GB2215054A

GB2215054A - Oscillatory turn-sensitive device

Info

Publication number: GB2215054A
Application number: GB8803769A
Authority: GB
Inventors: Takahiro Oikawa
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 1988-02-19
Filing date: 1988-02-18
Publication date: 1989-09-13
Anticipated expiration: 2008-02-18
Also published as: DE3805250A1; GB8803769D0; DE3805250C2; GB2215054B

Abstract

An oscillatory angular speed detecting apparatus comprises a pillar-shaped oscillator body 1 and drive and readout piezoelectric transducers 2a, 2b attached to first and second side surfaces of the oscillator body, the first side surface being perpendicular to the second side surface. Oscillation of the oscillator body is transduced into a readout signal by the readout piezoelectric transducer 2b, and a phase detecting device 15 detects variations of phases of drive and readout signals, and an amplitude detecting device 18 detects variations of amplitudes of the readout signals. The angular speed is derived from these phases and amplitude. A feedback transducer 2c is used for generating the drive signal by circuits 10, 11, 12 and to provide a phase reference for the phase detector 15. The readout signal from the transducer 2b is amplified by an amplifier 16 and is passed to both the phase detector 15 and the amplitude detector 18. DC levels generated at converters 19, 20 are digitized and processed to provide a display signal. <IMAGE>

Description

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TITLE OF THE INVENTION

OSCILLATORY ANGULAR SPEED DETECTING APPARATUS BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an oscillatory angular speed detecting apparatus and, more particularly, to an oscillatory angular speed detecting apparatus, in which a displacement generated by a Coriolis force is transduced into an electric signal, and then an angular speed is detected from the electric signal.

Description of the Prior Art

In a conventional oscillatory angular speed detecting apparatus, a conventional detecting element shown in Fig. 4 is used. As shown in Fig. 4, the detecting element comprises a square-piller-shaped beam 1 functioning as an oscillator body, a drive piezoelectric transducer 2a attached to a central portion of a longitudinal surface la of the beam 1, and a readout piezoelectric transducer 2b attached to a central portion of another longitudinal surface lb of -, the beam 11, the surface lb being perpendicular to the surface la. The beam 1 is supported at fixed linear positions a and b by support members 3a and 3b, respectively. The beam 1 is driven in a sine wave form by applying a drive signal to the drive piezoelectric transducer 2a.

When an angular speed is added to the beam 1 around a central longitudinal axis Z of the beam 1, while the beam 1 is oscillated, the Coriolis force sinusoidally varying at an oscillation frequency is generated in the direction perpendicular to the drive surface la of the beam 1. This Coriolis force generates an oscillation having the same 1 - frequency as the drive frequency of the beam 1. The oscillation caused to the beam 1 by the Coriolis force is detected by the readout piezoelectric transducer 2b attached to the surface lb perpendicular to the drive surface la. of the beam 1. The detected signal is sent to a readout circuit (not shown).

- A feedback piezoelectric transducer 2c to be used for exciting the beam 1 at a mechanical resonance frequency while its amplitude is kept to a certain length, is attached to a central portion of another longitudinal surface lc of the beam 1 on the reverse side of the drive surface la in parallel therewith, and a damper piezoelectric transducer 2d is attached to a central portion of still another longitudinal surface ld of the beam 1 on the reverse side of the surface lb in parallel therewith.

In a conventional oscillatory angular speed detecting apparatus having the detector element described above with reference to Fig. 4, a signal amplitude-modulated at an angular speed, which is detected by the readout transducer is amplified, and then the amplified signal is demodulated.

Next, the demodulated signal is rectified, thereby obtaining a direct-current signal having a strength in proportion to the.Anput angular speed.

As described above, in the conventional angular speed detecting apparatus, the angular speed is detected by the strength of the direct-current signal which is obtained by demodulating the detection signal modulated in proportion to the angular speed, and a complicated signal processing is required in order to detect the direction of the input angular speed. Accordingly, its circuit structure becomes complicated.

In order to resolve this proble, the present applicant has proposed an oscillatory angular speed detecting apparatus. In this caser the angular speed is 2 - 11 1 1 i detected, not by using the amplitude variating corresponding to the angular speed, but by utilizing the phase which varies simultaneously with the amplitude and which is hard to be varied by disturbances such as a voltage and a temperature variation, and a positive or negative signal is adapted to be readily output depending on a lag or lead of the phase against a reference phase by the phase-comparison, with the result that the detection of the angular speed direction can be readily carried out, as disclosed in the Japanese Patent Laying-Open Specification No. 61-193019'. However, in this embodiment, an output having a sufficiently high level could not be obtained.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an oscillatory angular detecting apparatus which is capable of detecting an angular speed in a simple manner without a complicated signal processing, and of obtaining a sufficiently large output, and which can highly improve an ability of an angular speed detection.

In accordance with one aspect of the invention there is provided an oscillatory angular speed detecting apparatus comprising a pillar-shaped oscillator body, a drive piezoelectric transducer attached to a f irst side surface of the oscillator body, and a readout piezoelectric transducer attached to a second side surface perpendicular to the first side surface of the oscillator body, wherein an oscillation of the oscillator body driven by applying a drive signal to the drive piezoelectric transducer is transduced into a readout signal by the readout piezoelectric transducer and an angular speed is detected from the readout signal, the improvement' which comprises phase detecting means for detecting variations of phases of the drive and the readout signals, and amplitude detecting 3 - means for detecting variations of amplitudes of the readout signals, the angular speed being detected from the phases detected by the phase detecting means and the amplitudes detected by the amplitude detecting means.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages cf the present invention will more fully appear from the following description of the preferred embodiment -with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of an oscillatory angular speed detecting apparatus according to the present invention; 15 Figs. 2 and 3 are wave form charts for explaining an operation of the apparatus of Fig. 1; and Fig. 4 is a perspective view of a conventional detector element used in the apparatus of Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference to the preferred embodiment thereof, taken in connection with the accompanying drawings.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 an oscillatory angular speed detecting apparatus according to the present invention.

In Figs. 1 and 4, the drive piezoelectric transducer 2a and the feedback piezoelectric transducer 2c are so attached to the beam 1 that polarities of their piezoelectric elements may be reversed, and consequently, when the drive signal is applied to the drive piezoelectric transducer 2a, a feedback signal with a phase leading 90 0 - 4 as compared with that of the drive signal is output f rom the feedback piezoelectric transducer 2c.

The feedback signal is fed to an amplifier 10 for amplifying the feedback signal,- and then the amplified 5 feedback signal is supplied to an automatic gain controller 11, hereinafter referred to as ACC, in which the level of the - amplif ied feedback signal is maintained to a predetermined value. A stabilized feedback signal output from the ACC 11 is sent to a phase shifter 12 for shifting 10 the phase of the stabilized feedback signal.

A phase-shifted feedback signal output from the phase shifter 12 is applied as the drive signal to the drive piezoelectric transducer 2a and is also fed to a rectifier 13.

1 The rectified feedback signal is supplied from the rectifier 13 to one input of a comparator 14. In the comparator14, the rectified feedback signal is compared with a reference voltage VR applied to another input of the comparator 14, and a compared result is output from the comparator 14 to the AGC 11 in order to control the gain of the AGC 11. Accordingly, the AGC 11 can output the stabilized feedback signal whose level is maintained to a certain level corresponding to the reference voltage V RI and hence the drive of the beam 1 driven by the drive piezoelectric transducer 2a can be stably conducted always at a certain amplitude. The phase-shifted feedback signal is also applied as a reference phase signal from the phase shifter 12 to one input of a phase detector 15.

The readout signal output from the readout piezoelectric transducer 2b is fed to an amplifier 16 for amplifying the readout signal. An amplified readout signal is sent from the amplifier 16 to a. filter 17 for eliminating unnecessary components of the amplified readout signal, and a filtered readout signal' is fed to an amplitude detector 18 which detects an amplitude of the filtered readout signal and outputs an alternating current (AC) signal corresponding to the amplitude of the readout signal.

The amplified readout signal output from the amplifier 16 is also applied to another input of the phase detector 15 which compares the phase of the readout signal fed from the amplifier 16 with the phase of the reference phase signal.supplied from the phase shifter 12 and outputs an alternating current (AC) signal corresponding to the phase shift between the readout signal and the reference phase signal and to the direction of the phase shift.

The AC signals output from the phase detector 15 and the amplitude detector 18 are fed to alternating current-direct current, hereinafter referred to as AC/DC, converters 19 and 20, respectively, in which the AC signals are converted into direct current (DC) signals, and then the two DC' signals are sent to respective analog-digital, hereinafter referred to as A/D, converters 21 and 22 for converting analog signals into digital signals. The obtained digital signals are sent from the A/D converters 21 and 22 to a signal processor 23 comprising, for instance, a microcomputer, in which the digital signals are processed and the processing results are displayed on a display 24.

The operatipn of the above described oscillatory angular speed detecting apparatus according to the present invention will now be described in detail with reference to Figs. 2 and 3.

Firstly, a method for detecting the angular speed from the phase of the readout signal will be described. A wave form f F (t) of the drive signal to be applied to the drive piezoelectric transducer 2a is indicated by a solid line of Fig. 2a, and the drive piezoelectric transducer 2a drives the beam 1 in response to the drive signa'l and causes the beam 1 to oscillate corresponding to the wave form of the drive signal. The oscillation of the beam 1 is stabilized X 1 by the AGC 11. A wave form fp,(t) indicated by a one-dotted line Of Fig. 2a is an oscillatory wave form of the readout signal read out of the readout piezoelectric transducer 2b when no rotational force is added to the beam 1. As apparent from the comparison between these two wave forms, the phase of the readout signal is shifted 900 from that of the drive signal.

Now, when a rotational force is added to the beam 1 in the clockwise direction and an angular speed w I is input to the beam 1, the readout piezoelectric transducer 2b outputs a readout signal havihg a wave form f pwl(t) indicated by a broken line of Fig. 2a. On the other hand, when a rotational force is added to the beam 1 in the counterclockwise direction and an angular speed -w2 is input to the beam 1, the phase of the readout signal is shifted in the reverse direction to that of the clockwise rotation, and the readout piezoelectric transducer 2b outputs a readout signal having a wave form f pw2(t) indicated by another broken line of Fig. 2a.

The drive signal f F (t) and the three readout signals fpo(t), fpWl (t) and fp,2(t) are fed to the phase detector where these waves are shaped to rectangular wave forms of signals f F(t)' f po (t)" f pwl (t), and f pw2(t)" respectively, as,shown in Fig. 2b. Then, the rectangular wave signal f F (t)' is compared with each of the rectangular wave signals f (t) I, f (t) I and f (t)' and the same po. pwl pw2 polarity portions of each pair of the rectangular wave signals are picked up, with the result that the phase detector 15 outputs three compared rectangular wave signals shown in Fig. 2c. In Fig. 2c, the wave signal indicated by a solid line is obtained from the two wave signals f F(t), and f po(t)1 and each of the other wave signals indicated by broken lines is obtained from the two waVe signals f F(t) I and f pwl (t) I., or f F (t) I and f pw2 (t) ' - It is readily understood from Fig. 2c that the continuous times of the positive and negative levels of each of the rectangular wave signals as to when the rotational forces are added, increase or decrease from those of the rectangular wave signal as to when no rotational force is added.

The rectangular wave signals shown in Fig. 2c are fed to the AC/DC converter 19, in which the full-wave rectifications of the rectangular wave signals - are performed to obtain signals having wave forms shown in Fig. 2d, and then the full-wave rectified signals are smoothed to obtain smoothed DC signals shown in Fig. 2e. In Fig. 2e, V 01 shows the level of the DC signal as to when no rotational force added. Then, the smoothed DC signals are so converted into other DC signals shown in Fig. 2f that the level V 01 of the DC signal may be changed- to the nought level, and the converted DC signals shown in Fig. 2f are output from the AC/DC converter 19. In Fig. 2f, there are shown two DC signals V 1 and V 2 as to when the rotational force is added to the beam 1 in the clockwise or the counterclockwise direction, respectively, and the output levels of the DC signals V 1 and V2 are V W1 and V w2' respectively. Therefore, the strengths and directions of the angular speeds can be detected by the strengths of the output levels V W1 and V w2 and the polarities thereof.

Secondly, a,, method for detecting the angular speed from the amplitude of the readout signal will be described. There are shown in Fig.. 3a three wave forms f po (t), f pwl(t) and fpw2 (t) of the readout signals, as indicated by a solid line and two broken linesl when no rotational force is added to the beam 1, when a rotational f orce is added to the beam 1 in the clockwise direction, and when a rotational force is added to the beam 1 in the counterclockwise direction, respectively. In this case, since it is unnecessary to consider the differences of the phases of these signals in detecting the amplitudes, the three wave forms are shown in the same phase, as shown in i:

R Fig. 3a, for reasons of convenience. However, in fact, the phases of the signals are often different from one another, as shown in Fig. 2a. Further, the amplitude variations of the signals are not always f ixed to f pwl (t) > f po (t) > f pw2 (t), as shown Fig. 3a, and vice versa. The amplitudes of the wave f orms f pwl (t) and f pw2 (t) may be larger or smaller than that of the wave form f Po(t).

The readout signals having the wave forms shown in Fig. 3a are fed from the readout piezoelectric transducer 2b to the amplitude detector 18 for detecting the aplitudes of the readout signals via the amplifier 16 and the filter 17, and then the readout signals are sent from the amplitude detector 18 to the AC/DC converter 20. In the AC/DC converter 20, the full-wave rectifications of such signals are carried out, thereby resulting rectified signals shown in Fig. 3b. Then, the rectified signals are flattened to obtain DC signals shown in Fig. 3c. Next, the flattened DC signals are so converted into other DC signals shown in Fig. 3d that the level V 02 of the DC signal as to when no rotational force is added, may be changed to the nought level, and the converted DC s ignals of Fig. 3d are output from-the AC/DC converter 20.

In Fig. 3d, there are shown two DC signals V 1 1 and V 2 as to when the rotational forces are added to the beam 1 in the clockwise and the counterclockwise directionSr respectively, and the output levels of the DC signals V11 and V 2' are V 1 1 and V 2 1 1 respectively.

W W Hence, the strengths of the angular speeds can be detected by the striBngths of the output levels V Wil and V w2' Further, when the amplitude variations of the readout signals which are obtained when the rotational forces are added to the beam 1 in the clockwise and the counterclockwise directions, one is larger and the other is smaller than that of the readout signal which is obtained when no rotational force is added to the beam 11 as shown in - 9 Fig. 3a, the directions of the angular speeds can be simultaneously detected by the polarities of the output levels V Wil and V w2" as well.

In this embodiment, however, when the amplitude variations of the signals f PW1 (t) and f pw2 (t) are both larger or smaller than that of the signal fpo (t), the directions of the angular speeds cannot be detected.

The DC signals output from the AC/DC converters 19 and 20 are fed to the respective A/D converters 21 and 22 in order to convert the DC signals into digital signals, and the digital signals are then sent to the signal processor 23. In the signal processor 23, the absolute values of the output signals of the A/D converters 21 and 22 are added, and the strengths of the angular speeds are detected on the basis of the added values. Further, the directions of the angular speeds are detected by the polarities of the output signals of the A/D converter 21. As described-above, since the strengths of the angular speeds can be obtained from Ivwll + IV.111 and IV w2 I + I Vw2' 1, the obtained values are the portions IVwl1I and IV w2' I larger than Vwl I and V w2 I as compared with the first embodiment in which the strengths of the angular speeds are detected from the phase of the readout signal, and therefore the more accurate angular,speed detection may be performed in this embodiment.

It is readily understood from the above description of the preferred embodiment, that according to the present invention, since the angular speeds are detected from the phases and the amplitudes of the readout signals read out of the readout piezoelectric transducer attached to the oscillator body, the large signals representing the strengths of the angular speeds can be obtained, and the detection ability of the angular speeds' can be highly improved. Further, according to the present invention, the directions of the angular speeds may be detected f rom the A 1 1 phases in a simple manner without a complicated signal processing.

Although the present invention has been described in its preferred embodiment with reference to the accompanying drawings, however, it is readily understood that the various changes and modification of the present invention may - be made by a person skilled in the art without departing from the spirit and scope of the present invention.

X b

Claims

1. In an oscillatory angular speed detecting apparatus comprising: 5 a pillar-shaped oscillator body; a drive piezoelectric transducer attached to a f irst side-surface of the oscillator body; and a readout piezoelectric transducer attached to a second side surface perpendicular to the first side surface of the oscillator body, wherein an oscillation of the oscillator body driven by applying a drive signal to the drive piezoelectric transducer is transduced into a readout signal by the readout piezoelectric transducer and an angular speed is detected from the readout signal, the improvement which comprises: phase detecting means for detecting variations of phases of the drive and the readout signals; and amplitude detecting means for detecting variations of amplitudes of the readout signals, the angular speed being detected from the phases detected by the phase detecting means and the amplitudes detected by the amplitude detecting means.

2. The apparatup as defined in claim 1, wherein the phase detecting means detect the angular speed from the drive signal, and a first readout signal obtained when no rotational force is added to the oscillator body, and a second readout signal obtained when a rotational force is - added to the oscillator body, and the amplitude detecting means detect the angular speed from the first readout signal and the second readout signal.

3. The apparatus as defined in claim 2, herein the phase detecting means compare the drive signal with the first and the second readout signals, respectively, to obtain first i 1 and second compared readout signals, and compare the phases -of the f irst and the second compared readout signals, the angular speed being detected from the difference of the phases of the first and the second compared readout signals, and wherein the amplitude detecting means compare the amplitudes of the first and the second readout signals, the angular speed being detected from the difference of the amplitudes of the first and the second readout signals.

4. The apparatus as defined in claim 3, wherein the phase. detecting means shape the drive signal, the f irst readout signal and the second readout signal to rectangular wave forms to obtain a drive rectangular signal, a first rectangular readout signal and a second rectangular readout signal, respectively, pick up the same polarity portions of the drive 'rectangular signal and the f irst rectangular readout signal and of the drive rectangular signal and the second rectangular readout signal to obtain first and second compared rectangular signals, conduct full-wave rectifications of the first and the second compared rectangular signals, smooth first and second rectified rectangular signals, to obtain f irst and second DC signals, and convert the DC signals so that the level of the f irst DC signal may be, nought level to obtain f irst and second converted DC signals, a strength and a direction of the angular speed being detected from a strength of the output level of the second converted DC signal and a polarity thereof, respectively, and wherein the amplitude detecting means conduct full-wave rectifications of the first readout signal and the second readout signal to obtain third and fourth rectified signals, smooth the third and the fourth rectified signals to obtain third and fourth DC signals, and convert these DC signals so that the leVel of the third DC signal may be nought level to obtain third and fourth converted DC signals, a strength and a direction of the angular speed being detected f rom a strength of an output level of the fourth converted DC signal and a polarity thereof, respectively.

5. The apparatus as defined in claim 4, wherein the phase detecting means comprises a phase detector and an AC/DC converter, and wherein the amplitude detecting means comprises an amplitude detector and an AC/DC converter.

6. An oscillatory angular speed detecting apparatus substantially as hereinbefore described with reference to, and as shown in, Figures 1, 2 and 3 of the accompanying

7. herein.

Any-novel feature or combination of features described 1 1 - 14 A hed 1989 atThe Patent Office.State House, 66.71 High Holborn, LondonWC1R4TP. Further copies maybe obtained from The Patent Office. Sales Branch, St Mary Cray. Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87 11