Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-11-02
2002-11-12
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06477897
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vibrating gyroscopes and, more specifically, it relates to vibrating gyroscopes for use in camera-shake corrections, navigation systems, vehicle-posture control, and the like.
2. Description of the Related Art
FIG. 10
is an illustration showing an example of a conventional vibrating gyroscope
1
. The vibrating gyroscope
1
includes a rectangular-parallelepiped vibrator
2
. The vibrator
2
is formed by laminating two planar piezoelectric members
3
a
and
3
b
. The piezoelectric members
3
a
and
3
b
are polarized in directions opposing each other. Between the piezoelectric members
3
a
and
3
b
, an intermediate electrode
4
is formed. In addition, on one main surface of the piezoelectric member
3
a
, detection electrodes
5
a
and
5
b
, which are two-split parts, are formed. Furthermore, on the entire other main surface of the piezoelectric member
3
b
, a drive electrode
6
is formed.
In order to use the vibrating gyroscope
1
, the detection electrodes
5
a
and
5
b
are connected to an adding circuit
7
. The adding circuit
7
is connected to a gain control circuit (AGC circuit)
8
. The AGC circuit
8
is connected to a phase circuit
9
. A signal output from the phase circuit
9
is input to the drive electrode
6
. The adding circuit
7
, the AGC circuit
8
, and the phase circuit
9
form a drive circuit. In addition, the detection electrodes
5
a
and
5
b
are connected to a differential circuit
10
. The differential circuit
10
is connected to a synchronous detection circuit
11
. A signal output from the differential circuit
10
is detected in synch with the signal of the AGC circuit
8
. In addition, The synchronous detection circuit
11
is connected to a smoothing circuit
12
, which is connected to a DC amplifying circuit
13
.
In the vibrating gyroscope
1
, by vibration of the vibrator
2
, signals output from the detection electrodes
5
a
and
5
b
are added by the adding circuit
7
, and the added signal is amplified by the AGC circuit
8
so as to make the amplitude of the signal constant. After this, the amplified signal is phase-adjusted by the phase circuit
9
. The driving signal obtained in this way is input to the drive electrode
6
, whereby the vibrating gyroscope
1
is self-excited. As a result, the vibrator
2
performs bending-vibration in a direction orthogonal to the drive electrode
6
.
From the detection electrodes
5
a
and
5
b
, signals in accordance with the bending-vibration of the vibrator
2
are output. When the vibrating gyroscope
1
does not rotate, the bending conditions of the parts where the detection electrodes
5
a
and
5
b
are formed remain unchanged. Thus, the same signal from each of the two detection electrodes
5
a
and
5
b
is output. Therefore, the output of the differential circuit
10
becomes zero. When a rotation angular velocity is added around the center axis of the vibrator
2
, Coriolis force causes a difference in the bending-vibration conditions between the part where the detection electrode
5
a
is formed and the part where the detection electrode
5
b
is formed. As a result, the detection electrodes
5
a
and
5
b
output different signals. Thus, the differential circuit
10
outputs a signal in accordance with the difference between the signals output from the detection electrodes
5
a
and
5
b
. After the signal is detected by the synchronous detection circuit
11
and smoothed by the smoothing circuit
12
, the signal is amplified by the DC amplifying circuit
13
, with the result that a DC signal in accordance with the rotation angular velocity can be obtained. Therefore, by measuring the signal output from the DC amplifying circuit
13
, the rotation angular velocity added to the vibrating gyroscope
1
can be detected.
Regarding the use of the vibrating gyroscope
1
, when a reference potential is used to secure a stable operation, the intermediate electrode
4
disposed between the piezoelectric members
3
a
and
3
b
is connected to the reference potential.
An equivalent circuit for representing the driving detection circuit of the vibrating gyroscope
1
is a circuit as shown in FIG.
11
. In this equivalent circuit, the symbol Vdrv denotes a circuit driving voltage, the symbol Rd denotes a drive resistance, the symbol Z denotes a vibrator characteristic impedance, the symbol Rs denotes a detection resistance, and the symbol Vs denotes a detection voltage. As shown in the equivalent circuit, the detection voltage Vs is determined by the partial-potential ratio between Rd, Z, and Rs. However, when the values of Rd, Z, and Rs change due to changes in external environments and changes with the elapse of time, the value of Vs also changes. Thus, when changes in the detection voltage occur due to changes in the external environments and changes with the elapse of time, a rotation angular velocity cannot be accurately detected.
In addition, when the intermediate electrode is connected to the reference potential to secure a stable operation, it is necessary to lead out a wiring pattern from the intermediate electrode. However, in order to lead out the wiring pattern from a thin intermediate electrode, the structure must become complicated, with the result that having such a structure is not advantageous in terms of processing accuracy and cost.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a vibrating gyroscope capable of being connected to a reference potential with a simple structure and suppressing changes in a detection signal due to changes in external environments and changes with the elapse of time.
The present invention provides a vibrating gyroscope including a vibrator on which a plurality of piezoelectric members polarized in directions opposing each other is laminated, at least one drive electrode formed on one of the mutually opposing main surfaces of the vibrator to input a signal for exciting the vibrator, at least two detection electrodes formed on one of the mutually opposing main surfaces of the vibrator to output a signal in accordance with vibration of the vibrator, and at least one reference electrode formed on one of the mutually opposing main surfaces of the vibrator to be connected to a reference potential. In this vibrating gyroscope, the reference electrode is formed in a position opposing the drive electrodes and the detection electrodes.
In this vibrating gyroscope, the drive electrodes and the detection electrodes may be formed on the same main surface of the vibrator or may be formed on different main surfaces of the vibrator.
Furthermore, the detection electrodes may be connected to a charging amplifier for converting a generated charge into a voltage to detect a rotation angular velocity input from a differential signal of the output of the charging amplifier.
By connecting the reference potential formed in the position opposing the drive electrodes and the detection electrodes to the reference potential of the driving detection circuit, electrical isolation between the driving side and the detecting side can be facilitated. As a result, influence of changes in the drive resistance of the driving side becomes less. Additionally, a signal-detection reference can be defined so that accurate signal detection can be performed. As a result, the condition of a vibrator like the AGC circuit can be accurately monitored.
Furthermore, since the input impedance of the charging amplifier for converting changes in a charge into a voltage is zero, by connecting the detection electrodes to the charging amplifying, the voltage of the detection signal is not influenced by the characteristic impedance of the vibrator. Thus, changes in the vibration of the vibrating gyroscope according to the rotation angular velocity can be accurately detected.
According to the present invention, the reference electrode is disposed on either one of the main surfaces of the vibrator in such a manner that the reference electrode is opposed to the drive e
LandOfFree
Vibrating gyroscope does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vibrating gyroscope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vibrating gyroscope will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2956254