3.1. ROLL INDEX OF UNTRIPPED VEHICLE ROLLOVER 25
1.5
1.25
1.158
1.0
0.5
0
0 1.0
Time (s)
Lateral Acceleration (g)
1.5 2.00.5
(c) U = 16 m/s
Roll Motion in Cornering
SSF Boundary
DSF Boundary
Figure 3.3: (Continued.) Lateral acceleration of roll motion at three forward speeds.
second item of DSF has nothing to do with the track width T
w
, but inversely relates to the
center of gravity H . us, decreasing H receives better improvement on vehicle stability
than increasing T
w
, as shown in Figure 3.4, while SSF does not show this tendency.
3. DSF takes the longitudinal location of the center of gravity into consideration. As section
(b), when wheelbase L is fixed as constant, substituting b D L a into the second item of
DSF yields a function f .a/. is is a decreasing function to variable a. erefore, moving
the center of the sprung mass close to the front axle can improve the stability of vehicle
rollover, as shown in Figure 3.5.
4. DSF takes the forward speed and the steering angle into account. From Equation (3.3),
DSF increases with the decreasing of the forward speed U and the front wheel-steering
angle ı. erefore, this evidence enables one to improve the stability of vehicle rollover by
using either a low speed or a small steering angle, as shown in Figure 3.6.
5. DSF varies from the equivalent roll stiffness of the suspension, as seen from Equa-
tion (3.3). It is reasonable to expect that enhancing this fact enables one to improve the
stability of vehicle rollover, as shown in Figure 3.7.
6. Furthermore, DSF includes the effects of the properties of tires on vehicle dynamic sta-
bility. e ratio of the cornering stiffness of a front tire and the rear as
1
D k
f
=k
r
and
substituting it into the second item of DSF yields a function f .
1
/, which is a decreas-