Chapter 6 - Vehicle Body Roll and Vehicle Dynamics

Abstract

This chapter highlights the roll mechanism, derives the vehicle equations of motion including the roll motion, and studies the effects of suspension system characteristics and vehicle roll on the vehicle motion. In the case of normal passenger cars, the vehicle body and wheels are connected to each other by soft and elastic connections to improve the vehicle ride comfort. This mechanism is generally called the suspension system, and the vehicle body is called the sprung mass, while the wheels are called the unsprung mass. The suspension system between the vehicle body and the wheels allows a relative up–down displacement between the vehicle body and the wheels. When the vehicle moves laterally, a centrifugal force acts at the vehicle center of gravity, causing the vehicle to tilt to the direction of the centrifugal force. This “tilt” is called the vehicle roll. If the suspension system is considered, the vehicle will have a roll degree of freedom that is produced together with vehicle lateral motion. In general, there are various types of suspension systems, from the simple rigid axle type to the independent suspension that is common in passenger cars. The relative vertical displacement or angular displacement between the sprung and unsprung masses is dependant on the structure of the suspension system.