Vibration analysis
First Claim
1. A method for measuring vibration in a machine including a member under periodic motion, said method comprising the steps of:
- (a) selecting specific vibration harmonic components to be measured;
(b) generating by first sensor means a first signal that repeats every period of said motion to provide a reference to a known position on the member, a frequency domain transform of said first signal having known harmonic component phase angles relative to said known position for all said selected harmonic components;
(c) generating by second sensor means a second signal which varies in the time domain with respect to a vibration characteristic of the machine;
(d) transforming the second signal into a frequency domain to derive a plurality of third (reconstruction magnitude) signals each indicative of the magnitude of one of the selected harmonic components of the transformed second signal, and synchronously transforming the first signal into the frequency domain to derive a fourth signal for each selected harmonic, each fourth signal being indicative of the phase angle difference between corresponding harmonic components of the transformed second signal and the transformed first signal; and
(e) storing said third signals and said fourth signals.
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Abstract
The present invention provides a method for measuring vibration in a machine including a member under periodic motion. To measure vibration in a rotating shaft (11) a first signal comprising a series of impulses, one impulse occurring each shaft revolution, is generated by a proximity probe (20) and a modulator/demodulator (22). The first signal is transmitted to channel A of a FFT spectrum analyzer (19) and a second signal, which varies in time with respect to displacement of the shaft (11), is produced by a proximity probe (14) and a modulator/demodulator (18) and fed to channel B of the FFT analyzer (19). The second signal is fourier transformed by analyzer (19) into the frequency domain to obtain reconstruction magnitude signals each indicative of the magnitude of one of the first twelve harmonics of the transformed second signal. The first signal is fourier transformed by the analyzer (19) synchronously with the second signal to obtain the phase angle differences between the respective harmonic components of each signal for the first twelve components. The mark to space ratio of the first signal is chosen to be less than one-twelfth so that the phase angles of the first twelve harmonic components of the fourier transformed first signal are known to be zero.
26 Citations
16 Claims
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1. A method for measuring vibration in a machine including a member under periodic motion, said method comprising the steps of:
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(a) selecting specific vibration harmonic components to be measured; (b) generating by first sensor means a first signal that repeats every period of said motion to provide a reference to a known position on the member, a frequency domain transform of said first signal having known harmonic component phase angles relative to said known position for all said selected harmonic components; (c) generating by second sensor means a second signal which varies in the time domain with respect to a vibration characteristic of the machine; (d) transforming the second signal into a frequency domain to derive a plurality of third (reconstruction magnitude) signals each indicative of the magnitude of one of the selected harmonic components of the transformed second signal, and synchronously transforming the first signal into the frequency domain to derive a fourth signal for each selected harmonic, each fourth signal being indicative of the phase angle difference between corresponding harmonic components of the transformed second signal and the transformed first signal; and (e) storing said third signals and said fourth signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification