tailieunhanh - COMFORT PERFORMANCE

The definition of comfort in a motor vehicle is at once complex and subjective, changing not only with time (cars considered comfortable just twenty years ago are nowadays considered unsatisfactory) but also from user to user. The same user may change his appraisal depending on circumstances and his psychophysical state. But comfort remains an increasingly important parameter in customer choice and strongly competitive factor among manufacturers. This chapter will deal primarily with vibrational comfort, although it is difficult to separate it from acoustic comfort without entering into details linked more with the driveability and handling of the vehicle. Not just. | 26 COMFORT PERFORMANCE The definition of comfort in a motor vehicle is at once complex and subjective changing not only with time cars considered comfortable just twenty years ago are nowadays considered unsatisfactory but also from user to user. The same user may change his appraisal depending on circumstances and his psychophysical state. But comfort remains an increasingly important parameter in customer choice and strongly competitive factor among manufacturers. This chapter will deal primarily with vibrational comfort although it is difficult to separate it from acoustic comfort without entering into details linked more with the driveability and handling of the vehicle. Not just driving comfort but vibrational and acoustic comfort as well the latter deeply affects the conditions in which the driver operates all have a strong impact on vehicle safety. It is possible to distinguish between vibrational and acoustic comfort linked with the vibration and noise produced inside vehicles by mechanical devices or on its surface by the air and ride comfort which is linked primarily with the ability of the tires and the suspensions to filter out vibration caused by motion on a road that is not perfectly smooth. With this distinction in mind SAE defines ride low frequency up to 5 Hz vibration of the vehicle body shake vibration at intermediate frequency between 5 and 25 Hz at which some natural frequencies of subsystems of the vehicle occur G. Genta L. Morello The Automotive Chassis Volume 2 System Design Mechanical Engineering Series Springer Science Business Media . 2009 349 350 26. COMFORT PERFORMANCE harshness high frequency vibration between 25 and 100 Hz of the structure and its components felt primarily as noise noise acoustic phenomena occurring between 100 Hz and 22 kHz . up to the threshold of human hearing. INTERNAL EXCITATION The sources of vibration on board a vehicle are essentially three The wheels the driveline and the engine. All contain .