National Instruments Order Analysis Toolset User Manual
TM
LabVIEW
Order Analysis Toolset
User Manual
LabVIEW Order Analysis Toolset User Manual
August 2003 Edition
Part Number 322879B-01
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Contents
About This Manual
How to Use This Manual ...............................................................................................vii
Conventions ...................................................................................................................vii
Related Documentation..................................................................................................viii
Chapter 1
Introduction to the LabVIEW Order Analysis Toolset
Overview of the LabVIEW Order Analysis Toolset......................................................1-1
Overview of the LabVIEW Order Analysis Start-Up Kit..............................................1-1
Important Considerations for the Analysis of Rotating Machinery...............................1-2
System Requirements ....................................................................................................1-3
Installation .....................................................................................................................1-3
Example VIs ..................................................................................................................1-4
Acquiring Data for Example VIs.....................................................................1-4
Configuring DAQ Hardware Used with Examples .........................................1-4
Acquire Data (Analog Tach) VI........................................................1-5
Acquire Data with PXI 4472 and TIO VI .........................................1-6
Chapter 2
Order Analysis
Order Analysis Definition and Application ...................................................................2-1
Order Analysis Basics....................................................................................................2-1
Effect of Rotational Speed on Order Identification .......................................................2-4
Constant Rotational Speed ..............................................................................2-4
Variable Rotational Speed...............................................................................2-6
Harmonic Analysis ..........................................................................................2-9
Order Analysis.................................................................................................2-9
Order Analysis Methods ................................................................................................2-9
Gabor Transform .............................................................................................2-10
Resampling ......................................................................................................2-13
Adaptive Filter.................................................................................................2-15
© National Instruments Corporation v LabVIEW Order Analysis Toolset User Manual
Contents
Chapter 3
Gabor Transform-Based Order Tracking
Overview of Gabor Order Analysis............................................................................... 3-1
Extracting the Order Components ................................................................................. 3-3
Masking .........................................................................................................................3-5
Extracting Orders ............................................................................................ 3-6
Reconstructing the Signal ............................................................................... 3-7
Displaying Spectral Maps.............................................................................................. 3-8
Calculating Waveform Magnitude ................................................................................ 3-10
Chapter 4
Resampling-Based Order Analysis
LabVIEW Order Analysis Toolset Resampling Method............................................... 4-1
Determining the Time Instance for Resampling ........................................................... 4-2
Resampling Vibration Data ........................................................................................... 4-4
Slow Roll Compensation............................................................................................... 4-5
Chapter 5
Calculating Rotational Speed
Digital Differentiator Method........................................................................................ 5-1
Averaging Pulses ........................................................................................................... 5-3
Appendix A
Gabor Expansion and Gabor Transform
Appendix B
References
Appendix C
Technical Support and Professional Services
Glossary
Index
LabVIEW Order Analysis Toolset User Manual vi ni.com
About This Manual
This manual provides information about the LabVIEW Order Analysis
Toolset, including system requirements, installation, and suggestions
for getting started with order analysis and the toolset. The manual also
provides a brief discussion of the order analysis process and the algorithm
used by the LabVIEW Order Analysis Toolset.
How to Use This Manual
If you are just beginning to gain experience with order analysis, read
Chapter 2, Order Analysis, of this manual and experiment with the
Order Analysis Start-Up Kit. Refer to Chapter 1, Introduction to the
LabVIEW Order Analysis Toolset, for information about the Order
Analysis Start-Up Kit.
If you have experience with order analysis, use the example VIs to
learn about how to use the LabVIEW Order Analysis Toolset. Refer
to Chapter 1, Introduction to the LabVIEW Order Analysis Toolset,
for information about the example VIs.
If you want to learn more about the algorithm used in the LabVIEW
Order Analysis Toolset, refer to Chapter 3, Gabor Transform-Based Order
Tracking, and Chapter 4, Resampling-Based Order Analysis.
For information about individual VIs, refer to the Order Analysis Toolset
Help, available in LabVIEW 6.1 by selecting Help»Order Analysis.
In LabVIEW 7.0 and later, Order Analysis Toolset Help is part of the
LabVIEW Help, which is available by selecting Help»VI, Function,
& How-To Help.
Conventions
The following conventions appear in this manual:
» The » symbol leads you through nested menu items and dialog box options
to a final action. The sequence File»Page Setup»Options directs you to
pull down the File menu, select the Page Setup item, and select Options
from the last dialog box.
This icon denotes a note, which alerts you to important information.
© National Instruments Corporation vii LabVIEW Order Analysis Toolset User Manual
About This Manual
bold Bold text denotes items that you must select or click in the software, such
as menu items and dialog box options. Bold text also denotes the names of
parameters, dialog boxes, sections of dialog boxes, windows, menus,
palettes, and front panel controls and buttons.
italic Italic text denotes variables or cross references.
monospace Text in this font denotes text or characters that you should enter from the
keyboard, sections of code, programming examples, and syntax examples.
This font is also used for the proper names of disk drives, paths, directories,
programs, subprograms, subroutines, device names, functions, operations,
variables, filenames and extensions, and code excerpts.
Platform Text in this font denotes a specific platform and indicates that the text
following it applies only to that platform.
Related Documentation
The following documents contain information that you might find helpful
as you read this manual:
• LabVIEW Order Analysis Toolset Help
• Getting Started with LabVIEW
• LabVIEW User Manual
• LabVIEW Help
LabVIEW Order Analysis Toolset User Manual viii ni.com
Introduction to the
LabVIEW Order Analysis Toolset
This chapter introduces the LabVIEW Order Analysis Toolset and the
Order Analysis Start-Up Kit, outlines system requirements, and gives
installation instructions.
Overview of the LabVIEW Order Analysis Toolset
The LabVIEW Order Analysis Toolset is a collection of virtual instruments
(VIs) for LabVIEW. These VIs help you measure and analyze noise or
vibration signals generated by rotating machinery by enabling you to
perform the following analysis operations:
• Calculation and examination of rotational speed
• Measurement of the power distribution in the frequency domain or
in the order domain as a function of either time or rotational speed
• Extraction of the order components from the original noise or vibration
signal
• Measurement of the magnitude and phase of any order component as
a function of rotational speed
• Presentation of data in a waterfall, orbit, or polar plot
1
The LabVIEW Order Analysis Toolset includes easy and advanced VIs.
Use the easy VIs to perform simple tasks in just a few steps. The advanced
VIs provide flexibility and increased control of the analysis process. Refer
to the LabVIEW Order Analysis Toolset Help for information about
individual VIs.
Overview of the LabVIEW Order Analysis Start-Up Kit
The Order Analysis Start-Up Kit is automatically installed when you install
the LabVIEW Order Analysis Toolset. To open the Order Analysis
Start-Up Kit, select Start»Programs»National Instruments»Order
Analysis»Order Analysis Start-Up. The Order Analysis Start-Up Kit
includes a LabVIEW application for order analysis. The order analysis
© National Instruments Corporation 1-1 LabVIEW Order Analysis Toolset User Manual
Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
application is built with components found in the LabVIEW Order
Analysis Toolset.
The order analysis application provides an example of how the LabVIEW
Order Analysis Toolset can help you successfully complete analysis
projects. The simple processes included in the order analysis application
enable you to perform data acquisition, tachometer analysis, tachless speed
profile generation, order analysis, and online monitoring of noise or
vibration signals generated by rotating machinery. You also can use the
order analysis application as a simple order analysis VI in projects or as
a tool to learn the basics of building and using LabVIEW Order Analysis
Tools e t VI s.
Important Considerations for the Analysis of Rotating Machinery
Order analysis is a powerful tool for analyzing rotating machinery when the
rotational speed might change over time. However, to successfully use the
LabVIEW Order Analysis Toolset, you must observe the following
condition and restriction:
• Provide a signal directly related to the position of the shaft, such as a
pulse train from a tachometer or key phasor. Although the LabVIEW
Order Analysis Toolset can measure the magnitude of the order
components without a tachometer signal, the measurement of the
phase of the order components requires a tachometer signal.
• Do not use the LabVIEW Order Analysis Toolset for analysis of
frequencies that are not excited by a fundamental frequency, such as
the modes encountered in modal analysis. Although you can observe
the different modes in the frequency domain, no simple relationship
exists among those different modes. Usually, the frequencies of
different modes are not simply a multiple of a fundamental frequency
over time.
LabVIEW Order Analysis Toolset User Manual 1-2 ni.com
System Requirements
You must have LabVIEW 6.1 or later Full Development System or
Professional Development System installed to run the LabVIEW Order
Analysis Toolset.
Note Refer to the LabVIEW Release Notes for the required system configuration for
LabVIEW.
Note Order analysis is a memory-intensive task, especially when you display spectral
maps. Increasing the amount of RAM in your system can significantly increase system
performance.
Installation
This section provides instructions for installing the LabVIEW Order
Analysis Toolset.
Note Some virus detection programs interfere with the installer. Disable any automatic
virus detection programs before you install. After installation, check your hard disk for
viruses and enable any virus detection programs you disabled.
Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
(Windows 2000/NT/XP) Complete the following steps to install the LabVIEW
Order Analysis Toolset.
1. Log on as an administrator or as a user with administrator privileges.
2. Insert the LabVIEW Order Analysis Toolset 2.0 installation CD into
the CD-ROM drive and follow the instructions that appear on the
screen. If the startup screen does not appear, select Start»Run,
navigate to the
Toolset 2.0 installation CD, and double-click
(Windows Me/98) Insert the LabVIEW Order Analysis Toolset 2.0
installation CD and follow the instructions that appear on the screen. If the
startup screen does not appear, select Start»Run, navigate to the
folder on the LabVIEW Order Analysis Toolset 2.0 installation CD, and
double-click
© National Instruments Corporation 1-3 LabVIEW Order Analysis Toolset User Manual
Setup folder on the LabVIEW Order Analysis
OAT.exe.
Setup
OAT.exe.
Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
Example VIs
If you have experience with order analysis, the example VIs, located in
the
examples\Order Analysis directory, can help you learn how to use
the LabVIEW Order Analysis Toolset. The example VIs illustrate the
following LabVIEW Order Analysis Toolset functions for both analog
and digital tachometer signal processing:
• Acquiring data
• Presenting data
• Gabor order tracking
• Resample order tracking
The example VIs use VIs found on the LabVIEW Order Analysis Toolset
palettes and illustrate the basic capabilities of the LabVIEW Order
Analysis Toolset.
Acquiring Data for Example VIs
For most of the example VIs, you can use prerecorded data or data you
acquire with data acquisition (DAQ) hardware. The example VIs that
accept either prerecorded data or acquired data have a Boolean control
named Data Source. The Data Source control has two choices, Example
and DAQ. When you choose Example, the VI uses prerecorded data
generated during a fan run-up as the data source. When you choose DAQ,
the VI uses data you acquire with DAQ hardware.
When acquiring data through DAQ hardware, National Instruments
recommends you follow the following guidelines:
• Use an anti-aliasing filter before data acquisition to avoid the
frequency alias.
• Sample the data from different channels simultaneously to maintain
the phase relationship between channels, such as a tachometer signal
and a vibration signal.
Configuring DAQ Hardware Used with Examples
The example VIs that accept both prerecorded data and acquired data use
either an analog tachometer signal or a digital tachometer signal. The front
panel of the example VI specifies the type of tachometer signal the VI uses,
for example, Gabor Order Tracking (Analog Tach) or Gabor Order
Tracking (Digital Tach). Depending on whether the example is an analog
tachometer example or a digital tachometer example, when Data Source is
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Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
set to DAQ and you click the Run button on the front panel of the
example VI, one of the following VIs opens:
• Acquire Data (Analog Tach) VI
• Acquire Data with PXI 4472 and TIO VI
Refer to the Acquire Data (Analog Tach) VI section for information about
the Acquire Data (Analog Tach) VI and the Acquire Data with PXI 4472
and TIO VI section for information about the Acquire Data with PXI 4472
and TIO VI.
Acquire Data (Analog Tach) VI
In analog tachometer examples, setting Data Source to DAQ and clicking
the Run button opens the Acquire Data (Analog Tach) VI. The Acquire
Data (Analog Tach) VI helps you acquire vibration data with a digital
tachometer signal. Figure 1-1 shows the Configuration tab of the Acquire
Data (Analog Tach) VI.
Figure 1-1. Acquire Data (Analog Tach) VI Configuration Tab
You must configure two channels of the DAQ device before you acquire
data. Use the Configuration tab of the Acquire Data (Analog Tach) VI,
shown in Figure 1-1, to configure your DAQ device. In the Channel
Settings section of the Configuration tab, use Tachometer for the
© National Instruments Corporation 1-5 LabVIEW Order Analysis Toolset User Manual
Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
tachometer signal and S&V for the sound or vibration sensor. After
choosing data acquisition settings, enter the number of pulses you want the
tachometer to generate per revolution in the Tach Pulse/Rev text box.
Use the controls in the Channel Info section of the Configuration tab to
specify the channel information for the sound or vibration sensor.
After configuring the DAQ device, click the Acquisition tab, shown in
Figure 1-2.
Figure 1-2. Acquire Data (Analog Tach) VI Acquisition Tab
The Acquisition tab, shown in Figure 1-2, allows you to acquire and
observe data. Click the Acquire button to acquire data. Continue to
configure the data acquisition and acquire data until you acquire the data
you want. Click the OK button to return to the front panel of the example
VI to analyze the data.
Acquire Data with PXI 4472 and TIO VI
In digital tachometer examples, setting Data Source to DAQ and clicking
the Run button opens the Acquire Data with PXI 4472 and TIO VI. The
Acquire Data with PXI 4472 and TIO VI helps you acquire vibration data
with a digital tachometer signal. Figure 1-3 shows the Configuration tab
of the Acquire Data with PXI 4472 and TIO VI.
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Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
Figure 1-3. Acquire Data with PXI 4472 and TIO VI Configuration Tab
Use the Configuration tab of the Acquire Data with PXI 4472 and TIO VI,
shown in Figure 1-3, to configure the DAQ devices. Use one of the
counters on a TIO device to receive TTL-compatible tachometer pulses.
Use the controls in the TIO Board Setting (Digital Tach Signal) section
of the Configuration tab to configure the TIO device. Use an NI PXI-4472
to acquire the data from the sound or vibration sensor. Use the controls in
the DSA Board Setting (S/V Signal) and Input Settings sections of the
Configure tab to configure the NI PXI-4472. After configuring the DAQ
devices, click the Acquisition tab, shown in Figure 1-4.
© National Instruments Corporation 1-7 LabVIEW Order Analysis Toolset User Manual
Chapter 1 Introduction to the LabVIEW Order Analysis Toolset
Figure 1-4. Acquire Data with PXI 4472 and TIO VI Acquisition Tab
The Acquisition tab, shown in Figure 1-4, allows you to acquire and
observe data. Click the Acquire button to acquire data. Continue to
configure the data acquisition and acquire data until you acquire the
data you want. Click the OK button to return to the front panel of the
example VI to analyze the data.
LabVIEW Order Analysis Toolset User Manual 1-8 ni.com
Order Analysis
This chapter gives brief descriptions of the need for order analysis, the
basic concepts of order analysis, the effect of rotational speed on order
identification, and the different order analysis methods.
Order Analysis Definition and Application
When it is impossible or undesirable to physically open up a system and
study it, you often can gain knowledge about the system by measuring and
analyzing signals associated with the system. For example, physicists and
chemists use the spectrum generated by a prism to distinguish between
different types of matter. Astronomers apply spectra, as well as the Doppler
effect, to determine distances between planets. Physicians use the
electrocardiograph (ECG), which traces the electrical activity of the heart,
as a nonsurgical means of diagnosing heart problems.
You can use order analysis to study, design, and monitor rotating
machinery. By measuring and analyzing sound or vibration signals
generated by a system with rotational components, you can gain a better
understanding of the system, associate features of noise and vibration
with the physical characteristics of the system, and identify system
characteristics that change with time and operating conditions.
Systems with rotational components include automobiles, airplanes,
air conditioners, and PC hard drives.
2
Order Analysis Basics
Order analysis and harmonic analysis have much in common. The term
harmonic refers to frequencies that are integer or fractional multiples of
a fundamental frequency.
When dealing with rotating machinery, you often can hear noise and feel
vibration created by the parts associated with the rotating components.
Parts associated with rotating components include bearings, gears, and
blades. Vibration of the rotating components creates noise and vibration
signals. The machine rotational speed is the source of the noise and
© National Instruments Corporation 2-1 LabVIEW Order Analysis Toolset User Manual
Chapter 2 Order Analysis
vibration signals. The frequency-domain representations of noise and
vibration behave as harmonics of the machine rotational speed.
In many industries, the harmonics related to the rotational speed are
referred to as orders. The corresponding harmonic analysis is called order
analysis. The harmonic at the same frequency as that of the rotational speed
is the first
order; the harmonic at twice the frequency of the rotational speed
is the second order and so on. Therefore, you can think of order analysis as
an application of harmonic analysis for rotating machinery.
Figure 2-1 shows the relationship between frequency and order spectra.
1.7E+4
0.0E+0
VibrationTachometer
–1.9E+4
–2.5E+4
3.0E+6
2.0E+6
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Time (s)
1.1E+3
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Time (s)
Spectrum
Frequency
3.3E–2
0.0 100.0 200.0 300.0 400.0 500.0
Frequency (Hz)
3.0E+6
2.0E+6
Order
Spectrum
3.3E–2
0.0 2.0 4.0 6.0 8.0 10.0
Order
Figure 2-1. Order and Frequency Domain Display of a Shaft Rotating at 3,000 rpm
The top graph in Figure 2-1 shows a vibration signal from a machine
running at 3,000 revolutions per minute (rpm). The rotational speed is
computed from the tachometer signal, which is shown as the second graph
in Figure 2-1. The frequency domain and order domain plots of the signal
are shown in the third and fourth graphs, respectively, in Figure 2-1.
LabVIEW Order Analysis Toolset User Manual 2-2 ni.com
Chapter 2 Order Analysis
Assuming that speed remains constant during data acquisition, you can use
the following equations to switch between the frequency domain and the
order domain.
RPM
Frequency
Order Frequency
-------------
60
Order×=
×=
60
-------------
RPM
Orders often reflect the physical characteristics of rotating machines. As in
classical harmonic analysis, by analyzing the phase and amplitude
relationships between different orders, you often can discover a great deal
about the system in which you are interested. For example, order analysis
has enabled the observation of the following relationships:
• Imbalance results in a spectral peak at the first order.
• Misalignment or bending of the shaft generates a large second order.
• Oil whirl might lead to strong fractional orders.
• Gears, belts, and blades might enhance high orders.
Figure 2-2 shows the order spectrum of the vibration signal measured from
a PC fan with seven blades and four coils.
4 Coils 7 Blades
0.0 2.0 4.0 6.0 8.0 10.0
Orders
Figure 2-2. Order Spectrum of a PC Fan with Seven Blades and Four Coils
12.0 14.0 16.0
The vibration signal depicted in Figure 2-2 contains strong fourth and
seventh orders. The four coils inside the fan drag and push the shaft
four times per revolution, causing the strong fourth order. The seven blades
of the fan pass the position of the sensor seven times per revolution and
cause the strong seventh order.
© National Instruments Corporation 2-3 LabVIEW Order Analysis Toolset User Manual
Chapter 2 Order Analysis
Like classical harmonic analysis, order analysis is a powerful tool for
gaining a better understanding of the condition of rotating machinery.
However, compared to harmonic analysis, order analysis is more effective
for the analysis of rotating machinery because you can use order analysis
when a machine runs at a constant speed and when the rotational speed
varies. As described in the Effect of Rotational Speed on Order
Identification section, harmonic analysis is effective only when the
rotational speed remains constant.
Effect of Rotational Speed on Order Identification
The ability to make a reliable identification of individual orders from the
conventional power spectrum depends on whether rotational speed remains
constant or varies. This section discusses the effect rotational speed has on
the conventional power spectrum and discusses classical harmonic analysis
and order analysis in relation to rotational speed.
Constant Rotational Speed
At a constant rotational speed, you can identify orders from both the
conventional power spectrum and the frequency-time spectral map.
Figure 2-3 illustrates the analysis of a vibration signal acquired from
a PC fan running at a constant speed.
LabVIEW Order Analysis Toolset User Manual 2-4 ni.com
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