1,721,008 research outputs found
Impiego di tecniche multibody per il miglioramento della sicurezza degli operatori di carrelli a forche
No full textL’elevato rischio per la sicurezza e la salute degli operatori legato alla perdita di
stabilità dei carrelli elevatori a forche, ha causato negli ultimi anni in Italia e in Europa numerosi
incidenti, molti dei quali mortali. In genere tali incidenti sono il risultato di manovre, condotte in modo
non ortodosso, che sfociano nella perdita di stabilità del mezzo, con il rischio consistente che il
conducente rimanga schiacciato tra la struttura del carrello ed il suolo.
Il presente lavoro ha lo scopo di analizzare, dal punto di vista biomeccanico, la funzionalità di diversi
sistemi di trattenimento al posto di guida per conducenti di carrello elevatore, atti a scongiurare tale
pericolo; le prestazioni dei vari dispositivi considerati vengono giudicate sulla base della severità delle
lesioni prodottesi a carico dell’operatore. L’analisi viene condotta attraverso la simulazione dell’evento
accidentale ottenuta mediante il solutore Multibody-FEM MADYMO (TNO Automotive), ideato e
sviluppato per l’infortunistica stradale, che in questa sede è invece, in modo del tutto originale,
dedicato allo studio della dinamica di un tipico infortunio sul lavoro.
L’analisi così condotta, permette di assegnare a ciascuna delle configurazioni esaminate parametri
biomeccanici di funzionalità al fine di pervenire ad una scelta consapevole delle soluzioni da adottar
Stability of an articulated vehicle with suspended cargo
No full textTractor-trailers are widely used to convey. Frequently they are used
for suspended cargo transport, for example in refrigerated vehicles for the
transport of meat. In this work, the stability of equipped articulated suspended
cargo vehicles has been studied. The objective is to characterize possible
conditions of instability that can be induced by the presence of oscillating
cargo. By means of a linear mathematical model of the articulated vehicle, the
critical speed has been determined and of the sensitivity of the critical speed to
the variation of some characteristic parameters of the vehicle has been
analysed. Finally, the improvement is when a passive device of viscous type
was inserted between the tractor and the trailer has been examined
The advantages of using continuously variable transmissions in wind power systems
No full textWhen connected to appropriate electric power generators, wind turbines may be used to produce electric energy. This may become complicated because wind speed tends to change. Traditionally, electric power was produced by electric generators connected to mechanical devices whose movement could be perfectly controlled and adapted to user's needs by special governors. This paper explores the feasibility of incorporating a continuously variable mechanical transmission between a wind turbine and an electric generator. Such a system would allow the turbine to operate at maximum efficiency levels and the generator to produce electric power at a desired frequency without using other devices. A mathematical model has been used to simulate a system formed by a wind turbine connected to an induction generator by means of a continuously variable transmission. The simulation was aimed at assessing whether the system was stable and attempted to adjust the transmission in order to ensure the required power suppl
Continuously variable transmissions with a torque sensing regulators in waterpumping windmills
No full textOne widespread application of wind energy is in waterpumping. Usually windmills are coupled to water pumps, though piston pumps are difficult to match to wind turbines. In the first approximation, the piston pump requires a constant torque to the turbine at all rotational speeds. Conversely, if the turbine were to operate at maximum efficiency levels, it would supply a torque proportional to the square of the wind speed. Hence, the combination of windmill and piston pump would be maximally efficient only for a single wind speed. This paper suggests incorporating a continuously variable transmission (C.V.T.) between the pump and the turbine to enhance the efficiency of windpumpers at different wind speeds. The feasibility of adopting automatically regulated C.V.T.s, which adjust their transmission ratio to the torque without requiring sophisticated regulators or control systems, is also examined since such a solution does not undermine the cost-effectiveness, reliability or simplicity of the system. A mathematical model has been relied on to simulate the operation of a windpumper equipped with a C.V.T. with a torque sensing regulator. The advantages in terms of efficiency and rate of flow of such a solution are demonstrated assuming that a waterpumping system equipped with a C.V.T. is installed in two locations in Somalia. Finally, the paper examines the dynamic behaviour of the system propose
Dynamic behaviour of wind power systems equipped with automatically regulated Continuously Variable Transmission
No full textHigh efficiency levels may be attained by wind turbines operating at varying speeds when the machine is made to run at a constant tip speed ratio. Previous papers have suggested incorporating a continuously variable transmission (c.v.t.) to achieve this purpose. Following the general recommendation of using efficient, reliable and economical technologies in wind power systems, one of these papers investigated whether a V-belt c.v.t. with automatically adjustable speed was compatible with a wind power system. The investigations in this case were carried out under steady-state conditions.
In this paper, the behaviour of a wind power system equipped with a c.v.t. will be examined in turbulent wind conditions using a dynamic model. The simulation results will show that, when the actual wind speed fluctuations are taken into account, incorporating a c.v.t. between the turbine and the electric generator yields greater advantages in terms of energy output than it does when the system is assessed in the steady-state. The better quality of the electrical energy supplied will be examined and compared to that produced by a constant speed system. Finally, the behaviour of a wind power system equipped with a c.v.t. will be assessed as the temporal characteristics of the wind gusts chang
A mixed analytical-multibody-BEM approach for predicting the sound power level of a hydraulic impact hammer
No full text- …
