JP2000171258A - Oscillation gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oscillation gyro in which temperature drift is suppressed. SOLUTION: An oscillation gyro 10 comprises an oscillator 12 where piezoelectric elements 16a, 16b, 16c are formed on the side faces of an oscillator 14. An oscillation circuit 22 is connected between the piezoelectric elements 16a, 16b and the piezoelectric element 16c in order to generate bending oscillation of the oscillator 14 in the direction orthogonal to the plane for forming the piezoelectric element 16c. The piezoelectric elements 16a, 16b, 16c are connected with a detecting circuit 24 in order to produce a signal corresponding to the rotational angular speed. The detecting circuit 24 is provided with such temperature characteristics as the gain is varied by temperature variation.

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 requiring a low temperature drift, such as a vibrating gyroscope used for a car navigation system or a pointing device.

[0002]

2. Description of the Related Art FIG. 1 is an illustrative view showing one example of a vibrating gyroscope as a background of the present invention. The vibrating gyro 10
The vibrator 12 is included. The vibrator 12, as shown in FIG.
It includes a regular triangular prism-shaped vibrating body 14. The vibrating body 14 is made of, for example, elinvar, iron-nickel alloy, quartz, glass, quartz,
It is generally formed of a material that generates mechanical vibration, such as ceramic.

[0003] Piezoelectric elements 16a, 16b and 16c are formed on three side surfaces of the vibrating body 14, respectively. These piezoelectric elements 16a, 16b and 16c include a piezoelectric layer made of, for example, porcelain, and electrodes are formed on both surfaces of the piezoelectric layer. Then, the piezoelectric elements 16a, 16b, 16
One electrode c is bonded to three side surfaces of the vibrating body 14.

[0004] Resistors 18 and 20 are connected to the piezoelectric elements 16a and 16b, respectively. And these resistors 1
An oscillation circuit 22 is connected between 8, 20 and the piezoelectric element 16c. Then, an output signal from the piezoelectric element 16c is fed back to the oscillation circuit 22, and a drive signal obtained by amplifying and phase-correcting the amplified signal is supplied to the piezoelectric elements 16a and 16b. By this drive signal, the vibrating body 14 bends and vibrates in a direction orthogonal to the surface on which the piezoelectric element 16c is formed.

[0005] The two piezoelectric elements 16a and 16b are connected to a detection circuit 24. The detection circuit 24 includes a differential circuit 26, and the piezoelectric elements 16a, 16a
b is connected. The output terminal of the differential circuit 26 is connected to the synchronous detection circuit 28. In the synchronous detection circuit 28, the output signal of the differential circuit 28 is detected in synchronization with the signal of the oscillation circuit 22. The synchronous detection circuit 28 is connected to the smoothing circuit 30,
Further, the smoothing circuit 30 is connected to the amplifier circuit 32.

In the vibrating gyroscope 10, the oscillation circuit 22
Accordingly, the vibrating body 14 bends and vibrates in a direction orthogonal to the surface on which the piezoelectric element 16c is formed. At this time, the piezoelectric elements 16a, 1
Since the output signal of 6b is the same, no signal is output from the differential circuit 26. In this state, when the vibrating body 14 rotates around the axis, the vibration direction of the vibrating body 14 changes due to the Coriolis force. Thereby, the piezoelectric elements 16a, 16
A difference in the output signal occurs between b and the signal is output from the differential circuit 26. The output signal of the differential circuit 26 is a synchronous detection circuit 28
, And further smoothed by the smoothing circuit 30, and then amplified by the amplifier circuit 32. The output signal of the differential circuit 26 is
Since the change corresponds to the change in the vibration direction of the vibrating body 14, the rotational angular velocity applied to the vibrator 12 can be detected by measuring the output signal of the amplifier circuit 32.

[0007]

The vibrator is formed so as to output a signal which becomes a reference voltage at about 25 ° C. However, the output signal of the vibrator has a temperature drift, and the output signal depends on the ambient temperature. Changes. Such a temperature drift is caused by variations in assembly accuracy of the vibrator, and does not have a certain tendency. Therefore, it is necessary to measure the temperature drift after the manufacture of the vibrator, and to sort out the specifications.

[0008] Therefore, a main object of the present invention is to provide a vibrating gyroscope having a small temperature drift.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a vibrating gyroscope including a vibrator for outputting a signal corresponding to a rotational angular velocity and a detecting circuit for detecting an output signal of the vibrator. A vibrating gyroscope characterized in that the gain has a positive characteristic that increases with increasing temperature or a negative characteristic that decreases with increasing temperature. In such a vibrating gyroscope, the output voltage value of the detection circuit is set according to the temperature characteristics of the output signal of the vibrator. Further, it is preferable to include an offset adjustment circuit for making the output signal of the detection circuit close to the reference value.

Since the gain of the detection circuit has a positive characteristic or a negative characteristic with respect to a temperature change, a temperature drift of the vibrator is canceled out, and a vibration gyro having a small change in an output signal due to the temperature change can be obtained. Therefore, the output voltage of the detection circuit is set according to the temperature characteristics of the output signal of the vibrator. Furthermore, even if the temperature change of the output signal of the vibration gyro decreases, if the output signal deviates from the reference value, by using an offset adjustment circuit, a vibration gyro with a small temperature change of the output signal near the reference value is used. Obtainable.

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

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to a vibrating gyroscope shown in FIG. In the vibration gyroscope 10, a gain having a temperature characteristic as shown in FIG. 3A can be used as the gain of the detection circuit 24.
The characteristic shown in FIG. 3A has a positive characteristic in which the gain increases as the temperature increases. That is, FIG.
As shown in (b), as the temperature increases, the difference between the output voltage of the detection circuit 24 and the reference voltage _Vref increases. In FIG. 3, the output voltage and the reference voltage V
_The offset voltage, which is the difference from _ref , has a positive characteristic and the offset voltage has a negative characteristic, which are selected according to the temperature drift of the output signal of the vibrator 12.

For example, as shown in FIG.
Has a characteristic that the output voltage decreases as the temperature rises, the detection circuit 24
A gain having a positive offset voltage and a positive temperature characteristic is used. In this case, the temperature drift of the vibrator 12 and the temperature drift of the detection circuit 22 cancel each other out, and as shown in FIG. 5, an output signal having a positive offset voltage and having almost flat characteristics with respect to a temperature change is obtained. be able to.

As shown in FIG. 6, when the temperature drift of the resonator 12 has such a characteristic that the output voltage increases as the temperature rises, the detection circuit 24 has a negative offset voltage and a positive characteristic. The one having a gain having the following temperature characteristic is used. In this case, the temperature drift of the vibrator 12 and the temperature drift of the detection circuit 22 cancel each other out, and as shown in FIG. 7, an output signal having a negative offset voltage and having almost flat characteristics with respect to a temperature change is obtained. be able to.

Detection circuit 2 having such a gain characteristic
For example, an amplifier circuit as shown in FIG. The amplifier circuit includes an operational amplifier 34, the inverting input terminal resistor R ₁ is connected to operational amplifier 34, the reference voltage V non-inverting input terminal via a resistor R ₃
Connected to _ref . Further, a resistor R ₂ for negative feedback is connected between the inverting input terminal and the output terminal of the operational amplifier 34. This amplifying circuit functions as an inverting amplifying circuit, and an output voltage V amplifies a difference V ₀ between the input voltage and the reference voltage V _ref.
It is a circuit to get _out . Here, _assuming that the difference between the output voltage and the reference voltage is V _out , the relationship between V _out and V ₀ is expressed by the following equation. V _out = {(R ₂ + ΔR ₂ ) / (R ₁ + ΔR ₁ )} × V
₀ Here, [Delta] R ₁ and [Delta] R ₂ represents a respective temperature characteristics of the resistors R ₁ and R _2. That is, the resistors R ₁ and R ₂
The temperature characteristics of the output of the amplifier circuit can be adjusted by appropriately selecting the temperature characteristics. Further, the slope of _Vout changes depending on the magnitude of the circuit gain, but also changes depending on the offset voltage. Therefore, the oscillator 12 having a temperature drift in the output signal has an offset that minimizes the temperature drift. The voltage can be selected.

The gain of the detection circuit 24 is shown in FIG.
A material having a temperature characteristic as shown in FIG. The characteristic shown in FIG. 9A has a negative characteristic that the gain decreases as the temperature increases. That is, as shown in FIG. 9B, as the temperature rises, the difference between the output voltage of the detection circuit 24 and the reference voltage decreases. In FIG. 9B as well, there are a positive offset voltage characteristic and a negative offset voltage characteristic, which are selected according to the temperature drift of the output signal of the vibrator 12.

For example, as shown in FIG.
In the case where the temperature drift of No. 2 has such a characteristic that the output voltage decreases as the temperature rises, the detection circuit 24 having a gain in which the offset voltage is negative and has a negative temperature characteristic is used. In this case, the vibrator 12
And the temperature drift of the detection circuit 22 are canceled out, and as shown in FIG. 11, an output signal having a negative offset voltage and almost flat characteristics with respect to a temperature change can be obtained.

As shown in FIG. 12, when the temperature drift of the vibrator 12 has such a characteristic that the output voltage rises as the temperature rises, the detection circuit 24 has a positive offset voltage and a negative characteristic. The one having a gain having the following temperature characteristic is used. In this case, the temperature drift of the vibrator 12 and the temperature drift of the detection circuit 22 cancel each other, and
As shown in FIG. 13, it is possible to obtain an output signal having a positive offset voltage and substantially flat characteristics with respect to a temperature change. In these cases as well, an offset voltage that minimizes the temperature drift of the vibrator 12 having a temperature drift in the output signal can be selected.

It should be noted that even if the gain of the detection circuit 24 is given a temperature characteristic to cancel out the temperature drift of the output signal of the vibrator 12 and obtain a flat characteristic, FIG.
As can be seen from FIGS. 7, 11 and 13, the output signal has an offset voltage. In this case, when the vibrating gyroscope is incorporated into the device, a problem may occur in the algorithm of the gyro output processing circuit or software. Therefore, as shown in FIG. 14, it is preferable to provide an offset adjustment circuit 36 after the amplification circuit. As shown in FIGS. 15 and 16, the offset voltage of the output signal having a flat characteristic can be made almost zero, that is, almost equal to the reference voltage, by the offset adjusting circuit 36. Can be eliminated.

FIGS. 17 to 20 show graphs of the output voltage with respect to the temperature in the experimental examples using the detection circuit 24 having the gain characteristic and the offset adjustment circuit 36 as described above. 17 to 20, a line connecting diamonds indicates an output voltage of the vibrator 12, and a line connecting squares indicates an output voltage when an amplifier having a temperature characteristic in gain is used to correct temperature drift. Indicate the output voltage when the offset voltage is further adjusted using the offset adjustment circuit 36.

As can be seen from FIGS. 17 to 20, the output voltage of the vibrator 12 has a flat characteristic by the amplifier circuit, and further, by using the offset adjusting circuit, the output characteristic of the vibrator 12 has a flat characteristic near the reference voltage of 2.5 V. Output. In this experimental example, since an inverting amplifier was used for the offset adjustment circuit,
The output waveform of the amplifier circuit and the output waveform of the offset adjustment circuit are mutually inverted.

As described above, by giving the temperature characteristic to the gain of the detection circuit 24, the temperature drift of the output signal of the vibrator 12 is canceled, and a flat waveform can be obtained. Therefore, the change in the output of the vibrating gyroscope 10 does not fluctuate much due to the change in the ambient temperature, and the rotational angular velocity can be accurately detected. Further, by adding the offset adjusting circuit 36, the output signal of the vibrating gyroscope 10 can be detected near the reference voltage, and when the vibrating gyroscope 10 is used, it is possible to eliminate problems in peripheral circuits and software. it can.

In order to provide the gain of the detection circuit 24 with a temperature characteristic, not only the circuit shown in FIG. 8 but also an element having a temperature characteristic such as a diode can be used, and the method is not limited. . The vibrator 12 is not limited to a regular triangular prism as shown in FIG.
Other pillars such as a quadrangular pillar or a column may be used, or a tuning fork type may be used, and the invention can be applied to a vibrator having a temperature drift in an output signal.

[0024]

According to the present invention, it is possible to eliminate the temperature drift of the output signal of the vibrator and to obtain a vibrating gyroscope in which the output signal does not fluctuate even when the ambient temperature changes. Therefore, it is possible to accurately detect the rotational angular velocity regardless of a change in the ambient temperature. Further, by using the offset adjustment circuit, it is possible to easily incorporate the vibrating gyroscope into the device.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of a vibrating gyroscope as a background of the present invention;

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

FIG. 3A is a characteristic diagram showing a positive characteristic gain as an example of the temperature characteristic of the gain of the detection circuit used in the present invention, and FIG. 3B is a detection circuit having the circuit gain of FIG. FIG. 6 is a diagram showing a relationship between the offset voltage and its temperature drift.

FIG. 4 is a characteristic diagram illustrating an example in which a detection circuit having a positive characteristic gain is applied to a vibrator whose output voltage decreases as the temperature increases.

FIG. 5 is a characteristic diagram showing an output of the detection circuit in the case shown in FIG.

FIG. 6 is a characteristic diagram illustrating an example in which a detection circuit having a positive characteristic gain is applied to a vibrator whose output voltage increases as the temperature increases.

FIG. 7 is a characteristic diagram showing an output of the detection circuit in the case shown in FIG.

FIG. 8 is a circuit diagram showing an example of an amplifier circuit used to give a temperature characteristic to the gain of the detection circuit.

9 (a) is a characteristic diagram showing a negative characteristic gain as another example of the temperature characteristic of the gain of the detection circuit used in the present invention, and FIG. 9 (b) has the circuit gain of FIG. 9 (a). FIG. 4 is a diagram illustrating a relationship between an offset voltage of a detection circuit and a temperature drift thereof.

FIG. 10 is a characteristic diagram illustrating an example in which a detection circuit having a negative characteristic gain is applied to a vibrator whose output voltage decreases as the temperature increases.

11 is a characteristic diagram showing an output of the detection circuit in the case shown in FIG.

FIG. 12 is a characteristic diagram illustrating an example in which a detection circuit having a negative characteristic gain is applied to a vibrator whose output voltage increases with an increase in temperature.

FIG. 13 is a characteristic diagram showing an output of the detection circuit in the case shown in FIG.

FIG. 14 is a circuit diagram showing an example in which an offset adjustment circuit is connected to the amplifier circuit shown in FIG.

FIG. 15 is a characteristic diagram illustrating an example in which an offset adjustment circuit is applied when the output voltage of the amplifier circuit has a positive offset voltage.

FIG. 16 is a characteristic diagram showing an example in which an offset adjustment circuit is applied when the output voltage of the amplifier circuit has a negative offset voltage.

FIG. 17 is a graph showing an experimental example in which outputs of a vibrator, an amplifier circuit, and an offset adjustment circuit are measured.

FIG. 18 is a graph showing another experimental example in which outputs of a vibrator, an amplifier circuit, and an offset adjustment circuit were measured.

FIG. 19 is a graph showing still another experimental example in which outputs of a vibrator, an amplifier circuit, and an offset adjustment circuit were measured.

FIG. 20 is a graph showing another experimental example in which outputs of a vibrator, an amplifier circuit, and an offset adjustment circuit were measured.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration gyroscope 12 Vibrator 14 Vibrating body 16a, 16b, 16c Piezoelectric element 22 Oscillation circuit 24 Detection circuit 26 Differential circuit 28 Synchronous detection circuit 30 Smoothing circuit 32 Amplification circuit 34 Operational amplifier 36 Offset adjustment circuit

Claims (3)

[Claims] 1. A vibrating gyroscope comprising: a vibrator that outputs a signal corresponding to a rotational angular velocity; and a detection circuit for detecting an output signal of the vibrator, wherein a gain of the detection circuit increases with an increase in temperature. A vibrating gyroscope having a positive characteristic that rises or a negative characteristic that decreases with increasing temperature. 2. The vibrating gyroscope according to claim 1, wherein the detection circuit output voltage value is set according to a temperature characteristic of an output signal of the vibrator. 3. The vibrating gyroscope according to claim 1, further comprising an offset adjusting circuit for bringing an output signal of the detecting circuit closer to a reference value.