National Instruments Order Analysis Toolset - Manual (Page 33)

Chapter 3 Gabor Transform-Based Order Tracking
© National Instruments Corporation 3-3 LabVIEW Order Analysis Toolset User Manual
Complete the following steps to perform Gabor order analysis.
1. Acquire data samples from the tachometer and noise or vibration
sensors synchronously at some constant sample rate.
2. Use the LabVIEW Order Analysis Toolset VIs to complete the
following steps.
a. Perform a Gabor transform on the noise or vibration samples to
produce an initial Gabor coefficient array.
b. Calculate the rotational speed from the tachometer signal. Refer to
Chapter 5,
Calculating Rotational Speed , for information about
calculating rotational speed.
c. Generate a 2D spectral map from the initial coefficient array to
observe the whole signal over frequency-time, frequency-rpm,
order-rpm, or rpm-order.
d. Generate a modified coefficient array, based on the rotational
speed and the order of interest, from the initial array by
performing a masking operation.
e. Generate a time domain signal from the modified coefficient array
by performing Gabor expansion.
f. Calculate the waveform magnitude and phase.
Refer to the Important Considerations for the Analysis of Rotating
Machinery section of Chapter 1, Introduction to the LabVIEW Order
Analysis Toolset , for information about a condition and restriction for using
the LabVIEW Order Analysis Toolset to analyze rotating machinery.
Extracting the Order Components
After generating the initial Gabor coefficient array through a Gabor
transform, you can select one or more order components for analysis. You
can convert the coefficient corresponding to the selected order component
back into a time domain signal. The resulting time domain signal contains
information only about the selected order component.
You select order components by including the coefficients along the
corresponding order curves. Therefore, you must determine the position
index of the coefficient on each order curve. Because the frequency of an
order component is an integer or fractional multiple of the fundamental
frequency, such as the rotational speed, the position index of a given order
curve at each time interval is calculated by multiplying the order number
and the fundamental frequency index at the time interval. If a signal is