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SWARM UAV
Magnetometer
Vibration
Analysis
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A SWARM UAV from
the Naval Surface
Warfare Center was
tested in a
laboratory setting
to understand and
propose solutions to
the problem of noisy
magnetometer
signals. Engine
runs, and shaker
based mechanical
impedance tests were
performed.
Significant signal
processing was
performed to analyze
the problem at hand.
The offending
mechanism of engine
vibration appearing
on the magnetometer
signal was
successfully
duplicated and fully
understood:
"The recommended
solution is simple
and cheap: implement
electronic
anti-aliasing
filters between the
magnetometer and the
data acquisition
board. A solution
consisting only of
Engine or
Magnetometer soft
mounts was also
considered, but the
back-of-the-envelope
calculation yielded
a design that would
result in 'floppy'
mounting and require
snubbing mechanisms.
If a mechanical-only
solution is desired,
additional mount
design and analysis
is required."
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Swarm UAV
Muffler Design
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In 2002, Sagetech
Corporation
conducted a short (SBIR
Phase I) study
focused on improving
engine efficiency
and reducing
acoustic exhaust
emissions on a 0.6
cu in model airplane
engine modified to
run on heavy fuel.
Although not the
primary focus of the
project, a
significant effort
was invested in the
carburetion and fuel
supply of the
engine. As a result,
impressive specific
fuel consumption was
extracted from this
engine even before
any exhaust
modifications were
made. The exhaust
system further
improved
performance. All
objectives were
surpassed in this
study:
-
Specific Power
Output was
increased by as
much as 20% over
the stock
exhaust.
-
Approximately
¾ hp was
generated at
9000 RPM
-
Specific
power output
was
increased
from 2.5 to
3.0
kW/(ml/s)
-
Specific fuel
consumption was
reduced from
0.47 to 0.39
lb/(hp hr).
-
Exhaust noise
was reduced by
20-40 dB as
compared to the
stock exhaust
-
At 12
inches,
exhaust
noise was
only a few
dB above the
ambient
noise floor.
-
At 3 feet,
exhaust
noise was
barely
measurable,
virtually at
the noise
floor.
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Dodge Viper
Active Noise
Cancellation
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 An
excellent example of
our system level
diagnostic skills
was our solution to
a problem Walker
Electronic
Silencing, Inc could
not solve. Their
active exhaust
system employed on
the Dodge Prowler
and Chevrolet
Corvette exhibited a
very rare, but
unacceptable “cough”
from the anti-noise
loudspeakers. After
18 months of
searching for the
cause, WES, Inc
called on Sagetech
Corporation. We
found the extremely
elusive problem
after a short two
week intensive
effort: the use of
>= rather than > in
a single line of
code which was
executed during less
than 0.00001% of
processor cycles.
We also uncovered
several
opportunities for
design optimization.
As a result of the
success, Walker
Electronic Silencing
signed Sagetech
Corporation to lead
future active
exhaust hardware
design efforts.
Unfortunately,
Tenneco Automotive,
Walker's parent
company, elected to
discontinue
development of a
production active
muffler.
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