JPH0348714A - Angular velocity sensor driving circuit - Google Patents

Abstract

PURPOSE:To prevent the sensitivity of an angular velocity sensor from being affected by temperature variation by making the amplitude quantity of tuning-fork vibration proportional to the sensor sensitivity and varying the amplitude quantity with temperature according to the temperature variation of the sensitivity. CONSTITUTION:Charges induced at the electrodes of a piezoelectric bimorph element 102 for a motor are amplified 1, rectified 2, and smoothed 3 to become a DC voltage which is proportional to the amplitude of the tuning fork vibration. An amplifier 4 amplifies the output voltage of the amplifier 1 to drive a piezoelectric bimorph element 101 for driving. Then when the amplitude of the tuning force vibration increases, the charges induced at the electrodes of the elements 102 increase, the output voltage amplitude of the amplifier 1 increases, and the amplitude of the voltage applied to the element 101 decreases, so that the amplitude of the tuning fork vibration is held at a constant value. A temperature dependent resistor 14 increases in resistance value as the ambient temperature rises and the amplifier 1 decreases in amplification degree as the temperature rises. Therefore, the vibration of the tuning fork vibration becomes small in amplitude as the temperature rises and becomes large in amplitude when the temperature falls. Thus, temperature characteristics of the sensitivity which are a problem characteristic to the tuning fork structure vibration type angular velocity sensor can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive circuit for a vibrating angular velocity sensor in which a ceramic piezoelectric element is formed into a tuning fork structure. The present invention relates to a drive circuit.

2. Description of the Related Art A conventional angular velocity sensor drive circuit will be described with reference to the drawings. FIG. 2 is a circuit block diagram showing the configuration of a conventional angular velocity sensor drive circuit, in which 1 is a first amplifier, 2 is a rectifier, 3 is a smoothing circuit, 4 is a second amplifier, 5 is a third amplifier, 6 is a synchronous detector, 7 is a fourth amplifier, and 9 is a tuning fork structure vibration type angular velocity sensor.

The tuning fork structure vibration type angular velocity sensor 9 includes a first amplifier 1 and
A rectifier 2 that rectifies the output charge of the first amplifier 1, a smoothing circuit 3 that smoothes the output voltage of the rectifier 2, and an amplifier that amplifies the output voltage from the first amplifier 1 based on the output voltage value of the smoothing circuit 3. The tuning fork vibrates while being controlled to a constant field of view by a fourth amplifier whose intensity changes. When the angular velocity is added to the tuning fork structure imaging type angular velocity sensor 91, the angular velocity signal becomes the third one.
The signal is amplified and phase shifted by an amplifier 5, detected by a synchronous detector 6, and further smoothed by a fourth amplifier 7.

It is amplified and output.

FIG. 3 is a sectional view of a piezoelectric bimorph element used in the tuning fork structure vibration type angular velocity sensor 9.

In FIG. 3, 10 is an electrode material, 11 is a piezoelectric element, 12 is an intermediate electrode plate, and 13 is an adhesive for bonding the piezoelectric element 11 and the intermediate electrode plate 12 together.

Problem to be Solved by the Invention However, in the tuning fork structure vibrating angular velocity sensor 9, there is a problem in that the sensitivity of the output voltage to the angular velocity is affected by the temperature characteristics of the materials of each part used in the sensor itself. . For example, regarding each material constituting the piezoelectric bimorph element shown in FIG. 3, the temperature characteristics of the sensitivity of the piezoelectric element 11, the temperature characteristics of the spring elasticity of the intermediate electrode plate 12, the temperature characteristics of the hardness after bonding of the adhesive 12, etc. A large number of factors are involved, and it is difficult to select a combination of materials such that the temperature characteristic of the sensitivity of the output voltage to the angular velocity is O. An object of the present invention is to provide an angular velocity sensor drive circuit whose angular velocity sensor sensitivity is not affected by temperature changes.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first imaging unit in which a driving piezoelectric bimorph element and a first sensing bimorph element are orthogonally joined to each other, and a monitor. a second vibration unit formed by orthogonally joining a piezoelectric bimorph element for detection and a second bimorph element for detection; A vibration type angular velocity sensor in which the second vibration unit has a tuning fork structure in which the free ends of the driving piezoelectric bimorph element and the monitoring piezoelectric bimorph element are connected to each other by a connecting plate so as to be parallel to each other along the detection axis. a first amplifier which has the function of driving the piezoelectric bimorph element for monitoring and whose amplification degree can be changed depending on the ambient temperature by using the output charge of the monitoring piezoelectric bimorph element as an input signal; a rectifier for rectification, a smoothing circuit for smoothing the output voltage of the rectifier, and an output voltage of the first amplifier as an input signal, the amplification degree being varied according to the output voltage value of the smoothing circuit, and output to the driving piezoelectric bimorph element. a second amplifier that outputs a signal, and a second amplifier that uses the output charges of the first detection bimorph element and the second detection bimorph element as input signals and amplifies the input and output signals with a phase shift of 90 degrees. a synchronous detector that synchronously detects the output voltage of the third amplifier with the polarity of the output voltage of the first amplifier; and a fourth amplifier that outputs a voltage.

If the above structure is used, in a tuning fork vibrating angular velocity sensor, the amplitude of the tuning fork vibration and the sensor sensitivity are proportional, so by changing the amplitude with temperature in accordance with the temperature change in sensitivity, the apparent temperature change in sensitivity can be suppressed. It can be reduced.

Embodiment Hereinafter, one embodiment of the angular velocity sensor drive circuit according to the present invention will be described based on the drawings.

First, Figures 5 to 7 about the tuning fork structure vibration type angular velocity sensor.
This will be explained using figures.

The angular velocity sensor has a structure as shown in FIG. 5, and is mainly composed of a drive element consisting of four piezoelectric bimorphs, a monitor element, and first and second detection elements, including a drive element 101 and a first detection element 103. The first
The vibration unit 109 and the second vibration unit 1-1.10, in which the monitor element 102 and the second detection element 104 are orthogonally joined at the joint 106, are connected by a connecting plate 107, and this connecting plate 107 is supported. It has a tuning fork structure supported at one point by the body 108.

When a sinusoidal voltage signal is applied to the driving element 101, the first vibration unit 109 starts to vibrate due to the inverse piezoelectric effect, and the second vibration unit L1. Start the vibration. Therefore, the charge generated on the surface of the monitor elements 1, 02 by the piezoelectric effect is proportional to the sinusoidal voltage signal applied to the drive element 1.01. This monitor element 1
．． By detecting the charge generated at 02 and controlling the sine wave voltage signal applied to the drive cable -f'-101 by -1 so that the amplitude becomes constant, stable tuning fork vibration can be obtained. can.

Mechanism 1: This sensor generates an output proportional to angular velocity
The mechanism will be explained using FIGS. 6 and 7. Fig. 6 shows the angular velocity sensor shown in Fig. 5 viewed from L. When a rotation with an angular velocity ω is applied to the sensing element r103 which is vibrating at a speed υ, the "Coriolis force" is applied to the sensing element 1 and 03. occurs. This "Konori force" is perpendicular to the speed υ and has a magnitude of 2
m t no ω. Detecting element ],,03 is vibrating like a tuning fork, so if detecting element 103 is vibrating at a speed υ at a certain point, detecting element 1.04 is vibrating at a speed -〇, which is the "Coriolis "force" is -2 mυω. Therefore, the sensing elements 103 and 1.04 are connected to each other as shown in FIG.
It deforms in the direction of the Coriolis force, and a charge is generated on the surface of the element due to the piezoelectric effect. Here, υ is the movement caused by the tuning fork vibration, and 1f and the vibration are v=a−s lnωot −C1)
a. Amplitude of tuning fork vibration (υ0) If it is the period of tuning fork vibration, "Coriolis force" is F ccta -ω - sin ωo
t - (2), which is proportional to the angular velocity ω and the tuning fork amplitude a, and detection A; child 1.
Force that deforms 03,104 in both directions. Hi naru. Therefore, the surface charge Q of the sensing elements 103 and 104 is QoCa 1ω-s i ncl)ot
−・”(3) If the seventh tuning fork amplitude a is controlled to a constant value, then Q・:<ω#s i +]ωo t
...(4), and the detection element 1. ．． 03
．． The surface charge ff1Q generated at 1.04 is obtained as an output proportional to the angular velocity ω.

If this signal is synchronously detected at ω0(, t is proportional to the angular velocity ω,
7. A DC signal is obtained. Note that even if a translational motion other than angular velocity is applied to this sensor, the sensing element 1.03, :! : Since charges of the same polarity are generated on the surfaces of the two elements of the sensing element 104, when converted to a DC signal, they cancel each other out and no output is produced.

As can be seen from equation (3), the amount of surface charge Q induced on the electrode of the sensing bimorph element of the tuning fork vibrating angular velocity sensor is proportional to the tuning fork amplitude a. If the sensitivity has a temperature characteristic as shown in the characteristic diagram in Figure 4, then let the temperature coefficient be β and (
3) The formula is Q −a ・ω −β (Ta −T )
s 1 n c + g t, ---15)
It can be expressed as Here, T, -T) is the temperature difference between the ambient temperature and the normal temperature.

Generally, the amplitude a of tuning fork vibration is controlled to be constant under any conditions, but as shown in equation (5), a temperature characteristic opposite to the temperature characteristic β of the sensor can be added to the amplitude a. It can be seen that the temperature dependence of Q can be reduced.

FIG. 1 is a block diagram showing one embodiment of the present invention, which is a method in which, as described above, the amplitude a of tuning fork vibration is given a temperature coefficient. The electric charge induced by the distortion in the monitor element 102 is converted into a voltage by the first amplifier 1, rectified by the rectifier 2, and converted into a DC voltage proportional to the amplitude a of the tuning fork vibration by the smoothing circuit 3.The second amplifier 4 amplifies the output voltage of the first amplifier 1 and drives the drive element 101, but the degree of amplification depends on the output voltage of the smoothing circuit 3, and the higher the output voltage of the smoothing circuit 3, the higher the degree of amplification. is a small smoothing circuit 3
The lower the output voltage, the higher the amplification degree.

When the amplitude of the tuning fork vibration increases, the electric charge induced in the electrode of the monitor element 102 increases, and accordingly, the output voltage amplitude of the first amplifier 1 increases. When the amplification degree of the second amplifier 4 becomes small (the amplitude of the voltage applied to the drive element 101 becomes small), the amplitude of the tuning fork vibration becomes small (the amplitude of the tuning fork vibration becomes small). It is kept at a constant value.

Reference numeral 14 denotes a temperature-dependent resistor whose resistance value increases as the ambient temperature rises, and the first amplifier 1 has a configuration in which the degree of amplification decreases as the temperature rises. Therefore, as the temperature increases, the amplitude of the tuning fork vibration decreases, and as the temperature decreases, the amplitude increases. First sensing element 103 and second sensing element 10
4, an alternating current charge is generated with an amplitude proportional to the applied angular velocity and a period equal to the tuning fork vibration period, and this alternating current charge is
The amplifier 5 converts the voltage into an alternating current voltage whose phase is shifted by 90 degrees. Furthermore, this voltage signal is synchronously detected by the synchronous detector 6 according to the polarity of the output voltage of the first amplifier 1, and smoothed and amplified by the fourth amplifier 7 to obtain a voltage proportional to the angular velocity. Expressing this in a formula, the charges generated in the first sensing element 103 and the second sensing element 104 are (
5) Expressed by the formula Q+o: ++Q+o4= a・ov・β(Ta T)
sin ωot... (5) If it is, then the output of the third amplifier converts equation (5) into a voltage and shifts the phase by 90", so this output voltage is v5 Then, V5-G1・a・ω・β(Ta T)cos(J)o
t...(6) It can be expressed as:

However, G1 is a coefficient for converting the charge of the third amplifier into voltage. The output voltage V5 expressed by equation (6) is further synchronously detected by a synchronous detector. The timing of synchronous detection is determined by the polarity of the output voltage of the first amplifier 1. Since the output voltage V of the first amplifier 1 has a phase that is 90 degrees ahead of the speed υ of tuning fork vibration, Vl = G2 cos ωo t
-=-(7) However, G2 is a coefficient for converting the charge of the first amplifier into a voltage.

As can be seen from equations (6) and (7), v5 and vl are in the same phase, so if V5 is synchronously detected with the polarity of vl, smoothed and amplified by the fourth amplifier 7, the output voltage of the fourth amplifier 7 is V
4 is V4=(g-G3・a・ω・β(Ta-T) −
-----(8) However, G3 is the gain of the fourth amplifier.

It can be seen from equation (8) that a voltage proportional to the angular velocity ω can be obtained. G1. G3. Normally, a is a constant, but since there is a temperature coefficient β of the sensor itself, in this embodiment, by adding a temperature-dependent resistor 2 to the first amplifier 1, a temperature characteristic opposite to β is added to the amplitude a. This cancels out the temperature coefficient β of the sensor itself.

Note that the amplification degree GI of the third amplifier 5 has temperature characteristics. It is also possible to give temperature characteristics to the amplification degree G3 of the fourth amplifier 7, but in this case it is not preferable because it causes a temperature change in the S/N ratio and a temperature change in the DC offset voltage.

Effects of the Invention According to the present invention, it is possible to correct the temperature characteristic of sensitivity, which is a problem peculiar to a tuning fork structure vibration type angular velocity sensor.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an angular velocity sensor drive circuit according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional angular velocity sensor drive circuit, and FIG. 3 is a cross-sectional view of a piezoelectric bimorph element.
Figure 4 is a characteristic diagram showing the temperature characteristics of the sensitivity of the angular velocity sensor.
FIG. 5 is a perspective view of the tuning fork structure vibration type angular velocity sensor, and FIGS. 6 and 7 are diagrams for explaining the operation of the angular velocity sensor. 1... First amplifier, 2... Rectifier,
3... Smoothing circuit, 4... Second amplifier, 5... Third amplifier, 6... Synchronous detector, 7... ... Fourth amplifier, 8 ... Angular velocity sensor drive circuit, 9 ... Tuning fork structure vibration type angular velocity sensor, 14 ... Temperature dependent resistance, 101
... Drive element, 102 ... Monitor element, 103 ... First detection element, 104 ...
...Second detection element, 105, 106...Joint portion, 107...Connection plate, 109...
First vibration unit, 11O...Second imaging unit]\.

Claims (2)

[Claims] (1) A first vibration unit in which a piezoelectric bimorph element for driving and a first bimorph element for detection are connected orthogonally to each other, and a piezoelectric bimorph element for monitoring and a second bimorph element for detection are connected orthogonally to each other. the driving piezoelectric bimorph element and the monitoring piezoelectric bimorph element are arranged so that the first and second vibration units are parallel to each other along the detection axis. A first sensor having a function of driving a vibrating angular velocity sensor having a tuning fork structure whose ends are connected by a connecting plate, and whose amplification degree can be changed depending on the ambient temperature by using the output charge of the monitoring piezoelectric bimorph element as an input signal. an amplifier; a rectifier that uses the output voltage of the first amplifier as an input signal and performs full-wave rectification;
a smoothing circuit for smoothing the output voltage of the rectifier;
a second amplifier which uses the output voltage of the amplifier as an input signal and outputs an output signal to the driving piezoelectric bimorph element, the amplification degree of which is varied according to the output voltage value of the smoothing circuit; a third amplifier which uses the output charge from the second detection bimorph element as an input signal and amplifies the input/output signal by shifting the phase of the input/output signal by 90 degrees;
a synchronous detector that synchronously detects the output voltage of the amplifier according to the polarity of the output voltage of the first amplifier; and a fourth amplifier that smooths and amplifies the output voltage of the synchronous detector and outputs a voltage proportional to the angular velocity. An angular velocity sensor drive circuit composed of (2) The angular velocity sensor drive circuit according to claim 1, wherein the amplification degree of the third amplifier is changed depending on the ambient temperature.