JP2571893B2 - Vibrating gyro - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration gyro for detecting an angular velocity used for, for example, a posture control system and a navigation system mounted on an automobile or the like, and a camera shake correction of a video camera.

[0002]

2. Description of the Related Art As a conventional vibration gyro, for example, the one shown in FIG. 3 is known. In this vibrating gyroscope, a first piezoelectric element 2 is attached to one side surface 1a of a vibrating body 1 having a rectangular cross section, and a second piezoelectric element 3 is attached to another side surface 1b adjacent to the side surface 1a. And vibrator 4
Is composed. The piezoelectric elements 2 and 3 are connected to the driving device 5 via respective impedance elements Z ₁ and Z _2.
Is connected to the further to the drive device 5, the capacitor 6 is connected via the other impedance elements Z _3, to these piezo and the capacitor 6, respectively alternating voltage simultaneously drive 5 Is applied.

On the other hand, connection points 7 and 8 between the impedance elements Z ₁ and Z ₂ and the piezoelectric elements 2 and 3 are connected to the input terminal of an adder 9, and the output terminal of the adder 9 is connected to the impedance element. Z ₃ and a connection point 10 of the capacitive element 6 are connected to the input terminal of the differential amplifier 11, and the differential output is fed back to the driving device 5. The connection points 7 and 8 are also connected to the input terminal of the differential amplifier 12, and the output of the differential amplifier 12 is connected to a resistor 13a and a capacitor 13b.
An angular velocity detection signal is obtained based on a detection signal supplied to a synchronous detector 14 (here, an FET) via a low-pass filter 13 and output to an output terminal 15 thereof.

In the vibrating gyroscope shown in FIG. 3, an AC voltage is applied to the piezoelectric elements 2 and 3 from a driving device 5 to cause the vibrator 4 to self-excitedly vibrate in the X-axis direction of an orthogonal three-dimensional coordinate system. it can. That is, when an AC voltage is applied to the piezoelectric elements 2 and 3, the output obtained from the connection points 7 and 8 is equal to the supply voltage from the drive device 5 and the piezoelectric elements 2 and 3 due to the distortion of the piezoelectric elements 2 and 3. , 3 are output as a composite output. Therefore, if the sum of the two combined outputs is obtained by the adder 9 and the difference between the output and the output corresponding to the supply voltage from the connection point 10 is obtained by the differential amplifier 11, the sum is obtained based on the vibration in the X-axis direction. Only the voltage generated from the piezoelectric elements 2 and 3 is extracted, and the output of the differential amplifier 11 is fed back to the driving device 5, whereby the vibrator 4 self-oscillates.

When the vibrator 4 is rotated around the Z axis while the vibrator 4 is self-excited, the vibrator 4
Vibrates in the Y-axis direction due to Coriolis force proportional to the angular velocity, and a difference occurs in the output from the connection points 7 and 8. Therefore, if the outputs of the connection points 7 and 8 are differentially amplified by the differential amplifier 12, the voltage accompanying the generation of the Coriolis force can be separated and detected. After supplying and removing harmonic components contained as a waveform distortion in the differential output, if the synchronous detector 14 detects in synchronization with the excitation cycle of the vibrator 4, the Coriolis force is detected as a voltage. And an angular velocity detection signal can be obtained based on this.

[0006]

However, in the above-described conventional vibrating gyroscope, a low-pass filter 13 is provided.
Is supplied directly to the synchronous detector 14, so that the voltage of the output terminal 15 (that is, the output terminal 16 of the low-pass filter 13) changes the conduction state (ground state) of the synchronous detector 14 composed of the FET. When it becomes non-conductive from
The voltage is charged according to a time constant determined by the capacitor 13a and the capacitor 13b. For this reason, a sufficient voltage cannot be output and a delay occurs. Further, the low-pass filter 13 functions only when the synchronous detector 14 is in a non-conducting state, so that the function is insufficient.

From the above, as shown in FIG. 4A, the voltage waveform at the output terminal 15 should be such that the detected voltage waveform shown by the broken line 17 should appear with the generation of the Coriolis force, but the solid line 18
As shown by, even when the synchronous detector 14 becomes non-conductive, the synchronous detector 14 does not rise immediately, resulting in loss of output. Also,
As shown in FIG. 4b, the voltage generated due to the unnecessary leakage vibration having a phase difference of about 90 ° with respect to the detected voltage is originally symmetrical above and below the base line 20 as shown by a broken line 19, and is reduced to zero. Becomes an asymmetric waveform as shown by the solid line 21, and this voltage changes due to a change in the ambient temperature, causing a drift.

As described above, in the above-described conventional vibrating gyroscope, the low-pass filter function is inadequate, and the loss of the detection output and the occurrence of drift occur. Therefore, the angular velocity can always be controlled with high sensitivity and high accuracy. There was a problem that it could not be detected.

The present invention has been made in view of such a conventional problem, and has as its object to provide a vibrating gyroscope appropriately configured to always detect angular velocity with high sensitivity and high accuracy. .

[0010]

In order to achieve the above object, according to the present invention, a vibrator having at least two piezoelectric elements is self-excitedly vibrated on a side surface of a vibrating body having a polygonal cross section. The outputs of the two piezoelectric elements are differentially amplified by a differential amplifier, and the differential output is detected in synchronization with the self-excited vibration by a synchronous detector via a low-pass filter, and the angular velocity acting on the vibrator is detected. In the vibration gyro to be detected, a resistor is connected between the low-pass filter and the synchronous detector.

[0011]

When the resistor is connected between the low-pass filter and the synchronous detector, the low-pass filter always outputs the result of the filter operation. Therefore, the synchronous detection output immediately rises regardless of the time constant of the low-pass filter, and becomes an output waveform that is surely synchronously detected.Thus, the loss of the detection output can be effectively prevented, and the drift can be reduced. , The angular velocity can always be detected with high sensitivity and high accuracy.

[0012]

FIG. 1 shows an embodiment of the present invention.
The same reference numerals as those shown in FIG. 3 indicate the same elements. In this embodiment, a first piezoelectric element 2 is adhered to one side surface 1a of the vibrating body 1 having a rectangular cross section, and a second piezoelectric element 3 is adhered to another side surface 1b adjacent to the side surface 1a. Thus, the vibrator 4 is formed. The piezoelectric elements 2 and 3 are connected to a driving device 5 via respective impedance elements Z ₁ and Z ₂ , and further connected to the driving device 5 via a capacitance element 6 via another impedance element Z ₃ . An AC voltage is simultaneously applied to these piezoelectric elements 2 and 3 and the capacitive element 6 from the driving device 5.

On the other hand, connection points 7 and 8 between the impedance elements Z ₁ and Z ₂ and the piezoelectric elements 2 and 3 are connected to the input terminal of the adder 9, and the output terminal of the adder 9 is connected to the impedance element. Z ₃ and the connection point 10 of the capacitive element 6 are connected to the input terminal of the differential amplifier 11, and the differential output is fed back to the driving device 5. Connection points 7 and 8 are differential amplifiers.
12 is connected to the input terminal of the differential amplifier 12, and the output of the differential amplifier 12 is connected to a low-pass filter comprising a resistor 13a and a capacitor 13b.
13 and a synchronous detector 14 (here, FE)
T), and an angular velocity detection signal is obtained based on the detection signal output to the output terminal 15 thereof.

In the vibrating gyroscope shown in FIG. 1, when an AC voltage is applied to the piezoelectric elements 2 and 3 from the driving device 5, the vibrator 4 self-oscillates in the X-axis direction of the orthogonal three-dimensional coordinate system. That is, when an AC voltage is applied to the piezoelectric elements 2 and 3, the output obtained from the connection points 7 and 8 is equal to the supply voltage from the drive device 5 and the piezoelectric elements 2 and 3 due to the distortion of the piezoelectric elements 2 and 3. , 3 are output as a composite output. Therefore, the sum of the two combined outputs is obtained by the adder 9,
If the difference between the output and the output corresponding to the supply voltage from the connection point 10 is obtained by the differential amplifier 11, only the voltage generated from the piezoelectric elements 2 and 3 based on the vibration in the X-axis direction is extracted,
By returning the output of the differential amplifier 11 to the driving device 5, the vibrator 4 self-oscillates.

When the vibrator 4 is rotated around the Z axis while the vibrator 4 is self-excited, the vibrator 4
Vibrates in the Y-axis direction due to Coriolis force proportional to the angular velocity, and a difference occurs in the output from the connection points 7 and 8. Therefore, if the outputs of the connection points 7 and 8 are differentially amplified by the differential amplifier 12, the voltage accompanying the generation of the Coriolis force can be separated and detected. Then, after removing harmonic components included as a waveform distortion in the differential output, the signal is supplied to the synchronous detector 14 via the resistor 22, and the excitation period of the vibrator 4 in the synchronous detector 14 is reduced. , The Coriolis force can be detected as a voltage, and an angular velocity detection signal can be obtained based on the voltage.

Here, as in the case of FIG. 3, the output terminal 15 is connected to the ground side in response to the synchronous detector 14 repeating conduction and non-conduction alternately every half cycle of the excitation period of the vibrator 4. In this embodiment, since the output terminal 16 of the low-pass filter 13 is connected to the output terminal 15 via the resistor 22, the low-pass filter 13 is intermittent with the ground side of the output terminal 15. Regardless of the repetition, the result of the filter action will always be output.

Therefore, the capacitor 13 associated with synchronous detection
Since the charging and discharging of b with respect to the ground side is eliminated, the detection voltage waveform generated at the output terminal 15 due to the generation of the Coriolis force, regardless of the time constant of the low-pass filter 13 in the non-conduction state of the synchronous detector 14, As shown by the solid line 23 in FIG. 2A, the voltage waveform rises immediately, that is, the voltage waveform is surely synchronously detected, whereby the output loss can be effectively prevented. In addition, the voltage generated due to unnecessary leakage vibration having a phase difference of about 90 ° with respect to the detected voltage also has a symmetrical waveform as shown by a solid line 24 in FIG. Drift is less likely to occur even if is changed.

[0018]

As described above, according to the present invention, the output of the low-pass filter is supplied to the synchronous detector via the resistor, so that the low-pass filter can always function, and the synchronous detection can be performed. Accordingly, charging and discharging of the output terminal of the low-pass filter can be effectively prevented. Therefore, the synchronous detection can be performed reliably, the loss of the detection output can be effectively prevented, and the drift can be reduced. Therefore, the angular velocity can always be detected with high sensitivity and high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation.

FIG. 3 is a diagram for explaining a conventional technique.

FIG. 4 is a signal waveform diagram for explaining the operation of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration body 1a, 1b Side surface 2, 3 Piezoelectric element 4 Vibrator 5 Drive device 6 Capacitor element 7, 8, 10 Connection point 9 Adder 11, 12 Differential amplifier 13 Low-pass filter 14 Synchronous detector 15 Output terminal 22 Resistor

Claims (1)

(57) [Claims] 1. A vibrator having at least two piezoelectric elements is self-oscillated on a side surface of a vibrating body having a polygonal cross section, and the outputs of the two piezoelectric elements are differentially amplified by a differential amplifier. The differential output is detected by a synchronous detector through a low-pass filter in synchronization with the self-excited vibration, and an angular velocity acting on the vibrator is detected. A vibrating gyroscope comprising a resistor connected between the detector and the detector.