Dynamics-guided Vibration Signal Analysis for Fixed-axis Gearbox Fault Diagnosis
Creators: Yang, Xingkai
Publisher: name: University of Alberta Library
Year: 2022

<p>Gearboxes are key components commonly employed to transfer torque and power and adjust speed in mechatronic systems, such as wind turbines, automobiles, and mining machines. Due to the harsh working environment, various faults may occur in gearboxes. Tooth cracks account for a<br>
large proportion of gearbox faults. Detection and severity assessment of early tooth cracks is of vital significance to prevent gearbox failures since it enables efficient condition-based maintenance activities, which not only improves system reliability but also reduces operation and maintenance costs. Vibration analysis has been widely utilized for gear tooth crack detection and severity assessment. In industrial applications, gearboxes may work under either constant or time-varying operating conditions. Besides, gearboxes may suffer from either one single tooth crack or multiple tooth cracks depending on their working environment. All these factors render it challenging to get a good understanding of vibration characteristics of gearboxes with tooth cracks owing to their complexity, which undermines the effectiveness of vibration analysis for tooth crack detection and severity assessment.<br>
This thesis aims to procure some insights into vibration characteristics of fixed-axis spur gearboxes with tooth cracks through dynamic simulation, and the obtained insights are further adopted to guide the development of effective vibration signal analysis methods for tooth crack detection and<br>
severity assessment. To this end, the overarching objective of this thesis consists of four sub-objectives, which aim to address four issues related to tooth crack detection and severity assessment for fixed-axis spur gearboxes. Firstly, inspired by the observation that the Crack Induced Impulses (CII) contain more information on tooth crack growth, two novel condition indicators are developed by a proposed method which conducts a thorough analysis on the CII and are adopted for early tooth crack severity assessment. Secondly, to effectively track tooth crack severity progression under time-varying operating conditions, a comprehensive study on how time-varying operating conditions affect vibration signals of a fixed-axis spur gearbox with a tooth crack is conducted. A linear dependence of the Amplitude Modulation (AM) of the CII on the time-varying operating conditions is identified, through which a new condition indicator is proposed to track tooth crack severity progression under time-varying operating conditions. In addition, inspired by the finding that the AM of the CII is resulted from operating condition variations, a normalization method is proposed to remove the speed variation-induced AM of the CII and a normalized CII is obtained. The normalized CII preserve information on tooth crack growth and are free from gearbox speed fluctuations, which are used to track tooth crack severity progression under variable speed conditions. Lastly, insights into vibration characteristics of a fixed-axis spur gearbox with multiple tooth cracks are obtained using dynamic simulation and are<br>
further experimentally validated. Besides, inspired by the observation that the CII can well reflect tooth cracks, a method focusing on the CII is proposed to detect the number and locations of multiple tooth cracks in fixed-axis spur gearboxes.<br>
The research work conducted in this thesis enables us to procure a good understanding of vibration characteristics of fixed-axis spur gearboxes with tooth cracks working under both constant and time-varying operating conditions and provides effective vibration signal analysis methods for<br>
tooth crack detection and severity assessment of fixed-axis spur gearboxes. Future work will explore the effects of tooth lubrication and bearing faults on gearbox vibration characteristics.</p>