Process device diagnostics using process variable sensor signal

• US 20040024568A1
• Filed: 06/05/2003
• Published: 02/05/2004
• Est. Priority Date: 06/25/1999
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Eryurek, Evren, Kavaklioglu, Kadir, Esboldt, Steven R.
• Granted Patent: US 7,010,459 B2
• Time in Patent Office: Days
• US Class Current: 702/182
• CPC Class Codes: G01F 1/3209 using Karman vortices
• CPC Class Codes: G01F 1/60 Circuits therefor
• CPC Class Codes: G01F 1/8477 with multiple measuring conduits
• CPC Class Codes: G01F 25/10 of flowmeters
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods
• CPC Class Codes: G05B 23/024 Quantitative history assessment, e.g. mathematical relationships between available data; Functions therefor; Principal component analysis [PCA]; Partial least square [PLS]; Statistical classifiers, e.g. Bayesian networks, linear regression or correlation analysis; Neural networks
• CPC Class Codes: G05B 9/03 with multiple-channel loop, i.e. redundant control systems
• CPC Class Codes: G07C 3/00 Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
• CPC Class Codes: G08C 19/02 in which the signal transmitted is magnitude of current or voltage G08C19/36, G08C19/38 take precedence

Abstract

A diagnostic device for use in a process control system receives a sensor signal related to a process variable of a process sensed by a process variable sensor. A signal preprocessor provides a sensor power signal output as a function of a frequency distribution of power in the sensor signal. A process condition is determined based upon the sensor power signal.

Claims

1. A diagnostic device for use in a process control system, comprising:

a sensor signal input, the sensor signal related to a process variable of a process fluid of a process, the process variable sensed by a process variable sensor;

a signal preprocessor coupled to the sensor input having a sensor power signal output as a function of a frequency distribution of power in the sensor signal; and

a signal evaluator coupled to the sensor power signal output having a condition output related to a condition of the process.

2. The diagnostic device of claim 1 wherein the sensor signal has a frequency content of at least about 50 Hz.

3. A transmitter including the diagnostic device of claim 1.

4. The diagnostic device of claim 1 wherein the process variable sensor comprises a pressure sensor.

5. The diagnostic device of claim 1 wherein the process variable sensor comprises electrodes in a magnetic flowmeter.

6. The diagnostic device of claim 1 wherein the process variable sensor comprises a sensor in a vortex flowmeter.

7. The diagnostic device of claim 1 wherein the process variable sensor comprises a sensor in a coriolis flowmeter.

8. The diagnostic device of claim 1 wherein the signal preprocessor isolates a frequency range of the sensor signal.

9. The diagnostic device of claim 1 signal preprocessor isolates a frequency range of the sensor signal.

10. The diagnostic device of claim 1 wherein the sensor signal has a frequency of between about 0 Hz and about 200 Hz.

11. The diagnostic device of claim 1 wherein the function comprises power spectral density.

12. The diagnostic device of claim 1 wherein the function is related to a Fourier transform of the sensor signal.

13. The diagnostic device of claim 1 wherein the function comprises a wavelet transform of the sensor signal.

14. The diagnostic device of claim 1 wherein the signal preprocessor includes a filter.

15. The diagnostic device of claim 1 wherein the condition relates to operation of a process control device.

16. The diagnostic device of claim 1 wherein the diagnostic device is implemented in a process monitor.

17. The diagnostic device of claim 1 wherein the diagnostic device is implemented in a control system.

18. The diagnostic device of claim 1 wherein the diagnostic device couples to a communication bus.

19. The diagnostic device of claim 18 wherein the communication bus comprises a two-wire loop.

20. The diagnostic device of claim 19 wherein the diagnostic device is fully powered with power received from the two-wire loop.

21. The diagnostic device of claim 1 wherein the sensor power signal output relates to a vibration noise signal carried in process fluid of the process.

22. The diagnostic device of claim 1 wherein the process variable sensor comprises a sensor in an ultrasonic flowmeter.

23. The diagnostic device of claim 1 wherein the condition of the process is related to condition of a process device selected from the group of devices consisting of valves, pumps, pump seals, discharge systems, actuators, solenoids, compressors, turbines, agitators, dampers, piping, fixtures and tanks

24. The diagnostic device of claim 1 wherein the signal evaluator compares the sensor power signal with a stored value.

25. The diagnostic device of claim 1 wherein the signal evaluator comprises a neural network.

26. The diagnostic device of claim 1 signal evaluator comprises fuzzy logic.

27. A diagnostic method performed in a process control environment, the method comprising:

obtaining a process variable sensor signal;

determining a frequency distribution of power in the process variable sensor signal; and

evaluating the frequency distribution of power in the process variable sensor signal and providing a condition output related to the process.

28. The method of claim 27 wherein determining includes filtering the process variable sensor signal.

29. The method of claim 27 wherein determining includes performing a Fourier transformation on the process variable sensor signal.

30. The method of claim 29 wherein determining includes performing a wavelet transformation.

31. The method of claim 30 wherein performing a wavelet transform comprises performing a discrete wavelet transform.

32. The method of claim 27 wherein evaluating comprises comparing frequency distribution of power in the process variable sensor signal to a stored value.

33. The method of claim 27 wherein evaluating comprises evaluating the frequency distribution of power in the process variable sensor signal to a neural network.

34. The method of claim 27 wherein evaluating comprises applying a rule to the frequency distribution of power in the process variable sensor signal.

35. The method of claim 27 wherein the process variable sensor signal comprises a pressure sensor signal.

36. The method of claim 27 wherein the process variable sensor signal comprises a sensor output from a coriolis flowmeter.

37. The method of claim 27 wherein the process variable sensor signal comprises a sensor output from a vortex flowmeter.

38. The method of claim 27 wherein the process variable sensor signal comprises electrode outputs from a magnetic flowmeter.

39. The method of claim 27 wherein the process variable sensor signal comprises an output from a sensor in a coriolis flowmeter.

40. The method of claim 27 wherein the process variable sensor signal has a bandwidth of at least about 50 Hz.

41. The method of claim 27 wherein the condition output relates to a condition of a process control device.

42. The method of claim 27 including fully powering the diagnostic device with power from a two-wire loop.

43. A process transmitter implementing the method of claim 27.

44. A process control system implementing the method of claim 27.

45. A process control device implementing the method of claim 27.

46. A process monitor implementing the method of claim 27.

47. The method of claim 27 wherein the frequency distribution of power in the process variable sensor signal comprises power spectral density.

48. A computer-readable medium having stored thereon instructions executable by a microprocessor system in a diagnostic device to diagnose condition of a process, the instructions comprising:

obtaining a process variable sensor signal;

determining a frequency distribution of power in the process variable sensor signal; and

evaluating the frequency distribution of power in the process variable sensor signal and providing a condition output related to the process.

49. A diagnostic device for use in a process control system, comprising:

a sensor signal input, the sensor signal related to a process variable of a process fluid of a process, the process variable sensed by a process variable sensor;

signal preprocessing means for determining a frequency distribution of power in the sensor signal; and

signal evaluating means for diagnosing a condition of the process based upon the frequency distribution of power in the sensor signal.