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Angular velocity detection circuit

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20140174148 patent thumbnailZoom

Angular velocity detection circuit


An angular velocity detection apparatus includes a vibrator that generates a signal that includes an angular velocity component and a vibration leakage component, a driver section that generates the drive signal, and supplies the drive signal to the vibrator, an angular velocity signal generation section that extracts the angular velocity component from the signal generated by the vibrator, and generates an angular velocity signal corresponding to the magnitude of the angular velocity component, a vibration leakage signal generation section that extracts the vibration leakage component from the signal generated by the vibrator, and generates a vibration leakage signal corresponding to the magnitude of the vibration leakage component, and an adder-subtractor section that adds the vibration leakage signal to the angular velocity signal, or subtracts the vibration leakage signal from the angular velocity signal, in a given ratio to correct temperature characteristics of the angular velocity signal.
Related Terms: Velocity

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USPTO Applicaton #: #20140174148 - Class: 73 137 (USPTO) -
Measuring And Testing > Instrument Proving Or Calibrating >Speed, Velocity, Or Acceleration



Inventors: Hideto Naruse, Kenji Sato, Yutaka Takada

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The Patent Description & Claims data below is from USPTO Patent Application 20140174148, Angular velocity detection circuit.

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This application is a continuation application of U.S. application Ser. No. 13/216,553 filed Aug. 24, 2011 which claims priority to Japanese Patent Application No. 2010-199791 filed on Sep. 7, 2010 all of which are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates to an angular velocity detection apparatus and an electronic instrument.

An electronic instrument or a system that includes an angular velocity detection apparatus, and performs a predetermined control process based on the angular velocity detected by the angular velocity detection apparatus has been widely used. For example, a vehicle travel control system prevents a side skid, or detects an overturn, based on the angular velocity detected by the angular velocity detection apparatus.

Such an electronic instrument or system performs wrong control if the angular velocity detection apparatus breaks down. Therefore, measures such as lighting an alarm lamp when the angular velocity detection apparatus has broken down have been employed. Various technologies that diagnose failure of the angular velocity detection apparatus have been proposed. For example, JP-A-2000-171257 focuses on the fact that a signal output from the vibrator of the angular velocity detection apparatus includes an angular velocity component, and a self-vibration component (vibration leakage component) based on excited vibrations of the vibrator, and discloses method that determines the presence or absence of failure of the angular velocity detection apparatus by extracting the vibration leakage component from the signal output from the vibrator, and monitoring the amplitude of the vibration leakage component. JP-A-2010-107416 discloses a failure diagnosis method that reliably generates a self-vibration component by tuning the balance so that the vibration energy of the vibrator becomes imbalanced.

It is ideal that a circuit that extracts the angular velocity component not to extract the vibration leakage component. However, a phase shift of a synchronous detection clock signal occurs due to a circuit production variation, so that the vibration leakage component is included in the extracted angular velocity signal (gyro signal). Therefore, if the vibration leakage component is enhanced as disclosed in JP-A-2010-107416, the temperature characteristics of the angular velocity signal deteriorate due to the effect of the temperature characteristics of the vibration leakage component. If the temperature characteristics of the vibration leakage component are indicated by a linear function or a quadratic function, the temperature characteristics of the vibration leakage component can be corrected using a small-scale temperature compensation circuit. However, the vibration leakage component has temperature characteristics indicated by a higher-order function. The circuit scale necessarily increases when correcting the temperature characteristics of the vibration leakage component using a higher-order function circuit.

SUMMARY

According to a first aspect of the invention, there is provided an angular velocity detection apparatus including:

a vibrator that generates a signal that includes an angular velocity component corresponding to the magnitude of an angular velocity, and a vibration leakage component of vibrations based on a drive signal;

a driver section that generates the drive signal, and supplies the drive signal to the vibrator;

an angular velocity signal generation section that extracts the angular velocity component from the signal generated by the vibrator, and generates an angular velocity signal corresponding to the magnitude of the angular velocity component;

a vibration leakage signal generation section that extracts the vibration leakage component from the signal generated by the vibrator, and generates a vibration leakage signal corresponding to the magnitude of the vibration leakage component; and

an adder-subtractor section that adds the vibration leakage signal to the angular velocity signal, or subtracts the vibration leakage signal from the angular velocity signal, in a given ratio to correct temperature characteristics of the angular velocity signal.

According to a second aspect of the invention, there is provided an electronic instrument including the above angular velocity detection apparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram illustrating a configuration example of an angular velocity detection apparatus according to a first embodiment of the invention.

FIG. 2 is a diagram illustrating a vibrating element of a gyro sensor element.

FIG. 3 is a diagram illustrating the operation of a gyro sensor element.

FIG. 4 is a diagram illustrating the operation of a gyro sensor element.

FIG. 5 is a waveform diagram illustrating the angular velocity detection principle.

FIG. 6 is a waveform diagram illustrating the vibration leak detection principle.

FIGS. 7A to 7C are graphs illustrating an example of the temperature characteristics of an angular velocity signal and the temperature characteristics of a vibration leakage signal.

FIGS. 8A to 8C are graphs illustrating an example of the temperature characteristics of an angular velocity signal and the temperature characteristics of a vibration leakage signal.

FIG. 9 is a diagram illustrating a configuration example of an adder-subtractor circuit.

FIGS. 10A to 10D are graphs illustrating an example of correction of the temperature characteristics of an angular velocity signal according to the first embodiment.

FIGS. 11A to 11D are graphs illustrating an example of correction of the temperature characteristics of an angular velocity signal according to the first embodiment.

FIG. 12 is a graph illustrating an example of the temperature characteristics of an angular velocity signal and the temperature characteristics of a vibration leakage signal.

FIG. 13 is a diagram illustrating a configuration example of an angular velocity detection apparatus according to a second embodiment of the invention.

FIG. 14 is a diagram illustrating a configuration example of a first-order temperature adjustment circuit.

FIGS. 15A to 15F are graphs illustrating an example of correction of the temperature characteristics of an angular velocity signal according to the second embodiment.

FIG. 16 is a diagram illustrating a configuration example of an angular velocity detection apparatus according to a third embodiment of the invention.

FIGS. 17A to 17E are graphs illustrating an example of correction of the temperature characteristics of an angular velocity signal according to the third embodiment.

FIG. 18 is a diagram illustrating a configuration example of an angular velocity detection apparatus according to a fourth embodiment of the invention.

FIGS. 19A to 19F are graphs illustrating an example of correction of the temperature characteristics of an angular velocity signal according to the fourth embodiment.

FIG. 20 is a functional block diagram of an electronic instrument.

DETAILED DESCRIPTION

OF THE EMBODIMENT

The invention may provide an angular velocity detection apparatus and an electronic instrument that can compensate for a change in temperature characteristics of the angular velocity signal due to the vibration leakage component without using a higher-order temperature compensation circuit.

(1) According to one embodiment of the invention, there is provided an angular velocity detection apparatus including:

a vibrator that generates a signal that includes an angular velocity component corresponding to the magnitude of an angular velocity, and a vibration leakage component of vibrations based on a drive signal;

a driver section that generates the drive signal, and supplies the drive signal to the vibrator;

an angular velocity signal generation section that extracts the angular velocity component from the signal generated by the vibrator, and generates an angular velocity signal corresponding to the magnitude of the angular velocity component;

a vibration leakage signal generation section that extracts the vibration leakage component from the signal generated by the vibrator, and generates a vibration leakage signal corresponding to the magnitude of the vibration leakage component; and

an adder-subtractor section that adds the vibration leakage signal to the angular velocity signal, or subtracts the vibration leakage signal from the angular velocity signal, in a given ratio to correct temperature characteristics of the angular velocity signal.

The angular velocity signal generation section may extract the angular velocity component from the signal generated by the vibrator based on a first detection signal that is synchronized with the drive signal, for example. The vibration leakage signal generation section may extract the vibration leakage component from the signal generated by the vibrator based on a second detection signal that is synchronized with the drive signal and differs in phase from the first detection signal, for example.

According to the above embodiment, the temperature characteristics of the angular velocity signal can be corrected by adding the vibration leakage signal to the angular velocity signal, or subtracting the vibration leakage signal from the angular velocity signal, in a given ratio, on the assumption that the temperature characteristics of the angular velocity signal and the temperature characteristics of the vibration leakage signal have a correlation. This makes it possible to compensate for a change in temperature characteristics of the angular velocity signal due to the vibration leakage component without using a higher-order temperature compensation circuit.

(2) The above angular velocity detection apparatus may further include a first first-order temperature adjustment section that adjusts a first-order component of the temperature characteristics of the angular velocity signal input to the adder-subtractor section to approach a first value, and a second first-order temperature adjustment section that adjusts a first-order component of temperature characteristics of the vibration leakage signal input to the adder-subtractor section to approach a second value.

The first value and the second value may be selected based on the relationship between the temperature characteristics of the angular velocity signal and the temperature characteristics of the vibration leakage signal so that the temperature characteristics of the angular velocity signal are corrected by addition or subtraction by the adder-subtractor section. For example, the first value and the second value may be set to an identical value when the temperature characteristic curve of the angular velocity signal and the temperature characteristic curve of the vibration leakage signal bend similarly, and the adder-subtractor section may subtract the vibration leakage signal from the angular velocity signal in the given ratio. The first value and the second value may be set to values that differ in sign and have the same absolute value when the temperature characteristic curve of the angular velocity signal and the temperature characteristic curve of the vibration leakage signal bend in an opposite way, and the adder-subtractor section may add the vibration leakage signal to the angular velocity signal in the given ratio.

This makes it possible to implement a temperature compensation process on the angular velocity signal even when the first-order component of the temperature characteristics of the angular velocity signal and the first-order component of the temperature characteristics of the vibration leakage signal differ to a large extent.

(3) The above angular velocity detection apparatus may further include a first-order temperature adjustment section that adjusts one of a first-order component of the temperature characteristics of the angular velocity signal input to the adder-subtractor section and a first-order component of temperature characteristics of the vibration leakage signal input to the adder-subtractor section to approach the other of the first-order component of the temperature characteristics of the angular velocity signal and the first-order component of the temperature characteristics of the vibration leakage signal.

This makes it possible to implement a temperature compensation process on the angular velocity signal even when the first-order component of the temperature characteristics of the angular velocity signal and the first-order component of the temperature characteristics of the vibration leakage signal differ to a large extent.

(4) The above angular velocity detection apparatus may further include a first-order temperature correction section that corrects a first-order component of temperature characteristics of a signal obtained by the adder-subtractor section.

This makes it possible to implement a more accurate temperature compensation process on the angular velocity signal even when the first-order component of the temperature characteristics of the angular velocity signal and the first-order component of the temperature characteristics of the vibration leakage signal differ to a large extent.

(5) The above angular velocity detection apparatus may further include a terminal that outputs a signal based on the vibration leakage signal to the outside.

The signal based on the vibration leakage signal may be the vibration leakage signal, or may be a signal obtained by performing a specific process (e.g., amplification) on the vibration leakage signal.

The presence or absence of failure of the angular velocity detection apparatus can be externally determined by monitoring the signal based on the vibration leakage signal on the assumption that the amplitude of the vibration leakage component is constant independently of the angular velocity.

(6) The above angular velocity detection apparatus may further include a failure determination section that determines the presence or absence of failure of the angular velocity detection apparatus based on the vibration leakage signal.

This makes it possible for the angular velocity detection apparatus to determine the presence or absence of failure of the angular velocity detection apparatus. If the determination result signal of the failure determination section is output to the outside, the presence or absence of failure of the angular velocity detection apparatus can be externally determined by monitoring the signal output from the failure determination section.

(7) In the above angular velocity detection apparatus, the adder-subtractor section may include an inverting amplifier that inverts a polarity of an input signal, a switch circuit that selects whether or not to bypass the inverting amplifier, and a variable gain amplifier that is disposed in series with the inverting amplifier, and amplifies or attenuates an input signal by a gain that can be variably set, may select whether or not to add a signal obtained by inverting a polarity of the vibration leakage signal to the angular velocity signal using the inverting amplifier and the switch circuit, and may select a ratio of the vibration leakage signal added to the angular velocity signal using the variable gain amplifier.

This makes it possible to select whether or not to invert the polarity of the vibration leakage signal based on the connection setting of the switch circuit, and amplify or attenuate the vibration leakage signal to the desired level based on the gain setting of the variable gain amplifier. Therefore, even if the level or the polarity of the temperature characteristics of the vibration leakage signal varies, the temperature characteristics of the vibration leakage signal can be caused to approach the temperature characteristics of the angular velocity signal or temperature characteristics obtained by inverting the polarity of the temperature characteristics of the angular velocity signal. This makes it possible to implement a temperature compensation process on the angular velocity signal.

(8) According to another embodiment of the invention, there is provided an electronic instrument including the above angular velocity detection apparatus.

Exemplary embodiments of the invention are described in detail below with reference to the drawings. Note that the following embodiments do not unduly limit the scope of the invention as stated in the claims. Note also that all of the elements described below should not necessarily be taken as essential elements of the invention.

1. ANGULAR VELOCITY DETECTION APPARATUS 1-1. First Embodiment

FIG. 1 is a diagram illustrating a configuration example of an angular velocity detection apparatus according to a first embodiment of the invention.

An angular velocity detection apparatus 1 according to the first embodiment includes a gyro sensor element 100 and an angular velocity detection IC 10.

The gyro sensor element 100 (i.e., vibrator) includes a vibrating element that includes a drive electrode and a detection electrode and is sealed in a package (not shown). The package normally has seal-tightness in order to reduce the impedance of the vibrating element to improve the vibration efficiency as much as possible.

The vibrating element of the gyro sensor element 100 may be formed of a piezoelectric material such as a piezoelectric single crystal (e.g., quartz crystal (SiO2), lithium tantalate (LiTaO3), or lithium niobate (LiNbO3)) or a piezoelectric ceramic (e.g., lead zirconate titanate (PZT)), or may have a structure in which a piezoelectric thin film (e.g., zinc oxide (ZnO) or aluminum nitride (AlN)) is disposed between the drive electrodes on the surface of semiconductor silicon.

In this embodiment, the gyro sensor element 100 is formed using a double-T-shaped vibrating element that includes two T-shaped drive vibrating arms. The vibrating element may have a tuning-fork structure, or a tuning-bar structure in the shape of a triangular prism, a quadrangular prism, or a column, for example.

FIG. 2 is a diagram illustrating the vibrating element of the gyro sensor element 100 according to this embodiment.

The gyro sensor element 100 according to this embodiment includes a double-T-shaped vibrating element that is formed using a Z-cut quartz crystal substrate. A vibrating element formed of a quartz crystal has an advantage in that the angular velocity detection accuracy can be improved since the resonance frequency changes to only a small extent due to a change in temperature. Note that the X-axis, the Y-axis, and the Z-axis illustrated in FIG. 2 indicate the axes of the quartz crystal.

As illustrated in FIG. 2, the vibrating element of the gyro sensor element 100 includes drive vibrating arms 101a and 101b that extend respectively from drive bases 104a and 104b in the +Y-axis direction and the −Y-axis direction. Drive electrodes 112 and 113 are respectively formed on the side surface and the upper surface of the drive vibrating arm 101a, and drive electrodes 113 and 112 are respectively formed on the side surface and the upper surface of the drive vibrating arm 101b. The drive electrodes 112 and 113 are connected to a driver circuit 20 respectively via an external output terminal 11 and an external input terminal 12 of the angular velocity detection IC 10 illustrated in FIG. 1.

The drive bases 104a and 104b are connected to a rectangular detection base 107 via connection arms 105a and 105b that respectively extend in the −X-axis direction and the +X-axis direction.

Detection vibrating arms 102 extend from the detection base 107 in the +Y-axis direction and the −Y-axis direction. Detection electrodes 114 and 115 are formed on the upper surface of the detection vibrating arms 102, and common electrodes 116 are formed on the side surface of the detection vibrating arms 102. The detection electrodes 114 and 115 are connected to a detection circuit 30 respectively via external input terminals 13 and 14 of the angular velocity detection IC 10 illustrated in FIG. 1. The common electrodes 116 are grounded.

When an alternating voltage (drive signal) is applied between the drive electrodes 112 and 113 of the drive vibrating arms 101a and 101b, the drive vibrating arms 101a and 101b produce flexural vibrations (excited vibrations) so that the ends of the drive vibrating arms 101a and 101b repeatedly move closer and away (see arrow B) due to an inverse piezoelectric effect (see FIG. 3).

When an angular velocity around the Z-axis is applied to the vibrating element of the gyro sensor element 100, the drive vibrating arms 101a and 101b are subjected to a Coriolis force in the direction that is perpendicular to the direction of the flexural vibrations (see arrow B) and the Z-axis. Therefore, the connection arms 105a and 105b produce vibrations (see arrow C), as illustrated in FIG. 4. The detection vibrating arms 102 produce flexural vibrations (see arrow D) in synchronization with the vibrations (see arrow C) of the connection arms 105a and 105b. The vibrations of the detection vibrating arms 102 based on the Coriolis force differ in phase from the flexural vibrations (excited vibrations) of the drive vibrating arms 101a and 101b by 90°.

The vibration energy of the drive vibrating arms 101a and 101b is balanced when the magnitude of the vibration energy or the vibration amplitude of the drive vibrating arms 101a and 101b is equal when the drive vibrating arms 101a and 101b produce flexural vibrations (excited vibrations), and the detection vibrating arm 102 does not produce flexural vibrations in a state in which an angular velocity is not applied to the gyro sensor element 100. However, when the balance of the vibration energy of the drive vibrating arms 101a and 101b is lost, the detection vibrating arm 102 produces flexural vibrations even if an angular velocity is not applied to the gyro sensor element 100. The above flexural vibrations are referred to as leakage vibrations. The leakage vibrations are flexural vibrations (see arrow D) in the same manner as the vibrations based on the Coriolis force, but occur in the same phase as the drive signal.

An alternating charge based on the flexural vibrations occurs in the detection electrodes 114 and 115 of the detection vibrating arms 102 due to a piezoelectric effect. An alternating charge that is generated based on the Coriolis force changes depending on the magnitude of the Coriolis force (i.e., the magnitude of the angular velocity applied to the gyro sensor element 100). On the other hand, an alternating charge that is generated based on the leakage vibrations is constant independently of the magnitude of the angular velocity applied to the gyro sensor element 100.

A rectangular weight section 103 that is wider than the drive vibrating arms 101a and 101b is formed at the end of the drive vibrating arms 101a and 101b. This makes it possible to increase the Coriolis force while obtaining the desired resonance frequency using relatively short vibrating arms. A weight section 106 that is wider than the detection vibrating arms 102 is formed at the end of the detection vibrating arm 102. This makes it possible to increase the amount of alternating charge that flows through the detection electrodes 114 and 115.

The gyro sensor element 100 thus outputs an alternating charge (i.e., angular velocity component) that is generated based on the Coriolis force and an alternating charge (i.e., vibration leakage component) that is generated based on the leakage vibrations of the excited vibrations via the detection electrodes 114 and 115 (detection axis: Z-axis).

A Coriolis force Fc applied to the gyro sensor element 100 is calculated by the following expression (1):

Fc=2mvΩ  (1)

where, m is an equivalent mass, v is a vibration velocity, and omega is an angular velocity. As is clear from the expression (1), the Coriolis force changes due to a change in equivalent mass m or vibration velocity v, even if the angular velocity omega is constant. Specifically, the angular velocity detection sensitivity changes due to a change in equivalent mass m or vibration velocity v. When the vibration state of the vibrating element of the gyro sensor element 100 has changed due to failure, the equivalent mass m or the vibration velocity v of the driving vibrations changes, so that the detection sensitivity changes. The state of the leakage vibrations also changes due to a change in equivalent mass m or vibration velocity v, so that the magnitude of the vibration leakage component changes. Specifically, the magnitude of the vibration leakage component has a correlation with the angular velocity detection sensitivity, and the presence or absence of failure of the gyro sensor element 100 can be determined by monitoring the magnitude of the vibration leakage component.

In this embodiment, the vibration leakage component at the desired level is positively generated by causing the balance of the vibration energy of the drive vibrating arms 101a and 101b to be lost to some extent. In particular, since the gyro sensor element 100 is formed using the double-T-shaped vibrating element, it is easy to cause the flexural vibrations of the drive vibrating arm 101a and the flexural vibrations of the drive vibrating arm 101b to become imbalanced by varying the mass of the weight section 103 at the end of the drive vibrating arm 101a and the weight section 103 at the end of the drive vibrating arm 101b.

Again referring to FIG. 1, the angular velocity detection IC 10 includes the driver circuit 20, the detection circuit 30, a reference power supply circuit 40, and a memory 50.

The driver circuit 20 includes an I/V conversion circuit (current/voltage conversion circuit) 210, an AC amplifier circuit 220, and an amplitude adjustment circuit 230.

The I/V conversion circuit 210 converts a drive current that flows through the vibrating element of the gyro sensor element 100 into an alternating voltage signal.

The alternating voltage signal output from the I/V conversion circuit 210 is input to the AC amplifier circuit 220 and the amplitude adjustment circuit 230. The AC amplifier circuit 220 amplifies the alternating voltage signal input thereto, clips the signal to a predetermined voltage value, and outputs a square-wave voltage signal 22. The amplitude adjustment circuit 230 changes the amplitude of the square-wave voltage signal 22 based on the level of the alternating voltage signal output from the I/V conversion circuit 210, and controls the AC amplifier circuit 220 so that a constant drive current is maintained.



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stats Patent Info
Application #
US 20140174148 A1
Publish Date
06/26/2014
Document #
14169575
File Date
01/31/2014
USPTO Class
73/137
Other USPTO Classes
International Class
01P21/00
Drawings
21


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Measuring And Testing   Instrument Proving Or Calibrating   Speed, Velocity, Or Acceleration