DUAL-AXIS RESONATOR GYROSCOPE

• US 20090056443A1
• Filed: 03/13/2007
• Published: 03/05/2009
• Est. Priority Date: 03/13/2006
• Status: Active Grant

• Current Assignee: Y-Sensors, Ltd.
• Original Assignee: Yishay Sensors Ltd.
• Inventors: Netzer, Yishay
• Granted Patent: US 8,087,295 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

The present invention discloses an improved planar, dual-axis, resonator gyroscope with mechanical coupling of adjacent vibrating members. The primary-mode flexible hinges include a tangential torsion element that largely decouples the out-of-plane resonant frequency from the wafer thickness. The use of separate plates for the force-balance and for the electric spring enables decoupling of the two functions. The invention also provides resonant frequency servo-loop for locking of the sense-mode resonant frequency to the drive-mode frequency, an online self-test, a split force balance loop for self cancellation of the quadrature signal, decoupling of the force-balance and resonant frequency servo-loops and stabilization of the inertial rate-sensing sensitivity—when operated in an open loop mode, all without interfering with the normal operation of the gyroscope. An optional sensing of the Z-axis acceleration perpendicular to the sensor plane is also provided which can be used for compensating acceleration-induced errors.

Claims

1. A dual-axis resonator gyroscope comprising:

(a) a baseplate carrying a first set of electrodes; and

(b) a resonator layer deployed above said baseplate, said resonator layer including an anchored portion rigidly attached to said baseplate and four oscillators each linked to said anchored portion via an integral spring formation configured to allow in-plane angular deflection of the corresponding oscillator around an effective center of rotation, said resonator layer further including mechanical linking elements linking between adjacent of said oscillators such that, when one of said oscillators undergoes a first angular in-plane deflection, said mechanical linking elements induce an opposite angular in-plane deflection of adjacent ones of said oscillators,

wherein said linking elements are configured to include at least one portion extending substantially tangentially relative to said effective center of rotation, thereby reducing stresses in said oscillators caused by said mechanical linking elements during relative motion of said oscillators.

2. The resonator gyroscope of claim 1, wherein each of said linking elements is substantially U-shaped.

3. The resonator gyroscope of claim 1, wherein each of said oscillators is linked to said anchored portion via a pair of at least two beams.

4. The resonator gyroscope of claim 3, wherein said at least two beams diverge from said anchored portion towards said oscillator.

5. The resonator gyroscope of claim 1, wherein said integral spring formation for each of said oscillators includes a torsion beam deployed to reduce mechanical resistance to out-of-plane deflection of said oscillator.

6. The resonator gyroscope of claim 1, wherein each of said oscillators is substantially triangular.

7. The resonator gyroscope of claim 1, wherein a total area of said oscillators corresponds to at least 90 percent of an area of a square encompassing said oscillators.

8. The resonator gyroscope of claim 1, further comprising a coverplate attached to said resonator layer and carrying a second set of electrodes, said first and second sets of electrodes being substantially symmetrical under reflection in plane subdividing a thickness of said resonator layer.

9. The resonator gyroscope of claim 8, wherein said baseplate and said coverplate are formed from borosilicate glass and said resonator layer is formed from silicon.

10. The resonator gyroscope of claim 1, wherein said first set of electrodes includes at least two electrodes underlying each of said oscillators.

11. The resonator gyroscope of claim 1, wherein said anchored portion and said four oscillators have a single common electrical output connection.

12. A resonator gyroscope comprising:

(a) a baseplate carrying a first set of electrodes; and

(b) a resonator layer deployed above said baseplate, said resonator layer including an anchored portion rigidly attached to said baseplate and at least two oscillators each linked to said anchored portion via an integral spring formation configured to allow in-plane angular deflection of the corresponding oscillator,

wherein said integral spring formation for each of said oscillators includes a torsion beam deployed to reduce mechanical resistance to out-of-plane deflection of said oscillator.

13. A method for operating a resonator gyroscope, the method comprising:

(a) providing a resonator gyroscope having;

(i) at least one pair of oscillators configured to oscillate in a primary oscillatory direction with a first resonant frequency and in a secondary oscillatory direction perpendicular to said first oscillatory direction with a second resonant frequency, and

(ii) an electrically controllable resonance modifier deployed to vary at least one of said first and second resonant frequencies;

(b) exciting oscillatory motion of said oscillators in said primary oscillatory direction at said first resonant frequency and detecting a mechanical response of said oscillators in said second oscillatory direction at said first resonant frequency indicative of an inertial rotation rate; and

(c) while performing step (b);

(i) applying an oscillatory force to said oscillators in said second oscillatory direction at each of a pair of test frequencies spaced equally above and below said first resonant frequency,

(ii) measuring a resulting amplitude of vibration in said secondary oscillatory direction at each of said pair of test frequencies, and

(iii) adjusting said electrically controllable resonance modifier so as to equalize said resulting amplitudes for said pair of frequencies, thereby matching said first and second resonant frequencies.

14. The method of claim 13, wherein said electrically controllable resonance modifier includes an electrostatic spring.

15. The method of claim 14, wherein said detecting a mechanical response of said oscillators in said second oscillatory direction is performed by supplying a voltage to a first set of electrodes to achieve force balance to cancel deflection of said oscillators in said secondary oscillation direction at said first resonant frequency, and wherein said electrostatic spring employs a second set of electrodes distinct from said first set of electrodes.

16. The method of claim 15, wherein said electrostatic spring is actuated so as to substantially cancel out an affect of said force balance on said resonant frequency of said oscillators in said secondary oscillatory direction.

17. The method of claim 13, wherein said pair of test frequencies are referred to as said first pair of test frequencies, the method further comprising:

(a) applying an oscillatory force to said oscillators in said second oscillatory direction at each of a second pair of test frequencies spaced equally above and below said first resonant frequency by a spacing different from said first pair of test frequencies;

(b) measuring a resulting amplitude of vibration in said secondary oscillatory direction at each of said second pair of test frequencies, and

(c) deriving from measurements of the resulting amplitude of vibration at each of said first and second pairs of test frequencies an estimation of a gain factor of said oscillators at said first resonant frequency.

18. A resonator gyroscope comprising:

(a) at least one pair of oscillators configured to oscillate in a primary oscillatory direction with a first resonant frequency and in a secondary oscillatory direction perpendicular to said first oscillatory direction,

(b) a force balance arrangement deployed to supply a voltage to a first set of electrodes to achieve force balance to cancel deflection of said oscillators in said secondary oscillation direction at said first resonant frequency, and

(c) an electrostatic spring arrangement deployed to supply a voltage to a second set of electrodes so as to adjust a resonant frequency of oscillation of said oscillators in said second oscillatory direction to match said first resonant frequency,

wherein said second set of electrodes is non-contiguous with said first set of electrodes, and wherein said electrostatic spring arrangement is configured so as to apply a voltage to said second set of electrodes so as to substantially cancel out an affect of said force balance arrangement on said resonant frequency of said oscillators in said secondary oscillatory direction.

19. A method for simultaneously measuring common mode and differential mode deflections of a pair of oscillators each disposed between an upper and a lower electrode, the method comprising the steps of:

(a) applying a first oscillating electric signal having a first frequency significantly higher than a frequency of oscillator motion between said upper and lower electrodes such that said signal is applied in opposite polarity across the two oscillators;

(b) applying a second oscillating electric signal having a second frequency different from said first frequency and significantly higher than a frequency of oscillator motion between said upper and lower electrodes such that said signal is applied with the same polarity across the two oscillators;

(c) amplifying a signal derived from a common electrical contact to said pair of oscillators;

(d) obtaining from a component of said signal at said first frequency a differential mode deflection of said pair of oscillators; and

(e) obtaining from a component of said signal at said second frequency a common mode deflection of said pair of oscillators.

20. The method of claim 19, further comprising deriving from said common mode deflection an indication of linear acceleration.

21. The method of claim 19, further comprising applying to at least one of said upper and lower electrodes a voltage chosen to at least partially cancel said common mode deflection.

22. The method of claim 19, further comprising employing said common mode deflection as an input to a force balance arrangement for closed-loop cancellation of said common mode deflection.

23. The method of claim 19, further comprising measuring a differential mode deflection in a second pair of oscillators each disposed between an upper and a lower electrode, the second pair of oscillators being electrically connected to the first pair of oscillators, the method including applying a third oscillating signal having said first frequency between said upper and lower electrodes of said second pair of oscillators such that said signal is applied in opposite polarity across the two oscillators, said third signal being at a predefined phase difference to said first signal.