Automotive Engineering - December 2022 - 14

TECHNOLOGY REPORT
ELECTRIFICATION
Tula's DMD promises gains in EV efficiency
tor, operating in its most efficient range
for longer periods of time. However, instead
of turning cylinders on and off,
Tula pulses the motor at the highest efficiency
point for a given speed and load.
There is no rotor current during DMD
" off " pulse and the system operates
" downstream " from the battery.
" The electric motor has the same
Tula's Dynamic Motor Drive
(DMD) pulses the electric motor
to optimize system efficiency.
Nestled in San Jose, California just
south of the San Francisco Bay, the
small but mighty team at Tula
Technologies continues to develop advancements
for optimizing the efficiency
of ICE and electrified powertrains.
SAE Media recently visited its facility to
speak with the engineering leadership
and test drive vehicles equipped with
their latest innovations.
Tula's goal is to let the motor (regardless
of fuel type) " operate where
efficiency is the highest and vary the
frequency of operation to provide the
desired output. " To that end, the company
already has systems in the market
and in high states of development to
increase the efficiency of ICE and electrified
vehicles. The best known of these
is Dynamic Skip Fire (DSF) which is currently
in use on several production
General Motors V8s.
Dynamic Motor Drive for EVs
Tula's latest innovation in increased propulsion
efficiency targets the EV sector.
The company's Dynamic Motor Drive
(DMD) was first covered by SAE in 2020
(https://www.sae.org/news/2020/12/
tula-dmd-aims-for-more-efficient-e-machines).
The system is now much further
along in development, leading Tula to
claim efficiency gains - a 25% reduction
of losses in externally excited synchronous
motor systems as well as a 3% gain
in efficiency in battery and energy costs.
Tula's DMD system utilizes modulated
torque or " pulses " to keep the
14 December 2022
electric motor in its most efficient operating
range. The concept is remarkably
similar to the tech Tula has used to increase
the efficiency of IC engines.
" It was clear that our passenger car
market was being disrupted, " Scott
Bailey, Tula's president and CEO, noted
on what spurred DMD development.
" If
you added up what the global auto industry
was investing into electrification
in 2020, it totaled about $300 billion.
Two years later, that total is over $515
billion. So, the momentum in the market
is continuing to shift. We knew our DSF
passenger-car market was going to be
significantly disrupted. "
Work on the DMD system began in
2018 but has accelerated significantly in
the past six months. Like Tula's other
systems, the goal is to keep the propulsion
system, in this case the electric mofundamental
efficiency sweet spot as an
IC engine " , Bailey said. " How you access
that sweet spot is different, but there is
an area of highest efficiency and if you
can find a way to operate in that area
more often, the same fundamental control
philosophy applies. "
The company states that DMD can
deliver up to a 25% loss reduction in the
MCT EV drive cycle. Tula also believes
that this technology could rapidly help
the market for electrically excitable synchronous
motors (EESM) grow versus
that for interior permanent magnet (IPM)
motors. " When you're dealing with a
system that is already 88% efficient, a
25% reduction is pretty significant, " said
Bailey. " By being able to take an EESM
and make it more efficient than an IPM
at a lower cost, that's where DMD becomes
important. We're offering up a
software solution that delivers considerable
value to the industry. "
On-road impressions
SAE Media drove a Chevrolet Bolt EV
outfitted with a prototype of Tula's DMD
The display screen
mounted in Tula's
Chevrolet Bolt
demo car noted
when the system
was in operation
(thick line at end
of the graph) and
when the motor
was operating
normally.
AUTOMOTIVE ENGINEERING
BOTH IMAGES: TULA
https://www.sae.org/news/2020/12/tula-dmd-aims-for-more-efficient-e-machines https://www.sae.org/news/2020/12/tula-dmd-aims-for-more-efficient-e-machines https://www.sae.org/news/2020/12/tula-dmd-aims-for-more-efficient-e-machines
Automotive Engineering - December 2022

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