Effect of Road Roughness on the Vehicle Ride Comfort and Rolling Resistance

Road roughness is a very important consideration in evaluating the condition of a given roadway, as it affects the ride comfort for the passenger and vehicle operating cost. This paper deals with an investigation of the influence of road roughness on the vehicle ride comfort and vehicular rolling resistance. The rolling resistance power losses is also investigated. A mathematical model of a quarter vehicle is developed to evaluate vehicle ride comfort in terms of suspension performance criteria. The performance of each suspension system can be assessed quantitatively in terms of discomfort (Acc), suspension working space (SWS) and dynamic tyre load (DTL). The effect of road roughness on the vehicular rolling resistance coefficient is also discussed. The ride performance, power consumed in rolling resistance and power dissipation in suspension for passive and switchable damper suspension systems are finally evaluated. The vehicle itself is treated as a rigid body undergoing vertical motions. The vehicular rolling resistance on road roughness consists of three parts, the rolling resistance of a tire on an absolutely smooth road and that due to road roughness variations and suspension motion.

The obtained results showed that ride comfort deteriorates when road roughness coefficient is increased. The rolling resistance coefficient is not a constant but varies with the road roughness coefficient and the vehicle speed. When road roughness coefficient is increased the rolling resistance force induced by road roughness increases too. The rolling resistance power losses is discussed. Comparisons between passive and switchable damper suspensions systems in terms of ride performance and power dissipation are also discussed.