JP2000221040A - Oscillation gyro - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation gyro capable of carrying out an accurate drift correction even in a small storage capacity, and capable of detecting angular velocity accurately in the whole temperature range. SOLUTION: This oscillation gyro 10 contains an angular velocity sensor 12 bendingly vibrating in an oscillation circuit 28. Two output signals of the sensor 12 are input into a differential ampififying circuit 30, and an output signal is detected by a synchronous detection circuit 32 to be amplified thereafter by a direct current amplifying circuit 34. An output signal of the amplifying circuit 34 and an output signal of a thermosensor 38 are converted into digital signals by A/D converters 36, 40 to be processed by a processor 42. A temperature drift is measured preliminarily by changing a temperature, a change of the temperature drift is approximated by a function of degree (n), and a resulting coefficient parameter is stored in the processor 42. A drift value at the time of use is calculated based on the coefficient parameter to conduct correction, and accurate angular velocity is detected thereby.

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 used for detecting an angular velocity, for example, for a car navigation system or for preventing camera shake.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing an example of a conventional vibrating gyroscope. The vibration gyro 1 includes an angular velocity sensor 2. As the angular velocity sensor 2, for example, a sensor in which piezoelectric elements 4a, 4b, and 4c are formed on the side surface of a regular triangular prism-shaped vibrator 3 is used. And the piezoelectric elements 4a, 4b
An oscillation circuit 5 is connected between the piezoelectric element 4c. Further, the piezoelectric elements 4a and 4b are connected to the input terminals of the differential amplifier circuit 6. The output signal of the differential amplifier circuit 6 is connected to a synchronous detection circuit 7, and the synchronous detection circuit 7 further includes a DC amplification circuit 8
Connected to.

In such a vibrating gyroscope 1, the output signal of the piezoelectric element 4c is fed back to the oscillation circuit 5, and this signal is amplified and phase-corrected, and then input as a drive signal to the piezoelectric elements 4a and 4b. . Thereby, the vibrating body 3
Vibrates in a direction perpendicular to the surface on which the piezoelectric element 4c is formed. At this time, the bending states of the piezoelectric elements 4a and 4b are the same, and the same signals are output from these piezoelectric elements 4a and 4b. Therefore, no signal is output from the differential amplifier circuit 6 and no signal is output from the DC amplifier circuit 8.
Therefore, it is understood that the angular velocity is not applied to the angular velocity sensor 2.

In this state, when an angular velocity is applied about the axis of the vibrating body 3, Coriolis force acts in a direction orthogonal to the bending vibration. This Coriolis force changes the vibration direction of the vibrating body 3. Therefore, a difference occurs in the bending state of the piezoelectric elements 4a and 4b, and the output signal increases in one of the piezoelectric elements 4a and 4b in accordance with the Coriolis force, and decreases in the other in accordance with the Coriolis force. . Therefore, a large output signal corresponding to the Coriolis force can be obtained from the differential amplifier circuit 6. Then, in the synchronous detection circuit 7, the output signal of the differential amplifier circuit 6 is detected in synchronization with the signal of the oscillation circuit 5. As a result, only the positive portion or only the negative portion of the output signal of the differential amplifier circuit 6 or a signal obtained by inverting either the positive portion or the negative portion is detected. This signal is amplified by the DC amplifier circuit 8, and a DC signal corresponding to the Coriolis force is obtained. When the directions of the angular velocities are opposite, the synchronous detection circuit 7 detects a portion of the output signal of the differential amplifier circuit 6 having the opposite polarity. Therefore, the direction of the angular velocity can be known from the polarity of the output signal of the DC amplifier circuit 8.

[0005]

However, the angular velocity sensor has a temperature drift, and when the ambient temperature changes, the output signal of the angular velocity sensor changes. Therefore, even if the angular velocity applied to the angular velocity sensor is the same, if the ambient temperature changes, the output signal changes, and it is not possible to detect an accurate angular velocity. Therefore, in order to correct the temperature drift, for each vibration gyro, the temperature is changed in advance and the temperature drift is actually measured, the drift value at each temperature is stored in a ROM or the like, and when the vibration gyro is actually used, It is conceivable to measure the temperature with a temperature sensor, read the drift value at that temperature from the ROM, and correct the output signal of the vibrating gyroscope.

[0006] However, the temperature drift varies depending on the individual vibrating gyroscopes, and does not change in proportion to the temperature change. Therefore, in order to correct accurately, the temperature is finely changed and the drift at each temperature is changed. The value must be measured. In order to store many drift values at each temperature, it is necessary to increase the storage capacity of the ROM. Also, if the width of temperature change is increased, the number of actually measured drift values decreases, but accurate correction cannot be performed because the number of data is small.

[0007] Therefore, a main object of the present invention is to provide a vibrating gyroscope capable of accurately performing drift correction even with a small storage capacity and accurately detecting an angular velocity over the entire temperature range. .

[0008]

SUMMARY OF THE INVENTION The present invention provides an angular velocity sensor for outputting a signal corresponding to an angular velocity, a processing device for processing an output signal of the angular velocity sensor, and an apparatus for measuring a temperature near the angular velocity sensor. A temperature sensor, and stores a coefficient parameter obtained by approximating the drift of the angular velocity sensor measured by changing the temperature to an n-order function in a processing device, and from the coefficient parameter corresponding to the temperature measured by the temperature sensor. A vibration gyro is characterized in that an output signal of an angular velocity sensor is corrected by a calculated correction value. The vibrating gyroscope includes an A / D converter for converting an output signal of the angular velocity sensor and an output signal of the temperature sensor into a digital signal, and the digital signal converted by the A / D converter is processed by the processing device.

The temperature drift is actually measured, and the obtained result is expressed as n
By approximating the following function, it is possible to obtain a function that changes close to the actual temperature drift with n + 1 coefficient parameters. Therefore, when the vibrating gyroscope is actually used, the drift value at each temperature can be calculated from the obtained function by measuring the temperature with the temperature sensor. Therefore, if the output signal of the angular velocity sensor is corrected based on the calculated drift value, an accurate angular velocity can be detected. When the temperature drift changes in a complicated manner, it is necessary to increase the value of n in the n-th order function approximation.
Even if the change is quite complicated, the temperature drift can be accurately approximated to the degree of the fourth-order function approximation or the fifth-order function approximation.

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.

[0011]

FIG. 1 is a block diagram showing an example of a vibrating gyroscope according to the present invention. The vibrating gyro 10
An angular velocity sensor 12 is included. As shown in FIG. 2, the angular velocity sensor 12 includes a regular triangular prism-shaped vibrating body 14, for example.
The vibrating body 14 includes, for example, an elinvar, an iron-nickel alloy,
It is generally formed of a material that generates mechanical vibration, such as quartz, glass, quartz, and ceramic. Piezoelectric elements 16a, 16b, 16c are formed on three side surfaces of the vibrating body 14, respectively.

As shown in FIG. 3, the piezoelectric element 16a includes a piezoelectric layer 18a made of, for example, a piezoelectric ceramic. Electrodes 20a and 22a are formed on both surfaces of the piezoelectric layer 18a. Then, one electrode 22a is bonded to the side surface of the vibrating body 14. Similarly, the piezoelectric elements 16b and 16c include piezoelectric layers 18b and 18c, and electrodes 20b and
22b and the electrodes 20c and 22c are formed. Then, one electrode 22 of these piezoelectric elements 16b, 16c
b and 22c are adhered to the side surface of the vibrating body 14.

Resistors 24 and 26 are connected to the piezoelectric elements 16a and 16b, respectively. An oscillation circuit 28 is connected between the resistors 24 and 26 and the piezoelectric element 16c.
In this case, the output signal from the piezoelectric element 16c is fed back to the oscillation circuit 28. Then, in the oscillation circuit 28, the feedback signal is amplified and the phase is adjusted to form a drive signal. This drive signal is applied to the piezoelectric elements 16a, 1
6b, whereby the vibrating body 14 bends and vibrates.

Further, the piezoelectric elements 16a and 16b are connected to the input terminals of the differential amplifier circuit 30. Differential amplifier circuit 30
Is connected to the synchronous detection circuit 32. In the synchronous detection circuit 32, the output signal of the differential amplifier circuit 30 is detected in synchronization with the signal of the oscillation circuit 28. Further, the synchronous detection circuit 32 is connected to a DC amplification circuit 34. The DC amplifier 34 is connected to an A / D converter 36 for converting an analog signal into a digital signal. A temperature sensor 38 is provided near the angular velocity sensor 12, and the temperature sensor 38 is connected to another A / D converter 40. Then, the two A / D converters 36 and 40 are connected to the processing device 42. In the processing device 42, the output signal of the angular velocity sensor 12 is processed according to the output signal of the temperature sensor 38.

In the vibrating gyroscope 10, the oscillation circuit 28
The piezoelectric elements 16a and 16b expand and contract due to the drive signal from the piezoelectric element 16b, whereby 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 element 16
The bending states of the piezoelectric elements 16a and 16b are the same, and the same signals are output from these piezoelectric elements 16a and 16b. Therefore, no signal is output from the differential amplifier circuit 30.

When an angular velocity is applied about the axis of the angular velocity sensor 12, Coriolis force acts in a direction orthogonal to the direction of the bending vibration of the vibrating body 14. Thereby, the direction of the bending vibration of the vibrating body 14 changes. Therefore, the piezoelectric elements 16a, 16
There is a difference in the bending state of the piezoelectric element 16b.
There is a difference between the output signals a and 16b. Since the change in the vibration direction of the vibrating body 14 corresponds to the Coriolis force, the change in the output signals of the piezoelectric elements 16a and 16b also corresponds to the Coriolis force. That is, when one of the output signals of the piezoelectric elements 16a and 16b increases in accordance with the Coriolis force, the other output signal decreases in accordance with the Coriolis force. Therefore, a large output signal corresponding to the Coriolis force can be obtained from the differential amplifier circuit 30.

The output signal of the differential amplifier circuit 30 is detected by the synchronous detection circuit 32 as a signal having only a positive portion or only a negative portion, or a signal obtained by inverting either the positive portion or the negative portion. The signal detected by the synchronous detection circuit 32 is applied to a DC amplification circuit 34.
Amplified by Therefore, the magnitude of the angular velocity applied to the angular velocity sensor 12 can be known from the level of the output signal of the DC amplifier circuit 34. When the direction of the angular velocity applied to the angular velocity sensor 12 is reversed, the synchronous detection circuit 3
In step 2, the polarity of the detected signal is reversed. Therefore, the polarity of the output signal from the DC amplification circuit 34 is also reversed. Therefore, the direction of the angular velocity applied to the angular velocity sensor 12 can be known from the polarity of the output signal of the DC amplifier circuit 34.

The output signal of the DC amplifier circuit 34 is input to an A / D converter 36, and an angular velocity signal converted into a digital signal is obtained. A temperature sensor 38 is provided near the angular velocity sensor 12. This temperature sensor 38
Is input to another A / D converter 40,
A temperature signal converted into a digital signal is obtained. The output signals of the two A / D converters 36 and 40 are
The data is input to the processing device 42. The angular velocity signal obtained from the A / D converter 36 is processed according to the temperature signal obtained from the A / D converter 40.

In the vibrating gyroscope 10, the processing device 42
In order to process the angular velocity signal by the
Is stored. A coefficient parameter for calculating the temperature drift of is stored. FIG. 4 shows a flowchart for obtaining such coefficient parameters. First, the temperature drift of the angular velocity sensor 12 is actually measured. Therefore, in step S1, the initial measurement is started. That is, the angular velocity sensor 12
The angular velocity signal from the A / D converter 36 is measured in a state where the angular velocity is not applied to. Such measurement is performed while changing the temperature. In step S2, it is determined whether the measurement has been performed at all predetermined temperatures. If the measurement is not completed at a plurality of predetermined temperatures, the measurement is further continued.

When the measurement of the temperature drift is continued, the angular velocity signal from the A / D converter 36 is fetched in step S3. Further, in step S4, a temperature signal from the A / D converter 40 is taken in, and the current temperature is calculated. Then, such measurement is performed while changing the temperature. When the angular velocity signal at the predetermined temperature is captured, the measurement is completed. As described above, by changing the temperature in a state where the angular velocity is not given and measuring the angular velocity signal, the temperature drift can be actually measured. When the measurement is completed, step S
At 5, an n-order function approximation is performed based on the obtained data. That is, as shown in FIG. 5, an approximate expression that obtains a curve close to the actually measured temperature drift is obtained, and the coefficient parameter of the obtained approximate expression is stored in the processing device 42 in step S6. FIG. 5 shows a curve obtained by cubic function approximation based on the actually measured temperature drift.

These steps S1 to S6 are performed in the process of manufacturing the vibrating gyroscope 10, and the vibrating gyroscope 10 having the processing device 42 storing the coefficient parameters is shipped. Of course, a program for correcting the temperature drift using the stored coefficient parameters is incorporated in the processing device 42.

When the user uses the vibrating gyroscope 10, the temperature drift is corrected according to the flowchart shown in FIG. First, in step S10, initialization is performed. Here, the stored coefficient parameters are called. Next, in step S11, an angular velocity signal is captured. Further, in step S12,
A temperature signal is captured. Then, the current temperature is calculated from the temperature signal. Next, in step S13,
A drift value at the current temperature is calculated from an n-order function using the stored coefficient parameters. This drift value becomes the correction value. Then, in step S14, the correction value is subtracted from the angular velocity signal, and the angular velocity signal is corrected. Thus, in step S15, an accurate angular velocity value from which the drift component has been removed is output. By repeating such steps S11 to S15, an accurate angular velocity value can be obtained regardless of the temperature change.

When the correction is performed by these steps, and when the drift signal shown in FIG. 5 is corrected by using a curve obtained by approximating a cubic function, as shown in FIG. Have been obtained. In the characteristic shown in FIG. 5, the difference between the maximum value and the minimum value of the temperature drift is about 620.
In contrast to FIG. 7, it is about 157 mV in FIG. Further, when a vibration gyro having the same drift characteristic is corrected by performing a quadratic function approximation, the difference between the maximum value and the minimum value of the temperature drift is about 8 as shown in FIG.
6 mV. In addition, as shown in FIG. 9, when the correction was performed by performing a quintic function approximation, as shown in FIG. 9, the difference between the maximum value and the minimum value of the temperature drift was 79 mV.

As described above, by increasing the order of approximation of the n-th order function, it is possible to obtain a function representing a curve close to the actual drift change. By performing correction using this function, vibration having a small temperature drift can be obtained. The gyro 10 can be obtained. In each of the vibrating gyroscopes 10,
Since the temperature drift changes in different ways, the coefficient parameter is determined in each vibrating gyroscope 10. Since such setting of the processing device 42 is performed at the time of manufacturing the vibration gyro 10, the user can obtain a vibration gyro without variation in quality.

When the change of the temperature drift is complicated,
Although it is necessary to increase the order of the n-th order function approximation, in most cases, to the degree of the fourth or fifth order function approximation,
It is possible to correct the angular velocity signal accurately. In the n-order function approximation, n + 1 coefficient parameters are obtained. However, even when the quintic function approximation is performed, the obtained coefficient parameters are six, and it is not necessary to increase the storage capacity of the processing device 42.

The vibration gyro 10 shown in FIG.
Although an angular velocity sensor in which a piezoelectric element is bonded to a regular triangular prism-shaped vibrator is used, other angular velocity sensors such as an angular velocity sensor using a bimorph-type vibrator in which two piezoelectric plates are bonded are used as the angular velocity sensor. Can be used.
That is, for any angular velocity sensor, the temperature drift is actually measured, a function having a curve close to the change in the temperature drift is derived by approximation of an n-th order function, and a correction value is obtained from this function to obtain a storage capacity. It is possible to output an accurate angular velocity value even if a processing device having a small value is used.

[0027]

According to the present invention, accurate correction of temperature drift can be performed using a processing device having a small storage capacity, and accurate correction can be performed for each vibration gyro. Therefore, an accurate angular velocity value can be output for all the vibrating gyroscopes even if there is a temperature change, and a vibrating gyroscope with small variation in characteristics can be obtained.

[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 an angular velocity sensor used in the vibration gyro shown in FIG.

FIG. 3 is a sectional view of the angular velocity sensor shown in FIG. 2;

FIG. 4 is a flowchart showing a process of setting a processing device in the vibrating gyroscope shown in FIG. 1;

5 is a graph showing a temperature drift and a curve obtained by performing a cubic function approximation in the flowchart shown in FIG. 4;

FIG. 6 is a flowchart showing a process performed by the processing device when using the vibrating gyroscope adjusted in the process shown in FIG. 4;

7 is a graph showing the actually measured angular velocity signal shown in FIG. 5 and the output corrected by the correction value obtained by the cubic function approximation.

8 is a graph showing the actually measured angular velocity signal shown in FIG. 5 and an output corrected by a correction value obtained by a quadratic function approximation.

9 is a graph showing the actually measured angular velocity signal shown in FIG. 5 and an output corrected by a correction value obtained by a quintic function approximation.

FIG. 10 is a block diagram showing an example of a conventional vibrating gyroscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration gyroscope 12 Angular velocity sensor 14 Vibration body 16a, 16b, 16c Piezoelectric element 28 Oscillation circuit 30 Differential amplification circuit 32 Synchronous detection circuit 34 DC amplification circuit 36 A / D converter 38 Temperature sensor 40 A / D converter 42 Processing device

Claims (2)

[Claims] An angular velocity sensor for outputting a signal corresponding to the angular velocity; a processing device for processing an output signal of the angular velocity sensor; and a temperature sensor for measuring a temperature near the angular velocity sensor. A coefficient parameter obtained by approximating the drift of the angular velocity sensor measured by changing it to an n-order function is stored in the processing device, and a correction value calculated from the coefficient parameter corresponding to the temperature measured by the temperature sensor A vibration gyro, wherein the output signal of the angular velocity sensor is corrected by the following. 2. An A / D converter for converting an output signal of the angular velocity sensor and an output signal of the temperature sensor into a digital signal, wherein the digital signal converted by the A / D converter is processed by the processing device. The vibrating gyroscope according to claim 1, wherein the gyroscope is operated.