A Similarity Comparison Method of Homologous Fault Response Fragments under Variable Rotational Speed

Abstract

Effective fault detection and diagnosis (FDD) for rotating machinery is always a focus issue in improving the prognostic and health management (PHM) of the equipments. The existing usage of similarity measurement has been widely spread in searching the homologous fault responses from vibration signals, but most of them are just suitable for stable speed and cannot be applied in all variable speed conditions. In order to improve measurement performance, a fast-meshed phase portrait (FMPP) frame combining the phase-space technique and box-scoring calculation is proposed. Firstly, the variable-speed signal is divided into multiple undetermined fragments according to fault characteristic orders (FCOs). Secondly, the undetermined fragments are reconstructed into corresponding phase-space trajectories to overcome the time-delay matching inconsistency of the variable speed fragments. Thirdly, the phase-space trajectories are mapped into meshed phase portraits via box-scoring calculation. Such decisive calculation can effectively transforms the diverse unequal fragments into the phase diagrams with same size, which saves time for the subsequent similarity measurement. Finally, the proposed FMPP is tested both for accuracy and timeliness on a self-built bearing bench, where the order tracking (OT) and dynamic time warping (DTW) methods are used for the comparisons. The experiments proved the effectiveness of the proposed method.

Mechanical varying non-stationary signal separation method based on instantaneous frequency estimation

“…2 With the development of non-stationary signal processing technology, scholars have gradually carried out research on the mechanical fault vibration signal separation. 3,4 In general, they can be divided into four universal categories, order tracking, 5 order cyclostationary analysis 6 and timefrequency analysis, 7 tine-varying filter. 8 As for order tracking, 9 its main procedure is to transform non-stationary signal into stationary or cyclically stationary signal by equal interval sampling technology in angle domain, so as to establish a bridge between signal processing under variable speed condition and constant speed condition, so that the classical signal processing method can play its role again.…”

“…2 With the development of non-stationary signal processing technology, scholars have gradually carried out research on the mechanical fault vibration signal separation. 3,4 In general, they can be divided into four universal categories, order tracking, 5 order cyclostationary analysis 6 and time-frequency analysis, 7 tine-varying filter. 8…”