JPH04297874A - Angular velocity sensor driver - Google Patents

Abstract

PURPOSE:To obtain a driver which is so arranged to cancel a drive signal component to be mixed into an input signal of an amplifier in a tuning fork type angular velocity sensor. CONSTITUTION:This apparatus has a tuning fork structure type angular velocity sensor 9, a phase inversion amplifier 10 which is connected so that an input signal is inputted from a piezo-electric element for driving of the sensor while an output signal is outputted to the piezo-electric element for driving again to invert the phase of a drive voltage by 180 deg., an amplifier 5 which uses an electric charge generated in a piezo-electric element for detection as input signal while an output signal thereof is picked up to obtain an angular velocity and a variable resistor 12 which is connected between the input side and the output side of the phase inversion amplifier 10 while a slide element is connected on the input side of the amplifier 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration type angular velocity sensor drive device in which a ceramic piezoelectric element is bonded to a tuning fork structure.

0002

[Background Art] In recent years, angular velocity sensors that can detect angular velocity have been put into practical use. For example, an angular velocity sensor is attached to a video camera, and the shaking of the shooting screen due to camera shake is corrected by changing the lens position using the output of the angular velocity sensor. etc. have been put into practical use. In particular, a vibrating angular velocity sensor in which a piezoelectric element is bonded to a tuning fork structure has excellent response speed and sensitivity, and is expected to be widely used in the future.

A conventional vibration type angular velocity sensor driving device will be explained based on the drawings. FIG. 6 is a circuit block diagram showing the configuration of a conventional vibration type angular velocity sensor drive device.
A driving section consisting of a first amplifier 1, a rectifier 2, a smoothing circuit 3, a second amplifier 4, and a third amplifier 5,
It consists of a detection section composed of a synchronous detector 6 and a low-pass filter 7, and is connected to a tuning fork structure vibration type angular velocity sensor 9. Next, the mutually related operations of the constituent elements will be explained.

The tuning fork structure vibration type angular velocity sensor 9 includes a first amplifier 1, a rectifier 2 that rectifies the output charge of the first amplifier 1, and a smoothing circuit 3 that smoothes the output voltage of the rectifier 2.
and a second amplifier 4 whose amplification degree for amplifying the output voltage from the first amplifier 1 changes depending on the output voltage value of the smoothing circuit 3, and the tuning fork vibrates under constant amplitude control. When angular velocity is applied to the tuning fork structure vibration type angular velocity sensor 9, the angular velocity signal is amplified and phase shifted by the third amplifier 5,
The signal is detected by a synchronous detector 6, smoothed and amplified by a low-pass filter 7, and output.

In the angular velocity sensor driving device of the present invention having the above configuration, when the angular velocity sensor is first driven, the first and second detection piezoelectric elements are orthogonal to the monitoring piezoelectric element or the driving piezoelectric element that vibrates like a tuning fork. Therefore, in principle, no charge is generated on the surface electrode unless an angular velocity signal is applied.

[0006]

[Problems to be Solved by the Invention] However, in conventional vibration type angular velocity sensor drive devices, due to variations in the structure of the sensor, the drive signal for causing the sensor to vibrate in a tuning fork mixes with the charge generated on the surface electrode of the detection piezoelectric element. . For this reason, this leakage signal is generally excluded by synchronous detection matched to the vibration frequency of the tuning fork structure, and only the angular velocity signal is output. However, the above leakage signal may be more than 100 times the original angular velocity signal. Furthermore, there are problems in that the output voltage fluctuates due to temperature changes, and the output voltage of the amplifier saturates, making it impossible to obtain a sufficient degree of amplification.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention aims to promote an angular velocity sensor drive device having a function of canceling drive signal components mixed into an input signal of an amplifier.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a drive piezoelectric element, a detection piezoelectric element, and a drive piezoelectric element and a detection piezoelectric element so that their vibration directions are perpendicular to each other. an angular velocity sensor comprising a first joining member that stacks up and joins the elements, and a second joining member that joins the pair of joined elements to a tuning fork structure, and a signal from the one driving piezoelectric element is inputted. a phase inversion amplifier that is connected to output the output signal to the other drive piezoelectric element and inverts the phase of the drive voltage by 180°;
an amplifier that uses the charge generated on the surface electrode of the detection piezoelectric element as an input signal and obtains an angular velocity signal by extracting the output signal; and an amplifier that is connected between the input terminal and the output terminal of the phase inversion amplifier; The slider has a variable resistor connected to the input terminal of the amplifier.

[0009]

According to the present invention, a drive signal or a signal whose phase is inverted by 180 degrees from the drive signal can be mixed into the output signal via the variable resistor, thereby canceling out and reducing leakage signals.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an angular velocity sensor driving device according to the present invention will be described below with reference to the drawings.

First, a tuning fork structure vibration type angular velocity sensor will be explained with reference to FIGS. 3 to 5. The angular velocity sensor has a structure as shown in FIG. The first joint is orthogonally joined at the joint part 105 which is the first joint member.
The vibration unit 109 and the second vibration unit 110 in which the monitor element 102 and the second detection element 104 are orthogonally joined at the joint part 106 are connected to the connecting plate 10 which is the second joint member.
7, and this connecting plate 107 is supported at one point by a support rod 108 to form a tuning fork structure.

When a sinusoidal voltage signal is applied to the drive element 101, the first vibration unit 109 starts to vibrate due to the inverse piezoelectric effect, and the second vibration unit 110 also starts to vibrate due to the tuning fork vibration. Therefore, the charge generated on the surface of the monitor element 102 due to the piezoelectric effect is proportional to the sinusoidal voltage signal applied to the drive element 101. By detecting the charge generated in the monitor element 102 and controlling the sinusoidal voltage signal applied to the drive element 101 so that the charge has a constant amplitude, stable tuning fork vibration can be obtained. Note that the monitor element 102 is vibrated as a second drive element when constant amplitude control is not required. The mechanism by which this sensor generates an output proportional to angular velocity will be explained using FIGS. 4 and 5.

FIG. 4 shows the angular velocity sensor shown in FIG. 3 viewed from above. When rotation at an angular velocity ω is applied to the sensing element 103, which is vibrating at a velocity v, a "Coriolis force" is applied to the sensing element 103. arise. This "Coriolis force" is perpendicular to the velocity v and has a magnitude of 2 mvω (m is the equivalent mass of the tip of the sensing element 103). Since the sensing element 103 is vibrating like a tuning fork, if the sensing element 103 is vibrating at a speed v at a certain point, the sensing element 104 is vibrating at a speed v, and the "Coriolis force" is -2mvω. be. Therefore, the sensing elements 103 and 104 are deformed toward each other in the direction of the "Coriolis force" as shown in FIG. 5, and charges are generated on the surfaces of the elements due to the piezoelectric effect. Here, v is the motion caused by the tuning fork vibration, and if the tuning fork vibration is This becomes a force that deforms 103 and 104 in the plane direction. Therefore, the amount of surface charge Q of the sensing elements 103 and 104 is Q
∝a=a・ω・sinω0t, and if the tuning fork amplitude a is controlled to be constant, then Q∝ω・sinω0t, which is the amount of surface charge Q generated on the sensing elements 103 and 104.
is obtained as an output proportional to the angular velocity ω, and this signal is expressed as ω
If synchronous detection is performed at 0t, a DC signal proportional to the angular velocity ω can be obtained. Note that even if a translational motion other than angular velocity is applied to this sensor, charges of the same polarity are generated on the surfaces of the two sensing elements 103 and 104, so when converting to a DC signal,
Since they cancel each other out and no output is produced, the piezoelectric bimorph element has been described, but it goes without saying that a general piezoelectric element can have the same function.

FIG. 1 shows one embodiment of the present invention, and parts having the same functions as those of the conventional example are denoted by the same reference numerals and explanations thereof will be omitted.

Reference numeral 10 denotes a phase inversion amplifier, which is connected to the output side of the first amplifier 1. This phase inversion amplifier 1
0, it is possible to obtain a signal whose phase is inverted by 180 degrees from the drive signal for causing the tuning fork structure vibration type angular velocity sensor 9 to vibrate. A variable resistor 11 is connected between the input side and the output side of the phase inversion amplifier 10, and the slider of this variable resistor 11 is connected to the input side of the third amplifier 5 via the resistor 12. connected. With this configuration, an appropriate value of the input signal or output signal of the phase inversion amplifier 10 can be mixed into the input side of the third amplifier 5.

FIGS. 2(a), 2(b), and 2(c) are waveform diagrams illustrating the operation of this embodiment. The solid line in Figure 2(a) is shown in Figure 1.
The input signal of the phase inversion amplifier 10 is shown, and the broken line shows the output signal of the same amplifier. These signals are sine waves whose frequency is the same as the tuning fork vibration frequency of the angular velocity sensor, as described above.

FIG. 2(b) shows theoretical values of charges generated in the sensing element 103 and the sensing element 104 when an angular velocity is applied. This waveform has the same frequency as Fig. 2(a) and a phase of 90
The amplitude is proportional to the applied angular velocity, as explained by the Coriolis force principle described above. However, in reality, due to variations in the materials constituting the sensor and assembly errors, the waveform generated in the sensing element 103 or 104 differs from that in FIG. 2(b), as shown by the solid line in FIG. 2(c). Although the waveform is obtained by adding the drive voltage, either the drive voltage is added by appropriately sliding the variable resistor 11, or a voltage with the opposite phase to the drive voltage is added. This is determined by whether the orthogonality accuracy between the detection element 104 and the monitor element 102 and the orthogonality accuracy between the detection element 103 and the driving element 101 deviate from 90° to the plus side or to the minus side. variable resistance 1
1, the waveform in Fig. 2(a) is changed from the waveform in Fig. 2(c).
An appropriate amount of voltage is added as shown by the broken solid line or the waveform shown by the broken line. As a result, the drive signal component can be removed from the waveform of FIG. 2(c), and the waveform can be approximated to an ideal waveform as shown in FIG. 2(b).

As is clear from the above description, the angular velocity sensor drive device of this embodiment can remove leakage components of the drive signal caused by sensor variations. Therefore, fluctuations in the output voltage due to temperature changes caused by the response speed of the synchronous detection circuit are reduced. Another advantage is that the low-pass filter can be simplified.

[0019]

As described above, according to the present invention, a drive signal or a signal whose phase is 180° inverted from the drive signal can be mixed into the output signal through the variable resistor, thereby canceling out and reducing leakage signals. can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the angular velocity sensor driving device of the present invention.

[Figure 2] Waveform diagram for explaining the operation of the same embodiment

[Figure 3
] Perspective view of tuning fork structure vibration type angular velocity sensor

[Figure 4] Diagram explaining the operation of the sensor

[Figure 5] Diagram explaining the operation of the sensor

[Figure 6] Block diagram of a conventional angular velocity sensor drive device

[Explanation of symbols]

1 First amplifier 2 Rectifier 3 Smoothing circuit 4 Second amplifier 5 Third amplifier 6 Synchronous detector 7 Low pass filter 9 Tuning fork structure vibration type angular velocity sensor 10 Phase inversion amplifier 11 Variable resistor 12 Resistor

Claims (1)

[Claims] 1. A driving piezoelectric element, a sensing piezoelectric element, a first joining member for stacking and joining the driving piezoelectric element and the sensing piezoelectric element so that their vibration directions are perpendicular to each other, and the joined element. an angular velocity sensor equipped with a second joining member that joins the pair to a tuning fork structure; and a connection so that a signal from the one driving piezoelectric element is input and an output signal is output to the other driving piezoelectric element. and a phase inversion amplifier that inverts the phase of the drive voltage by 180 degrees; an amplifier that uses the charge generated on the surface electrode of the detection piezoelectric element as an input signal and obtains an angular velocity signal by extracting the output signal; An angular velocity sensor driving device comprising: a variable resistor connected between an input terminal and an output terminal of an inverting amplifier, and a variable resistor having a slider connected to the input terminal of the amplifier.