Vehicular energy losses associated with the traversal of an uneven road
Authors: X. P. Lu, L. Segel
The energy losses which derive from the vibratory phenomenon experienced by a motor vehicle when It traverses an Irregular road surface have been examined. The study has revealed that there are, at least, four “dynamic” energy-loss mechanisms contributing to vehicular rolling resistance. Specifically, it was determined that the energy losses associated with the dynamic deflection of the tire and the stroking of the suspension damper are predicted reasonably well by a linear mass-spring-damper model of a motor vehicle traversing an uneven road surface at constant speed. The energy losses attributable to impacts between tire and road become significant only when the speed is very high or the road is very rough. Finally, measurements have shown that the angular accelerations associated with time-varying radial deflections of the tire will cause an energy loss when the shear forces required to accelerate or decelerate the wheel become larger than can be sustained by the frictional coupling prevailing between tire and road. Fortunately, this particular contribution is small, or negligible, on relatively smooth surfaces. Overall it appears that the additional energy losses attributable to the traversal (at 13 m/s) of a typical primary road in the U.S. are of the order of ten percent of the rolling loss which would occur on an absolutely smooth road surface.