Generalised envelope spectrum-based signal-to-noise objectives: Formulation, optimisation and application for gear fault detection under time-varying speed conditions

TL;DR

This paper introduces a new envelope spectrum-based signal-to-noise objective for vibration signal filtering, improving gear fault detection under variable speed conditions by directly maximizing fault signature prominence.

Contribution

It formulates a generalized envelope spectrum-based objective function that enhances fault detection without relying on proxy health indicators, optimized directly for variable speed scenarios.

Findings

Outperforms five existing methods in experimental tests

Effective in variable speed conditions

Directly maximizes fault signature prominence

Abstract

In vibration-based condition monitoring, optimal filter design improves fault detection by enhancing weak fault signatures within vibration signals. This process involves optimising a derived objective function from a defined objective. The objectives are often based on proxy health indicators to determine the filter's parameters. However, these indicators can be compromised by irrelevant extraneous signal components and fluctuating operational conditions, affecting the filter's efficacy. Fault detection primarily uses the fault component's prominence in the squared envelope spectrum, quantified by a squared envelope spectrum-based signal-to-noise ratio. New optimal filter objective functions are derived from the proposed generalised envelope spectrum-based signal-to-noise objective for machines operating under variable speed conditions. Instead of optimising proxy health indicators, the optimal filter coefficients of the formulation directly maximise the squared envelope spectrum-based signal-to-noise ratio over targeted frequency bands using standard gradient-based optimisers. Four derived objective functions from the proposed objective effectively outperform five prominent methods in tests on three experimental datasets.