Search results for "Earing"

Sub-Optimal Control Law for Active Magnetic Bearings Suspension

2012

This paper deals with the comparison of three types of sub-optimal control law for the stable levitation of a turbojet shaft, sustained by two radial active magnetic bearings (AMBs). Shaft is considered rigid for the procedure simplification. The utilized approach leads to development of different sub-optimal control laws to use in speed-varying simulations in the angular speed of the shaft. The first control matrix is obtained by explicit relationships of the parameters of the control law vs. speed, obtained using a curve-fitting procedure neglecting the speed-varying elements out of the main diagonal of each single block constituting the entire control matrix. The second control law is ob…

ROBUST CONTROL FOR A SUSPENDED ROTATING SHAFT BY RADIAL ACTIVE MAGNETIC BEARINGS

2011

This paper shows a comparison based on dynamic behaviour of a rotating shaft when it is suspended by 4-axis active magnetic bearings under several control systems. The control systems used are μ-synthesis, loop shaping design procedure and Sub(H∞) robust control with the introduction of uncertainties on position and current gains of the actuators. Each of these controllers is characterized by four input signals and four output signals and the introduction of uncertainties on displacement gain and current gain is due to torn and worn of the components during the time, which can lead the entire system to instability phenomena. The comparison of the performances is obtained through the introdu…

MULTIBODY NUMERICAL SIMULATION OF AN INTERNAL COMBUSTION ENGINE WITH APPRAISAL OF THE WEAR DAMAGE

2009

An internal combustion engine at four times (Otto cycle) and three cylinders is simulated by multibody software MSC Visual Nastran. The bearings are simulated by means of the library of constraint of the software, putting a particular attention to bench bearings and to the lubrication conditions. The loads on the bench bearings and in both the feet and head of the connecting rods, are evaluated by dynamical simulation, so that the inertia loads can be take in account, considering the condition of the maximum couple furnished by the engine. By making the necessary hypothesis, the evaluation of the wear damage is executed by Bayer theory on zero wear, obtaining that a good expectation of life…

DYNAMIC BEHAVIOUR COMPARISON OF ROTATING SHAFT SUSPENDED BY TWO RADIAL ACTIVE MAGNETIC BEARINGS.

2012

EXPERIMENTAL INVESTIGATIONS OF MINIMUM POWER CONSUMPTION OPTIMAL CONTROL FOR VARIABLE SPEED AMB ROTOR

2010

The purpose of this paper is to present a method for development of the optimal speed-dependent control matrix for a rotor supported on active magnetic bearings (AMBs) with the provision of minimum control power consumption over the operating speed range. The speed dependency of the optimal control matrix is the result of the dynamics of rotating machines. Most of published works on optimal control use a stationary optimal control matrix derived for the non-rotating system and thus neglecting the effect of gyroscopic phenomena. This paper employs the minimum energy consumption condition to derive the speed varying optimal control for rotating AMB rotor system. In the presented approach the …

Failure mechanisms of flax/epoxy laminates with open hole: a failure map

2017

Aim of this paper is the investigation of the pin/hole contact stress and failure mechanisms of flax/epoxy composite laminates underwent to tensile bearing tests. In particular, the maximum loads and failure modes are evaluated at varying joint geometry. In order to optimize the use of composite materials in structural applications, an experimental failure map, identifying main failure modes of mechanically fastened joints, is obtained by evaluating failure modes (i.e., net tension, shear out, cleavage and bearing) as a function of the pin diameter and the position of the hole from the free edge of the laminate. Main goal of this paper is give a simple experimental methodology to support th…

The relationship between moderate hearing loss with balance and postural control

2017

AGE-RELATED HEARING IMPAIRMENT (ARHI): A COMMON SENSORY DEFICIT IN THE ELDERLY

2011

This paper aims to give a broad overview of the scientific findings related to Age-related hearing impairment that is a complex disorder, with both environmental as well as genetic factors contributing to the impairment. The involvement of several environmental factors has been partially elucidated. A first step towards the identification of the genetic factors has been made, which will result in the identification of susceptibility genes, and will provide possible targets for the future treatment and/or prevention of ARHI.

Intratympanic treatment with dexamethasone as first-line or salvage therapy in sudden sensorineural hearing loss: Results of a retrospective study

2014

Aim: Sudden sensorineural hearing loss is a condition of emergency in Otolaryngology. Although there is no universally accepted treatment protocol, corticosteroids, intravenous and oral, are the most common treatment The purpose of this study is to evaluate the efficacy of intratympanic administration of dexamethasone as first line therapy, or as a rescue therapy after treatment with systemic steroids in patients not responders. Methods: The population, consisting of 85 patients referred to our unit from January 2010 to December 2013, was divided into two groups according to the treatment protocol performed. We also analyzed possible variables that may affect the response to treatment such …

Association between sensorineural hearing loss and sleep-disordered breathing: Literature review

2015

The cochlea is especially sensitive to circulatory alterations because it is supplied by a single terminal artery and lacks adequate collateral blood supply. To examine the putative association between Sensorineural Hearing Loss (SNHL) and Sleep Disordered Breathing (SDB) through the literature review is very interesting. In fact these medical disorders usually are associated to cerebral circulatory alterations resulting in hypoxia, acute hemodynamic change, and decreased cerebral blood flow, because the Sleep Disorder Breathing (SDB), for example OSAHS (Obstructive Sleep Apnea Hypopnea Syndrome), is characterized by periodic hyposia/reoxygenation. These noxious stimuli can, in turn, activa…