Engee documentation

orderspectrum

The average spectrum depends on the order of the vibration signal.

Library

EngeeDSP

Syntax

Function call

  • spec,order = orderspectrum(x,fs,rpm) — calculates the vector of the average spectrum spec order and amplitude for the input signal x, sampled with frequency fs, and also returns a vector of orders order corresponding to each average value of the spectrum. To calculate the spectrum, the function orderspectrum uses a flat-topped window for the signal x with a constant phase resulting from oversampling.

  • spec,order = orderspectrum(map,order) — calculates the vector of the average spectrum of order and amplitude based on the map of the order and frequency of rotation map and the input vector of orders order. Use the function rpmordermap to calculate map and order. Argument map must be scaled linearly. The returned amplitudes are the same as the amplitudes in map. The returned spectrum scales linearly.

  • spec,order = orderspectrum(map,order,Name,Value) — sets the type of amplitude using an additional type argument «name-value», value Amplitude It should be taken into account when calculating the average order and amplitude spectrum based on the rotation order and frequency map.

  • orderspectrum(___,out=:plot) — plots a linearly scaled RMS amplitude of a spectrum of orders.

Arguments

Input arguments

# x — input signal

+ vector

Details

The input signal is specified as a row vector or column vector.

# fs — sampling rate
scalar

Details

The sampling rate, set as a positive scalar, expressed in Hz.

# rpm — rotation speed

+ vector

Details

The rotation speed, set as a vector of positive values expressed in rpm. Length of the argument rpm must match the length of the argument. x.

  • If there is a pulse signal of the tachometer, use the function tachorpm for direct extraction rpm.

  • If there is no pulse signal of the tachometer, use the function rpmtrack to extract rpm from the vibration signal.

# map — a map of the order and speed of rotation

+ vector

Details

A map of the rotation order and frequency, defined as a matrix. Use the function rpmordermap to calculate rotation order and frequency maps.

# order — orders in the syntax of the rotation order and frequency map

+ vector

Details

The orders in the syntax of the rotation order and frequency map, specified as a vector. Vector length order must be equal to the number of lines in the map map.

Input arguments «name-value»

Specify optional argument pairs as Name,Value, where Name — the name of the argument, and Value — the appropriate value. Type arguments «name-value» they should be placed after the other arguments, but the order of the pairs does not matter. You can specify multiple pairs «name-value».

Use commas to separate the name and value, and Name put it in quotation marks.

# Amplitude — type of amplitude

+ "rms" (by default) | "peak" | "power"

Details

The type of amplitude of the rotation order and frequency map, set by one of the following values:

  • "rms" — returns the RMS amplitude for each estimated order;

  • "peak" — returns the peak amplitude for each estimated order;

  • "power" — returns the power level for each estimated order.

# out — type of output data

+ :data (by default) | :plot

Details

Type of output data:

  • :data — the function returns data;

  • :plot — the function returns a graph.

For this argument, the name and value are separated by an equal sign (=).

Output arguments

# spec — average order and amplitude spectrum

+ vector

Details

The average spectrum of order and amplitude, returned as a vector of RMS amplitudes on a linear scale. If you use map and order as input arguments , and set for the argument Amplitude meaning "power" when using the function rpmordermap to calculate map, then the function orderspectrum returns spec in units of power.

# order — output orders

+ vector

Details

The output orders returned as a vector of real numbers.

Literature

  1. Brandt, Anders. Noise and Vibration Analysis: Signal Analysis and Experimental Procedures. Chichester, UK: John Wiley & Sons, 2011.

  2. Vold, Håvard, and Jan Leuridan. «High Resolution Order Tracking at Extreme Slew Rates Using Kalman Tracking Filters.» Shock and Vibration. Vol. 2, 1995, pp. 507–515.