1984-09-01

A Vehicle Design Optimization Problem Associated with Rolling Resistance Reduction 841237

This paper addresses vehicular rolling resistance reduction in conjunction with improvement in ride comfort and road holding ability in a simplified vehicle design optimization problem.
The three vehicle performance indices mentioned above are represented respectively by the values of vehicular rolling resistance force (VRF), root mean square of vehicle body vertical acceleration (RAC), and root mean square of dynamic load between tire and road (RDL).
The summation of VRF, RAC, and RDL associated with corresponding weighting coefficients is treated as the objective function to be minimized.
A model for determining rolling resistance of a vehicle traversing an uneven road is presented. In this model vehicular rolling resistance force is treated as a function of the power spectral density of road elevation input. The linear vehicle system is represented by vehicle parameter dependent transfer functions.
Ideal vehicle parameter values determined from the viewpoint of vehicular rolling resistance reduction will not necessarily be the same as those determined from the viewpoint of other performance requirements; for instance - ride comfort and road holding ability.
Compromise among these conflicting requirements is examined. The level of emphasis placed on the various performance requirements is represented by different combinations of the values of the corresponding weighting coefficients. The objective function associated with some physical design constraints for a linear quarter vehicle and specified operational condition (road roughness and vehicle velocity) is computed by Generalized Reduced Gradient Optimization Technique.
The influence of different combinations of weighting coefficients on optimal vehicle parameters and resulting performance indices (ride comfort, road holding ability and rolling resistance) are presented and discussed.
Rolling resistance of a vehicle traversing rough roads could be reduced considerably by using this method. It is possible that when fuel economy achieved while operating on a rough road is a primary design consideration, “vehicular rolling resistance reduction” could be treated as one of the parallel vehicle performance indices in optimal design consideration.

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