JPH10260043A - Angular velocity detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect angular velocity of high S/N by coincide the excitation direction of second and third both vibration pieces and the lengthwise direction of a first vibration piece with the Y-direction, and cutting leakage vibration against the first vibration piece. SOLUTION: When an excitation circuit is driven so as to output rectangular waves of duty ratio one to one and opposite phase to each other to output terminals, a first vibration piece 11 and a second vibration piece 12 vibrate in-phase in the Y-direction. Namely, the second vibration piece 12 and a third vibration piece 13 are simultaneously bent in the direction of +Y, thereafter simultaneously bent in the direction of -Y, and then this is continuously repeated hereafter. The vibration phase is deviated from the phase of an excitation signal by 90 deg.. When a vibrator 10 stands still, the second vibration piece 12 and the third vibration piece 13 only vibrate in the Y-direction, and because the first vibration piece 11 is connected to them at the node of the vibration, force in the Y-direction is only applied to the first vibration piece 11. Consequently, the excitation vibration is hardly leaked to the first vibration piece 11. Therefore, excitation vibration of noise is not leaked into vibration to be detected, and hence angular velocity of high S/N can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity detecting device used for an automobile navigation system and attitude control, and more particularly to a vibration type angular velocity detecting device.

[0002]

2. Description of the Related Art Conventionally, there has been known a vibration type angular velocity detecting device utilizing the fact that when a vibrator is rotated, a new vibration corresponding to the rotational angular velocity is generated by Coriolis force. Among them, Japanese Patent Application Laid-Open No. 7-167883 describes that the vibrating piece for excitation of the vibrator and the vibrating piece for detection are orthogonal to each other.
There is known a vibration type angular velocity detecting device described in the above publication.

The vibrator of this vibration type angular velocity detecting device has a shape in which each of the U-shaped ends is bent outward at right angles, and the opposing portions on the root side from the bent portion are used as excitation vibrating reeds. The portion ahead of the bent portion is used as the detecting resonator element. According to this vibrator, when the exciting vibrating piece is excited, the detecting vibrating piece also vibrates in the exciting vibration direction, that is, in its own longitudinal direction. When the vibrator rotates in the vertical direction, the vibrating piece for detection vibrates in the direction perpendicular to the excitation vibration direction due to the Coriolis force. By detecting the amplitude of the vibration due to the Coriolis force generated in the detecting vibrating piece in this manner, the rotational angular velocity can be detected.

[0004]

However, in the prior art, when the excitation vibrating piece is excited, the detecting vibrating piece vibrates in the direction of rotational movement about the root of the exciting vibrating piece. Therefore, the detecting vibrating piece vibrates not only in the longitudinal direction but also in the direction perpendicular thereto, and the leak vibration in the same direction is superimposed on the vibration due to the Coriolis force to be detected.

Since the phase of the vibration due to the Coriolis force and the phase of the leakage vibration are shifted by 90 degrees, the leakage vibration of the excitation vibration, which is a noise component, is removed from the vibration of the detecting vibrating piece, and only the vibration due to the Coriolis force is removed. It is possible to extract. However, the removal of leakage vibration is not always perfect,
In order to increase the detection accuracy, an angular velocity detection device that does not cause leakage vibration of the excitation vibration in the detection vibration piece has been required.

[0006]

SUMMARY OF THE INVENTION An angular velocity detecting device according to the present invention has been made to solve such a problem, and is fixed to an object to be detected whose angular velocity is to be detected in an XYZ three-dimensional coordinate space. A first vibrating reed protruding in the direction of + Y from the base, a second vibrating reed protruding in the direction of + X from the tip of the first vibrating reed, and a A vibrator having three vibrating pieces; an exciting means for exciting the second vibrating piece and the third vibrating piece in phase in the Y direction; a detecting means for detecting a vibration amplitude of the first vibrating piece in the X direction; And angular velocity calculating means for calculating a rotational angular velocity about the Z direction from the magnitude of the amplitude detected by the above.

According to this angular velocity detecting device, the exciting directions of the second vibrating piece and the third vibrating piece as the exciting vibrating pieces and the longitudinal direction of the first vibrating piece as the detecting vibrating piece coincide with the Y direction. In addition, when the second vibrating piece and the third vibrating piece are excited in the same phase, the second vibrating piece, the third vibrating piece, and the first vibrating piece are connected to each other at a node of the coupled vibration by the two vibrating pieces. Therefore, the leakage vibration that is the vibration in the Y direction is not transmitted to the first vibrating piece.

In the angular velocity detecting device according to the present invention, it is desirable to provide a fourth vibrating reed projecting in the direction of + Y from the tip of the first vibrating reed.

By adjusting the length and the like of the fourth vibrating reed, the natural frequency of the first vibrating reed as the detecting vibrating reed can be changed.
The natural frequencies of the resonator element can be easily matched, and the sensitivity can be improved.

[0010]

FIG. 1 is a perspective view showing a vibrator used in an angular velocity detecting device according to an embodiment of the present invention. The vibrator 10 includes a first vibrating reed 11, a second vibrating reed 1
A second vibrating piece 13 and a vibrator base 14 are provided, which are integrally formed of a metal material called an elinvar, which is an iron-nickel alloy. The integral structure can be manufactured by grinding or the like, and the reason why the elinvar is used as the material is that the temperature characteristics of the elastic coefficient are relatively stable.

Here, the positional relationship, the shape, and the like of each element constituting the vibrator 10 will be described using XYZ three-dimensional spatial coordinates whose directions are shown in FIG. First vibrating bar 11
Is a flat plate parallel to the YZ plane extending in the + Y direction from the vibrator base 14 fixed directly or indirectly to the object to be detected of the angular velocity. The second vibrating bar 12 is a flat plate extending from the tip of the first vibrating bar 11 in the + X direction and parallel to the XZ plane. The third vibrating reed 13 is a flat plate parallel to the XZ plane extending in the −X direction from the tip of the first vibrating reed 11. The thicknesses of the first to third vibrating bars 11 to 13 are all equal,
The widths of the respective vibrating bars in the Z direction are also equal to each other. The lengths of the second vibrating bar 12 and the third vibrating bar 13 in the longitudinal direction (X direction) are also equal.

A piezoelectric element 15 in which PZT (lead zirconate titanate), which is a piezoelectric material, is sandwiched between two electrodes is provided on one of the surfaces of the first resonator element 11 parallel to the YZ plane. One electrode of the element 15 is tightly fixed to the first resonator element 11. Second vibrating bar 12 and third vibrating bar 13
Each of the planes parallel to the XZ plane of
5, piezoelectric elements 16 and 17 are provided.
One electrode of each of the piezoelectric elements 16 and 17 is tightly fixed to the corresponding resonator element. Both electrodes of the piezoelectric element 15 are connected to input terminals of a detection circuit described later, and both electrodes of the piezoelectric elements 16 and 17 are connected to output terminals of an excitation circuit described later.

The piezoelectric element 15 is used for detecting vibration, and dielectric polarization occurs in PZT in response to expansion and contraction in the Y direction, and electric charges appear on two electrodes. The first resonator element 11 is +
When bent in the X direction, the piezoelectric element 15 contracts in the Y direction, and when bent in the -X direction, the piezoelectric element 15 expands in the Y direction. Therefore, when the first vibrating piece 11 vibrates in the X direction, an AC voltage having the same frequency as the vibration frequency is applied to the piezoelectric element 1.
Appears between 5 electrodes.

The piezoelectric elements 16 and 17 are used for excitation. When an AC voltage is applied between the electrodes, the piezoelectric elements 16 and 17 expand and contract in the X direction at the same frequency as the AC voltage. Piezoelectric elements 16 and 17
Extend, both the second vibrating piece 12 and the third vibrating piece 13 bend in the -Y direction, and when the piezoelectric elements 16 and 17 contract, both vibrating pieces bend in the + Y direction. Therefore, by applying an AC voltage to the piezoelectric elements 16 and 17, the second vibrating piece 12 and the third vibrating piece 13
Vibrates in the direction at the same frequency as the applied alternating current.

FIG. 2 is a circuit diagram showing an exciting circuit, a detecting circuit, and an angular velocity calculating circuit used in the angular velocity detecting device of the present embodiment. FIG. 3 is a waveform diagram showing input / output waveforms for these circuits.

The excitation circuit 21 has an oscillation circuit 22 and outputs a rectangular wave having a duty ratio of 1 to 1 as shown in FIG. The upper part of FIG. 3B shows the output waveform of the output terminal 23, and the lower part of FIG. 3B shows the output waveform of the output terminal 24, both of which have opposite phases. Output terminal 2
3 is connected to the electrode of the piezoelectric elements 16 and 17 on the side attached to the vibrating reed, and the output terminal 24 is connected to the piezoelectric elements 16 and 1
7 is connected to the other electrode, that is, the exposed electrode.

The detection circuit 25 is a circuit for detecting the vibration amplitude of the first resonator element 1 and includes a differential amplifier circuit 26, a synchronous detection circuit 27, an integration circuit 28, a DC amplification circuit 29, and an offset adjustment circuit 30. .

The differential amplifier circuit 26 is a circuit for performing differential amplification of signals input to the input terminals 31 and 32. The input terminal 31 is connected to an electrode of the piezoelectric element 15 on the side attached to the vibrating reed. , The input terminal 32 is connected to the other electrode of the piezoelectric element 15. Therefore, signals having phases opposite to each other are input to input terminals 31 and 32.

When the first vibrating reed 11 is vibrating in the X direction, sine waves of opposite phases are given to the input terminals 31 and 32 as shown in the upper and lower parts of FIG.
The differential amplifier circuit 26 outputs a differential amplified signal as shown in FIG. 3D indicating the input signal level of the terminal 31 based on the input signal level of the terminal 32.

The synchronous detection circuit 27 is a circuit for detecting the AC signal output from the differential amplifier circuit 26 by using one output signal of the oscillation circuit 22 as a detection signal. The AC signal output from the differential amplifying circuit 26 is 90 degrees out of phase with the excitation vibration of the first vibrating reed 11 and the second vibrating reed 12 as described later, and is in phase with one output signal of the oscillation circuit 22. Therefore, this output signal can be used as a detection signal.

The integration circuit 28 is a circuit for smoothing the output signal of the synchronous detection circuit 27, and its output value corresponds to the output signal amplitude of the differential amplifier circuit 26. Therefore,
It also indicates the vibration amplitude of the first vibrating reed 11.

The DC amplifying circuit 29 is a circuit for amplifying the output signal of the integrating circuit 28 in order to facilitate subsequent signal processing. The offset adjusting circuit 30 removes an offset component caused by the characteristics of the vibrator. At the same time, the circuit shifts the output voltage to a desired potential (here, 2.5 V) when the vibrator is stationary, that is, when the output value of the differential amplifier circuit 26 is zero. The output signal of the offset adjustment circuit 30 is input to the angular velocity calculation circuit 35 via the output terminal 33.

The angular velocity calculating circuit 35 calculates a rotational angular velocity about an axis parallel to the Z axis of the vibrator 1 based on an output signal of the detecting circuit 25 indicating a vibration amplitude of the first vibrating reed 11 and an angular velocity and Coriolis. This is a circuit that calculates based on a relational expression with force.

Next, the operation of the angular velocity detecting device according to the present embodiment will be described. FIG. 4 is a plan view showing a state when the second vibrating piece 12 and the third vibrating piece 13 of the vibrator 1 shown in FIG. 1 are excited. When the excitation circuit 21 is driven to output to the output terminals 23 and 24 rectangular waves having mutually opposite phases and a duty ratio of 1: 1 as shown in FIG.
As shown in FIG. 4, the first and second resonator elements 12
Vibrates in the direction. That is, the second resonator element 12 and the third
The vibrating piece 13 simultaneously bends in the + Y direction after being simultaneously bent in the −Y direction, and thereafter repeats this continuously.
The vibration phase is 90 degrees out of phase with the excitation signal as shown in FIG. The excitation frequency is made substantially equal to the natural frequency of the coupled vibration of the second vibrating bar 12 and the third vibrating bar 13.

When the vibrator 10 is stationary, the second
The vibrating reed 12 and the third vibrating reed 13 only vibrate in the Y direction as described above, and the first vibrating reed 11 is connected at a node of the vibration.
Applies only a force in the Y direction. Therefore, the excitation vibration hardly leaks to the first vibrating reed 11.

When the vibrator 10 rotates about an axis parallel to the Z-axis, the second vibrating piece 12 and the third vibrating piece 13 vibrating in the X direction correspond to the rotational angular velocity ω shown in the following equation (1). Coriolis force F is applied.

F = 2 mV × ω (1) where m is the mass of the vibrating reed, and V is the vibration speed.

The Coriolis force will be described with reference to FIG. 4. When the vibrator 10 is rotating at an angular velocity ω about an axis parallel to the Z axis, the excitation causes + Y as indicated by arrows A and B. Vibrating reed 12 and third vibrating reed 1 in the direction of
3, a Coriolis force F as shown by arrows C and D is generated. Since this Coriolis force is proportional to the speed V, it becomes maximum when the second vibrating bar 12 and the third vibrating bar 13 are linear. The forces indicated by the arrows C and D are transmitted to the first vibrating reed 11 and bend the first vibrating reed 11 in the direction of the arrow E. Similarly, when the second vibrating piece 12 and the third vibrating piece 13 move in the −Y direction, the second vibrating piece 1
A Coriolis force in the + X direction acts on the second and third vibrating bars 13, and this force causes the first vibrating bar 11 to bend in the + X direction.

With the above operation, the first vibrating reed 1
1 vibrates in the X direction with an amplitude proportional to the angular velocity ω. The piezoelectric element 15 generates a voltage between the electrodes in accordance with the vibration amplitude.
1 and 32 are input. The detection circuit 25 processes the input signal as described above and outputs a signal indicating a voltage value corresponding to the vibration amplitude of the first vibrating reed 11 to the output terminal 33.

The signal at the output terminal 33 is supplied to an angular velocity arithmetic circuit 35.
To calculate the angular velocity ω by calculation. FIG. 5 is a graph showing the relationship between the voltage and the angular velocity conversion executed in the angular velocity calculation circuit 35. In the figure, the horizontal axis represents the angular velocity (yaw), and the vertical axis represents the output signal voltage of the detection circuit 25. Since the detection circuit 25 is adjusted to output a voltage of 2.5 V when the vibrator 10 is stationary, this graph shows that the output voltage of the detection circuit 25 is 2.5 V and the angular velocity is A straight line passes through the zero point, and the angular velocity is calculated from the output of the detection circuit based on this straight line.

FIG. 6 shows a vibrator 60 used in an angular velocity detecting device according to a second embodiment of the present invention.
The vibrator 60 has a structure including two vibrators 10 according to the first embodiment. That is, the vibrator base 64
The first vibrator is provided on the + Y side and the second vibrator is provided on the -Y side. The first vibrator receives +
A first vibrating reed 61 protruding in the Y direction;
Are provided with a second vibrating piece 62 and a third vibrating piece 63 which respectively protrude in the + X and -X directions from the tip of the. Second
The vibrator includes a first vibrating piece 65 protruding from the vibrator base 64 in the -Y direction, a second vibrating piece 66 and a third vibrating piece protruding from the tip of the first vibrating piece 65 in the + X and -X directions, respectively. The vibrating piece 67 is provided. First vibrating bars 61 and 6
5 is provided with a detecting piezoelectric element, and a second vibrating reed 62,
The 66 and the third vibrating bars 63 and 67 are provided with piezoelectric elements for excitation, respectively. Note that fixed bases 68 and 69 are provided at both ends of the vibrator base 64, respectively.

The second vibrating piece 62 of the first vibrator and the third vibrating piece
The vibrating bar 63 is excited in the same direction in the Y direction, and at the same time, the second vibrating bar 66 and the third vibrating bar 67 of the second vibrator are in the same phase as each other and in the opposite phase to the second vibrating bar 62 and the third vibrating bar 63. Excit so that When the vibrator 60 rotates about an axis parallel to the Z-axis in this excited state, the first vibrating pieces 61 and 65 are driven by the Coriolis force at an amplitude corresponding to the rotational angular velocity.
Since it vibrates in the direction, the angular velocity can be obtained by detecting the vibration amplitude as in the first embodiment. In addition, in the case of the vibrator 60, the second vibrating bars 62, 66
In addition, the center of gravity does not move due to the excitation of the third vibrating bars 63 and 67. Therefore, even slight vibration leakage from the vibrator base can be suppressed.

FIG. 7 shows a vibrator 70 used in an angular velocity detecting device according to a third embodiment of the present invention.
The vibrator 70 is obtained by adding a fourth vibrating piece 75 to the vibrator 10 of the first embodiment. The fourth resonator element 75 is the first
The vibrating reed has a free end protruding in the + Y direction so as to further extend the vibrating reed 11. The fourth resonator element 75
By adjusting the length and the like, the X of the first vibrating piece 11
The natural frequency of the directional vibration can be easily set to a desired value.

[0034]

As described above, according to the angular velocity detecting device of the present invention, the second vibrating piece and the third vibrating piece, which are vibrating pieces for excitation, are used.
Excitation vibration of the vibrating reed does not leak to the first vibrating reed, which is the detecting vibrating reed. That is, there is no leakage of the excitation vibration which is noise during the vibration to be detected. Therefore, S / N
Angular velocity detection with a high ratio is possible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a vibrator used in an angular velocity detecting device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an excitation circuit, a detection circuit, and an angular velocity calculation circuit used in the angular velocity detection device according to the first embodiment of the present invention.

FIG. 3 is a timing chart showing the operation.

FIG. 4 is a plan view for explaining excitation vibration of a vibrator and vibration based on Coriolis force.

FIG. 5 is a characteristic diagram showing a relationship between a detection circuit output voltage and an angular velocity used in the angular velocity calculation circuit.

FIG. 6 is a perspective view showing a vibrator used in an angular velocity detecting device according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a vibrator used in an angular velocity detecting device according to a third embodiment of the present invention.

[Explanation of symbols]

10, 60, 70 ... vibrator, 11, 61, 65 ... first vibrating reed, 12, 62, 66 ... second vibrating reed, 13, 63, 6
7: third vibrating reed, 14, 64: vibrator base, 21: excitation circuit, 25: detection circuit, 35: angular velocity calculation circuit.

Claims (2)

[Claims] 1. In an XYZ three-dimensional coordinate space, a base fixed to a detection target whose angular velocity is to be detected is + Y
A first vibrating reed protruding in the direction of +, a second vibrating reed protruding in the + X direction from the tip of the first vibrating reed, and a third vibrating reed protruding in the -X direction from the tip of the first vibrating reed. An exciting unit that excites the second vibrating bar and the third vibrating bar in the same direction in the Y direction; a detecting unit that detects a vibration amplitude of the first vibrating bar in the X direction; Angular velocity calculating means for calculating a rotational angular velocity about the Z direction from the magnitude of the amplitude detected by the method. 2. The apparatus according to claim 1, further comprising a fourth vibrating reed protruding in a + Y direction from a tip of said first vibrating reed.
3. The angular velocity detecting device according to claim 1.