VIBRATION MONITORING SYSTEM

• US 20140142871A1
• Filed: 06/05/2012
• Published: 05/22/2014
• Est. Priority Date: 06/28/2011
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lombriser, Clemens, Schott, Wolfgang H., Weiss, Brat E.
• Application Number:
  US14/128,679
• Publication Number:
  US 20140142871A1
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 7/022 Vibration control arrangements, e.g. for generating random vibrations
• CPC Class Codes: G01M 7/025 Measuring arrangements
• CPC Class Codes: G01N 29/04 Analysing solids using acoustic emission techniques G01N29/14
• CPC Class Codes: G01V 1/008 Earthquake measurement or prediction event detection for microseismic events G01V1/288
• CPC Class Codes: G01V 1/01 Measuring or predicting earthquakes
• CPC Class Codes: G05B 23/0235 based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold

Abstract

The invention is directed to a method for monitoring vibrations to detect distinct vibration events in an acceleration waveform converted into acceleration samples. The method comprises: storing the acceleration samples as a sequence of acceleration frames into a cache memory (S110); detecting the presence or absence of a distinct vibration event in each of said acceleration frames (S160); in case of detecting a distinct vibration event in an acceleration frame, forwarding said acceleration frame from said cache memory to a long-term storage device (S170).

Claims

1. A method for monitoring vibrations to detect distinct vibration events, the method comprising:

storing acceleration samples as a sequence of acceleration frames into a cache

memory;

detecting a presence or an absence of a distinct vibration event in each of said acceleration frames; and

forwarding an acceleration frame from said cache memory to a long-term storage device in response to detecting the distinct vibration event in said acceleration frame.

2. The method of claim 1, wherein

each of said acceleration frames has a fixed length;

and

each of said acceleration frames comprises several frames stored in said cache memory.

3. The method of claim 1, further comprising:

computing velocity frames from said acceleration frames stored in said cache memory; and

computing velocity parameters for each of said velocity frames;

wherein the detecting step comprises detecting the presence or the absence of distinct vibrations in each of said velocity frames computed from said acceleration frames based on the computed velocity parameters.

4. The method of claim 3, further comprising:

storing said velocity parameters for each of said velocity frames to said long-term storage device.

5. The method of claim 4, wherein:

the long-term storage device is a memory comprising a first address space and a second address space;

said acceleration frame is forwarded from said cache memory to the first address space of the memory in response to detecting the distinct vibration event; and

said velocity parameters of each said velocity frames are stored to the second address space of the memory.

6. The method of claim 3, wherein said velocity frames are computed from said acceleration frames by a method comprising:

computing a mean value of said acceleration frames using a forward Euler integration; and

integrating DC-offset compensated acceleration frames using a backward Euler integration.

7. The method of claim 3, wherein velocity parameters for each of said velocity frames comprises:

the maximum absolute vibration velocity |v_i|_max of each said velocity frame within a window of a length W, where W is smaller than or equal to the length of a velocity frame;

the position t_i^s of said maximum absolute vibration velocity |v_i|_max within said window of length W; and

the dominant frequency f_i of each said velocity frames.

8. The method of claim 7, further comprising:

constructing windowed velocity frames of length W by a method comprising;

shifting the velocity samples of each velocity frame so that the velocity sample with maximum absolute vibration velocity |v_i|_max is in the centre of said window of length W; and

dropping the velocity samples of each velocity frame outside said window of length W.

9. The method of claim 8, wherein said dominant frequency f_i of each said velocity frame is detected by a method comprising:

computing the magnitude of the frequency spectrum of each said windowed velocity frame of length W using a real-value W-point Bruun Fast Fourier Transform; and

searching for the frequency index which maximizes the magnitude of said frequency spectrum.

10. The method of claim 9, wherein the magnitude of the frequency spectrum is computed by using the law of cosines in the last stage of said real-value W-point Bruun Fast Fourier Transform.

11. The method of claim 9, wherein the computation of the magnitude of the frequency spectrum using said real-value W-point Bruun Fast Fourier Transform further comprises:

multiplying said windowed velocity frame of length W with a filter window function w of size W;

storing the result of the multiplication of said windowed velocity frame of length W and said window function w of size W; and

computing simultaneously the first stage of the Bruun Fast Fourier Transform.

12. The method of claim 9, wherein the detection of said dominant frequency f_i further comprises the step of pre-scaling the velocity samples of each said windowed velocity frame of length W by bit-shifting so that the maximum absolute vibration velocity |v_i|_max is represented by the maximum valid digital number.

13. The method of claim 7, wherein the presence of the distinct vibration event is detected in each of said velocity frames by a method comprising:

comparing said maximum absolute vibration velocity |v_i|_max to a predefined threshold value v_th(f_i); and

detecting an event if said maximum absolute vibration velocity |v_i|_max exceeds said threshold value v_th(f_i).

14. The method of claim 1, wherein the cache memory is organized into a ring buffer and provides at least one buffer for storing the filtered acceleration samples as a sequence of acceleration frames.

15. An apparatus for monitoring vibrations to detect distinct vibration events, wherein the apparatus is configured for performing the steps of the method comprising:

an integration unit configured to store the acceleration samples as a sequence of acceleration frames into a cache memory;

a frequency detection unit configured to detect a presence or an absence of a distinct vibration event in each of said acceleration frames; and

an event detection unit configured to forward said acceleration frame from said cache memory to a long-term storage device in case of detecting a distinct vibration event in an acceleration frame.

16. A computer readable non-transitory article of manufacture tangibly embodying computer readable instructions which, when executed, causes a computer to carry out the steps of a method comprising:

storing acceleration samples as a sequence of acceleration frames into a cache memory;

detecting a presence or an absence of a distinct vibration event in each of said acceleration frames; and

forwarding said acceleration frame from said cache memory to a long-term storage device in case of detecting a distinct vibration event in an acceleration frame.