Initialization algorithm for drive control in a coriolis flowmeter

• US 6,505,135 B2
• Filed: 03/13/2001
• Issued: 01/07/2003
• Est. Priority Date: 03/13/2001
• Status: Active Grant

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Maginnis, Richard L.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US09/805,271
• Publication Number:
  US 20020133307A1
• Time in Patent Office: 665 Days
• Field of Search: 702/100, 702/45, 702/54, 702/194, 738/613.56, 738/613.54, 738/613.55, 738/613.57
• US Class Current: 702/100
• CPC Class Codes: G01F 1/8418 motion or vibration balancing means
• CPC Class Codes: G01F 1/8436 signal processing
• CPC Class Codes: G01F 1/8477 with multiple measuring conduits
• CPC Class Codes: G01F 1/849 having straight measuring conduits

Abstract

A system for initializing parameters in a drive circuit. This invention applies initial drive signals to a drive circuit which causes said flow tube to vibrate. The configuration of the flow tube is then determined from pick-off signals received from pick-off sensors associated with the flow tube. Parameters for generation of said drive signals are then set based upon the configuration of said flow tube.

Claims

1. A method for initializing a drive circuit which generates drive signals that are applied to a driver that is oscillating a flow tube, said method comprising the steps of:

applying said drive signals to said driver at a predetermined gain to initiate vibrating of said flow tube;

controlling a drive voltage of said drive signals applied to said driver to maintain a velocity of pick-off signals received from pick-off sensors associated with said flow tube;

determining whether a notch filter has converged on a drive frequency of said flow tube based on said pick-off signals; and

controlling said drive voltage of said drive signals applied to said driver to maintain a displacement of said flow tube in response to a determination that said notch filter has converged on said drive frequency.

2. The method of claim 1 further comprising the step of:

receiving said pick-off signals from said pick-off sensors.

3. The method of claim 2 further comprising the step of:

determining said drive frequency of said flow tube based on said pick-off signals.

4. The method of claim 3 wherein said step of determining said drive frequency comprises the steps of:

comparing said drive frequency to a threshold frequency; and

determining said flow tube is a straight tube responsive to said drive frequency being greater than said threshold frequency.

5. The method of claim 4 wherein said step of determining said drive frequency further comprises the step of:

determining said flow tube is a curved flow tube responsive to said drive frequency being less than or equal to said threshold frequency.

6. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

setting at least one variable for use in generating said drive signals.

7. The method of claim 6 wherein said step of setting said at least one variable comprises the step of:

setting a pick-off amplitude.

8. The method of claim 7 wherein said pick-off amplitude is set to a desired voltage.

9. The method of claim 6 wherein said step of setting said at least one variable comprises the step of:

setting a flow tube period.

10. The method of claim 6 wherein said step of setting said at least one variable comprises the step of:

setting a desired drive target.

11. The method of claim 10 wherein said desired drive target is set to a target voltage divided by a target.

12. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

setting a kick gain signal to off.

13. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

setting a programable gain amplifier to unity gain.

14. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

initializing flags.

15. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

initializing a timer.

16. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

initializing a notch filter.

17. The method of claim 1 wherein said step of determining whether said notch filter has converged comprises the steps of:

determining whether a timer has reached a time out; and

returning to said step of applying drive signals to said driver in response to a determination said timer has reached said time out.

18. The method of claim 1 wherein said step of controlling said drive voltage of said drive signals to maintain said displacement further comprises the step of:

determining flowmeter parameters in response to a determination that said notch filter has converged to said drive frequency.

19. The method of claim 1 further comprising the steps of:

determining whether said notch filter has converged to a notch filter value that is within a desired range; and

returning to said step of applying drive signals to said driver responsive to a determination that said notch filter value is outside said desired range.

20. The method of claim 19 wherein said step of determining whether said notch filter value is within said desired range comprises the step of:

comparing said notch filter value to a minimum value.

21. The method of claim 20 wherein said minimum value is 30 hertz.

22. The method of claim 19 wherein said step of determining whether said notch filter value is within said desired range comprises the step of:

comparing said notch filter value to a maximum value.

23. The method of claim 22 wherein said maximum value is 900 hertz.

24. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

setting amplitudes of said drive signals to initial amplitudes.

25. The method of claim 24 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

setting an initial application time of said drive signals.

26. The method of claim 25 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

applying said drive signals to said driver for a duration of said application time.

27. The method of claim 26 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

determining whether amplitudes of said pick-off signals are sufficient for said notch filter.

28. The method of claim 27 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

adjusting said amplitudes of said drive signals in response to a determination that said amplitudes of said pick-off signals are not sufficient for said notch filter.

29. The method of claim 28 wherein said step of adjusting said amplitudes of said drive signals comprises the step of:

increasing a multiplying digital to analog conversion by two.

30. The method of claim 29 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

adjusting said application time in response to a determination that said amplitudes of said drive signals are not sufficient.

31. The method of claim 30 wherein said step of adjusting said application time comprises the step of:

increasing said application time by ten milliseconds.

32. The method of claim 31 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the steps of:

waiting a delay period; and

applying said drive signals using said adjusted amplitudes of said drive signals and said adjusted application time in response to waiting said delay period.

33. The method of claim 1 wherein said step of applying said drive signals to said driver to initiate vibrating of said flow tube comprises the step of:

determining whether a timer has reached a time out; and

repeating said step of applying said drive signals to said driver in response to a determination that said timer has reached said time out.

34. The method of claim 1 wherein said step of controlling said drive voltage of said drive signals applied to said driver to maintain said velocity comprises maintaining said velocity at least at 50 millivolts.

35. The method of claim 1 further comprising the step of:

determining flowmeter sensor parameters in response to a determination said notch filter has converged upon said drive frequency.

36. The method of claim 35 wherein said step of determining said flowmeter sensor parameters comprises the step of:

determining a proportional gain of said drive signals applied to said driver.

37. The method of claim 35 wherein said step of determining said flowmeter sensor parameters comprises the step of:

determining a integral gain of said drive signals applied to said driver.

38. The method of claim 1 wherein said step of controlling said drive voltage of said drive signals applied to said driver to maintain said displacement comprises the step of:

testing to determine whether a drive loop gain is locked.

39. The method of claim 38 wherein said step of testing to determine whether a drive loop gain is locked comprises the step of:

determining drive error from said pick-off signals received from said pick-off sensors associated with said flow tube.

40. The method of claim 39 wherein said step of testing to determine whether a drive loop gain is locked further comprises the step of:

determining whether said drive error has converged to zero.

41. The method of claim 38 wherein said step of testing to determine whether a drive loop gain is locked comprises the steps of:

determining whether a timer has reached a time out; and

repeating said step of applying said drive signals to said driver responsive to said timer reaching said time out.

42. The method of claim 38 wherein said step of testing to determine whether a drive loop gain is locked further comprises:

repeating said step of applying said drive signals to said driver responsive to a determination said drive loop gain is not locked.

43. The method of claim 1 wherein said step of controlling said drive voltage of said drive signals applied to said driver to maintain said displacement comprises the steps of:

setting a programmable gain amplitude;

generating said drive signals to maintain an amplitude of said pick-off signals from said pick-off sensors associated with said flow tube;

determining whether said amplitude of said pick-off signals is maintained; and

performing a forgive process in response to said amplitude of said pick-off signals not being maintained.

44. The method of claim 43 wherein said step of controlling said drive voltage of said drive signals applied to said driver to maintain a displacement further comprises the step of:

delaying measurements of said pick-off signals for a predetermined amount of time to account for transients.

45. The method of claim 43 wherein said step of performing said forgive process comprises the steps of:

holding a last delta time calculation;

determining whether said amplitude of said pick-off signals returns to said maintained amplitude in a given amount of time; and

repeating said step of applying said driver signals to said driver in response to a determination that said amplitude of said pick-off signals did not return to said maintained amplitude of said pick-off signals in said given amount of time.

46. An apparatus for measuring a process parameter of a material having a flow tube through which said material flows, a driver that vibrates said flow tube, pick-off sensors associated with said flow tube to measure said vibrations, and meter electronics that generate drive signals transmitted to said driver to vibrate said flow tube and that receives pick-off signals from said pick-off sensors, said apparatus further comprising:

circuitry in said meter electronics configured to;

a.) apply said drive signals to said driver at a predetermined gain to initiate vibrating of said flow tube;

b.) control a drive voltage of said drive signals applied to said driver to maintain a velocity of said pick-off signals received from said pick-off sensors;

c.) determine whether a notch filter has converged to a drive frequency of said flow tube based on said pick-off signals; and

d.) control said drive voltage of said drive signals applied to said driver to maintain a displacement of said flow tube in response to a determination that said notch filter has converged on said drive frequency.

47. The apparatus of claim 46 further comprising:

circuitry in said meter electronics configured to receive said pick-off signals from said pick-off sensors.

48. The apparatus of claim 47 further comprising:

circuitry in said meter electronics configured to determine said drive frequency of said flow tube based on said pick-off signals.

49. The apparatus of claim 48 wherein said circuitry is configured to:

compare said drive frequency to a threshold frequency, and determine said flow tube is a straight tube responsive to said drive frequency being greater than said threshold frequency.

50. The apparatus of claim 49 wherein said circuitry is configured to:

determine said flow tube is a curved flow tube responsive to said drive frequency being less than or equal to said threshold frequency.

51. The apparatus of claim 46 wherein said circuitry is configured to:

set at least one variable for use in generating said drive signals.

52. The apparatus of claim 51 wherein said circuitry is configured to:

set a pick-off amplitude.

53. The apparatus of claim 52 wherein said pick-off amplitude is set to a desired voltage.

54. The apparatus of claim 51 wherein said circuitry is configured to:

set a flow tube period.

55. The apparatus of claim 51 wherein said circuitry is configured to:

set a desired drive target.

56. The apparatus of claim 55 wherein said desired drive target is set to a target voltage divided by a target frequency.

57. The apparatus of claim 46 wherein said circuitry is configured to:

set a kick gain signal to off.

58. The apparatus of claim 46 wherein said circuitry is configured to:

set a programable gain amplifier to unity gain.

59. The apparatus of claim 46 wherein said circuitry is configured to:

initialize flags.

60. The apparatus of claim 46 wherein said circuitry is configured to:

initialize a timer.

61. The apparatus of claim 46 wherein said circuitry is configured to:

initialize a notch filter.

62. The apparatus of claim 46 wherein said circuitry is configured to:

determine whether a timer has reached a time out, and return to operation a.) in response to a determination said timer has reached said time out.

63. The apparatus of claim 46 wherein said circuitry is configured to:

determine flowmeter parameters in response to a determination that said notch filter has converged to said drive frequency.

64. The apparatus of claim 46 wherein said circuitry further comprises:

circuitry in said meter electronics configured to determine whether said notch filter has converged to a notch filter value that is within a desired range, and return to operation a.) responsive to a determination that said notch filter value is outside said desired range.

65. The apparatus of claim 64 wherein said circuitry is configured to:

compare said notch filter value to a minimum value.

66. The apparatus of claim 65 wherein said minimum value is 30 hertz.

67. The apparatus of claim 64 wherein said circuitry is configured to:

compare said notch filter value to a maximum value.

68. The apparatus of claim 67 wherein said maximum value is 900 hertz.

69. The apparatus of claim 46 wherein said circuitry is configured to:

set amplitudes of said drive signals to initial amplitudes.

70. The apparatus of claim 69 wherein said circuitry is configured to:

set an initial application time of said drive signals.

71. The apparatus of claim 70 wherein said circuitry is configured to:

apply said drive signals to said driver for a duration of said application time.

72. The apparatus of claim 71 wherein said circuitry is configured to:

determine whether amplitudes of said pick-off signals are sufficient for said notch filter.

73. The apparatus of claim 72 wherein said circuitry is configured to:

adjust said amplitudes of said drive signals in response to a determination that said amplitudes of said pick-off signals are not sufficient for said notch filter.

74. The apparatus of claim 73 wherein said circuitry is configured to:

increase a multiplying digital to analog conversion by two.

75. The apparatus of claim 74 wherein said circuitry is configured to:

adjust said application time in response to a determination that said amplitudes of said drive signals are not sufficient.

76. The apparatus of claim 75 wherein said circuitry is configured to:

increase said application time by ten milliseconds.

77. The apparatus of claim 76 wherein said circuitry is configured to:

wait a delay period and apply said drive signals using said adjusted amplitude of said drive signals and said adjusted application time in response to waiting said delay period.

78. The apparatus of claim 46 wherein said circuitry is configured to:

determine whether a timer has reached a time out, and restart operation a.) in response to a determination that said timer has reached said time out.

79. The apparatus of claim 46 wherein circuitry is configured to maintain said velocity to at least at 50 millivolts.

80. The apparatus of claim 46 wherein said circuitry is configured to:

determine flowmeter sensor parameters in response to a determination said notch filter has converged upon said drive frequency.

81. The apparatus of claim 80 wherein said is circuitry configured to:

determine a proportional gain of said drive signals applied to said driver.

82. The apparatus of claim 80 wherein said circuitry is configured to:

determine an integral gain of said drive signals applied to said driver.

83. The apparatus of claim 46 wherein said circuitry is configured to:

perform a test to determine whether a drive loop gain is locked.

84. The apparatus of claim 83 wherein said circuitry is configured to:

determine drive error from said pick-off signals received from said pick-off sensors associated with said flow tube.

85. The apparatus of claim 84 wherein said circuitry is configured to:

determine whether said drive error has converged to zero.

86. The apparatus of claim 83 wherein said circuitry is configured to:

determine whether a timer has reached time out, and repeat operation a.) responsive to said timer reaching said time out.

87. The apparatus of claim 83 wherein said circuitry is configured to:

repeat operation a.) responsive to a determination said drive loop gain is not locked.

88. The apparatus of claim 46 wherein said circuitry is configured to:

set a programmable gain amplitude, generate said drive signals to maintain an amplitude of said pick-off signals from said pick-off sensors associated with said flow tube, determine whether said amplitude of said pick-off signals is maintained, and perform a forgive process in response to said amplitude of said pick-off signals not being maintained.

89. The apparatus of claim 88 wherein said circuitry is configured to:

delay measurements of said pick-off signals for a predetermined amount of time to account for transients.

90. The apparatus of claim 88 wherein said circuitry is configured to:

determine whether said amplitude of said pick-off signals returns to said maintained amplitude in a given amount of time, and repeat operation a.) in response to a determination that said amplitude did not return to said maintained amplitude of said pick-off signals in said given amount of time.