Parallel Hybrid Vehicle Design*
Hybrid
electric vehicles (HEVs) combine the internal combustion
engine of a conventional vehicle with the battery
and electric motor of an electric vehicle. This combination
offers the extended range and rapid refueling that
consumers expect from a conventional vehicle, with
the significant energy savings and environmental benefits
of an electric vehicle.
The
practical benefits of HEVs include improved fuel economy
and lower emissions compared to conventional vehicles.
Hybrid power systems were conceived as a way to compensate
for the shortfall in current battery technology: batteries
can supply only enough energy for short trips.
An
HEV with a parallel configuration has a direct mechanical
connection between the engine and the wheels, as in
a conventional vehicle, but also has an electric motor
that drives the wheels simultaneously, that is "in
parallel." For example, the vehicle can use the (relatively
constant) power produced by the engine for constant-
speed driving and the electric motor for accelerating
and decelerating.
An
HEV is essentially an electric machine that can electronically
``balance the engine'' (function as an electronic
flywheel), start the engine, and convert engine power
into electricity. It can also provide extra power
to the drive train when needed for hill climbing or
quick acceleration.
The project objective is to determine, for a given
vehicle size and driving pattern, what is the optimum
relative power balance between the internal combustion
engine and the electric motor. It is desired to maximize
fuel economy --- which we assume corresponds to the
minimum pollution --- subject to the constraint that
the
vehicle 'handling' should be comparable to a conventional
vehicle.
The
ideal completed project deliverable would be a generic
mathematical model that, given vehicle size, EPA driving
patterns, and handling characteristics, will decide
the optimum power ratio between engine and
motor. This is a large project and must be pruned
to some interesting but useful portion.
*This
summary prepared by R. E. Svetic and C. R. MacCluer
with the assistance of Dr. P. J. McCleer, President,
McCleer Power Incorporated, Jackson, Michigan.
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