Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2001-03-16
2002-12-24
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504140
Reexamination Certificate
active
06497147
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2000-077092 on Mar. 17, 2000 and to Japanese Application No. 2001-076275 filed on Mar. 16, 2001.
FIELD OF THE INVENTION
The present invention generally relates to an actuator for an oscillator. More particularly, the present invention pertains to an actuator for an oscillator for oscillating electrostatic driven type oscillators provided with angular rate sensors.
BACKGROUND OF THE INVENTION
A schematic illustration of related art actuators for an oscillator for oscillating electrostatic driven oscillators provided with an angular rate sensor is shown in FIG.
19
. As shown in
FIG. 19
, a signal for the displacement of the electrostatic driven oscillator caused by the oscillation in a driving direction is outputted from a driving direction displacement detecting electrode
81
to a displacement signal detecting portion
82
.
The displacement signal outputted to the displacement signal detecting portion
82
is synchronously detected at a timing synchronized to the displacement in a driving direction in a synchronous detection circuit
83
to be outputted to an amplitude adjuster
84
as oscillation amplitude data.
Simultaneously, the displacement signal outputted to the displacement signal detecting portion
82
is outputted to the amplitude adjuster
84
after being phase-shifted by approximately 90 degrees in a 90 degree phase shifter
85
. By means of the phase shift of the displacement signal by approximately 90 degrees via the 90 degree phase shifter
85
, an alternating voltage component of the drive signal having phase-contrast by approximately 90 degrees relative to the displacement signal is generated in the amplitude adjuster
84
to facilitate the oscillation of the electrostatic driven type oscillator.
The oscillation amplitude data outputted to the amplitude adjuster
84
is compared with a predetermined amplitude value in the amplitude adjuster
84
. When the oscillation amplitude data is smaller than the predetermined amplitude value, an alternating voltage component of the drive signal having increased amplitude is generated (incremental adjustment). On the other hand, when the oscillation amplitude data is larger than the predetermined amplitude value, the alternating voltage component of the drive signal having decreased amplitude is generated (decremental adjustment). The amplitude adjustment of the alternating voltage component of the drive signal in the foregoing manner is performed for controlling the amplitude driving force of the oscillator to have constant amplitude in the driving direction of the oscillator. The alternating voltage component of the drive signal in which the amplitude is adjusted in the foregoing manner is outputted to an adder
86
.
In the adder
86
, a drive signal is generated by incorporating the alternating voltage component of the drive signal in which the amplitude is adjusted and the direct-current voltage component of the drive signal having a predetermined value. The drive signal generated in this manner is supplied to a drive electrode
87
fixed on a substrate. When the voltage of the drive electrode of the oscillator side is grounded (GND), the oscillator is oscillated to have constant amplitude in the driving direction by the oscillation of the electrostatic attraction generated to be proportional to the second power of the drive signal between the oscillator and the drive electrode
87
.
Generally, electrostatic driven oscillators are oscillated by a drive signal consisting of the alternating voltage component and the direct-current voltage component supplied thereto. The electrostatic driven oscillators are oscillated by the oscillation of the electrostatic attraction generated proportional to the second power of the drive signal between the electrostatic driven oscillator and a drive electrode. The displacement of the electrostatic driven type oscillator according to the oscillation in a driving direction is detected as a displacement signal. The generation of the drive signal is controlled by an amplitude adjusting means to maintain the constancy of the oscillation amplitude of the electrostatic driven oscillator in a driving direction based on the detected displacement signal. By controlling the generation of the drive signal, the oscillation driving force of the electrostatic driven oscillator is controlled to maintain the constancy of the oscillation amplitude of the electrostatic driven oscillator in a driving direction.
The alternating voltage component of the drive signal is a cause of the noise of the displacement detecting signal because of the approximately same frequency with the displacement detecting signal. Thus, the alternating voltage component of the drive signal becomes a main cause of the detection error of the oscillation condition of the electrostatic driven oscillator. When an angular rate is detected during oscillation of the electrostatic driven oscillator applied to an angular rate sensor, the alternating voltage component causes a lag in the detected output.
When the amount of the noise derived from the alternating voltage component of the drive signal is stable, the detection error of the oscillation and the lag of the detected output of the angular rate maintain an approximately fixed level. When the detection error of the oscillation and the lag of the detected output of the angular rate maintain an approximately fixed level, they can be easily corrected. Therefore, when the amount of the noise derived from the alternating voltage component of the drive signal is stable, it is easy to correct the error. However, when the increase or decrease of the alternating voltage component of the drive signal is adjusted for maintaining the oscillation amplitude in a driving direction to be constant while the Q factor of the electrostatic driven oscillator in a driving direction fluctuates due to the change of the electrostatic driven oscillator due to the passage of time and the change in the environmental temperature, the amount of the noise mixed in the displacement detecting signal fluctuates. Thus, the detection error of the oscillation condition of the electrostatic driven type oscillator and the lag of the detected output of the angular rate are fluctuated by the increase or decrease of the alternating voltage component of the drive signal.
In order to minimize the fluctuation of the lag of the detecting output of the angular rate and the detection error of the oscillation condition of the electrostatic driven oscillator, it was proposed to control the oscillation drive force of the electrostatic driven oscillator to maintain the constancy of the oscillation amplitude of the electrostatic oscillator in a driving direction by increasing or decreasing only the direct-current voltage component while maintaining the constancy of the amplitude of the alternating voltage component of the drive signal.
Thus, as shown in a schematic illustration of
FIG. 20
, the displacement according to the oscillation of the electrostatic driven oscillator in a driven direction is outputted to a displacement signal detecting portion
92
from a driving direction displacement detecting electrode
91
as a displacement signal.
The displacement signal outputted to the displacement signal detecting portion
92
which is synchronously detected at a timing synchronized to the displacement in the driving direction in a synchronous detecting circuit
93
is outputted as the oscillation amplitude data to an oscillation adjuster
94
. The oscillation amplitude data outputted to the amplitude adjuster
94
is compared to a predetermined amplitude value in the amplitude adjuster
94
. When the oscillation amplitude data is smaller than the predetermined amplitude value, the direct-current voltage component of the drive signal is adjusted to be increased. On the other hand, when the oscillation amplitude data is larger than the predetermined amplitude value, the direct-current voltage component of the drive signal is
Kato Manabu
Kurachi Hideya
Aisin Seiki Kabushiki Kaisha
Kwok Helen
Sughrue & Mion, PLLC
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