Boots – shoes – and leggings
Patent
1991-03-11
1994-05-03
Teska, Kevin J.
Boots, shoes, and leggings
36442406, 36455101, 364151, G06F 1560
Patent
active
053093798
DESCRIPTION:
BRIEF SUMMARY
This invention relates to monitoring.
BACKGROUND OF THE INVENTION
The invention is more particularly concerned with methods and apparatus for monitoring the condition of assemblies such as a gas-turbine engine in an aircraft.
It is known to monitor the vibration produced by engines and bearings and to detect when certain frequencies of the vibration exceed a predetermined level so as to establish when wear or damage has been produced. This can be a useful technique but is only capable of detecting significant amounts of wear or damage. This is because the vibration spectrum produced by the engine or bearing varies normally according to its operational condition such as speed, temperature, loading and so on. The amplitude above which one frequency of vibration will trigger a wear or damage signal must be sufficiently high that it is not triggered at the maximum amplitude experienced in normal use. This makes the apparatus relatively insensitive to incipient damage. Furthermore, although previous systems relying on the detection of spectral peaks can be used to identify known faults which cause spectral peaks at predictable frequencies, they are not capable of responding to more subtle spectral variations, such as distortion not involving sharp peaks, or unusual combinations of peaks, or unusual sequences. The response of previous systems is therefore severely limited as far as incipient or hitherto unknown fault conditions are concerned.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide monitoring methods of improved sensitivity.
According to the present invention there is provided a method of monitoring the condition of an assembly including the steps of deriving signals representative of the condition of the assembly, continuously building a model of the assembly at different stages of use through the life of the assembly such that the model is modified by any ageing of the assembly, and detecting the amount of deviation of the condition of the assembly from the model of the assembly.
Where the method is used to monitor the condition of a sound-generating assembly, the step of deriving signals representative of the condition of the assembly includes monitoring the acoustic spectrum of the assembly such that the model includes information about the acoustic spectrum of the assembly at different stages of use through the life of the assembly. The acoustic spectrum is preferably the acoustic spectrum transmitted through air, and the acoustic spectrum is monitored with a microphone.
The assembly may be an engine such as a gas-turbine engine. The step of deriving signals representative of the condition of the assembly may include monitoring the speed of the engine.
A multi-dimension vector may be established in respect of the condition of the assembly. The model of the assembly may be built using a sequence-learning neural net or a hidden Markov model.
A model may be built of a first assembly, this model being utilized on a second assembly of the same kind as the first assembly, and the model being modified by operation of the second assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
An engine monitoring apparatus and method, in accordance with the present invention, will now be described, by way of example with reference to the accompanying drawings, in which:
FIG. 1 shows the apparatus schematically; and
FIGS. 2 and 3 are graphs illustrating the change in acoustic spectrum.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The monitoring apparatus comprises a first acoustic channel 1 responsive to the sound generated by a gas-turbine engine 2 and a second channel 3 responsive to the operational condition of the engine. The two channels 1 and 3 together produce a condition vector output which is compared in a processor 4 with a model of the engine built up from previous operation of that engine.
The acoustic channel 1 includes a microphone 10 which is responsive to the airborne sound generated by the engine 2 in operation. The microphone 10 is not necessarily responsive to sound within
REFERENCES:
patent: H1006 (1991-12-01), Zwicke
patent: 4184205 (1980-01-01), Morrow
patent: 4215412 (1980-07-01), Bernier et al.
patent: 4336595 (1982-06-01), Adams et al.
patent: 4785403 (1988-11-01), Kuhlberg
patent: 4837695 (1989-06-01), Baldwin
patent: 4912661 (1990-03-01), Pottor
patent: 5070458 (1991-12-01), Gilmore et al.
patent: 5105372 (1992-04-01), Provost et al.
Rawlings Keith C.
Witcomb Roger C.
Ramirez Ellis B.
Smiths Industries Public Limited Company
Teska Kevin J.
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