Main Content

Extract Spectral Features

Interactively extract spectral fault band metrics in the Live Editor

Description

The Extract Spectral Features task lets you interactively extract spectral fault band metrics. The task helps with analyzing and understanding spectral data. Using a comprehensive interface, you can add components to represent various bearings, gear meshes, or other parts of your hardware setup. As you set the physical parameters of these components, the Extract Spectral Features Live Editor task will plot fault frequency bands at the characteristic frequencies of the components. You can overlay power spectrum data on the fault band plot to associate various peaks in the data with the components' characteristic frequencies. This can make fault detection and fault isolation easier, as changes in the power spectrum data can easily be traced back to the physical components causing them. In addition to a plot of the characteristic frequencies and the power spectrum data, the task will generate spectral metrics of the data within each characteristic frequency band. The output metrics table containing the peak amplitude, peak frequency, and band power of each band aids in characterizing potential mechanical faults. The task automatically generates MATLAB® code for your live script. For more information about Live Editor tasks generally, see Add Interactive Tasks to a Live Script.

Extract Spectral Features task in Live Editor

Open the Task

To add the Extract Spectral Features task to a live script in the MATLAB Editor:

  • On the Live Editor tab, select Task > Extract Spectral Features.

  • In a code block in your script, type a relevant keyword, such as fault bands or metrics. Select Extract Spectral Features from the suggested command completions.

Parameters

Select power spectrum data

Select a vector of frequencies from the MATLAB workspace that correspond to your power spectrum data.

Select a vector containing the power spectrum magnitudes from the MATLAB workspace.

Configure components

Choose between adding a bearing, gear mesh or a custom component. You can name your component and then click the Add button. You can set the physical characteristics of these components using the parameters below. The Extract Spectral Features Live Editor task will plot fault frequency bands at the characteristic frequencies of the components.

Bearing Component Parameters

You can toggle this option to enable or disable the component from being included in the spectral metrics computation. Disabling the component will also remove its fault bands from the plot. Use the Delete button to permanently remove a component.

Specify the number of rolling elements in the bearing.

Pitch diameter of the bearing is the diameter of the circle that the center of the ball or roller travels during the bearing rotation.

Rotational speed of the shaft or inner race of the bearing. It is the fundamental frequency around which the Extract Spectral Features live task generates the fault frequency bands. The units must be consistent with the unit of the frequency vector.

Contact angle in degrees between a plane perpendicular to the ball or roller axis and the line joining the two raceways.

Diameter of the ball or roller in the bearing.

Specify the harmonics of the fundamental frequency to be included in the plot and in the spectral metrics computation.

Specify the sidebands around the fundamental frequency and its harmonics to be included in the plot and in the spectral metrics computation.

Specify the units of the fault band frequencies as either 'frequency' or 'order'. Select:

  • 'frequency' if you have the fault bands in the same units as the Rotational speed.

  • 'order' if you have the fault bands as number of rotations relative to the inner race rotation Rotational speed.

Specify the width of the frequency bands centered at the nominal fault frequencies as a positive scalar. Uncheck the Auto option to specify the width value manually.

Gear Mesh Component Parameters

You can toggle this option to enable or disable the component from being included in the spectral metrics computation. Disabling the component will also remove its fault bands from the plot. Use the Delete button to permanently remove a component.

Specify the number of teeth on the input gear as a positive integer.

Specify the number of teeth on the output gear as a positive integer.

Specify the rotational speed of the input gear as a positive scalar. It is the fundamental frequency around which the Extract Spectral Features live task generates the fault frequency bands. The units must be consistent with the unit of the frequency vector.

Specify the harmonics of the fundamental frequency to be included in the plot and in the spectral metrics computation.

Specify the sidebands around the fundamental frequency and its harmonics to be included in the plot and in the spectral metrics computation.

Specify the units of the fault band frequencies as either 'frequency' or 'order'. Select:

  • 'frequency' if you have the fault bands in the same units as the Rotational speed.

  • 'order' if you have the fault bands as number of rotations relative to the Rotational speed.

Specify the width of the frequency bands centered at the nominal fault frequencies as a positive scalar. Uncheck the Auto option to specify the width value manually.

Custom Component Parameters

You can toggle this option to enable or disable the component from being included in the spectral metrics computation. Disabling the component will also remove its fault bands from the plot. Use the Delete button to permanently remove a component.

Specify fundamental frequency of interest as a positive scalar. The Extract Spectral Features live task constructs the fault frequency bands around the fundamental frequency. For instance, to construct fault bands for a faulty induction motor, the mains frequency of 60 Hz is the fundamental frequency of interest. Similarly, to generate fault bands for a faulty gear train, the input shaft frequency is the fundamental frequency.

Specify the harmonics of the fundamental frequency to be included in the plot and in the spectral metrics computation.

Specify the sidebands around the fundamental frequency and its harmonics to be included in the plot and in the spectral metrics computation.

Specify the type of separation between successive sidebands as either 'additive' or 'multiplicative'. Select:

  • 'additive', to set the separation between successive sidebands to 0.1*F1 value, where F1 is the distance of the first sideband from the fundamental frequency.

  • 'multiplicative', to set the separation between successive sidebands proportional to both the harmonic order and the sideband value.

Specify the separation value between successive sidebands as a positive scalar. Uncheck the Auto option to specify the separation value manually.

Specify the width of the frequency bands centered at the nominal fault frequencies as a positive scalar. Uncheck the Auto option to specify the width value manually.

Toggle to specify whether negative nominal fault frequencies have to be folded about the frequency origin. If you turn Folding on, then the Extract Spectral Features live task folds the negative nominal fault frequencies about the frequency origin by taking their absolute values such that the folded fault bands always fall in the positive frequency intervals. The folded fault bands are computed as [max(0, |F|W2), |F|+W2], where W is the Band width and F is the Frequency.

Display results

Toggle this option enable or disable the display of spectral metrics. When the option is checked, then the Extract Spectral Features live task displays the metrics as a 1xN table, where N = 3*size((F+S),1)+1, that is three metrics per frequency range and the total band power over the frequency range.

The live task returns the following spectral metrics for each frequency range:

  • Peak Amplitude — Peak amplitude value for each specified frequency range.

  • Peak Frequency — Peak frequency value for each specified frequency range.

  • Band Power — Average power of each frequency range. For more information on band power, see bandpower.

  • Total Band Power — Sum of individual band powers for the set of specified frequency ranges.

Introduced in R2021a