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Frequency Domain Decomposition - FDD |
At a Glance
-
Method:
Frequency
Domain
Decomposition.
-
User
choices:
Peak
picking.
-
Frequency
resolution:
Defined by
number of
frequency
lines in
spectral
density
function.
-
Mode shape
estimation:
Immediate
animation.
-
Damping:
None.
-
Patent
protected.
Identifying
physical
parameters by
looking at the
decomposed
spectrum
In the frequency
domain approach
the
identification
is based on the
singular value
decomposition of
the spectral
density
matrix.The
singular values
are interpreted
as a combination
of auto spectral
densities for a
set of single
degree of
freedom (SDOF)
systems.The user
identifies the
physical
parameters by
visual
evaluation of
the plot
identifying the
SDOF spectral
density
bell-shaped
curve.
The SDOF
spectral density
bell-shaped
curves are
clearly seen for
the five picked
modes.
Accurate and
fast
identification
This technique
is denoted
Frequency Domain
Decomposition
(FDD) and is
known as the
most time
efficient and
accurate of the
frequency domain
techniques.
Identification
by simple
peak-picking
A fast way to
identify modal
parameters in a
minimum of time
is by using the
snap-facility to
select a peak on
one of the
identified SDOF
spectral density
bell-shaped
curve. The
program then
immediately
estimates the
mode shape for
each test setup,
assembles the
mode shape parts
from the
different test
setups, and
displays a 3D
display of the
resulting mode
shape.This plot
can be animated
in order to
visualize the
movement of the
mode shape.
Instant
animation of
peak picked
modes.
Download movie.
Deals with
close modes,
noise and
harmonics
The technique
deals
effectively with
closely spaced
modes and with
noise. It also
gives a clear
indication of
the presence of
harmonic
components in
the records due
to rotating
machinery
operating on the
structure when
the vibration
response was
measured.
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Technical
Details
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