Envelope Detection and Cepstrum Analysis for Gear Fault Diagnosis – A Comparative Study

While operating a gear with local fault impulse is created, the high-frequency shock vibration is then generated and the vibration amplitude is modulated by the pulse force. Both the envelope and cepstrum analyses are useful tools to identify the fault frequencies and distinguish them from other frequency contents. Since the envelope analysis method provides an important and effective approach to analyse the fault signals of high-frequency impact vibration, it has been applied to the roller bearing fault diagnosis successfully. The intent of this article is to introduce these two tools and compare them between in a pragmatic way and to demonstrate their properties by using practical example of a gear fault. All the experimental data are acquired from vehicle gearbox which is tested on the laboratory stand equipped with three dynamometers; the input dynamometer serves as internal combustion engine, the output dynamometers introduce the load on the flanges of output joint shafts. The pitting defect is manufactured on one tooth of pinion gear on the output shaft. The results obtained from practical experiments prove that Cepstrum analysis provides a clear indication of fault for machine parts such as vehicle gearbox in addition to evaluate the efficiency of the common envelope analysis.