Anomaly detector for vibratory angular rate sensor

• US 20060077013A1
• Filed: 10/07/2005
• Published: 04/13/2006
• Est. Priority Date: 10/08/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ito, Hajime, Mase, Shunji, Tsuruhara, Takao
• Granted Patent: US 7,292,021 B2
• Time in Patent Office: Days
• US Class Current: 331/74
• CPC Class Codes: G01C 19/5649 Signal processing

Abstract

In an anomaly detector that detects an abnormal condition of an oscillation signal of a circuit such as a vibratory sensing circuit, the oscillation signal, having AC and DC components, is converted to a pair of first and second signals of either opposite-polarity DC amplitudes or opposite-phase alternating amplitudes. The first and second signals are combined to cancel the AC component of the oscillation signal to detect the DC component. The DC component is then compared with the upper and lower thresholds of a decision range to produce an alarm if the DC component goes outside the decision range. In one embodiment, the first and second signals are produced by detecting positive and negative peak values of the oscillation signal at intervals. In a second embodiment, the first signal is produced by high-pass filtering the oscillation signal as a replica of the AC component and the second signal is the oscillation signal itself.

Claims

1. An anomaly detector for detecting a DC component of an oscillation signal, comprising:

a DC component detector that detects a DC component of said oscillation signal, said detector including no timing delay element that introduces a delay in detecting said DC component; and

a window comparator, associated with said detector, that determines whether the detected DC component is within a predetermined range.

2. The anomaly detector of claim 1, wherein the DC component detector produces, from said oscillation signal, a pair of first and second signals having amplitudes of opposite polarities so that at least one of said first and second signals contains said DC component of the oscillation signal, and combines said first and second signals to detect said DC component by mutually canceling said amplitudes of opposite polarities.

3. The anomaly detector of claim 2, wherein said first signal is a DC amplitude of first polarity containing said DC component, and said second signal is a DC amplitude of second polarity containing said DC component, said second polarity being opposite to said first polarity.

4. The anomaly detector of claim 2, wherein said first signal is alternating amplitudes of first phase, and said second signal is alternating amplitudes of second phase opposite to said first phase, one of said first and second signals containing said DC component of the oscillation signal.

5. The anomaly detector of claim 2, wherein said DC component detector comprises:

a maximum detector that detects a positive peak value of said oscillation signal at periodic intervals; and

a minimum detector that detects a negative peak value of said oscillation signal at said periodic intervals synchronously with said maximum detector.

6. The anomaly detector of claim 5, wherein said positive peak value is equal to a positive amplitude of said oscillation signal plus said DC component and said negative peak value is equal to a negative amplitude of said oscillation signal minus said DC component.

7. The anomaly detector of claim 6, wherein said window comparator has an upper threshold value defining the upper limit of said predetermined range and a lower threshold value defining the lower limit of said predetermined range, and said window comparator defines a midpoint value between said upper and lower threshold values corresponding to twice the value of said DC component that is generated when said DC component is of a normal value.

8. The anomaly detector of claim 5, wherein each of said periodic intervals is greater than a period of said oscillation signal.

9. The anomaly detector of claim 2, wherein said DC component detector produces said first signal by extracting an AC component from the oscillation signal and produces said second signal by directly using the oscillation signal to cancel the AC component contained therein with the extracted AC component.

10. The anomaly detector of claim 9, wherein said DC component detector comprises a filter for high-pass filtering said oscillation signal to produce said first signal.

11. The anomaly detector of claim 10, wherein said filter comprises:

an input terminal to which said oscillation signal is applied;

an operational amplifier having a noninverting input connected to a source of reference voltage and an inverting input;

a first capacitor connected between said input terminal and said inverting input of said operational amplifier;

a second capacitor connected between an output of said operational amplifier and said inverting input of the operational amplifier; and

an impedance circuit connected in parallel with said second capacitor.

12. The anomaly detector of claim 11, wherein said impedance circuit comprises;

a series of first and second resistors forming a circuit node therebetween; and

a third resistor connected between said circuit node and said source of reference voltage.

13. The anomaly detector of claim 11, wherein said impedance circuit comprises:

a series of first and second resistors forming a circuit node therebetween; and

a third capacitor connected between said circuit node and a constant potential level.

14. A sensing circuit comprising:

a sensing element that produces a signal representing oscillations of the sensing element in response to an externally applied force;

a DC component detector, associated with said conversion circuitry, that detects a DC component of said voltage, said detector including no timing delay element that introduces a delay in detecting said DC component; and

a window comparator, associated with said detector, that determines whether the detected DC component is within a predetermined range.

15. The sensing circuit of claim 14, wherein said sensing element produces a pair of voltage signals representing said oscillations of the sensing element, further comprising a differential amplifier that produces a differential signal representing the difference between said voltage signals, and wherein said DC component detector is connected to the output of said differential amplifier.

16. The sensing circuit of claim 14, wherein the DC component detector produces, from said oscillation signal, a pair of first and second signals having amplitudes of opposite polarities so that at least one of said first and second signals contains said DC component of the oscillation signal, and combines said first and second signals to detect said DC component by mutually canceling said amplitudes of opposite polarities.

17. The sensing circuit of claim 16, wherein said first signal is a DC amplitude of first polarity containing said DC component, and said second signal is a DC amplitude of second polarity containing said DC component, said second polarity being opposite to said first polarity.

18. The sensing circuit of claim 16, wherein said first signal is alternating amplitudes of first phase, and said second signal is alternating amplitudes of second phase opposite to said first phase, one of said first and second signals containing said DC component of the oscillation signal.

19. The sensing circuit of claim 16, wherein said AC component detector comprises:

a maximum detector that detects a positive peak value of said oscillation signal at periodic intervals; and

a minimum detector that detects a negative peak value of said oscillation signal at said periodic intervals synchronously with said maximum detector.

20. The sensing circuit of claim 19, wherein said positive peak value is equal to a positive amplitude of said oscillation signal plus said DC component and said negative peak value is equal to a negative amplitude of said oscillation signal minus said DC component.

21. The sensing circuit of claim 19, wherein said window comparator has an upper threshold value defining the upper limit of said predetermined range and a lower threshold value defining the lower limit of said predetermined range, and said window comparator defines a midpoint value between said upper and lower threshold values corresponding to twice the value of said DC component that is generated when said sensing circuit is operating properly.

22. The sensing circuit of claim 19, wherein each of said periodic intervals is greater than the period of said oscillation signal.

23. The sensing circuit of claim 19, wherein said periodic intervals are an integral multiple of the period of said oscillation signal.

24. The sensing circuit of claim 16, wherein said DC component detector produces said first signal by extracting an AC component from the oscillation signal and produces said second signal by directly using the oscillation signal to cancel the AC component contained therein with the extracted AC component.

25. The sensing circuit of claim 24, wherein said DC component detector comprises a filter for high-pass filtering said oscillation signal to produce said first signal.

26. The sensing circuit of claim 25, wherein said filter comprises:

an input terminal to which said oscillation signal is applied;

an operational amplifier having a noninverting input connected to a source of reference voltage and an inverting input;

a first capacitor connected between said input terminal and said inverting input of said operational amplifier;

a second capacitor connected between an output of said operational amplifier and said inverting input of the operational amplifier; and

an impedance circuit connected in parallel with said second capacitor.

27. The sensing circuit of claim 26, wherein said impedance circuit comprises:

a series of first and second resistors forming a circuit node therebetween; and

a third resistor connected between said circuit node and said source of reference voltage.

28. The sensing circuit of claim 26, wherein said impedance circuit comprises:

a series of first and second resistors forming a circuit node therebetween; and

a third capacitor connected between said circuit node and a constant potential level.

29. The sensing circuit of claim 25, wherein said DC component detector comprises an adder that combines said high-pass filtered oscillation signal with the AC component of said oscillation signal to detect said DC component.

30. A method of detecting anomaly of an oscillation signal, comprising the steps of:

detecting a DC component of said oscillation signal without using a timing delay element that introduces a delay in detecting said DC component; and

determining whether the detected DC component is within a predetermined range.

31. The method of claim 30, wherein the DC component detecting step comprises the steps of:

a) producing, from said oscillation signal, a pair of first and second signals having amplitudes of opposite polarities so that at least one of said first and second signals contains said DC component of the oscillation signal; and

b) combining said first and second signals to cancel the AC component of the oscillation signal to detect said DC component.

32. The method of claim 31, wherein said first signal is a DC amplitude of first polarity containing said DC component, and said second signal is a DC amplitude of second polarity containing said DC component, said second polarity being opposite to said first polarity.

33. The method of claim 31, wherein said first signal is alternating amplitudes of first phase, and said second signal is alternating amplitudes of second phase opposite to said first phase, one of said first and second signals containing said DC component of the oscillation signal.

34. The method of claim 31, wherein step (a) comprises detecting a positive peak value and a negative peak value of said oscillation signal synchronously at periodic intervals and wherein step (b) comprises combining the detected positive and negative peaks to detect said DC component.

35. The method of claim 31, wherein step (a) comprises high-pass filtering said oscillation signal to produce a replica of said AC component of the oscillation signal and wherein step (b) comprises combining the high-pass filtered signal with said oscillation signal to cancel the AC component of the oscillation signal with said replica to detect said DC component.