Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2001-03-16
2002-12-10
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504140
Reexamination Certificate
active
06490924
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2000-077091 filed on Mar. 17, 2000, the entire content of which is incorporated herein by reference.
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 an electrostatic driven type oscillator provided with an angular rate sensor.
BACKGROUND OF THE INVENTION
A block diagram of a known actuator for an oscillator for oscillating electrostatic driven type oscillators provided with angular rate sensors is shown in FIG.
14
. As shown in
FIG. 14
, a signals for the displacement of the electrostatic driven type 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, the 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 of 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 of which the amplitude is adjusted and the direct-current voltage component (bias voltage) 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 (oscillation driving force) generated to be proportional to the second power of the drive signal (driving voltage) between the oscillator and the drive electrode
87
.
Generally, electrostatic driven type 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 (oscillation driving force) generated proportional to the second power of the drive signal between the electrostatic driven type oscillator and a drive electrode. The displacement (oscillation amplitude) of the electrostatic driven type oscillator according to the oscillation in the driving direction is detected as the 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 type oscillator in the driving direction based on the detected displacement signal. By controlling the generation of the drive signal, the oscillation driving force (electrostatic attraction) of the electrostatic driven type oscillator is controlled to maintain the constancy of the oscillation amplitude of the electrostatic driven type oscillator in the 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 type oscillator. When the angular rate is detected while the electrostatic driven type oscillator is oscillated, the alternating voltage component causes a lag of the detected output.
When the amount of the noise deriving from the alternating 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 deriving 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 the driving direction to be constant while the Q factor of the electrostatic driven type oscillator in the driving direction is fluctuated by the change of the electrostatic driven type oscillator due to the passage of time and the change of the environmental temperature, the amount of the noise mixed in the displacement detecting signal is fluctuated. Thus, the detecting 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.
SUMMARY OF THE INVENTION
In light of the foregoing, it is an object of the present invention to provide an actuator for an oscillator preventing unfavorable conditions such as the change of the detection error and the fluctuation of the lag of the detecting output of the angular rate of the oscillation of the electrostatic driven type oscillator by controlling the fluctuation of the amount of the noise mixed in the displacement signal.
It is a further object of the present invention to provide an actuator for oscillators minimizing the fluctuation of the alternating voltage component of the drive signal.
To attain the above objects, the following technical means are provided with the actuator for the oscillator of the present invention which includes an electrostatic driven type oscillator, an oscillator driving means for oscillating the electrostatic driven type oscillator by outputting a drive signal thereto, a displacement detecting means for detecting the displacement based on the oscillation of the electrostatic driven type oscillator as a displacement signal, and an amplitude adjusting means for controlling the generation of the drive signal outputted from the oscillator driving means to maintain the constancy of the oscillation amplitude of the electrostatic driven type oscillator based on the detected displacement signal. The amplitude adjusting means includes an alternating voltage component generating means for generating an alternating voltage component of the drive signal havi
Kato Manabu
Kurachi Hideya
Aisin Seiki Kabushiki Kaisha
Kwok Helen
Sughrue & Mion, PLLC
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