JP5349199B2 - Angular velocity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an angular velocity around 3 axes with high precision by a time sharing detection operation. <P>SOLUTION: An oscillator is bonded to the central portion of a lower face of a flexible supporter extending to an XY plane and a sensor body 300 having a drive element group and a detection element group on the top face thereof is prepared. A driving signal DrZ for Z-axis exciting the oscillator at a first-half period and a drive signal DrX for X-axis exciting the oscillator at a second-half period are generated by an operating signal generator 100 and supplied to the drive element group through a matrix converter 200. Each displacement S&Delta;x, S&Delta;y, S&Delta;z of the oscillator in each axial direction is detected by a signal from the detection element group and transmitted to an AM detector AMD and a synchronous detector SD synchronous with the driving signal at only a vibration stabilization period through a switch SW. An amplitude Fxa and a phase Fxp of X-axis vibration and an amplitude Fza and a phase Fzp of Z-axis vibration are fed back to the operating signal generator 100 for feedback control and signals outputted from the predetermined synchronous detector SD are outputted as angular velocities &omega;x, &omega;y, &omega;z of 3 axes. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an angular velocity sensor, and more particularly to a signal processing circuit used for an angular velocity sensor that can detect angular velocities around three independent axes.

  In the field of industrial equipment and consumer equipment, the demand for a built-in small angular velocity sensor is increasing. Since the angular velocity is also a vector quantity as with acceleration and force, a three-dimensional angular velocity sensor capable of detecting angular velocities about three independent axes in a three-dimensional space is desired in practice. For example, Patent Document 1 below discloses a capacitive sensor and a piezoelectric sensor that can detect a three-dimensional angular velocity as well as a three-dimensional acceleration.

  The detection principle of a general angular velocity sensor is to measure the Coriolis force acting on the vibrator in the second coordinate axis direction in a state where the vibrator is vibrated in the first coordinate axis direction in a three-dimensional orthogonal coordinate system. By doing so, the angular velocity around the third coordinate axis is obtained. With such a detection principle, angular velocity detection around two coordinate axes orthogonal to the vibration direction of the vibrator is possible, but angular velocity detection around the coordinate axis facing the vibration direction of the vibrator cannot be performed. Therefore, in order to detect angular velocities around three axes, it is necessary to vibrate the vibrator along two coordinate axes.

  <§7.2> of Patent Document 1 described above discloses a time-division detection operation for detecting angular velocities around three axes. In this detection operation, first, the angular velocity around the second coordinate axis and the angular velocity around the third coordinate axis are detected in a state where the vibrator is vibrated in the first coordinate axis direction, and then the vibrator is moved to the second coordinate axis. The angular velocity around the first coordinate axis is detected in the state of being oscillated in the coordinate axis direction. <§7.3> of the same document also discloses a detection circuit for performing such a time division detection operation.

WO94 / 023272

  As described above, an angular velocity sensor having a function of detecting angular velocities around three axes by a time-division detection operation is known as shown in Patent Document 1 described above. However, the conventional signal processing circuit used for the angular velocity sensor having such a function has a problem that a highly accurate detection value cannot be obtained. That is, in the time division detection operation, it is necessary to alternately perform a detection operation performed while vibrating the vibrator in the first axial direction and a detection operation performed while vibrating the vibrator in the second axial direction. However, if the vibration direction of the vibrator is changed alternately, the movement of the vibrator becomes unstable and accurate measurement cannot be performed.

  Therefore, an object of the present invention is to provide an angular velocity sensor that can detect angular velocities around three axes with high accuracy by a time-division detection operation.

(1) A first aspect of the present invention is an angular velocity sensor for detecting an angular velocity around each coordinate axis in an XYZ three-dimensional coordinate system.
A flexible support having an upper surface passing through the Z-axis at a central position and parallel to the XY plane;
A vibrator bonded to the center of the lower surface of the flexible support;
A fixing member for fixing the periphery of the flexible support;
A drive element group disposed above the flexible support;
A group of detection elements disposed above the flexible support;
An AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and an electrical signal indicating an angular velocity around each coordinate axis is detected using a detection signal obtained from the detection element group at a predetermined timing. A detection circuit for outputting a signal;
Provided,
The drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive element arranged in the X-axis negative area when projected onto the XY plane. , A Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area, and the X-axis positive drive element and X When an AC drive signal is supplied to the negative axis driving element, the vibrator vibrates along the X axis, and when an AC drive signal is supplied to the Y axis positive driving element and the Y axis negative driving element, the vibrator Oscillates along the Y-axis, and when the AC drive signal is supplied to all of the four sets of driving elements, the vibrators oscillate along the Z-axis. Has the function of causing
The detection element group includes an X-axis positive detection element arranged in the X-axis positive area and an X-axis negative detection element arranged in the X-axis negative area when projected onto the XY plane. The Y-axis positive side detection element arranged in the Y-axis positive area and the Y-axis negative side detection element arranged in the Y-axis negative area are symmetrical with respect to both the XZ plane and the YZ plane. The Z-axis displacement detection element is arranged, and the X-axis positive side detection element and the X-axis negative side detection element are formed on the flexible support when the vibrator is displaced in the X-axis direction. Due to the bending that occurs, the detection signal having an absolute value corresponding to the displacement and having opposite polarities is output. The Y-axis positive detection element and the Y-axis negative detection element are arranged in the Y-axis direction. Due to the bending that occurs in the flexible support when it is displaced in the direction of The Z-axis displacement detection element has an absolute value corresponding to the displacement and a polarity corresponding to the displacement direction due to the bending that occurs in the flexible support when the vibrator is displaced in the Z-axis direction. The function of outputting the detection signal of
The detection circuit
Having a function of executing a periodic operation for a period T constituted by the first half period T1 and the second half period T2,
In the first half cycle T1, a drive signal for vibrating the vibrator in the first coordinate axis direction is supplied to the specific drive element, and in the second half cycle T2, the vibrator is moved to the specific drive element. Supplying a drive signal for vibrating in the second coordinate axis direction;
During the period of the stable vibration period in the first coordinate axis direction in which the vibrator is expected to maintain a stable vibration state in the first half cycle T1, the second due to the Coriolis force of the vibrator obtained from the detection element group. Based on the detected value indicating the displacement in the coordinate axis direction, the angular velocity around the third coordinate axis is detected, and the displacement in the third coordinate axis direction caused by the Coriolis force of the vibrator obtained from the detection element group is indicated. Based on the detected value, the angular velocity around the second coordinate axis is detected,
During the period of the stable vibration period with respect to the second coordinate axis direction in which the vibrator is expected to maintain a stable vibration state in the second half cycle T2, the third due to the Coriolis force of the vibrator obtained from the detection element group. The angular velocity around the first coordinate axis is detected based on the detection value indicating the displacement in the coordinate axis direction.

(2) According to a second aspect of the present invention, in the angular velocity sensor according to the first aspect described above,
The detection circuit has a function of measuring the phase and amplitude of the vibrator based on a signal obtained from the detection element group, and a function of performing feedback control on the phase and amplitude of the vibrator based on the measurement value. It is what I did.

(3) According to a third aspect of the present invention, in the angular velocity sensor according to the first or second aspect described above,
When the resonance frequency of the vibrator with respect to a specific vibration direction is f0, the time when the vibrator is expected to be in a stable vibration state from the start of supplying a drive signal for vibrating the vibrator in the vibration direction The period α is set in the range of (1 / f0) × 50 ≦ α ≦ (1 / f0) × 125.

(4) According to a fourth aspect of the present invention, in the angular velocity sensor according to the third aspect described above,
When the resonance frequency of the vibrator in the first coordinate axis direction is f1, and the resonance frequency of the vibrator in the second coordinate axis direction is f2, the first half cycle T1 is (1 / f1) × 100. ≦ T1 ≦ (1 / f1) × 250, and the second half cycle T2 is set to a range of (1 / f2) × 100 ≦ T2 ≦ (1 / f2) × 250 It is.

(5) The fifth aspect of the present invention is an angular velocity sensor for detecting an angular velocity around each coordinate axis in an XYZ three-dimensional coordinate system.
A flexible support having an upper surface passing through the Z-axis at a central position and parallel to the XY plane;
A vibrator bonded to the center of the lower surface of the flexible support;
A fixing member for fixing the periphery of the flexible support;
A drive element group disposed above the flexible support;
A group of detection elements disposed above the flexible support;
While performing control based on the detection signal obtained from the detection element group, an AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and from the detection element group at a predetermined timing. A detection circuit that outputs an electrical signal indicating an angular velocity around each coordinate axis using the obtained detection signal;
Provided,
The drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive element arranged in the X-axis negative area when projected onto the XY plane. , A Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area, and the X-axis positive drive element and X When an AC drive signal is supplied to the negative axis driving element, the vibrator vibrates along the X axis, and when an AC drive signal is supplied to the Y axis positive driving element and the Y axis negative driving element, the vibrator Oscillates along the Y-axis, and when the AC drive signal is supplied to all of the four sets of driving elements, the vibrators oscillate along the Z-axis. It plays the function of causing the bending of
The detection element group includes an X-axis positive detection element arranged in the X-axis positive area and an X-axis negative detection element arranged in the X-axis negative area when projected onto the XY plane. The Y-axis positive side detection element arranged in the Y-axis positive area and the Y-axis negative side detection element arranged in the Y-axis negative area are symmetrical with respect to both the XZ plane and the YZ plane. The Z-axis displacement detection element is arranged, and the X-axis positive side detection element and the X-axis negative side detection element are formed on the flexible support when the vibrator is displaced in the X-axis direction. Due to the bending that occurs, the detection signal having an absolute value corresponding to the displacement and having opposite polarities is output. The Y-axis positive detection element and the Y-axis negative detection element are arranged in the Y-axis direction. Due to the bending that occurs in the flexible support when it is displaced in the direction of The Z-axis displacement detection element has an absolute value corresponding to the displacement and a polarity corresponding to the displacement direction due to the bending that occurs in the flexible support when the vibrator is displaced in the Z-axis direction. The function to output the detection signal of
The detection circuit
For the period T constituted by the first half period T1 and the second half period T2, it has a function of executing a periodic operation, and
An AC signal having a predetermined frequency and amplitude is arranged in the first half cycle T1, and a first drive signal is generated in the second half cycle T2, in which no AC signal is arranged. A first drive signal generator that
In the first half cycle T1, no AC signal is arranged, and in the second half cycle T2, an AC signal having a predetermined frequency and amplitude is arranged. A second drive signal generator for generating;
In the first half cycle T1, pulses having a pulse width equal to or less than ½ of the cycle of the first drive signal are periodically arranged at a position synchronized with the positive peak of the first drive signal. In the second half cycle T2, pulses having a pulse width of 1/2 or less of the cycle of the second drive signal are periodically arranged at positions synchronized with the positive peak of the second drive signal. A positive side synchronous detection signal generating unit for generating a positive side synchronous detection signal;
In the first half cycle T1, pulses having a pulse width equal to or less than ½ of the cycle of the first drive signal are periodically arranged at a position synchronized with the negative peak of the first drive signal. In the second half cycle T2, pulses having a pulse width equal to or less than ½ of the cycle of the second drive signal are periodically arranged at a position synchronized with the negative peak of the second drive signal. A negative side synchronous detection signal generating unit for generating a negative side synchronous detection signal;
A first detection enable signal generator for generating a first detection enable signal indicating a first stable oscillation period in which the vibrator is expected to maintain a stable vibration state in the first half period T1,
A second detection enable signal generator for generating a second detection enable signal indicating a second stable oscillation period in which the vibrator is expected to maintain a stable vibration state in the second half period T2,
In the first half cycle T1, the first drive signal or its phase inversion signal is supplied to the drive element necessary to vibrate the vibrator in the first coordinate axis direction, and in the second half cycle T2, A matrix converter that supplies a second drive signal or a phase inversion signal thereof to a drive element necessary for vibrating the vibrator in the second coordinate axis direction;
In the period of the first stable oscillation period, the displacement in the second coordinate axis direction due to the Coriolis force of the vibrator obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal is shown. A first angular velocity detector that outputs an electrical signal indicating an angular velocity around the third coordinate axis based on the detected value;
In the period of the first stable oscillation period, the displacement in the third coordinate axis direction due to the Coriolis force of the vibrator obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal is shown. A second angular velocity detector that outputs an electrical signal indicating an angular velocity around the second coordinate axis based on the detected value;
In the period of the second stable oscillation period, the displacement in the third coordinate axis direction caused by the Coriolis force of the vibrator obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal is shown. A third angular velocity detector that outputs an electrical signal indicating an angular velocity around the first coordinate axis based on the detected value;
A first amplitude measurement unit that measures the amplitude of the vibrator based on a detection value indicating displacement of the vibrator in the first coordinate axis direction obtained from the detection element group during the first stable vibration period;
Based on the detected value indicating the displacement of the transducer in the first coordinate axis direction obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable vibration period. A first phase measuring unit for measuring the phase of the vibrator;
A second amplitude measuring unit for measuring the amplitude of the vibrator based on a detection value indicating displacement of the vibrator in the second coordinate axis direction obtained from the detection element group during the second stable vibration period;
Based on the detection value indicating the displacement of the vibrator in the second coordinate axis direction obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable vibration period. A second phase measurement unit for measuring the phase of the vibrator;
Based on the amplitude measured by the first amplitude measurement unit and the phase measured by the first phase measurement unit, the frequency and amplitude of the first drive signal generated by the first drive signal generation unit is a predetermined reference. The feedback control is performed so that the frequency and the reference amplitude are obtained, and the second drive signal generation unit is generated based on the amplitude measured by the second amplitude measurement unit and the phase measured by the second phase measurement unit. A feedback control unit that performs feedback control so that the frequency and amplitude of the second drive signal become a predetermined reference frequency and reference amplitude;
Is provided.

(6) The sixth aspect of the present invention is an angular velocity sensor for detecting an angular velocity around each coordinate axis in an XYZ three-dimensional coordinate system.
A flexible support having an upper surface passing through the Z-axis at a central position and parallel to the XY plane;
A vibrator bonded to the center of the lower surface of the flexible support;
A fixing member for fixing the periphery of the flexible support;
A drive element group disposed above the flexible support;
A group of detection elements disposed above the flexible support;
While performing control based on the detection signal obtained from the detection element group, an AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and from the detection element group at a predetermined timing. A detection circuit that outputs an electrical signal indicating an angular velocity around each coordinate axis using the obtained detection signal;
Provided,
The drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive element arranged in the X-axis negative area when projected onto the XY plane. , A Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area, and the X-axis positive drive element and X When an AC drive signal is supplied to the negative shaft side drive element, the vibrator vibrates along the X axis, and when an AC drive signal is supplied to all of the four sets of drive elements, the vibrator vibrates along the Z axis. As described above, each of the arrangement positions of the flexible support functions to cause a specific deflection,
The detection element group includes an X-axis positive detection element arranged in the X-axis positive area and an X-axis negative detection element arranged in the X-axis negative area when projected onto the XY plane. The Y-axis positive side detection element arranged in the Y-axis positive area and the Y-axis negative side detection element arranged in the Y-axis negative area are symmetrical with respect to both the XZ plane and the YZ plane. The Z-axis displacement detection element is arranged, and the X-axis positive side detection element and the X-axis negative side detection element are formed on the flexible support when the vibrator is displaced in the X-axis direction. Due to the bending that occurs, the detection signal having an absolute value corresponding to the displacement and having opposite polarities is output. The Y-axis positive detection element and the Y-axis negative detection element are arranged in the Y-axis direction. Due to the bending that occurs in the flexible support when it is displaced in the direction of The Z-axis displacement detection element has an absolute value corresponding to the displacement and a polarity corresponding to the displacement direction due to the bending that occurs in the flexible support when the vibrator is displaced in the Z-axis direction. The function to output the detection signal of
The detection circuit
A function of executing a periodic operation for the period T constituted by the first half period Tz and the second half period Tx;
In the first half cycle Tz, an AC signal having a predetermined frequency fz and amplitude Az is arranged, and in the second half cycle Tx, no AC signal is arranged, a Z-axis drive signal DrZ A Z-axis drive signal generator for generating
No AC signal is arranged in the first half cycle Tz, and an X-axis drive signal in which an AC signal having a predetermined frequency fx and amplitude Ax is arranged in the second half cycle Tx. An X-axis drive signal generator for generating DrX;
In the first half cycle Tz, a pulse having a pulse width equal to or less than ½ of the cycle of the Z-axis drive signal DrZ is periodically arranged at a position synchronized with the positive peak of the Z-axis drive signal DrZ. In the second half cycle Tx, pulses having a pulse width equal to or less than ½ of the cycle of the X-axis drive signal DrX are periodically arranged at a position synchronized with the positive peak of the X-axis drive signal DrX. A positive side synchronous detection signal generating unit for generating a positive side synchronous detection signal SdA;
In the first half cycle Tz, a pulse having a pulse width equal to or less than ½ of the cycle of the Z-axis drive signal DrZ is periodically arranged at a position synchronized with the negative peak of the Z-axis drive signal DrZ. In the second half cycle Tx, a pulse having a pulse width equal to or less than ½ of the cycle of the X-axis drive signal DrX is periodically arranged at a position synchronized with the negative peak of the X-axis drive signal DrX. A negative side synchronous detection signal generator for generating a negative side synchronous detection signal SdB;
A Z-axis detection enable signal generator for generating a Z-axis detection enable signal EnZ indicating a first stable vibration period βz that is expected to maintain a stable vibration state along the Z-axis in the first half period Tz. When,
X-axis detection enable signal generator for generating an X-axis detection enable signal EnX indicating a second stable vibration period βx that is expected to maintain a stable vibration state along the X-axis in the second half period Tx When,
In the first half cycle Tz, the Z-axis drive signal DrZ is supplied to all four sets of drive elements, and in the second half cycle Tx, the X-axis drive signal DrX is supplied to the X-axis positive drive element. A matrix converter for supplying and supplying a phase inversion signal of the X-axis drive signal DrX to the X-axis negative drive element;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable vibration period βz, the detection signal of the X axis positive detection element and the detection signal of the X axis negative detection element are A Y-axis angular velocity detector that outputs an electrical signal indicating the angular velocity ωy around the Y-axis based on the detected value indicating the difference;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable oscillation period βz, the detection signal of the Y axis positive detection element and the detection signal of the Y axis negative detection element are An X-axis angular velocity detector that outputs an electrical signal indicating an angular velocity ωx around the X axis based on a detected value indicating the difference;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable oscillation period βx, the detection signal of the Y axis positive detection element and the detection signal of the Y axis negative detection element are A Z-axis angular velocity detector that outputs an electrical signal indicating an angular velocity ωz around the Z-axis based on a detected value indicating the difference;
Z-axis amplitude for measuring the amplitude of the vibrator in the Z-axis direction based on the detected value indicating the displacement of the vibrator in the Z-axis direction obtained from the Z-axis displacement detection element during the first stable vibration period βz A measuring section;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable vibration period βz, a detection value indicating the displacement in the Z-axis direction of the vibrator obtained from the Z-axis displacement detection element is obtained. Based on the Z-axis phase measurement unit for measuring the phase of the vibrator in the Z-axis direction,
A detected value indicating the displacement of the vibrator in the X-axis direction obtained as a difference between the detection signal of the X-axis positive detection element and the detection signal of the X-axis negative detection element during the second stable vibration period βx An X-axis amplitude measurement unit that measures the amplitude of the vibrator in the X-axis direction,
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable oscillation period βx, the detection signal of the X axis positive detection element and the detection signal of the X axis negative detection element are An X-axis phase measurement unit that measures the phase of the vibrator in the X-axis direction based on a detection value indicating the displacement of the vibrator in the X-axis direction obtained as a difference;
Based on the amplitude measured by the Z-axis amplitude measurement unit and the phase measured by the Z-axis phase measurement unit, the frequency and amplitude of the Z-axis drive signal DrZ generated by the Z-axis drive signal generation unit are set to a predetermined reference frequency and reference. The feedback control is performed so as to obtain the amplitude, and the X-axis drive signal DrX generated by the X-axis drive signal generation unit is based on the amplitude measured by the X-axis amplitude measurement unit and the phase measured by the X-axis phase measurement unit. A feedback control unit that performs feedback control so that the frequency and amplitude become a predetermined reference frequency and reference amplitude;
Is provided.

(7) According to a seventh aspect of the present invention, in the angular velocity sensor according to the sixth aspect described above,
Matrix converter
A circuit that generates a sum signal “DrZ + DrX” and supplies the sum signal to the X-axis positive drive element;
A circuit that generates a difference signal “DrZ−DrX” and supplies the difference signal to the X-axis negative drive element;
A circuit for supplying “DrZ” to the Y-axis positive drive element;
A circuit for supplying “DrZ” to the Y-axis negative drive element;
It is made to have.

(8) According to an eighth aspect of the present invention, in the angular velocity sensor according to the fifth to seventh aspects described above,
Angular velocity detector
A positive-side integrator that integrates the signal value of the given signal only while the pulse of the positive-side synchronous detection signal is given;
A negative-side integrator that integrates the signal value of the given signal only while the pulse of the negative-side synchronous detection signal is given; and
A differentiator that outputs the difference between the accumulated value of the positive-side integrator and the accumulated value of the negative-side integrator;
And an electric signal corresponding to the difference obtained by the differentiator is output as a signal indicating the angular velocity.

(9) According to a ninth aspect of the present invention, in the angular velocity sensor according to the eighth aspect described above,
The angular velocity detection unit further includes a gate switch SW that passes the detection value only during the period of the stable vibration period and supplies the detection value to the synchronous detection circuit SD.

(10) According to a tenth aspect of the present invention, in the angular velocity sensor according to the fifth to ninth aspects described above,
Phase measurement unit
A positive-side integrator that integrates the signal value of the given signal only while the pulse of the positive-side synchronous detection signal is given;
A negative-side integrator that integrates the signal value of the given signal only while the pulse of the negative-side synchronous detection signal is given; and
A differentiator that outputs the difference between the accumulated value of the positive-side integrator and the accumulated value of the negative-side integrator;
And an electric signal corresponding to the difference obtained by the differentiator is output as a signal indicating a measured value of the phase.

(11) An eleventh aspect of the present invention is the angular velocity sensor according to the tenth aspect described above,
The phase measurement unit further includes a gate switch SW that passes the detected value only during the period of the stable vibration period and supplies the detected value to the synchronous detection circuit SD.

(12) According to a twelfth aspect of the present invention, in the angular velocity sensor according to the fifth to eleventh aspects described above,
The angular velocity detection unit has a function to hold the previous detection value when it is no longer in the stable vibration period, and continuously output the detection value held until the next stable vibration period comes It is a thing.

(13) According to a thirteenth aspect of the present invention, in the angular velocity sensor according to the fifth to twelfth aspects described above,
When the feedback control unit performs feedback control for each half cycle, control is performed so that the frequency of the drive signal is f0 when the resonance frequency of the vibrator in the vibration direction of the half cycle is f0. It is a thing.

(14) According to a fourteenth aspect of the present invention, in the angular velocity sensor according to the fifth to twelfth aspects described above,
When the feedback control unit performs feedback control for each half cycle and the resonance frequency of the vibrator in the vibration direction of the half cycle is f0, the frequency of the drive signal is a predetermined frequency in the vicinity of f0 (f0 is Except for the above control.

(15) According to a fifteenth aspect of the present invention, in the angular velocity sensor according to the thirteenth or fourteenth aspect described above,
The frequency at which the phase of the driving signal and the phase of the vibrator measured by the phase measuring unit cause a phase difference of 90 ° is regarded as the frequency f0, and the frequency control for the driving signal is performed. is there.

(16) According to a sixteenth aspect of the present invention, in the angular velocity sensor according to the first to fifteenth aspects described above,
The individual elements constituting the drive element group and the detection element group are made of piezoelectric elements fixed to the upper surface of the flexible support.

(17) According to a seventeenth aspect of the present invention, in the angular velocity sensor according to the first to fifteenth aspects described above,
The individual elements constituting the drive element group and the detection element group are constituted by a displacement electrode fixed on the upper surface of the flexible support and a fixed electrode fixed at a position facing the displacement electrode. It is made up of a capacitive element.

  According to the angular velocity sensor of the present invention, the displacement component based on the Coriolis force can be efficiently extracted only during the vibration stabilization period while the vibrator is vibrated alternately in two coordinate axis directions every half cycle. The angular velocity around the three axes can be detected with high accuracy by the time division detection operation.

It is a longitudinal cross-sectional view which shows the structure of the sensor main-body part of the angular velocity sensor using the piezoelectric element which concerns on one Embodiment of this invention, and the cross section which cut | disconnected the structure of FIG. 2 by XZ plane is shown. It is a top view which shows the structure of the sensor main-body part shown in FIG. 1 (hatching is for showing the shape of each electrode clearly, and does not show a cross section). It is a circuit diagram which shows the structure of the detection circuit of the angular velocity sensor which concerns on this invention. It is a wave form diagram which shows each operation signal output from the operation signal generator 100 in the detection circuit shown in FIG. It is a figure which shows the calculation function of the matrix converter 200 in the detection circuit shown in FIG. FIG. 4 is a circuit diagram illustrating a specific configuration example of a matrix converter 200 in the detection circuit illustrated in FIG. 3. FIG. 4 is a signal waveform diagram illustrating a driving operation of a vibrator in a state where an angular velocity is not acting by the detection circuit illustrated in FIG. 3. FIG. 4 is a circuit diagram showing a configuration example of a synchronous detection circuit SD in the detection circuit shown in FIG. 3. FIG. 4 is a waveform diagram showing signal waveforms when correct phase control is performed in the detection circuit shown in FIG. 3. FIG. 4 is a waveform diagram showing signal waveforms when the phase is delayed in the detection circuit shown in FIG. 3. FIG. 4 is a waveform diagram showing signal waveforms when the phase is advanced in the detection circuit shown in FIG. 3. FIG. 4 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 3 in a state where the angular velocity around the Y axis is not acting. FIG. 4 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 3 in a state where an angular velocity around the Y axis is acting. It is a signal waveform diagram explaining the general operation of the angular velocity sensor according to the present invention. It is a graph which shows the frequency characteristic of a general mechanical vibration system. It is a longitudinal cross-sectional view which shows the structure of the sensor main-body part using the capacitive element which concerns on another embodiment of this invention. FIG. 17 is a bottom view of the auxiliary substrate 60 of the sensor main body shown in FIG. 16.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<<< §1. Basic structure of sensor body >>
The angular velocity sensor according to the present invention includes a sensor main body and a detection circuit. Here, first, the basic structure of the sensor main body will be described. The sensor main body includes a vibrator, a flexible support and a fixing member that supports the vibrator, a drive element group that vibrates the vibrator, and a detection element group that detects displacement of the vibrator. ing.

  FIG. 1 is a longitudinal sectional view showing a structure of a sensor main body of an angular velocity sensor using a piezoelectric element according to an embodiment of the present invention. As shown in the figure, the sensor main body is composed of a flexible support 10, a vibrator 20, a fixing member 30, a piezoelectric element 40, and electrodes (elements having a symbol with E at the beginning). . Here, for convenience of explanation, the origin O is set at the center of gravity of the vibrator 20, the X axis is in the right direction in the figure, the Z axis is in the upward direction in the figure, and the Y axis is in the vertical direction in the drawing. We will define a coordinate system. This angular velocity sensor has a function of independently detecting an angular velocity ωx around the X axis, an angular velocity ωy around the Y axis, and an angular velocity ωz around the Z axis in the XYZ three-dimensional coordinate system.

  FIG. 2 is a top view showing the structure of the sensor body. Note that the X-axis, Y-axis, and origin O shown in FIG. 2 are not located on the upper surface of the sensor body, but are actually arranged at the position of the origin O shown in FIG. However, in the description of the electrode arrangement to be described later, in order to refer to the position of each electrode when projected onto the XY plane, in FIG. 2, a projected image on the XY plane is drawn for convenience. Further, in FIG. 2, in order to clearly show the shape of each electrode, the electrode portions are hatched (the hatching in FIG. 2 does not indicate a cross section). The longitudinal sectional view shown in FIG. 1 shows a cross section obtained by cutting the sensor main body shown in FIG. 2 along the XZ plane.

  The illustrated flexible support 10 is a flexible substrate having a square shape, and has an upper surface that passes through the Z axis at the center position and is parallel to the XY plane. As shown in FIG. 1, a columnar vibrator 20 is bonded to the center of the lower surface of the flexible support 10. Further, a fixing member 30 is joined around the lower surface of the flexible support 10, and the bottom surface thereof is fixed to a sensor housing (not shown). An annular groove G is formed between the vibrator 20 and the fixing member 30 so as to surround the vibrator 20, and a portion of the flexible support 10 positioned above the groove 20 is a thin plate-like member. And bends due to the action of external force.

  Above the flexible support 10, a drive element group and a detection element group are arranged. That is, as shown in FIG. 1, the common electrode Ec is formed on the upper surface of the flexible support 10, and the piezoelectric element 40 is disposed on the upper surface of the common electrode Ec. Twelve sets of individual electrodes are formed. As shown in FIG. 2, the piezoelectric element 40 is a disk-shaped element, and can be composed of, for example, piezoelectric ceramics such as PZT (lead zirconate titanate). The common electrode Ec is a disk-shaped electrode formed on the lower surface of the disk-shaped piezoelectric element, and a protrusion used for wiring is formed on the right side. The common electrode Ec shown by hatching in the top view of FIG. 2 is a portion of this protrusion, and actually the common electrode Ec extends over the entire lower surface of the disk-shaped piezoelectric element 40.

  The shape and arrangement of the 12 sets of individual electrodes formed on the upper surface of the piezoelectric element 40 are as shown in the top view of FIG. All of these 12 sets of individual electrodes are arranged above the annular groove G shown in FIG. In other words, the flexible support 10 is disposed in a portion where the bending is caused by the action of an external force.

  First, as the electrodes constituting the drive element group, when projected onto the XY plane, the X-axis positive drive electrode Ex (+) arranged in the X-axis positive region and the X-axis negative region are arranged. The X-axis negative drive electrode Ex (−) arranged, the Y-axis positive drive electrode Ey (+) arranged in the Y-axis positive area, and the Y-axis negative arranged in the Y-axis negative area Four sets of side drive electrodes Ey (−) are provided.

  On the other hand, as the electrodes constituting the detection element group, when projected on the XY plane, the X-axis positive detection electrode Ex1 arranged in the X-axis positive region and the X-axis negative region are arranged. 4 of X-axis negative side detection electrode Ex2, Y-axis positive side detection electrode Ey1 disposed in the Y-axis positive region, and Y-axis negative side detection electrode Ey2 disposed in the Y-axis negative region A set is provided, and further, Z-axis displacement detection electrodes Ez1 to Ez4 each including four electrodes are provided. Here, the four Z-axis displacement detection electrodes Ez1 to Ez4 are electrodes arranged so as to be symmetric with respect to both the XZ plane and the YZ plane.

  As shown in FIG. 2, in the case of the embodiment shown here, the overall electrode pattern consisting of a total of 12 individual electrodes is symmetrical with respect to both the XZ plane and the YZ plane. This is a consideration for ensuring symmetry in drive signals and detection signals described later. For example, if the X-axis positive drive electrode Ex (+) and the X-axis negative drive electrode Ex (−) have symmetry with respect to the YZ plane, drive signals having the same amplitude are supplied to both electrodes. By doing so, the vibrator can be vibrated around the origin O.

  In the example shown here, the four electrodes Ex (+), constituting the driving element group are arranged outside the eight electrodes Ex1, Ex2, Ey1, Ey2, Ez1 to Ez4 constituting the detection element group. Ex (-), Ey (+), and Ey (-) are arranged, but conversely, the electrodes constituting the driving element group are arranged on the inside and the electrodes constituting the detection element group are arranged on the outside. It doesn't matter.

  Here, each of the individual electrodes formed on the upper surface of the piezoelectric element 40, a part of the piezoelectric element 40 positioned below the individual electrode, and a part of the common electrode Ec positioned below the driving element or A detection element is formed. That is, in the piezoelectric sensor shown here, a piezoelectric element sandwiched between a pair of upper and lower electrodes constitutes one drive element or detection element.

  More specifically, the X-axis positive drive electrode Ex (+), a part of the piezoelectric element 40 below the X-axis positive drive electrode, and a part of the common electrode Ec below the X-axis positive drive electrode constitute an X-axis negative drive element. The side drive electrode Ex (−), a part of the piezoelectric element 40 below the side drive electrode Ex (−) and a part of the common electrode Ec below the side drive electrode constitute an X-axis negative side drive element, and the Y-axis positive side drive electrode Ey (+). And a portion of the piezoelectric element 40 below it and a portion of the common electrode Ec below it constitute a Y-axis positive drive element, and the Y-axis negative drive electrode Ey (−) and the piezoelectric element 40 below it. The Y-axis negative side driving element is constituted by a part and a part of the common electrode Ec below the part.

  Similarly, the X-axis positive side detection electrode Ex1, the part of the piezoelectric element 40 below it and the part of the common electrode Ec below it constitute an X-axis positive side detection element, and the X-axis negative side detection electrode Ex2 And a portion of the piezoelectric element 40 below it and a portion of the common electrode Ec below it constitute an X-axis negative detection element, a Y-axis positive detection electrode Ey1 and a portion of the piezoelectric element 40 below it, and The lower common electrode Ec constitutes a Y-axis positive detection element, and the Y-axis negative detection electrode Ey2, the lower piezoelectric element 40 and the lower common electrode Ec constitute a Y-axis. A negative-side detection element is configured, and the Z-axis displacement detection element is configured by the Z-axis displacement detection electrodes Ez1 to Ez4, a part of the piezoelectric element 40 therebelow and a part of the common electrode Ec therebelow.

  Here, for example, the characteristics of the piezoelectric element 40 such that when a positive voltage is applied to the upper surface and a negative voltage is applied to the lower surface, the piezoelectric element 40 expands along the XY plane, and when a negative voltage is applied to the upper surface and a positive voltage is applied to the lower surface, the piezoelectric element 40 contracts along the XY plane. (Or an element having completely opposite characteristics), the common electrode Ec is used as a ground reference potential, and a predetermined alternating current is applied to the X-axis positive drive electrode Ex (+). When a voltage is applied and an AC voltage having an opposite phase is applied to the X-axis negative drive electrode Ex (−), the X-axis positive side portion and the negative side portion of the flexible support 10 periodically expand and contract. And since the expansion / contraction state of both is always reversed, the vibrator 20 vibrates in the X-axis direction.

  Similarly, if a predetermined AC voltage is applied to the Y-axis positive drive electrode Ey (+) and an AC voltage having an opposite phase is applied to the Y-axis negative drive electrode Ey (−), the flexible support 10 Since the Y-axis positive side portion and the negative side portion periodically expand and contract, and the expansion / contraction state of both is always reversed, the vibrator 20 vibrates in the Y-axis direction. In addition, when an AC voltage having the same phase is applied to the four drive electrodes Ex (+), Ex (−), Ey (+), and Ey (−), each part expands and contracts at the same period, so that vibration occurs. The child 20 vibrates in the Z-axis direction.

  As described above, AC drive signals having various phases are supplied to some or all of the four drive electrodes Ex (+), Ex (−), Ey (+), and Ey (−). Thus, the vibrator can be vibrated in the X axis, the Y axis, and the Z axis. Of course, in a specific detection operation described later, only the vibration operation in the X-axis direction and the vibration operation in the Z-axis direction are performed, and the vibration operation in the Y-axis direction is not performed.

  The characteristics of the piezoelectric element can be arbitrarily set based on the polarity of the polarization treatment applied in the manufacturing process. Therefore, if different polarization treatments are applied to the individual portions of the disk-like piezoelectric element 40 shown in FIG. 2, the characteristics can be reversed for each portion. As described above, when a piezoelectric element whose characteristics are inverted for each portion is used, the phase of the AC signal supplied for driving is different from that in the above example.

  For example, in the region where the X-axis positive drive electrode Ex (+) is formed and the region where the X-axis negative drive electrode Ex (−) is formed, the piezoelectric elements 40 are polarized with opposite polarities. In the case where the processing has been performed, in order to vibrate the vibrator 20 in the X-axis direction, it is necessary to apply an AC voltage having the same phase to both electrodes Ex (+) and Ex (−) (the AC voltage having the same phase is applied). Even if it is added, since the characteristics are reversed, if one of the two stretches, the other shrinks). In this case, in order to vibrate the vibrator 20 in the Z-axis direction, it is necessary to apply an AC voltage having opposite phases to both electrodes Ex (+) and Ex (−).

  As described above, the phase of the AC drive signal supplied to each drive electrode needs to be determined depending on the polarization characteristics of the piezoelectric element in each drive electrode formation region. Will be described using a typical embodiment having the same polarization characteristics.

  On the other hand, on each detection electrode, a positive or negative voltage is generated with the common electrode Ec as the ground reference potential based on the stretched state of a part of the lower flexible support 10. For example, when the vibrator 20 is displaced in the X-axis direction, the expansion and contraction states of the flexible support 10 on the X-axis positive side portion and the negative-side portion are reversed, so that the X-axis positive side detection electrode Ex1 Voltages having opposite polarities are generated on the X-axis negative side detection electrode Ex2. At this time, the polarity of the generated voltage depends on the displacement direction of the vibrator, and the magnitude of the generated voltage depends on the displacement amount of the vibrator. Therefore, the detected value indicating the difference between the voltage generated at the X-axis positive side detection electrode Ex1 and the voltage generated at the X-axis negative side detection electrode Ex2 is the displacement in the X-axis direction of the vibrator 20 (the sign is the displacement direction, absolute The value is a value indicating the amount of displacement).

  Similarly, the detected value indicating the difference between the generated voltage of the Y-axis positive side detection electrode Ey1 and the generated voltage of the Y-axis negative side detection electrode Ey2 is a displacement in the Y axis direction of the vibrator 20 (the sign is the displacement direction, The absolute value is a value indicating displacement). In addition, regarding the displacement in the Z-axis direction, an equivalent voltage is generated in the four Z-axis displacement detection electrodes Ez1 to Ez4. Therefore, the detection value indicating the sum of the generated voltages of these four electrodes Ez1 to Ez4 is: This is a value indicating the displacement of the vibrator 20 in the Z-axis direction (the sign is the displacement direction, and the absolute value is the displacement amount). The displacement of the vibrator 20 in the Z-axis direction can also be detected as the sum of the voltages generated by the X-axis detection electrodes Ex1 and Ex2 and the Y-axis detection electrodes Ey1 and Ey2.

  As described above, by adding or subtracting the generated voltage of each of the detection electrodes Ex1, Ex2, Ey1, Ey2, Ez1 to Ez4, the displacement of the vibrator in each coordinate axis direction can be detected. The detected Coriolis force can also be detected as a displacement.

  After all, if the sensor main body shown here is used, the angular velocities ωx, ωy, and ωz around each coordinate axis can be detected by the following method. For example, if a displacement in the Y-axis direction (Coriolis force acting in the Y-axis direction) of the transducer 20 is detected in a state where the transducer 20 is vibrated in the X-axis direction, the displacement is an angular velocity ωz around the Z-axis. If the displacement of the vibrator 20 in the Z-axis direction (Coriolis force acting in the Z-axis direction) is detected, the displacement corresponds to the angular velocity ωy about the Y-axis.

  Similarly, if the displacement of the vibrator 20 in the X-axis direction (Coriolis force acting in the X-axis direction) is detected in a state where the vibrator 20 is vibrated in the Y-axis direction, the displacement is an angular velocity around the Z axis. If a displacement in the Z-axis direction of the vibrator 20 (Coriolis force acting in the Z-axis direction) is detected corresponding to ωz, the displacement corresponds to the angular velocity ωx around the X-axis. Further, if the displacement of the vibrator 20 in the X-axis direction (Coriolis force acting in the X-axis direction) is detected in a state where the vibrator 20 is vibrated in the Z-axis direction, the displacement is an angular velocity ωy around the Y-axis. If the displacement of the vibrator 20 in the Y-axis direction (Coriolis force acting in the Y-axis direction) is detected, the displacement corresponds to the angular velocity ωx around the X-axis. The detection circuit described in §2 is a circuit for performing such a detection operation.

<<< §2. Configuration of detection circuit >>
FIG. 3 is a circuit diagram showing a configuration of a detection circuit of the angular velocity sensor according to the present invention. This detection circuit detects the displacement of the vibrator 20 in the predetermined coordinate axis direction while supplying the predetermined drive signal to the sensor main body described in §1 to vibrate the vibrator 20 in the predetermined coordinate axis direction. Thus, the electric signal indicating the angular velocity around the predetermined coordinate axis is output. The detection circuit also functions to perform feedback control so as to maintain the reference vibration state while monitoring the vibration state of the vibrator.

  Note that the sensor main body 300 shown in the center of FIG. 3 is not actually a component of the detection circuit, but represents the sensor main body described in §1. That is, Ex (+), Ex (−), Ey (+), and Ey (−) shown near the upper side of the block of the sensor main body 300 in FIG. This corresponds to the electrodes Ex (+), Ex (−), Ey (+), Ey (−). Similarly, Ex1, Ex2, Ey1, Ey2, and Ez1 to Ez4 shown in the vicinity of the lower side of the block of the sensor body 300 in FIG. 3 are the eight detection electrodes Ex1, Ex2, Ey1, and E1 shown in FIG. This corresponds to Ey2, Ez1 to Ez4. 3 corresponds to the common electrode Ec shown in FIG. 2, and this common electrode Ec is grounded as shown.

  Hereinafter, each component of the detection circuit will be described in order. First, the operation signal generator 100 has a function of generating a drive signal supplied to the sensor main body 300 and various signals supplied to other circuit elements. The operation signal generator 100 includes a feedback control unit 110 and signal generation units 120, 130, 140, 150, 160, and 170 as depicted in the block of the figure.

  FIG. 4 is a waveform diagram showing each operation signal output from the operation signal generator 100. The detection circuit according to the present invention has a function of executing a periodic operation for a period T constituted by a first half period T1 and a second half period T2. In particular, in the embodiment shown here, the first half cycle T1 is a period in which detection is performed while vibrating the transducer 20 in the Z-axis direction, and the second half cycle T2 is performed in the X-axis direction. Since detection is performed while vibrating, the first half cycle T1 is hereinafter referred to as half cycle Tz, and the second half cycle T1 is referred to as half cycle Tx. FIG. 4 (1) shows a period of the half cycle Tz and a period of the half cycle Tx on the time axis. Both the half periods Tz and Tx constitute one period T of the detection circuit, and the detection circuit performs a periodic operation with such a period T.

  In the embodiment shown here, T is set to 12.5 ms, and the periodic operation is repeatedly executed at a frequency of 80 Hz. In addition, since setting is made so that each half cycle is equal, Tz = Tx = 6.25 ms. Of course, the half periods Tz and Tx are not necessarily set equal. As will be described later, in practice, the value of the period T is preferably set to an optimum value according to the resonance frequency of the vibrator. For example, in the case of a sensor in which the resonance frequency in the Z-axis direction and the resonance frequency in the X-axis direction of the vibrator are substantially equal, the resonance frequency is f0 and the period T is (1 / f0) × 200 to (1 / f0) ×. If the range is set to 500, good detection is possible (details will be described in §6).

  The Z-axis drive signal generator 150 in the operation signal generator 100 has a function of generating a Z-axis drive signal DrZ for vibrating the vibrator 20 in the Z-axis direction. As shown in FIG. 4 (2), the Z-axis drive signal DrZ includes an AC signal having a predetermined frequency fz and amplitude Az in the first half cycle Tz, and the second half cycle Tx. Is a signal to which no AC signal is arranged. On the other hand, the X-axis drive signal generator 140 has a function of generating an X-axis drive signal DrX for vibrating the vibrator 20 in the X-axis direction. As shown in FIG. 4 (3), the X-axis drive signal DrX has no AC signal arranged in the first half cycle Tz, and the second half cycle Tx has a predetermined frequency fx and An AC signal having an amplitude Ax is provided.

  In the case of the embodiment shown here, it is set so that fz = fx = about 20 kHz and Az = Ax = 1.0 V. In FIG. 4, for convenience of illustration, only five cycles of each drive signal are drawn within a period of one half cycle Tz or Tx. However, in the case of the above numerical setting, actually, one half cycle Tz. Alternatively, 125 periods of each drive signal are included in the period of Tx. The same applies to a positive side synchronous detection signal SdA and a negative side synchronous detection signal SdB described later.

  The frequencies and amplitudes of the Z-axis drive signal DrZ and the X-axis drive signal DrX are controlled by the feedback control unit 110 and are adjusted as needed based on the deviation between the feedback signal and a predetermined reference value, as will be described later. Note that the frequencies fz and fx need not be set to be equal, and similarly, the amplitudes Az and Ax need not be set to be equal. In the illustrated example, the amplitudes Az and Ax of the drive signals DrZ and DrX are always maintained at constant values, but the amplitudes Az and Ax are not necessarily maintained at constant values. It may be devised to control the vibrator to increase the initial amplitude and stabilize the movement of the vibrator quickly. These drive signals DrX, DrZ are given to the drive electrodes Ex (+), Ex (−), Ey (+), Ey (−) of the sensor main body 300 via the matrix converter 200.

  As described above, the matrix converter 200 uses the X-axis drive signal DrX and the Z-axis drive signal DrZ supplied from the X-axis drive signal generator 140 and the Z-axis drive signal generator 150 in the operation signal generator 100 as the sensor body. The process given to the specific drive electrodes Ex (+), Ex (−), Ey (+), Ey (−) of the unit 300 is executed. The specific operation will be described later.

  On the other hand, the positive-side synchronous detection signal generator 160 has a function of generating a positive-side synchronous detection signal SdA composed of pulses synchronized with the positive-side peaks of the drive signals DrX and DrZ. The generation unit 170 has a function of generating a negative side synchronous detection signal SdB composed of pulses synchronized with the negative side peaks of the drive signals DrX and DrZ.

  More specifically, as shown in FIG. 4 (4), the positive side synchronous detection signal SdA is Z-axis driven at a position synchronized with the positive peak of the Z-axis drive signal DrZ in the first half period Tz. Pulses having a pulse width equal to or less than ½ of the period of the signal DrZ are periodically arranged, and in the second half period Tx, the X-axis drive is performed at a position synchronized with the positive peak of the X-axis drive signal DrX. This is a signal in which pulses having a pulse width of 1/2 or less of the period of the signal DrX are periodically arranged. Further, as shown in FIG. 4 (5), the negative side synchronous detection signal SdB has a cycle of the Z-axis drive signal DrZ at a position synchronized with the negative peak of the Z-axis drive signal DrZ in the first half cycle Tz. Of the X-axis drive signal DrX is periodically arranged at a position synchronized with the negative peak of the X-axis drive signal DrX in the second half-cycle Tx. This is a signal in which pulses having a pulse width less than or equal to 1/2 are periodically arranged.

  The center position of the pulse on the time axis of each of the synchronous detection signals SdA and SdB matches the peak position of each drive signal. The pulse width may be set to a value that is ½ or less of the cycle of each drive signal, but in the embodiment shown here, it is set to about ¼ of the cycle of each drive signal. . These synchronous detection signals SdA and SdB are given to all synchronous detectors SD.

  The Z-axis detection enable signal generation unit 130 has a function of generating a Z-axis detection enable signal EnZ indicating a period in which the vibration of the vibrator 20 in the Z-axis direction is stable and detection processing is possible. The detection enable signal generation unit 120 has a function of generating an X-axis detection enable signal EnX that indicates a period during which the vibration in the X-axis direction of the transducer 20 is stable and detection processing is possible.

  That is, as shown in FIG. 4 (6), the Z-axis detection enable signal EnZ is a first stable vibration that is expected to maintain a stable vibration state along the Z-axis in the first half period Tz. It is a signal indicating the period βz. Here, the illustrated period αz is a first unstable vibration period in which the vibration state of the vibrator 20 in the Z-axis direction is expected to be unstable in the first half period Tz. On the other hand, as shown in FIG. 4 (7), the X-axis detection enable signal EnX is a second stable vibration that is expected to maintain a stable vibration state along the X-axis in the second half period Tx. It is a signal indicating the period βx. Here, the illustrated period αx is a second unstable vibration period in which the vibration state of the vibrator 20 in the X-axis direction is expected to be unstable in the second half period Tx.

  As already described, in the embodiment shown here, the vibrator 20 is driven along the Z axis in the first half cycle Tz, and the vibrator 20 is driven along the X axis in the second half cycle Tx. Is done. However, since the vibrator 20 is an object supported by a mechanical structure called the flexible support body 10, the driving direction changes from the Z-axis to the X-axis or from the X-axis to the Z-axis in a half cycle. Even if the operation of switching 90 ° is performed every time, the actual vibration direction is not immediately switched, so that the actual vibration immediately after switching becomes unstable. The time required for the vibration state to stabilize is a parameter determined depending on the mechanical structure of each sensor main body. Therefore, the unstable vibration periods αz and αx for the sensor body can be obtained by measurement using the actual sensor body (or by computer simulation).

  Of course, each half cycle Tz, Tx must be set to a period longer than these unstable oscillation periods αz, αx. In the example shown here, αz = αx = 2.5 ms. Therefore, when Tz = Tx = 6.25 ms is set, βz = βx = 3.75 ms. These detection enable signals EnX and EnZ are signals indicating periods of stable oscillation periods βz and βx in which accurate detection is possible, and are respectively given to specific gate switches SW.

  As described above, in FIG. 3, the element drawn above the sensor main body 300 is a circuit that performs processing for driving the vibrator 20 in the detection circuit. Due to the action of this circuit, the vibrator 20 of the sensor main body vibrates in the Z-axis direction during the first half period Tz and vibrates in the X-axis direction during the second half period Tx. Next, a circuit that performs processing for detecting displacement of the vibrator 20 in a state where the vibrator 20 is vibrating will be described. This circuit is composed of elements drawn below the sensor main body 300 in FIG.

  First, the differentiator 411 functions to obtain a difference between the voltage generated at the X-axis positive detection electrode Ex1 and the voltage generated at the X-axis negative detection electrode Ex2. As described above, the signal SΔx indicating the difference becomes a detection value indicating the displacement of the vibrator 20 in the X-axis direction, and is referred to as an X-axis displacement detection signal SΔx here. Similarly, the differentiator 412 functions to obtain a difference between the voltage generated at the Y-axis positive detection electrode Ey1 and the voltage generated at the Y-axis negative detection electrode Ey2. As described above, the signal SΔy indicating this difference becomes a detection value indicating the displacement of the vibrator 20 in the Y-axis direction, and is referred to as a Y-axis displacement detection signal SΔy here.

  The adder 413 functions to obtain the sum of the voltages generated in the four Z-axis displacement detection electrodes Ez1 to Ez4. Since the signal SΔz indicating the sum is a detection value indicating the displacement of the vibrator 20 in the Z-axis direction as described above, it is referred to as a Z-axis displacement detection signal SΔz here.

  The X-axis displacement detection signal SΔx output from the difference unit 411 is supplied to the AM detector 431 and the synchronous detector 441 through the gate switch 421, and is supplied to the synchronous detector 442 through the gate switch 422. Similarly, the Y-axis displacement detection signal SΔy output from the subtractor 412 is supplied to the synchronous detector 443 through the gate switch 423 and is supplied to the synchronous detector 444 through the gate switch 424. The Z-axis displacement detection signal SΔz output from the adder 413 is given to the synchronous detector 445 and the AM detector 432 through the gate switch 425.

  Here, the gate switches 421 and 424 are stable only during the stable oscillation period βx indicated by the X-axis detection enable signal EnX generated by the X-axis detection enable signal generator 120 (that is, the vibration in the X-axis direction is stable). And only during a period in which the detection process is enabled), the input detection value is passed and output. On the other hand, the gate switches 422, 423, and 425 are operated only during the stable oscillation period βz indicated by the Z-axis detection enable signal EnZ generated by the Z-axis detection enable signal generation unit 130 (that is, vibration in the Z-axis direction is not generated). Only during a period when the detection process is stable and stable), the input detection value is passed and output. Therefore, the AM detectors 431 and 432 and the synchronous detectors 441 to 445 are given a signal indicating a predetermined detection value only during the stable oscillation period, and detection is performed only during the period.

  The AM detector 431 performs a function of obtaining the amplitude of the X-axis displacement detection signal SΔx, and the obtained X-axis amplitude measurement value Fxa is fed back to the feedback control unit 110, and the AM detector 432 receives the Z-axis displacement detection signal SΔz. The function of obtaining the amplitude is performed, and the obtained Z-axis amplitude measurement value Fza is fed back to the feedback control unit 110. On the other hand, the synchronous detector 441 functions to obtain the phase of the X-axis displacement detection signal SΔx, and the obtained X-axis phase measurement value Fxp is fed back to the feedback control unit 110, and the synchronous detector 445 receives the Z-axis displacement detection signal. The function of obtaining the phase of SΔz is achieved, and the obtained Z-axis phase measurement value Fzp is fed back to the feedback control unit 110.

  The synchronous detector 442 has a function of obtaining the Coriolis force in the X-axis direction applied to the transducer 20 based on the X-axis displacement detection signal SΔx during the first half period Tz in which the transducer 20 is vibrating in the Z-axis direction. The obtained value is output as the angular velocity ωy about the Y axis. On the other hand, the synchronous detector 443 obtains the Coriolis force in the Y-axis direction that has acted on the vibrator 20 based on the Y-axis displacement detection signal SΔy during the first half period Tz in which the vibrator 20 vibrates in the Z-axis direction. The function is performed, and the obtained value is output as the angular velocity ωx around the X axis. The synchronous detector 444 obtains the Coriolis force in the Y-axis direction that has acted on the transducer 20 based on the Y-axis displacement detection signal SΔy during the latter half period Tx in which the transducer 20 vibrates in the X-axis direction. The function is performed, and the obtained value is output as the angular velocity ωz around the Z axis.

  The feedback control unit 110 determines the amplitude and frequency of the X-axis drive signal DrX generated by the X-axis drive signal generation unit 140 based on the X-axis amplitude measurement value Fxa and the X-axis phase measurement value Fxp that are fed back. The feedback control is performed so that the amplitude and the reference frequency are obtained, and the amplitude of the Z-axis drive signal DrZ generated by the Z-axis drive signal generator 150 based on the Z-axis amplitude measurement value Fza and the Z-axis phase measurement value Fzp that are fed back. Further, feedback control is performed so that the frequency becomes a predetermined reference amplitude and reference frequency. By such feedback control, the vibrator 20 vibrates in the X-axis direction and the Z-axis direction with a predetermined reference amplitude and a predetermined reference frequency, respectively. Since the synchronous detection signals SdA and SdB are signals synchronized with the drive signals DrX and DrZ, the frequency of the synchronous detection signals SdA and SdB generated by the synchronous detection signal generation units 160 and 170 is also determined by the feedback control unit 110. You will receive frequency control.

  Thus, when the detection circuit shown in FIG. 3 is used, the vibrator 20 is vibrated in the Z-axis direction in the first half cycle Tz and repeatedly in the X-axis direction in the second half cycle Tx. The synchronous detector 442 outputs an electrical signal indicating the angular velocity ωy around the Y axis, and the synchronous detector 443 outputs an electrical signal indicating the angular velocity ωx around the X axis. In the second half period Tx, the synchronous detector 444 is output. To output an electrical signal indicating the angular velocity ωz around the Z-axis. In addition, since the detection values indicated by these output signals are values obtained during the stable oscillation periods βz and βx indicated by the detection enable signals EnZ and EnX, they are accurate and accurate detection values.

<<< §3. Oscillator movement >>>
Next, here, the movement of the vibrator 20 driven using the detection circuit shown in FIG. 3 will be described in detail. As described above, the operation signal generator 100 supplies the matrix converter 200 with the Z-axis drive signal DrZ as shown in FIG. 4 (2) and the X-axis drive signal DrX as shown in FIG. 4 (3). Is done.

  The matrix converter 200 uses these two drive signals DrZ and DrX to vibrate the vibrator 20 in the Z-axis direction during the first half cycle Tz, and the second half cycle Tx. Is operated to vibrate in the X-axis direction. Specifically, in the first half cycle Tz, all four sets of driving elements (four driving electrodes Ex (+), Ex (−), Ey (+), Ey (−)) are included. The Z-axis drive signal DrZ is supplied, and in the second half period Tx, the X-axis drive signal DrX is supplied to the X-axis positive drive element (X-axis positive drive electrode Ex (+)), and the X-axis A phase inversion signal of the X-axis drive signal DrX is supplied to the negative drive element (X-axis negative drive electrode Ex (−)).

  In order to perform such a driving operation, the matrix converter 200 performs an X-axis positive drive signal Dx (+), an X-axis negative drive signal Dx (−), and a Y-axis positive side by calculation as shown in FIG. It has a function of generating a drive signal Dy (+) and a Y-axis negative drive signal Dy (−). Here, the X-axis positive drive signal Dx (+) is a sum signal of the Z-axis drive signal DrZ and the X-axis drive signal DrX, and the X-axis positive drive element (X-axis positive drive electrode Ex ( +)). The X-axis negative drive signal Dx (−) is a difference signal between the Z-axis drive signal DrZ and the X-axis drive signal DrX, and is an X-axis negative drive element (X-axis negative drive electrode Ex (− )). On the other hand, the Y-axis positive drive signal Dy (+) and the Y-axis negative drive signal Dy (-) are both the Z-axis drive signal DrZ itself, and are respectively Y-axis positive drive elements (Y-axis positive drive). Electrode Ex (+)) and the Y-axis negative drive element (Y-axis negative drive electrode Ex (-)).

  FIG. 6 is a circuit diagram showing a specific configuration example of the matrix converter 200. When the Z-axis drive signal DrZ and the X-axis drive signal DrX supplied from the operation signal generator 100 are input to the two terminals on the left side of the figure, the drive signals Dx (+) are respectively output from the four terminals on the left side of the figure. , Dx (−), Dy (+), and Dy (−) are output. This circuit includes four OP amplifiers 210 to 240 and resistors R1 to R10.

  Here, the OP amplifier 210 is a circuit that generates a sum signal Dx (+) of “DrZ + DrX” and supplies it to the X-axis positive drive element (X-axis positive drive electrode Ex (+)). The amplifiers 220 and 240 are circuits that generate a difference signal Dx (−) of “DrZ−DrX” and supply it to the X-axis negative drive element (X-axis negative drive electrode Ex (−)). Further, the OP amplifier 230 converts “DrZ” into the Y-axis positive drive element (Y-axis positive drive electrode Ey (+)) and the Y-axis negative drive element (Y-axis negative drive electrode Ey (−) )) And a circuit supplied to both.

  After all, the drive signals Dx (+), Dx (−), Dy (+), and Dy (−) shown on the right side of each equation in FIG. 5 and each right terminal in FIG. It is given to the electrodes Ex (+), Ex (−), Ey (+), Ey (−), respectively. In this case, let us consider how the vibrator 20 moves by dividing it into a first half cycle Tz and a second half cycle Tx.

  First, during the period of the first half cycle Tz, as shown in FIG. 4, the X-axis drive signal DrX does not have an effective component as a substantial signal. This means only the signal DrZ. Therefore, with the common electrode Ec shown in FIG. 2 grounded, each of the four drive electrodes Ex (+), Ex (−), Ey (+), Ey (−) is shown in FIG. 4 (2). Since the AC signal of the Z-axis drive signal DrZ shown is supplied, the vibrator 20 vibrates in the Z-axis direction in synchronization with the AC signal as described in §1.

  On the other hand, during the period of the second half cycle Tx, as shown in FIG. 4, the Z-axis drive signal DrZ does not have an effective component as a substantial signal. This means only the signal DrX. Therefore, with the common electrode Ec shown in FIG. 2 grounded, the AC signal of the Z-axis drive signal DrZ shown in FIG. 4 (3) is supplied to the X-axis positive drive electrode Ex (+), and the X-axis negative drive electrode Ex (+) is supplied. Since the inverted signal is supplied to the side drive electrode Ex (−), the vibrator 20 vibrates in the X-axis direction in synchronization with the AC signal as described in section 1 above.

  Thus, the matrix converter 200 vibrates the vibrator 20 in the Z-axis direction during the first half cycle Tz and in the X-axis direction during the second half cycle Tx. become.

  In the detection circuit shown in FIG. 3, the displacements of the vibrator 20 in the coordinate axis directions can be detected as displacement detection signals SΔx, SΔy, SΔz, respectively. For example, the X-axis displacement detection signal SΔx is a signal output from the differentiator 411 and corresponds to the difference between the voltage generated at the X-axis positive detection electrode Ex1 and the voltage generated at the X-axis negative detection electrode Ex2. Signal. When the vibrator 20 is not displaced in the X-axis direction (that is, when the center of gravity of the vibrator 20 is located on the YZ plane), the potentials of both electrodes Ex1 and Ex2 are equal, so SΔx = 0. When the vibrator 20 is displaced in the X-axis direction, the expansion and contraction states of the piezoelectric elements located below the electrodes Ex1 and Ex2 are opposite to each other, and thus voltages having opposite polarities are generated on the electrodes Ex1 and Ex2. A signal SΔx corresponding to the difference is output as a positive or negative value. Therefore, the absolute value of the detection signal SΔx indicates the displacement amount of the vibrator 20 in the X-axis direction, and the sign of the detection signal SΔx indicates the displacement direction (X-axis positive direction or negative direction).

  Similarly, the Y-axis displacement detection signal SΔy is a signal output from the differentiator 412 and corresponds to the difference between the voltage generated at the Y-axis positive detection electrode Ey1 and the voltage generated at the Y-axis negative detection electrode Ey2. Signal. Again, the absolute value of the detection signal SΔy indicates the displacement amount of the vibrator 20 in the Y-axis direction, and the sign of the detection signal SΔy indicates the displacement direction (whether the Y-axis is positive or negative). The Z-axis displacement detection signal SΔz is a signal output from the adder 413 and is a signal corresponding to the sum of the voltages generated by the four Z-axis displacement detection electrodes Ez1 to Ez4. Again, the absolute value of the detection signal SΔz indicates the amount of displacement of the transducer 20 in the Z-axis direction, and the sign of the detection signal SΔz indicates the displacement direction (whether the Y-axis is positive or negative).

  FIG. 7 is a signal waveform diagram for explaining the driving operation of the vibrator in the state where the angular velocity is not acting by the detection circuit shown in FIG. As shown in FIG. 7 (1), the period T is composed of a first half period Tz and a second half period Tx. Then, during the period of the first half cycle Tz, the vibrator 20 is driven in the Z axis direction by the supply of the Z axis drive signal DrZ shown in FIG. 7 (2), and the period of the second half cycle Tx is as shown in FIG. The vibrator 20 is driven in the X-axis direction by supplying the X-axis drive signal DrX shown in 7 (3).

  On the other hand, FIG. 7 (4) shows the waveform of the Z-axis displacement detection signal SΔz output from the adder 413 when such a driving operation is performed. This detection signal SΔz indicates the transition of the position of the vibrator 20 with respect to the Z axis. The transition of the position of the vibrator 20 is due to the supply of the Z-axis drive signal DrZ shown in FIG. 7 (2). However, the mechanical vibration system comprising the vibrator 20 and the flexible support 10 that supports the vibrator 20 is changed. Due to the inherent characteristics, the actual displacement of the vibrator 20 causes a phase lag with respect to the Z-axis drive signal DrZ. As will be described later, when the vibrator 20 is vibrated at a resonance frequency in the Z-axis direction, the actual displacement of the vibrator 20 causes a phase delay of 90 ° with respect to the Z-axis drive signal DrZ. This is why the phase of the detection signal SΔz shown in FIG. 7 (4) has a phase lag with respect to the drive signal DrZ shown in FIG. 7 (2).

  Further, the amplitude Az of the drive signal DrZ shown in FIG. 7 (2) is constant, whereas the amplitude of the detection signal SΔz shown in FIG. This is because inertia acts on 20. That is, even if the supply of the AC signal in the drive signal DrZ is started from the beginning of the first half cycle Tz, the vibrator 20 that is stationary in the Z-axis direction starts to vibrate in the Z-axis direction. It will take some time. For this reason, the amplitude gradually increases during the first unstable vibration period αz shown in the figure. The illustrated first stable vibration period βz is a period after the vibrator 20 starts a stable vibration operation with a constant amplitude.

  Subsequently, at the end of the first half cycle Tz, the supply of the AC signal in the drive signal DrZ is stopped. For this reason, during the period of the second half cycle Tx, a signal for driving the transducer 20 in the Z-axis direction is not supplied. However, the vibrator 20 in motion maintains the vibration state in the Z-axis direction for a while while gradually decreasing the amplitude due to the inertial action. This is why the amplitude of the detection signal SΔz shown in FIG. 7 (4) remains at the beginning of the half cycle Tx.

  Eventually, the amplitude of the Z-axis displacement detection signal SΔz reaches a constant value while gradually increasing from the beginning of the first half cycle Tz, as shown by the dashed-dotted envelope in FIG. 7 (4). It disappears while gradually decreasing from the beginning of the half cycle Tx. Here, the period αz is a first unstable vibration period in which the vibration is unstable while being the first half period Tz, and the period βz is a stable vibration within the first half period Tz. This is the first stable vibration period obtained. As described above, the Z-axis detection enable signal EnZ shown in FIG. 4 (6) is a signal indicating the first stable oscillation period βz.

  Similarly, FIG. 7 (5) shows the waveform of the X-axis displacement detection signal SΔx output from the differentiator 411. This detection signal SΔx indicates a change in position of the vibrator 20 with respect to the X axis. The transition of the position of the vibrator 20 is due to the supply of the X-axis drive signal DrX shown in FIG. 7 (3). However, the mechanical vibration system comprising the vibrator 20 and the flexible support 10 that supports the vibrator 20 is changed. Due to the inherent characteristics, the actual displacement of the vibrator 20 causes a phase lag with respect to the X-axis drive signal DrX. Again, when the vibrator 20 is vibrated at a resonance frequency in the X-axis direction, the actual displacement of the vibrator 20 causes a phase delay of 90 ° with respect to the X-axis drive signal DrX.

  Further, the amplitude of the detection signal SΔx shown in FIG. 7 (5) reaches a constant value while gradually increasing from the beginning of the second half cycle Tx, as shown by the dashed-dotted envelope, and the first half cycle The disappearance while gradually decreasing from the beginning of Tz is due to the inertial action of the vibrator 20. Here, the period αx is a second unstable vibration period in which the vibration is unstable while being in the second half period Tx, and the period βx is a stable vibration in the second half period Tx. This is the second stable vibration period obtained. As described above, the X-axis detection enable signal EnX shown in FIG. 4 (7) is a signal indicating the second stable oscillation period βx.

  FIG. 7 (6) shown at the end shows the waveform of the Y-axis displacement detection signal SΔy output from the differentiator 412. The detection signal SΔy indicates a change in position of the vibrator 20 with respect to the Y axis. In the embodiment shown here, the vibrator 20 is not vibrated in the Y-axis direction. Therefore, when the angular velocity is not acting, the Y-axis displacement detection signal SΔy remains zero as shown in the figure. Will remain.

  As described above, the stable vibration periods βz and βx for each sensor can be obtained by measurement using an actual sensor body or by computer simulation. In FIG. 7, for convenience of illustration, only five cycles of each drive signal and each detection signal are drawn within a period of one half cycle Tz or Tx. A greater number of cycles of each drive signal and each detection signal (125 cycles in the above example) are included in the period.

<<< §4. Detection of amplitude and phase and Coriolis force >>>
As described in §2, in the detection circuit shown in FIG. 3, the elements drawn below the sensor main body 300 (elements with reference numerals in the 400s) are in the Z-axis or X-axis direction of the vibrator 20. And the Coriolis force in the X-axis, Y-axis, and Z-axis directions acting on the vibrator 20. Hereinafter, each of these detection functions will be described individually.

  First, the X-axis detection enable signal EnX shown in FIG. 4 (7) is given to the gate switch 421, and the given X-axis displacement detection signal SΔx is allowed to pass only during the second stable oscillation period βx. Fulfills the function. Similarly, the Z-axis detection enable signal EnZ shown in FIG. 4 (6) is given to the gate switch 422, and passes the given X-axis displacement detection signal SΔx only during the first stable oscillation period βz. Fulfills the function of The Z-axis detection enable signal EnZ shown in FIG. 4 (6) is given to the gate switch 423, and the given Y-axis displacement detection signal SΔy is allowed to pass only during the first stable oscillation period βz. Fulfills the function. Further, the X-axis detection enable signal EnX shown in FIG. 4 (7) is given to the gate switch 424, and the given Y-axis displacement detection signal SΔy is allowed to pass only during the second stable oscillation period βx. Fulfills the function. The gate switch 425 is supplied with the Z-axis detection enable signal EnZ shown in FIG. 4 (6), and passes the applied Z-axis displacement detection signal SΔz only during the first stable oscillation period βz. Fulfills the function.

  Next, functions of the AM detectors 431 and 432 will be described. First, the AM detector 431 obtains the amplitude Fxa of the X-axis displacement detection signal SΔx given only during the second stable oscillation period βx through the gate switch 421. Specifically, the amplitude Fxa of the stable oscillation period βx of the detection signal SΔx shown in FIG. 7 (5) is obtained. The amplitude Fxa obtained in this way is fed back to the feedback controller 110 as an X-axis amplitude measurement signal. Similarly, the AM detector 432 obtains the amplitude Fza of the Z-axis displacement detection signal SΔz given through the gate switch 425 only during the first stable oscillation period βz. Specifically, the amplitude Fza of the stable oscillation period βz of the detection signal SΔz shown in FIG. 7 (4) is obtained. The amplitude Fza thus obtained is fed back to the feedback control unit 110 as a Z-axis amplitude measurement signal.

  As described above, the AM detectors 431 and 432 are circuits that perform the function of obtaining the amplitude Fxa of the detection signal SΔx and the amplitude Fza of the detection signal SΔz, but there are various circuits for obtaining the amplitude of a general AC signal. Since this is a known circuit used in the field, a detailed description of the internal configuration of the AM detectors 431 and 432 is omitted here.

  Since the amplitude Fxa of the X-axis displacement detection signal SΔx corresponds to the vibration amplitude in the X-axis direction of the vibrator 20, the feedback control unit 110 determines that the amplitude Fxa is a predetermined reference amplitude. Control for adjusting the amplitude of the X-axis drive signal DrX generated by the generator 140 is performed. In addition, since the amplitude Fza of the Z-axis displacement detection signal SΔz corresponds to the amplitude of vibration in the Z-axis direction of the vibrator 20, the feedback control unit 110 sets the Z-axis displacement so that the amplitude Fza becomes a predetermined reference amplitude. Control for adjusting the amplitude of the Z-axis drive signal DrZ generated by the drive signal generator 150 is performed.

  On the other hand, all of the synchronous detectors 441 to 445 are configured by the circuit shown in FIG. Actually, the synchronous detectors 441 and 445 are used for obtaining the phases Fxp and Fzp of the detection signals SΔx and SΔz, and the synchronous detectors 442, 443 and 444 are based on the detection signal SΔx or SΔy, and the X axis Coriolis force acting in the direction or the Y-axis direction is detected, and finally, it is used for obtaining angular velocities ωy, ωx, and ωz, respectively. As described above, the synchronous detectors 441 and 445 and the synchronous detectors 442, 443, and 444 have different uses, but can be configured by the same circuit shown in FIG.

  The circuit shown in FIG. 8 has a function of outputting an output signal Sout from the right terminal in the drawing based on the input signal Sin given to the left terminal in the drawing. As shown in the figure, this circuit includes a positive-side integrator K1, a negative-side integrator K2, and a differentiator K3.

  The positive side accumulator K1 includes a gate switch Ga that allows a signal to pass only while the pulse of the positive side synchronous detection signal SdA is applied, and resistors R11 to R13 and capacitors C1 to C3 for accumulating the passed signals. The amplifier OP1 is configured to integrate the signal value of the given input signal Sin only while the pulse of the positive side synchronous detection signal SdA is given.

  Similarly, the negative-side integrator K2 includes a gate switch Gb that allows a signal to pass only while the pulse of the negative-side synchronous detection signal SdB is applied, resistors R14 to R16, and capacitors C4 to C4 that integrate the passed signals. C6 is configured by an operational amplifier OP2, and performs a function of integrating the signal value of the given input signal Sin only while the pulse of the negative side synchronous detection signal SdB is given.

  On the other hand, the differencer K3 is composed of a differential amplifier DIF to which a reference voltage Ref is applied, a resistor R17, and a capacitor C7, and outputs a difference between the integrated value of the positive integrator K1 and the integrated value of the negative integrator K2. Fulfills the function of

  Here, when the circuit shown in FIG. 8 is used as the synchronous detector 445 shown in FIG. 3 and the Z-axis displacement detection signal SΔz is given as the input signal Sin, the output signal Sout obtained from this circuit becomes the Z-axis displacement. The reason why the signal indicates the measured value of the phase of the detection signal SΔz will be briefly described.

  FIG. 9 is a waveform diagram showing signal waveforms when correct phase control is performed in the detection circuit shown in FIG. As shown in FIG. 9 (1), the time axis in this figure shows a part of the stable oscillation period βz in the first half period Tz. During this period, a Z-axis drive signal DrZ as shown in FIG. 9 (2) is given to the sensor main body, and the vibrator 20 vibrates in the Z-axis direction. Therefore, a Z-axis displacement detection signal SΔz as shown in FIG. 9 (3) is obtained. As described above, if the vibrator 20 vibrates at a resonance frequency in the Z-axis direction, the phase of the Z-axis displacement detection signal SΔz is delayed by 90 ° with respect to the phase of the Z-axis drive signal DrZ. Each waveform in FIG. 9 shows the state at this time.

  In general, it is known that in such a vibration system, when the vibrator is vibrated at a specific resonance frequency, the movement using the supplied energy most efficiently is possible and the largest amplitude is obtained. At this time, it is also known that the actual phase of the vibrator is delayed by 90 ° with respect to the phase of the drive signal. The waveform diagram shown in FIG. 9 shows each signal waveform obtained when the vibrator vibrates in an ideal vibration state.

  Here, the positive side synchronous detection signal SdA shown in FIG. 9 (4) is a detection signal having a pulse (pulse centered at the positive side peak position) synchronized with the positive side peak of the Z-axis drive signal DrZ. The negative side synchronous detection signal SdB shown in FIG. 9 (5) is a detection signal having a pulse synchronized with the negative peak of the Z-axis drive signal DrZ (pulse centered at the negative peak position). 8 is a function of integrating the input signal Sin, that is, the signal value of the Z-axis displacement detection signal SΔz only during the pulse period of the positive side synchronous detection signal SdA by the function of the gate switch Ga. The negative-side integrator K2 performs the function of integrating the input signal Sin, that is, the signal value of the Z-axis displacement detection signal SΔz only during the pulse period of the negative-side synchronous detection signal SdB by the function of the gate switch Gb.

  FIG. 9 (6) shows the integration process of the signal value of the Z-axis displacement detection signal SΔz. That is, the integration areas a and b shown by hatching in this graph correspond to areas where signal values are integrated by the positive side integrator K1, and the integration areas c and d are signal values by the negative side integrator K2. This corresponds to the region where the integration is performed. As in the example shown in FIG. 9, when the phase of the Z-axis displacement detection signal SΔz is exactly 90 ° behind the phase of the Z-axis drive signal DrZ, the area of the integration region a and the area of the integration region b Are equal, and the area of the integration region c is equal to the area of the integration region d. However, since the integration areas a and d are areas showing negative signal values and the integration areas b and c are areas showing positive signal values, the integration value by the positive side integrator K1 eventually becomes zero, and the negative side integrator K2 The integrated value due to becomes zero, and the output signal Sout output from the differentiator K3 becomes zero.

  Therefore, as shown in FIG. 9 (7), the Z-axis phase measurement signal Fzp (output signal Sout in FIG. 8) output from the synchronous detector 445 becomes a signal indicating zero. This indicates that the vibrator 20 currently vibrates in the Z-axis direction with an ideal phase (that is, a phase that is exactly 90 ° behind the phase of the Z-axis drive signal DrZ). In other words, the phase difference with respect to the ideal phase is zero. When such a Z-axis phase measurement signal Fzp is fed back as a feedback signal, the feedback controller 110 controls the Z-axis drive signal generator 150 to maintain the frequency fz of the generated Z-axis drive signal DrZ as it is. I do.

  Next, let us consider a case where the vibration phase of the vibrator 20 in the Z-axis direction deviates from an ideal phase due to some factor. FIG. 10 is a waveform diagram showing signal waveforms when the phase is slightly delayed. That is, the phase difference of the Z-axis displacement detection signal SΔz shown in FIG. 10 (3) with respect to the phase of the Z-axis drive signal DrZ shown in FIG. 10 (2) exceeds 90 °, and deviates from an ideal vibration state. Will be. In this case, as can be seen from FIG. 10 (6), the areas of the integration regions a, b, c, d shown by hatching the graph change. Specifically, the areas of the integration areas a and c are larger than the areas of the integration areas b and d. For this reason, if each integration region is integrated in consideration of the sign, the integration value (integration region a, b) by the positive side integrator K1 becomes negative, and the integration value by the negative side integrator K2 (integration region c, d). ) Becomes positive. Eventually, the output signal Sout output from the differentiator K3 becomes negative.

  Therefore, as shown in FIG. 10 (7), the Z-axis phase measurement signal Fzp (output signal Sout in FIG. 8) output from the synchronous detector 445 becomes a signal indicating a negative value (FIG. 10 (7)). The one-dot chain line is a reference level indicating a value of zero, and the solid line indicates the actual level of the signal Fzp). This indicates that the vibrator 20 is oscillating with a delay from the ideal phase. In other words, the difference between the one-dot chain line level and the solid line level in FIG. 10 (7) is the phase difference with respect to the ideal phase. When such a Z-axis phase measurement signal Fzp is fed back as a feedback signal, the feedback controller 110 lowers the frequency fz of the generated Z-axis drive signal DrZ with respect to the Z-axis drive signal generator 150, thereby delaying the phase. (In an experiment conducted by the inventor of the present application, it has been confirmed that if the frequency fz is lowered, control for advancing the phase becomes possible).

  Conversely, FIG. 11 is a waveform diagram showing signal waveforms when the phase is slightly advanced. That is, the phase difference of the Z-axis displacement detection signal SΔz shown in FIG. 11 (3) with respect to the phase of the Z-axis drive signal DrZ shown in FIG. 11 (2) divides 90 °, and deviates from an ideal vibration state. Will be. In this case, as can be seen from FIG. 11 (6), the areas of the integration regions a, b, c, d shown by hatching the graph are changed. Specifically, the areas of the integration areas a and c are smaller than the areas of the integration areas b and d. For this reason, if each integration region is integrated in consideration of the sign, the integration value (integration region a, b) by the positive side integrator K1 becomes positive, and the integration value (integration region c, d) by the negative side integrator K2 is positive. ) Becomes negative. Eventually, the output signal Sout output from the differentiator K3 becomes positive.

  Therefore, as shown in FIG. 11 (7), the Z-axis phase measurement signal Fzp (output signal Sout in FIG. 8) output from the synchronous detector 445 becomes a signal indicating a positive value (FIG. 11 (7)). The one-dot chain line is a reference level indicating a value of zero, and the solid line indicates the actual level of the signal Fzp). This indicates that the vibrator 20 is currently oscillating from an ideal phase. In other words, the difference between the one-dot chain line level and the solid line level in FIG. 11 (7) is the phase difference with respect to the ideal phase. When such a Z-axis phase measurement signal Fzp is fed back as a feedback signal, the feedback control unit 110 increases the frequency fz of the generated Z-axis drive signal DrZ to the Z-axis drive signal generation unit 150 to advance the phase. (In an experiment conducted by the inventor of the present application, it has been confirmed that when the frequency fz is increased, it is possible to control to delay the phase).

  The reason why the Z-axis phase measurement signal Fzp is obtained during the first stable oscillation period βz by the synchronous detector 445 shown in FIG. 3 has been described above. The X-axis phase measurement signal Fxp is obtained during the oscillation period βx. Thus, the obtained phase measurement signals Fzp and Fxp are fed back to the feedback control unit 110 as described above, and the feedback control unit 110 drives the Z-axis so that the signal values of these feedback signals become zero. Control is performed to adjust the frequencies of the Z-axis drive signal DrZ generated by the signal generator 150 and the Z-axis drive signal DrX generated by the X-axis drive signal generator 140.

  Subsequently, when the circuit shown in FIG. 8 is used as the synchronous detector 442 shown in FIG. 3 and the X-axis displacement detection signal SΔx is given as the input signal Sin, the output signal Sout obtained from this circuit is the transducer 20. The reason why the signal indicates the Coriolis force in the X-axis direction, that is, the angular velocity ωy around the Y-axis, which has been applied to is described briefly.

  FIG. 12 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 3 in the state where the angular velocity around the Y axis is not acting. As shown in FIG. 12 (1), the time axis in this figure shows a part of the stable oscillation period βz within the first half period Tz. During this period, a Z-axis drive signal DrZ as shown in FIG. 12 (2) is given to the sensor main body, and the vibrator 20 vibrates in the Z-axis direction. Therefore, a Z-axis displacement detection signal SΔz as shown in FIG. 12 (3) is obtained. As described above, if the vibrator 20 vibrates in an ideal manner, the phase of the Z-axis displacement detection signal SΔz is delayed by 90 ° with respect to the phase of the Z-axis drive signal DrZ. Each waveform in FIG. 12 shows the state at this time.

  Thus, when the vibrator 20 is vibrating in the Z-axis direction, if the angular velocity around the Y-axis is not acting, the Coriolis force in the X-axis direction does not act, so the vibrator 20 is in the X-axis direction. There is no displacement with respect to. Therefore, as shown in FIG. 12 (6), the X-axis displacement detection signal SΔx is a signal indicating a zero level. Since the X-axis displacement detection signal SΔx indicating such a zero level is given to the synchronous detector 442, the output signal, that is, the angular velocity detection signal ωy around the Y-axis is as shown in FIG. 12 (7). , A signal indicating a zero level.

  On the other hand, FIG. 13 is a signal waveform diagram for explaining the operation of the detection circuit shown in FIG. 3 in the state where the angular velocity around the Y axis is acting. When the vibrator 20 is vibrating in the Z-axis direction, if an angular velocity around the Y-axis is applied, a Coriolis force in the X-axis direction is applied, and the vibrator 20 is displaced in the X-axis direction. However, since the direction in which the Coriolis force acts depends on the movement direction of the vibrator 20, when the vibrator 20 is moving in the positive direction of the Z axis and in the negative direction of the Z axis. Sometimes, the direction of the Coriolis force in the X-axis direction is reversed even if the direction and magnitude of the angular velocity about the Y-axis are exactly the same.

  For example, the signal value of the Z-axis displacement detection signal SΔz in FIG. 13 (3) indicates the position of the vibrator 20 with respect to the Z-axis, but the point P1 on the graph indicates that the position of Z = 0 is the Z-axis positive. The point P2 indicates the moment when it reaches the maximum amplitude point in the positive direction of the Z axis, and the point P3 indicates the moment when it passes through the Z = 0 position in the negative direction of the Z axis. The point P4 indicates the moment when the maximum amplitude point in the negative Z-axis direction is reached. Therefore, in the first half process of moving to the points P0 to P2, the vibrator moves with a velocity component in the positive direction of the Z axis (takes the maximum positive velocity at the moment of passing through the point P1), and moves to the points P2 to P4. In the latter half process, the vibrator moves with a velocity component in the negative direction of the Z axis (takes the maximum negative velocity at the moment of passing through the point P3).

  Here, the Coriolis force in the X-axis direction acting on the vibrator is proportional to the velocity component of the vibrator in the Z-axis direction, and the displacement of the vibrator in the X-axis direction is also in accordance with this. Therefore, in this case, an X-axis displacement detection signal SΔx as shown in FIG. 13 (6) is obtained. Since the X-axis displacement detection signal SΔx is given to the synchronous detector 442, the output signal, that is, the angular velocity detection signal ωy around the Y-axis, has a predetermined level as shown in FIG. 13 (7). It becomes the signal which shows. That is, as shown in FIG. 13 (6), the integrated value (integrated region e) by the positive integrator K1 becomes positive, and the integrated value (integrated region f) by the negative integrator K2 becomes negative. The output signal Sout corresponding to the difference between the two output from the device K3 has a positive value. In FIG. 13 (7), the alternate long and short dash line indicates the zero level, and the solid line indicates the level of the output signal Sout, that is, the angular velocity detection signal ωy around the Y axis.

  As described above, the reason why the angular velocity detection signal ωy around the Y axis can be obtained by the synchronous detector 442 shown in FIG. 3 during the first stable oscillation period βz has been described. An angular velocity detection signal ωx around the X axis is obtained during the stable vibration period βz, and the angular velocity detection signal ωz around the Z axis is obtained by the synchronous detector 444 during the second stable vibration period βx.

  As described above, in the detection circuit shown in FIG. 3, the X-axis amplitude measurement signal Fxa, the X-axis phase measurement signal Fxp, and the Z-axis are indicated by the elements having the 400th symbol drawn below the sensor body 300. The amplitude measurement signal Fza, the Z-axis phase measurement signal Fzp, the angular velocity detection signal ωx around the X axis, the angular velocity detection signal ωy around the Y axis, and the angular velocity detection signal ωz around the Z axis are obtained. Moreover, each of these signals is obtained by detecting the displacement of the vibrator only during the period of the stable oscillation period βx indicated by the X-axis detection enable signal EnX or the stable oscillation period βz indicated by the Z-axis detection enable signal EnZ. Since it is a signal, it is an accurate value for a period in which the vibration of the vibrator is stable.

  After all, the gate switch 421 and the AM detector 431 in the detection circuit shown in FIG. 3 are detected during the second stable oscillation period βx, the detection signal of the X-axis positive detection element and the detection signal of the X-axis negative detection element. Based on the detected value SΔx indicating the displacement of the vibrator in the X-axis direction obtained as a difference between the X-axis amplitude and the X-axis amplitude measurement unit that measures the amplitude Fxa of the vibrator in the X-axis direction. The detector 432 detects the amplitude of the vibrator in the Z-axis direction based on the detection value SΔz indicating the displacement of the vibrator in the Z-axis direction obtained from the Z-axis displacement detection element during the first stable vibration period βz. A Z-axis amplitude measuring unit that measures Fza is configured.

  Further, the gate switch 421 and the synchronous detector 441 detect the X-axis positive detection element by using the positive synchronous detection signal SdA and the negative synchronous detection signal SdB during the second stable oscillation period βx. X axis for measuring the phase Fxp of the vibrator in the X axis direction based on the detection value SΔx indicating the displacement of the vibrator in the X axis direction obtained as the difference between the signal and the detection signal of the X axis negative side detection element The phase measurement unit is configured, and the gate switch 425 and the synchronous detector 445 detect the Z-axis displacement by using the positive side synchronous detection signal SdA and the negative side synchronous detection signal SdB during the first stable oscillation period βz. Based on the detected value SΔz indicating the displacement of the vibrator in the Z-axis direction obtained from the element for use, a Z-axis phase measurement unit that measures the phase Fzp of the vibrator in the Z-axis direction is configured.

  On the other hand, the gate switch 422 and the synchronous detector 442 detect the X-axis positive detection element by using the positive synchronous detection signal SdA and the negative synchronous detection signal SdB during the first stable oscillation period βz. Based on the detection value SΔx indicating the difference between the signal and the detection signal of the X-axis negative side detection element, a Y-axis angular velocity detector that outputs an electrical signal indicating the angular velocity ωy around the Y-axis is configured, and the gate switch 423 And the synchronous detector 443 uses the positive side synchronous detection signal SdA and the negative side synchronous detection signal SdB during the first stable oscillation period βz, so that the detection signal of the Y axis positive side detection element and the Y axis negative detection signal Based on the detected value SΔy indicating the difference from the detection signal of the side detection element, an X-axis angular velocity detector that outputs an electrical signal indicating the angular velocity ωx around the X-axis is configured, and the gate switch 424 and the synchronous detector 44 are configured. Uses the positive side synchronous detection signal SdA and the negative side synchronous detection signal SdB during the second stable oscillation period βx, so that the detection signal of the Y axis positive detection element and the negative detection element of the Y axis are detected. Based on the detection value SΔy indicating the difference from the detection signal, the Z-axis angular velocity detector that outputs an electrical signal indicating the angular velocity ωz around the Z-axis is configured.

  The feedback control unit 110 shown in FIG. 3 generates the Z generated by the Z-axis drive signal generation unit 150 based on the amplitude Fza measured by the Z-axis amplitude measurement unit and the phase Fzp measured by the Z-axis phase measurement unit. Feedback control is performed so that the frequency fz and the amplitude Az of the axis drive signal DrZ have a predetermined reference frequency and reference amplitude, and the amplitude Fxa measured by the X-axis amplitude measurement unit and the phase Fxp measured by the X-axis phase measurement unit Based on the above, the feedback control is performed so that the frequency fx and the amplitude Ax of the X-axis drive signal DrX generated by the X-axis drive signal generator 140 become the predetermined reference frequency and reference amplitude.

  As such feedback control method, for example, a PID control method using a control circuit combining circuit elements such as resistance, capacitance, and inductance, a control method using a microprocessor, and the like are well known. Description is omitted.

<<< §5. General sensor operation >>>
FIG. 14 is a signal waveform diagram for explaining the general operation of the angular velocity sensor according to the present invention. As described above, the detection circuit shown in FIG. 3 has a function of performing a repetitive operation for each period T constituted by both half periods Tz and Tx, as shown in FIG. 14 (1). As shown in (2) and (3), the vibrator is vibrated alternately in the Z-axis direction and the X-axis direction using the Z-axis drive signal DrZ and the X-axis drive signal DrX. On the other hand, the detection operation is performed during the period of the first stable vibration period βz and the second stable vibration period βx indicated by the Z-axis detection enable signal EnZ and the X-axis detection enable signal EnX shown in FIGS. 14 (4) and (5). Only done about.

  Therefore, as shown in FIG. 14 (6), the Z-axis amplitude measurement signal Fza, the Z-axis phase measurement signal Fzp, the X-axis amplitude measurement signal Fxa, the X-axis phase measurement signal Fxp, the angular velocity detection signal ωx around the X axis, and the Y axis The angular velocity detection signal ωy around and the angular velocity detection signal ωz around the Z axis are obtained only during the hatched period in the figure. Here, since the Z-axis amplitude measurement signal Fza and the Z-axis phase measurement signal Fzp are used for control when the vibrator is vibrated in the Z-axis direction, as illustrated, during the first stable vibration period βz. It is sufficient if it is obtained, and the X-axis amplitude measurement signal Fxa and the X-axis phase measurement signal Fxp are used for control when the vibrator is vibrated in the X-axis direction. It is sufficient if it is obtained during the stable oscillation period βx.

  On the other hand, the angular velocity detection signals ωx, ωy, and ωz are main output signals of the angular velocity sensor, and it is preferable that, in practice, some signal output is always obtained. Therefore, the synchronous detectors 442, 443, and 444 functioning as the angular velocity detection unit have a function of holding the immediately preceding detection value when the stable vibration period is not reached, and the period until the next stable vibration period comes. It is preferable to continuously output the held detection value.

  Specifically, as shown in FIG. 14 (6), the detected values of the angular velocity detection signals ωx and ωy are obtained only within the period of the first stable vibration period βz shown by hatching in the figure. At the end of the stable vibration period βz, the detected value at that time is held, and the detected value held until the next first stable vibration period βz comes to be output as it is. You can do it. Similarly, the detected value of the angular velocity detection signal ωz is obtained only within the period of the second stable vibration period βx shown by hatching in the figure, but at the end of the second stable vibration period βx, the detection at that time is detected. The value may be held, and the detected value held until the next second stable vibration period βx comes to be output as it is.

  In this case, accurate detection values that are updated in real time are output during the hatched period, while past detected values that are retained are continuously output during other periods. As a result, the accuracy of the detected value decreases. However, if the detection cycle T is set to a relatively short time, a detection value that is practically satisfactory can be obtained. For example, in the case of the above-described embodiment, since T = 12.5 ms is set, even if the held detection value is continuously output, there is no problem in using it for general purposes. Absent.

  As already described, in the angular velocity sensor according to the present invention, it is preferable that the frequency for vibrating the vibrator is set to a resonance frequency f0 unique to the vibration direction. FIG. 15 is a graph showing frequency characteristics of a general mechanical vibration system. Graph A is a graph showing the amplitude with respect to the vibration frequency f. Even when the same energy is supplied to excite the vibrator, the amplitude when the vibrator is vibrated at the resonance frequency f0 is the largest as shown in the figure. Therefore, when the feedback control unit 110 performs feedback control for each half cycle, when the resonance frequency of the vibrator with respect to the vibration direction of the half cycle is set to f0, the drive signal frequency is set to f0. If this is performed, a very efficient detection operation becomes possible.

  The resonance frequency f0 of the vibrator has a unique value for each vibration axis. In the case of the above-described embodiment, the resonance frequency in the case of vibrating in the Z-axis direction and the resonance frequency in the case of vibrating in the X-axis direction have different eigenvalues, and therefore, the first half cycle Tz and the second half cycle. In the period Tx, each vibrator vibrates at a separate frequency. Of course, the resonance frequency in the Z-axis direction and the resonance frequency in the X-axis direction can be matched by appropriately designing the structure of the sensor body.

  On the other hand, graph B is a graph showing the phase difference between the drive signal and the actual displacement, and the phase difference is indicated by the angle axis shown on the left side. As shown in the figure, when oscillating at the resonance frequency f0, the phase of the actual displacement is delayed by 90 ° with respect to the phase of the drive signal. This is why the feedback control unit 110 performs frequency control such that the phase difference is 90 ° as described in §4. In general, the resonance frequency of the vibrator differs for each product lot, and also changes depending on the usage environment such as temperature. However, it is universal that “when oscillated at a resonance frequency, the phase of the actual displacement is delayed by 90 ° with respect to the phase of the drive signal”. Therefore, the frequency at which the phase of the drive signal and the phase of the vibrator measured by the phase measurement unit cause a phase difference of 90 ° is regarded as the frequency f0, and the frequency control for the drive signal is performed. That's fine. In the present invention, “feedback control for maintaining the phase difference at 90 °” is performed, so that it is possible to perform correct control to always maintain an ideal vibration state for any product lot in any use environment. Become.

  Graph C shows the feedback signal indicating the phase difference, that is, the phase measurement signals Fxp and Fzp in the example shown in §4. When the actual vibration frequency of the vibrator deviates from the resonance frequency f0, the value of the feedback signal also deviates from the reference value. The feedback control unit 110 performs control such that the phase difference indicated by the feedback signal is 90 °. It should be noted that since the increase / decrease relationship of the phase difference with respect to the frequency is reversed if the frequency range outside the illustrated vicinity frequency region N is deviated, correct control cannot be performed. Therefore, the feedback control unit 110 does not deviate from the vicinity frequency region N. Need to do.

  Actually, it is known that when the vibrator is vibrated accurately at the resonance frequency f0, the system becomes nonlinear and efficient control cannot be performed. Therefore, in practice, it is preferable to perform control so that the vibration frequency of the vibrator is maintained at a predetermined frequency slightly shifted from the resonance frequency f0 instead of performing control so as to match the vibration frequency of the vibrator with the accurate resonance frequency f0. That is, when the feedback control unit 110 performs feedback control for each half cycle, and the resonance frequency of the vibrator in the vibration direction of the half cycle is f0, the frequency of the drive signal is a predetermined frequency near f0. However, it is only necessary to perform control such that the frequency f0 is another frequency.

  As described above, when the vibrator vibrates at a frequency that causes a phase difference of 90 ° between the phase of the drive signal and the phase of the vibrator measured by the phase measurement unit, the vibration frequency is the resonance frequency. f0. Therefore, in order to perform control to maintain a predetermined frequency slightly shifted from the resonance frequency f0, the phase difference becomes a predetermined value (for example, 85 ° or 95 °) in the vicinity of 90 ° (excluding 90 °). Such feedback control may be performed. In §4, the control operation for performing the feedback control so that the signal values of the phase measurement signals Fxp and Fzp are made zero is described. However, when the feedback control is performed so that the phase difference is 85 ° or 95 °, the phase measurement is performed. Feedback control may be performed so as to maintain the signal values of the signals Fxp and Fzp at a predetermined positive or negative value close to zero.

<<< §6. Optimal period setting >>>
As described above, the measurement cycle T in the present invention is configured by the first half cycle T1 for vibrating the vibrator in the first coordinate axis direction and the second half cycle T2 for vibrating in the second coordinate axis direction. Is done. Then, as shown in FIGS. 4 (6) and (7), each half cycle T1, T2 is divided into an unstable vibration period α in which the vibration state of the vibrator is expected to be unstable and the vibrator is stable. It is divided into the stable vibration period β that is expected to maintain the vibration state, and the angular velocity is detected within the period of the stable vibration period β.

  In the case of the embodiment described above, T = 12.5 ms is set, and the periodic operation is repeatedly executed at a frequency of 80 Hz. Then, settings are made so that each half cycle becomes equal, and T1 = T2 = 6.25 ms. In practice, such a period setting is preferably set to an optimum value according to the resonance frequency of the vibrator. The reason will be described below.

  The mechanical structure used for the angular velocity sensor according to the present invention is joined to a flexible support having an upper surface parallel to the XY plane and a center at the lower surface of the flexible support. Vibrator, a fixing member for fixing the periphery of the flexible support, a drive element group disposed above the flexible support, and a detection element disposed above the flexible support And an element group. Therefore, the present inventor actually created a plurality of prototypes of such mechanical structures (changed dimensions, shapes, materials, etc. of each part) or designed them on a computer simulation program, With respect to the prototype, the relationship between the resonance frequency in a specific coordinate axis direction and the unstable vibration period α when vibrating in the axis direction was examined by actual measurement or simulation.

  As a result, when the resonance frequency of the vibrator in a specific vibration direction is f0, the length α of the unstable vibration period is distributed in the range of (1 / f0) × 50 to (1 / f0) × 125. Turned out to be. Note that the time point at which the vibration state of the vibrator was determined to be stable was the time point at which the amplitude value reached 90% of the “steady amplitude value”. Here, the “steady amplitude value” refers to the amplitude value when the vibrator continues to vibrate in a specific vibration direction for a sufficiently long period (for example, several seconds), and the amplitude of the vibrator becomes constant. Instead of determining that “vibration was stable” when it reached “steady amplitude value”, it was determined that “vibration was stable” when it reached 90%. This is because it has been experimentally confirmed that the detection result obtained at the time point is practically the same as the detection result obtained when the “steady amplitude value” is reached.

  As described above, according to experiments (actual measurement and simulation) conducted by the inventor of the present application, the length α of the unstable vibration period of the vibrator varies depending on various mechanical structures, but vibration in the vibration direction. When the resonance frequency of the child is f0, the distribution is approximately in the range of α = (1 / f0) × 50 to (1 / f0) × 125. Of course, from the viewpoint of “stable measurement”, the length α of the unstable oscillation period may be set as long as possible. Actually, the angular velocity can be detected regardless of whether the periods αz and αx in FIGS. 4 (6) and (7) are set to several seconds or minutes.

  However, as the periods αz and αx are set longer, the half periods Tz and Tx are also longer, so the period in which the angular velocities ωx, ωy, and ωz around the three coordinate axes are obtained becomes longer, and the detected value is on the time axis. This is not preferable because the resolution is reduced. For example, when the half periods Tz and Tx are set to about several seconds, the sensor functions theoretically as an angular velocity sensor, but such a sensor should be used to detect camera shake during shooting with a digital camera. It is not practical and has no value as a commercial product. As described above, in order to increase the resolution on the time axis, it is preferable to set the half periods Tz and Tx as short as possible. For this purpose, it is preferable to set the length α of the unstable oscillation period as short as possible.

  Eventually, when the resonance frequency of the vibrator in a specific vibration direction is set to f0, it is expected that the vibrator will be in a stable vibration state from the start of supplying a drive signal for vibrating the vibrator in the vibration direction. If the period α up to the point in time is set within the range of (1 / f0) × 50 ≦ α ≦ (1 / f0) × 125, an appropriate detection operation can be performed for any sensor employing a mechanical structure. It becomes possible to do. Therefore, in designing the detection circuit of the angular velocity sensor according to the present invention, it is preferable to design so that the period of the unstable vibration period α is within the above range.

  On the other hand, the length β of the stable oscillation period is a parameter that determines the length of the period during which the angular velocity measurement operation is performed. The longer the period β is set, the greater the number of detected value samples obtained in the half cycle, but the longer the period in which the angular velocities ωx, ωy, and ωz around the three coordinate axes are obtained, the detected value The resolution on the time axis decreases. According to an experiment conducted by the present inventor, an appropriate detection value with the best balance could be obtained when the period α was set to the period β.

  As described above, if the period α is set to the period β, the half cycle = α + β = 2α may be set. After all, when the resonance frequency of the vibrator in the first coordinate axis direction is f1, and the resonance frequency of the vibrator in the second coordinate axis direction is f2, the length of the unstable vibration period is as described above (1 / F0) × 50 to (1 / f0) × 125, the first half period T1 is set to a range of (1 / f1) × 100 ≦ T1 ≦ (1 / f1) × 250. And the second half cycle T2 may be set in the range of (1 / f2) × 100 ≦ T2 ≦ (1 / f2) × 250. In the case of a sensor in which the resonance frequency f1 in the Z-axis direction of the vibrator is substantially equal to the resonance frequency f2 in the X-axis direction, the resonance frequency is f0 and the period T is (1 / f0) × 200 to (1 / f0) ×. When the range is set to 500, good detection is possible.

<<< §7. Other variations >>
Until now, as in the example shown in FIG. 1 and FIG. 2, the individual elements constituting the driving element group and the detection element group are formed into piezoelectric sensors fixed to the upper surface of the flexible support 10. Although an example to which the present invention is applied has been described, the present invention is not limited to an angular velocity sensor using such a piezoelectric element. For example, each element constituting the drive element group and the detection element group includes a displacement electrode fixed to the upper surface of the flexible support and a fixed electrode fixed to a position facing the displacement electrode. The present invention can also be applied to an angular velocity sensor including a configured capacitive element.

  FIG. 16 is a longitudinal sectional view showing a structure of a sensor main body using such a capacitive element. In the sensor main body shown in FIG. 16, the configurations of the flexible support 10, the vibrator 20, and the fixing member 30 are exactly the same as those of the sensor main body shown in FIG. However, instead of providing the piezoelectric element 40, a capacitive element is formed. That is, the auxiliary substrate 60 is bonded to the upper side of the flexible support 10 via the pedestal 50, and the common electrode Ec formed on the upper surface of the flexible support 10 and the lower surface of the auxiliary substrate 60 are formed. Individual capacitive elements are formed by the individual electrodes thus formed.

  FIG. 17 is a bottom view of the auxiliary substrate 60 of the sensor main body shown in FIG. The shape and arrangement of the twelve electrodes formed on the lower surface of the auxiliary substrate 60 are the same as the shape and arrangement of the twelve electrodes formed on the upper surface of the piezoelectric element 10 shown in FIG. It is shown with a reference numeral. A total of 12 capacitive element groups are formed by electrode pairs facing each other. These 12 sets of capacitive element groups perform substantially the same function as the 12 sets of piezoelectric element groups shown in FIG.

  Piezoelectric elements have the property of causing expansion and contraction when a voltage is applied between the upper and lower electrodes. However, the capacitive element is subjected to the action of Coulomb force by applying a voltage between both electrodes. It has the property that the distance is changed. Therefore, if an AC drive signal is given to each drive electrode, the vibrator can be vibrated in a predetermined coordinate axis direction. In addition, the piezoelectric element has the property of generating a voltage between the upper and lower electrodes when subjected to mechanical expansion and contraction stress, and this property is used to detect the displacement of the vibrator in the predetermined axial direction. We were able to. On the other hand, when the capacitive element receives a stress that causes the flexible support 10 to bend, the distance between the electrodes changes, and the capacitance value changes. Thus, the displacement of the vibrator in the predetermined axis direction can be detected.

  As a result, the detection operation shown in FIG. 3 can be applied to the capacitive sensor main body shown in FIGS. 16 and 17 to perform the same detection operation as that described above. In short, the present invention relates to a flexible support having an upper surface that passes through the Z axis at the center and is parallel to the XY plane, a vibrator bonded to the center of the lower surface of the flexible support, and a flexible support. A sensor main body comprising: a fixing member for fixing the periphery of the body; a drive element group disposed above the flexible support; and a detection element group disposed above the flexible support. It can be said that the technology is applicable. The flexible support is not necessarily a flat substrate, and may be a member having a plurality of bridge structures, for example.

  Here, the drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive arranged in the X-axis negative area when projected onto the XY plane. And an Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area. When an AC drive signal is supplied to the element and the X-axis negative drive element, the vibrator vibrates along the X-axis, and an AC drive signal is supplied to the Y-axis positive drive element and the Y-axis negative drive element. Then, the vibrators vibrate along the Y-axis, and when the AC drive signal is supplied to all four driving elements, the vibrators vibrate along the Z-axis. As long as each of them has a function of causing specific bending, a piezoelectric element, a capacitive element, or another element may be used.

  The detection element group includes an X-axis positive detection element arranged in the X-axis positive area and an X-axis negative detection element arranged in the X-axis negative area when projected onto the XY plane. The element, the Y-axis positive detection element arranged in the Y-axis positive area, the Y-axis negative detection element arranged in the Y-axis negative area, and the XZ plane and the YZ plane are symmetric. Z-axis displacement detecting elements arranged in such a manner that the X-axis positive side detecting element and the X-axis negative side detecting element are flexibly supported when the vibrator is displaced in the X-axis direction. Due to the bending that occurs in the body, the detection signals having the absolute values corresponding to the displacement and having the opposite polarities are output. The Y-axis positive side detection element and the Y-axis negative side detection element Detection of opposite polarities with absolute values corresponding to the displacement due to the bending that occurs in the flexible support when displaced in the axial direction The Z-axis displacement detecting element outputs an absolute value corresponding to the displacement and responds to the displacement direction due to the bending that occurs in the flexible support when the vibrator is displaced in the Z-axis direction. As long as it has a function of outputting a detection signal having a polarity, it may be a piezoelectric element, a capacitive element, or another element.

  A feature of the present invention is that while performing control based on a detection signal obtained from the detection element group, an AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and a predetermined timing is obtained. And using a specific detection circuit that outputs an electrical signal indicating an angular velocity around each coordinate axis using a detection signal obtained from the detection element group.

  The detection circuit shown in FIG. 3 measures the angular velocity ωx around the X axis and the angular velocity ωy around the Y axis while vibrating the vibrator in the Z-axis direction during the first half cycle Tz, and the second half cycle Tx. Although the circuit measures the angular velocity ωz around the Z axis while vibrating the vibrator in the X axis direction, the detection circuit used in the present invention does not necessarily need to be a circuit of such an embodiment. It is possible to measure the angular velocity ωy around the Y axis as well as the angular velocity ωz around the Z axis while oscillating the vibrator in the X axis direction, and the angular velocity around the X axis while vibrating the vibrator in the Y axis direction. It is also possible to measure the angular velocity ωz about the Z axis together with ωx.

  As a result, the detection circuit used in the present invention has a function of executing a periodic operation for the period T constituted by the first half period T1 and the second half period T2, and the first drive signal Generator, second drive signal generator, positive side synchronous detection signal generator, negative side synchronous detection signal generator, first detection enable signal generator, second detection enable signal generator, matrix converter, 1 angular velocity detection unit, second angular velocity detection unit, third angular velocity detection unit, first amplitude measurement unit, first phase measurement unit, second amplitude measurement unit, second phase measurement unit, feedback control What is necessary is just to have a part.

  Here, in the first driving signal generator, an AC signal having a predetermined frequency and amplitude is arranged in the first half period T1, and no AC signal is present in the second half period T2. The second drive signal generation unit is a component that generates a first drive signal that is not arranged, and the second drive signal generation unit does not provide any AC signal in the first half cycle T1, and the second half In the period T2, an AC signal having a predetermined frequency and amplitude is provided and a component that generates a second drive signal.

  Further, the positive side synchronous detection signal generator generates a pulse width equal to or less than ½ of the period of the first drive signal at a position synchronized with the positive peak of the first drive signal in the first half period T1. Are periodically arranged, and in the second half cycle T2, the pulse width is ½ or less of the cycle of the second drive signal at a position synchronized with the positive peak of the second drive signal. The negative-side synchronous detection signal generator is a component that generates a positive-side synchronous detection signal in which pulses having a frequency are periodically arranged. A pulse having a pulse width equal to or less than ½ of the cycle of the first drive signal is periodically arranged at a position synchronized with the negative peak, and in the second half cycle T2, the second drive signal A pulse having a pulse width of 1/2 or less of the period of the second drive signal is periodically arranged at a position synchronized with the negative peak. That is a component that generates a negative-side synchronization detection signal.

  On the other hand, the first detection enable signal generator generates a first detection enable signal indicating a first stable oscillation period in which the vibrator is expected to maintain a stable vibration state in the first half period T1. The second detection enable signal generator is an element, and generates a second detection enable signal indicating a second stable oscillation period in which the vibrator is expected to maintain a stable vibration state in the second half period T2. It is a component to do.

  The matrix converter supplies the first drive signal or its phase inversion signal to the drive element necessary for vibrating the vibrator in the first coordinate axis direction in the first half cycle T1, The second half cycle T2 is a component that supplies the second drive signal or its phase inversion signal to the drive element necessary for vibrating the vibrator in the second coordinate axis direction.

  Then, the first angular velocity detection unit is caused by the Coriolis force of the vibrator obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable vibration period. A component that outputs an electrical signal indicating an angular velocity around the third coordinate axis based on a detection value indicating a displacement in the second coordinate axis direction. The second angular velocity detection unit is configured to output the first stable vibration period. Based on the detection value indicating the displacement in the third coordinate axis direction due to the Coriolis force of the transducer obtained from the detection element group by using the period, the positive side synchronous detection signal and the negative side synchronous detection signal, The third angular velocity detector uses a positive side synchronous detection signal and a negative side synchronous detection signal during the second stable vibration period. Depending on the detection element group Based on the detected values indicating displacement in the third coordinate axis direction due to the Coriolis force of the resulting transducer, is a component for outputting an electrical signal indicating the angular velocity around the first coordinate axis.

  Furthermore, the first amplitude measurement unit calculates the amplitude of the vibrator based on the detection value indicating the displacement of the vibrator in the first coordinate axis direction obtained from the detection element group during the first stable vibration period. The first phase measurement unit is a component to be measured, and the first phase measurement unit uses the positive side synchronous detection signal and the negative side synchronous detection signal during the period of the first stable oscillation period. It is a component that measures the phase of the vibrator based on a detection value indicating displacement in the first coordinate axis direction.

  On the other hand, the second amplitude measuring unit calculates the amplitude of the vibrator based on the detection value indicating the displacement of the vibrator in the second coordinate axis direction obtained from the detection element group during the second stable vibration period. The second phase measurement unit is a component to be measured, and the second phase measurement unit uses a positive-side synchronous detection signal and a negative-side synchronous detection signal during the second stable oscillation period. A component that measures the phase of the vibrator based on a detection value indicating displacement in the second coordinate axis direction.

  The feedback control unit is configured to output the first drive signal generated by the first drive signal generation unit based on the amplitude measured by the first amplitude measurement unit and the phase measured by the first phase measurement unit. The feedback control is performed so that the frequency and the amplitude become the predetermined reference frequency and the reference amplitude, and the second measurement is performed based on the amplitude measured by the second amplitude measurement unit and the phase measured by the second phase measurement unit. This is a component that performs feedback control so that the frequency and amplitude of the second drive signal generated by the drive signal generation unit become a predetermined reference frequency and reference amplitude.

10: flexible support 20: vibrator 30: fixing member 40: piezoelectric element 50: pedestal 60: auxiliary substrate 100: operation signal generator 110: feedback control unit 120: X-axis detection enable signal generation unit 130: Z-axis Detection enable signal generator 140: X-axis drive signal generator 150: Z-axis drive signal generator 160: Positive side synchronous detection signal generator 170: Negative side synchronous detection signal generator 200: Matrix converters 210 to 240: OP amplifier 300: Sensor body 411: Differencer 412: Differencer 413: Adders 421-425: Gate switch (SW)
431, 432: AM detector (AMD)
441-445: Synchronous detector (SD)
Ax: Amplitude of the X-axis drive signal Az: Amplitude of the Z-axis drive signal AMD: AM detectors a to f: Graph integration regions C1 to C7: Capacitor DIF: Differential amplifier DrX: X-axis drive signal DrZ: Z-axis drive Signal Dx (+): X-axis positive drive signal Dx (-): X-axis negative drive signal Dy (+): Y-axis positive drive signal Dy (-): Y-axis negative drive signal Ec: Common electrode EnX : X-axis detection enable signal EnZ: Z-axis detection enable signal Ex (+): X-axis positive drive electrode Ex (-): X-axis negative drive electrode Ey (+): Y-axis positive drive electrode Ey (-): Y-axis negative drive electrode Ex1: X-axis positive detection electrode Ex2: X-axis negative detection electrode Ey1: Y-axis positive detection electrode Ey2: Y-axis negative detection electrodes Ez1-Ez4 : Z-axis displacement detection electrode Fxa: X-axis amplitude measurement signal Fxp: X-axis phase measurement signal Fz : Z-axis amplitude measurement signal Fzp: Z-axis phase measurement signal f: Frequency f0: Resonance frequency fx: Frequency of X-axis drive signal fz: Frequency of Z-axis drive signal G: Annular groove Ga, Gb: Gate switch K1: Positive side Accumulator K2: Negative-side integrator K3: Differencer N: Near frequency region O: Origin XY, three-dimensional coordinate system OP1, OP2: Operational amplifiers P0 to P4: Points R1 to R17 on the graph: Resistance Ref: Reference voltage SD : Synchronous detector SdA: Positive synchronous detection signal SdB: Negative synchronous detection signal Sin: Input signal Sout: Output signal SW: Gate switch SΔx: X-axis displacement detection signal SΔy: Y-axis displacement detection signal SΔz: Z-axis displacement detection Signal T: Operation period Tx: Second half period Tz: First half period X, Y, Z: Each coordinate axis αx of the three-dimensional coordinate system: Second unstable vibration period αz: First unstable vibration period βx: second stable oscillation period β : First stable oscillation period ωx, ωy, ωz: angular velocity components about respective coordinate axes

Claims (15)

An angular velocity sensor for detecting an angular velocity around each coordinate axis in an XYZ three-dimensional coordinate system,
A flexible support having an upper surface passing through the Z-axis at a central position and parallel to the XY plane;
A vibrator bonded to the center of the lower surface of the flexible support;
A fixing member for fixing the periphery of the flexible support;
A drive element group disposed above the flexible support;
A group of detection elements disposed above the flexible support;
While performing control based on a detection signal obtained from the detection element group, an AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and the detection is performed at a predetermined timing. A detection circuit that outputs an electrical signal indicating an angular velocity around each coordinate axis using a detection signal obtained from the device group;
With
The drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive element arranged in the X-axis negative area when projected onto the XY plane. And a Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area, and the X-axis positive drive element When the AC drive signal is supplied to the X-axis negative drive element, the vibrator vibrates along the X-axis, and the Y-axis positive drive element and the Y-axis negative drive element are AC driven. When the signal is supplied, the vibrator vibrates along the Y axis, and when the AC drive signal is supplied to all of the four sets of driving elements, the flexible vibrator so that the vibrator vibrates along the Z axis. Having a function of causing a specific deflection at each position of the support,
The detection element group includes an X-axis positive detection element arranged in an X-axis positive area and an X-axis negative detection element arranged in an X-axis negative area when projected onto the XY plane. And the Y-axis positive detection element arranged in the Y-axis positive region, the Y-axis negative detection element arranged in the Y-axis negative region, and both the XZ plane and the YZ plane are symmetric. Z-axis displacement detection element disposed on the X-axis, and the X-axis positive side detection element and the X-axis negative side detection element are arranged to be movable when the vibrator is displaced in the X-axis direction. Due to the bending generated in the flexible support, detection signals having absolute values corresponding to the displacement and having opposite polarities are output, and the Y-axis positive side detection element and the Y-axis negative side detection element are In response to the displacement due to the flexure generated in the flexible support when the vibrator is displaced in the Y-axis direction Detection signals having opposite values and having opposite polarities are output, and the Z-axis displacement detection element is caused by bending caused in the flexible support when the vibrator is displaced in the Z-axis direction. It has a function to output a detection signal having an absolute value corresponding to the displacement and a polarity corresponding to the displacement direction,
The detection circuit includes:
Having a function of executing a periodic operation for a period T constituted by the first half period T1 and the second half period T2,
A first drive signal in which an AC signal having a predetermined frequency and amplitude is arranged in the first half cycle T1, and no AC signal is arranged in the second half cycle T2. A first drive signal generator for generating
No AC signal is disposed in the first half cycle T1, and an AC signal having a predetermined frequency and amplitude is disposed in the second half cycle T2. A second drive signal generator for generating a signal;
In the first half cycle T1, a pulse having a pulse width equal to or less than ½ of the cycle of the first drive signal is periodically located at a position synchronized with the positive peak of the first drive signal. In the second half cycle T2, there is a pulse having a pulse width equal to or less than ½ of the cycle of the second drive signal at a position synchronized with the positive peak of the second drive signal. Periodically arranged, positive side synchronous detection signal generating unit for generating positive side synchronous detection signal,
In the first half cycle T1, a pulse having a pulse width equal to or less than ½ of the cycle of the first drive signal is periodically provided at a position synchronized with the negative peak of the first drive signal. In the second half cycle T2, there is a pulse having a pulse width equal to or less than ½ of the cycle of the second drive signal at a position synchronized with the negative peak of the second drive signal. The negative side synchronous detection signal generator that generates the negative side synchronous detection signal, which is periodically arranged,
A first detection enable signal generating unit for generating a first detection enable signal indicating a first stable vibration period in which the vibrator is expected to maintain a stable vibration state in the first half period T1;
A second detection enable signal generator for generating a second detection enable signal indicating a second stable vibration period in which the vibrator is expected to maintain a stable vibration state in the second half period T2,
In the first half cycle T1, the first driving signal or its phase inversion signal is supplied to the driving element necessary to vibrate the vibrator in the first coordinate axis direction, and the second half cycle T1. In the period T2, a matrix converter that supplies the second drive signal or a phase inversion signal thereof to a drive element necessary for vibrating the vibrator in the second coordinate axis direction;
The second coordinate axis resulting from the Coriolis force of the vibrator obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable oscillation period A first angular velocity detector that outputs an electrical signal indicating an angular velocity around the third coordinate axis based on a detected value indicating displacement in a direction;
The third coordinate axis resulting from the Coriolis force of the transducer obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable oscillation period A second angular velocity detector that outputs an electrical signal indicating an angular velocity around the second coordinate axis based on a detected value indicating displacement in a direction;
The third coordinate axis resulting from the Coriolis force of the transducer obtained from the detection element group by using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable oscillation period A third angular velocity detector that outputs an electrical signal indicating an angular velocity around the first coordinate axis based on a detected value indicating displacement in a direction;
Measuring the amplitude of the vibrator based on a detection value indicating displacement of the vibrator in the first coordinate axis direction obtained from the detection element group during the first stable vibration period; An amplitude measurement unit;
During the period of the first stable oscillation period, displacement of the vibrator obtained from the detection element group in the first coordinate axis direction by using the positive side synchronous detection signal and the negative side synchronous detection signal is performed. A first phase measurement unit for measuring the phase of the vibrator based on the detected value;
Measuring the amplitude of the vibrator based on a detection value indicating displacement of the vibrator in the second coordinate axis direction obtained from the detection element group during the second stable vibration period; An amplitude measurement unit;
During the period of the second stable oscillation period, displacement of the transducer obtained from the detection element group in the second coordinate axis direction by using the positive side synchronous detection signal and the negative side synchronous detection signal is performed. A second phase measuring unit for measuring the phase of the vibrator based on the detected value;
The frequency and amplitude of the first drive signal generated by the first drive signal generation unit based on the amplitude measured by the first amplitude measurement unit and the phase measured by the first phase measurement unit Is controlled so as to have a predetermined reference frequency and reference amplitude, and based on the amplitude measured by the second amplitude measuring unit and the phase measured by the second phase measuring unit, the second A feedback control unit that performs feedback control so that the frequency and amplitude of the second drive signal generated by the drive signal generation unit have a predetermined reference frequency and reference amplitude;
An angular velocity sensor comprising: An angular velocity sensor for detecting an angular velocity around each coordinate axis in an XYZ three-dimensional coordinate system,
A flexible support having an upper surface passing through the Z-axis at a central position and parallel to the XY plane;
A vibrator bonded to the center of the lower surface of the flexible support;
A fixing member for fixing the periphery of the flexible support;
A drive element group disposed above the flexible support;
A group of detection elements disposed above the flexible support;
While performing control based on a detection signal obtained from the detection element group, an AC drive signal is supplied to the drive element group to vibrate the vibrator in a predetermined coordinate axis direction, and the detection is performed at a predetermined timing. A detection circuit that outputs an electrical signal indicating an angular velocity around each coordinate axis using a detection signal obtained from the device group;
With
The drive element group includes an X-axis positive drive element arranged in the X-axis positive area and an X-axis negative drive element arranged in the X-axis negative area when projected onto the XY plane. And a Y-axis positive drive element arranged in the Y-axis positive area, and a Y-axis negative drive element arranged in the Y-axis negative area, and the X-axis positive drive element When the AC drive signal is supplied to the X-axis negative drive element, the vibrator vibrates along the X-axis, and when the AC drive signal is supplied to all of the four sets of drive elements, the vibrator Z Each has a function of causing a specific bending at each arrangement position of the flexible support so as to vibrate along an axis;
The detection element group includes an X-axis positive detection element arranged in an X-axis positive area and an X-axis negative detection element arranged in an X-axis negative area when projected onto the XY plane. And the Y-axis positive detection element arranged in the Y-axis positive region, the Y-axis negative detection element arranged in the Y-axis negative region, and both the XZ plane and the YZ plane are symmetric. Z-axis displacement detection element disposed on the X-axis, and the X-axis positive side detection element and the X-axis negative side detection element are arranged to be movable when the vibrator is displaced in the X-axis direction. Due to the bending generated in the flexible support, detection signals having absolute values corresponding to the displacement and having opposite polarities are output, and the Y-axis positive side detection element and the Y-axis negative side detection element are In response to the displacement due to the flexure generated in the flexible support when the vibrator is displaced in the Y-axis direction Detection signals having opposite values and having opposite polarities are output, and the Z-axis displacement detection element is caused by bending caused in the flexible support when the vibrator is displaced in the Z-axis direction. It has a function to output a detection signal having an absolute value corresponding to the displacement and a polarity corresponding to the displacement direction,
The detection circuit includes:
Having a function of executing a periodic operation for a period T constituted by the first half period Tz and the second half period Tx;
A Z-axis drive in which an AC signal having a predetermined frequency fz and amplitude Az is arranged in the first half cycle Tz, and no AC signal is arranged in the second half cycle Tx. A Z-axis drive signal generator for generating a signal DrZ;
In the first half cycle Tz, no AC signal is arranged, and in the second half cycle Tx, an AC signal having a predetermined frequency fx and amplitude Ax is arranged. An X-axis drive signal generator for generating a drive signal DrX;
In the first half cycle Tz, a pulse having a pulse width equal to or less than ½ of the cycle of the Z-axis drive signal DrZ is periodically provided at a position synchronized with the positive peak of the Z-axis drive signal DrZ. In the second half cycle Tx, a pulse having a pulse width equal to or less than ½ of the cycle of the X-axis drive signal DrX is located at a position synchronized with the positive peak of the X-axis drive signal DrX. A positive-side synchronous detection signal generator that generates a positive-side synchronous detection signal SdA that is periodically arranged;
In the first half cycle Tz, a pulse having a pulse width equal to or less than ½ of the cycle of the Z-axis drive signal DrZ is periodically provided at a position synchronized with the negative peak of the Z-axis drive signal DrZ. In the second half cycle Tx, a pulse having a pulse width equal to or less than ½ of the cycle of the X-axis drive signal DrX is located at a position synchronized with the negative peak of the X-axis drive signal DrX. A negative-side synchronous detection signal generator for generating a negative-side synchronous detection signal SdB, which is periodically arranged;
A Z-axis detection enable signal for generating a Z-axis detection enable signal EnZ indicating a first stable vibration period βz that is expected to maintain a stable vibration state along the Z-axis in the first half period Tz. Generating part;
X-axis detection enable signal for generating an X-axis detection enable signal EnX indicating a second stable oscillation period βx that is expected to maintain a stable vibration state along the X-axis in the second half period Tx. Generating part;
In the first half cycle Tz, the Z-axis drive signal DrZ is supplied to all of the four sets of drive elements, and in the second half cycle Tx, the X-axis positive drive element is supplied with the Z-axis drive signal DrZ. A matrix converter that supplies an X-axis drive signal DrX and supplies a phase inversion signal of the X-axis drive signal DrX to the X-axis negative drive element;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable oscillation period βz, the detection signal of the X axis positive side detection element and the X axis negative side detection element A Y-axis angular velocity detection unit that outputs an electrical signal indicating the angular velocity ωy around the Y axis based on a detection value indicating a difference from the detection signal;
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable oscillation period βz, the detection signal of the Y axis positive detection element and the Y axis negative detection element An X-axis angular velocity detector that outputs an electrical signal indicating an angular velocity ωx around the X axis based on a detection value indicating a difference from the detection signal of
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable oscillation period βx, the detection signal of the Y axis positive side detection element and the Y axis negative side detection element A Z-axis angular velocity detector that outputs an electrical signal indicating an angular velocity ωz around the Z-axis based on a detection value indicating a difference from the detection signal of
During the first stable oscillation period βz, the amplitude of the vibrator in the Z-axis direction is measured based on a detection value obtained from the Z-axis displacement detection element and indicating the displacement of the vibrator in the Z-axis direction. Z-axis amplitude measurement unit
Displacement of the vibrator in the Z-axis direction obtained from the Z-axis displacement detection element by using the positive side synchronous detection signal and the negative side synchronous detection signal during the first stable vibration period βz. A Z-axis phase measuring unit that measures a phase of the vibrator in the Z-axis direction based on a detection value indicating:
Displacement in the X-axis direction of the vibrator obtained as a difference between the detection signal of the X-axis positive detection element and the detection signal of the X-axis negative detection element during the second stable vibration period βx An X-axis amplitude measurement unit that measures the amplitude of the vibrator in the X-axis direction based on a detection value indicating
By using the positive side synchronous detection signal and the negative side synchronous detection signal during the second stable oscillation period βx, the detection signal of the X axis positive side detection element and the X axis negative side detection element are used. An X-axis phase measuring unit that measures the phase of the vibrator in the X-axis direction based on a detection value indicating the displacement of the vibrator in the X-axis direction obtained as a difference from the detection signal of
Based on the amplitude measured by the Z-axis amplitude measurement unit and the phase measured by the Z-axis phase measurement unit, the frequency and amplitude of the Z-axis drive signal DrZ generated by the Z-axis drive signal generation unit are predetermined. The feedback control is performed so that the reference frequency and the reference amplitude are obtained, and the X-axis drive signal generation unit is generated based on the amplitude measured by the X-axis amplitude measurement unit and the phase measured by the X-axis phase measurement unit. A feedback control unit that performs feedback control so that the frequency and amplitude of the X-axis drive signal DrX have a predetermined reference frequency and reference amplitude;
An angular velocity sensor comprising: The angular velocity sensor according to claim 2 ,
Matrix converter
A circuit that generates a sum signal “DrZ + DrX” and supplies the sum signal to the X-axis positive drive element;
A circuit that generates a difference signal “DrZ−DrX” and supplies the difference signal to the X-axis negative drive element;
A circuit for supplying “DrZ” to the Y-axis positive drive element;
A circuit for supplying “DrZ” to the Y-axis negative drive element;
An angular velocity sensor comprising: The angular velocity sensor according to any one of claims 1 to 3 ,
Angular velocity detector
A positive-side integrator that integrates the signal value of the given signal only while the pulse of the positive-side synchronous detection signal is given;
A negative-side integrator that integrates the signal value of the given signal only while the pulse of the negative-side synchronous detection signal is given; and
A subtractor that outputs a difference between the integrated value of the positive integrator and the integrated value of the negative integrator;
An angular velocity sensor comprising: a synchronous detection circuit SD comprising: an electrical signal corresponding to a difference obtained by the differentiator as a signal indicating an angular velocity. The angular velocity sensor according to claim 4 ,
An angular velocity sensor, further comprising a gate switch SW that allows the angular velocity detection section to pass a detection value only during a period of a stable vibration period and applies the detection value to the synchronous detection circuit SD. In the angular velocity sensor according to any one of claims 1 to 5 ,
Phase measurement unit
A positive-side integrator that integrates the signal value of the given signal only while the pulse of the positive-side synchronous detection signal is given;
A negative-side integrator that integrates the signal value of the given signal only while the pulse of the negative-side synchronous detection signal is given; and
A subtractor that outputs a difference between the integrated value of the positive integrator and the integrated value of the negative integrator;
An angular velocity sensor comprising: a synchronous detection circuit SD comprising: an electrical signal corresponding to a difference obtained by the differentiator as a signal indicating a phase measurement value. The angular velocity sensor according to claim 6 .
An angular velocity sensor characterized in that the phase measurement unit further includes a gate switch SW that allows a detected value to pass only during a stable vibration period and applies the detected value to the synchronous detection circuit SD. In the angular velocity sensor according to any one of claims 1 to 7 ,
The angular velocity detector has a function to hold the previous detected value when it is no longer in the stable vibration period, and continuously output the held detection value until the next stable vibration period comes An angular velocity sensor. In the angular velocity sensor according to any one of claims 1 to 8 ,
When the feedback control unit performs feedback control for each half cycle, control is performed such that the frequency of the drive signal is f0 when the resonance frequency of the vibrator in the vibration direction of the half cycle is f0. An angular velocity sensor. In the angular velocity sensor according to any one of claims 1 to 8 ,
When the feedback control unit performs feedback control for each half cycle, and the resonance frequency of the vibrator with respect to the vibration direction of the half cycle is f0, the frequency of the drive signal is a predetermined frequency near the f0 (the above-described frequency An angular velocity sensor that performs control such that f0 is excluded). The angular velocity sensor according to claim 9 or 10 ,
The frequency control for the drive signal is performed by regarding the frequency at which the phase of the drive signal and the phase of the vibrator measured by the phase measurement unit cause a phase difference of 90 ° as the frequency f0. Angular velocity sensor. In the angular velocity sensor according to any one of claims 1 to 11 ,
An angular velocity sensor, wherein each element constituting the drive element group and the detection element group is composed of a piezoelectric element fixed to the upper surface of the flexible support. In the angular velocity sensor according to any one of claims 1 to 11 ,
The individual elements constituting the drive element group and the detection element group are constituted by a displacement electrode fixed on the upper surface of the flexible support and a fixed electrode fixed at a position facing the displacement electrode. An angular velocity sensor comprising a capacitive element. The angular velocity sensor according to any one of claims 1 to 13 ,
When the resonance frequency of the vibrator with respect to a specific vibration direction is f0, the time when the vibrator is expected to be in a stable vibration state from the start of supplying a drive signal for vibrating the vibrator in the vibration direction The angular velocity sensor characterized in that the period α is set in the range of (1 / f0) × 50 ≦ α ≦ (1 / f0) × 125. The angular velocity sensor according to claim 14 ,
When the resonance frequency of the vibrator in the first coordinate axis direction is f1, and the resonance frequency of the vibrator in the second coordinate axis direction is f2, the first half cycle T1 is (1 / f1) × 100. ≦ T1 ≦ (1 / f1) × 250, and the second half cycle T2 is set to a range of (1 / f2) × 100 ≦ T2 ≦ (1 / f2) × 250 Angular velocity sensor.

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