JP3391098B2 - Vibrating gyro - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrating gyroscope, and more particularly to a vibrating gyroscope having improved response performance. 2. Description of the Related Art As a conventional vibrating gyroscope, for example, the one shown in FIG. 9 is known. In this vibrating gyro, one side surface 1a of the vibrating body 1 having a square prism shape
And the other side surface 1b adjacent to the side surface 1a.
The vibrator 4 is formed by attaching the piezoelectric elements 3 to the respective elements. The piezoelectric elements 2 and 3 are connected to the output side of the driving device 6 via impedance elements Z ₁ and Z ₂ , respectively. The output side of the driving device 6, also connected to the capacitor C via another impedance element Z _3, thereby the piezoelectric elements 2 and 3
And an AC voltage to the capacitor C at the same time. The outputs of the connection points 5a and 5b of the impedance elements Z ₁ and Z ₂ and the piezoelectric elements 2 and 3 are added by an adder 8, and the output of the adder 8 and the impedance element Z ₃ and the output at the connection point 5c of the capacitive element C are supplied to the differential amplifier 15, and the differential output is fed back to the driving device 6. In addition, connection point 5
The outputs at a and 5b are also supplied to a differential amplifier 16,
The differential output is supplied to the synchronous detector 19 and the driving device 6
Detects in synchronization with the output of In such a vibrating gyroscope, when an AC voltage is applied to the piezoelectric elements 2 and 3 from the driving device 6, the vibrator 4 vibrates in the X-axis direction of the orthogonal three-dimensional coordinate system. In this vibration state, the output obtained from the connection points 5a and 5b is
The supply voltage from the driving device 6 and the respective piezoelectric elements 2
3 is a combined output with the voltage output from each of the piezoelectric elements 2 and 3 in accordance with the distortion 3. Therefore, if the sum of the two combined outputs is obtained by the adder 8 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 15, the oscillation in the X-axis direction can be obtained. Therefore, only the voltage generated from the piezoelectric elements 2 and 3 can be extracted on the basis of the above equation. Therefore, if the differential output is fed back to the driving device 6, the vibrator 4 can be stably self-excited. When the vibrator 4 is rotated around the Z axis while the vibrator 4 is vibrating by itself as described above,
The vibrator 4 is driven by a Coriolis force proportional to its angular velocity.
Vibration in the axial direction causes a difference in output from the connection points 5a and 5b. Therefore, if the difference is obtained by the differential amplifier 16, it is possible to separate and detect the voltage generated due to the generation of the Coriolis force. After detecting the differential output by the synchronous detector 19, it is not shown. If you smooth it with a smoothing circuit,
An angular velocity detection signal can be obtained. In the above-described conventional vibrating gyroscope, in order to obtain a predetermined detection sensitivity with respect to the generated Coriolis force, the X-axis direction and the Y-axis direction in the primary vibration mode are used. The cross-sectional shape of the vibrating body 1 is substantially the same square over the entire length thereof so that the resonance frequencies of the respective bending vibrations are close to or coincide with each other. However, when the resonance frequencies of the bending vibrations in the X-axis direction and the Y-axis direction are brought close to or coincide with each other, the response performance to the change in the input angular velocity, that is, the so-called frequency response performance is poor.
As shown in FIGS. 10A and 10B, examples of the sensitivity characteristic and the phase characteristic show that a significant phase delay occurs at a low frequency, and the sensitivity characteristic also fluctuates. For this reason, accurate angular velocity cannot be detected.
When used for control of traveling or the like, there is a possibility that a sufficient response to the operation of the automobile cannot be made, so that appropriate control becomes impossible. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a vibrating gyroscope appropriately responding to an input angular velocity and always detecting the angular velocity accurately. And In order to achieve the above object, a vibrating gyroscope according to the present invention has at least a pair of piezoelectric elements provided on a side surface of a vibrating body having a resonance point, and has an exciting direction. A vibrator having a resonance frequency different from a resonance frequency in a sensitivity direction intersecting with the excitation direction, a driving unit for self-oscillating the vibrator at the resonance frequency in the excitation direction, a resonance frequency in the excitation direction, A notch filter having a dip point at a difference frequency from a resonance frequency in a sensitivity direction, and a detection unit for detecting an input angular velocity based on vibration of the vibrator in the sensitivity direction. . The self-excited vibration of the vibrator at the resonance frequency in the excitation direction is made different by changing the resonance frequency between the excitation direction of the vibrator and the sensitivity direction crossing the same. Since the target sharpness (Q) is excited at a substantially low level, the vibration in the sensitivity direction rapidly converges,
It responds at high speed to a change in the input angular velocity.
In this case, the detection sensitivity of the input angular velocity is such that the sum or difference between the frequency of the input angular velocity and the resonance frequency in the excitation direction is:
When the resonance frequency coincides with the resonance frequency in the sensitivity direction, the maximum value is shown.However, this variation in the detection sensitivity is caused by the notch having a dip point at the difference frequency between the resonance frequency in the excitation direction and the resonance frequency in the sensitivity direction. By providing a filter, suppression can be achieved. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention.
The vibrator 4 is self-excited and vibrated accurately at the resonance point in the excitation direction (X). As shown in FIG. 9, the vibrator 4 is formed by attaching the piezoelectric elements 2 and 3 to adjacent side surfaces of the vibrating body 1 having a regular square prism shape. In this embodiment, the excitation direction of the vibrator 4 ( X) and the sensitivity direction (Y) are partially or entirely different in the second moment of area, so that the resonance frequency in the excitation direction (X) is different from the resonance frequency in the sensitivity direction (Y). , FIG. 2 (A), (B)
As shown in FIG. 2, a notch 1c is formed on a part of one ridge line, or a notch 1c is formed over the entire ridge line as shown in FIGS. Use something. In FIG. 1, a signal output terminal 9 of a driving device 6 is connected to signal input terminals 11 of feedback amplifiers 10L and 10R.
L, 11R, respectively, and these feedback amplifiers 10
The feedback input terminals 12L and 12R of L and 10R are connected to one electrodes of the piezoelectric elements 2 and 3, respectively. The other electrodes of the piezoelectric elements 2 and 3 are connected via a capacitor Cc to a compensation signal output terminal 13 of a driving device 6 for outputting a compensation signal for the braking capacity of the vibrator 4, thereby allowing the other electrodes of the piezoelectric elements 2 and 3 to be connected. And the compensation signal are synthesized. This synthesized signal is amplified by the summing amplifier 17, and the summing amplifier 17
Is connected to the input terminal 14 of the driving device 6 so that the vibrator 4 is self-excited. The signal at the output terminal 18 of the summing amplifier 17 and the drive signal at the signal output terminal 9 of the driving device 6 are supplied to a differential amplifier 22 for differential amplification. The output is fed to a feedback amplifier 1 via a variable resistor VR for adjusting a subtle difference in equivalent resistance between the piezoelectric elements 2 and 3.
0L and 10R are supplied to the feedback input terminals 12L and 12R, and the feedback input terminals 12L and 12R correspond to the current value flowing through the equivalent resistance of the piezoelectric elements 2 and 3 and correspond to the temperature dependence. To change the current. The outputs of the feedback amplifiers 10L and 10R are supplied to a differential amplifier 20 for differential amplification, and the outputs are supplied to a notch filter 26 via a sample-and-hold circuit 24. To detect the Coriolis force acting on. Here, the sample and hold circuit 24 is configured to sample and hold the output of the differential amplifier 20 in synchronization with the drive signal of the drive device 6, and the notch filter 26 controls the resonance of the vibrator 4 in the excitation direction. It is configured to have a dip point at the difference frequency between the frequency and the resonance frequency in the sensitivity direction. FIG. 3 shows the compensation signal output terminal 13 shown in FIG.
1 shows a configuration of an example of a driving device 6 having the following. The driving device 6 includes a non-inverting amplifier 15 and an inverting amplifier 1.
And a non-inverting amplifier 15
The output is supplied to the compensation signal output terminal 13 as a compensation signal, and is also amplified by the inverting amplifier 16 and supplied to the signal output terminal 9 as a drive signal. That is, in the driving device 6, the phase of the driving signal supplied to the signal output terminal 9 and the phase of the compensation signal supplied to the compensation signal output terminal 13 are changed by 180 °, and the amplitude ratio of those signals is changed by an inverting amplifier. 16 is set appropriately. In the vibrating gyroscope shown in FIG. 1, among the current components flowing through the piezoelectric elements 2 and 3, the imaginary components related to the respective braking capacities are canceled by the compensation signal synthesized via the capacitor Cc. The output of 17 is only a real component of the current components flowing through the piezoelectric elements 2 and 3. Therefore, the voltage gain of the summing amplifier 17 becomes maximum at the mechanical series resonance frequency fs of the vibrator 4, and the vibrator 4 is moved to its mechanical series resonance frequency fs.
Self-excited vibration can be stably performed in the excitation direction (X) at a frequency exactly matching the following. The self-excited oscillation in the excitation direction at the mechanical series resonance frequency fs is caused by the capacitor Cc
By using a material having a temperature dependency corresponding to the temperature dependency of the braking capacity of the vibrator 4, the stability can be further improved. Here, the excitation direction (X) and the sensitivity direction (Y)
The response characteristic due to the difference between the respective resonance frequencies will be described. FIG. 4 is a graph showing a value (interval between resonance frequencies) Δf obtained by subtracting the resonance frequency in the excitation direction from the resonance frequency in the sensitivity direction.
The relationship between the output of the sample and hold circuit 24 and the frequency fφ of the input angular velocity that is delayed by 90 ° in phase angle with respect to the frequency of the input angular velocity in a state where the vibrator 4 is self-excited at the resonance frequency in the excitation direction. Also, FIG.
The relationship between the resonance frequency interval Δf and the frequency f _{G of the} input angular velocity at which the output of the sample and hold circuit 24 has a maximum is shown. As is apparent from FIGS. 4 and 5, Δf
There is also a case of either positive or negative, fφ ≒ | Δf | and f _G ≒ | Δf | become. Therefore, if the response characteristic of the vibration gyro is set to allow a delay of 90 °, any one of the positive and negative Δ
It can be seen that f should be set. In FIG. 1, when the vibrator 4 set to Δf = 100 Hz is used, the sensitivity characteristics and phase characteristics of the output of the sample hold circuit 24 are as shown in FIGS. 6A and 6B. In this case, since the notch filter 26 has the dip point set to Δf = 100 Hz, the sensitivity characteristic and the phase characteristic of the output are as shown in FIG.
(A) and (B) are obtained. That is, in the sample and hold circuit 24, the phase characteristic is 100H
It becomes almost flat up to the vicinity of z, and the sensitivity characteristic shows a maximum value at 100 Hz. However, the fluctuation of the sensitivity near 100 Hz is effectively suppressed by the notch filter 26 in the subsequent stage. Moreover, as is apparent from FIGS. 7A and 7B, at an input angular velocity of 10 Hz, the detection sensitivity is -1.6.
dB and the phase delay are 45 °, and good response characteristics are obtained. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified or changed. For example, a synchronous detection circuit may be used in place of the sample and hold circuit 24, whereby the output of the differential amplifier 20 is detected in synchronization with the drive signal and supplied to the notch filter 26. Also, the vibrating body 1 is shown in FIG.
Not only the notch 1c formed over a part or the whole of one ridge of the quadrangular cross section shown in FIGS. 8A to 8D but also a triangular cross section as shown in FIG. A notch 1c is formed on a part of one ridge line of the shape, or a notch portion 1c is formed over the entire ridge line having a triangular cross section as shown in FIG. It can also be used. As described above, according to the present invention, the resonance frequency between the excitation direction and the sensitivity direction of the vibrator is made different,
The vibrator is self-excited at the resonance frequency in the excitation direction, and the detection means is provided with a notch filter having a dip point at the difference frequency between the resonance direction in the excitation direction and the sensitivity direction. In addition, fluctuations in detection sensitivity due to different resonance frequencies can be effectively suppressed,
The angular velocity can always be detected accurately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a view showing four examples of a vibrating body shown in FIG. 1; FIG. 3 is a block diagram illustrating a configuration of an example of a driving device. FIG. 4 is a diagram showing the relationship between the resonance frequency difference between the excitation direction and the sensitivity direction in which the phase angle of the output of the sample and hold circuit is delayed by 90 ° and the frequency of the input angular velocity in FIG. FIG. 5 is a diagram showing a relationship between a resonance frequency difference at which the output of the sample hold circuit indicates a maximum and the frequency of the input angular velocity. FIG. 6 is a diagram showing a resonance frequency difference Δf = 100 Hz in FIG.
FIG. 9 is a diagram illustrating response characteristics of the output of the sample-hold circuit in the case of FIG. FIG. 7 is a diagram showing a response characteristic of an output of the notch filter. FIG. 8 is a diagram showing another two examples of the vibrating body usable in the present invention. FIG. 9 is a block diagram showing a conventional vibrating gyroscope. FIG. 10 is a diagram showing response characteristics of the vibrating gyroscope shown in FIG. 9; [Description of Signs] 1 Vibration body 1c Notch 2, 3 Piezoelectric element 4 Vibrator 6 Driver 10L, 10R Feedback amplifier 17 Summation amplifier 20 Differential amplifier 24 Sample hold circuit 26 Notch filter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04

Claims (1)

(57) [Claims 1] Provided on a side surface of a vibrating body having a resonance point,
A vibrator having at least substantially a pair of piezoelectric elements and having different resonance frequencies in an excitation direction and resonance frequencies in a sensitivity direction crossing the excitation direction; and causing the vibrator to self-oscillate at the resonance frequency in the excitation direction. A driving unit, comprising: a notch filter having a dip point at a difference frequency between a resonance frequency in the excitation direction and a resonance frequency in the sensitivity direction, and detecting an input angular velocity based on vibration of the vibrator in the sensitivity direction. And a vibrating gyroscope.