Abstract
One of the most important aspects of the design activity of passenger railway vehicles is the optimization of the comfort level that is often in contrast with other requirements, such as low weight, to reduce energy consumption, and high and flexible seating capacity. Due to the coach weight reduction, the car body structure becomes more susceptible to structural vibrations that affect the passenger comfort. In modern vehicles, seats are important elements to achieve the desired comfort, but in order to design and estimate the actual comfort level, the whole system must be considered, including the track excitations, a vehicle detailed dynamic model, and the coach and the seat flexibility. This paper describes a numerical model of a double-deck vehicle developed using a MB code that considers measured track irregularities, a detailed vehicle model, and a transfer function of the seat obtained by experimental tests on an optimized seat. In order to make the numerical model more realistic, the coach has been modeled as a flexible body to consider the effect of its natural frequencies. The work has been performed within the “CARITAS” project, whose aim is the design of a high comfort vehicle for people with reduced mobility.
Highlights
The work has been performed within the “CARITAS” project, whose aim is the design of a high comfort vehicle for people with reduced mobility
One of the most important aspects of a railway vehicle is to guarantee a high comfort level, especially if the vehicle is used for the transportation of people with reduced mobility
It is evident that the coach flexibility more affects the vertical acceleration, especially on the upper floor and on the central ground floor, where several modes are excited by the track irregularities
Summary
One of the most important aspects of a railway vehicle is to guarantee a high comfort level, especially if the vehicle is used for the transportation of people with reduced mobility. Noise level in the coach is instead mainly affected by vibrations with a frequency range between 30 Hz and 5000 Hz. The evaluation of the vehicle comfort is usually performed by means of multibody simulations, where the coach is modeled as a rigid or a flexible body. The mass reduction results in larger structural vibrations in the frequency range where the human body shows greater sensitivity [4, 5] For this reason, several models considering a flexible coach have been developed. The second method, instead, allows considering this effect and so it is suitable when it is necessary to consider the vibrations of the floor, which have an important role in the coach acceleration, as demonstrated in [1] The results of those studies demonstrate that the coach flexibility affects the estimation of the comfort index. Their limitation is based on the fact that the comfort estimation is made on the floor, neglecting the influence of the seat
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