  A 4-independent wheel driving (4-IWD) electric vehicle has distinctive
advantages with both enhanced dynamic and energy efficiency performances since
this configuration provides more flexibilities from both the design and control
aspects. However, it is difficult to achieve the optimal performances of a
4-IWD electric vehicle with conventional design and control approaches. This
work is dedicated to investigating the vehicular optimal design and control
approaches, with a 4-IWD electric race car aiming at minimizing the lap time on
a given circuit as a case study. A 14-DOF vehicle model that can fully evaluate
the influences of the unsprung mass is developed based on Lagrangian dynamics.
The 14-DOF vehicle model implemented with the reprogrammed Magic Formula tire
model and a time-efficient suspension model supports metric operations and
parallel computing, which can dramatically improve the computational
efficiency. The optimal design and control problems with design parameters of
the motor, transmission, mass center, anti-roll bar and the suspension of the
race car are successively formulated. The formulated problems are subsequently
solved by directly transcribing the original problems into large scale
nonlinear optimization problems based on trapezoidal approach. The influences
of the mounting positions of the propulsion system, the mass and inertia of the
unsprung masses, the anti-roll bars and suspensions on the lap time are
analyzed and compared quantitatively. Some interesting findings that are
different from the `already known facts' are presented.
