4.2 Simulation results
Following the above discussions, a simple
cycloid curve, ws(t) =Y (t), was selected as a
desired trajectory for smooth slip shift. From Eq.
(9), the clutch torque for this shift can be given
by u (t) = (an-y'(t»/ /3n'
Desired clutch torque for smooth torque shift is
chosen so that u (t) =YeU) or u (t) =YdU), The
corresponding slip speed and vehicle acceleration
during the shift may be obtained from Eq. (9)
and Eq. (8b), respectively. Desired trajectory for
the smooth acceleration shift will be either avU)
=Yd(t) or av i.t) =Yc(t) depending on the desired
shift completion time and shift condition. The
clutch torque for effecting this shift can be determined
from Eq. (8b).Simulation results of each shift are shown in
Fig. 4 for various curve parameters. A shift completion
time was set at 3 sec. for visualization
purpose. However, short shift time does not siginficanfly
affect the response. Desired curve for
smooth torque and acceleration shift may be
selected according to the area requirement based
on the required shift completion time and the shift
condition. All of the plots in the figure show
smooth transients except for the initial jerk at the
beginning of the smooth slip shift. It is due to the
fact that the initial clutch torque, u (0) = ani (3n =
TEm of this shift is less than the initial engaged
clutch torque TEO' Note that the torque shift and
acceleration shift show the same effect even
though their concepts are different. The reason is
that the clutch torque directly drives vehicle inertia,
which in turn induces vehicle acceleration.