Spectral Features Based on Fault Bands

Rotating machinery produces a spectrum that reflects the harmonics of the system. These harmonics result from the relationships among the rotating components, such as gear ratios and bearing ball size. When you know the physical characteristics of your bearing or gear mesh component, you can identify the characteristic frequencies of the component where failures can occur. Fault bands are frequency bands that bound these characteristic frequencies. Rather than compute spectral metrics across the entire frequency range, you can concentrate app analysis on frequencies within the fault bands, and extract more focused and effective features that indicate specific mechanical faults.

The app provides three types of fault band-based metrics.

Bearing Faults
Gear Mesh Faults
Custom Faults

Use Bearing Faults Features and Gear Mesh Faults Features when you know the physical parameters of your bearing or gear mesh component and want the app to compute fault bands from those parameters. Use Custom Faults Features to specify the fault bands directly. Selecting any of these options opens a tab for you to specify the parameters. When you use specify rotation or fundamental frequency using Constant (rpm) or Constant (Hz) respectively, the app overlays a preview of the fault bands on the spectral plot. If you change a parameter on the corresponding tab, the app updates the preview. In the Features section of the tab, you can select the features that you want.

The Bearing Faults Features and Gear Mesh Fault Features tabs contain similar specifications, as the following table shows.

Type

Rotation

Physical Parameters

Defect Types

Fault Band Settings

Features

Bearing Faults Features

Rotation in rpm

Bearing parameters

Number of balls
Ball and pitch diameters
Contact angle

Outer race
Inner race
Rolling element
Cage

Harmonics
Sidebands (inner race, ball)
Fault band width
Fault band folding
Number of generated features

Peak frequency
Band power
Peak amplitude
Total band power

Gear Mesh Faults Features

Gear mesh parameters

Number of input and output teeth

Input shaft
Output shaft
Assembly phase pass
Gear mesh

Harmonics
Sidebands (input gear, output gear)
Fault band width
Fault band folding
Number of generated features

The Custom Faults Features tab contains the specifications shown in the following table.

Type	Fundamental Frequency	Fault Band Settings	Advanced Settings	Features
Custom Faults Features	Fundamental frequency in Hz	Harmonics Sidebands Fault band width Sideband separation	Sideband separation type (additive or multiplicative) Fault band folding Number of generated features	Peak frequency Band power Peak amplitude Total band power

For more information about the parameters used for fault band metrics, see the Live Editor task description in Extract Spectral Features. For more information about the commands that the app uses, see