JPH06317425A - Detection circuit for vibrational gyro - Google Patents

Abstract

PURPOSE:To compensate for offsets so as to stably obtain accurate vibrational gyro outputs by synthesizing an amplitude difference detecting output with a synchronous detecting output due to the variation of a phase difference. CONSTITUTION:A vibrator is constituted so that its resonance frequency in the exciting direction (X-axis direction) and another resonance frequency in the detecting direction (Y-axis direction) can be separated from each other and, at the same time, a detecting system incorporating a differential amplifier 8 and synchronous detector 9, amplitude difference detector 10, and synthesizing circuit 11 are added to the vibrator. By supplying the outputs of piezoelectric elements 2a and 2b to the detector 10, the amplitude difference between the outputs is detected and the detected amplitude difference is synthesized with the output of the detector 9 by means of the circuit 11. Then an angular velocity detecting signal is obtained by smoothing the synthesized output of the circuit 11 by means of a smoothing circuit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration gyro detection circuit for detecting an angular velocity, and more particularly to a vibration gyro detection circuit capable of stably obtaining an accurate vibration gyro output.

[0002]

2. Description of the Related Art As a conventional vibrating gyroscope, for example, one shown in FIG. 9 is known. In this vibrating gyroscope, one side surface 1a of the vibrating body 1 having a square prism shape is formed.
The first piezoelectric element 2a and the second piezoelectric element 2b are attached to the other side surface 1b adjacent to the side surface 1a to form the vibrator 3.

In a vibrating gyroscope using such a vibrator 3, the piezoelectric elements 2a and 2b are connected to the output side of the driving device 4 via the impedance elements Z ₁ and Z ₂ , respectively, and the driving device 4 The output side is also connected to the capacitive element C via another impedance element Z ₃ so that an AC voltage is simultaneously applied from the drive device 4 to the piezoelectric elements 2a, 2b and the capacitive element C.

Further, here, the impedance element Z ₁ ,
Z ₂ and the piezoelectric elements 2a and 2b, respectively, at connection points 5a,
5b is connected to the input terminal of the adder 6, and the output terminal of the adder 6 and the connection point 5c of the impedance element Z ₃ and the capacitive element C are connected to the input terminal of the differential amplifier 7, respectively. The differential output is fed back to the driving device 4, the connection points 5a and 5b are also connected to the input terminals of the other differential amplifiers 8, the differential output is detected by the synchronous detector 9, and then smoothed (not shown). It is smoothed by a circuit to obtain an angular velocity detection signal. The output of the drive unit 4 is also supplied to the synchronous detector 9.

In such a vibrating gyro, the drive unit 4
By applying an alternating voltage to the piezoelectric elements 2a, 2b from the piezoelectric element 2a, 2b, the vibrator 3 can be caused to self-excitate in the X-axis direction of the orthogonal three-dimensional coordinate system, and the connecting points 5a, 5
The output obtained from b is the supply voltage from the drive device 4,
Along with the distortion of each piezoelectric element 2a, 2b, it becomes a combined output with the voltage output from each piezoelectric element 2a, 2b.

Therefore, if the sum of the two combined outputs is obtained by the adder 6 and the difference between the output and the output corresponding to the supply voltage from the connection point 5c is obtained by the differential amplifier 7, vibration in the X-axis direction is obtained. Based on the above, only the voltage generated from the piezoelectric elements 2a and 2b can be extracted, and the differential output thereof is fed back to the drive device 4, whereby the vibrator 3 can be stably self-excited.

Further, when the vibrator 3 is rotated about the Z-axis while the vibrator 3 is self-excited as described above,
The oscillator 3 has Y due to Coriolis force proportional to its angular velocity.
It vibrates in the axial direction and a difference occurs in the outputs from the connection points 5a and 5b. Therefore, if the difference is obtained by the differential amplifier 8, the voltage generated due to the Coriolis force generation can be separated and detected. After the differential output is detected by the synchronous detector 9, it is smoothed (not shown). An angular velocity detection signal can be obtained by smoothing with a circuit.

[0008]

However, in the above-mentioned conventional vibrating gyro, it is difficult to make the exciting direction of the vibrator 3 perfectly coincide with the X direction, so that the vibrating especially occurs with a change in ambient temperature. The state changes, which causes an output to be generated in the synchronous detector 9 and an offset voltage to be generated, even though the vibrator 3 is not rotated about the Z axis.

For example, in the vibrator 3 in which the resonance frequencies f _x and f _y in the excitation direction and the detection direction are close to or coincide with each other, even if the excitation direction is set to the X-axis direction by the initial setting,
When the ambient temperature changes due to the non-uniformity of the internal characteristics of the vibrating body 1 forming the vibrator 3 or the characteristic difference between the piezoelectric elements 2a and 2b, for example, as shown in FIG. It makes an elliptical motion whose major axis is in a direction substantially parallel to. Therefore, the output of the piezoelectric elements 2a and 2b is shown in FIG.
1 causes a phase difference Δφ, which causes an offset voltage, which makes it impossible to stably detect an accurate angular velocity detection signal.

The object of the present invention was made in view of the above-mentioned conventional problems, and is appropriately configured so that an accurate vibrating gyro output can be stably obtained without being affected by changes in ambient temperature. To provide a detection circuit for the vibration gyro.

[0011]

In order to achieve the above object, in the present invention, the resonance frequency in the excitation direction and the resonance frequency in the detection direction of a columnar vibrator having two piezoelectric elements for detecting an angular velocity are separated from each other. And a synchronous detection means for synchronously detecting the differential outputs of the two piezoelectric elements, and an amplitude difference detection means for detecting an amplitude difference between the two piezoelectric elements,
A synthesizing unit for synthesizing the outputs of the synchronous detecting unit and the amplitude difference detecting unit to cancel the offset voltage is provided, and the angular velocity is detected based on the output of the synthesizing unit.

[0012]

According to various experiments conducted by the present inventor, as described above, the resonance frequency (f _x ) in the excitation direction of the columnar oscillator,
When the resonance frequency ( _fy ) in the detection direction is separated, when the excitation direction of the vibrator is set to the X-axis direction, its excitation posture changes as the ambient temperature changes, for example, as shown in FIG. It was confirmed that the movement changed to an elliptic movement having a major axis in the axial direction having an inclination from the X axis to the Y axis direction. In this case,
In the vibration gyro shown in Fig. 2, the piezoelectric elements 2a and 2b
As shown in FIG. 2, a phase difference Δφ is generated in the output of each of the output signals, and ΔV is also generated in their amplitudes.

Further, the various samples were measured the temperature change in the phase difference Δφ and amplitude difference [Delta] V, the f _x <f _y, is as shown in FIG. 3, also f _x
When> f _y , the results are as shown in FIG. 4, and it was found that there is mutual relevance in any case.

From the above, if the detection output of the amplitude difference is combined with the synchronous detection output due to the change of the phase difference, the offset can be canceled out, and thereby an accurate vibration gyro output can be stably obtained. Will be possible.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 shows the structure of the main part of the first embodiment of the present invention. In this embodiment, in the vibration gyro shown in FIG. 9, the vibrator 3 is configured such that the resonance frequency in the excitation direction (X axis direction) and the resonance frequency in the detection direction (Y axis direction) are separated from each other, and An amplitude difference detector 10 and a synthesis circuit 11 are added to a detection system having a differential amplifier 8 and a synchronous detector 9, and the outputs of the piezoelectric elements 2a and 2b are supplied to the amplitude difference detector 10 to detect the amplitude difference between them. Detect and
The amplitude difference is combined with the output of the synchronous detector 9 in the combining circuit 11, and the combined output is smoothed by the smoothing circuit 12 to obtain the angular velocity detection signal.

The amplitude difference detector 10 is, as shown in FIG.
The outputs of the piezoelectric elements 2a and 2b are respectively converted to rectifier circuits 13a and 13a.
The amplitude difference is detected by rectifying by 13b and supplying the outputs of these rectifying circuits 13a and 13b to the differential amplifier 14. The synchronous detector 9 is composed of an FET, an analog switch, a sample and hold circuit, and the like.

According to this embodiment, the resonance frequency in the excitation direction of the vibrator 3 and the resonance frequency in the detection direction are separated from each other, and the amplitude difference detector 10 detects the amplitude difference between the outputs of the piezoelectric elements 2a and 2b. Then, since the amplitude difference is combined with the output of the synchronous detector 9 in the combining circuit 11, the offset voltage generated due to the temperature change in the combining circuit 11 can be effectively canceled. Therefore, the accurate angular velocity detection signal can always be stably obtained.

FIG. 7 shows the construction of the main part of the second embodiment of the present invention. In this embodiment, instead of smoothing the output of the synthesis circuit 11 by the smoothing circuit 12 in the first embodiment, the outputs of the synchronous detector 9 and the amplitude difference detector 10 are smoothed by the smoothing circuits 15a and 15b, respectively. These outputs are combined by the combining circuit 11, and other configurations are similar to those of the first embodiment.

FIG. 8 shows the construction of the main part of the third embodiment of the present invention. In this embodiment, the amplitude difference between the piezoelectric elements 2a and 2b is detected from the output of the differential amplifier 8 in the first embodiment. Therefore, in this embodiment, the output of the differential amplifier 8 is also supplied to the synchronous detector 16, where the output of the differential amplifier 8 is synchronously detected with a phase difference of 90 ° from that of the synchronous detector 9. Piezoelectric elements 2a, 2b
The amplitude difference of is detected. The amplitude difference between the piezoelectric elements 2a and 2b detected by the synchronous detector 16 is combined with the output of the synchronous detector 9 in the combining circuit 11 as in the first embodiment, and the combined output is smoothed by the smoothing circuit 12. Then, the angular velocity detection signal is obtained.

In FIG. 8, as in the case of FIG. 7, instead of smoothing the output of the synthesizing circuit 11 by the smoothing circuit 12, the outputs of the synchronous detectors 9 and 16 are smoothed by the smoothing circuits, respectively. It is also possible to configure so that the output of the above is combined by the combining circuit 11.

[0021]

As described above, according to the present invention, the offset voltage generated due to the change in ambient temperature can be effectively canceled, so that an accurate angular velocity detection signal can always be obtained stably. it can.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation of the present invention.

FIG. 2 is a diagram for explaining the output of the piezoelectric element according to the present invention.

FIG. 3 is a diagram for explaining the relationship between the output amplitude difference and the phase difference.

FIG. 4 is a diagram for explaining the relationship between the amplitude difference and the phase difference.

FIG. 5 is a diagram showing a configuration of a main part of the first embodiment of the present invention.

6 is a diagram showing a specific circuit configuration of the amplitude difference detector shown in FIG.

FIG. 7 is a diagram showing a configuration of a main part of a second embodiment of the present invention.

FIG. 8 is also a diagram showing the configuration of the main part of the third embodiment.

FIG. 9 is a diagram showing a configuration of a conventional vibrating gyro.

FIG. 10 is a diagram for explaining the operation of the vibrator shown in FIG.

11 is a diagram for explaining the output of the piezoelectric element shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibrating body 2a, 2b Piezoelectric element 3 Oscillator 8 Differential amplifier 9 Synchronous detector 10 Amplitude difference detector 11 Composite circuit 12 Smoothing circuit 13a, 13b Rectifier circuit 14 Differential amplifier 15a, 15b Smoothing circuit 16 Synchronous detector

Claims (1)

[Claims] 1. A resonance frequency in the excitation direction and a resonance frequency in the detection direction of a columnar vibrator having two piezoelectric elements for detecting an angular velocity are separated from each other, and the differential outputs of the two piezoelectric elements are synchronously detected. The synchronous detection means, the amplitude difference detection means for detecting the amplitude difference between the two piezoelectric elements, and the combining means for combining the outputs of the synchronous detection means and the amplitude difference detection means to cancel the offset voltage. A detection circuit for a vibration gyro, which is configured to detect an angular velocity based on an output of a synthesizing means.