Vibrating conduit parameter sensors, methods and computer program products for generating residual-flexibility-compensated mass flow estimates

• US 6,272,438 B1
• Filed: 08/05/1998
• Issued: 08/07/2001
• Est. Priority Date: 08/05/1998
• Status: Expired due to Term

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Normen, David F., Cunningham, Timothy J., Shelley, Stuart J.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): Raymond, Edward
• Application Number:
  US09/129,746
• Time in Patent Office: 1,098 Days
• Field of Search: 73/860.38, 73/3, 73/861.18, 702/45, 702/100, 702/56, 702/33, 702/54
• US Class Current: 702/56
• CPC Class Codes: G01F 1/8413 means for influencing the flowmeter's motional or vibrational behaviour, e.g., conduit support or fixing means, or conduit attachments
• CPC Class Codes: G01F 1/8436 signal processing
• CPC Class Codes: G01F 1/8477 with multiple measuring conduits

Abstract

A process parameter associated with a material contained in a conduit is estimated by estimating a real normal modal residual flexibility component associated with a real normal mode of motion of the conduit. A plurality of motion signals representing motion of the conduit is received. A residual-flexibility-compensated estimate of mass flow is generated from the received plurality of motion signals and the estimated real normal modal residual flexibility component. Related apparatus and computer program products are also described.

Claims

1. In a parameter sensor including a conduit configured to contain a material, a method of estimating a process parameter comprising the steps of:

estimating a real normal modal residual flexibility component associated with a real normal mode of motion of the conduit;

receiving a plurality of motion signals representing motion of the conduit; and

generating a residual-flexibility-compensated estimate of mass flow from the received plurality of motion signals and the estimated real normal modal residual flexibility component.

2. A method according to claim 1, further comprising the step of exciting the conduit at an excitation frequency, and:

wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating a real normal modal residual flexibility component associated with the real normal mode at the excitation frequency;

wherein said step of receiving comprises the step of receiving a plurality of motion signals representing motion of the conduit in response to the excitation; and

wherein said step of generating a residual-flexibility-compensated estimate comprises the steps of;

determining motion of the conduit at the excitation frequency from the received plurality of motion signals; and

generating a residual-flexibility-compensated estimate of mass flow from the determined motion at the excitation frequency and the estimated real normal modal residual flexibility component.

3. A method according to claim 2, wherein said step of estimating a real normal modal residual flexibility component comprises the steps of:

resolving motion of the conduit at the excitation frequency under a substantially zero mass flow condition into a plurality of real normal modal components associated with a plurality of real normal modes; and

estimating a real normal modal residual flexibility component of the conduit motion associated with a mode of the plurality of real modes from the resolved plurality of real normal modal components.

4. A method according to claim 2, wherein said step of estimating a real normal modal residual flexibility component comprises the steps of:

identifying a function that describes motion of the conduit in a real normal mode as a function of frequency;

determining motion of the conduit at a selected frequency; and

estimating a real normal modal residual flexibility component at the excitation frequency associated with the real normal mode by fitting the determined motion at the selected frequency to the identified function.

5. A method according to claim 4, wherein said step of estimating comprises the steps of:

determining a scaling transformation that relates the determined motion to the identified function; and

estimating a real normal modal residual flexibility component at the excitation frequency from the determined scaling transformation.

6. In a parameter sensor including a conduit configured to contain a material, a method of estimating a process parameter comprising the steps of:

receiving a first plurality of motion signals representing motion of the conduit under a substantially zero mass flow condition;

processing the received first plurality of motion signals to resolve the motion of the conduit under the substantially zero mass flow condition into a plurality of real normal modal components;

estimating a real normal modal residual flexibility component from the resolved plurality of real normal modal components;

receiving a second plurality of motion signals representing motion of the conduit; and

generating a residual-flexibility-compensated estimate of mass flow from the received second plurality of motion signals and the estimated real normal modal residual flexibility component.

7. A method according to claim 6, wherein said step of processing the received first plurality of motion signals comprises the step of mode pass filtering the received first plurality of motion signals to produce a mode pass filtered representation of the conduit motion under the substantially zero mass flow condition.

8. A method according to claim 7:

wherein said step of processing the first plurality of motion signals comprises the step of estimating real normal modal motion under the substantially zero mass flow condition;

wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating residual real normal modal motion from the estimated real normal modal motion under the substantially zero mass flow condition; and

wherein said step of generating a residual-flexibility-compensated estimate comprises the steps of;

estimating real normal modal motion from the received second plurality of motion signals; and

generating a residual-flexibility-compensated estimate of mass flow under the unknown mass flow condition from the estimated residual real normal modal motion and the estimated real normal modal motion.

9. A method according to claim 6:

wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating a first real normal modal residual flexibility component associated with a first real normal mode of conduit motion under the substantially zero mass flow condition;

wherein said step of estimating a real normal modal residual flexibility component further comprises the step of estimating a second real normal modal residual flexibility component associated with a second real normal mode of conduit motion under a non-zero mass flow condition; and

wherein said step of generating a residual-flexibility-compensated estimate of mass flow comprises the step of generating a residual-flexibility-compensated estimate of mass flow from the received second plurality of motion signals, the estimated first real normal modal residual flexibility component and the estimated second real normal modal residual flexibility component.

10. A method according to claim 9, wherein the first real normal mode is more highly correlated with flow of material in the conduit than the second real normal mode.

11. A method according to claim 9, wherein said step of estimating a second real normal modal residual flexibility component comprises the steps of:

receiving a third plurality of motion signals representing motion of the conduit under a non-zero mass flow condition; and

processing the received third plurality of motion signals to estimate the second real normal modal residual flexibility component.

12. A method according to claim 9, wherein said step of estimating a second real normal modal residual flexibility component comprises the steps of:

identifying a function describing motion in the second real normal mode as a function of frequency; and

estimating the second real normal modal residual flexibility component from the identified function.

13. A method according to claim 9:

wherein said step of estimating a real normal modal residual flexibility component comprises the step of generating a first estimate of the second real normal modal residual flexibility component;

wherein said step of generating a residual-flexibility-compensated estimate of mass flow comprises the step of generating a first residual-flexibility-compensated estimate of mass flow from the first estimate of the second real normal modal residual flexibility component;

wherein said step of estimating a real normal modal residual flexibility component comprises the step of generating a second estimate of the second real normal modal residual flexibility component; and

wherein said step of generating a residual-flexibility-compensated estimate of mass flow comprises the step of generating a second residual-flexibility-compensated estimate of mass flow from the second estimate of the second real normal modal residual flexibility component.

14. In a parameter sensor including a conduit configured to contain a material, a method of estimating a process parameter comprising the steps of:

identifying a function operative to describe motion of the conduit in a real normal mode as function of frequency;

determining a first value representing motion of the vibrating conduit at a selected frequency;

estimating a real normal modal residual flexibility component associated with the real normal mode by fitting the first value to the identified function;

receiving a plurality of motion signals representing motion of the conduit; and

generating a residual-flexibility-compensated estimate of mass flow from the received second plurality of motion signals and the estimated real normal modal residual flexibility component.

15. A method according to claim 14, wherein said step of estimating a real normal modal residual flexibility component comprises the steps of:

determining a scaling transformation relating the first value to the identified function; and

estimating a real normal modal residual flexibility component associated with the real normal mode from the identified function and the determined scaling transformation.

16. A method according to claim 15, wherein said step of determining a scaling transformation comprises the steps of:

evaluating the identified function at the selected frequency to generate a second value; and

determining a scaling transformation relating the first value to the identified function from the first value and the second value.

17. A method according to claim 16:

wherein said step of determining a first value comprises the step of determining a first plurality of values at a plurality of selected frequencies;

wherein said step of evaluating comprises the step of evaluating the identified function at the plurality of selected frequencies to generate a second plurality of values; and

wherein said step of determining a scaling transformation comprises the step of determining a scaling transformation from the first plurality of values and the second plurality of values.

18. A method according to claim 14, wherein the real normal mode comprises a real normal mode substantially correlated with mass flow.

19. A method according to claim 14, further comprising the step of exciting the conduit at an excitation frequency, and wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating a real normal modal residual flexibility component at the excitation frequency.

20. A method according to claim 19, wherein the real normal mode comprises a real normal mode having a resonant frequency apart from the excitation frequency.

21. A method according to claim 20:

wherein said step of determining a first value comprises the step of determining a first plurality of values at a plurality of selected frequencies near the resonant frequency of the real normal mode; and

wherein said step estimating a real normal modal residual flexibility component comprises the step of estimating a real normal modal residual flexibility component associated with the real normal mode by fitting the first plurality of values to the identified function.

22. A method according to claim 14, wherein said step of determining a first value comprises the steps of:

receiving a plurality of motion signals representing motion of the conduit under a unknown mass flow condition; and

determining the first value from the received plurality of motion signals representing motion of the conduit under the unknown mass flow condition.

23. A method according to claim 14:

wherein said step of determining a first value comprises the step of determining a first value representing real normal modal motion in the real normal mode; and

wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating residual real normal modal motion in the real normal mode.

24. A method according to claim 23, wherein said step of generating a residual-flexibility-compensated estimate comprises the steps of:

processing the received plurality of motion signals to estimate real normal modal motion of the conduit as a material flows therethrough; and

generating a residual-flexibility-compensated estimate of mass flow from the estimated real normal modal motion and the estimated residual real normal modal motion.

25. A method according to claim 17:

wherein said step of identifying a function comprises the step of identifying a plurality of functions;

wherein said step of determining a first value comprises the step of generating a first matrix of values representing real normal modal motion in the real normal mode at a plurality of selected frequencies;

wherein said step of evaluating comprises the step of generating a second matrix of values of the identified function evaluated at the plurality of selected frequencies; and

wherein said step of estimating residual real normal modal motion comprises the step of evaluating a real normal modal motion vector at a selected frequency from a product of the first matrix, the second matrix and a vector of values representing the plurality of identified functions evaluated at the selected frequency.

26. A method according to claim 16:

wherein said step of determining a first value comprises the step of determining a first plurality of values representing motion of the conduit at a plurality of selected frequencies;

wherein said step of evaluating comprises the step of evaluating the identified function at the plurality of selected frequencies to generate a second plurality of values; and

wherein said step of estimating a real normal modal residual flexibility component comprises the step of estimating residual physical motion associated with the real normal mode from the first plurality of values, the second plurality of values and the identified function.

27. A method according to claim 26, wherein said step of generating a residual-flexibility-compensated estimate comprises the step of:

mode pass filtering the received plurality of motion signals to produce a mode-pass filtered representation of motion of the conduit as a material flows therethrough; and

generating a residual-flexibility-compensated estimate of mass flow from the mode pass filtered representation and the estimated residual physical motion.

28. An apparatus for estimating a process parameter associated with a material contained in a vibrating conduit, the apparatus comprising:

a real normal modal residual flexibility component estimator configured to receive motion signals representing motion of the conduit and operative to estimate a real normal modal residual flexibility component associated with a real normal mode of motion of the conduit therefrom; and

a residual-flexibility-compensated mass flow estimator responsive to said real normal modal residual flexibility component estimator, configured to receive motion signals representing motion of the conduit and operative to generate a residual-flexibility-compensated estimate of mass flow therefrom according to estimated real normal modal residual flexibility component.

29. An apparatus according to claim 28, and:

wherein said real normal modal residual flexibility component estimator comprises means for estimating a real normal modal residual flexibility component of the conduit associated with the real normal mode at an excitation frequency; and

wherein said residual-flexibility-compensated mass flow estimator comprises;

means for determining motion of the conduit at the excitation frequency from a plurality of motion signals representing motion of the conduit responsive to an excitation at the excitation frequency; and

means, responsive to said means for determining motion, for generating a residual-flexibility-compensated estimate of mass flow from the determined motion and the estimated real normal modal residual flexibility component.

30. An apparatus according to claim 29, wherein said real normal modal residual flexibility component estimator comprises:

means, responsive to a plurality of motion signals representing motion of the conduit under a substantially zero mass flow condition, for resolving motion of the conduit at the excitation frequency under the substantially zero mass flow condition into a plurality of real normal modal components associated with a plurality of real normal modes; and

means, responsive to said resolving means, for estimating a real normal modal residual flexibility component of the conduit motion associated with a real normal mode of the plurality of real normal modes from the resolved plurality of real normal modal components.

31. An apparatus according to claim 29, wherein a real normal modal residual flexibility component estimator comprises:

means for identifying a function that describes motion of the conduit in a real normal mode as a function of frequency;

means, responsive to a plurality of motion signals representing motion of the conduit, for determining motion of the conduit at a selected frequency; and

means, responsive to said means for determining motion of the conduit at a selected frequency and to said function identifying means, for estimating a real normal modal residual flexibility component at the excitation frequency associated with the real normal mode by fitting the determined motion at the selected frequency to the identified function.

32. An apparatus according to claim 31, wherein said real normal residual flexibility component estimating means comprises:

means for determining a scaling transformation that relates the determined motion to the identified function; and

means, responsive to said scaling transformation determining means, for estimating a real normal modal residual flexibility component at the excitation frequency from the determined scaling transformation.

33. An apparatus for estimating a process parameter associated with a material contained in a conduit, the apparatus comprising:

a real normal modal residual flexibility component estimator, responsive to a first plurality of motion signals representing motion of the conduit under a substantially zero mass flow condition, for processing the first plurality of motion signals to estimate a real normal modal residual flexibility component associated with a real normal mode of motion of the conduit; and

a residual-flexibility-compensated mass flow estimator, responsive to a second plurality of motion signals representing motion of the conduit, for generating a residual-flexibility-compensated estimate of mass flow from the second plurality of motion signals and the first estimated real normal modal residual flexibility component.

34. An apparatus according to claim 33, wherein said real normal modal residual flexibility component estimator comprises a mode pass filter operative to filter the first plurality of motion signals to produce a mode pass filtered representation of the conduit motion under the substantially zero mass flow condition.

35. An apparatus according to claim 34:

wherein said real normal modal residual flexibility component estimator comprises;

means for estimating real normal modal motion under the substantially zero mass flow condition from the first plurality of motion signals; and

means for estimating residual real normal modal motion from the estimated real normal modal motion under the substantially zero mass flow condition; and

wherein said residual-flexibility-compensated mass flow estimator comprises;

means for estimating real normal modal motion from the second plurality of motion signals; and

means for generating a residual-flexibility-compensated estimate of mass flow under the unknown mass flow condition from the estimated residual real normal modal motion and the estimated real normal modal motion.

36. An apparatus according to claim 33, further comprising means for estimating a second real normal modal residual flexibility component associated with a second real normal mode of conduit motion under a non-zero mass flow condition;

and

wherein said residual-flexibility-compensated mass flow estimator comprises means for generating a residual-flexibility-compensated estimate of mass flow from the received second plurality of motion signals, the estimated first real normal modal residual flexibility component and the estimated second real normal modal residual flexibility component.

37. An apparatus according to claim 36, wherein the first real normal mode is more highly correlated with flow of material in the conduit than the second real normal mode.

38. An apparatus according to claim 36, wherein said means for estimating a second real normal modal residual flexibility component comprises means for processing a third plurality of motion signals representing motion of the conduit under a non-zero mass flow condition to estimate the second real normal modal residual flexibility component.

39. An apparatus according to claim 36, wherein said means for estimating a second real normal modal residual flexibility component comprises:

means for identifying a function describing motion in the second real normal mode as a function of frequency; and

means for estimating the second real normal modal residual flexibility component from the identified function.

40. An apparatus according to claim 36:

wherein said means for estimating a second real normal modal residual flexibility component comprises means for generating a first estimate of the second real normal modal residual flexibility component;

wherein said residual-flexibility-compensated mass flow estimator comprises means for generating a first residual-flexibility-compensated estimate of mass flow from the first estimate of the second real normal modal residual flexibility component;

wherein said means for estimating a second real normal modal residual flexibility component further comprises means for generating a second estimate of the second real normal modal residual flexibility component; and

wherein said residual-flexibility-compensated mass flow estimator further comprises means for generating a second residual-flexibility-compensated estimate of mass flow from the second estimate of the second real normal modal residual flexibility component.

41. An apparatus for estimating a process parameter from motion signals representing motion of a vibrating conduit containing a material, the apparatus comprising:

a real normal modal residual flexibility component estimator including;

means for identifying a function operative to describe motion of the conduit in a real normal mode as function of frequency;

means, responsive to a plurality of motion signals representing motion of the conduit, for determining a first value representing motion of the vibrating conduit at a selected frequency; and

means, responsive to said function identifying means and to said means for determining a first value, for estimating a real normal modal residual flexibility component associated with the real normal mode by fitting the first value to the identified function; and

a residual-flexibility-compensated mass flow estimator, responsive to said real normal modal residual flexibility component estimator, for generating a residual-flexibility-compensated estimate of mass flow from the received second plurality of motion signals and the estimated real normal modal residual flexibility component.

42. An apparatus according to claim 41, wherein said step a real normal modal residual flexibility component estimator comprises:

means for determining a scaling transformation relating the first value to the identified function; and

means for estimating a real normal modal residual flexibility component associated with the real normal mode from the identified function and the determined scaling transformation.

43. An apparatus according to claim 42, wherein said means for determining a scaling transformation comprises:

means for evaluating the identified function at the selected frequency to generate a second value; and

means for determining a scaling transformation relating the first value to the identified function from the first value and the second value.

44. An apparatus according to claim 43:

wherein said step of determining a first value comprises the step of determining a first plurality of values at a plurality of selected frequencies;

wherein said means for evaluating comprises means for evaluating the identified function at the plurality of selected frequencies to generate a second plurality of values; and

wherein means for determining a scaling transformation comprises means for determining a scaling transformation from the first plurality of values and the second plurality of values.

45. An apparatus according to claim 41, wherein the real normal mode comprises a real normal mode substantially correlated with mass flow.

46. An apparatus claim 41, wherein said real normal modal residual flexibility component estimating means comprises means for estimating a real normal modal residual flexibility component at an excitation frequency responsive to excitation of the conduit at the excitation frequency.

47. An apparatus according to claim 46, wherein the real normal mode comprises a real normal mode having a resonant frequency apart from the excitation frequency.

48. An apparatus according to claim 47:

wherein said means for determining a first value comprises means for determining a first plurality of values at a plurality of selected frequencies near the resonant frequency of the real normal mode; and

wherein said means for estimating a real normal modal residual flexibility component comprises means for estimating a real normal modal residual flexibility component associated with the real normal mode by fitting the first plurality of values to the identified function.

49. An apparatus according to claim 41, wherein said means for determining a first value comprises means for determining the first value from a plurality of motion signals representing motion of the conduit under a unknown mass flow condition.

50. An apparatus according to claim 41:

wherein said means for determining a first value comprises means for determining a first value representing real normal modal motion in the real normal mode; and

wherein said step of means for estimating a real normal modal residual flexibility component comprises means for estimating residual real normal modal motion in the real normal mode.

51. An apparatus according to claim 50, wherein said residual-flexibility-compensated mass flow estimator comprises:

means for processing a plurality of motion signals to estimate real normal modal motion of the conduit as a material flows therethrough; and

means for generating a residual-flexibility-compensated estimate of mass flow from the estimated real normal modal motion and the estimated residual real normal modal motion.

52. An apparatus according to claim 44:

wherein said means for identifying a function comprises means for identifying a plurality of functions;

wherein said means for determining a first value comprises means for generating a first matrix of values representing real normal modal motion in the real normal mode at a plurality of selected frequencies;

wherein said means for evaluating comprises means for generating a second matrix of values of the identified function evaluated at the plurality of selected frequencies; and

wherein said means for estimating residual real normal modal motion comprises means for evaluating a real normal modal motion vector at a selected frequency from a product of the first matrix, the second matrix and a vector of values representing the plurality of identified functions evaluated at the selected frequency.

53. An apparatus according to claim 43:

wherein said means for determining a first value comprises means for determining a first plurality of values representing motion of the conduit at a plurality of selected frequencies;

wherein said means for evaluating comprises means for evaluating the identified function at the plurality of selected frequencies to generate a second plurality of values; and

wherein said means for estimating a real normal modal residual flexibility component comprises means for estimating residual physical motion associated with the real normal mode from the first plurality of values, the second plurality of values and the identified function.

54. An apparatus according to claim 53, wherein said residual-flexibility-compensated mass flow estimator comprises:

a mode pass filter operative to filter a plurality of motion signals to produce a mode-pass filtered representation of motion of the conduit as a material flows therethrough; and

means for generating a residual-flexibility-compensated estimate of mass flow from the mode pass filtered representation and the estimated residual physical motion.

55. A computer program product for estimating a process parameter associated with a material contained in a conduit, the computer program product comprising:

a computer readable storage medium having computer readable program code means embodied in said medium, said computer readable program code means comprising;

first computer-readable program code means for storing motion signals representing motion of the conduit;

second computer-readable program code means, responsive to said first computer-readable program code means, for estimating a real normal modal residual flexibility component associated with a real normal mode of motion of the conduit; and

third computer-readable program code means, response to said first computer-readable program code means and to said second computer-readable program code means, for generating a residual-flexibility-compensated estimate of mass flow from stored motion signals and the estimated real normal modal residual flexibility component.

56. A computer program product according to claim 55:

wherein said second computer-readable program code means comprises computer-readable program code means for estimating a real normal modal residual flexibility component associated with the real normal mode at an excitation frequency; and

wherein said third computer-readable program code means comprises;

computer-readable program code means for determining motion of the conduit at the excitation frequency from stored motion signals; and

computer-readable program code means for generating a residual-flexibility-compensated estimate of mass flow from the determined motion at the excitation frequency and the estimated real normal modal residual flexibility component.

57. A computer program product according to claim 56, wherein said second computer-readable program code means comprises:

computer-readable program code means, responsive to stored motion signals representing conduit motion under a substantially zero mass flow condition, for resolving motion of the conduit at the excitation frequency under the substantially zero mass flow condition into a plurality of real normal modal components associated with a plurality of real normal modes; and

computer-readable program code means for estimating a real normal modal residual flexibility component of the conduit motion associated with a mode of the plurality of real modes from the resolved plurality of real normal modal components.

58. A computer program product according to claim 56, wherein said second computer-readable program code means comprises:

computer-readable program code means for identifying a function that describes motion of the conduit in a real normal mode as a function of frequency;

computer-readable program code means for determining motion of the conduit at a selected frequency; and

computer-readable program code means for estimating a real normal modal residual flexibility component at the excitation frequency associated with the real normal mode by fitting the determined motion at the selected frequency to the identified function.

59. A computer program product according to claim 56, wherein said second computer-readable program code means comprises:

computer-readable program code means for determining a scaling transformation that relates the determined motion to the identified function; and

computer-readable program code means for estimating a real normal modal residual flexibility component at the excitation frequency from the determined scaling transformation.