-free strategy is developed via the joint application of STFD and GD, from which a resampling-free order spectrum can be derived. This order spectrum can effectively reveal not only the existence of a fault but also its location. However, the success of this method relies largely on an effective enveloping technique. To address this matter and at the same time to exploit the advantages of TFA in nonstationary signal analysis, a TFA technique, involving dual demodulations and an iterative process, is developed and innovatively applied to bearing fault identification. The proposed methods have been validated using both simulation and experimental data collected in our lab. The test results have shown that the first two methods can effectively extract fault signatures, remove the interferences (including in-band ones) without prefiltering, and detect fault types from vibration signals for constant speed cases. The last two have shown to be effective in detecting faults and discern fault types from vibration data collected under variable speed conditions without resampling and prefiltering.

Author: Robert Bond Randall
Publisher: John Wiley & Sons
ISBN: 0470977582
Category : Technology & Engineering
Languages : en
Pages : 409

View

Book Description
"Without doubt the best modern and up-to-date text on the topic, wirtten by one of the world leading experts in the field. Should be on the desk of any practitioner or researcher involved in the field of Machine Condition Monitoring" Simon Braun, Israel Institute of Technology Explaining complex ideas in an easy to understand way, Vibration-based Condition Monitoring provides a comprehensive survey of the application of vibration analysis to the condition monitoring of machines. Reflecting the natural progression of these systems by presenting the fundamental material and then moving onto detection, diagnosis and prognosis, Randall presents classic and state-of-the-art research results that cover vibration signals from rotating and reciprocating machines; basic signal processing techniques; fault detection; diagnostic techniques, and prognostics. Developed out of notes for a course in machine condition monitoring given by Robert Bond Randall over ten years at the University of New South Wales, Vibration-based Condition Monitoring: Industrial, Aerospace and Automotive Applications is essential reading for graduate and postgraduate students/ researchers in machine condition monitoring and diagnostics as well as condition monitoring practitioners and machine manufacturers who want to include a machine monitoring service with their product. Includes a number of exercises for each chapter, many based on Matlab, to illustrate basic points as well as to facilitate the use of the book as a textbook for courses in the topic. Accompanied by a website www.wiley.com/go/randall housing exercises along with data sets and implementation code in Matlab for some of the methods as well as other pedagogical aids. Authored by an internationally recognised authority in the area of condition monitoring.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704

View

Book Description

Author: Shazali Osman
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Nowadays, modern rotating machinery industries such as automotive, aerospace, turbo machinery, chemical plants, and power generation stations are rapidly increasing in complexity and in their everyday operations, which demand their systems to operate at higher reliability, extreme safety, and with lower production and maintenance costs. Therefore, accurate fault diagnosis of machine failure is vital to the operation of the related industries. The majority of machine imperfections has been related to gearbox faults (e.g., gears, shafts and bearings), which are subject to damage modes such as fatigue, impacts, and overloading. Faults not detected in time can result in severe damage to machinery, catastrophic injuries, and substantial financial losses. On the other hand, if a fault is detected in its early stages, corrective and preventive action can be taken to avoid any significant machine failure. Vibration monitoring, a method that is widely used to determine the condition of various mechanical systems, will be applied in this work. In data acquisition, a transducer is attached to the structure under investigation and the vibration signal is recorded. This signal is then processed to extract representative features for fault detection. Signal processing techniques are therefore required to extract representative features to assess the health condition of gearbox components. However, in practice, the theoretical frequencies and characteristic features of gearbox faults may be modulated and masked by parasitical frequencies due to numerous noisy vibrations, as well as by the complexity of the transmission mechanics. To solve the related problems, the objective of this research work is to propose new signal processing technologies to evaluate gearbox health conditions. This work will focus on fixed-axis gearboxes, in which all gears are designed to rotate around their perspective fixed centers. Firstly, an enhanced morphological filtering (eM) technique is proposed to improve signal-to-noise ratio. Secondly, under controlled operating conditions, an integrated Hilbert Huang transform (iHT) method is suggested for bearing fault detection. Thirdly, a leakage-free resonance sparse decomposition (LRSD)-based technique is developed for advanced vibration signal analysis to eliminate random noise and to recognize characteristic features for bearing in gearboxes health conditions. The effectiveness of the proposed techniques is verified by a series of experimental tests corresponding to different bearing and gearbox conditions.

Author: Abdenour Soualhi
Publisher: John Wiley & Sons
ISBN: 1786304651
Category : Science
Languages : en
Pages : 240

View

Book Description
Methods of diagnosis and prognosis play a key role in the reliability and safety of industrial systems. Failure diagnosis requires the use of suitable sensors, which provide signals that are processed to monitor features (health indicators) for defects. These features are required to distinguish between operating states, in order to inform the operator of the severity level, or even the type, of a failure. Prognosis is defined as the estimation of a systems lifespan, including how long remains and how long has passed. It also encompasses the prediction of impending failures. This is a challenge that many researchers are currently trying to address. Electrical Systems, a book in two volumes, informs readers of the theoretical solutions to this problem, and the results obtained in several laboratories in France, Spain and further afield. To this end, many researchers from the scientific community have contributed to this book to share their research results.

Author: Hamid Reza Karimi
Publisher: Academic Press
ISBN: 0128224886
Category : Technology & Engineering
Languages : en
Pages : 421

View

Book Description
Fault Diagnosis and Prognosis Techniques for Complex Engineering Systems gives a systematic description of the many facets of envisaging, designing, implementing, and experimentally exploring emerging trends in fault diagnosis and failure prognosis in mechanical, electrical, hydraulic and biomedical systems. The book is devoted to the development of mathematical methodologies for fault diagnosis and isolation, fault tolerant control, and failure prognosis problems of engineering systems. Sections present new techniques in reliability modeling, reliability analysis, reliability design, fault and failure detection, signal processing, and fault tolerant control of engineering systems. Sections focus on the development of mathematical methodologies for diagnosis and prognosis of faults or failures, providing a unified platform for understanding and applicability of advanced diagnosis and prognosis methodologies for improving reliability purposes in both theory and practice, such as vehicles, manufacturing systems, circuits, flights, biomedical systems. This book will be a valuable resource for different groups of readers – mechanical engineers working on vehicle systems, electrical engineers working on rotary machinery systems, control engineers working on fault detection systems, mathematicians and physician working on complex dynamics, and many more. Presents recent advances of theory, technological aspects, and applications of advanced diagnosis and prognosis methodologies in engineering applications Provides a series of the latest results, including fault detection, isolation, fault tolerant control, failure prognosis of components, and more Gives numerical and simulation results in each chapter to reflect engineering practices

Author: Ran Chen
Publisher: Trans Tech Publications Ltd
ISBN: 3038138118
Category : Technology & Engineering
Languages : en
Pages : 4300

View

Book Description
Volume is indexed by Thomson Reuters CPCI-S (WoS). This work comprises 798 peer-reviewed papers on Mechatronics and Intelligent Materials, and seeks to promote the development of those topics by strengthening international academic cooperation and communication via the exchange of research ideas. It will provide readers with a broad overview of the latest advances made in the fields of mechatronics and intelligent materials.

Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 980

View

Book Description

Author: Pranav H. Darji
Publisher: BoD – Books on Demand
ISBN: 9535131834
Category : Technology & Engineering
Languages : en
Pages : 122

View

Book Description
In the twenty-first century, bearings are expected to perform better in the form of various operating conditions, that is from low speed to extremely high speed and from low load to huge load applications. The expectations from the field of bearing technology are great. During the recent years, we have been witnessing the development of a new generation of mechanical systems that are highly miniaturized and very sophisticated, yet extremely robust. Technological progress creates increasingly arduous conditions for rolling mechanisms.