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JAGUAR - Swept Sine Control
Swept Sine testing is done to determine
resonant frequencies and damping factors, overall peak G
response of the structure to stimulus, or simply to adhere to a
test requirement. Whatever your needs are, JAGUAR establishes
new levels of performance.
Testing large structures that possess closely spaced, highly
responsive resonant characteristics poses a severe challenge to
a digital control system.
The traditional approach is to attempt to sweep rapidly through
a resonance, in the hope that damage can be avoided. This makes
resonance definition very difficult. Traditional systems
typically lack adequate control dynamic range to allow
excitation of the resonance yet maintain control. The risk of
damage makes this undesirable.
JAGUAR solves these problems with a combination of purpose built
hardware, powerful DSP on each input and output channel, and a
long engineering appreciation for the intricacies of sine
testing. Some specifics of performance follow:
 | Output attenuator control performed in
steps as small as 0.05 dB. This fine amplitude control
provides a high degree of accuracy to protect critical test
articles, especially at the peak of resonance.
| Anti-imaging protection in the output
section such that out-of-band energy is attenuated 96 dB.
Prohibiting energy from being output to the shaker that was
not intended to be output prevents over/under- test
conditions.
| Phase matching between channels, without
resorting to software compensation, which is typically less
than 0.01 degree. A powerful feature of JAGUAR is its
ability to generate H(f) during the test and display them as
they build. This is a potent analysis tool that greatly aids
in pre-modal testing and resonance definition.
| Extremely powerful 32 bit floating point
DSP which equips each input channel with the world ’s only
patented digital tracking filter. True Tracking Filters
during analysis and/or control ensure that ONLY the response
energy desired is considered in measurement and control
strategies. High quality Tracking Filters also prove
invaluable in determining the peak G, Q, Phase and true
frequency of resonant and anti- resonant conditions.
Hardware specifications matter because software cannot
compensate for the failures of hardware. Without JAGUAR
’s 32 bit DSP for each channel pair, “tracking filtering
”would be performed using a sliding FFT process that
allows the frequency information to be extracted with
amplitude values from a small slice of time data. Because
FFTs force even spacing of spectral lines, there will be
averaging of energy for each spectral line of the FFT.
Causing the fundamental signal source to change its
frequency further compounds this undesirable attribute.
Digital smearing occurs, which amplifies the scale of the
error. The result is that the fundamental response is
“averaged ” across multiple FFT bins, causing extremely
poor peak definition and Q estimates. Peak definition is
valuable because it helps identify the resonant frequency.
The FFT approach greatly hampers sine control and
significantly reduces the accuracy of resonance
measurements.
JAGUAR ’s true Tracking Filters eliminate all of the
problems created by using an FFT based process. The
result is the ability to actually control through resonance
which yields a very accurate description of the resonance.
It also ensures that the test article is neither over-nor
under tested. Both conditions typically occur with FFT-based
“tracking filters. ”
Adaptive control greatly enhances the accuracy and speed
with which JAGUAR performs Sine and Random tests. JAGUAR
’s unique combination of low internal signal noise,
optimum data window choices and advanced processing power
permits a very large percentage of error correction per loop
while maintaining control stability. Within the Aerospace
community, JAGUAR is acknowledged as the premier Sine
Control system in the world. |
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