Abstract
This paper considered the root loci plot when the velocity was changed by using 3 degree of freedom (D.O.F) model consisting of plane 2 D.O.F motion and roll 1 D.O.F motion. As a result of the parameter study, this paper pointed out that the two root loci may become double roots in a case. On the lower speed side than the vehicle speed at which the double root occurs, the yaw natural frequency was about 30% larger than that of the 2.D.O.F plane model. Thus, an approximate expression of the yaw natural frequency in this vehicle speed range was proposed.
