JPH07229744A - Vibration detecting circuit - Google Patents

Abstract

PURPOSE:To eliminate the error of detected signal due to the fluctuation of the sensitivity in a vibration detecting circuit using a piezoelectric gyroscope. CONSTITUTION:A driving circuit 32 generates the exciting voltage VA and supplies it to a piezoelectric gyroscope 11 through resistors R21, R22. The electrode voltage VD1, VD2 of the piezoelectric gyroscope 11 is supplied to a variable amplifying part 36 of a detected signal generating part 35. A full-wave rectifying circuit 39 receiver the voltage VD3 which is the sum of the electrode voltage VD1, VD2 and generates the control voltage proportional to the amplitude of the voltage VD3. The variable amplifying part 36 generates the amplified difference signal with the amplification proportional to this control voltage. An amplified component extracting part 41 extracts the amplitude component of the difference signal, and outputs it as the detected signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration detecting circuit, and more particularly to a vibration detecting circuit using a piezoelectric gyro.

[0002]

2. Description of the Related Art In recent years, a piezoelectric vibrating gyro (hereinafter referred to as a piezoelectric gyro) that detects an angular velocity of vibration has been used for detecting vibration. FIG. 5 shows an operation explanatory diagram of the piezoelectric gyro 11. The piezoelectric gyro 11 is configured by joining piezoelectric elements 13a and 13b in which piezoelectric ceramics are sandwiched between metals to two surfaces of a square pole-shaped vibrator 12 made of metal.

The voltage of the vibrator 12 is set to a predetermined voltage by the power source E ₁₁ . Via the resistor R _51, R _52, piezoelectric elements 13a, 13b in addition to the excitation voltage, to vibrate the vibrator 12 in the Y direction.

When the vibrator 12 is rotated by the vibration of the object to be detected generated outside, Coriolis force is generated in the X direction in proportion to the angular velocity. Due to this Coriolis force, one piezoelectric element contracts and the other piezoelectric element expands. As a result, the amount of change in the voltage amplitude of the electrodes of the piezoelectric elements 13a and 13b is proportional to the Coriolis force, and the amplitude of one electrode voltage increases and the amplitude of the other electrode voltage decreases. The difference between the amplitudes of the two electrode voltages corresponds to the angular velocity. For this reason,
An amplitude component is extracted from the difference signal between the two electrode voltages, and the angular velocity detection signal is obtained.

The level of the angular velocity detection signal with respect to the reference angular velocity is the sensitivity of the piezoelectric gyro 11.

[0006]

The sensitivity of the piezoelectric gyro 11 varies with temperature and the like. However, conventionally, in the vibration detection circuit using the piezoelectric gyro 11, the difference signal between the two electrode voltages is used as it is to generate the detection signal of the angular velocity. Therefore, if the sensitivity changes due to temperature fluctuations or the like, an error occurs in the angular velocity detection signal.

The present invention has been made in view of the above points, and an object thereof is to provide a vibration detection circuit capable of eliminating an error in a detection signal due to a change in sensitivity.

[0008]

According to a first aspect of the present invention, a detection signal of a level corresponding to an angular velocity of vibration is generated based on a difference signal between electrode voltages of two excited detection electrodes of a piezoelectric gyro. In the vibration detection circuit having a detection signal generating section, the detection signal generating section is
The level of the detection signal is corrected according to the amplitude of the sum signal of the two electrode voltages.

According to a second aspect of the invention, the detection signal generator supplies a control signal generator that generates a control signal having a level corresponding to the amplitude of the sum signal of the two electrode voltages, and the two electrode voltages. A variable amplification unit that generates a difference signal by amplifying the signal of the difference between the two electrode voltages with an amplification degree according to the level of the control signal, and an amplitude component from the difference signal supplied from the variable amplification unit. And an amplitude component extraction unit that extracts a signal to generate a detection signal.

According to a third aspect of the present invention, the control signal generation section is composed of a double-wave rectification circuit that generates a control voltage.

[0011]

According to the first aspect of the present invention, the detection signal generating section corrects the level of the detection signal generated according to the amplitude of the sum signal of the two electrode voltages corresponding to the sensitivity of the piezoelectric gyro. Therefore, it is possible to prevent an error from occurring in the detection signal of the angular velocity even if the sensitivity of the piezoelectric gyro changes.

According to a second aspect of the present invention, a control signal generating section,
By providing the variable amplification section, it is possible to easily realize the configuration for correcting the level of the detection signal according to the sensitivity of the vibration gyro.

According to the third aspect of the invention, it is possible to realize the control signal generating section with a simple structure.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a vibration detecting circuit according to an embodiment of the present invention. The circuit of FIG. 1 is a circuit that detects the angular velocity of vibration using the piezoelectric gyro 11 described in FIG.
A drive circuit 32 that generates an excitation voltage for exciting the piezoelectric gyro 11 and a detection signal generation unit 35 are provided.

The detection signal generator 35 includes a variable amplifier 36,
It is composed of an amplitude component extraction unit 41 and a double-wave rectification circuit 39 as a control voltage generation unit. The variable amplifier 36 includes the differential amplifier circuit 3
7 and a voltage control amplifier circuit 38. Further, the amplitude component extraction unit 41 includes a synchronous detection circuit 42 and a low pass filter 43. The drive circuit 32 includes a differential amplifier circuit 33 and an excitation voltage generation circuit 34.

The voltage of the vibrator 12 of the piezoelectric gyro 11 is
A predetermined voltage is set by the power source E ₁₁ . Drive circuit 3
The excitation voltage V _A generated in 2 is applied to the piezoelectric elements 13a and 13b via the resistors R ₂₁ and R ₂₂ .

Electrode voltage V of each of the piezoelectric elements 13a and 13b
_D1 and V _D2 are supplied to the differential amplifier circuit 37 of the variable amplifier 36. Further, the voltage V _{D3 obtained} by summing the respective electrode voltages V _D1 and V _D2 by the resistors R ₂₄ and R ₂₅ becomes the differential amplifier circuit 33.
Is supplied to the plus input terminal and the full-wave rectification circuit 39. Further, the excitation voltage V _A is supplied to the negative input terminal of the differential amplifier circuit 33.

Next, the operation of the circuit shown in FIG. 1 will be described. The excitation voltage generation circuit 34 uses the triangular excitation voltage V _A.
To generate. The excitation voltage V _A is applied to the piezoelectric elements 13a and 13b via the resistors R ₂₁ and R ₂₂ , so that the vibrator 12 moves to Y.
Vibrates in the direction. The respective electrode voltages V _D1 and V _D2 are substantially sinusoidal voltages.

The differential amplifier circuit 33 obtains a voltage obtained by subtracting the excitation voltage V _A from the sum voltage V _{D3 of the} two electrode voltages V _D1 and V _D2 , and feeds it back to the excitation voltage generation circuit 34.
By this feedback, an oscillation circuit that generates the excitation voltage V _A is configured. The feedback voltage of the differential amplifier circuit 33 controls the phase of the excitation voltage V _A so that the oscillator 12 always oscillates at the resonance frequency of the oscillator 12.

As described above, when the oscillator 12 is excited, the oscillator 12 is vibrated by the vibration of the detection target generated externally.
When is rotated, Coriolis force is generated in the X direction in proportion to the angular velocity. Due to this Coriolis force, one piezoelectric element contracts and the other piezoelectric element expands. As a result, the amplitude change amount of the electrode voltages V _D1 and V _D2 of the respective piezoelectric elements 13a and 13b is proportional to the Coriolis force, and the amplitude of one electrode voltage increases and the amplitude of the other electrode voltage decreases.

The difference in amplitude between the two electrode voltages V _D1 and V _D2 corresponds to the angular velocity. Therefore, the electrode voltages V _D1 and V _D2
The amplitude component is extracted from the signal of the difference between the two to obtain the angular velocity detection signal.

The differential amplifier circuit 37 of the variable amplifier section 36 has two
A signal obtained by amplifying the signal of the difference between the two electrode voltages V _D1 and V _D2 with a constant amplification degree is generated. The voltage control amplifier circuit 38 converts the signal supplied from the differential amplifier circuit 37 into a double-wave rectifier circuit 39.
The differential signal is generated by amplification with an amplification degree proportional to the level of the control voltage supplied from.

The amplitude component extraction unit 41 extracts the amplitude component of the differential signal supplied from the variable amplification unit 36 and outputs it as a detection signal of angular velocity. The synchronous detection circuit 42 of the amplitude component extraction unit 41 receives the excitation voltage V _A from the excitation voltage generation circuit 34.
The differential signal supplied from the variable amplifier 36 is synchronously detected. The low-pass filter 43 takes out the DC component of the synchronously detected signal and outputs it as an angular velocity detection signal. The level of this detection signal corresponds to the angular velocity.

The two-wave rectification circuit 39 has two electrode voltages V
_A substantially sinusoidal voltage V _{D3, which} is the sum of _D1 and V _D2 , is supplied. The double-wave rectifier circuit 39 double-wave rectifies the voltage V _D3 and outputs a DC component voltage as a control voltage. That is,
A control voltage proportional to the amplitude of the substantially sinusoidal voltage V _D3 is generated.

Next, the sensitivity of the piezoelectric gyro 11 changes.
At this time, the correction of the detection signal will be described. 2 is piezoelectric
An equivalent circuit of the gyro 11 is shown. Piezoelectric element 13a side, etc.
The value circuit is a resistor R_S1, Coil L_S1, Capacitor C_S1Directly
Column circuit and capacitor C_S11It becomes a parallel circuit of. Similarly,
The equivalent circuit on the piezoelectric element 13b side has a resistance R_S2,coil
L _S2, Capacitor C_S2Series circuit and capacitor C_S12of
It becomes a parallel circuit.

FIG. 3 shows an example of the temperature characteristic of the sensitivity of the piezoelectric gyro 11. Further, FIG. 4 shows the relationship between the amplitude of the voltage V _D3 , which is the sum of the electrode voltages V _D1 and V _D2 , and the temperature.

Piezoelectric gyro 1 shown in the equivalent circuit of FIG.
The impedance in the excitation state of 1 changes with temperature. The sensitivity of the piezoelectric gyro 11 becomes better as the impedance becomes smaller. As the impedance of the piezoelectric gyro 11 changes with temperature, the sensitivity changes with temperature, as shown in FIG. 3, for example. A maximum sensitivity at a reference temperature T _m, at the reference temperature T a temperature lower than _m and higher temperatures has a characteristic that the sensitivity is lowered.

On the other hand, the better the sensitivity of the piezoelectric gyro 11 is,
Since the impedance of the piezoelectric gyro 11 becomes small,
Resistance R_{twenty one}, R_{twenty two}And electrode voltage divided by the piezoelectric gyro 11
Pressure V _D1, V_D2Becomes smaller. Therefore, the electrode voltage V
_D1, V_D2Voltage V_D3Also becomes smaller. others
Therefore, for the characteristics of FIG. 3, as shown in FIG._D3
Is the reference temperature T_mAt the minimum, the reference temperature T_m
At lower and higher temperatures, it has an increasing property.
It

The characteristic of the change of the sensitivity of the piezoelectric gyro 11 with respect to temperature, that is, the characteristic of the change of the level of the detection signal with respect to the temperature, and the characteristic of the change of the amplitude of the voltage V _D3 with respect to the temperature are in inverse proportion to each other. . For example, if the sensitivity becomes 1 / K times the sensitivity at the reference temperature T _m due to a temperature change, the amplitude of the voltage V _D3 becomes K times the amplitude at the reference temperature T _m .

As described above, the control voltage generated by the double-wave rectification circuit 39 is proportional to the amplitude of the voltage V _D3 . The voltage control amplifier circuit 38 is set to an amplification degree proportional to this control voltage. Further, the amplification degree of the differential amplifier circuit 37 is constant. Therefore, the amplification degree of the variable amplification section 36 changes in proportion to the amplitude of the voltage V _D3 .

Therefore, when the sensitivity of the piezoelectric gyro 11 changes, the amplification degree of the variable amplification section 36 changes in inverse proportion to the sensitivity, and the level of the detection signal is corrected. Therefore, the level of the detection signal with respect to a constant angular velocity becomes a constant value without being affected by the sensitivity of the vibration gyro 11.

For example, the sensitivity of the piezoelectric gyro 11 is 1 / K
When doubled, the amplitude of the voltage V _D3 and the control voltage double K times,
The amplification degree of the variable amplification section 36 also becomes K times. As a result, for a constant angular velocity, the differential signal output by the variable amplifier 36 becomes constant, and the level of the detection signal also becomes constant.

As described above, in this embodiment, the piezoelectric gyro
The voltage V corresponding to the sensitivity of 11 _D3Proportional to the amplitude of
The gain of the variable amplifier 36 of the detection signal generator 35.
Then, the level of the generated detection signal is corrected. others
Therefore, even if the sensitivity of the piezoelectric gyro 11 changes with temperature,
The error can be prevented from occurring in the signal.

Further, in the present embodiment, it suffices to provide the both-wave rectification circuit 39 and the variable amplification section 36 including the voltage control amplification circuit 38, which has a simple structure, and facilitates the circuit which can correct the level of the detection signal. Can be realized.

Even if the sensitivity changes due to factors other than temperature, such as variations in manufacturing, the detection signal generator 35 can similarly correct the level of the detection signal.

Further, instead of the variable amplification section 36, a differential amplification circuit having a constant amplification degree may be provided, and the amplification degree of the amplification section provided at the subsequent stage of the amplitude component extraction section 41 may be varied by a control voltage. it can.

[0037]

As described above, according to the invention of claim 1,
The detection signal generation unit corrects the level of the detection signal generated according to the amplitude of the sum signal of the two electrode voltages corresponding to the sensitivity of the piezoelectric gyro. It is possible to prevent an error from occurring in the detection signal.

According to the second aspect of the invention, by providing the control signal generating section and the variable amplifying section, it is possible to easily realize the configuration for correcting the level of the detection signal according to the sensitivity of the vibration gyro. it can.

According to the invention of claim 3, with a simple structure,
It is possible to realize the control signal generation unit.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a vibration detection circuit according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit of a piezoelectric gyro.

FIG. 3 is a diagram showing an example of temperature characteristics of sensitivity of a piezoelectric gyro.

FIG. 4 is a diagram showing a relationship between voltage amplitude and temperature obtained by summing two electrode voltages.

FIG. 5 is an operation explanatory diagram of the piezoelectric gyro.

[Explanation of symbols]

 11 Piezoelectric Vibratory Gyro 12 Vibrator 13a, 13b Piezoelectric Element 32 Drive Circuit 33 Differential Amplifier Circuit 35 Detection Signal Generation Section 36 Variable Amplifier Section 37 Differential Amplifier Circuit 38 Voltage Control Amplifier Circuit 41 Amplitude Component Extraction Section 42 Synchronous Detection Circuit 43 Low Filter

Claims (3)

[Claims] 1. A vibration detection circuit having a detection signal generation unit for generating a detection signal at a level corresponding to an angular velocity of vibration based on a difference signal between electrode voltages of two detection electrodes of an excited piezoelectric gyro. The detection signal generation unit corrects the level of the detection signal according to the amplitude of the sum signal of the two electrode voltages of the piezoelectric gyro. 2. The control signal generation unit for generating a control signal having a level corresponding to the amplitude of the sum signal of the two electrode voltages, the detection signal generation unit being supplied with the two electrode voltages, A variable amplifier that generates a differential signal by amplifying a signal of the difference between two electrode voltages with an amplification degree according to the level of the control signal, and an amplitude component is extracted from the differential signal supplied from the variable amplifier and detected. The vibration detection circuit according to claim 1, further comprising an amplitude component extraction unit that generates a signal. 3. The vibration detection circuit according to claim 2, wherein the control signal generation unit includes a double-wave rectification circuit that generates a control voltage.