Paper Title
Fault Diagnosis of Wind Turbine Gearboxes using Enhanced Tacholess Order Tracking

Abstract
Health monitoring of wind turbines is crucial to support their sustainability and economic operation. Gearbox failures contribute significantly to the cost of wind turbine maintenance. These failures are typically monitored by vibration sensors attached to external housing. Non-stationary vibration is induced by the variable-speed operation of the wind turbine. In this paper, a new technique is introduced to enable the extraction of a speed reference from the vibration signal, which can be utilized to remove speed fluctuations and diagnose faults in the gearbox. High speed variations of the shaft, i.e., tacho signal, have been extracted from the vibration signal of an accelerometer mounted on the casing of the gearbox. The epicyclic mesh frequency has been used to construct the speed reference by an enhanced order tracking technique comprising auto-adjustable phase demodulation (APD). APDis aimed at improving fault detection efficiency by accommodating highspeed fluctuations. The effectiveness of the proposed APD performance has been successfully demonstrated by using vibration measurements from commercial in-service wind turbines. Index Terms - Computed order tracking, Phase demodulation, Planetary gearbox, Non-stationary vibration