Various methods for evaluating ride quality in automobiles are investigated by means of a field study involving two different automobiles, seventy-eight different passengers, and eighteen different raodway sections. Passenger rating panels were used to obtain subjective evaluation of the various rides, and measured vibration spectra were examined on the basis of various frequency weighting techniques to determine their ability to predict the subjective ratings. Included in the evaluation criteria considered are weighting functions derived from the ISO (International Standards Organization) Standard, the UTACV (Urban Tracked Air Cushion Vehicle) Specification, and the Absorbed Power method of Lee and Pradko. Excellent correlation was found to exist between the subjective ride ratings and simple root mean square acceleration measurements at either the vehicle floorboard or the passenger/seat interface. Equations are presented to predict the subjective ride rating from measured vibration spectra.
This paper presents the results of an analytical and experimental study of ride vibrations in an automobile over roads of various degrees of roughness. Roadway roughness inputs were measured. Three different linear mathematical models were employed to predict the acceleration response of the vehicle body. The models used included two, four, and seven degrees of freedom, primarily for vertical direction motion. The results show that the prime source of errors in predicting responses of this type lies in the common assumptions made for roadway roughness spectra. With adequate description of the roadway inputs, the results showed that the seven degree of freedom model accurately predicted the low frequency response (up to 10 Hz). Using the seven degree of freedom model, predicted accelerations compare well with measured data for a wide range of roadways in the low frequency range. Higher frequency components in the measured acceleration response are significant and are illustrated here.
Analyses are developed to determine the dynamic performance of vehicles interacting with single, multiple, and continuous span elevated structures. Operating conditions in which multispan resonant conditions occur are identified, and the resulting resonant amplitudes computed. Guideway design examples considering tracked, levitated vehicles are described to illustrate the influence of span configuration and vehicle speed and suspension properties upon guideway span design for vehicle-guideway systems required to provide specified passenger comfort levels. For the 150 and 300 mph (242 and 483 km/h) vehicle systems considered, continuous and multispan guideway configurations were found to have reduced span material requirements in comparison to single span systems which provide the same level of passenger comfort.
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