The Mechanism of Vehicular Rolling Resistance on Uneven Roads (Random Vibration, Fuel Economy, Energy Loss).

A dynamic modeling and experimental study dealing with vehicular rolling losses on uneven roads is described. The modeling effort consists of two parts: linear and nonlinear. In both cases, the relationship between vehicular rolling resistance, road roughness characteristics, tire-vehicle properties, as well as the vehicle operational condition is studied. In the analysis, the vehicle is represented as a one-quarter vehicle traversing a random profile. The tire, on the other h and , is modeled as a combination of many independent hysteretic segments, and the work performed on each segment as it passes through the contact patch is formulated for different cases. By adding together the energy losses due to (a) hysteresis in the tire, (b) suspension damping, and (c) impact, the vehicular rolling loss is determined. In this analysis, the enveloping characteristics of a tire are represented as a transfer function between the road elevation associated with distributed tire stiffness, and effective road elevation associated with concentrated tire stiffness. Experimental verification of the findings predicted by the analysis was conducted with a single tire-wheel-suspension system loaded against a 1.7 m diameter drum. Measurements of rolling resistance were made on a smooth drum for subsequent comparison with the measurements obtained when the tire-wheel-suspension system is forced to roll over an uneven surface which is created by mounting aluminum sheets on the surface of the drum. The study presents findings to demonstrate that vehicular rolling resistance is a function of four energy-dissipation mechanisms: (1) Smooth surface rolling resistance; (2) Energy dissipation in the tire due to road roughness; (3) Losses in the suspension system due to relative motion between sprung and unsprung masses; and (4) Impact loss between tire and road. These mechanisms are defined in mathematical terms and their relative importance is established on a quantitative basis.Ph.D.Mechanical engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160559/1/8512461.pd