Abstract
In order to analyze the stability of middle range trucks and bus on wheel tread tracks, we constructed vehicle model which contained unsprung mass, lateral displacement of unsprung mass, compliance in steering system and roll steer. At first, we linearized the effect of wheel tracks and examined the stability of wandering behavior. Using this equation of motion, we analyzed the effect of design parameters for vehicle and also of the dimension of wheel tread track. For the result of simulation, we confirm that the roll steer has strong effect to wandering behavior not only from linear analysis but also from nonlinear analysis.