JPH04118515A - Angular speed detector and acceleration detector - Google Patents

Abstract

PURPOSE:To obtain a angular speed and acceleration signals which are not affected by acceleration and Corioli's force by constituting the mechanical unit of a tuning fork member, vibration member, and stress detection member. CONSTITUTION:When acceleration is applied in the oscillation direction (y-y) of a tuning fork member 1, homopolar and same level stress detecting voltage are generated in piezoelectric elements 2 and 3, and the difference is zero even if acceleration is further applied. Therefore, taking the difference between the detected voltage of the elements 2 and 3, the differential voltage is affected by the acceleration applied to the vibration and the direction of the vibration of the member 1 caused by piezoelectric elements 4 and 5, angular speed can be known by this differential voltage. On the other hand, taking the sum of the detected voltage, sum voltage corresponds to the stress caused by vibration and acceleration, but is not affected by the stress cased by Corioli's force. If the affected quantity of vibration is subtracted from this sum voltage, the differential voltage becomes the acceleration applied in the direction of the vibration which is not affected by rotation and vibration.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an angular velocity detector called a so-called vibrating gyro that detects its own rotation and outputs a signal according to the rotation, and , from another point of view, relates to an acceleration detector that outputs a signal according to acceleration applied to itself.

The angular velocity detector or acceleration detector of the present invention is, for example, an angular velocity sensor and/or acceleration sensor used for navigation of automobiles, aircraft, ships, etc., and automobiles used for attitude control, brake control, 4WS control, 4WD control, etc. of automobiles. The present invention can be used as an angular velocity sensor and/or acceleration sensor for detecting motion of a robot arm, an angular velocity sensor and/or acceleration sensor used for multi-axis control of a robot arm, etc.

(Prior Art) A so-called vibrating gyroscope generally has a structure as shown in FIG. In other words, a pair of opposing mechanical oscillators, such as tuning forks, are driven by a drive element in the direction of approaching and moving away from each other, giving them vibrations with a phase shift of 180 degrees to create an inertial force, which causes the rotation of the base. Coriolis acting on the vibrator is detected by a detection element attached to the tuning fork. Since Coriolis changes according to the angular velocity ω, the angular velocity of rotation can be detected by detecting the deflection of the tuning fork caused by Coriolis using a strain detection element such as a piezoelectric element. JP-A-62-101+
No. 109 proposes a vibrating gyroscope that detects torsion of a connecting member connecting the centers of a pair of disc-shaped vibrators.

The present applicant has already proposed improvements to this type of vibrating gyroscope (Japanese Patent Application No. 63-283157, Japanese Patent Application No. 63-283)
-283158 (Japanese Patent Application No. 1983-283] 59 and Japanese Patent Application No. 1-284542).

(Problems to be Solved by the Invention) Conventional vibrating gyroscopes have had the following various drawbacks.

If the shape of the first point tuning fork is complicated or not symmetrical with respect to the vibration plane, the waveform of steady vibration is distorted from a simple harmonic motion of a sine wave. Therefore, the detected angular velocity contains a considerable error, and the rotation angle obtained by integrating the detected angular velocity contains a considerable error (
deviation).

Second point: It is difficult to manufacture a tuning fork at the intended resonance frequency. Many man-hours are required to adjust the resonant frequency of the tuning fork, detection sensitivity, etc.

The number of elements is large, such as the constituent elements of the third tuning fork, the vibrator that excites the tuning fork, and the sensor that detects Coriolis. Many man-hours are required for assembly.

The present invention was made with the aim of improving these conventional problems.

[Structure of the invention]

(Means for Solving the Problems) The angular velocity detector of the present invention includes a tuning fork member (1), an excitation member ( 4, 5), and the tuning fork member (1
), and the central axis (z) of the tuning fork member (1)
first and second stress detection members (2) mounted at symmetrical positions with respect to a plane extending in the direction of the vibration (Fi).
, 3).

The acceleration detector of the present invention includes a tuning fork member (1), an excitation member (4, 5) that excites vibration (Fi) around the central axis of the tuning fork member (1) in the tuning fork member, and (1)
first and second stress detection members ( 2,
3).

Note that symbols in parentheses indicate corresponding elements in the embodiments shown in the drawings and described later.

(Function) According to the angular velocity detector of the present invention, since the first and second stress detection members (2, 3) are located at symmetrical positions with respect to the vibration direction (y) of the tuning fork member (1), the tuning fork member (1) ) The first and second stress detecting members (2°3) simultaneously detect the stress caused by the vibrations in the same phase. Further, when acceleration acts in a direction (y) parallel to the vibration direction of the tuning fork member (1), both the first and second stress detection members (2, 3) are substantially of the same polarity corresponding to the acceleration. Generate stress detection signals of the same level. Therefore, the first and second stress detection members (2
, 3), it is the tuning fork member (1)
It becomes zero level without being affected by the vibration of and the acceleration in the vibration direction (y). By the way, when the tuning fork member (1) rotates, for example, around the central axis (z), Coriolis perpendicular to the vibration direction is generated.
One of the stress detection members (2, 3) detects positive stress and the other detects negative stress. Therefore, the difference between the detection signals of the first and second stress detection members (2, 3) indicates a value corresponding to Coriolis. That is, Coriolis is detected at twice the signal level detected by one stress detection member. Since this Coriolis is proportional to the rotational angular velocity, the difference between the detection signals of the first and second stress detection members (2, 3) indicates the angular velocity. In this way, by obtaining the difference between the detection signals of the first and second stress detection members (2, 3), an angular velocity signal that is substantially unrelated to the vibration of the tuning fork member (1) and the acceleration applied in the direction of the vibration can be obtained. is obtained.

This angular velocity detector includes at least one tuning fork member (1),
Since the mechanism section can be constituted by at least one vibrating member (two of 4.5 in the embodiment) and at least two stress detecting members (2, 3), the number of elements is very small, and the number of elements is very small. Three problems will be automatically and significantly improved. In addition to the small number of elements, it is relatively easy to incorporate the vibration members (4, 5) and stress detection members (2, 3) into one tuning fork member (1) in the above-mentioned positional relationship. , the problem of the first point is also significantly improved. In particular, this improvement effect is further enhanced by forming the tuning fork member (1) into a square prism as in the embodiment described later. Furthermore, since only one tuning fork member (1) is used, the resonant frequency can be adjusted simply by cutting its vibrating free end, making it easy to adjust the resonant frequency. , 3) are at symmetrical positions, the difference in detection sensitivity is small. In other words, the fifth problem mentioned above is also improved.

According to the acceleration detector of the present invention, when acceleration acts in the direction (y) parallel to the vibration direction of the tuning fork member (1), both the first and second stress detection members (2, 3) detect acceleration. generate stress detection signals of the same polarity and substantially the same level corresponding to the stress detection signals. In addition to this, stress detection signals corresponding to vibrations are also generated, and these signals are of substantially the same polarity and the same level. Therefore, when the detection signals of the first and second stress detection members (2, 3) are summed, the level of this sum becomes zero as the signal level due to Coriolis caused by rotation is canceled out, and the vibration direction The level corresponds to the acceleration applied to (y) and corresponds to the vibration. The vibration component is generated by the excitation member (45
) corresponds to the electric signal level that excites vibration, so by subtracting that amount from the sum, that is, the sum of the detection signals of the first and second stress detection members (2, 3) and the excitation electric signal level. The difference obtained corresponds to the acceleration applied in the vibration direction (y), which is substantially independent of Coriolis due to rotation. In this way, it is possible to obtain an acceleration signal that is not affected by Coriolis caused by rotation.

This acceleration detector includes at least one tuning fork member (1),
Since the mechanism section can be constituted by at least one vibrating member (two vibrating members 4 and 5 in the embodiment) and at least two stress detecting members (2, 3), the number of elements is very small, and the number of elements is very small. Three problems will be automatically and significantly improved. In addition to the small number of elements, it is relatively easy to incorporate the vibration members (4, 5) and stress detection members (2, 3) into one tuning fork member (1) in the above-mentioned positional relationship. , the problem of the first point is also significantly improved. In particular, this improvement effect is further enhanced by forming the tuning fork member (1) into a square prism as in the embodiment described later. Furthermore, since only one tuning fork member (1) is used, the resonance frequency can be easily adjusted by cutting the vibration free end of the tuning fork member (1), and the resonance frequency can be easily adjusted. 3) are in symmetrical positions, so the difference in detection sensitivity is small. In other words, the fifth problem mentioned above is also improved.

As described above, the angular velocity detector and the acceleration detector of the present invention have exactly the same mechanical elements, and as described above, one set of mechanical elements can generate an angular velocity signal that is not affected by acceleration in the vibration direction (y). At the same time, it is possible to obtain an acceleration signal in the vibration direction (y) that is not affected by Coriolis caused by rotation.

Angular velocity detection and acceleration detection can be performed simultaneously with one set of detection mechanisms.

Other objects and features of the present invention will become clear from the following description of embodiments with reference to the drawings.

(Example) Fig. 1 shows the external appearance of a mechanical part of an embodiment of the present invention, and Fig.
The figure shows the configuration of an electrical circuit connected to the mechanical element.

First, referring to FIG. 1, piezoelectric elements 2 to 5 are bonded to each of the four side surfaces of the tuning fork member 1, respectively.

A vibration absorbing material 6 is fixed to the bottom of the tuning fork member 1.
This vibration absorbing material 6 is fixed to the sensor base 7.

The sensor base 7 is fixed to the inner bottom of the sensor casing 8. In addition, in FIG. 1, the sensor casing 8 is
The entire individual wall and a part of the upper wall are shown broken.

The tuning fork member 1 is a quadrangular prism with a square horizontal cross section. The piezoelectric elements 2 to 5 have substantially the same shape and structure, and have substantially the same vibration characteristics and stress detection characteristics, that is, are mutually equivalent, and are aligned with the central axis (z- z).

In this embodiment, two adjacent piezoelectric elements 4 and 5 are assigned to excite the tuning fork member 1. When the piezoelectric element 4.5 is energized to vibrate at the same period, the same phase, and the same amplitude, the tuning fork member 1 vibrates at the edge (side) where the two side surfaces to which the piezoelectric elements 4.5 are joined intersect, and at the other side opposite to this edge. It vibrates (Fi) in the direction (y-y) along a plane including one edge (the edge where the two side surfaces to which the piezoelectric element 2.3 are joined intersect) and the central axis (zz).

Since the piezoelectric elements 2 and 3 for stress detection are located at symmetrical positions with respect to the plane, they generate stress detection voltages of substantially the same level and phase in response to this vibration (Fi).

Therefore, when the difference in the stress detection voltages of the piezoelectric elements 2.3 is taken, the difference voltage is substantially zero even if the tuning fork member 1 vibrates in the direction (y-y) along the plane.

By the way, if the tuning fork member 1 rotates, for example, around the central axis (z-z) while vibrating (Fl), the direction of vibration (y-y) and the central axis will extend due to this rotation and the vibration. Coriolis Fc is generated in the direction (x) perpendicular to the direction (zz).

This Coriolis Fc produces a tensile stress on one side surface to which the piezoelectric element 2.3 is joined and a compressive stress on the other side, so that the stress detection voltages of the piezoelectric elements 2 and 3 are of opposite polarity.
The levels (absolute values) become substantially equal. Therefore, when taking the difference between the stress detection voltages of the piezoelectric elements 2 and 3, the difference voltage is twice the level of the stress detection voltage of one piezoelectric element corresponding to Coriolis.

By the way, when acceleration is applied to the tuning fork member 1 in the vibration direction (y-y), the piezoelectric elements 2 and 3 generate stress detection voltages having the same polarity and substantially equal levels.

Therefore, when taking the difference between the stress detection voltages of the piezoelectric elements 2 and 3, the difference voltage is substantially zero even if acceleration is applied in the vibration direction <yy>.

As a result of the above, by taking the difference between the stress detection voltages of the piezoelectric elements 2.3, the difference voltage can be determined by the vibration (Fl) of the tuning fork member 1 caused by the piezoelectric elements 4 and 5 and the acceleration applied in the direction of vibration (y-y). The level corresponds to the angular velocity of rotation, and the angular velocity can be determined from this differential voltage.

On the other hand, when the stress detection voltages of the piezoelectric elements 2 and 3 are summed, the sum voltage is the stress caused by the vibration (Fl) and the vibration direction (
This corresponds to the stress due to acceleration applied to y-y), but there is substantially no effect of stress due to Coriolis (rotation). If you subtract the influence of vibration (Fi) from this sum voltage, for example, if you subtract the energizing voltage of piezoelectric elements 4 and 5 (more precisely, the value obtained by multiplying it by a certain coefficient), the resulting difference voltage will be calculated by subtracting the influence of vibration (Fi). It shows the acceleration applied in the vibration direction (y-y) which is substantially eliminated and the influence of vibration (Fl) is substantially eliminated.

Referring to FIG. 2, a piezoelectric element 4 that excites the tuning fork member 1
and 5, an oscillator 9 applies an excitation voltage. The stress detection voltage of the piezoelectric elements 2 and 3 for stress detection is determined by the charge amplifier 1.
0 and 11, respectively. Charge amplifier 10
and 11 have a built-in phase adjustment circuit. These phase adjustment circuits are constructed by placing the tuning fork member 1 in a stationary system and using piezoelectric elements 4.
5 is finely adjusted so that it generates outputs of the same phase when vibrated. The amplification gain is also finely adjusted to produce the same level of output.

The output voltage of charge amplifier 10.11 is applied to differential amplifier 12 and adder 16.

Differential amplifier 12 generates a voltage corresponding to the difference in the output voltage levels of charge amplifiers 10.11. This differential voltage is applied to the angular velocity signal output terminal 15 via the demodulator 13 and further via the signal processing circuit 14.

Based on the excitation voltage of the piezoelectric element 4.5, the demodulator 13
A voltage component that fluctuates in synchronization with the excitation voltage is removed from the differential voltage. As a result, the output voltage of the demodulator 13 becomes a signal corresponding to the rotational angular velocity of the tuning fork member 1, that is, an angular velocity signal. The signal processing circuit 14 calibrates the level of the angular velocity signal to 5, a voltage level within the range required by a signal reading device (not shown) connected to the output terminal 15. Also, set the output impedance to the required value.

Adder 16 is a summing amplifier mainly composed of operational amplifiers, and generates a voltage corresponding to the sum of the output voltage levels of charge amplifiers 10.11. This sum voltage is applied to an acceleration signal output terminal 22 via a demodulator 20 and a signal processing circuit 21. Based on the excitation voltage of the piezoelectric element 4.5, the demodulator 20 generates an oscillating voltage equivalent to the output voltage of the adder 16, which corresponds only to the excitation voltage, and subtracts this from the sum voltage.

As a result, the output voltage of the demodulator 20 changes in the vibration direction (y-y
), that is, an acceleration signal. The signal processing circuit 21 calibrates the level of the acceleration signal to a voltage level within a range required by a signal reading device (not shown) connected to the output terminal 22. Also, set the output impedance to the required value.

In this embodiment, the oscillator 9 is a self-excited oscillation circuit that automatically sets the vibration Fi of the tuning fork member 1 to its resonance frequency, and the amplifier (piezo driver) 19. Automatic gain adjustment circuit (AG
C) 17 and an automatic phase shift circuit (APC) 18.

When the APC 18 is powered on, it starts charging its internal CR time constant circuit. As a result, the voltage of the CR time constant circuit (the output voltage of the APC 18) gradually increases. The amplifier 19 generates an excitation voltage corresponding to this output voltage (positive peak when the voltage of the CR time constant circuit is the upper peak voltage, negative peak when the voltage of the CR time constant circuit is the base voltage), and the piezoelectric element 4.5 As a result, the piezoelectric element 4.5 gradually warps outward, and the tuning fork member 1 bends to the left in FIG.

Along with this, the output of the adder 16 gradually increases. Since the output voltage of the adder 16 has a certain phase lag with respect to the excitation voltage, the output voltage of the adder 16 reaches the positive peak after the output voltage of the APC 18 reaches the upper peak. When the output voltage of the adder 16 reaches a positive peak (the output voltage of the amplifier 19 and the output voltage of the adder 16 become equal), the APC 18 starts discharging the CR time constant circuit. This allows APC
The output voltage of 18 gradually decreases. This makes the piezoelectric element 4.5
gradually returns to the neutral position and then becomes inwardly curved, and the tuning fork member 1
Turn so that it reaches the right side in Figure 1. Accordingly, the output of the adder 16 gradually decreases and changes to negative polarity.

When the output voltage of the adder 16 reaches the lower peak (the output voltage of the adder 16 becomes equal to the output voltage of the amplifier 19), the APC 18 starts charging the CR time constant circuit.

In this way, the excitation voltage of the amplifier 19 vibrates in a sine wave shape, and the tuning fork member 1 vibrates from side to side (Fl) accordingly, but since the bending of the tuning fork member 1 is used as a feedbank to swing the excitation voltage, the excitation voltage The frequency of the voltage is automatically adjusted to the tuning fork member 1.
is determined by the frequency at which it is most likely to vibrate, that is, the resonance frequency.

The AGC 17 compares the output level (time series average value) of the adder 16 with a reference value, and when the former is lower than the latter, changes the gain of the amplifier 19 to a higher value, and when the opposite occurs, changes the gain to a lower value. As a result, the gain of the amplifier 19 becomes equal to the gain of the adder 16.
The output level of the tuning fork member 1 (the voltage level corresponding to the vibration of the piezoelectric element 2.3) is automatically adjusted to the reference value.
The amplitude of is the reference value.

The embodiment described above is an angular velocity detector that simultaneously obtains both an angular velocity signal and an acceleration signal, and is also used as a y-direction acceleration detector. A representative signal is obtained. Such a signal can be obtained by making the tuning fork member 1 into a rectangular prism shape or a quadrangular prism shape, and further by vibrating the tuning fork member 1 in a diagonal direction to generate symmetrical vibrations in the tuning fork member 1.

In the above embodiment, the tuning fork member 1 has a quadrangular prism shape, but it can also have other shapes. For example, it is made into a triangular prism whose horizontal cross section is an isosceles triangle, and a piezoelectric element for stress detection having substantially the same shape and characteristics is attached to the isosceles part, and one piezoelectric element is placed opposite the isosceles. The piezoelectric element may be attached to the bottom portion to vibrate. Alternatively, the tuning fork member 1 shown in FIG. 1 is cut in the vertical direction parallel to the It is also possible to form a pentagonal prism, omit the piezoelectric element 4.5, and connect one piezoelectric element to the newly generated side surface to excite and energize it. Furthermore, the tuning fork member 1 is made of a prism such as a pentagonal prism, a hexagonal prism, etc., and the piezoelectric element for excitation is aligned with the central axis (z - z
) and one edge so as to excite vibrations in the direction along the plane, and a piezoelectric element for stress detection may be attached at a symmetrical position with respect to the second plane. Alternatively, the tuning fork member 1 is made into a cylinder, and a piezoelectric element for excitation is joined to a part of the side circumferential surface toward the central axis, and a stress detection element is placed at a symmetrical position with respect to a plane containing the center of this piezoelectric element and the central axis of the cylinder. A piezoelectric element may be attached.

Further, the piezoelectric element for excitation does not necessarily need to be mounted on the side surface or the side peripheral surface. For example, similar to the conventional example shown in FIG. 3, the tuning fork member 1 may be supported by a piezoelectric element, and this piezoelectric element may be excited and energized as in the conventional example.

〔Effect of the invention〕

As described above, the angular velocity detector or acceleration detector of the present invention includes at least one tuning fork member (1), at least one vibrating member (two vibrating members 4 and 5 in the embodiment), and at least two Since the stress detection members (2, 3) can constitute the mechanical part,
The number of elements is very small, and the third problem of the prior art is automatically and significantly improved. In addition to the small number of elements, it is relatively easy to incorporate the vibration members (4, 5) and stress detection members (2, 3) into one tuning fork member (1) in the above-mentioned positional relationship. , the conventional problem of point 1 is also significantly improved.

Furthermore, since only one tuning fork member (1) is used, the resonant frequency can be adjusted simply by cutting its vibrating free end, making it easy to adjust the resonant frequency. , 3) are at symmetrical positions, the difference in detection sensitivity is small. In other words, the second problem of the prior art is also improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the appearance of the main parts of a mechanism according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the electric circuit section of this embodiment. FIG. 3 is a perspective view showing the appearance of a mechanical section of a conventional vibrating gyroscope. 1° tuning fork member (tuning fork member) 2.3 piezoelectric element (first and second stress detection member) 4.
5 piezoelectric element (excitation member) 6 vibration absorption member 7 sensor base 8: sensor casing 9 parts oscillator 10
．． 11 Charge amplifier 12 Differential amplifier 13.20
Demodulator 14.21 Signal processing circuit 15 Angular velocity signal output terminal
16: Adder 17 Automatic gain adjustment circuit I8 Automatic phase shift adjustment circuit 19 Amplifier Fig. 1 Complete 3

Claims (1)

[Scope of Claims] (1) a tuning fork member; an excitation member that excites vibrations in the tuning fork member that vibrates the central axis of the tuning fork member; An angular velocity detector comprising first and second stress detection members mounted at symmetrical positions with respect to a plane extending in the direction of vibration. (2) The excitation member is comprised of first and second vibrators mounted at symmetrical positions with respect to the plane of the tuning fork member that includes its central axis. angular velocity detector. (3) The excitation member and the stress detection member are each piezoelectric elements, and include an oscillation circuit that applies a phase-shifted voltage of the stress detection voltage generated by the stress detection piezoelectric element to the excitation piezoelectric element. The angular velocity detector according to item (1) or item (2). (4) a tuning fork member, an excitation member that excites vibrations in the tuning fork member that vibrates the central axis of the tuning fork member, and a surface that is joined to the tuning fork member and that includes the central axis of the tuning fork member and extends in the direction of the vibration. An acceleration detector comprising first and second stress detection members mounted at symmetrical positions with respect to the acceleration sensor. (5) The excitation member is comprised of first and second vibrators mounted at symmetrical positions with respect to the plane including the central axis of the tuning fork member, as described in claim (4) above. acceleration detector. (6) The excitation member and the stress detection member are each piezoelectric elements, and include an oscillation circuit that applies a phase-shifted voltage of the stress detection voltage generated by the stress detection piezoelectric element to the excitation piezoelectric element. The acceleration detector according to item (4) or item (5).