Acoustical defect detection system
First Claim
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1. A nonintrusive method of detecting internal defects in moving devices which have repetitive movements comprising:
- generating a sensor signal corresponding to the vibrations of said device during at least one cycle of movement;
analyzing said sensor signal in real time to produce a time signature related to device position that is the envelope of said signal, and to produce a set of frequency signatures related to device position that are the separate power spectra for fractions of a cycle; and
comparing said signatures with those of an acceptable device to identify abnormalities in vibration.
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Abstract
The vibration of a moving device which has repetitive movements, for instance a rotary compressor, are sensed at the outer case and analyzed in real time in both the time and frequency plane. For the time analysis the envelope of the signal is generated; for the frequency analysis a fast Fourier transform is performed and separate power spectra for fractions of a revolution are produced. The signatures are compared with those of an acceptable device to identify rejects and abnormalities at a particular position of a moving part.
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Citations
15 Claims
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1. A nonintrusive method of detecting internal defects in moving devices which have repetitive movements comprising:
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generating a sensor signal corresponding to the vibrations of said device during at least one cycle of movement; analyzing said sensor signal in real time to produce a time signature related to device position that is the envelope of said signal, and to produce a set of frequency signatures related to device position that are the separate power spectra for fractions of a cycle; and comparing said signatures with those of an acceptable device to identify abnormalities in vibration. - View Dependent Claims (2, 3)
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4. A nonintrusive method of detecting internal defects in rotary devices which have repetitive movements comprising:
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sensing the vibrations of said device during a designated number of revolutions and generating a sensor signal; conditioning said sensor signal to extract low frequency extraneous noise and high frequencies that could result in aliasing errors; generating a position reference in each revolution to synchronize averaging; producing a time signature which is the averaged envelope of said conditioned signal; producing a set of frequency signatures which are separately calculated and are the averaged power spectra of said conditioned signal for equal fractions of a revolution; and comparing said time and frequency signatures with reference data of an acceptable device and statistically derived limits of acceptability to identify abnormalities in vibration at a particular position of the rotating device. - View Dependent Claims (5, 6, 7, 8)
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9. An acoustical defect detecting system for inspecting moving devices which have repetitive movements comprising:
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a sensor which generates an electrical signal representative of the vibrations of said device; first means for producing a time signature which is related to device position and is the envelope of said signal during at least one cycle of movement of said device; second means for producing a set of frequency signatures that are related to device position and are each the power spectrum of said signal during a fraction of one cycle of movement; and means for comparing said signatures with those of an acceptable device to identify internal defects. - View Dependent Claims (10)
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11. An acoustical defect detecting system for inspecting rotary devices such as compressors which have repetitive movements comprising:
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a sensor which generates an electrical signal representative of the vibrations of said device; means for conditioning said signal to filter out low frequency noise and high frequencies that could result in aliasing errors; means for generating a position reference once per revolution to synchronize averaging; first analysis means for producing a time signature which is the averaged envelope of said conditioned signal over a designated number of revolutions; second analysis means for producing a set of frequency signatures that are the averaged and separately calculated power spectra of said conditioned signal during fractions of a revolution; and means for comparing said time and frequency signatures with statistically derived reference data of an acceptable device to identify internal defects at a particular position of said device. - View Dependent Claims (12, 13, 14, 15)
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Specification