JPS60239613A - Angular velocity sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The angular velocity of an aircraft's motion is an important input to all navigation and inertial guidance systems. Such devices are commonly used on aircraft, spacecraft, ships, or missiles. Sensing the angular rate of motion is currently done by gyroscopes. .

However, nogyroscopes have various drawbacks. Gyroscopes must be made to extremely high precision, but can have a drift rate of less than 1 degree per hour. Due to the cost of making a gyroscope, it is very expensive, physically large and heavy. Gyroscopes require frequent and precise maintenance because important moving elements such as bearings change over time. Gyroscopes can also be damaged by low levels of shock and vibration. For this reason, an increase in the drift rate of an unknown magnitude may occur at an unknown time. - Since gyroscopes are susceptible to shock and vibration, heavy mounting structures are often used to protect them, which are also expensive.

It is therefore obvious that it would be desirable to replace the gyroscope by some other device which is less expensive and capable of measuring angular velocity and thus measuring vehicle or aircraft-like attitude. The present invention has a resonant structure of quartz having piezoelectric properties, the structure has at least two vibrating elements, each element is composed of two substantially parallel prongs and a common yuzu, and the two prongs and The axes are arranged in one plane, a common cypress acts as an output axis, and the coffin becomes a balanced resonant sensing device that responds only to angular movements about an axis parallel to the output axis, and the output axis is twisted and electromagnetic means coupled to said two prongs for causing said two prongs to vibrate at a driving frequency; and electromagnetic means coupled to said output shaft to produce an angular velocity of motion about said axis experienced by the device. and an output means for extracting an electrical signal representing the angular velocity sensing device.

Preferably, the sensing device is a tuning fork. The tuning fork should be mechanically stable with respect to temperature, have low internal friction, and comply with Hooke's law. Preferably, the tuning fork is made of quartz, but does not necessarily have to be made of quartz. However, synthetic crystals such as ethylene diamine tartrate (EDT), dipotassium tartrate (1) KT) or diphosphoric acid
Other piezoelectric materials such as ammonium hydrogen (ADP) can also be used. Non-piezoelectric materials can also be used with piezoelectric drives.

The tuning fork is preferably constructed from an insulating material such as quartz, but conductive materials can also be used. In this case, the two of the tuning forks must be excited or electromagnetically, ie by a stationary coil and a magnetic device mounted on the two forks.

A tuning fork consists of two forks that are arranged parallel to each other and can vibrate. The two prongs are interconnected by an output shaft or handle from which an output signal can be extracted. The output signal represents the angular velocity of the motion input experienced by the device. This produces a deflection perpendicular to the direction of vibration. It is also possible to obtain an optically modulated or frequency modulated output signal.

The output signal can be tapped off by coupling two or four capacitors to the output shaft, or piezoelectrically, resistively or optically. The measurable input velocity of the sensing device of the present invention, on the order of 10 degrees per hour, is low enough to serve as a magnetically corrected directional reference as well as a gravity corrected vertical attitude reference. 0
．． If an input velocity of 1°/hour can be measured, the device can be used as an inertial plate reference, such as a self-contained inertial guidance device.

Although novel features considered to be unique to this invention are specifically described in the claims, the structure, operation, and other objects and advantages of this invention itself can best be understood from the following description of the drawings. It will be.

A simple tuning fork is shown in FIGS. 1 and 2 to explain the operations Ig and Ig of the present invention. As mentioned before,
Tuning fork 10 is made of a synthetic crystal, preferably a piezoelectric material such as quartz. Figures 1 and 2 show two prongs 11.1.
2 and an output shaft or handle 13 are shown. As will be explained later with reference to FIGS. 4 to 6, the forks can be made to vibrate by applying an electric field.

A pair of electrodes 14, shown at 11, spaced from the free end of each of the two prongs, are shown in FIG. 2 and provide a capacitive output. At this time, they oscillate toward each other as shown by 2 or arrow 15, and in the next half cycle, to move away from each other as shown by arrow 16. Therefore, 2
Since the forks 11 and 12 are balanced, the tuning fork represents a balanced resonant circuit. Another pair of electrodes 17.18, which can be applied directly to the area between the two prongs 11.12 and the output shaft 13, makes it possible to extract the electrical power. Due to the deflection of the tuning fork 10 caused by the angular movement of the device, the two electrodes 17, 18
have different polarities. Once the angular motion is applied, the time derivative, ie the angular motion of the motion, is easily obtained.

In this case, the distance from the center of movement of the tuning fork to the end of fork 11 is 0.
．． 5 cm, or the distance of the part covered by the electrode 14 among the prongs is 0.2 cm, the distance from the center of movement to the center of the electrode 14 is 0.4 cm, the width of each prong is 0.05 cm,
The thickness of each fork is 0.005 cm, and the half amplitude of vibration is 0.005 cm.
00025 cm, the driving frequency is 10 kHz, and the density of quartz is 2.6 gm/cτc3. Under these assumptions, the angular momentum can be calculated as follows6 1 (=6,53X10 g+ocm2/sec (1) Similarly, the torque T can be calculated as follows.

T"1,89X10-'gmcm (2) Finally, the deflection of the two forks is Y=1.62X10-'cm (3) At this time, the effect of increasing the dimension without changing the width of the tuning fork is N become,
It can be shown that this is proportional to the increase in size to the fifth power. Therefore, the calculation will be as shown in the table below.

TABLE-L Nl 2 3 4 5 N51 32 243 1024 3125It is therefore clearly seen from Table 1 that increasing the dimensions of the tuning fork significantly increases the deflection of the fork.

Next, Figures 3 to 19 will be explained in general.
In particular, FIGS. 3 through 6 show preferred embodiments of the invention. This embodiment includes two tuning forks, the two axes of which are arranged parallel to and spaced apart from the central axis. That is, the first fork 20 of a pair of tuning forks.
20' is composed of one section 22. The section 22 is divided into two parts constituting the two tuning forks 20.21 by a gap 23, which leaves a small bridge 24 interconnecting the two parts 20.2. The other section 22' is exactly symmetrical to section 22 and forms h1 the other fork 20°, 21' of the two tuning forks.

The two ends of each of the two sections 22, 22' are interconnected by interconnecting members 25', 25'. The part 25 is divided into two sections 22.2 by two gaps 26.28'.
It is separated from 2'. The other interconnection member 25' is likewise separated from the two sections 22, 22'.

Two interconnecting members 25, 25' form an output shaft.

These are both connected by small bridges 27.27' to the surrounding frame 30, which is divided into two sections 22.27'.
22'. As shown in FIG. 4, the tuning fork can be surrounded by three casings. That is, the portions 20, 20' form a pair of forks, and the portions 2 j , 21
' forms the other tuning fork.

FIG. 5 shows electrodes that can be provided at the ends of a pair of forks 20, 20' of a tuning fork. The fork 20 has one electrode 32, . It has 33. Similarly, the fork 20'' has one electrode 34 + 35. One inner surface of the casing 31 has a similar electrode 36 and the other or opposite inner surface has an electrode 37.

A sensing oscillator 38 is connected to two inner electrodes 36,37 provided on the casing 31. For this reason, electrode 37.3
A capacitance 40 is formed between the two.

Another capacitance 41 is formed across the electrodes 33.36.

A third capacitor 42 is formed between electrodes 34, 37 and a fourth capacitor 43 is formed between electrodes 35, 36.

The output of the bridge circuit of FIG. 6 can be read by meter 44.

The output circuit of the capacitive bridge of FIG. 6 is shown in FIG. tj&8. The driving oscillator 46 can be multiplied by a multiplier 47. The signal from meter 44 can be amplified using the nine-bridge amplifier 48 whose driving oscillator is used in the sensing device of FIG.

After this, the phase detector 50 is used. This phase detector is
Kakeru! A reference phase from multiplier 47 coupled to IIJJ oscillator 46 is used. After the phase detector, γ wave detector 5 and Δ
A /D converter 52 follows, which converter includes a microprocessor, a linearizer, a display driver and a to/11 converter 53.
supply a signal to. Therefore, the output signal g can be obtained from either digital output lead a54 or analog output lead #1I55 and applied to a suitable display device.

Figure PS7 shows an enlarged view of a portion of the sensing device of Figure 3 and its electrodes. A pair of drive types +M60.61 are also arranged on 20. Two drive electrodes conductive m13
2 and 133, respectively, and these conductors are connected to a driving oscillator. The two electrodes are slightly separated from each other and set up an electric field that causes the forks to vibrate. The other fork 20' has a similar electrode 60'.

61', which are connected to output conductors 62' and 63'. Conductor 62. f32' are joined together
Ru.

A pick-up electrode 64 is connected to another pick-up electrode 65 also located on the fork 20.

Output electrodes 64,65 are connected to conductor #i66 and frame 30. The other fork 20' has a similar output electrode.

It will be appreciated that the output electrodes 64,64' are located directly on the capacitor and produce a capacitive output as shown in FIG. One output electrode such as 62.63 can be grounded.

A piezoelectric output circuit for the electrode of FIG. 13 is shown in FIG. In this case as well, the drive oscillator 46 is
．． 91 to the balanced type button device of FIGS. 3 and 13.
energize. In this case, due to the distortion of the crystal due to the bending of the prongs, a piezoelectric voltage appears at the electrode 96 and its corresponding invisible electrode. The buffer amplifier 67 is shown in FIGS. 133 and 13.
After the sensing device in the figure, there is a phase detector 50, γ
A wave converter 51, a ^/D converter 52 and a D/^ converter 53 follow. This provides a digital signal or an analog signal (g) on the output conductor 54.55.
8 (see Figure 3), the mass of the prongs can be increased to allow for lower resonant frequencies.

The resonant frequency of the prongs in the direction of output deflection can be equal to the frequency of the drive signal. For this reason, the resonance frequency depends on the mass of the prongs as shown in 20.21 and the gap 23.
26 dimensions. Therefore, these values can be adjusted arbitrarily.

Another form of sensing device according to the invention is shown in FIGS. 10 and 11. As clearly shown in FIG. 10, the sensing device consists of two tuning forks 70.71 arranged on a common axis, perpendicular to the output shaft 72.

Preferably, the output shaft 72 is fixed between two walls 73,74. A substantially rectangular open lower portion 5.7 symmetrical to the output shaft 72
5" to mainly reduce the weight of the output shaft and reduce its rigidity. As a result, the output shaft 7
2's resonant frequency decreases. Therefore, the output shaft 72 also acts as a pair of tuning forks.

FIG. 11 shows the polarity of the output voltage at curves 97B and 771, ie, on both sides of the output shaft 72.

Figures 12 and 13 show another form of sensing device of the invention, which uses two pairs of tuning forks.

As clearly shown in Figure vJ12, the first
There is a pair of tuning forks FI 3.84, and a second pair of tuning forks 85.86, tI, also having a common axis. The two axes are spaced from the output shaft 87. Two pairs of tuning forks are connected to the output shaft 87 by a connecting member 88. FIG. 13 shows, as an example, how to drive a tuning fork.

Input leads 90.91 from the drive oscillator are connected such that input leads 9 go to tuning fork 83.84. At the same time, the lower casing 95 of the upper casing 94 is energized by the human power conductor 90, so that the casing 94.95 and the tuning fork 83.8
Generates an electric field at the opening of 4.

One output or pickup electrode 96 is connected to the interconnection portion 8
It can be placed on 8. The other output electrode is electrode 9
6 and cannot be seen in Figure 13.

The sensing device of FIG. 14 has two pairs of four tuning forks each. That is, the first set of tuning forks 100°101.102
．． 103 have a common axis. The four tuning forks 100 to 103 in the ft52 set also have a common axis, but are separated from the output shaft 105. The output shaft 105 can also be provided with a rectangular notch 106 at each end to reduce its weight and stiffness and thus lower its resonant frequency. Tuning forks such as 100-103 are separated from the output shaft by large gaps 107, 10B, 110. The output shaft 105 is also connected to two walls 111.11
It can be placed between 2.

The phase can be shifted by twisting the output shaft 105 in advance. That is, by applying stress in advance, the direction of angular motion is detected in addition to the angular velocity. Therefore, output shaft 105 can be used to generate an output frequency that may be higher than the drive frequency. The same is true for the output shaft 72 in FIG.

It should be noted that the electrodes are preferably constructed with gold plating. The two prongs of each tuning fork can be balanced by laser treatment. That is, the laser can ablate a suitable portion of one prong electrode. This increases the Q of the circuit.

What has been described above is an angular velocity sensing device essentially consisting of a tuning fork energized by a drive oscillator.

Angular movement of the device causes deflection of the output shaft perpendicular to the direction of vibration. This deflection can be measured by voltages generated by capacitive, resistive, or piezoelectric effects. A frequency modulated output signal can be obtained, or an optical pickup can be used. Various types with multiple tuning forks have been described. A preferred arrangement is capable of controlling the frequency of the output signal relative to the vibrations of the sensing device. This angular rate sensing device can be manufactured using semiconductor technology much more cheaply than ordinary nogyroscopes. In addition to being cheap to manufacture, its accuracy makes it practical for use as an inertial reference, either magnetically or compensated for gravity, as an orientation and attitude reference, or as a self-contained inertial guidance system. This should be sufficient for most uses.

[Brief explanation of drawings]

FIG. 1 is a plan view of a tuning fork for detailed explanation of this invention.
FIG. 2 is a side view of the tuning fork of FIG. 1, showing two pairs of electrodes from which output signals are extracted. FIG. 3 is a plan view of a preferred embodiment of the invention having two tuning forks, with the casing omitted. FIG. 4 is a cross-sectional view of the embodiment of FIG. 3, showing the casing surrounding the tuning fork. Figure 5 is #15- in Figure 3.
5 shows the casing and the capacitive output that can be used in a bridge circuit. Fig. 6 is a circuit diagram showing the capacitive bridge obtained by the electrode device of Fig. 5, and Fig. 7 is an enlarged plan view of a portion of the sensing device of Fig. m3, including the drive wire from the sensing device of Fig. ptS3. and output electrodes are shown. rjS8
This figure is a block diagram of the output circuit of the bridge circuit of FIG. 7, and FIG. 9 is a block diagram similar to the ilB diagram, but shows the piezoelectric output obtained by the electrodes in the form of FIG. 13. FIG. 10 is a plan view of another angular velocity sensing device consisting of two tuning forks arranged one straight above the output axis in the normal direction;
Figure 1 schematically shows the voltage generated on the output shaft due to rIi mechanical deformation, and Figure ttS12 shows each pair of tuning forks being in a straight line and two pairs being arranged parallel to the output shaft. FIG. 13--FIG. 13 is an enlarged view of a portion of the sensing device of FIG. 12 showing one pick-up electrode along with the drive electrode. Figure tIS14 shows a further example of the sensing device of the present invention having eight tuning forks, in which four tuning forks are arranged on the same axis, and the respective axes of the two sets of tuning forks are arranged parallel to the axis of the output shaft. FIG.

[Explanation of main symbols]

20.20', 21.2 j': Tuning fork 25.2
5': Output shaft 32.33.34.35.36.37: Electric 1 color 38=
Oscillator 44: Engraving of instrument drawings (no changes in content) Fig, / Fia, 11° procedural amendment (voluntary) July 18, 1980 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case 1982 Patent Application No. 94759 2, Title of the invention: Angular velocity sensing device 3, Relationship with the 7 persons making the correction: Applicant Name: Piezo Electric Technology Investors Limited 4, Agent: 5, Date of amendment order: Showa year/month Date (voluntary) 6, Subject of amendment (1) Column for the representative of the applicant (2) Cleaning of all drawings (however, there are no changes to the contents) (3) Power of attorney and translation 7, Attachment to the contents of the amendment street

Claims (1)

[Claims] (1) The structure has resonance *i of quartz having piezoelectric properties, and the structure has at least two vibrating elements, each element consisting of two substantially parallel prongs and a common axis, The two prongs and the yuzu are arranged in one plane, the common yuzu acts as an output axis, and the withers respond only to angular movement about an axis parallel to the output axis to produce balanced resonance. an electromagnetic means for causing a torsional deflection on the output shaft; and an electromagnetic means coupled to the two prongs for causing the two prongs to vibrate at a driving frequency; an angular rate sensing device, comprising output means for extracting an electrical signal representative of the angular rate of movement about said axis experienced by the device. (2. In the angular velocity sensing device according to claim 1, the vibration element is disposed symmetrically with respect to the output axis, and is spaced apart from the output axis substantially parallel to the angular velocity sensing device. (3) In the angular velocity sensing device according to claim 1, the vibrating element is arranged symmetrically with respect to the output axis and substantially perpendicular to the output axis. (4) In the angular velocity sensing device according to claim 3, the element and the output shaft are composed of a quartz tuning fork having piezoelectric properties, and the tuning fork or the output shaft is a balanced resonant sensing device that responds only to angular motion about an axis parallel to
An angular rate sensing device for causing torsional deflection of said output shaft, said output means including a phase detector for said electrical signal and means for generating an output signal representative of the angular rate of motion. (5) In the angular velocity sensing device according to claim @4, the electromagnetic means includes a driving oscillator, a first electrode connected to each of the two prongs, and a fixed portion separated from the mi electrodes. An angular rate sensing device including an electrode, the electrode being coupled to the oscillator. (6) In the angular velocity sensing device according to claim 5, the output means has a pair of output electrodes provided on the output shaft for each of the two prongs, and generating an electrical signal indicative of deflection of said shaft due to movement;
An angular rate sensing device, wherein a pair of output electrodes are coupled to the phase detector. (7) In the angular velocity sensing device according to claim 6, the output electrode is connected to the phase detector,
An angular velocity sensing device, wherein the phase detector is connected to the drive oscillator to take out the output signal. (8) In the angular velocity sensing device according to claims tIS4 to @7, two tuning forks are provided, the tuning forks are arranged substantially in a normal direction to the output shaft, and the tuning forks are disposed in a substantially normal direction to the output shaft, an angular rate sensing device disposed between two substantially fixed elements; (9) In the angular velocity sensing device according to claims 4 to 7, four tuning forks are provided, each pair of tuning forks is arranged along a common axis, and each axis is connected to the output. An angular rate sensing device parallel to an axis, the output axis being disposed between two substantially stationary elements. (10) The angular velocity sensing device according to claim 119, wherein the electromagnetic means includes a drive electrode for two prongs of each tuning fork, and a drive oscillator having two output conductors for the drive electrode. The drive electrodes of each of the two forks of the pair of tuning forks are connected to the opposite conductor of the drive oscillator, and the drive electrode of each of the other pair of tuning forks is connected to the conductor of the drive oscillator. This is an angular velocity sensing device that vibrates in the opposite phase to the first pair of tuning forks. (11) In the angular velocity sensing device according to claims 4 to 7, eight tuning forks are provided, four tuning forks have a common first axis, and the remaining four tuning forks have a common first axis. The two tuning forks have 12 common axes, the first and second axes are parallel to and approximately equidistant from the common glaze, and the common axis is approximately the same length as the axes. An angular rate sensing device, wherein the common axis is arranged between two substantially fixed elements that are parallel. (12) It has an integral element of quartz with two approximately parallel sections, each section having a center gap of f:tSl, and a small bridge section between the two sections of each section. leave,
each section forming a fork of a tuning fork, each end of said section being interconnected by an interconnecting member forming an output shaft;
each member is spaced apart from its associated section by a second gap, leaving a small bridge between each member and its associated section, the gap controlling the inertia and frequency of the sensing device input; For this purpose, the dimensions of said gap and said parts and the masses of said sections, said parts and parts determine the resonant frequency of said fork and the angular velocity of the output signal representative of the angular velocity of the movement experienced by said sensing device. Sensing device. (13) In the angular velocity sensing device according to claim 12, a casing is provided, a pair of drive electrodes are provided on each prong, and an output electrode is provided on each prong to suppress the deflection of the prong. an angular velocity sensing device for extracting an electrical signal representing the angular velocity, the casing being spaced from the electrode; (14) In the angular velocity sensing device according to claim rIS 13, a pair of inner electrodes are provided on the inner surface of the casing for each tuning fork, and the inner electrodes are coupled to a drive oscillator. Sensing device. (15) The angular velocity sensing device according to claim ttS14, wherein the casing is etched to receive the electrode. (16) An angular velocity sensing device according to claims @1 to 15, in which the output shaft is twisted in advance to generate an output signal representing the direction of angular movement. (17) The angular velocity sensing device according to claim 16, wherein the output shaft is provided with at least one substantially rectangular notch to reduce its gravity and rigidity.