JPH03276013A - Angular velocity sensor - Google Patents

Abstract

PURPOSE:To eliminate an unnecessary signal component and to improve the detection accuracy by adjusting the area of a piezoelectric element for driving and the electrode for a signal lead-out wire. CONSTITUTION:When AC electric power is supplied to the piezoelectric element 3 for driving, the piezoelectric element 3 for driving is put in tuning fork vibration. A piezoelectric element 1 for detection when rotating at an angular velocity omegagenerate a voltage with a Coriolis force. When the orthogonal error between the piezoelectric element 3 for driving and piezoelectric element 1 for detection is large, an unnecessary signal is generated to generate an error. Electrode lead-out parts 12a and 12b are provided to parts of electrodes 8a and 8b for signal lead-out wires and removed partially to form trimming parts 13. The area of the trimming parts 13 is adjusted to balance the generation of charges and the unnecessary signal component due to the orthogonal error, etc., is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gyroscope, and particularly to an angular velocity sensor using vibration of a piezoelectric element.

BACKGROUND OF THE INVENTION Conventionally, a mechanical rotary gyro has been mainly used as an inertial navigation device using a gyroscope to determine the direction of a moving object such as an airplane or a ship.

Although this method can provide stable orientation, since it is mechanical, the device is large-scale and costly, and it is difficult to apply it to equipment where miniaturization is desirable.

On the other hand, there is a vibration-type angular velocity sensor that vibrates an object without using rotational force and detects the r Coriolis force from the vibrated sensing element. Many of these structures employ piezoelectric and electromagnetic mechanisms. In these cases, the mass that makes up the gyro does not move at a constant speed, but instead vibrates. Therefore, when angular velocity is applied, the Coriolis force is
This occurs as a vibrational torque with a frequency equal to that of the mass. The principle of a vibration-type angular velocity sensor is to measure angular velocity by detecting vibrations caused by this torsion, and in particular, many sensors using piezoelectric materials have been devised. (Journal of the Japan Society of Aeronautics and Astronautics Vol. 23 No. 267 No. 339-3
(Page 50) The structure of an angular velocity sensor based on the above principle is shown in FIG. In FIG. 3, 1 is a detection piezoelectric element, 2 is a coupling member, and 3 is a drive piezoelectric element, and the drive piezoelectric element 3 and the detection piezoelectric element 1 are joined to each other orthogonally by the coupling member 2. This constitutes a sensor element. Then, this pair of sensor elements is connected to the above (dynamic piezoelectric element 3).
A tuning fork element is constructed by joining the end portions of the two parts using an elastic coupling member 4 so as to form a tuning fork structure. Further, this tuning fork element is mounted on a base 6 while being supported by a support pin 6 whose one end is connected to approximately the center of the elastic coupling member 4.

Reference numeral 7 denotes a driving electrode formed to face both sides of the driving piezoelectric element 3, and El and 8b denote a signal lead line formed on the driving piezoelectric element 3 so as to be disposed outside the pivoting electrode 7. The lead wire 9 drawn out from the electrode of the detection piezoelectric element 1 is connected to the detection piezoelectric element 1, and leads are drawn out from the detection piezoelectric element 1.

10 is this driving electrode 7. These are lead wires that connect the signal lead wires 81L, 8b and the lead pins 11 implanted in the pace 6.

In order to operate the conventional angular velocity sensor configured as described above, first, in order to drive the pair of driving piezoelectric elements 3, the opposing inner surfaces are used as a common electrode, and the driving piezoelectric elements 3 on the outer surfaces are An alternating current signal is applied between the electrode 7 for use. The drive piezoelectric element 3 to which the signal is applied begins to vibrate symmetrically around the elastic coupling member 4, which is what is called a tuning fork vibration.

When a rotation with an angular velocity ω is applied to the detection piezoelectric element 1 which is vibrating at a speed υ, a "Coriolis force" is applied to the detection piezoelectric element 1.
occurs. This "Coriolis force" is perpendicular to the speed υ and has a magnitude of 2mυω. Since the tuning fork is vibrating, if one of the detection piezoelectric elements 1 is vibrating at a speed υ at a certain point, the other detection piezoelectric element 1 is vibrating at a speed -〇, and the r Coriolis "force" is -2 mυω. A pair of detection piezoelectric elements 1 have "Coriolis forces" in opposite directions.
acts, deforms in opposite directions, and charges are generated on the surface of the element due to the piezoelectric effect. A pair of sensor elements are wired so that charges generated by the "Coriolis force" are added to each other.

Therefore, 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 pair of detection piezoelectric elements 1, so that they cancel each other out and no output is produced.

Here, υ is the speed caused by tuning fork vibration, and if the tuning fork vibration speed is υ−υO−sinωot υ0 : tuning fork vibration velocity amplitude ω0 : angular period of tuning fork vibration, then r Coriolis force is FQ = 2 m −υ
0・ω・stnωot, which is proportional to the angular velocity ω and the tuning fork vibration speed υ0, and becomes a force that deforms the sensing piezoelectric element 1 in the plane direction. Therefore, the surface charge amount Qc of the sensing piezoelectric element 1 is: Qcocυ0-ω-stnωo1, and if the tuning fork vibration velocity amplitude υ0 is controlled to be constant, then QCC(ω-sinωot), and the amount of surface charge Q generated on the detection piezoelectric element 1 is an output proportional to the angular velocity ω. can get.

In addition to the above r Coriolis force, the detection piezoelectric element 1 has
Deformation occurs due to the drive inertia force. This will be explained using FIGS. 4 and 5.

FIG. 4 is a top view of the detection piezoelectric element 1 and the drive piezoelectric element 3. It is desirable that the detection piezoelectric element 1 and the drive piezoelectric element 3 are orthogonal to each other! However, due to assembly accuracy problems, it deviates from the right angle as shown in FIG.

Therefore, as shown in FIG. 5, deformation occurs in the detection piezoelectric element 1 due to the vibration of the drive piezoelectric element 1. This is a force that causes deformation in the detection piezoelectric element 1 when the degree of orthogonality between the detection piezoelectric element 1 and the driving piezoelectric element 3 deviates from each other. The deformation of the detection piezoelectric element 1 is proportional to the displacement of the driving piezoelectric element 3, and is also proportional to sin θ, where θ is the deviation angle from orthogonality. Therefore, the surface charge amount Qa of the detection piezoelectric element 1
is Qa"υ0/ωo-5in(ωot・π/2)-sin
θ, tuning fork vibration velocity amplitude υ0 and drive vibration angular frequency ω. If is controlled to be constant, then Qa ■sin (ωo t −π/2 )−sinθ
The amount of surface charge Qa generated on the detection piezoelectric element 1 depends on the deviation angle θ from orthogonality, but its phase is equal to the amount Qc of surface charge generated on the detection piezoelectric element 1 due to the r Coriolis force. It is shifted by π/2.

Therefore, the amount of surface charge (Qc
+Qa) with ωot, a DC signal proportional to the angular velocity ω can be obtained.

The method of synchronous detection will be explained using FIG. FIG. 6 shows a method in which a pass-inverting amplifier is used to perform multiplication with a rectangular wave. The signal component generated by the ``R Coriolis force'' remains as a DC component, but the unnecessary signal component generated by the ``drive inertia force'' is canceled by synchronous detection.

Further, charges are generated in the driving electrode 7 on each driving piezoelectric element 3 according to the deformation of each driving piezoelectric element 3, but the shape is symmetrical with that of the driving electrode 7 and the area is small. Since they are made equal, the generated charges are the same, so the generated charges are canceled by signal processing using differential input.

Problems to be Solved by the Invention The angular velocity sensor having the above configuration has the following problems.

Since the detection piezoelectric element 1 has a width of 1.611ffff and the driving piezoelectric element 3 has a width of 2.5 mm, it is difficult to improve orthogonal accuracy in orthogonal assembly. For example, if a gradient of 0.1 is created at both ends of the width of the detection piezoelectric element 1, the orthogonality error will be 3°35'.

If the orthogonality error is large, the unnecessary signal components generated by the "drive inertia" will become large, and the passing through used for signal processing -
6 Vpp, which maintains the linearity of the signal amplification factor of the inverting amplifier
Go beyond 1.

The two signal lead-out electrodes 8 on the piezoelectric drive element 3 are designed to have the same area.
Variations occur, and only the differences are superimposed on the above-mentioned unnecessary signal components.

Therefore, it has become impossible to correctly extract only the angular velocity component.

The present invention has been made in view of these points, and an object of the present invention is to obtain an angular velocity sensor in which unnecessary signal components are reduced to below e Vpp and only angular velocity components can be correctly extracted through signal processing.

Means for Solving Problem 1 In order to solve the above problems, the present invention adjusts the effective area of the electrode used as the signal lead line of the drive piezoelectric element.

Effect The above configuration reduces unnecessary signal components to 6Vpp or less,
It becomes possible to obtain an angular velocity sensor that can correctly extract only the angular velocity component through signal processing.

Embodiment FIG. 1 is a perspective view showing an embodiment of an angular velocity sensor according to the present invention. Referring to FIG. 1, the same parts as in FIG. 3 are given the same numbers. 12J12b is the signal lead wire electrode 8I! An electrode extraction part 13 is provided in a part of L, 8b and serves both for lead wiring and adjustment. Reference numeral 13 is a trimming part obtained by removing a part of the electrode extraction part 121L, 12b.

The principle of angular velocity detection is the same as that of the conventional example, so it will be omitted, and it will be explained that by adjusting the area of the signal electrode, unnecessary signal components generated by "drive inertia" can be canceled.

Signal from signal leader electrode 8 & signal leader electrode 8
Since the signal from b is received differentially, the electric charge generated at the electrode 8a and the surface (
The difference between the sum of the charges generated at the electrode 8b and the sum of the charges generated at the surface connected to the electrode 8b of the detection piezoelectric element 1 (hereinafter referred to as the surface). becomes an unnecessary signal component. By adjusting the area, that is, trimming, by burning out the electrode lead-out portions 121L and 12b of the signal line lead-out electrodes 8a and 8b with a laser, unnecessary signal components can be reduced to a specified amount or less.

The state of charge generation in each electrode when the driving piezoelectric element 3 is deformed will be explained. The difference in orthogonality between the detection piezoelectric element 1 and the driving piezoelectric element 3 is when the electrode 8a side is at an acute angle, and when the electrode 8a side is at an acute angle.
Sometimes it is an obtuse angle. Consider a case where the electrode 8a side is at an acute angle.

As shown in FIG. 2, when the driving piezoelectric element 3 is tilted toward the inner common electrode side, the outer signal electrode side expands and generates a positive charge. The detection piezoelectric element 1 is tilted toward the a-plane side, and that side is shrunk to generate a negative charge.

The b-plane side stretches and generates positive charges. Therefore, it is sufficient to trim the electrode area of the electrode 8b. Conversely,
When the driving piezoelectric element 3 is tilted toward the outer signal electrode side, the signal electrode side contracts and generates negative charges. The detection piezoelectric element 1 is tilted toward the b-plane side, and that side is shrunk and generates a negative charge. Furthermore, the a-plane side stretches and generates positive charges. Therefore, it is only necessary to trim the electrode area of the electrode 8b, and since the amount of displacement of the sensing piezoelectric element 1 is proportional to the amount of displacement of the driving piezoelectric element 3, the necessary trimming part is when the electrode area is tilted to the opposite side as described above. is the same as

Furthermore, when the electrode 8a side is obtuse, the electrode 81L and the a-plane of the detection piezoelectric element 1 generate charges of the same polarity, so the electrode 8a may be trimmed.

From these facts, it can be seen that it is sufficient to trim the electrode for the signal lead line on the side where the angle at which the detection piezoelectric element 1 and the drive piezoelectric element 3 intersect is an obtuse angle.

The linearity of the signal amplification factor of the pass-inverting amplifier is maintained at 5Vppt, so if the unnecessary signal components are trimmed to 6vpp or less, only the angular velocity component can be correctly extracted using the signal processing described above. can. If the unnecessary signal components are reduced, the error at the time of passing and reversing will be reduced, so the accuracy of angular velocity detection will be improved, and stable angular velocity detection will be possible even if the ambient temperature changes.

In this embodiment, an electrode extraction part 121L as an adjustment electrode,
12b is placed near the fixed end of the driving piezoelectric element 3, and since the distortion is large at that position, the effect of adjusting unnecessary signal components by trimming the same area becomes large.

In particular, there is no need to provide an adjustment electrode, and any position of the signal lead line electrode may be trimmed. Also,
In order to improve the accuracy of adjustment, it is sufficient to trim the area near the connecting member where the distortion is small (on the contrary, the distortion is large in the immediate vicinity).

In this example, adjustment electrodes are provided on both signal lead wire electrodes, but only one electrode is provided with an adjustment electrode, so that even when that electrode side becomes the minimum acute angle in orthogonal assembly, If the area of the button is set so that adjustment can be made by trimming the adjustment electrode, there is no need to select the electrode to be trimmed by simply changing the trimming portion.

In this example, the electrodes are removed using a laser.
After soldering the pins, it will not work no matter how you trim the electrodes, such as peeling off the electrodes along with the pins.

Since the purpose of the present invention is to adjust the effective electrode area of the housing, the purpose of the present invention can also be achieved by removing the polarization of the piezoelectric element in the signal electrode portion by heating or the like.

As described in detail, according to the present invention, by adjusting the area of the signal lead-out electrode of the driving piezoelectric element, unnecessary signal components can be reduced to below a specified value, so that only the angular velocity component can be correctly detected by signal processing. This makes it possible to obtain an angular velocity sensor with high precision and resistance to environmental temperature changes.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an angular velocity sensor according to an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the state of charge generation in the sensor, Fig. 3 is a perspective view of a conventional angular velocity sensor, and Fig. 4 is the same. A top view of the detection piezoelectric element and the drive piezoelectric element of the sensor, FIG. 6 is an explanatory diagram showing the generation of drive inertia force, and FIG. 6 is an explanatory diagram to explain the AC-DC conversion method. . 1... piezoelectric element for detection, 2.4... coupling member, 3... piezoelectric element for drive, 7...
Drive electrode, Sa. 8b...Signal leader line electrode, 12&, 12b...
... Electrode extraction part, 13... Trimming part.・Name of agent: Patent attorney Shigetaka Awano and 1 other person No.3

Claims (1)

[Claims] A driving piezoelectric element and a sensing piezoelectric element are connected to each other orthogonally by a connecting member to form a sensor element, and a part of the electrode provided on the driving piezoelectric element is connected to a signal from the sensing piezoelectric element. An angular velocity sensor that is used as a leader line and is characterized in that the signal leader line electrode is provided with an adjustment part for adjusting the effective area of the electrode.