INFLUENZA SUL COMPORTAMENTO DINAMICO DI UN ROTORE SOSPESO ATTRAVERSO CUSCINETTI MAGNETICI ATTIVI MEDIANTE \u3bc-SYNTHESIS E LOOP-SHAPING DESIGN

In questo lavoro viene effettuato un confronto sul comportamento dinamico di un albero rotante quando \ue8 sospeso attraverso un sistema di due cuscinetti magnetici ciascuno costituito da due assi. Le sospensione magnetica attiva \ue8 ottenuta elaborando due diversi sistemi di controllo che realizzano la stabilit\ue0 del rotore conferendo a quest\u2019ultimo delle prestazioni robuste nel mantenimento degli spostamenti entro certi margini prestabiliti. Ognuno di questi sistemi di controllo \ue8 caratterizzato da otto ingressi e quattro uscite con la presenza di incertezze sul guadagno spostamento e guadagno di corrente; ci\uf2 \ue8 giustificato dal semplice fatto che gli apparati elettronici possono usurarsi con il continuo uso nel tempo inducendo il rotore a stati di instabilit\ue0 durante un normale funzionamento. I risultati prodotti sono mostrati attraverso le simulazioni in ambiente MATLab dove vengono testate le capacit\ue0 del rotore di eliminare il disturbo e di seguire un riferiment

INFLUENCE OF UNCERTAINTIES ON ROTATING FLEXIBLE SHAFT SUSPENDED BY 4-AXIS RADIAL ACTIVE MAGNETIC BEARINGS \ub5-SYNTHESIS AND LOOP-SHAPING-DESIGN

This paper shows a comparison about dynamic behavior of a rotating shaft when it is suspended by 4-axis radial active magnetic bearing system. The active magnetic suspension is obtained by two different controllers which realize the robust stability and robust performance. The control systems used are \ub5-synthesis and loop shaping design procedure. Each of these controllers is characterized by fourinput and four output signals and the introduction of uncertainties on displacement gain and current gain is justified by the simple fact that during the time the component which constitutes these gains can be subjected to torn and worn which can lead the entire system to instability phenomena. The inputs are the feedbacks of four displacement components relative to the four axis of radial active magnetic bearing while the outputs are the control current injected in the plant in order to provide the control of position of two section under the monitoring of ideal sensors. An ideal sensor here is meant to be able to capture small displacements and without presence of noise. The advantages of a four input controller is the absence of velocity components which are present in the state vector such that no observer and speedsensors are need to build a feedback. The comparison of the performances is made through the introduction of same weighting function for the two control system. The weighting functions are introduced in order to define the required performances for the position and control signals. The results are produced by simulations tracking of reference and disturbance rejection are tested in order to provide elements useful to implement the goal of this paper. All simulations and results are performed by MATLab

Valutazione delle lesioni nell\u2019impatto ciclista adolescente -veicolo con simulazione multibody

Le situazioni di impatto e la dinamica di ciclista e pedone sono le informazioni fondamentali per lo sviluppo di soluzioni efficaci per migliorare la protezione del pedone e del ciclista in caso di urto con autovetture. La casistica degli incidenti a Palermo, negli ultimi anni, avvenuti su strade urbane (84%) che coinvolgono adolescenti (6,4%), mostra che i ciclisti hanno in genere una posizione di impatto superiore rispetto al pedone, con una quota maggiore di lesioni per urti nella zona del parabrezza. In questo lavoro \ue8 eseguita la simulazione dinamica per lo studio delle lesioni alla testa e al torace dell\u2019adolescente, tra una bicicletta generica e un modello di auto che presenta caratteristiche vantaggiose per la sicurezza del pedone o del ciclista. Il software SimWise (Visual Nastran) \ue8 stato usato per la simulazione multibody dell\u2019impatto; il modello antropomorfo, l'auto e le biciclette sono quelli utilizzati in lavori precedenti. L'attenzione \ue8 su un ciclista adolescente, perch\ue9 i relativi dati di lesione si trovano in letteratura con difficolt\ue0. I dodici test d\u2019impatto completo (auto contro ciclista) hanno come parametri principali: velocit\ue0 del veicolo (20, 30, 40 e 50 km/h), con tre diverse posizioni del ciclista rispetto al veicolo: frontale, laterale e posteriore. La posizione di impatto della testa (sopra il cofano, nel parabrezza), determinato dalla prova di crash, mostra che la protezione del ciclista dovrebbe essere migliorata nella zona pi\uf9 alta del parabrezza, rispetto a quelle pedonali. La ferita alla testa viene analizzata utilizzando il parametro HIC e la ferita al torace \ue8 analizzata secondo il criterio dei 3 ms; viene calcolata la probabilit\ue0 AIS 4 +, concludendo che la lesione alla testa \ue8 pi\uf9 pericolosa in caso di pedone adolescente, mentre la ferita della cassa toracica \ue8 pi\uf9 pericolosa nel caso di ciclista adolescente. Inoltre il ciclista adolescente ha una maggiore possibilit\ue0 di sopravvivenza rispetto al ciclista adulto. Incidentologia e simulazioni mostrano che il parabrezza \ue8 una posizione di impatto frequente per testa e torace

Biomechanics parameters in teenage cyclist – SUV accident and comparison with the pedestrian

The study of the injury caused by the vehicle-teenage cyclist crash is presented in this paper. The vehicle is a SUV, with high frontal part, in order to compare the results with those obtained previously in the sedan- teenage cyclist crash and begin a study of the influence of the frontal shape of the vehicle. No variation is executed on the model of the teenage cyclist and the bike. Three different positions are analyzed: front, rear and lateral position. The injury on the cyclist head is examined by HIC criterion, in the way indicated in the rules. Correlation HIC – AIS is used to calculate the lethality of the injuries. The principal conclusion is done that the injury of the head is more dangerous for the SUV impact than the sedan, but only at the maximum speed (50 km/h). The injury to the chest is analyzed by 3 ms criterion; the injury is greater for the SUV impact than the sedan, but the entity is strongly dependent on the cyclist position. A comparison is executed with both the teenage and adult pedestrian concluding that the pedestrian is subjected to greater injury, because the bike absorbs a part of the energy in the front and side crash. The more dangerous injury is the telescoping. A further comparison show that the shape of the bonnet and the height of the frontal part have to be studied in an accurate way to reduce the injury to pedestrians and cyclists

Characterisation of Fibre Glass Panels for Naval Use

This work examines the characteristic of fiber glass composite panels constructed by Cantieri Arturo Stabile in Trapani (Italy): composite materials are very used in the naval applications, where high stiffness and resistance are required with reduced weight. Experimental tests are executed following ASTM or UNI EN rules, in particular the shear test is executed using a rig constructed to the purpose, designed following the rule ASTM D 4255-83. Besides the tests were simulated by analytical methods, by means of Cadec software and numerically by FEM software as Altair Hyperworks and Ansys, to evidence the error range of the experimental test and to obtain the configuration that can give suitable results also for more complex designs. The successive phase of optimization is useful to obtain a reduction of the thickness, without compromising the resistance, for a consequent reduction of the production cost and energy saving of the boat during its use

Design and use of a Fatigue Test Machine in Plane Bending for Composite Specimens and Bonded Joints

Polymeric and composites materials are increasingly used in industry as structural parts, so that specific information on their mechanical properties "at long term" (creep, relaxation, fatigue) are requested. The design and implementation of these components also requires that they are permanently connected together to perform certain functions. The use of adhesives in structural joints has increased over recent years thanks to the continuous development by companies which provide the market with adhesive having better and better mechanical properties. The main areas relate to the aerospace, aeronautical and automotive industries, where requirements are required for lightness and reliability. One of the main causes of out of order of the glue joints is due to the propagation of defects within the adhesive layer. Indeed, a microscopic defect could evolve because of fatigue loading and then propagate to the final break of the component. The defect may occur during the manufacturing process of the component, during the installation or for the incompatibility of the elements to connect. Delamination depends mainly on the extent of crack and on the mode of loading. Proper design and verification of structural elements cannot therefore leave apart from these aspects, so that in recent decades, in parallel with traditional methods, criteria based on fracture mechanics have been developed for the understanding of issues relating to the damage phenomena. Fatigue tests usually require several hours of application of cyclic stress to obtain an appreciable damage. These tests lead to results more or less uneven as to require the repetition of the test several times to obtain more accurate estimation of the endurance limit. All these considerations are economically incompatible with the use of particularly costly servo-hydraulic machines. Thus the development of a specific approach to fatigue tests based on the use of specific materials testing machines (FTM - Fatigue Testing Machine) becomes very important. Some ideal characteristics of such machines is described in the following: 1) adaptability to different geometries and rigidities of the specimens; 2) ease to perform various conditions of stress (alternate or pulsatory load); 3) possibility to develop studies of fatigue by the recording of the data obtained from different samples of different materials tested, to which any criterion for predicting the fatigue life can be applied; 4) ability to run tests by controlling the amount of deformation; 5) low cost of instrumentation to perform several tests simultaneously; 6) adaptability of the frequency of loading. The purpose of this chapter is to present a material testing machine for fatigue bending stress level that meets all the requirements listed above and to show the results of damage tests of composite material specimens and of the delaminations propagation in bonded joints