Method for recording and removing the bipolar bias from a vibration input signal

• US 6,546,361 B2
• Filed: 01/12/2001
• Issued: 04/08/2003
• Est. Priority Date: 01/12/2001
• Status: Active Grant

• Current Assignee: ABB Automation GmbH (ABB Limited)
• Original Assignee: ABB Automation GmbH (ABB Limited)
• Inventors: Di Tommaso, Anthony M., Ye, Ren-Chao
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): West, Jeffrey R
• Application Number:
  US09/759,928
• Publication Number:
  US 20020095272A1
• Time in Patent Office: 816 Days
• Field of Search: 702/66, 702/69, 702/70, 702/74, 702/75, 702/78, 702/79, 702/106, 702/107, 702/189, 702/193-195, 702/199, 736/45--48, 327/76, 327/307, 341/7, 341/8, 341/15
• US Class Current: 702/189
• CPC Class Codes: H03H 21/0001 Analogue adaptive filters
• CPC Class Codes: H03H 21/0043 Adaptive algorithms

Abstract

A method for recording and removing the bipolar bias from a vibration input signal. The signal is a time varying signal where the bipolar bias has an amplitude which is many times greater than the amplitude of the time varying waveform of the signal that represents the vibration of the machine. In calculating the level of the bipolar bias the method approaches a predetermined dead band asymptotically and in stable manner. The determination of the bipolar bias level occurs when the next event has occurred and the time for that determination is much shorter than the time between occurrence of the events.

Claims

1. A method for removing the bipolar bias level from a periodic time varying signal and recording the level thereof comprising:

a) firstly determining upon the occurrence of a new event if the maximum amplitude of a collection of samples observed between events is equal to a predetermined positive saturation level and multiplying said predetermined positive saturation level by a negative constant, which is less than one, when said first determination is true to determine a first bias level compensation value;

b) secondly determining, when said first determination is not true, if the minimum amplitude of said collection of samples observed between events is equal to a predetermined negative saturation level and multiplying said predetermined negative saturation level by said negative constant when said second determination is true to determine a second bias level compensation value;

c) thirdly determining, if both said first and second determinations are not true, the average of said maximum and minimum amplitudes of said collection of samples observed between events and multiplying said average by said negative constant when said average is not within a predetermined range of amplitude values to determine a third bias level compensation value; and

d) adding said first or said second or said third bias level compensation value to a value for said bipolar bias level previously accumulated during the occurrence of said event occurring just prior in time to said new event occurrence.

2. The method of claim 1 further comprising adding a bias level compensation value of zero to said value for said previously accumulated bipolar bias level when said average is within said predetermined range of amplitude values.

3. An apparatus for removing the bipolar bias level from a periodic time varying signal and recording the level thereof comprising:

an analog to digital converter having a predetermined sampling rate for converting said time varying signal to digital samples;

a digital signal processor for;

a) firstly determining upon the occurrence of a new event if the maximum amplitude of a collection of said digital samples observed between events is equal to a predetermined positive saturation level and multiplying said predetermined positive saturation level by a negative constant, which is less than one, when said first determination is true to determine a first bias level compensation value;

b) secondly determining, when said first determination is not true, if the minimum amplitude of said collection of digital samples observed between events is equal to a predetermined negative saturation level and multiplying said predetermined negative saturation level by said negative constant when said second determination is true to determine a second bias level compensation value;

c) thirdly determining, if both said first and second determinations are not true, the average of said maximum and minimum amplitudes of said collection of digital samples observed between events and multiplying said average by said negative constant when said average is not within a predetermined range of amplitude values to determine a third bias level compensation value; and

d) adding said first or said second or said third bias level compensation value to a value for said bipolar bias level previously accumulated during the occurrence of said event occurring just prior in time to said new event occurrence.

4. The apparatus of claim 3 wherein said digital signal processor further adds a bias level compensation value of zero to said value for said previously accumulated bipolar bias level when said average is within said predetermined range of amplitude values.

5. An apparatus for removing the bipolar bias level from a periodic time varying signal and recording the level thereof comprising:

an analog to digital converter having a predetermined sampling rate for converting said time varying signal to digital samples;

a digital signal processor for;

(i) determining if a new digital sample has arrived at the input of said digital signal processor;

(ii) determining from the amplitude of said new digital sample if either positive or negative saturation has occurred at said digital signal processor input and, when positive saturation has occurred, replacing the stored maximum amplitude for samples occurring prior to the occurrence of said new digital sample with said new sample amplitude and, when negative saturation has occurred, replacing the stored minimum amplitude for samples occurring prior to the occurrence of said new digital sample with said new sample amplitude;

(iii) low pass digitally filtering said new digital sample;

(iv) determining from the amplitude of said digitally filtered new digital sample if the positive or negative amplitude is greater or less than the stored maximum amplitude or stored minimum amplitude for samples occurring prior to the occurrence of said new digital sample and replacing either said stored maximum amplitude, when said digitally filtered new digital sample amplitude is greater than said stored maximum amplitude, or said stored minimum amplitude, when said digitally filtered new digital sample amplitude is less than said stored minimum amplitude; and

(v) determining if a new event has occurred and upon the occurrence thereof firstly determining if the maximum amplitude stored during the determining from the amplitude of a new digital sample if positive saturation has occurred is equal to a predetermined positive saturation level and multiplying said predetermined positive saturation level by a negative constant, which is less than one, when said first determination is true to determine a first bias level compensation value.

6. The apparatus of claim 5 wherein said digital signal processor secondly determines, when said first determination is not true, if the minimum amplitude stored during the determining from the amplitude of a new digital sample if negative saturation has occurred is equal to a predetermined negative saturation level and multiplying said predetermined negative saturation level by said negative constant when said second determination is true to determine a second bias level compensation value.

7. The apparatus of claim 6 wherein said digital signal processor thirdly determines, if both said first and second determinations are not true, the average of said maximum and minimum amplitudes stored during the determining if positive or negative saturation has occurred and multiplying said average by said negative constant when said average is not within said a predetermined range of amplitude values to determine a third bias level compensation value.

8. The apparatus of claim 7 wherein said digital signal processor adds said first or said second or said third bias level compensation value to a value for said bipolar bias level previously accumulated during the occurrence of said event occurring just prior in time to said new event occurrence.

9. A method for removing the bipolar bias level from a periodic time varying signal and recording the level thereof comprising:

(a) determining from the amplitude of a new digital sample of said time varying signal if either positive or negative saturation has occurred at the input of a digital signal processor and, when positive saturation has occurred, replacing the stored maximum amplitude for samples occurring prior to the occurrence of said new digital sample with said new sample amplitude and, when negative saturation has occurred, replacing the stored minimum amplitude for samples occurring prior to the occurrence of said new digital sample with said new sample amplitude;

(b) low pass digitally filtering said new digital sample;

(c) determining from the amplitude of said digitally filtered new digital sample if the positive or negative amplitude is greater or less than the stored maximum amplitude or stored minimum amplitude for samples occurring prior to the occurrence of said new digital sample and replacing either said stored maximum amplitudes, when said digitally filtered new digital sample amplitude is greater than said stored maximum amplitude or said stored minimum amplitude, when said digitally filtered new digital sample amplitude is less than said stored minimum amplitude; and

(d) determining if a new event has occurred and upon the occurrence thereof firstly determining if the maximum amplitude stored during the determining from the amplitude of a new digital sample if positive saturation has occurred is equal to a predetermined positive saturation level and multiplying said predetermined positive saturation level by a negative constant, which is less than one, when said first determination is true to determine a first bias level compensation value.

10. The method of claim 9 further comprising secondly determining, when said first determination is not true, if the minimum amplitude stored during the determining from the amplitude of a new digital sample if negative saturation has occurred is equal to a predetermined negative saturation level and multiplying said predetermined negative saturation level by said negative constant when said second determination is true to determine a second bias level compensation value.

11. The method of claim 10 further comprising thirdly determining, if both said first and second determinations are not true, the average of said maximum and minimum amplitudes stored during the determining if positive or negative saturation has occurred and multiplying said average by said negative constant when said average is not within said a predetermined range of amplitude values to determine a third bias level compensation value.

12. The method of claim 11 further comprising adding said first or said second or said third bias level compensation value to a value for said bipolar bias level previously accumulated during the occurrence of said event occurring just prior in time to said new event occurrence.