A comparative study on Vibration- and current-based approaches for drivetrain gearbox fault diagnosis

Gearboxes are widely used in rotary machines, such as wind turbines, automobiles, and helicopters. Failures of gearboxes contribute to a significant portion of the total failures and downtime in these machines. Gearbox fault diagnosis is an effective means to prevent catastrophic failures, improve the reliability, and reduce the downtime and maintenance cost of these machines. Vibration-based approaches have been employed in most commercially available condition monitoring systems (CMSs); while current-based approaches have received increasing attentions in the industry and academia. This paper presents a comparative study on the vibration- and current-based approaches for gearbox fault diagnosis. Theoretical analysis and experimental tests are carried out to show that: in vibration signals, ghost frequencies appear when the gearbox is healthy and disappear when a gear fault occurs; vibration signals of a faulty gearbox are modulated by shaft rotating frequencies at gear meshing frequencies (GMFs); in current signals, the fundamental frequency component is dominant when the gearbox is healthy; and current signals are modulated by gearbox characteristic frequencies at the fundamental frequency when gear faults appear.