JPH09203639A - Angular velocity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an angular velocity accurately all the time even if there are dispersion in parts and temperature change. SOLUTION: Driving piezoelectric elements 14a and 14b, monitoring piezoelectric elements 15a and 15b and a self-oscillation circuit 30 vibrate a tuning-fork type vibrator in the orthogonal direction with respect to the axial direction of the vibrator at a natural frequency and at a constant amplitude. Detecting piezoelectric elements 16a and 16b detect the vibration caused by Coriolis force, which is in proportion to the angular velocity around the axial line of the tuning-fork type vibrator. A bandpass filter circuit 50 is composed of a switched- capacitance filter and extracts and outputs only the frequency component in the vicinity of the natural frequency among the frequency components contained in the detected signal. A phase-locked loop circuit 40 inputs the electric signal having the frequency equal to the natural frequency from the self-oscillation circuit 30, multiplies the frequency of this signal and controls the central frequency of the band-pass filter circuit 50 to the natural frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity detecting device for detecting an angular velocity of an object using a vibrator having a natural frequency.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No.
As shown in Japanese Patent Publication No. 172711, a tuning fork type oscillator having a natural frequency is vibrated at a natural frequency in a first direction orthogonal to the axial direction and is rotated at an angular velocity around the axial line. And the oscillator causes the Coriolis force of a magnitude proportional to the angular velocity to cause the axial direction and the first
Using the principle of vibrating at the natural frequency in the second direction orthogonal to both directions, the vibration of the vibrator in the second direction is extracted as an electric signal and vibrated according to the magnitude of the amplitude value of the extracted electric signal. The angular velocity around the axis of the object with the child fixed is detected. Further, in this conventional device, the extracted electric signal is passed through a bandpass filter whose center frequency is matched with the natural frequency of the vibrator, and the noise component contained in the extracted electric signal is removed, The detection accuracy of the angular velocity is improved.

[0003]

However, in the above-mentioned conventional device, the natural frequency of the vibrator and the bandpass filter are changed due to environmental changes such as variations in parts of the vibrator and the bandpass filter and temperature changes. There is a problem in that there is a deviation from the center frequency and the amplitude of the electric signal that has passed through the bandpass filter fluctuates, which deteriorates the detection accuracy of the angular velocity.

[0004]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of always detecting an angular velocity with high accuracy, and the structural feature thereof is the vibration of a vibrator generated by Coriolis force. The center frequency of the bandpass filter for passing the electric signal is variable, and the filter control means for controlling the center frequency of the bandpass filter to match the natural frequency of the vibrator is provided.

[0005]

According to the present invention configured as described above, since the filter control means controls the center frequency of the bandpass filter to match the natural frequency of the vibrator, the vibrator or the bandpass filter is controlled. The center frequency of the bandpass filter and the natural frequency of the oscillator always match, even if the filter components vary or the environment changes such as temperature changes, and the electrical signal that represents the angular velocity of the object with the oscillator fixed is It is always taken out with high accuracy, and the same angular velocity can always be detected with high accuracy.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a tuning fork type vibrator 10 which constitutes an angular velocity detecting device according to the embodiment.

The tuning fork type vibrator 10 is provided with a pair of vibrating pieces 12 and 13 which are erected in parallel on a base 11 fixed to an object whose angular velocity is detected. Driving piezoelectric elements 14a and 14b and monitoring piezoelectric elements 15a and 15b are fixed to the lower portions of the vibrating bars 12 and 13, respectively. The driving piezoelectric elements 14a and 14b have a function of exciting the vibrating bars 12 and 13 in the X-axis direction, and the monitoring piezoelectric elements 15a and 15b.
b has a function of detecting the vibration of the vibrating bars 12 and 13 in the X-axis direction and extracting an electric signal representing the vibration. In addition, the piezoelectric elements 16a and 16b for detection are provided above the vibrating pieces 12 and 13.
Are fixed to each other, and the elements 16a and 16b function as electric signal extracting means for detecting the vibration of the vibrating pieces 12 and 13 in the Y-axis direction and extracting the vibration as an electric signal. The X axis and the Y axis are orthogonal to each other, and are also orthogonal to the Z axis, which is the direction of the axis L1 of the tuning fork vibrator 10.

As shown in FIG. 2, the driving piezoelectric element 14 is used.
a, 14b and the piezoelectric elements 15a, 15b for monitoring include a buffer amplifier 2 in a self-exciting circuit 30 which constitutes self-exciting means together with these elements 14a, 14b, 15a, 15b.
They are connected via 1 and 22 respectively. This self-exciting circuit 30 is connected to a phase locked loop circuit (filter control means) 40 via a buffer amplifier 23. The detection piezoelectric elements 16 a and 16 b are connected to the bandpass filter circuit 50 via the buffer amplifiers 24 and 25 and the differential amplifier circuit 26.

The self-exciting circuit 30 includes the driving piezoelectric element 14.
A drive signal is supplied to a and 14b to move the vibrating bars 12 and 13 to X.
It is excited in the axial direction and includes a multiplier 31, a low-pass filter 32, an inverting amplifier 33, and a voltage control type amplifier 34. The multiplier 31 is the monitoring piezoelectric element 15a, 1
In order to rectify the electric signal from 5b, the electric signal is squared and output, and the low-pass filter 32 integrates the electric signal from the multiplier 31. As a result, a voltage signal representing the amplitude of vibration of the vibrating bars 12 and 13 in the X-axis direction is obtained. The inverting amplifier 33 outputs a voltage signal that is substantially inversely proportional to the voltage signal from the low-pass filter 32, and the voltage control type amplifier 34 calculates the gain of the electric signal input from the monitoring piezoelectric elements 15a and 15b by the voltage signal from the inverting amplifier 33. Output to the driving piezoelectric elements 14a and 14b.
As a result, the vibrating bars 12 and 13 continue to vibrate in the X-axis direction at the constant amplitude and at the natural frequency of the tuning fork vibrator 10.

The phase-locked loop circuit (filter control means) 40 constitutes a multiplication circuit for multiplying and outputting the natural frequency of the tuning fork type oscillator 10, and includes a voltage controlled oscillator 41, a frequency divider 42, and a phase. It comprises a comparator 43 and a low-pass filter 44. The phase comparator 43 includes a self-exciting circuit 3
An electric signal having a frequency equal to the natural frequency of the tuning fork vibrator 10 is input from 0, and a clock signal having a frequency obtained by multiplying the frequency of the electric signal by a predetermined number is output from the voltage controlled oscillator 41.

The bandpass filter circuit 50 extracts only the frequency components near the natural frequency of the tuning fork type vibrator 10 among the frequency components included in the electric signals extracted by the detecting piezoelectric elements 16a and 16b. is there. The bandpass filter circuit 50 includes capacitors C1 to C6,
Operational amplifiers OP1 and OP2 and switching circuit SW1
.. to SW3, which is a switched capacitance filter whose center frequency is variable, the switching circuits SW1 to SW3 are switched according to the high / low level of the clock signal supplied from the voltage controlled oscillator 41, It has a function of changing the center frequency of the bandpass filter circuit 50 according to the frequency of the same clock signal. In this case, when the switching circuits SW1 to SW3 are switched by the clock signal having a frequency obtained by multiplying the natural frequency of the tuning fork type vibrator 10 by the predetermined number, the center frequency of the bandpass filter circuit 50 becomes the natural frequency. It has been adjusted to be equal.

An amplitude detection circuit 60 is connected to the output of the bandpass filter circuit 50. The circuit 60 detects the amplitude value of an electric signal representing vibration in the Y-axis direction from the bandpass filter circuit 50 and outputs the same. It outputs a signal that represents the amplitude value.

In the angular velocity detecting device constructed as described above, by the action of the driving piezoelectric elements 14a, 14b, the monitoring piezoelectric elements 15a, 15b and the self-exciting circuit 30,
The vibrating pieces 12 and 13 vibrate in the X-axis direction at the natural frequency of the tuning fork type vibrator 10. In this case, the vibration amplitudes of the vibrating bars 12 and 13 are controlled to be substantially constant by the self-exciting circuit 30. In this state, when the fixed object on the base 11 rotates about the axis L1 (Z axis) of the tuning fork type vibrator 10, the Coriolis force proportional to the angular velocity of the rotation causes Y of the vibrating bars 12, 13.
The vibration pieces 12 and 13 are generated in the axial direction and vibrate in the Y-axis direction. In this case, the frequency of vibration of the vibrating bars 12 and 13 is equal to the natural frequency of the tuning fork type vibrator 10, and the amplitude of the vibration is proportional to the rotational angular velocity of the object.

The vibrations of the vibrating bars 12 and 13 in the Y-axis direction are detected by the detecting piezoelectric elements 16a and 16b, taken out as electric signals, and supplied to the bandpass filter circuit 50. On the other hand, the voltage controlled oscillator 41 outputs a clock signal having a frequency obtained by multiplying the natural frequency of the tuning fork vibrator 10 by the predetermined number, and the center frequency of the bandpass filter circuit 50 is the natural frequency by the clock signal. Since the frequency is controlled to be equal to the frequency, the electric signal representing the vibration of the vibrating bars 12 and 13 in the Y-axis direction is amplified through the bandpass filter circuit 50 having the center frequency equal to the natural frequency of the tuning fork vibrator 10. It is output to the detection circuit 60. Then, in the amplitude detection circuit 60, the resonator element 1
Since the amplitude values of the electric signals 2 and 13 representing the vibration in the Y-axis direction are detected, the angular velocity about the axis L1 (Z axis) of the object to which the tuning fork type vibrator 10 is fixed is detected as the amplitude value.

In this case, the self-exciting circuit 30 includes the resonator element 12,
It acts so as to always excite 13 with a constant amplitude. Also, a phase locked loop circuit (filter control means)
40 controls the center frequency of the bandpass filter circuit 50 so as to match the natural frequency of the tuning fork type oscillator 10, so that the tuning fork type oscillator 10 or the bandpass filter circuit 4 is controlled.
0 capacitors C1 to C6, operational amplifiers OP1 and OP2
Even if there is a variation in manufacturing accuracy, such as when there is a change in the environment such as a temperature change, the center frequency of the bandpass filter circuit 50 and the natural frequency of the tuning fork vibrator 10 always match.
The electric signal representing the angular velocity of the object to which the tuning fork type vibrator 10 is fixed is always taken out with high precision, and the same angular velocity can always be detected with high precision.

Further, in the above embodiment, since the bandpass filter circuit 50 is constituted by the switched capacitance filter, the filter circuit 50 can be easily integrated into a circuit and the circuit portion of the angular velocity detecting device can be made small. As a result, mass production becomes easier. Then, in order to obtain a clock signal for controlling the center frequency of the bandpass filter circuit 50 to be equal to the natural frequency of the tuning fork type vibrator 10 and having a frequency at least higher than the natural frequency, Using the locked loop circuit 40, the circuit 40 transmits an electric signal having a frequency equal to the same natural frequency to the tuning fork vibrator 10
Since the frequency of the input electric signal is multiplied while being input from the self-exciting circuit 30, the center frequency of the bandpass filter circuit 50 can be accurately controlled to be equal to the natural frequency of the tuning fork vibrator 10.

In the above embodiment, the vibrating pieces 12, 13 of the tuning fork type vibrator 10 are excited in the X axis direction by the driving piezoelectric elements 14a, 14b, and the vibrating pieces 12, 13 are moved in the X axis direction and Each vibration in the Y-axis direction is monitored by the piezoelectric elements 15a and 15b for monitoring and the piezoelectric element 16a for detection.
Each of them was detected by 16b and extracted as an electric signal. However, as shown in FIG.
The device itself may be made of a piezoelectric material such as quartz. In this case, the tuning fork type vibrator 70 is formed by using a piezoelectric element.
The vibrating pieces 72, 73 of
Since it is not necessary to convert the vibration of 3 into an electric signal,
Instead of the two driving piezoelectric elements 14a and 14b of the above embodiment, two sets of driving electrodes 74a1, 74a2 and 74b1 for exciting the vibrating pieces 72 and 73 in the X-axis direction,
The tuning fork type vibrator 70 may be provided with 74b2. In addition, the two monitoring piezoelectric elements 15 of the above-described embodiment.
Instead of a and 15b, two sets of monitor electrodes 75a1, 75a2 and 75b1, 75b2 as electric signal extracting means for extracting the vibrations of the vibrating bars 72, 73 in the X-axis direction as electric signals are tuned fork type vibrations. It may be provided on the child 70. Further, in place of the pair of detection piezoelectric elements 16a and 16b of the above-described embodiment, Y of the vibrating pieces 72 and 73 is used.
A pair of detection electrodes 76a and 76b may be provided in the tuning fork vibrator 70 as an electric signal extracting means for extracting the vibration in the axial direction as an electric signal.

In this case, two sets of driving electrodes 74 are used.
Of a1, 74a2 and 74b1, 74b2, one electrode of each set is grounded, and the other electrode of each set is connected to the buffer amplifier 21 instead of the detection piezoelectric elements 14a and 14b of FIG. You can do it like this. Also, two sets of monitor electrodes 75a1, 75a2 and 75b
If one of the electrodes of each set of 1,75b2 is grounded and the other electrode of each set is connected to the buffer amplifier 22 instead of the monitoring piezoelectric elements 15a and 15b of FIG. Good. Further, the pair of detection electrodes 76a and 76b are connected to the pair of detection piezoelectric elements 16 shown in FIG.
The buffer amplifiers 24 and 25 may be connected to the buffer amplifiers a and 16b, respectively. In the modified example configured in this manner, the tuning fork type vibrator 70 can be operated in the same manner as the above-described embodiment and the same effect can be expected.
Since the device itself can be configured to be small, the entire angular velocity detection device can be configured to be compact.

Further, in the above-described embodiments and modifications, the electric signals converted by the monitoring piezoelectric elements 15a, 15b and the monitoring electrodes 75a1, 75a2, 75b1, 75b2 are input to the self-exciting circuit 30 and the filter control means is provided. Phase locked loop circuit 40
I also tried to enter. However, the monitoring piezoelectric element (or the monitoring electrode) for the self-excitation circuit 30 and the monitoring piezoelectric element (or the monitoring electrode) for the phase-locked loop circuit 40 are separately provided, and each monitoring piezoelectric element is provided. Each electric signal converted by the element (or each electrode) may be supplied to the self-excitation circuit 30 and the phase-locked loop circuit 40, respectively.

Further, in the above-described embodiments and modifications, the driving piezoelectric element and the pair of driving electrodes, and the monitoring piezoelectric element and the pair of monitoring electrodes are provided in two sets each, but it is sufficiently large. When the vibration and the electric signal are obtained, the driving piezoelectric element and the pair of driving electrodes, and the monitoring piezoelectric element and the pair of monitoring electrodes may be provided one each.

Further, in the above-described embodiment and its modification, the tuning fork type vibrator has been described as an example of the vibrator having a natural frequency, but the vibrator is not limited to the tuning fork type, but is H type, etc. Various vibrators in the form of can be used.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a tuning fork type vibrator according to an embodiment of an angular velocity detecting device of the present invention.

FIG. 2 is a block diagram of a circuit portion according to an embodiment of the angular velocity detecting device.

FIG. 3 is a schematic perspective view of a tuning fork type vibrator according to a modified example of the same embodiment.

[Explanation of symbols]

10 ... Tuning fork type vibrator, 12, 13 ... Vibrating piece, 14a, 1
4b ... Piezoelectric element for driving, 15a, 15b ... Piezoelectric element for monitor, 16a, 16b ... Piezoelectric element for detection, 30 ... Self-exciting circuit, 40 ... Phase locked loop circuit, 50 ... Bandpass filter circuit, 60 ... Amplitude detecting circuit , 70 ... Tuning fork type vibrator, 72, 73 ... Vibrating piece, 74a1, 74a
2, 74b1, 74b2 ... Driving electrodes, 75a1, 75
a2, 75b1, 75b2 ... Monitor electrodes, 76a, 7
6b ... Detection electrode.

Claims (1)

[Claims] 1. A vibrator having a predetermined natural frequency, self-exciting means for vibrating the vibrator at a natural frequency in a first direction orthogonal to the uniaxial direction, the uniaxial direction and the first direction. Electric signal extracting means for extracting the vibration of the vibrator in the second direction orthogonal to the two directions as an electric signal, and a frequency component included in the extracted electric signal connected to the electric signal extracting means. In the angular velocity detection device comprising a bandpass filter for extracting only frequency components in the vicinity of the natural frequency, and detecting the angular velocity around the uniaxial line based on the output signal of the bandpass filter, the bandpass filter A filter that configures the center frequency variably and controls the center frequency of the bandpass filter to match the natural frequency of the oscillator. Angular velocity detecting apparatus characterized in that a control means.