Gearbox fault diagnosis under different operating conditions based on time synchronous average and ensemble empirical mode decomposition

In this paper, a new method is proposed by combining ensemble empirical mode decomposition (EEMD) with order tracking techniques to analyse the vibration signals from a two stage helical gearbox. The method improves EEMD results in that it overcomes the potential deficiencies and achieves better order spectrum representation for fault diagnosis. Based on the analysis, a diagnostic feature is designed based on the order spectra of extracted IFMs for detection and separation of gearbox faults. Experimental results show this feature is sensitive to different fault severities and robust to the influences from operating conditions and remote sensor locations

Motor current signal analysis using a modified bispectrum for machine fault diagnosis

This paper presents the use of the induction motor current to identify and quantify common faults within a two-stage reciprocating compressor. The theoretical basis is studied to understand current signal characteristics when the motor undertakes a varying load under faulty conditions. Although conventional bispectrum representation of current signal allows the inclusion of phase information and the elimination of Gaussian noise, it produces unstable results due to random phase variation of the sideband components in the current signal. A modified bispectrum based on the amplitude modulation feature of the current signal is thus proposed to combine both lower sidebands and higher sidebands simultaneously and hence describe the current signal more accurately. Based on this new bispectrum a more effective diagnostic feature namely normalised bispectral peak is developed for fault classification. In association with the kurtosis of the raw current signal, the bispectrum feature gives rise to reliable fault classification results. In particular, the low feature values can differentiate the belt looseness from other fault cases and discharge valve leakage and intercooler leakage can be separated easily using two linear classifiers. This work provides a novel approach to the analysis of stator current for the diagnosis of motor drive faults from downstream driving equipment

Acoustic based safety emergency vehicle detection for intelligent transport systems

A system has been investigated for the detection of incoming direction of an emergency vehicle. Acoustic detection methods based on a cross microphone array have been implemented. It is shown that source detection based on time delay estimation outperforms sound intensity techniques, although both techniques perform well for the application. The relaying of information to the driver as a warning signal has been investigated through the use of ambisonic technology and a 4 speaker array which is ubiquitous in most modern vehicles. Simulations show that accurate warning information may be relayed to the driver and afford correct action

Um aparato experimental para estudo e desenvolvimento de circuitos de acondicionamento de sinal: uma experiência pedagógica

Este documento descreve um aparato experimental desenvolvido pelos autores e relata alguns aspectos da respectiva experiência pedagógica que tem constituído a sua utilização na componente laboratorial de uma disciplina da área da electrónica aplicada. O aparato contém sensores e actuadores incorporados em dois tanques de água e é direcionado para o estudo e teste dos respectivos circuitos de acondicionamento de sinal. A modelação das funções características dos sensores e o desenvolvimento de simples algoritmos de controlo é também exercitado na utilização deste sistema. No contexto académico em que tem sido utilizado, pode encarar-se este sistema como uma reprodução em pequena escala de um hipotético processo industrial, o que tipicamente contribui para uma maior motivação por parte dos alunos e facilita a concepção de enunciados de trabalhos que promovam uma atitude direccionada ao processo como um todo e menos numa soma de tarefas individuais não relacionadas.info:eu-repo/semantics/publishedVersio