Cyclic time averaging for machine monitoring

• US 20030130811A1
• Filed: 12/04/2002
• Published: 07/10/2003
• Est. Priority Date: 12/04/2001
• Status: Active Grant

• Current Assignee: SKF USA Incorporated (SKF)
• Original Assignee: SKF Condition Monitoring Inc
• Inventors: Boerhout, Johannes I.
• Granted Patent: US 6,789,025 B2
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• 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

A cyclic time averaging method is directed at processing time-domain vibration data of the machine to produce an averaged time waveform over a selected cyclic time period. It is not necessary to employ a triggering signal to obtain the averaged time waveform.

Claims

1. A method of monitoring the condition of a machine comprising:

receiving a set of N sampled vibration amplitude values taken at a corresponding set of discrete times spanning a period of operation of the machine;

deriving a set of n averaged amplitude data points, with n being less than N, wherein each of the n averaged amplitude points comprises an average of vibration amplitudes separated by a period M, and wherein at least some of the vibration amplitudes used in deriving the set of n averaged amplitude data points do not correspond to any of the N sample values.

2. The method of claim 1, wherein deriving the n averaged data points, comprises estimating an amplitude value between at least one pair of said N sample values.

3. The method of claim 2, wherein said estimating comprises interpolating.

4. The method of claim 3, wherein said interpolating comprises linear interpolation.

5. A method of monitoring the condition of a machine comprising:

generating a time-series vibration amplitude data set comprising N data points over a time period greater than a time period M without re-triggering data acquisition during the acquisition of said N points;

deriving n averaged data points, wherein each of the n points is representative of average amplitudes for points of the time-series data separated in time by M.

6. The method of claim 5, wherein M is based at least in part on the period of motion of a rotating or reciprocating component of the machine.

7. The method of claim 5, wherein said N points are separated in time by a sampling time period 1/F_s, wherein F_s comprises a sampling frequency, and wherein M=n/F_s.

8. The method of claim 7, wherein n is a non-integer value.

9. A system for monitoring the condition of a machine, the system comprising:

a data storage module that receives and stores N sampled vibration amplitude values taken at a corresponding set of discrete times spanning a period of operation of the machine; and

a data analyzer module, in communication with said data storage module, configured to derive from said N values a set of n averaged amplitude data points, wherein;

n is less than N;

each of said n points comprises an average of vibration amplitudes separated by a period M; and

at least some of the amplitudes used to derive said set of n points do not correspond to any of said N values.

10. The system of claim 9, wherein said data analyzer module is further configured to estimate an amplitude value between at least one pair of said N values.

11. The system of claim 10, wherein said data analyzer module is configured to estimate said amplitude value by interpolation.

12. The system of claim 11, wherein said data analyzer module is configured to estimate said amplitude value by linear interpolation.

13. A system for monitoring the condition of a machine, the system comprising:

a data acquisition module configured to generate a time-series vibration amplitude data set comprising N data points over a time period greater than a time period M, wherein said data acquisition module is configured to generate said N data points independently of a repeating synchronizing trigger signal;

a data analyzer module configured to derive n averaged data points, wherein each of said n points is representative of average amplitudes for points of said time-series data separated in time by said period M.

14. The system of claim 13, wherein M is based at least in part on the period of motion of a rotating or reciprocating component of the machine.

15. The system of claim 13, wherein said N points are separated in time by a sampling time period 1/F_s, wherein F_s comprises a sampling frequency, and wherein M=n/F_s.

16. The system of claim 15, wherein n is a non-integer value.

17. A system for monitoring the condition of a machine, the system comprising:

a data storage module that receives and stores time-series data comprising N sampled vibration amplitude values with corresponding times, wherein said time-series data spans a period of operation of the machine; and

a data analyzer module, in communication with said data storage module, configured to derive from said N values a set of n averaged amplitude data points, wherein;

n is less than N;

each of said n points comprises an average of vibration amplitudes separated by a period M; and

at least some of the amplitudes used to derive said set of n points are estimated from interpolation between at least one pair of said N values.

18. The system of claim 17, wherein M is based at least in part on the period of motion of a rotating or reciprocating component of the machine.

19. The system of claim 17, wherein said N points are separated in time by a sampling time period 1/F_s, wherein F_s comprises a sampling frequency, and wherein M=n/F_s.

20. The system of claim 19, wherein n is a non-integer value.

21. A system for monitoring the condition of a machine, the system comprising:

means for receiving N sampled vibration amplitude values taken at a corresponding set of discrete times spanning a selected period of operation of the machine; and

means for deriving n averaged amplitude data points, with n being less than N, wherein each of the n points comprises an average of vibration amplitudes separated by a period M, and wherein at least some of the amplitudes used in deriving said n data points do not correspond to any of said N values.

22. A system for analyzing vibration data configured to receive a plurality of vibration amplitude samples taken at discrete sampling times, said system comprising:

a first module configured to estimate vibration amplitudes at times between said discrete sampling times;

a second module configured to use said estimated vibration amplitudes in performing a cyclic average.