is a heavy-duty solution so it had to
be a robust, rugged transmission,” he
noted. “It had to have the appropriate
communication protocol, meaning the
transmission could be controlled with
an outside smart controller. The actual
control laws and the way it shifts as
part of the hybrid system, that’s done
by our system controller. We needed
to make sure there was compatibility
from that perspective.
“We also had a need from a cost
standpoint to fit the price point we
were considering to meet the payback
aspect in terms of why a customer
buys a hybrid truck.”
BAE Systems estimates that pay-
back for the HybriDrive parallel sys-
tem is less than five years in the
targeted vocations and duty cycles.
The parallel drive system is designed to support vehicles with big-bore engines ranging from 350 to 600
hp and with torque ratings from 750 to
1750 lb.ft. The system supplies 94 to
145 hp of electric propulsion, depending on model, and 300 to 600 lb.ft. of
The parallel system is based upon
a single electric machine that is situated between the engine and the CX
transmission. The electric machine is
composed of a stator and rotor supplied by Remy, an Indiana-based supplier of electric motors and systems
for hybrid applications. BAE Systems
has a 10-year supply agreement with
Remy for electric motor components.
The electric machine acts as both
an electric motor and a generator. As
a motor, it provides torque to the driveline to help propel the vehicle. It works
as a generator when the vehicle is
slowing or braking. Energy recovered
during regenerative braking is stored
in a battery pack for later use when
additional energy is needed, such as
when climbing a hill or accelerating.
Four models of Cat CX transmissions
are being used with the HybriDrive parallel system. They are paired with either
a 70 or 110 kW electric machine and
PTOs to power electronic accessories
onboard the vehicle, all of which were
previously belt driven.
“Depending on the size of the truck,
the vocation and duty cycle, we will
marry one of the two electric machines
with one of the four transmissions to
provide the best torque, power capabil-
ity and fuel savings,” said Mekhiche.
“We keep the battery and electronics
common across the different variants.”
The electric machine, transmission,
cooling system and two clutches are all
part of the Integrated Drive Unit (IDU).
One clutch is positioned on the side
of the transmission to disconnect the
electric machine from the transmission.
The second is located on the side of the
engine, de-coupling the engine from
the driveline, thus allowing the truck to
operate as an all-electric vehicle.