Ride Comfort Analysis

2359 Words 10 Pages
Introduction
The ride comfort concept sweeps over many disciplines in automotive engineering. The vehicle parameters such as suspension spring stiffness and damping coefficient, the temperature control inside the cabin, the ergonomics of the car and many other factors contribute to this quality. When vehicles travel on the irregular roads, they are always subjected to excitation from braking, acceleration and inertial forces on a curved track, which causes discomfort to the driver. The excitation sources for these vibrations can be road roughness, wheel assembly, driveline excitation, engine excitation, aerodynamic forces and transmission excitation. Usually, road roughness will be the major source that excites the car body through wheel assembly
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Internal vibrations are induced by tires, powertrain, and engine, whereas external vibrations are induced by the forces coming from the road. Tires, powertrain, and engine rotate with different velocities and their excitations are characterized with different frequencies. The road- and engine-induced vibrations are the major sources of NVH problems in ride comfort evaluation. A simulation model using seat-back, seat-surface, and feet acceleration values collected from four different road vehicles which were run on six different roads is created for calculating ride comfort effectively. ISO 2631 classifies, the vibrations between 0.5 and 80 Hz according to frequencies that result with discomfort, tire, and health problem, and vibrations between 0.1 and 0.5 Hz result with motion …show more content…
A linear relationship exists between subjective and objective results. The correlation of unweighted, ISO 2631 and BS 6841 weighted values are analyzed to determine which of the methods give good correlation. All three of the methods (unweighted, ISO 2631 and BS 6841) are found to give good correlation as far as the RMS, RMQ, VDV and eVDV values are concerned for vertical acceleration as well as multi-axis translation values. The multi-axis values are however dominated significantly by the vertical acceleration values. All the correlations, except AAP, exhibit a linear trend. The trend for AAP is well defined but non-linear and a big increase in objective value only results in a small increase in subjective value as the terrain roughness increases. The trends for ISO 2631 and BS 6841 are in very good agreement. The difference can be attributed to the relatively small difference in the weighting curves. It can be concluded that the vertical acceleration gives the best, and in fact the only reliable correlation between subjective and objective ride comfort values. The same conclusion can be made from the AAP and VDI 2057 correlation where only vertical values were used. The pitch and roll acceleration of the vehicle body is experienced as vertical acceleration by the respondents and therefore the pitch

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