Digital signal processing of encoder signals to detect resonances in rotating machines
First Claim
1. A method for analyzing the torsional and bending vibration of a rotary machine comprising the steps of:
- a) acquiring at least one raw signal representative of the instantaneous rotational velocity of at least one shaft of said rotary machine;
b) conditioning said raw signal to produce conditioned signals;
c) digitizing said conditioned signals at an initial rate greater than required by the Nyquist criterion to produce initial digital signals and forming initial digital records therefrom each comprised of a portion of said initial digital signal;
d) processing said initial digital signal records to produce an enhanced signal wherein selected torsional vibration components are enhanced and other signal components are reduced;
e) averaging said enhanced signals so to remove selected random signal components; and
f) analyzing said averaged enhanced signals to determine the torsional and bending vibration parameters of said rotary machine.
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Abstract
The present invention is a method and system for accurately analyzing shaft encoder signals from rotating machines. The invention reduces noise and other interferences in the encoder signals by novel means that yield an unprecedented power for extracting useful information. Signal distortion due to variation in the rotation rate of the machinery and due to FFT leakage are eliminated by acquiring digital values of the encoder signals at a set of discrete times that are determined by the properly averaged rotation rate of the shaft and requiring a fixed integer number of these discrete times per rotation of the shaft. Amplitude modulation is eliminated by proper spectral combination of left and right sidebands of the main encoder signal. Additive noise is removed by multiplying sidebands and averaging the results over a number of data records.
62 Citations
19 Claims
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1. A method for analyzing the torsional and bending vibration of a rotary machine comprising the steps of:
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a) acquiring at least one raw signal representative of the instantaneous rotational velocity of at least one shaft of said rotary machine; b) conditioning said raw signal to produce conditioned signals; c) digitizing said conditioned signals at an initial rate greater than required by the Nyquist criterion to produce initial digital signals and forming initial digital records therefrom each comprised of a portion of said initial digital signal; d) processing said initial digital signal records to produce an enhanced signal wherein selected torsional vibration components are enhanced and other signal components are reduced; e) averaging said enhanced signals so to remove selected random signal components; and f) analyzing said averaged enhanced signals to determine the torsional and bending vibration parameters of said rotary machine. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification