Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1998-10-30
2001-05-22
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S056000, C702S076000, C702S183000, C073S602000, C073S659000
Reexamination Certificate
active
06236950
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to signal processing and, more particularly to automatic generation of a stencil representative of signals having similar characteristics.
BACKGROUND OF THE INVENTION
In many different environments, signals may be monitored and analyzed to obtain information about the source of the signal. For example in one environment, electrodes of an electrocardiogram system may be positioned on a patient's body to sense and amplify electrocardiographic (ECG) signals originating from the patient's heart. The signal analyzer may then analyze the sensed and amplified ECG signals to obtain information about the condition of the patient's heart. In another environment, a vibration sensor may be positioned upon an operating automotive transmission to generate vibration signals that are indicative of the mechanical vibrations the transmission is experiencing during operation. A testing apparatus may then monitor and analyze the vibration signals generated by the operating transmission to determine whether the transmission has a mechanical defect.
One technique for analyzing the above signals has been to compare the frequency spectrum of the monitored signals to patterns or stencils that have been obtained from known signal sources. For example, several frequency spectra may be obtained from vibration signals generated by several properly operating transmissions. A technician may then analyze the obtained spectra and define a pattern or stencil which matches the obtained spectra. A testing apparatus then may monitor and compare the vibration signals generated by another transmission to the previously defined stencil in order to determine whether the monitored transmission is functioning correctly.
Similarly, several frequency spectra may be obtained from vibration signals generated by differential assemblies having a defective bearing. Again, a technician may analyze the obtained spectra and define a stencil which matches the obtained spectra. A testing apparatus then may monitor and compare the vibrations signals generated by another differential assembly to the previously defined stencil in order to determine whether the differential assembly has a defective bearing.
A disadvantage of the above signal analysis technique is that defining stencils is costly since a technician must analyze and manually define a stencil representative of signals having a known characteristic (e.g. proper functionality, defective bearing). As should be appreciated, analysis of the generated spectra by the technician is time consuming. Moreover, the time consuming analysis is amplified due to several stencils needing to be defined in order to monitor several types of components, and detect several types of conditions.
Another disadvantage of the above signal analysis technique is that the quality of the defined stencils is highly dependant upon the skill level of the technician defining the stencils. For example, if the technician defines a stencil too strictly, then a testing apparatus may fail to match a monitored signal to the defined signal even though the monitored signal was generated by a device having the condition represented by the defined stencil. Conversely, if the technician defines the stencil too broadly, then a testing apparatus may improperly match the monitored signal to the defined stencil even though the monitored signal was generated by a device not having the condition represented by the defined stencil.
What is needed, therefore, is a method and apparatus for automatically constructing stencils that are representative of signals having similar characteristics.
DISCLOSURE OF THE INVENTION
In accordance with one embodiment of the present invention, there is provided a method of automatically constructing a stencil that is representative of signals having similar characteristics. One step of the method includes obtaining from a frequency spectrum for a signal, characteristic frequency boundaries that define characteristic frequency intervals for the signal. Another step of the method includes generating the stencil representative of signals having similar characteristics by defining stencil components based upon the characteristic frequency intervals and the frequency spectrum.
Pursuant to another embodiment of the present invention, there is provided a stencil generator for automatically constructing a stencil that is representative of signals having similar characteristics. The stencil generator includes a component generator coupled to a boundary extractor. The boundary extractor is operable to receive a frequency spectrum of a signal. Moreover, the boundary extractor is operable to obtain from the received frequency spectrum characteristic frequency boundaries for the signal. The component generator is operable to receive the frequency spectrum, and receive the characteristic frequency boundaries from the boundary extractor. The component generator is also operable to define stencil components based upon the characteristic frequency boundaries and the frequency spectrum.
Pursuant to yet another embodiment of the present invention, there is provided a stencil generator for automatically constructing a stencil that is representative of signals having similar characteristics. The stencil generator includes a processor that is coupled to a memory device having stored therein instructions. The instructions when executed by the processor cause the processor to obtain from a frequency spectrum for a signal, characteristic frequency boundaries that define characteristic frequency intervals for the signal. The instructions when executed by the processor further cause the processor to generate the stencil representative of signals having similar characteristics by defining stencil components based upon the characteristic frequency intervals and the frequency spectrum.
It is an object of the present invention to provide a new method and apparatus for constructing a stencil that is representative of a class of signals.
It is an object of the present invention to provide an improved method and apparatus for constructing a stencil that is representative of a class of signals.
It is yet another object of the present invention to provide a method and apparatus that automate stencil construction in order to lower the cost associated with stencil construction.
It is still another object of the present invention to provide a method and apparatus that construct a stencil that results in a testing apparatus having a low rate of misclassification of a monitored signal.
The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.
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Article
Bui Bryan
Caterpiller Inc.
Hoff Marc S.
Maginot Addison & Moore
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