EVALUATION OF COMFORT FOR PASSENGERS OF RAILWAY VEHICLES EVALUATION OF COMFORT FOR PASSENGERS OF RAILWAY VEHICLES

The passenger’s complex sensation felt during the application of oscillations and/or inertia forces, via the whole-body transmission is defined and evaluated with the help of comfort indexes such as a mean comfort; mean permanent sensation evaluated according to the measurement procedures for the indexes, and comfort on curve transition, discomfort due to a perceived curve entry or reverse transmission, or comfort on discrete events - discomfort, due to a perceived transient oscillation on a straight track, curves and curve transitions. In the text the authors deal with mean comfort evaluation and its qualification with the help of the Comfort Indexes.


Introduction
The comfort of passengers in a vehicle is influenced by a number of different factors, for example temperature, noise, vibration etc. The paper considers only that part of the comfort influenced by dynamic behaviour of the vehicle. This part of the comfort is described as Ride Comfort or as Comfort. The European standard summarises the relevant works taking into account the effects on ride comfort for passengers from the vibration exposure measured on the car body floor (the simplified method for Mean Comfort evaluation), taking into account the vibration exposure measured on the interfaces (the complete method for evaluation) and taking into account the effects on Ride Comfort for passengers of discrete events (Comfort Discrete Events) and running on curve transitions (Comfort on Curve Transitions).

Ride comfort
The ride comfort for passengers, or ride comfort is the complex sensation produced on the passenger by car-frame movements of the vehicle transmitted to the whole body through the interfaces.
The sensation is classified as: • average sensation: based on the vibration applied on a long-time basis (at least some minutes), • instantaneous sensation: a sudden modification of the average sensation, due to a short basis event (change of the mean lateral acceleration value, roll movement at significant speed, lateral jerk with possible oscillation).
Both the first and the second type of sensation are taken into account in the Mean Comfort evaluation. The second type of sensation is taken into account in the Comfort on Curve Transitions and in Comfort of Discrete Events.
The quantification of Ride Comfort for passengers is performed through simulation computations [2,4,6,7] or trough indirect measurements, i.e. measuring and post-processing the relevant parameters (accelerations and angular velocity, they were measured in the car-body).

Input parameters
The quantification of Ride Comfort for passengers is performed through indirect measurements, i.e. measuring and post-processing the relevant parameters (accelerations and angular velocity, they were measured in the carbody). Other types of tests and evaluation, such as a direct test based on the direct assessment of the perceptions of tested passengers, and combined tests including both direct and indirect tests are possible as well, but they are not quantified in [1]. The indirect measurements are classified as simplified or complete if the measurements are taken respectively on relevant points of the carbody floor, or also on the interfaces. When travelling, the passengers' bodies are influenced by vibration due to dynamical movement of a vehicle.
Passengers are people travelling in a vehicle, without specific activities related to the transport.

Ride comfort for passenger evaluation
Comfort is the complex sensation produced on the passenger during the application of oscillations and/or inertia forces, via the whole-body transmission caused by vehicle -frame movements. It is defined and measured through comfort indexes as: • Mean comfort: a mean feeling, continuously adjusted, as evaluated through a measurement following the procedures for comfort index N MV and indexes N VA and N VD .

EVALUATION OF COMFORT FOR PASSENGERS OF RAILWAY VEHICLES Juraj Gerlici -Tomas Lack -Zuzana Ondrova *
The passenger's complex sensation felt during the application of oscillations and/or inertia forces, via the whole-body transmission is defined and evaluated with the help of comfort indexes such as a mean comfort; mean permanent sensation evaluated according to the measurement procedures for the indexes, and comfort on curve transition, discomfort due to a perceived curve entry or reverse transmission, or comfort on discrete events -discomfort, due to a perceived transient oscillation on a straight track, curves and curve transitions. In the text the authors deal with mean comfort evaluation and its qualification with the help of the Comfort Indexes.
• Comfort on Curve Transition: discomfort, due to a perceived curve entry or reverse transition, quantified by the recommended procedure indicated as comfort index P CT . • Comfort on Discrete Events: discomfort, due to a perceived transient oscillation on a straight track, curves and curve transitions, qualified by the recommended procedure indicated as comfort index P DE .
The contact area is compounded from the contact parts between the carbody and the passenger with the function of sustaining and guiding the passenger and of transmitting the weight of the same passenger to the carbody itself; In the standing position (floor-feet), in the seated position (headrest -neck, arm rest -upper arm, seat -hip, seat -back, floor -feet), Whole-body transmission: this is an action transmitted to the whole body through the interfaces.

Indirect measurements/tests features:
This is a measurement or test or part of tests based on measurement and post-processing of the relevant parameters (acceleration and roll speed measured in the carbody).
Complete measurements are composed of measurements at the positions in accordance to [1,5,8]: • measurements on interfaces, • measurements on carbody floor, near to the seat. The complete method is more highly correlated with the passenger's perception of comfort than the simplified method. For a general assessment of the ride comfort of a railway vehicle, the simplified method shall be used. For a full assessment of the ride comfort of vehicles (with a view to the passenger's perception of comfort), it is recommended that the complete method is used where needed.
The simplified method of the Mean Comfort assessment can be performed through the following procedures: • oscillation measurement, • results of measured data evaluation, • list of requested track characteristics for vehicles, • test protocol form.
To find out effective values of weighted accelerations the registered signals must be elaborated with the help of the following methods: analogous, hybrid (analogous in connection with digital) or digital. In order to take into account the different degrees of sensitivity displayed by different individuals as a function of frequency, weighting curves have been established for vertical and horizontal acceleration signals. These curves are defined in tables [1,5]. The curves were determined for sinusoidal vibrations; they are considered valid for broad-band stationary vibrations. Although each individual has his own weighting curves, the curves selected are optimum curves for assessing mean vibration comfort. Weighting curves are defined by mathematical analytical formulae. Their purpose is to modify the final values of numerical elaboration of measured data as to emphasize crucial information which we want to achieve from the measured signal and at the same time to suppress non-essential information for the final value.

Ride comfort computation
There are measured accelerations in the directions of separate coordinate axe a x , a y , a z [3,5,9]. There is given a measured frequency of f n . On the base of the frequency we state a number of samples which we scan within the time interval of 5 seconds. At the scan frequency of 200 Hz we acquire 1000 samples in five seconds. On the base of occurrence samples condition in 5 -second -time interval we divide the complete time of scanning (acquisition of samples) into 5 -second -time intervals following each other.
Each interval has in time strictly determined its begin T 1 and the end T 2 .
In this way we stated a number of data blocks. On the base of sampling frequency and time of 5 seconds we determine a number of scans which should be present in the given interval. For a further numerical elaboration it is necessary that this value be a multiple of two. In the case that it is not the above mentioned multiple we substitute it by the nearest higher value which is the multiple of two.
We do the Fast Fourier Transformation (FFT) for a file of data in each time interval defined by T 1 and T 2 .
We do the computation CAW for the frequency range from 0.4 Hz to 80 Hz.
We apply the weighting filter w in dependence on the type of evaluation (floor, standing, seated).
Parameters coefficients for weighting curves evaluation Table 1 Weighting frequency range Weighting curve parameters In a statistical way we evaluate acceleration values modified by the weighting function in corresponding directions and we determine summating functions in histograms.
aWx 50 ϭ acceleration value in the direction x multiplied by the weighting function Wx at 50% quantile of the summating function.
We state the final values of ride comfort indexes for passengers from the following formulae.
Similar expressions can be written for a sitting person comfort index evaluation.
The other expression

Conclusion
The evaluation of ride comfort for passengers is an extremely current issue. A subjective feeling of comfort when travelling is often the decisive criterion which influences the traveller -passenger when choosing a means of transport. Except for economic influences which arise from preferring or refusing some of transport means in the frame of transport system of a country or region, the level of transport system development has a direct  ⏐C и C*⏐ ᎏ ᎏ ᎏ 2

Fig. 5 The acceleration spectrum in the coordinates axe directions is depicted
The aim of comfort evaluation procedures by the indirect method (acceleration measurements) and by statistical evaluation is to achieve a concrete number, a comfort index which, when doing the analysis, takes into consideration the quality of the couple vehicle/track and it is not influenced by subjective feelings of individual passengers.