System and method for analyzing signals of rotating machines

• US 6,332,116 B1
• Filed: 04/19/2000
• Issued: 12/18/2001
• Est. Priority Date: 04/19/2000
• Status: Expired due to Term

• Current Assignee: National Instruments Corporation (Emerson Electric Company)
• Original Assignee: National Instruments Corporation (Emerson Electric Company)
• Inventors: Shao, Hui, Qian, Shie
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): TSAI, CAROL S W
• Application Number:
  US09/551,924
• Time in Patent Office: 608 Days
• Field of Search: 702/182, 702/183, 702/76, 702/147, 736/59, 736/60, 735/79, 735/83, 735/93, 736/09, 735/59, 340/681, 340/682, 340/683, 324/207, 324/25, 324/226, 708/400
• US Class Current: 702/183
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence

Abstract

A signal analysis system and method for analyzing an input signal acquired from a mechanical system. The mechanical system may include at least one rotating apparatus. The signal analysis system may be configured to: (a) receive samples of the input signal, (b) perform an invertible joint time-frequency transform (e.g. a Gabor transform) on the samples of the input signal to produce a first array of coefficients which depend on time and frequency, (c) select first coefficients from the first array which correspond to a first subset of one or more order components in the input signal, (d) generate a time domain signal from the first coefficients, and (e) present the time domain signal to a user on a presentation device. The signal analysis system generate the time domain signal from the first coefficients by performing an inverse joint time-frequency transform on the first coefficients. The signal analysis system extract the one or more order components for presentation to the user by masking out all coefficients except those corresponding to the one or more components. Conversely, the signal analysis system may suppress the one or more order components, i.e. present to the user the input signal minus the one or more order components by masking out coefficients corresponding to the one or more components and keeping the remaining coefficients.

Claims

1. A method for analyzing an input signal acquired from a mechanical system containing a rotating apparatus, the method comprising:

receiving samples of the input signal, wherein the input signal is sampled in time;

performing an invertible joint time-frequency transform on the samples of the input signal to produce a first array of coefficients which depend on time and frequency;

selecting first coefficients from the first array which correspond to a first subset of one or more order components in the input signal;

generating a time domain signal from the first coefficients; and

presenting the time domain signal to a user on a presentation device, wherein the time domain signal is useable in analyzing the mechanical system; and

adjusting the mechanical system in response to analysis of the time domain signal, wherein said adjusting the mechanical system comprises one or more of;

     1) changing a design of the mechanical system;

     2) replacing one or more components of the mechanical system;

     3) predicting a failure of one or more components of the mechanical system; and

     4) adding a sound-absorbent material to one or more locations of the mechanical system.

2. The method of claim 1, wherein said generating the time domain signal from the first coefficients comprises performing an inverse joint time-frequency transform on the first coefficients.

3. The method of claim 1, further comprising selecting the first subset of one or more order components prior to said selecting the first coefficients from the first array.

4. The method of claim 3, wherein said selecting the first subset of one or more order components comprises selecting a second subset of one or more order components in the input signal for removal, wherein the first subset of one or more order components corresponds to order components of the input signal which are not included in the second subset of one or more order components.

5. The method of claim 1, wherein the input signal comprises a plurality of order components, the method further comprising:

displaying a visual representation of the first array of coefficients, wherein the visual representation indicates at least one of the plurality of order components;

receiving user input which indicates a user'"'"'s selection of one or more points in the visual representation, wherein said user input operates to select the first coefficients from the first array.

6. The method of claim 5, further comprising determining one or more time-frequency curves corresponding to the one or more points, wherein the one or more time-frequency curves are used to determine the first coefficients from the first array.

7. The method of claim 6, wherein said selecting the first coefficients from the first array comprises selecting coefficients of the first array which correspond to the one or more time-frequency curves;

wherein the one or more time-frequency curves correspond to the first subset of one or more order components in the input signal.

8. The method of claim 7, wherein said selecting the first coefficients from the first array comprises selecting coefficients of the first array which reside in a union of neighborhoods containing the one or more time-frequency curves respectively.

9. The method of claim 6, wherein said selecting the first coefficients from the first array comprises selecting coefficients of the first array which do not correspond to the one or more time-frequency curves.

10. The method of claim 9, wherein said selecting the first coefficients from the first array comprises selecting coefficients of the first array which reside in the complement of the union of neighborhoods containing the one or more time-frequency curves respectively.

11. The method of claim 1, wherein said selecting the first coefficients from the first array comprises:

constructing an order mask array which corresponds to the first subset of one or more order components;

applying the order mask array to the first array of coefficients to select the first coefficients.

12. The method of claim 11, the method further comprising:

determining one or more time-frequency curves which corresponding to the one or more order components of the first subset;

wherein said constructing the order mask array further comprises setting coefficients of the order mask array equal to one in a union of neighborhoods containing the one or more time-frequency curves of the first subset respectively.

13. The method of claim 11, further comprising:

determining one or more time-frequency curves which corresponding to a second subset of one or more order components in the input signal;

wherein said constructing the order mask array further comprises setting coefficients of the order mask array equal to zero in a union of neighborhoods containing the one or more time-frequency curves of the second subset respectively, wherein the first subset of order components comprises order components of the input signal which are not included in the second subset.

14. The method of claim 11, wherein said constructing the order mask comprises:

computing an instantaneous rotation frequency signal with respect to time, wherein the instantaneous rotation frequency signal corresponds to a fundamental order component of the input signal;

wherein the order mask array is constructed using one or more multiples of the instantaneous rotation frequency signal.

15. The method of claim 11, wherein said constructing the order mask further comprises:

receiving a first signal indicative of speed of rotations of the rotating apparatus;

wherein the instantaneous rotation frequency signal is computed in response to the first signal.

16. The method of claim 14, further comprising:

generating an instantaneous order frequency signal as a multiple of the instantaneous rotation frequency signal in response to a desired order number;

wherein said constructing the order mask array further comprises setting coefficients of the order mask array equal to a first value in a first neighborhood of the instantaneous order frequency signal.

17. The method of claim 1, wherein said presentation device comprises at least one speaker;

wherein said presenting the time domain signal to the user on the presentation device comprises audially presenting the time domain signal as sound output from the at least one speaker.

18. The method of claim 1, wherein said presentation device comprises a display;

wherein said presenting the time domain signal to the user on the presentation device comprises visually displaying the time domain signal on the display.

19. The method of claim 1, wherein the samples of the input signal are equally space in time.

20. The method of claim 1, wherein the joint time-frequency transform comprises the Gabor transform.

21. The method of claim 1, wherein the input signal comprises a signal generated by a microphone proximate to the mechanical system.

22. The method of claim 1, wherein the input signal comprises an accelerometer signal generated by an accelerometer coupled to the mechanical system.

23. A method for analyzing an input signal acquired from a mechanical system containing a rotating apparatus, the method comprising:

receiving samples of the input signal, wherein the input signal is sampled in time;

performing an invertible joint time-frequency transform on the samples of the input signal to produce a first array of coefficients which depend on time and frequency;

selecting one or more order components in the input signal, wherein said selecting the one or more order components in the input signal comprises;

receiving a first signal indicative of speed of rotations of the rotating apparatus;

computing an instantaneous rotation frequency signal with respect to time in response to the first signal, wherein the instantaneous rotation frequency signal corresponds to a fundamental order component of the input signal;

generating one or more multiples of the instantaneous rotation frequency signal, wherein each of said one or more order components corresponds to one of said multiples;

selecting a first subset of coefficients from the first array in response to said selection of the one or more order components in the input signal;

generating a time domain signal from the first subset of coefficients; and

presenting the time domain signal to a user on a presentation device;

wherein the time domain signal is useable in analyzing the mechanical system.

24. The method of claim 23, wherein said generating the time domain signal from the first subset of coefficients comprises performing an inverse joint time-frequency transform on the subset of coefficients.

25. The method of claim 23, wherein said selecting the first subset of coefficients from the first array comprises selecting coefficients of the first array which correspond to the one or more order components.

26. The method of claim 23,

wherein said selecting one or more order components in the input signal comprises selecting the one or more order components for removal;

wherein said selecting the first subset of coefficients from the first array comprises selecting coefficients of the first array which correspond to the input signal with the one or more order components removed.

27. The method of claim 23, wherein said selecting the one or more order components is performed in response to user input.

28. The method of claim 23, wherein said selecting the one or more order components includes determining one or more time-frequency curves corresponding to the one or more order components.

29. A method for analyzing one or more order components from a input signal generated by a mechanical system containing a rotating apparatus, the method comprising:

receiving samples of the input signal;

performing an invertible joint time-frequency transform on the samples of the input signal to produce a first array of coefficients which depend on time and frequency;

constructing an order mask array in response to user input;

masking the first array of coefficients with the order mask array to generate a second array of coefficients which depend on time and frequency;

generating a time domain signal from the second array of coefficients;

presenting the time domain signal to a user on a presentation device;

wherein the time domain signal is useable in analyzing the mechanical system.

30. The method of claim 29, wherein said constructing an order mask comprises:

computing an instantaneous rotation frequency signal with respect to time;

multiplying the instantaneous rotation frequency signal by one or more order numbers to generate one or more instantaneous order frequency signals;

generating a third array of coefficients, wherein coefficients of the third array equal a first value in one or more time-frequency neighborhoods of the one or more instantaneous order frequency signals, wherein the order mask comprises the third array, wherein the coefficients of the third array equal a second value outside the one or more time-frequency neighborhoods.

31. The method of claim 30, wherein the first value equals one and the second value equals zero.

32. The method of claim 30, wherein the first value equals zero and the second value equals one.

33. The method of claim 30, wherein said constructing the order mask further comprises:

receiving a first signal indicative of speed of rotations of the rotating apparatus;

wherein the instantaneous rotation frequency signal is computed in response to the first signal.

34. The method of claim 33, wherein the first signal comprises a tachometer signal generated by a tachometer coupled to the mechanical system.

35. The method of claim 30, wherein the one or more time-frequency neighborhoods have frequency bandwidths controlled by a second user input.

36. The method of claim 30, further comprising computing the one or more order numbers in response to the user input.

37. The method of claim 36, wherein said computing the one or more order numbers in response to the user input comprises:

displaying a visual representation of the first array of coefficients on a display screen;

receiving location data in response to one or more user selection event specifying one or more locations on the display screen;

computing one or more time-frequency pairs in response to the location data;

dividing the frequency of each time-frequency pair by a value of the instantaneous rotation frequency signal corresponding to the time of the time-frequency pair.

38. The method of claim 36, wherein said computing the one or more order numbers in response to the user input comprises:

rescaling the first array of coefficients to generate a fourth array of coefficients, wherein the rescaled fourth array of coefficients depend on order and time;

displaying a visual representation of the fourth array of coefficients on a display screen;

receiving location data in response to one or more user selection events specifying one or more locations on the display screen.

39. A method for analyzing one or more order components from a first signal generated by a mechanical system containing a rotating apparatus, the method comprising:

receiving samples of the first signal;

performing a forward joint time-frequency transform on the first signal to produce a first array of coefficients which depend on time and frequency, wherein the forward joint-time frequency transform is invertible;

constructing a scaling array in response to user input;

scaling the first array of coefficients by the scaling array to generate a second array of coefficients;

generating a time domain signal from the second array of coefficients;

presenting the time domain signal to a user on a presentation device;

wherein the time domain signal is useable in analyzing the mechanical system.

40. The method of claim 39, wherein said scaling emphasizes one or more order components in the first signal, wherein said constructing the scaling array is performed in response to the user input.

41. The method of claim 40, wherein said scaling de-emphasizes one or more order components in the first signal, wherein said constructing the scaling array is performed in response to user input.

42. A system for analyzing operation of a rotating apparatus in a mechanical system, the system comprising:

an input for receiving samples of the input signal, wherein the input signal is acquired from the mechanical system containing the rotating apparatus, wherein the input signal is sampled in time;

a processor coupled to the input;

a memory medium coupled to the processor which stores analysis software;

wherein the processor is operable to execute the analysis software to;

perform an invertible joint time-frequency transform on the input signal to produce a first array of coefficients which depend on time and frequency;

select a first subset of coefficients from the first array which correspond to a first subset of one or more order components, wherein, in selecting the first coefficients from the first array, the processor is operable to;

construct an order mask array which corresponds to the first subset of one or more order components; and

apply the order mask array to the first array of coefficients to select the first coefficients; and

generate a time domain signal from the subset of coefficients; and

a presentation device coupled to the processor which is operable to present the time domain signal to a user;

wherein the time domain signal is useable in analyzing operation of the rotating apparatus in the mechanical system.

43. The system of claim 42, wherein, in generating the time domain signal, the processor is operable to perform an inverse joint time-frequency transform on the first subset of coefficients.

44. The system of claim 42, further comprising an input device coupled to the processor, wherein the input device is operable to receive user input selecting the first subset of one or more order components, wherein the first subset of one or more order components indicate the first subset of coefficients from the first array.

45. The system of claim 42, further comprising an input device coupled to the processor, wherein the input device is operable to receive user input selecting a second subset of one or more order components in the input signal for removal, wherein the first subset of one or more order components corresponds to order components of the input signal which are not included in the second subset of one or more order components.

46. The system of claim 42, wherein the input signal comprises a plurality of order components, the system further comprising:

a display which displays a visual representation of the first array of coefficients, wherein the visual representation indicates at least one of the a plurality of order components;

an input device operable to receive user input which indicates a user'"'"'s selection of one or more points in the visual representation, wherein said user input operates to select the first coefficients from the first array.

47. A memory medium comprising program instructions for analyzing an input signal acquired from a mechanical system containing a rotating apparatus, wherein the program instructions are executable to implement:

receiving samples of the input signal, wherein the input signal is sampled in time;

performing an invertible joint time-frequency transform on the input signal to produce a first array of coefficients which depend on time and frequency;

masking the first array of coefficients with the order mask array to generate a second array of coefficients which depend on time and frequency;

generating a time domain signal from the second array of coefficients; and

presenting the time domain signal to a user on a presentation device;

wherein the time domain signal is useable in analyzing the mechanical system.