Application of Lock-In Amplifier on gear diagnosis

Detection of faults in gears under variable rotational speed by vibration analysis becomes in a difficult task because events characterizing faults are not periodic. In this work, the use of Lock-In Amplifier (LIA), which leads to a time analysis approach, is proposed to be applied on gear fault detection. In this work, LIA is synchronized to the rotational frequency of any of the gear shafts and is used in order to determine spectral components related to a gear fault. In order to compare effectiveness and efficiency of the proposed technique with previously developed techniques, two gear-failure indicators are presented. These two indicators are determined in such a way that distributed teeth wear and faults producing a vibration with amplitude modulation can be detected. Several study cases, including numerical simulations and real vibration analysis, were carried out in order to validate the effectiveness of the proposed technique.