Roll Mode Change Due to Vehicle Speed and Its Effect on Yaw Natural Frequency

This paper classifies roll resonance into two kinds, and points out symbolic solutions of yaw natural frequency at each roll resonance. Firstly, this paper consider change of roll natural frequency ω_x due to change of vehicle speed V. This paper points out that ω_x is a roll mode around the roll axis on the low speed side, and a roll mode around the center of gravity on the high speed side. Furthermore, we define V of this boundary as V_b; V_b is a V where ω_x and yaw resonance frequency ω_n coincide. In addition, V_b of passenger cars is estimated to be about 90 [km/h]. Furthermore, this paper considers an influence of ω_x change on ω_n. As the reference for this consideration, we use the yaw resonance frequency ω_n0 of well-known planar 2 DOF model. In the domain of V < V_b, this paper points out that ω_n is about 1.3 times ω_n0 and derives a symbolic solution of this ω_n. On the other hand, this paper also points out that ω_n is almost equal to w0 in the region of V > V_b. Strictly speaking, this ω_n is slightly larger than ω_n0, which corresponds to the symbolic solution that the author pointed out in the past.