Search results for " vibration"

Real time assessment of hand-arm vibration system based on capacitive MEMS accelerometers

2012

Vibrations are a well known potential cause of health diseases and therefore constitute a main concern for the safety of workers in a large number of activities. In order to prevent health hazards, national and international institutions have issued laws and directives which establish recommended limits to the workers' exposure to vibrations during operations. Consequently, if the amount of adsorbed vibration exceeds the allowable daily limits the worker has to stop his job. Recent wireless sensing and communicating technologies can effectively be employed for such purpose, allowing to develop monitoring customized devices at affordable cost which could be easily employed during the workers…

Diagnosis of mechanical unbalance for double cage induction motor load in time-varying conditions based on motor vibration signature analysis

2013

This paper investigates the detectability of mechanical unbalance in double cage induction motor load using motor vibration signature analysis technique. Rotor imbalances induce specific harmonic components in electrical, electromagnetical, and mechanical quantities. Harmonic components characteristic of this category of rotor faults, issued from vibration signals analysis, are closely related to rotating speed of the rotor, which complicates its detection under non-stationary operating conditions of the motor. Firstly, experimental results were performed first under healthy and mechanical load unbalance cases, for different load levels under steady-state operating conditions to evaluate th…

Closed-loop bandwidth impact on MVSA for rotor broken bar diagnosis in IRFOC double squirrel cage induction motor drives

2013

This paper investigates the detectability of rotor broken bars in indirect rotor flux oriented control (IRFOC) for variable speed double cage induction motor drives, using vibration signature analysis techniques. The Impact of the closed loop control system cannot be neglected when the detection of rotor asymmetries in the machine is based on the signature analysis of electrical or mechanical variables. Therefore, the investigation of rotor fault components for different bandwidths of closed-loop regulators is necessary to evaluate its relevance in the above listed variables. This paper investigates the impact of the control system on relevance of the fault components computed from axial an…

Some properties of multi-degree-of-freedom potential systems and application to statistical equivalent non-linearization

2003

This paper presents some properties of two restricted classes of multi-degree-of-freedom potential systems subjected to Gaussian white-noise excitations. Specifically, potential systems which exhibit damping terms with energy-dependent polynomial form are referred to. In this context, first systems with coupled stiffness terms and damping terms depending on the total energy are investigated. Then, systems with uncoupled stiffness terms and damping terms depending on the total energy in each degree-of-freedom are considered. For these two classes, it is found that algebraic relations among the stationary statistical moments of the energy functions can be derived by applying standard tools of…

HEALTH MONITORING, FAULT DETECTION AND DIAGNOSIS IN INDUSTRIAL ROTATING MACHINERY BY ADVANCED VIBRATION ANALYSIS

Le vibrazioni in campo ferroviario: analisi f.e.m. dell’interazione convoglio-sovrastruttura-terreno

2003

This paper describes the formulation and application of a finite element method model that simulates the generation and propagation of train-induced vibrations into track-ground system. The F.E.M. model accounts for the interaction between ground, railway, shape of cross-section and train speed. The aim of this research is the evaluation of the influence of each factor on vibrational phenomena.

Optimized substrates and measurement approaches for Raman spectroscopy of graphene nanoribbons

2019

The on-surface synthesis of graphene nanoribbons (GNRs) allows for the fabrication of atomically precise narrow GNRs. Despite their exceptional properties which can be tuned by ribbon width and edge structure, significant challenges remain for GNR processing and characterization. In this contribution, we use Raman spectroscopy to characterize different types of GNRs on their growth substrate and to track their quality upon substrate transfer. We present a Raman-optimized (RO) device substrate and an optimized mapping approach that allows for acquisition of high-resolution Raman spectra, achieving enhancement factors as high as 120 with respect to signals measured on standard SiO2/Si substra…

Polariton response in the presence of Brownian dissipation from molecular vibrations

2020

We study the elastic response of a stationarily driven system of a cavity field strongly coupled with molecular excitons, taking into account the main dissipation channels due to the finite cavity linewidth and molecular vibrations. We show that the frequently used coupled oscillator model fails in describing this response especially due to the non-Lorentzian dissipation of the molecules to their vibrations. Signatures of this failure are the temperature dependent minimum point of the polariton peak splitting, uneven polariton peak height at the minimum splitting, and the asymmetric shape of the polariton peaks even at the experimentally accessed "zero-detuning" point. Using a rather generi…

Semiactive–passive structural vibration control strategy for adjacent structures under seismic excitation

2012

Abstract The objective of this paper is to study a structural vibration control strategy for seismic protection of multi-structure systems that combines interstructure passive damping elements with local feedback control systems implemented in the substructures. These local feedback control systems are independently designed and operated, and use semiactive devices with limited actuation capacity as force actuators. The combined action of local semiactive feedback control systems and passive interstructure links can produce an appropriate reduction in the substructures' vibrational response and, simultaneously, provides additional protection against interstructure collisions. The proposed s…

Nonlinear model based particle swarm optimization of PID shimmy damping control

2016

The present study aims to investigate the shimmy stability behavior of a single wheeled nose landing gear system. The system is supposed to be equipped with an electromechanical actuator capable to control the shimmy vibrations. A Proportional-Integrative-Derivative (PID) controller, tuned by using the Particle Swarm Optimization (PSO) procedure, is here proposed to actively damp the shimmy vibration. Time-history results for some test cases are reported and commented. Stochastic analysis is last presented to assess the robustness of the control system.