Tham khảo tài liệu 'tyre vehicle dynamics episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | NON-STEADY-STATE STRING BASED TYRE MODELS 241 as found for the slip angle response. Consequently the same cut-off frequency applies. ơ a When analysing the behaviour at small frequencies it appears that here the phase lag does tend to for O rF yf Fịf s s v 7 with the relaxation length for the side force with respect to the yaw angle ơFv ơ a Further analysis reveals that when developing the frequency response function HFm a series up to the second degree in ic j HfJICF GJ1 - FVi OS y bF2ÌCO _ G 1 A 2 _ .G GaG ơFii bF2COs a FC F and subsequently employing the fundamental relationship between a and p responses the frequency response function Hpa up to the first degree in io J. becomes HfÁỈC0 GJ1 - FaiC0 GG1 bF2ÌC0 5-78 which shows that Fa bF2 which is an important result in view of assessing ơFa from yaw oscillation measurement data and checking the correspondence with . The aligning torque -M z Fig. shows a response to the slip angle which is closer to a second-order system with a phase lag tending to a variation around 180 and a 2 1 asymptotic slope of the amplitude with a cut-off frequency equal to ----------- s Ma co f ---------- v 7 yt p a where t denotes the pneumatic trail cf. . Again the response of Fy to p turns out to be the same as the response of -M z to a. As the graph of shows the amplitude of M z as a response to yaw oscillations w exhibits a clear dip at with parameter Ơ 3a a wavelength . 12a. This condition corresponds to the situation depicted in third case and is referred to as the meandering phenomenon or as kinematic shimmy which occurs in practice when the wheel is allowed to swivel freely about the vertical axis through the wheel centre and the system is slowly moved forwards. The nearly symmetric string 242 NON-STEADY-STATE STRING BASED TYRE MODELS LJ RPSOH UHSUHVHQWDWLRQRIVLGHIRUFHDQGPRPHQWUHV SRQVHW deformation explains why the amplitude of the aligning torque almost .
