JPH11142161A - Vibrational gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vibrational gyro which can eliminates the drift components by using a simple circuit, without individually correcting the temp. characteristics of vibrators. SOLUTION: The vibrational gyro comprises a vibrator 22 composed of a vibrator body 24 and piezoelectric elements 26a-26c output signal of which are inputted to an oscillator circuit 38 composed of an inverted amplifier circuit 40 and AGC circuit 42 through buffer circuits 36a, 36b to obtain a driving signal to be inputted to the piezoelectric element 26c. Output signal of the buffer circuits 36a, 36b are inputted to a detector circuit 44 composed of a differential circuit 46, synchronous detector circuit 48, smoother circuit 52 and d-c amplifier 54. The synchronous detector circuit 48 detects the output signal of the differential circuit 46 synchronously with a reference signal from a phase shifter circuit 50 which comprises a thermosensitive element to adjust the phase of the output signal of the inverted amplifier circuit 40 according to the temp. to provide a reference signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrating gyroscope and, more particularly, to a vibrating gyroscope for detecting a camera shake, detecting a position in a car navigation system, and detecting an angular velocity used for controlling a posture of a vehicle.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing an example of a conventional vibrating gyroscope. The vibrating gyroscope 1 includes a vibrator 2. The vibrator 2 includes, for example, a regular triangular prism-shaped vibrator 3 and piezoelectric elements 4 a, 4 b, formed on three side surfaces of the vibrator 3.
4c. The piezoelectric elements 4a and 4b are connected to a comparator circuit 6 via buffer circuits 5a and 5b. The comparator circuit 6 is connected to a phase correction circuit 7, and an output signal of the phase correction circuit 7 is input to the piezoelectric element 4c as a drive signal.

[0005] The buffer circuits 5a and 5b are connected to a differential circuit 8 constituting a detection circuit. The main signal of the differential circuit 8 is detected by the synchronous detection circuit 9 in synchronization with the signal of the comparator circuit 6. The output signal of the synchronous detection circuit 9 is smoothed by the smoothing circuit 10 and further amplified by the DC amplifier circuit 11.

The output signals of the piezoelectric elements 4a and 4b are impedance-converted by buffer circuits 5a and 5b, the output signals of the buffer circuits 5a and 5b are combined, and the waveform is shaped by a comparator circuit 6. And the comparator circuit 6
Is output to the piezoelectric element 4c as a drive signal. This drive signal causes the piezoelectric element 4c to expand and contract, whereby the vibrating body 3 bends and vibrates in a direction orthogonal to the surface on which the piezoelectric element 3c is formed.

At the time of non-rotation, the piezoelectric elements 4a, 4b
Have the same bending state, and their output signals are the same. Therefore, no signal is output from the differential circuit 8,
It can be seen that the rotational angular velocity is not applied. When rotated about the axis of the vibrating body 3, the vibration direction of the vibrating body 3 changes due to Coriolis force. Thereby, the piezoelectric elements 4a, 4
A difference occurs in the output signal b, and a signal corresponding to the difference is output from the differential circuit 8. The output signal of the differential circuit 8 is detected by the synchronous detection circuit 9 in synchronization with the signal of the comparator circuit 6. The output signal of the synchronous detection circuit 9 is smoothed by a smoothing circuit 10 and further amplified by a DC amplifier circuit 11.

Since the change in the vibration direction of the vibrator 3 corresponds to the Coriolis force, the change in the output signals of the piezoelectric elements 4a and 4b also corresponds to the Coriolis force. Therefore, a signal corresponding to the Coriolis force is output from the differential circuit 8. Therefore, a signal obtained by smoothing and amplifying the output signal of the differential circuit 8 also corresponds to the Coriolis force. Since the Coriolis force corresponds to the rotational angular velocity applied to the vibrating gyroscope 1, the rotational angular velocity applied to the vibrating gyroscope 1 can be detected by measuring the output signal of the DC amplifier circuit 11.

[0007]

However, even when the rotational angular velocity is not applied, an offset drift is output from the differential circuit. This drift component has a phase difference from a reference signal for synchronous detection. FIG.
Is a graph showing drift components detected in synchronization with the reference signal. The output signal d when the drift component detected in this way is smoothed is expressed by the following equation (1).

[0008]

(Equation 1)

Here, f is the frequency of the reference signal and the drift, and α is the phase difference between the reference signal and the drift signal. As can be seen from equation (1), when α = π / 2, the positive part and the negative part cancel each other, and the drift component becomes zero. However, the phase of the drift component has a temperature characteristic, and the phase may be different depending on each temperature. For example, if the phase of the drift component changes due to a temperature change, the positive and negative parts of the drift component detected by the synchronous detection circuit will not be equal, and a signal corresponding to the difference will be output from the DC amplifier circuit. become.

In order to suppress such drift components, it is conceivable to improve the temperature characteristics of the piezoelectric element or cancel the temperature characteristics of the gyro output generated at each temperature. As the former method, there is a method of reducing the direction variation of the piezoelectric element, but there is a limit in the property of the material. In the latter method, the tendency of each piezoelectric element varies widely, and correction is practically impossible.

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a vibrating gyroscope capable of removing a drift component by using a simple circuit without individually correcting the temperature characteristics of the vibrator.

[0012]

According to the present invention, there is provided a vibrator for outputting a signal corresponding to a rotational angular velocity by utilizing the vibration of a vibrating body, and for detecting an output signal of the vibrator in synchronization with a reference signal. A vibration gyro includes a synchronous detection circuit and a phase shift circuit for adjusting a phase of a reference signal according to a temperature. Such a vibrating gyroscope includes an oscillation circuit for forming a drive signal for vibrating the vibrator from an output signal of the vibrator, and a signal of the oscillation circuit is phase-corrected by a phase shift circuit to form a reference signal. You. The phase shift circuit includes a temperature sensing element.

By using a phase shift circuit having a temperature characteristic corresponding to the temperature characteristic of the drift component included in the output signal of the oscillator, the drift component and the π /
A reference signal having a phase difference of 2 can be obtained. Therefore, if the output signal of the oscillator is detected in synchronization with the reference signal, it is possible to detect a drift component in which the positive portion and the negative portion are substantially the same, and smooth the drift component to obtain a positive component and a negative component. Parts and can be offset.

In order to obtain such a reference signal, a signal can be taken out from an oscillation circuit for driving the vibrator, and the signal can be phase-corrected by a phase shift circuit. At this time,
By including a temperature-sensitive element in the phase shift circuit, the output signal of the phase shift circuit can have a temperature characteristic.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the accompanying drawings.

[0016]

FIG. 1 is a block diagram showing an example of a vibrating gyroscope according to the present invention. The vibrating gyro 20
The vibrator 22 is included. The vibrator 22 includes, for example, a regular triangular prism-shaped vibrator 24 as shown in FIGS. The vibrating body 24 is generally formed of a material that generates mechanical vibration, such as an elinvar, an iron-nickel alloy, quartz, glass, quartz, or ceramic.

On the three side surfaces of the vibrating body 24, piezoelectric elements 26a, 26b and 26c are formed, respectively. The piezoelectric element 26a includes a piezoelectric layer 28a formed of, for example, a piezoelectric ceramic. The electrodes 30 are provided on both sides of the piezoelectric layer 28a.
a, 32a are formed. Then, one electrode 32a
Is adhered to the side surface of the vibrating body 24. Similarly, the piezoelectric elements 26b and 26c include piezoelectric layers 28b and 28c, and electrodes 30b and 32b are provided on both surfaces of the piezoelectric layers 28b and 28c.
And the electrodes 30c and 32c. Then, one of the electrodes 32b and 32c of the piezoelectric elements 26b and 26c is bonded to the side surface of the vibrator 24.

The piezoelectric elements 26a and 26b are connected to a reference potential via resistors 34a and 34b, respectively. Further, the piezoelectric elements 26a, 26b are connected to the buffer circuits 36a,
36b. The output signals of the buffer circuits 36a and 36b are combined and input to the oscillation circuit 38. The oscillation circuit 38 includes an inverting amplification circuit 40 and an automatic gain control circuit (AG
C circuit 42), and the signal obtained by combining the outputs of the buffer circuits 36a and 36b is processed by the oscillation circuit 38 and supplied to the piezoelectric element 26c as a drive signal.

Further, the output signals of the buffer circuits 36a and 36b are input to the detection circuit 44. The detection circuit 44 includes a differential circuit 46, and a difference between output signals of the buffer circuits 36a and 36b is output from the differential circuit 46. Differential circuit 4
The output signal of No. 6 is detected by the synchronous detection circuit 48 in synchronization with the reference signal. The reference signal is obtained by adjusting the phase of the output signal of the inverting amplifier circuit 40. At this time,
The output signal of the inverting amplifier circuit 40 is input to the phase shift circuit 50, and the phase is adjusted by the phase shift circuit 50.

The phase shift circuit 50 is formed, for example, by connecting resistors R1, R2, R3, capacitors C1, C2 and a thermistor N1 as a temperature sensing element in a ladder shape as shown in FIG. In this phase shift circuit 50, a first parallel circuit in which a resistor R1 and a capacitor C1 are connected in parallel, a second parallel circuit in which a resistor R2 and a thermistor N1 are connected in parallel, a resistor R3 and a capacitor C2 Are connected in series with each other. An output signal of the inverting amplifier circuit 40 is input to the first parallel circuit, and a reference signal is output from an intermediate portion between the second parallel circuit and the third parallel circuit. In the phase shift circuit 50, since the thermistor N1 is incorporated, the impedance changes depending on the temperature, and the phase of the reference signal is adjusted. The output signal of the synchronous detection circuit 48 is smoothed by the smoothing circuit 52, and the output signal of the smoothing circuit 52 is further
Amplified at 4.

In such a vibrating gyroscope 20, the piezoelectric element 26c expands and contracts by the drive signal obtained by the oscillation circuit 38, whereby the vibrating body 24 bends and vibrates in a direction perpendicular to the surface on which the piezoelectric element 26c is formed. At the time of no rotation, the bending state of the piezoelectric elements 26a and 26b becomes the same,
The output signal is the same. Therefore, no signal is output from the differential circuit 46, and it can be seen that the rotational angular velocity is not applied.

When rotating about the axis of the vibrating body 24,
The direction of vibration of the vibrating body 24 is changed by the Coriolis force.
Therefore, the bending state of the piezoelectric elements 26a and 26b changes, and different signals are output from the piezoelectric elements 26a and 26b. Therefore, the differential circuit 46 outputs a signal corresponding to the difference between the output signals of the piezoelectric elements 26a and 26b. The output signal of the differential circuit 46 is
, The signal is detected in synchronization with the reference signal output from the phase shift circuit 50.

In the synchronous detection circuit 48, only the positive portion or only the negative portion of the output signal of the differential circuit 46, or a signal obtained by inverting either the positive or negative signal is detected. Then, the output signal of the synchronous detection circuit 48 is smoothed by the smoothing circuit 52 and further amplified by the DC amplifier circuit 54. The change in the vibration direction of the vibrating body 24 corresponds to the Coriolis force, and the piezoelectric element 26a,
The change in the output signal of 26b corresponds to the change in the vibration direction of the vibrating body 24. Therefore, the rotational angular velocity applied to the vibrator 22 can be detected from the level of the output signal of the DC amplifier circuit 54.

When the direction of the rotational angular velocity applied to the vibrator 22 is reversed, the direction of the generated Coriolis force is also reversed, and the change in the vibration direction of the vibrator 24 is also reversed. Therefore, the output signals of the piezoelectric elements 26a and 26b change in reverse, and the differential circuit 46 outputs a signal of the opposite polarity. Therefore, the polarity of the final output signal of the DC amplifier circuit 54 is also reversed.
Therefore, from the polarity of the output signal of the DC amplifier circuit 54,
The direction of the rotational angular velocity can be known.

In such a vibrating gyroscope 20, offset drift may be output even during non-rotation. When the frequency of the reference signal and the drift signal for synchronous detection is f, and the phase difference between the reference signal and the drift signal is α, such a drift component is expressed by Expression (1). Therefore, when α = π / 2, the synchronous detection circuit 48
The drift component detected in step (a) contains a positive part and a negative part in the same ratio, and the smoothing circuit 52 smoothes out the positive part and the negative part, thereby canceling the DC component.
4 does not output a drift component.

However, when the temperature changes, the phase of the drift component may change due to the temperature characteristics of the piezoelectric elements 26a to 26c. For example, as shown in FIG. 9, when the temperature rises, the phase of the drift component advances, and when the temperature falls, the phase of the drift component lags. However, in this vibration gyro 20, the phase shift circuit 5
Since 0 includes the thermistor N1, the resistance value of the thermistor N1 changes depending on the temperature, and the impedance of the phase shift circuit 50 also changes. Therefore, the phase of the output signal of the phase shift circuit 50 changes depending on the temperature.

Therefore, by using the thermistor N1 having appropriate temperature characteristics, it is possible to adjust the temperature change of the phase of the reference signal to the temperature change of the phase of the drift component. The phase shift amount of the phase shift circuit 50 can be obtained from the following equation. That is, the impedance Z ₂ of the parallel circuit of the impedance Z ₁ and the resistor R2 and the thermistor N1 of the parallel circuit of the resistor R1 and the capacitor C1 are represented by respectively formula (2) and (3) Synthesis of Z ₁ and Z ₂ The impedance Z ₁ + Z ₂ is represented by equation (4).

[0028]

(Equation 2)

[0029]

(Equation 3)

[0030]

(Equation 4)

In the equation (4), S = N1R2 +
R1R2 + N1R1, T = ωC1N1R1R2, V = N
1 + R2, W = ωC1R1. The impedance Z ₃ of the parallel circuit of the resistor R3 and the capacitor C2 is expressed by the following equation (5).

[0032]

(Equation 5)

In the equation (5), X = R3 and Y =
ωC2R3. And impedance Z ₁ ,
The combined impedance Z ₀ of Z ₂ and Z ₃ is given by the following equation (6)
It is represented by

[0034]

(Equation 6)

Where A = S + VX-TY, B = T + S
Y + VWX, D = V−VWY, and E = VW + VY.
Accordingly, the ratio of the input signal V _in and the output signal V _out is represented by the following equation (7).

[0036]

(Equation 7)

Where F = XD, G = EX, H = AB
Y, K = B + AY, L = FH + GK, M = GH-FK,
N = H ² + K ² . Therefore, the phase shift amount θ between the input signal and the output signal is expressed by the following equation (8).

[0038]

(Equation 8)

By matching the phase shift amount θ with the temperature characteristics of the drift component, it is possible to detect the drift component so that the positive part and the negative part are equal. Thus, the vibrating gyroscope 20 with a small drift component output from the DC amplifier circuit 54 can be obtained regardless of the temperature change.

As an experimental example, the phase shift circuit 50 shown in FIG.
FIG. 5 shows the temperature characteristics. Here, since a negative temperature coefficient thermistor is used as the thermistor N1, the phase changes in a high temperature part in a direction in which the phase advances, and in a low temperature part, the phase changes in a direction in which the phase delays. Thereby, the optimum synchronous detection phase can be obtained at each temperature, and as a result, the offset drift characteristics can be reduced. Phase shift circuit 5
FIG. 6 shows the offset drift characteristics for the case where 0 is used and the case where it is not used. As can be seen from FIG.
The temperature characteristic component represented by the quadratic function can be easily corrected.

Note that the linear function component has a resistance R3
By varying the resistance R2 for the quadratic function component, the phase shift curve in FIG. 5 can be changed. Thus, the temperature characteristics represented by the linear function and the quadratic function can be easily corrected. In addition, as a temperature sensing element,
For example, if an element having a linear characteristic such as a temperature compensating capacitor is used, the phase shift temperature characteristic becomes linear. That is, the characteristic of FIG. 5 has a quadratic function characteristic due to the characteristics of the thermistor.
This is because the temperature characteristics of FIG. Therefore, if the vibrator 22 has a linear temperature characteristic, a temperature-sensitive element having a linear temperature characteristic can be used.

As described above, the temperature-sensitive element is not limited to the thermistor, but may be one having characteristics according to the characteristics of the vibrator. In addition, the vibrator is not limited to a vibrator using a triangular prism-shaped vibrator, but may be a vibrator of various shapes such as a vibrator using another rectangular vibrator such as a quadrangular prism or a vibrator having a columnar shape. A vibrator using a body can be used. Further, a vibrator in which electrodes are formed on a vibrating body formed of a piezoelectric body may be used.

Further, as shown in FIG. 7, a bimorph type vibrator can be used. In this vibrator 60, two piezoelectric substrates 64 and 66 are laminated with an internal electrode 62 interposed therebetween. The piezoelectric substrates 64 and 66 are provided with the internal electrodes 62.
A driving electrode 68 is formed on the entire surface of one of the piezoelectric substrates 66. On the other piezoelectric substrate 64, detection electrodes 70 and 72 divided in the width direction are formed. In such a vibrator 60, the output signals of the detection electrodes 70 and 72 are
6a and 36b, the output signal of the oscillation circuit 38 is given to the driving electrode 68. Also for such a vibrator 60, the temperature characteristics of the drift component can be corrected by using the phase shift circuit 50.

The phase shift circuit 50 is not limited to a ladder type circuit as shown in FIG. 4, but may be another circuit according to the characteristics of the vibrator 22. Even when another circuit is used as the phase shift circuit 50, by using an appropriate temperature sensing element, the phase of the reference signal can be adjusted, and a vibrating gyroscope with a small drift component can be obtained.

[0045]

According to the present invention, it is possible to obtain a vibration gyro having a small drift component by correcting the temperature characteristics of the offset drift of the vibration gyro. Therefore, even if the temperature changes, the rotational angular velocity can be accurately detected. Moreover, it is not necessary to adjust the vibrator, and the temperature characteristics of the offset drift can be corrected only by adding a simple circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a vibrating gyroscope according to the present invention.

FIG. 2 is a perspective view showing an example of a vibrator used in the vibrating gyroscope shown in FIG.

FIG. 3 is a sectional view of the vibrator shown in FIG. 2;

FIG. 4 is a circuit diagram showing an example of a phase shift circuit used in the vibration gyro shown in FIG.

FIG. 5 is a graph showing a temperature characteristic of an output signal of the phase shift circuit shown in FIG. 4;

FIG. 6 is a graph showing offset drift characteristics with and without a phase shift circuit.

FIG. 7 is an illustrative view showing another example of the vibrator used in the vibrating gyroscope according to the present invention;

FIG. 8 is a block diagram showing an example of a conventional vibrating gyroscope.

FIG. 9 is a graph showing the phase of a drift signal detected in synchronization with a reference signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Vibration gyroscope 22 Vibrator 24 Vibrator 26a, 26b, 26c Piezoelectric element 36a, 36b Buffer circuit 38 Oscillation circuit 40 Inverting amplifier circuit 42 AGC circuit 44 Detection circuit 46 Differential circuit 48 Synchronous detection circuit 50 Phase shift circuit 52 Smoothing circuit 54 DC amplifier circuit

Claims (3)

[Claims] 1. A vibrator for outputting a signal corresponding to a rotational angular velocity using vibration of a vibrating body, a synchronous detection circuit for detecting an output signal of the vibrator in synchronization with a reference signal, and corresponding to a temperature. A vibrating gyroscope including a phase shift circuit for adjusting a phase of the reference signal. 2. An oscillator circuit for forming a drive signal for oscillating the oscillator from an output signal of the oscillator, wherein a signal of the oscillator circuit is phase-corrected by the phase shift circuit and the reference signal is The vibrating gyro according to claim 1, wherein 3. The phase shift circuit includes a temperature sensing element.
The vibrating gyroscope according to claim 1.