1993-03-01

Seat Dynamic Parameters for Ride Quality 930115

Humans are most sensitive to low frequency whole body vibrations often associated with roadways. As a result, improvement of vibration characteristics is an important aspect of vehicle design. While much research has been performed on active suspensions and their role in ride quality, comparatively little has been performed on seat dynamics. This paper develops a method of selecting optimal seat dynamic seat parameters with respect to ride quality. A nine degree of freedom dynamic vehicle simulation model is presented. An optimization procedure, using absorbed power as the objective function, then minimizes rider discomfort by manipulating the seat dynamic parameters. A two degree of freedom seat model yields four design variables, including seat suspension stiffness and damping and seat cushion stiffness and damping. The optimization problem is solved for several road inputs and two different vehicle models. The road inputs include actual road profiles, as well as common road test elements like sine waves and chuck holes. The vehicle models include a typical passenger car and utility-type vehicle. The results indicate that cushion and suspension stiffness and suspension damping are the most important factors influencing ride quality. The objective function was found to be relatively insensitive to cushion damping. The most critical parameter was determined to be the seat suspension damping. Design charts are provided which may be used in an active seat suspension application.

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