KR19990031118A - 2-axis piezoelectric gyroscope - Google Patents

Abstract

A biaxial piezoelectric gyroscope capable of simultaneously measuring the rotation angle of an object in the biaxial direction is disclosed. According to one embodiment, a driving element for the linear velocity in the z-axis direction is attached to the bottom of the box-shaped metal, four pieces of piezoelectric elements are attached to each side of the metal box for sensing for each rotation direction. Since the body is in the form of a box, the piezoelectric elements are naturally arranged to be orthogonal to each other. At this time, as the adhesive, an adhesive capable of conducting electricity alone is used. In this structure, the entire metal box simultaneously serves as an electrical ground. According to another embodiment, in the cross-shaped structure, a piezoelectric element for driving is attached with a conductive adhesive on a support to give a linear velocity in the z-axis direction. After the thin permalloy flakes are attached to hold the ground thereon, the flakes of the four piezoelectric elements for detection are placed and bonded to each other at right angles to the two rotation directions.

Description

2-axis piezoelectric gyroscope

The present invention relates to a biaxial piezoelectric gyroscope capable of simultaneously measuring the rotation angle of the object in the biaxial direction.

The rotation angle sensor (gyroscope) has been widely used in aircraft, missiles, etc. as a device for measuring the rotation of the inertial body in the form of a rotation angle about any axis as a reference. There are many types of gyroscopes. The conventionally used type was a method of measuring torque acting on a rapidly rotating wheel, but now piezoelectric and optical types have been developed. Conventional mechanical gyroscopes require motors and bearings and have weak disadvantages for mechanical wear and impact, while optical ring laser gyros, now known for their highest precision, are too expensive to be used in inexpensive systems. There is a problem.

Piezoelectric gyroscopes made of piezoelectric materials with overcoming these shortcomings and having an appropriate price and precision have recently been commercialized in camcorders and car navigation systems.

The piezoelectric material refers to a material having a property capable of converting mechanical energy and electrical energy applied thereto, and the piezoelectric effect is expressed by stress, electric field, deformation, and electrical displacement applied to the material. The relationship between these variables is followed by the piezoelectric coefficient, and the piezoelectric effect of the material is represented using the electromechanical coupling coefficient K. Where K is defined as the fraction of the amount of energy converted into mechanical energy relative to the electrical energy applied to the material, or vice versa. Therefore, when electrical energy is applied to the piezoelectric element having a good electromechanical coupling coefficient, the ultrasonic signal can be oscillated. Conversely, the ultrasonic signal from the outside is converted into an electrical signal by the piezoelectric element. Taking advantage of these piezoelectric materials, first, a linear conversion between electrical and mechanical energy is possible. Therefore, in the case of the mechanical conversion amount, for example, vibration, it is possible to precisely control by adjusting the magnitude of the voltage to apply the amplitude. Conversely, external vibration signals can be received as precisely linear electrical signals. Furthermore, this transformation occurs entirely due to the properties of the material itself without the aid of any external mechanism. In other words, by simply replacing the piezoelectric material specimens of the conventional complex motor or turbine can be achieved.

There are various kinds of piezoelectric materials having such characteristics, and there are broadly classified piezoelectric ceramics and piezoelectric polymers. Piezoelectric polymer is a high-density polymer material of PVDF. Unlike ceramic, it has low acoustic impedance and high piezoelectric voltage constant. However, piezoelectric polymer has a disadvantage that piezoelectric displacement constant is considerably smaller than ceramic. Up to now, due to technical limitations in polymer manufacturing, no localization has been achieved, and the application cases are limited to a few cases such as high frequency ultrasonic devices. However, due to its flexibility, high sensitivity as a sensor, and ease of shape change, it is expected that the application field will increase.

Piezoelectric ceramics are divided into piezoelectric single crystals and piezoelectric polycrystals. Piezoelectric single crystals have advantages such as high purity, uniformity of material properties, low temperature coefficient, and high frequency characteristics, but due to limitations of low piezoelectric efficiency and high price, It is limited to applications such as small, precise passive elements and sensors. On the other hand, piezoelectric polycrystals are widely used due to their relatively low purity, temperature stability, and uniformity of properties, but with high piezoelectric properties, low cost, and above all, their characteristics can be arbitrarily changed to some extent as necessary. It is becoming an application. Representative piezoelectric polycrystalline materials include PZT, BaTiO ₃ , LiNbO ₃ , LiTaO _3, etc. PZT is the most recent high-power piezoelectric material.

The principle that the piezoelectric gyroscope detects rotation is that when a linear velocity is applied in the x-axis direction with respect to the object 1 as the rotation is applied around the z-axis, a Coriolis force is generated in the y-axis direction. Done. A piezoelectric gyroscope is a sensor that applies a linear velocity, which is already known about the applied rotation, in the x-axis direction using a piezoelectric system, and then detects Coriolis force generated in the y-axis direction using a piezoelectric body.

Such piezoelectric rotation angle sensors are miniaturized, have low manufacturing costs, and have a precise characteristic, and thus are widely used. The piezoelectric rotation angle sensor mainly uses a method of comparing the magnitude of the oscillated signal by configuring the oscillation circuit using the resonance point of the piezoelectric material, but the circuit structure has a disadvantage.

In addition, all of these piezoelectric gyroscopes commercially available so far are single-axis gyroscopes that can measure the rotation angle of an object rotating on one plane. Such one-axis gyroscopes should be installed to be orthogonal to two or three in order to measure the rotation angle of a rotating object about two or more reference axes in space, such as a camcorder or a articulated robot.

Piezoelectric gyroscopes capable of simultaneously detecting two or more rotations are disclosed in Korean Patent Nos. 95-5388 and 95-5389.

In the piezoelectric gyroscope disclosed in Japanese Patent No. 95-5388, referring to FIG. 2, the z-axis of the piezoelectric films 11 and 11 ′ for driving is provided with a metal holder 14 disposed on the base 15. Direction in parallel to the zy plane, and the y-axis rotation angle sensing piezoelectric films 13 and 13 'on the piezoelectric films 11 and 11' in parallel to the xy plane in the y-axis direction, and the piezoelectric The z-axis rotation angle sensing films 12 and 12 'are disposed on the films 13 and 13' in parallel to the xz plane in the z-axis direction.

Further, as shown in FIG. 3, a piezoelectric gyroscope is disclosed in which a piezoelectric sensor structure is formed into a tetrahedron in the form of a quadrangular pyramid, and an equilateral triangular piezoelectric element is attached to each side and bottom of the metal structure. It is.

The piezoelectric gyroscope disclosed in the above publication has a shape having a coarse structure by a conceptual approach (see FIG. 2), or the structure is stable, but the piezoelectric body attached to the surface is also triangular, which is quite difficult to manufacture and error in processing. It has a pyramid shape (see FIG. 3) that can only be accompanied.

In addition, the inventors of the present application found that the thickness and width of the PZT does not significantly affect the resonant frequency, but the length has a significant effect on the resonant frequency. In other words, the larger the size of the piezoelectric gyroscope, the higher the sensing sensitivity. However, in the piezoelectric gyroscope disclosed in the above publication, when the length of the PZT is increased, the height of the gyroscope increases, which causes a problem in that the entire structure is enlarged.

The present invention proposes a biaxial piezoelectric gyroscope that is not only structurally stable compared to the above-described three-dimensional piezoelectric gyroscope, but also can be easily manufactured without accompanying errors in manufacturing.

An object of the present invention is to solve the above-mentioned disadvantages, and to provide a piezoelectric gyroscope capable of simultaneously measuring rotation about two axes using one sensor.

Another object of the present invention is to provide a piezoelectric gyroscope whose height does not increase even when the size of the piezoelectric body is increased.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the principle of operation of a piezoelectric gyroscope.

2 and 3 are perspective views of a conventional three-dimensional piezoelectric gyroscope.

4 is a perspective view of a box-type piezoelectric gyroscope according to the present invention.

5 is a perspective view of a cruciform piezoelectric gyroscope according to the present invention;

6 is a circuit diagram of a piezoelectric gyroscope according to the present invention.

<Description of the code | symbol about the principal part of drawing>

2, 2 ', 102, 102': piezoelectric material

3, 3 ', 102, 103': piezoelectric material

4, 4 ', 104, 104': metal support

5, 105: piezoelectric material

50: signal generator

52: gyroscope

54, 56: charge amplifier

58, 60: voltage amplifier

62, 64: peak detector

66: differential amplifier

In order to achieve the above object, according to a first aspect of the present invention, there is provided a biaxial gyroscope using a plurality of piezoelectric materials, comprising: a rectangular metal base for grounding; A drive piezoelectric material attached to a lower surface of the metal base by a conductive adhesive, the drive piezoelectric material attached by a nonconductive adhesive such that a linear velocity direction of the drive piezoelectric material becomes a thickness direction of the drive piezoelectric material; And a plurality of sensing piezoelectric materials attached to four sides of the metal base so as to be perpendicular to the linear velocity direction to sense the rotation angle with respect to the reference axis of the two axes.

According to a second aspect of the present invention, there is provided a biaxial gyroscope using a plurality of piezoelectric materials, comprising: a metal plate for grounding; A driving piezoelectric material attached to either side of the metal plate by a conductive adhesive, the driving piezoelectric material being attached such that a linear velocity direction of the driving piezoelectric material becomes a thickness direction of the driving piezoelectric material; And at least four piezoelectric materials for sensing, each edge being bonded with a non-conductive adhesive to the other side of the metal plate so as to be perpendicular to the linear velocity direction so as to sense a rotation angle with respect to a reference axis on two axes. An axial piezoelectric gyroscope is provided.

A biaxial piezoelectric gyroscope according to the present invention includes a waveform generator for applying a linear velocity to the piezoelectric material for driving; An amplifier for amplifying the charge generated in the piezoelectric material for sensing; A detector for removing a frequency component of a drive signal from the signal generated by the amplifier and outputting only a signal for a rotational angular velocity; And a differential amplifier that obtains a signal proportional to the final rotational angular velocity based on the difference value of the signal generated at the detector.

Hereinafter, an embodiment of a biaxial piezoelectric gyroscope according to the present invention will be described in detail with reference to the accompanying drawings.

The inventor of the present application designed a two-axis gyroscope by adding one more axis based on this principle in the one-axis model using the Coriolis principle. In this design, the piezoelectric element acting as a sensor driving is arranged in the z-axis direction to apply a linear velocity. In the piezoelectric element under motion at the applied linear velocity, a sensing element for sensing the Coriolis force on the x-axis rotation is placed on the y axis, and a sensing element for sensing the Coriolis force on the y-axis rotation is placed on the x-axis. Placed. The piezoelectric element also contains superconductivity. Responsiveness due to this pyroelectric property is mixed with piezoelectric properties, which are the mainstay of the gyroscope, and the signal due to this pyroelectric property acts as an unwanted noise component in the present gyroscope and needs to be compensated for. For this thermal compensation, the polarities of the sensing elements were reversed and arranged in pairs so that the difference values were canceled out in the circuit.

An embodiment of a biaxial piezoelectric gyroscope according to the present invention has a box-shaped structure (shown in FIG. 4) in which a piezoelectric element is bonded to a metal whose body is box-shaped, and a cross-shaped structure in which a sensing element portion is manufactured in a cross-shaped form with a piezoelectric element. (Shown in Figure 5).

A drive element for the z-axis linear speed is attached to the bottom of the box-shaped metal, and four pieces of piezoelectric elements are attached to each side of the metal box for sensing of each rotation direction. Since the body is in the form of a box, the piezoelectric elements are naturally arranged to be orthogonal to each other. At this time, as the adhesive, an adhesive capable of conducting electricity alone is used. In this structure, the entire metal box simultaneously serves as an electrical ground.

In the cruciform structure, a piezoelectric element for driving is attached with a conductive adhesive on a support to give a linear velocity in the z-axis direction. After the thin permalloy flakes are attached to hold the ground thereon, the flakes of the four piezoelectric elements for detection are placed and bonded to each other at right angles to the two rotation directions.

Hereinafter, embodiments of the box-shaped and cross-shaped piezoelectric gyroscopes according to the present invention will be described in detail with reference to the accompanying drawings.

4 schematically shows a box-type piezoelectric gyroscope. Referring to FIG. 4, the metal support 4 'is disposed parallel to the x-y plane, and the piezoelectric material 5 is attached using the conductive adhesive above the metal support. And the metal support 4 is attached on it using a normal adhesive again. The piezoelectric material 5 corresponds to a drive for providing a linear velocity to an object in the principle of the piezoelectric gyroscope described above. Electrodes are provided on both planes of the piezoelectric material 5 and electromagnetic signals of a sine wave or pulse wave are applied to generate linear velocity in the z-axis direction of FIG. 4.

Piezoelectric materials (2, 2 ') and (3, 3') are attached to four surfaces corresponding to the x-z and y-z planes except for the upper surface of the remaining metal plane (4) using a conductive adhesive. At this time, the piezoelectric materials 2 and 2 'installed on the surface corresponding to the xy plane of the metal support detect the rotation angle from the rotational speed? X in the x-axis direction and attach in parallel to the yz plane of the metal support 4'. The piezoelectric materials 3 and 3 'sense the rotation angle from the rotational speed? Y.

In the present invention having the structure as described above, the pulse wave or the sine wave of the signal generator 50 of FIG. 6 is applied to the piezoelectric material 5 of the driving unit to detect the rotation angle by the sensor, and the piezoelectric material 2 of the x-axis is applied. The charge according to the rotational force Ωx detected at 2 ') or the piezoelectric materials 3, 3' at the y-axis is amplified by the amplifiers 54 to 60, and its output is finally rotated at the detectors 62 and 64. It is configured to be connected to each signal output.

Fig. 5 schematically shows a cruciform piezoelectric gyroscope. Referring to FIG. 5, the metal support 104 ′ is placed parallel to the xy plane and the piezoelectric material 105 is attached using a conductive adhesive on top of the metal support, and the metal support 104 is then placed on the normal adhesive again. Use to attach. At this time, the piezoelectric material 105 corresponds to a driving unit that provides linear velocity to an object in the above-described piezoelectric gyroscope principle, by installing electrodes on both planes and applying an electromagnetic signal of a sine wave or pulse wave to FIG. 5. Linear velocity is generated in the z-axis direction.

Piezoelectric materials 103 and 103 'are disposed above the metal support 104 in the y-axis direction in parallel to the y-z plane, and piezoelectric materials 102 and 102' are disposed in the x-axis direction in parallel to the x-z plane. At this time, the piezoelectric materials 103 and 103 'sense the rotation angle from the rotational speed? Y and the piezoelectric materials 102 and 102' detect the rotational angle from the rotational speed? X in the x-axis direction.

In order to detect the rotation angle by the cross-shaped gyroscope having the structure as described above, the pulse wave or sine wave of the signal generator 50 shown in FIG. 6 is applied to the piezoelectric material 105 of the driving unit, and the piezoelectric on the x-axis is applied. The electric charges corresponding to the rotational force Ωx sensed by the materials 102 and 102 'or the piezoelectric force Ωy sensed by the piezoelectric materials 103 and 103' on the y-axis are amplified by the amplifiers 54 to 60, and their outputs are detected by the detectors 62 and 64. ) To be output as the final rotation angle signal.

As the piezoelectric material used in the above-described embodiment of the gyroscope, PZT, BaTiO ₃ , LiNbO ₃ , LiTaO ₃ , quartz, or the like may be used as the piezoelectric ceramic having the same shape and physical properties.

Particularly, the longer the length of the piezoelectric material is, the higher the sensitivity can be obtained. The smaller the width of the piezoelectric material, the more uniform the angular moment distribution on the surface.

However, due to processing difficulties, it is appropriate to bring about 1/5 of the maximum length in consideration of durability. In addition, the thinner the thickness of the piezoelectric material, the better the selectivity and sensitivity of the vibration mode, but considering the processing and durability, it is appropriate to bring about 1/10 of the maximum length.

In addition, the piezoelectric material disposed above the metal support must be positioned to achieve exactly 90 ° and must be secured using an adhesive or structure so that only mechanical bonding is achieved by mutually adhering with a nonconductive adhesive.

Referring to FIG. 6, which shows a circuit of a piezoelectric gyroscope, an operation in which a piezoelectric gyroscope according to the present invention detects rotation using a Coriolis force will be described.

When the object having a linear speed (U) and vibrating receives a rotation, the force (F) is received in a direction that is proportional to the rotation angle speed and perpendicular to the linear speed (U) and the rotation direction (W). At this time, by placing the piezoelectric material capable of sensing this force perpendicular to the plane of the force, a change in the amount of charge proportional to the rotation angle can be derived. Here, by having two oppositely polarized piezoelectric sensing units instead of one sensing unit, the difference in the amount of charge is finally obtained by using a differential amplifier to double the magnitude of the output voltage and compensate by thermal noise from the outside.

The circuit shown in FIG. 6 serves to induce a Coriolis force generated in proportion to rotation in the form of a voltage, and is composed of a waveform generator and a signal processor. The waveform generator generates a square wave or a sinusoidal wave, and the frequency can be varied so that the waveform generator can be accurately driven at the resonance point of the driving piezoelectric body. The waveform generator is connected to the driving piezoelectric body 5; 105 and used to generate the linear velocity in the vertical direction.

Due to the Coriolis force generated when a rotation is applied to an object driven at a certain frequency, a charge proportional to the force is generated in the sensing element, which is connected to the charge amplifiers 54 and 56 and linearly converted into a voltage form. Is amplified. In this case, the amplified signal passes through the voltage amplifiers 58 and 60 again because the signal is very weak. The signal generated by the amplifier has the driving frequency component (ω ₁ ) and the frequency component of the rotational angular velocity (ω ₂ ) as shown in the following equation.

V ∝ u × w

= U cos (ω ₁ t) × W cos (ω ₂ t + φ)

Where U and ω ₁ are constants.

In particular, since the driving frequency component ω ₁ has a much larger value than the frequency component ω ₂ of the rotation angle, the driving frequency and the frequency component of the rotational motion overlap with each other and appear in amplitude modulated form. Therefore, in order to remove the driving frequency component from the output, the peak detector is used to smooth the DC component to obtain the output component only for the rotational speed. The difference between the signal obtained on one side and the signal on the other side is obtained by using the differential amplifier 66, thereby doubling the magnitude of the output voltage and eventually obtaining a signal proportional to the rotation speed.

4 and 5, when the external oscillation signal is inputted to the driving piezoelectric material 5; 105, the piezoelectric material is stretched and contracted by a signal corresponding to the resonance frequency of the piezoelectric material 5. It works. Accordingly, the piezoelectric materials 2, 2 '; 102, 102' and the piezoelectric materials 3, 3 '; 103, 103' have a linear movement Vz in the z-axis direction. At this time, if a rotational speed Ωx on the xz plane or Ωy on one side of yz is applied, the piezoelectric materials (2, 2 'and 3, 3'; 102, 102 'and 103, 103') are respectively -2mVzΩX and -2mVzΩY (m is a piezoelectric material). The Coriolis force, expressed as mass of matter). This force causes tension or contraction to each piezoelectric material 2, 2 'or 3, 3'; 102, 102 'or 103, 103' and causes the piezoelectric material to generate charge. As described above, the biaxial rotation angle component signal detected by the piezoelectric material is represented as a final signal through the differential amplifier and the detection circuit. Here, two piezoelectric materials are polarized in the opposite direction to each other (for example, (2, 2 'or 3, 3'; 102, 102 'or 103, 103')]. Charge components due to humidity and the like cancel each other, and only the charge components due to the pure rotational speed are amplified twice and output. The sensing outputs of these amplifiers 54 to 60 are vector summed at the detectors 62 and 64 and output to the final control signal source.

According to the above configuration, the biaxial piezoelectric gyroscope according to the present invention is structurally stable and very easy to manufacture. In addition, even if the length of the piezoelectric body is increased, the entire size of the gyroscope does not increase.

Claims (4)

In a biaxial gyroscope using a plurality of piezoelectric materials, A cuboid metal base for grounding; A drive piezoelectric material attached to a lower surface of the metal base by a conductive adhesive, the drive piezoelectric material attached by a nonconductive adhesive such that a linear velocity direction of the drive piezoelectric material becomes a thickness direction of the drive piezoelectric material; And And a plurality of sensing piezoelectric materials attached to four sides of the metal base so as to be perpendicular to the linear velocity direction to sense a rotation angle with respect to a reference axis of two axes. 2. The apparatus of claim 1, further comprising: a waveform generator for applying a linear velocity to the drive piezoelectric material; An amplifier for amplifying the charge generated in the piezoelectric material for sensing; A detector for removing a frequency component of a drive signal from the signal generated by the amplifier and outputting only a signal for a rotational angular velocity; And a differential amplifier obtaining a signal proportional to the final rotational angular velocity based on the difference value of the signal generated by the detector. In a biaxial gyroscope using a plurality of piezoelectric materials, Metal plates for grounding; A driving piezoelectric material attached to either side of the metal plate by a conductive adhesive, the driving piezoelectric material being attached such that a linear velocity direction of the driving piezoelectric material becomes a thickness direction of the driving piezoelectric material; And At least four sensing piezoelectric materials, each corner of which is bonded with a non-conductive adhesive to the other side of the metal plate so as to be perpendicular to the linear velocity direction to sense a rotation angle with respect to the biaxial reference axis. 2-axis piezoelectric gyroscope. 2. The apparatus of claim 1, further comprising: a waveform generator for applying a linear velocity to the drive piezoelectric material; An amplifier for amplifying the charge generated in the piezoelectric material for sensing; A detector for removing a frequency component of a drive signal from the signal generated by the amplifier and outputting only a signal for a rotational angular velocity; And a differential amplifier obtaining a signal proportional to the final rotational angular velocity based on the difference value of the signal generated by the detector.