Vehicle Electrification - June 26, 2013 - 26

Next-gen eAssist
aims at cost reduction
first two generations of the system, and the
knowledge gained since 2006 has allowed
the engineers to “sharpen our pencils a bit”
for the Gen-3, he said.
“Exactly how much battery is required to do
this job? Can we do it with less?” Poulos
asked rhetorically. “As we go to the next generation we’re expected to be a bit more parsimonious with what we’re doing.” He indicated that transitioning to a less expensive,
smaller, and lighter battery requires devising a
more effective energy-management strategy,
which could include adding battery-warming
technology “and other things to stretch it.”
GM’s development of a nine-speed automatic transaxle for front-drive vehicles provides some opportunity for eAssist, along
with technical challenges.
“More gears give us the ability to do more
with smaller engines, for sure,” Poulos observed. “And the ability to stay in a higher
gear is still there if you can provide electric
boost. If base engine power is decreasing,
the contribution from the electric boost becomes a larger proportion. Also, smaller engines tend to spin faster and they’re noisier,
but there are ways to mitigate that by keeping
the engine running at a lower speed.
“I’d say more gears beyond the current sixspeed is architecturally helpful for us, but execution is more difficult, including calibration,” he said.

Designing for ubiquity
As GM develops its next-generation vehicle
architectures and “faces that low-CO2 zone,”

June 26, 2013

as Poulos calls the new regulatory environment, engineers are laying out future platforms and body structures to accommodate
a variety of electrified propulsion systems. For
eAssist, that geography affects the engine
compartment hardware, electrical cabling,
and the battery module and its thermal management system located on the rear cabin
bulkhead.
“The debate that’s going on now is about
how to protect for it,” he said. “What’s important is to have a long-term vision of this technology, so when we get to those architectural
decisions we do the right things. That’s how
you can save money.”
That said, Poulos noted that future versions
of eAssist “will be better suited to the vehicle
applications they’re going into,” as well as
being lighter and more package-efficient. The
latter includes less impact on passengercompartment and trunk volume, as some
customers have requested. “We’d like to get
to the point where we just bolt this stuff in the
car,” he stated. “We’re not there yet.”
One key element of the system getting attention is the sophisticated belt-drive arrangement. The main focus is developing a
Bill of Design for Gen-3 that is “more mature,
robust, and easier to use, because if you
want [eAssist] to go into lots of applications,
you don’t want to spend a lot of development
time tweaking these things to get them just
right for each one.”
Longer term, the designers would like an
alternative to belt drives. But the eAssist evolution has reached a state where “if somebody says, ‘Put it on that engine,’ we hook it
up and in one shot we’re 90% there with a
small amount of tweaking,” Poulos said.

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Vehicle Electrification - June 26, 2013

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