JP2006250643A - Abnormality detection device for angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the detection precision regarding the abnormality of the angular velocity sensor by detecting the oscillation frequency of the oscillator from the signal corresponding to the oscillation state. <P>SOLUTION: The angular velocity sensor comprises: the oscillator 1; the piezoelectric bodies 13, 14 being impressed with a driving signal for exciting the oscillator 1; the piezoelectric bodies 15, 16 for detecting the monitor signal corresponding to the oscillation of the oscillator 1; and the signal process circuit 100 for outputting the driving signal adjusted capable of keeping a certain oscillation amplitude of the ossillator 1. The signal process circuit 100 is provided with: a frequency dividing circuit 121 for outputting the frequency dividing signal by dividing the monitor signal or the driving signal; and the abnormality detection circuit 121 for detecting the abnormality of the oscillation, on the basis of whether the frequency of the frequency divided signal belongs to a prescribed frequency range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an abnormality detection device for an angular velocity sensor.

  A conventional apparatus capable of detecting an abnormality of an angular velocity sensor is disclosed in Patent Document 1, for example. This conventional apparatus includes waveform determining means for determining whether the waveform of the feedback signal (vibration monitor signal) from the vibrator of the angular velocity sensor is in a normal state or an abnormal state.

Specifically, the amplitude of the feedback signal of the vibrator is detected, and whether the waveform is normal or abnormal is determined based on whether or not this amplitude is a predetermined amplitude. However, it is described that the phase and frequency of the feedback signal may be detected instead of the amplitude.
JP 2002-188921 A

  In an angular velocity sensor drive circuit, a feedback loop is usually formed in order to excite the vibrator at a specific resonance frequency. That is, the drive circuit includes an AGC circuit, and the AGC circuit controls the magnitude of the drive signal in accordance with the amplitude of the feedback signal. As a result, the vibration amplitude of the vibrator becomes constant, and as a result, the vibration frequency of the vibrator matches the resonance frequency described above.

  However, for example, when a foreign object adheres to the vibrator or a part of the vibrator is damaged and the shape of the vibrator is changed, the vibrator has a constant vibration amplitude as described above. Is excited, the vibration frequency of the vibrator deviates from the resonance frequency described above. Therefore, by monitoring the deviation of the vibration frequency of the vibrator from the resonance frequency, it is possible to detect abnormalities such as adhesion of foreign matter to the vibrator and shape change.

  Here, the vibration frequency of the vibrator is often set to a high frequency of, for example, 2 kHz or more so as not to be affected by disturbance vibration or the like. However, for example, an electronic component having an oscillation circuit therein may generate high frequency noise belonging to such a high frequency band. When such high frequency noise acts on the vibration frequency monitoring circuit, it becomes difficult to accurately detect the vibration frequency of the vibrator based on the feedback signal from the vibrator.

  The present invention has been made in view of the above-described points, and can accurately detect the vibration frequency of the vibrator from a signal corresponding to the vibration state of the vibrator, thereby improving the detection accuracy regarding abnormality of the angular velocity sensor. An object of the present invention is to provide a sensor abnormality detection device.

In order to achieve the above-described object, an abnormality detection device for an angular velocity sensor according to claim 1 is provided.
A vibrator,
When the vibrator is excited, it outputs a monitor signal output means for outputting a monitor signal corresponding to the vibration of the vibrator and a drive signal for exciting the vibrator, and based on the monitor signal, An abnormality detection device in an angular velocity sensor having a drive signal output circuit that outputs a drive signal adjusted so that the vibration amplitude of the vibrator becomes constant,
Frequency dividing means for dividing the monitor signal or the drive signal and outputting the divided signal;
And determining means for determining abnormality of the vibrator based on whether or not the frequency of the frequency-divided signal belongs to a predetermined frequency range.

  As described above, since the abnormality detection device for an angular velocity sensor according to claim 1 includes a frequency dividing circuit, the monitor signal or the drive signal is converted into a frequency divided signal having a frequency lower than that. Can do. The frequency band of this frequency-divided signal is lower than the frequency band of high-frequency noise generated by the electronic circuit. For this reason, the vibration frequency of the vibrator can be accurately detected from the frequency-divided signal regardless of the influence of high-frequency noise, and it is also possible to detect minute changes in the vibration frequency due to foreign matter adhering to the vibrator or shape change Become.

  The frequency dividing circuit preferably divides the monitor signal or the drive signal so that the frequency of the frequency-divided signal is 1 kHz or less. Since most of the high frequency noise belongs to a frequency band of 2 kHz or higher, it is preferable to set the frequency of the frequency-divided signal to 1 kHz or lower in order to reliably separate it.

  According to a third aspect of the present invention, the abnormality detection means includes a conversion means for converting the frequency-divided signal into a voltage signal, a voltage signal converted by the conversion means, and an upper limit corresponding to an upper limit and a lower limit of a predetermined frequency range. It is preferable to have a comparison means for comparing the voltage value and the lower limit voltage value. With such a configuration, it is possible to reliably detect whether the vibration frequency of the vibrator belongs to a predetermined frequency range based on the resonance frequency.

(First embodiment)
The angular velocity sensor abnormality detection apparatus according to the first embodiment of the present invention will be described below. First, based on FIG.1 and FIG.2, the structure of the vibrator | oscillator 1 of an angular velocity sensor is demonstrated. 1 is a perspective view of the vibrator 1, and FIG. 2 is a cross-sectional view taken along the line AA of FIG.

  As shown in FIG. 1, the vibrator 1 is a tuning fork vibrator in which two vibrator elements 11 and 12 protrude from the vibrator base 10 in the same direction. The vibrator 1 is made of, for example, a non-piezoelectric material such as ceramic, and a piezoelectric body such as PZT is pasted on the vibrating pieces 11 and 12.

  The piezoelectric body includes driving piezoelectric bodies 13 and 14 attached to the outer side surface of the vibrating piece 11 and the inner side surface of the vibrating piece 12. An AC voltage having an opposite phase is applied to the driving piezoelectric bodies 13 and 14. Then, the driving piezoelectric bodies 13 and 14 are distorted so as to expand or contract due to the inverse piezoelectric effect, and the resonator elements 11 and 12 repeat symmetrical vibrations so as to approach / separate from each other along the X direction.

  For example, when a voltage having a phase is applied to the driving piezoelectric body 13 via the driving electrode D + and a voltage having a phase opposite to that of the driving piezoelectric body 14 is applied to the driving piezoelectric body 14 via the driving electrode D−, It is assumed that the driving piezoelectric body 13 contracts and the driving piezoelectric body 14 expands. In this case, the vibrating bars 11 and 12 are both bent outward due to the contraction of the driving piezoelectric member 13 and the extension of the driving piezoelectric member 14. On the contrary, when the driving piezoelectric member 13 expands and the driving piezoelectric member 14 contracts, both the vibrating pieces 11 and 12 bend inward. By periodically applying such a voltage using an AC voltage, the resonator elements 11 and 12 are vibrated in the opposite phase in the X direction at a specific resonance frequency determined by the shape and material of the resonator elements 11 and 12. Can do.

  Further, the piezoelectric body includes monitor piezoelectric bodies 15 and 16 and detection piezoelectric bodies 17 and 18. The monitor piezoelectric members 15 and 16 are attached to the inner side surface and the outer side surface of the resonator elements 11 and 12 so as to face the driving piezoelectric members 13 and 14, respectively. When the vibration pieces 11 and 12 are excited by application of an alternating voltage to the driving piezoelectric bodies 13 and 14, the monitoring piezoelectric bodies 15 and 16 are distorted by the vibrations, and the positive piezoelectric effect causes the distortion. The electric charge according to is generated. Therefore, the excitation state of the resonator elements 11 and 12 can be detected by the monitor piezoelectric members 15 and 16.

  The detection piezoelectric members 17 and 18 are attached to the outer side surface to which the driving piezoelectric members 13 and 14 and the monitor piezoelectric members 15 and 16 are attached and the side surface (front surface) orthogonal to the inner side surface. When an angular velocity is generated around the Y axis when the vibrating pieces 11 and 12 are excited, the vibrating pieces 11 and 12 vibrate along the Z-axis direction by Coriolis force according to the angular velocity. The detection piezoelectric members 17 and 18 generate electric charges according to the magnitude of vibration in the Z-axis direction.

  Here, the detection principle of the angular velocity will be briefly described with reference to FIG. The vibrating bars 11 and 12 of the vibrator 1 are vibrated in the opposite direction in the X direction as shown in FIG. 3, and when the vibrator 1 rotates at an angular velocity Ω around the Y axis in this state, the vibrating bars 11 and 12 The Coriolis force F expressed by F = 2 mV × Ω acts in the Z direction. Note that m is the mass of the resonator element, and V is the vibration speed.

  Due to the action of the Coriolis force F, the vibrating bars 11 and 12 are 90 ° out of phase with respect to the vibration in the X direction, and vibrate in the Z direction in opposite phases. Therefore, the angular velocity acting around the Y axis can be detected by the detecting piezoelectric members 17 and 18 that generate charges according to the magnitude of vibration in the Z-axis direction.

  Next, a driving signal (AC voltage signal) for driving the vibrator 1 of the above-described angular velocity sensor is generated, or based on the electric charges generated by the detection piezoelectric members 17 and 18 according to the acting angular velocity. The signal processing circuit 100 for outputting the angular velocity signal will be described with reference to FIG.

  FIG. 4 is a block diagram showing a circuit configuration of the signal processing circuit 100. In FIG. 4, charge amplifiers 101 to 104 use the monitor electrodes M + and M− and the detection electrodes S + and S−, respectively, for the charges generated in the monitor piezoelectric bodies 15 and 16 and the detection piezoelectric bodies 17 and 18. The charge amount is inverted and amplified and converted into a voltage value.

  The differential amplifier circuit 105 is a circuit that amplifies and outputs the output voltage difference between the charge amplifiers 101 and 102, and the output voltage represents the vibration amplitude in the X direction of the resonator elements 11 and 12. That is, since the monitor piezoelectric members 15 and 16 are attached to the inner side surface and the outer side surface of the resonator elements 11 and 12 that vibrate in opposite phases, the voltage values output from the charge amplifiers 101 and 102 are also opposite in phase. It becomes. For this reason, if the output voltage difference between the charge amplifiers 101 and 102 is amplified, the amplified output voltage corresponds to the vibration amplitude in the X direction of the resonator elements 11 and 12.

  The phase modulation circuit 106 performs phase modulation so as to shift the phase of the output voltage of the differential amplifier circuit 105 by about 90 ° to generate a phase modulation monitor signal. When a drive signal is applied to the drive piezoelectric members 13 and 14 to vibrate the resonator elements 11 and 12, the vibration pieces 11 and 12 are generated based on the phase of the drive signal and the charges generated by the monitor piezoelectric members 15 and 16. The phase of the voltage signal (monitor signal) is shifted by about 90 °. Therefore, a phase modulation circuit 106 is provided in order to match the phases of the monitor signal and the drive signal. The phase modulation monitor signal output from the phase modulation circuit 106 is supplied to the rectifier circuit 107 and the gain control circuit 110.

  The rectifier circuit 107 rectifies the phase modulation monitor signal and outputs a vibration amplitude signal indicating the magnitude of the vibration amplitude. The differential amplifier 109 receives the vibration amplitude signal and a drive reference value indicating the magnitude of the target vibration amplitude output from the drive reference value output circuit 108, and outputs a voltage difference between the two signals. The rectifier circuit 107 may be configured to input a monitor signal before phase modulation.

  The gain control circuit 110 generates a drive signal (AC voltage signal) synchronized with the phase modulation monitor signal input from the phase modulation circuit 106. At that time, the gain adjustment at the time of outputting the drive signal is performed based on the output voltage difference from the differential amplifier 109 so that the magnitude of the vibration amplitude of the vibration pieces 11 and 12 matches the magnitude of the target vibration amplitude. .

  When the drive signal from the gain control circuit 110 is output to the drive electrodes D + and D−, the vibrator 1 is excited so that the magnitude of the vibration amplitude is constant. The phase inversion circuit 111 inverts the phase of the drive signal in order to apply a drive signal having a phase opposite to that of the drive electrode D + to the drive electrode D−.

  On the other hand, the differential amplifier circuit 112 is a circuit that amplifies and outputs the output voltage difference between the charge amplifiers 103 and 104, and the output voltage signal corresponds to the vibration of the vibrating pieces 11 and 12 in the Z direction. As described above, when rotation about the Y axis is applied to the vibrator 1, Coriolis force acts in the Z direction on the vibrating pieces 11 and 12 vibrating in the X direction, and the drive signal is shifted in phase by 90 °. Vibration occurs. At this time, since the resonator elements 11 and 12 vibrate in the opposite direction in the Z direction, an output voltage corresponding to the angular velocity can be obtained by taking the difference between the output voltages of the charge amplifiers 103 and 104.

  However, the output of the differential amplifier circuit 112 is synchronized with the vibration generated by the Coriolis force resulting from the generation of the angular velocity. Therefore, the synchronous detection circuit 113 performs synchronous detection using the phase modulation monitor signal synchronized with the drive signal output from the phase modulation circuit 106, and outputs the frequency component corresponding to the vibration frequency by the drive signal to the output of the differential amplifier circuit 112. Extract from and rectify. Further, the smoothing circuit 114 smoothes the output of the synchronous detection circuit 113. Thereby, an angular velocity detection signal corresponding to the angular velocity around the Y axis can be output from the output terminal 115.

  Next, when an abnormality such as a change in the shape of the vibrating bars 11, 12 due to adhesion of foreign matter to the vibrating bars 11, breakage or the like related to the characteristic part of the present embodiment occurs, the vibrating bars 11, 12 An abnormality detection circuit for detecting the abnormality based on the change in the vibration frequency of 12 will be described.

First, changes in the vibration frequency due to foreign matter adhesion to the vibration pieces 11 and 12 and changes in the shape of the vibration pieces 11 and 12 will be described. The motion model of the vibrating reeds 11 and 12 can be simplified as shown in FIG. 5, and at this time, the inherent resonance frequency fn of the vibrating reeds 11 and 12 can be expressed by the following Equation 1.
(Formula 1) fn = 1 / 2π × (k / m) ^1/2
Here, m is the mass of the resonator element, and k is the spring constant of the resonator element.

  When there is no abnormality in the vibration pieces 11 and 12, the vibration pieces 11 and 12 are driven as shown in FIG. 6A by driving the vibration pieces 11 and 12 so that the vibration amplitude matches the target vibration amplitude. As shown, it is excited at a constant frequency fn. However, when a foreign object adheres to the vibration pieces 11 and 12 or a part of the vibration pieces 11 and 12 is damaged and the shape of the vibration pieces 11 and 12 changes, the vibration amplitude of the vibration pieces 11 and 12 is constant. When the vibration pieces 11 and 12 are excited so that the vibration frequency becomes as follows, the vibration frequency of the vibration pieces 11 and 12 is deviated from the resonance frequency described above.

  For example, when a foreign object adheres to the vibrating bars 11 and 12, the mass of the vibrating bars 11 and 12 changes from m to m + Δm, so that the vibration frequency is lowered as shown in FIG. In addition, for example, when the vibration pieces 11 and 12 are damaged such that the bases of the vibration pieces 11 and 12 are cracked or a part of the tip of the vibration piece is broken, the shape of the vibration pieces 11 and 12 is changed. The length of the vibrating bars 11 and 12 changes. As a result, since the spring constant changes from k to k ± Δk, the frequency fluctuation shown in the abnormal time 1 of FIG. 6B or the abnormal time 2 of FIG. 6C occurs.

  When such abnormalities of the vibrating bars 11 and 12 occur, not only the target excitation state cannot be obtained but also a pseudo angular velocity detection signal is output even though the angular velocity is not input. This also leads to deterioration of detection accuracy. Therefore, in the first embodiment, an abnormality detection circuit 120 is added to the signal processing circuit 100 of the angular velocity sensor to constantly monitor the vibration frequency of the vibration pieces 11 and 12 and output a diagnosis signal when vibration is abnormal. That is, when an abnormality such as adhesion of foreign matter or shape change to the vibrating bars 11 and 12 occurs, the vibration frequency of the vibrating bars 11 and 12 deviates from the resonance frequency. Is detected as a vibration abnormality and a diagnosis signal is output.

  The circuit configuration and operation of the abnormality detection circuit 120 will be described with reference to FIG. As shown in FIG. 4, the abnormality detection circuit 120 divides a signal (monitor signal) representing the vibration amplitude in the X direction of the resonator elements 11 and 12 output from the differential amplifier 105 to generate a divided monitor signal. A frequency dividing circuit 121 is provided. In other words, the frequency dividing circuit 121 converts the monitor signal representing the vibration amplitude of the vibrating reeds 11 and 12 into a frequency divided monitor signal with a frequency lower than that.

  Here, the vibration frequency of the resonator elements 11 and 12 is set to, for example, a high frequency of 2 kHz or more so as not to be affected by disturbance vibration or the like. However, for example, an electronic component having an oscillation circuit therein may generate high frequency noise belonging to such a high frequency band. When such high-frequency noise acts on the abnormality detection circuit 120 and is mixed into the monitor signal, it becomes difficult to accurately detect the vibration frequency of the resonator elements 11 and 12 based on the monitor signal.

  For such a problem, by providing the above-described frequency dividing circuit 121, the frequency band of the frequency division monitor signal can be shifted from the frequency band of the high frequency noise generated by the electronic circuit. For this reason, it is possible to accurately detect the vibration frequency of the vibrator from the divided monitor signal regardless of the influence of the high frequency noise, and the minute change in the vibration frequency due to the adhesion of foreign matter to the vibration pieces 11 and 12 and the shape change. Detection is also possible.

  The frequency dividing circuit 121 preferably divides the monitor signal so that the frequency of the divided monitor signal is 1 kHz or less. This is because most of the high-frequency noise belongs to the frequency band of 2 kHz or higher, so that it is reliably separated from them.

  The frequency division monitor signal whose frequency is lowered by the frequency dividing circuit 121 is input to a frequency counter 122 that converts the frequency into a voltage signal. The voltage signal output from the frequency counter 122 is input to the comparator 125. The comparator 125 further includes an upper limit and a lower limit of a predetermined frequency range based on the resonance frequency for the voltage signal converted from the frequency division monitor signal from the upper limit value output circuit 123 and the lower limit value output circuit 124. An upper limit voltage value and a lower limit voltage value corresponding to are input. The comparator 125 outputs a diagnosis signal via the output terminal 126 when the voltage signal converted from the frequency division monitor signal is out of the range defined by the upper limit voltage value and the lower limit voltage value.

  As described above, in the present embodiment, the abnormality detection circuit 120 including the frequency dividing circuit 121 is provided, so that even a minute change in the vibration frequency based on the abnormality of the vibrator 1 can be detected with high accuracy, and this is indicated by a diagnosis signal. Can be notified.

  In the first embodiment described above, the frequency dividing circuit 121 divides the monitor signal output from the differential amplifier circuit 105, but divides the drive signal output from the gain control circuit 110. You may comprise as follows.

(Second Embodiment)
Next, an abnormality detection device for an angular velocity sensor according to a second embodiment of the present invention will be described. 7 and 8 show the configuration of the vibrator 2 of the angular velocity sensor according to the second embodiment of the present invention, FIG. 7 is a perspective view of the vibrator 2, and FIG. It is BB sectional drawing of.

  Similar to the first embodiment, the vibrator 2 is a tuning fork vibrator in which two vibrating pieces 21 and 22 protrude from the vibrator base 20. The difference from the first embodiment is the material of the vibrator 2. The vibrator 2 is made of, for example, a piezoelectric material such as quartz, and the vibrator elements 21 and 22 themselves of the vibrator 2 exhibit a reverse piezoelectric effect or a positive piezoelectric effect.

  Therefore, the vibration pieces 21 and 22 include a drive electrode for applying a voltage, and a monitor electrode and a detection electrode for detecting the induced polarization generated in the vibration pieces 21 and 22 when the vibration pieces 21 and 22 are distorted. It is pasted. Therefore, by applying a drive signal composed of an AC voltage signal to the drive electrodes via the drive electrode terminals D + and D−, the resonator elements 21 and 22 themselves are distorted by the inverse piezoelectric effect, and the resonator elements 21 and 22 It vibrates in the opposite phase along the direction. The electric charges corresponding to the distortion of the vibrating bars 21 and 22 due to the vibration are detected by the monitor electrode and input to the signal processing circuit via the monitor electrode terminals M1 +, M1-, M2 +, and M2-. Further, when an angular velocity is generated around the Y axis, the resonator elements 21 and 22 vibrate in the opposite direction along the Z axis direction by Coriolis force according to the angular velocity. Charges corresponding to the distortion of the vibrating bars 21 and 22 due to the vibration are detected by the detection electrodes and input to the signal processing circuit via the detection electrode terminals S1 +, S1-, S2 +, and S2-.

  FIG. 9 shows the configuration of the signal processing circuit according to the second embodiment, but the circuit configuration and operation are substantially the same as those of the signal processing circuit 100 according to the first embodiment described above, and thus the description thereof is omitted.

  As described above, even when the vibrator 2 itself is made of a piezoelectric material, the vibration abnormality of the vibrator 1 based on the abnormality of the vibrator 1 is monitored by monitoring the vibration abnormality of the vibrator 2 using a frequency dividing circuit. Even a minute change can be detected with high accuracy, and the fact can be notified by a diagnosis signal.

It is a perspective view which shows the structure of the vibrator | oscillator of the angular velocity sensor concerning 1st Embodiment. It is AA sectional drawing of FIG. It is explanatory drawing for demonstrating the detection principle of angular velocity. It is a block diagram which shows the circuit structure of the signal processing circuit in 1st Embodiment. It is a model figure which shows the motion model of a vibration piece. The vibration state of the resonator element is shown. (A) shows a normal vibration frequency, (b) shows a state where the vibration frequency is lowered, and (c) shows a state where the vibration frequency is increased. It is a perspective view which shows the structure of the vibrator | oscillator of the angular velocity sensor concerning 2nd Embodiment. It is BB sectional drawing of FIG. It is a block diagram which shows the circuit structure of the signal processing circuit in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrator 11, 12 Vibrating piece 13,14 Drive piezoelectric body 15,16 Monitor piezoelectric body 17,18 Detection piezoelectric body 100 Signal processing circuit 120 Abnormality detection circuit 121 Frequency dividing circuit 122 Frequency counter 123 Upper limit output circuit 124 Lower limit output circuit 125 comparator

Claims (3)

A vibrator,
A monitor signal output means for outputting a monitor signal corresponding to the vibration of the vibrator when the vibrator is excited; and a drive signal for exciting the vibrator, An abnormality detection device in an angular velocity sensor, having a drive signal output circuit that outputs a drive signal adjusted so that the vibration amplitude of the vibrator is constant,
Frequency dividing means for dividing the monitor signal or the drive signal and outputting a divided signal;
An abnormality detection apparatus for an angular velocity sensor, comprising: a determination unit configured to determine abnormality of the vibrator based on whether or not a frequency of the divided signal belongs to a predetermined frequency range.   2. The angular velocity sensor abnormality detection device according to claim 1, wherein the frequency dividing circuit divides the monitor signal or the drive signal so that a frequency of the frequency-divided signal is 1 kHz or less.   The abnormality detection means includes: a conversion means for converting the frequency-divided signal into a voltage signal; a voltage signal converted by the conversion means; and an upper limit voltage value and a lower limit voltage value corresponding to an upper limit and a lower limit of the frequency range. The abnormality detecting device for an angular velocity sensor according to claim 1 or 2, further comprising a comparison means for comparing.

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