National Instruments Order Analysis Toolset - Manual (Page 30)

Chapter 2 Order Analysis
© National Instruments Corporation 2-15 LabVIEW Order Analysis Toolset User Manual
After the resampling process takes place, recovering a time waveform at a
specific order might be difficult.
Refer to Chapter 4, Resampling-Based Order Analysis , for information
about how the LabVIEW Order Analysis Toolset uses software-based
resampling for order analysis.
Adaptive Filter
Although the frequencies of the order components change as the rotational
speed changes, you can consider the rotational speed and the frequency of
order components to remain constant in a relatively short time interval.
The adaptive filter method of order analysis filters out the desired order by
using a bandpass filter whose passband frequency shifts according to the
rotational speed.
The Vold-Kalman Order Tracking Filter is an example of the successful
application of the adaptive filter method. With an accurate instantaneous
speed signal as a guide, the Vold-Kalman Order Tracking Filter can extract,
without ambiguity, two orders that are in close proximity to each other.