Signal processing

Signal processing algorithms

pyvib.signal.autocorrelation(y, normalize=False)

Get auto-correlation of the signal

Parameters

yfloat 1D array

Signal

normalizeboolean, optional

Whether signal should be normalized

Returns

acfloat 1D array

Autocorrelated signal

pyvib.signal.downsample(s, n, phase=0)

Direct downsampling of a signal

Parameters

• s (1D array) – Signal to downsample

• n (int) – Downsampling factor

• phase (int) – Phase lag before sampling

Returns

s_out – Downsampled signal

Return type

1D array

pyvib.signal.encoder2position(t, enc, thr)

Converts from encoder pulses to position signal

Parameters

• t (float 1D array) – Time vector

• enc (float 1D array) – Measured analog signal

• thr (float) – Threshold for pulses going up or down

Returns

• t_s (float 1D array) – Position time vector

• s (float 1D array) – Position vector

• n (int) – Number of pulses encountered

pyvib.signal.envelope(y, absolute=True)

Get envelope of signal.

Parameters

• y (float 1D array) – Signal to get envelope of

• absolute (boolean, optional) –

  Whether the absolute value (envelope is returned):

  • True for envelope

  • False for analytic signal

Returns

env – Enveloped or analytic signal

Return type

float 1D array

See also

fftwhilbert

function A faster way of calculating the analytic signal

pyvib.signal.fftwconvolve(in1, in2, mode='full')

Convolve two N-dimensional arrays using PYFFTW. This is a modified version of scipy.signal.fftwconvolve

Convolve in1 and in2 using the fast Fourier transform method, with the output size determined by the mode argument.

Parameters

• in1 (float 1D array) – First input.

• in2 (float 1D array) – Second input. Should have the same number of dimensions as in1. If operating in ‘valid’ mode, either in1 or in2 must be at least as large as the other in every dimension.

• mode (str {'full', 'valid', 'same'}, optional) –

  A string indicating the size of the output:

  full

  The output is the full discrete linear convolution of the inputs. (Default)

  valid

  The output consists only of those elements that do not rely on the zero-padding.

  same

  The output is the same size as in1, centered with respect to the ‘full’ output.

Returns

out – An N-dimensional array containing a subset of the discrete linear convolution of in1 with in2.

Return type

float 1D array

pyvib.signal.generalized_synchronous_average(t, vib, t_s, s, R, ds=None)

Estimate the synchronous average of a signal that actually varies in speed

Based on Abboud, D., Antoni, J., Sieg-Zieba, S., & Eltabach, M. (2016). Deterministic-random separation in nonstationary regime. Journal of Sound and Vibration, 362, 305-326.

Parameters

tfloat 1D array

Time of signal

yfloat

Signal

t_sfloat 1D array

Time of shaft position

sfloat

Shaft position

Rint

Number of regimes

dsfloat, optional

Force a certain delta position if wanted

Returns

gsafloat 1D array

Synchronous signal which can be removed

s_otfloat 1D array

Order tracked position

vib_otfloat 1D array

Order tracked signal

pyvib.signal.ordertrack(t, y, t_s, s, ds, cubic=True)

Order track the vibration signal to match a desired position vector

Parameters

tfloat 1D array

Time signal

yfloat 1D array

Signal to order track

t_sfloat 1D array

Time of position signal

sfloat 1D array

Position signal in number of rounds

dsfloat

Desired delta position

cubicboolean, optional

Whether cubic interpolation is used

Returns

s_otfloat 1D array

Shaft position of returned signal

y_otfloat 1D array

Order tracked signal

pyvib.signal.teager(vib)

Compute the teager energy operator

Parameters

x (1D array) – Input signal

Returns

x_teager – Teager energy operator

Return type

float 1D array

pyvib.signal.tsakeep(y, Fs, X, debug=False)

Duplicates the synchronous signal to the original length

Parameters

yfloat 1D array

Signal

Fsfloat

Sampling rate in Hz

Xfloat

Synchronous speed in Hz

Returns

y_syncfloat 1D array

Synchronous signal

pyvib.signal.tsaremove(y, Fs, X, debug=False)

Subtracts the synchronous average of a signal

Parameters

yfloat 1D array

Signal

Fsfloat

Sampling rate in Hz

Xfloat

Synchronous speed in Hz

Returns

y_nonsyncfloat 1D array

Non-synchronous signal