Source: http://www.google.com/patents/US7437253?dq=7350717
Timestamp: 2014-07-29 11:49:09
Document Index: 103960447

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US7437253 - Parametrically disciplined operation of a vibratory gyroscope - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsParametrically disciplined operation of a symmetric nearly degenerate mode vibratory gyroscope is disclosed. A parametrically-disciplined inertial wave gyroscope having a natural oscillation frequency in the neighborhood of a sub-harmonic of an external stable clock reference is produced by driving an...http://www.google.com/patents/US7437253?utm_source=gb-gplus-sharePatent US7437253 - Parametrically disciplined operation of a vibratory gyroscopeAdvanced Patent SearchPublication numberUS7437253 B2Publication typeGrantApplication numberUS 11/192,759Publication dateOct 14, 2008Filing dateJul 29, 2005Priority dateJul 29, 2004Fee statusPaidAlso published asUS20060037417Publication number11192759, 192759, US 7437253 B2, US 7437253B2, US-B2-7437253, US7437253 B2, US7437253B2InventorsKirill V. Shcheglov, Ken J. Hayworth, A. Dorian Challoner, Chris S. PeayOriginal AssigneeThe Boeing Company, California Institute Of TechnologyExport CitationBiBTeX, EndNote, RefManPatent Citations (45), Non-Patent Citations (7), Referenced by (4), Classifications (6), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetParametrically disciplined operation of a vibratory gyroscopeUS 7437253 B2Abstract Parametrically disciplined operation of a symmetric nearly degenerate mode vibratory gyroscope is disclosed. A parametrically-disciplined inertial wave gyroscope having a natural oscillation frequency in the neighborhood of a sub-harmonic of an external stable clock reference is produced by driving an electrostatic bias electrode at approximately twice this sub-harmonic frequency to achieve disciplined frequency and phase operation of the resonator. A nearly symmetric parametrically-disciplined inertial wave gyroscope that can oscillate in any transverse direction and has more than one bias electrostatic electrode that can be independently driven at twice its oscillation frequency at an amplitude and phase that disciplines its damping to zero in any vibration direction. In addition, operation of a parametrically-disciplined inertial wave gyroscope is taught in which the precession rate of the driven vibration pattern is digitally disciplined to a prescribed non-zero reference value.
U.S. Provisional Patent Application No. 60/592,589, filed Jul. 29, 2004, and entitled �PARAMETRICALLY DISCIPLINED SYMMETRIC NEARLY DEGENERATE MODE VIBRATORY GYROSCOPE�, by Shcheglov et al.
U.S. patent application Ser. No. 10/639,134, by Shcheglov et al., filed Aug. 12, 2003, and entitled �ISOLATED PLANAR GYROSCOPE WITH INTERNAL RADIAL SENSING AND ACTUATION,� which claims priority to U.S. Provisional Patent Application No. 60/402,681, filed Aug. 12, 2002, and entitled �CYLINDER GYROSCOPE WITH INTEGRAL SENSING AND ACTUATION�, by Shcheglov et al. and U.S. Provisional Patent Application No. 60/428,451, filed Nov. 22, 2002, and entitled �DESIGN AND FABRICATION PROCESS FOR A NOVEL HIGH PERFORMANCE MESOGYRO�, by Shcheglov et al.
U.S. patent application Ser. No. 10/639,135, by Shcheglov et al., filed Aug. 12, 2003, and entitled �INTEGRAL RESONATOR GYROSCOPE� which claims priority to U.S. Provisional Patent Application No. 60/402,681, filed Aug. 12, 2002, and entitled �CYLINDER GYROSCOPE WITH INTEGRAL SENSING AND ACTUATION�, by Shcheglov et al. and U.S. Provisional Patent Application No. 60/428,451, filed Nov. 22, 2002, and entitled �DESIGN AND FABRICATION PROCESS FOR A NOVEL HIGH PERFORMANCE MESOGYRO�, by Shcheglov et al.; and
U.S. patent application Ser. No. 11/103,899, by Challoner et al., filed Apr. 12, 2005, and entitled �ISOLATED PLANAR MESOGYROSCOPE,� which claims priority to U.S. Provisional Patent Application No. 60/561,323, filed Apr. 12, 2004, by Challoner et al., entitled �MESOGYROSCOPE,�
U.S. Utility patent application Ser. No. 10/405,178, by Challoner, filed Apr. 2, 2003, entitled �ISOLATED RESONATOR GYROSCOPE,� which is a continuation of parent U.S. Pat. No. 6,629,460, issued Oct. 7, 2003, by Challoner, entitled �ISOLATED RESONATOR GYROSCOPE,�
U.S. Utility patent application Ser. No. 10/370,953, by Challoner et al., filed Feb. 20, 2003, entitled �ISOLATED RESONATOR GYROSCOPE WITH A DRIVE AND SENSE FRAME,�
U.S. Utility patent application Ser. No. 10/423,459, by Challoner et al., filed Apr. 25, 2003, entitled �ISOLATED RESONATOR GYROSCOPE WITH ISOLATION TRIMMING USING A SECONDARY ELEMENT,�; and
U.S. Utility patent application Ser. No. 10/410,744 by Challoner et al., filed Apr. 10, 2003, entitled �ISOLATED RESONATOR GYROSCOPE WITH COMPACT FLEXURES,�
U.S. Pat. No. 6,698,287, by Kubena et al., issued Mar. 2, 2004, entitled �MICROGYRO TUNING USING FOCUSED ION BEAMS�; and
U.S. Pat. No. 6,915,215, by M'Closkey et al., issued Jul. 5, 2005, entitled �INTEGRATED LOW POWER DIGITAL GYRO CONTROL ELECTRONICS�.
STATEMENT OF GOVERNMENT RIGHTS The invention described herein was made in the performance of work under NASA contract NAS 7-1402, and is subject to the provisions of Public Law 96-517 (35 U.S.C. 202) in which the Contractor has elected to retain title.
Conventionally-machined gyroscopes suitable for inertial wave operation such as the quartz hemispherical resonator gyroscope (HRG) have an ideal axisymmetric design, finite angular gain, k=0.3, with near-ideal mechanical fabrication precision and quality, but are not compact, low-cost and low-power. Furthermore, the HRG electronics operation limits performance. Several key parameters of the vibratory modal motion are not disciplined, e.g., resonator frequency and damping non-uniformity, leading to rate drift over temperature and are permitted to naturally vary with time or temperature or free-run. In some vibratory gyroscope designs the difference in the natural frequencies of the two resonator modes are controlled to zero or disciplined by driving output quadrature voltage to zero by modification of electrostatic biases to modify electrostatic stiffness, (quadrature nulling) or by feedback of the modal motion position states. Failure to discipline all parameters necessitates expensive calibration of the final rate output bias over temperature and case-orientation of the vibration pattern due to changes in the undisciplined parameters. Resonator state feedback is used to track the natural drive frequency and phase and control the amplitude using an automatic gain control (AGC) loop and sometimes the output axis in a force-to-rebalance loop. Sometimes drive frequency and phase is tracked with a phase-lock loop. Further, the output disturbance noise of the closed loop electronics of the HRG design is limiting noise and drift performance. A type of inertial wave operation (i.e., �whole-angle� or �rate-integrating�) has been used with the HRG, however the natural frequency and natural damping unbalance are still allowed to freely change with temperature and time. Case-fixed closed loop operation or free-precession operation of the HRG, at very low inertial rates, does not offer the opportunity to completely identify changes in the stiffness and damping parameters of motion in all directions.
SUMMARY OF THE INVENTION Embodiments of the present invention adapt the principle of parametric driving of oscillators to the operation of a microgyroscope to facilitate complete discipline of the parameters of motion, improve performance and other characteristics. Parametric driving, where the resonator spring constant is modulated at twice the resonant frequency, applied to embodiments of the present invention employs a substantially fixed external frequency reference to discipline the microgyro resonator. In addition, embodiments of the invention may uniformly null effective damping of motion at all case orientations through further parametrically disciplined operation of the microgyroscope.
a = F k 0 2 + k 1 2 4 + g 2 ⁢ ω 2 - 2 ⁢ k 0 ⁢ m ⁢ ⁢ ω 2 + m 2 ⁢ ω 4 + gk 1 ⁢ ωcos ⁢ ⁢ ( 2 ⁢ θ ) + k 1 ⁡ ( k 0 - m ⁢ ⁢ ω 2 ) ⁢ ⁢ sin ⁢ ⁢ ( 2 ⁢ θ ) ⁢ ⁢ and ( 2 ) tan ⁢ ⁢ θ = ( k 1 + 2 ⁢ g ⁢ ⁢ ω ) ⁢ ⁢ cos ⁢ ⁢ ϕ - 2 ⁢ ⁢ ( k 0 - m ⁢ ⁢ ω 2 ) ⁢ ⁢ sin ⁢ ⁢ ϕ - 2 ⁢ ⁢ ( k 0 - m ⁢ ⁢ ω 2 ) ⁢ ⁢ cos ⁢ ⁢ ϕ + ( k 1 - 2 ⁢ g ⁢ ⁢ ω ) ⁢ ⁢ sin ⁢ ⁢ ϕ . ( 3 ) It is apparent from Equation (2) that the damping term in denominator g2ω2 can be cancelled by the term,
k 1 2 4 + gk 1 ⁢ ωcos ⁢ ⁢ ( 2 ⁢ θ ) . This occurs when θ=90�, and k1=2 gω.
Increasing the parametric excitation amplitude causes the oscillator to have negative damping�the oscillation amplitude grows exponentially as shown in FIG. 3C where m=1, k0=1, g=0.01, k1=0.022, F=0, x(0)=1, x′(0)=0. FIG. 3D shows the dynamics of an oscillator with the same parameters as in FIG. 3B, except that the natural resonance frequency has been increased by 0.5% by increasing the stiffness of the spring from 1.00 to 1.01. For the oscillator of FIG. 3D, m=1, k0=1.01, g=0.01, k1=0.02, F=0, x(0)=1, x′(0)=0. It is apparent that the parametric pumping at the same amplitude no longer produces self-sustained oscillation. However, by increasing the parametric excitation amplitude (in this particular case from 0.02 to 0.0284), a self-sustaining oscillation condition can be recovered. FIG. 3E illustrates this case where m=1, k0=1.01, g=0.01, k1=0.0284, F=0, x(0)=1, x′(0)=0. It is important to note that the resonator now oscillates at half of the parametric pump frequency, and NOT at the natural frequency.
FIG. 4D illustrates and exemplary reference signal generator. The original clock signal fref is divided by N to yield a 2 f signal which is directly converted to analog to provide V2f and also divided by 2 (to yield f) and converted to analog to separately provide V�1f. V�2f and V�1f are applied to the controller 440 of FIG. 4B as indicated.
Mode 2 operates the gyroscope under force to rebalance as in Mode 1 but now with a disciplined resonator frequency. Opening switches #1 and #2 and applying V�2f reference level (+/−Vref) square wave from the reference generator shown in FIG. 4C to the AGC modulator input produces a scaled modulator output VB2f that transforms the original closed loop AGC drive into a self-disciplined open-loop drive. This drive, as shown in the analysis of a single harmonic oscillator, modulates the effective modal stiffness at 2 f and results in phase-lock of the resonator at the fundamental frequency, f, i.e., in phase with the V1f waveform. Demodulation of the S1 (quadrature sinsusoidal component, S1's) with V�1f will result in S1's=0 if the natural resonator frequency, fr is in the neighborhood of f and lock-in occurs. The maximum allowable value for |f−fr| for lock-in to occur can be determined from the above harmonic oscillator analysis with a model for the electrostatic stiffness (parameter k1) based on resonator voltages and capacitance gaps or it can be determined empirically by adjusting the reference frequency (N value) until S1's=0 and lockin occurs. Preferably |f−fr| should be less than �Q If fr begins to wander outside this range, then dc electrostatic bias parameters and resonator bias, kGB can be adjusted to shift fr back into the required neighborhood of f for lock in.
One benefit under Mode 3 operation is the ability to set Ωc p/(2 k)>Ω max so that F is always changing. This enables continual averaging of residual biases, sometimes referred to as �carouseling,� or continual identification and correction of residual damping along any case direction and hence the achievement of noise-limited drift.
FIG. 5A shows a finite element analysis model 500 of a disc resonator comprising 2440 nodes of internal rings with segments marked according to adjacent sense or control (drive) electrode names. The S1+ and D1+ electrodes are indicated by the �+� symbols within 45 degree arc segments (e.g., inner D1+ circumferential electrodes 502 and outer circumferential electrodes 504) centered on the first axis 506 and on opposing sides of the resonator. Similarly, the S1− and D1− electrodes are indicated by the �*� symbols within 45 degree arc segments (e.g., inner D1− circumferential electrodes 508 and outer circumferential electrodes 510) centered on another axis (not shown) orthogonal to the first axis 506 and on opposing sides of the resonator. The S2+, D2+, S2− and D2− electrodes are disposed in the same pattern about a second axis 512 shifted 45 degrees from the first axis 506. The outer S2+ electrodes 514 and inner D2+ electrodes 516 are shown (indicated by the �+� symbols) within 45 degree arc segments centered on the second axis 512 and the outer S2− electrodes 518 and inner D2− electrodes 520 (indicated by the �*� symbols) are disposed within 45 degree arc segments centered on another axis (not shown) orthogonal to the second axis 512 and on opposing sides.
FIG. 5B shows the finite element analysis model 500 with t-frame bias and trim adjacent electrostatic bias electrode locations and mechanical trim locations. The BT1 bias electrodes 522 (indicated by the �x� symbols) are disposed in 45 degree arc segments centered on and orthogonal to the second axis 512. Similarly, the BT2 bias electrodes 524 (indicated by the �x� symbols) are disposed in 45 degree arc segments centered on and orthogonal to the first axis 506. In addition, mechanical trim locations MT1 526 and MT2 528 are disposed on the outer periphery of the resonator centered on and orthogonal to the first and second axes 506, 512, respectively. The mechanical trim locations are for material removal by laser or FIB trim techniques.
FIG. 5C shows the finite element analysis model 500 with x-frame bias and trim adjacent electrostatic bias electrodes and mechanical trim locations. Here, the pattern is analogous to that of FIG. 5B, but shifted 45 degrees. Mechanical trim locations MX1 530 and MX2 532 are disposed on the outer periphery as shown. The BX1 electrodes 534 (indicated by the �x� symbols) are disposed in 45 degree arc segments centered on orthogonal axes through the MX1 530 mechanical trim locations. Similarly, the BX2 electrodes 536 (indicated by the �x� symbols) are disposed in 45 degree arc segments centered on orthogonal axes through the MX2 532 mechanical trim locations.
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KIRILL V.;HAYWORTH, MR. KEN J.;PEAY, MR. CHRIS S.;REEL/FRAME:016677/0074;SIGNING DATES FROM 20051014 TO 20051024Owner name: THE BOEING COMPANY, ILLINOISFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CHALLONER, MR. A. DORIAN;REEL/FRAME:016677/0053Effective date: 20051022RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google