Abstract

Variations in the dynamic tire forces of commercial freight vehicles, known to accelerate the road damage, are strongly related to vibration modes of the vehicle associated with vertical and pitch motions of the sprung and unsprung masses. The high levels of tire induced road damage caused by heavy vehicles has prompted a growing demand for the design of road-friendly vehicles. In this study, the enhancement of road friendliness of heavy vehicles is investigated using two methods to control the resonant forces: (i) Determination of optimal asymmetric force velocity characteristics of the suspension dampers to control the tire forces corresponding to the resonant modes; (ii) Optimal design of an axle vibration absorber to control the tire forces corresponding to the unsprung mass resonant modes. An analogy between the dynamic wheel loads and the ride quality performance characteristics of heavy vehicles is established through analysis of a linear quarter-vehicle model to illustrate the potential benefits of optimal damping. A weighted optimization function comprising the dynamic load coefficient (DLC) and the overall rms vertical acceleration at the driver's location is formulated to determine the design parameters of the damper and axle absorbers for a range of vehicle speeds and road roughnesses.