I. Introduction
Efficient machine fault diagnosis technology can prevent unexpected device faults, decrease device downtime, and increase device operating efficiency. Over the last few decades, fault diagnosis technology is continually updated by using the latest technological advances in two main categories, i.e., fault diagnosis algorithm and fault diagnosis system. A wide variety of algorithms, such as overall level monitoring, frequency spectrum analysis, artificial neural networks (ANNs), and support vector machine (SVM), have been successfully developed and implemented for machine fault diagnosis [1].