Generation of mechanical oscillation applicable to vibratory rate gyroscopes
First Claim
1. An oscillation-sustaining system for a vibrating microstructure comprising:
- a microstructure having a resonant frequency anchored to a substrate by a suspension having compliance along a dither axis;
a sensor for measuring displacement of the microstructure along the dither axis;
sensing circuitry to infer positioning of the microstructure based upon an output of the sensor;
an amplitude detection circuit having an output;
a filter circuit for filtering the output of the amplitude-detection circuit;
a filter having a phase shift about the resonant frequency, the phase shift having a magnitude and a sign which are adjustable by the filtered representation of the amplitude-detection circuit output; and
a force transducer for applying an oscillation-sustaining force along the dither axis based upon a phase-shifted representation of the microstructure position.
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Accused Products
Abstract
To achieve a drive-axis oscillation with improved frequency and amplitude stability, additional feedback loops are used to adjust force-feedback loop parameters.
An amplitude-control loop measures oscillation amplitude, compares this value to the desired level, and adjusts damping of the mechanical sense-element to grow or shrink oscillation amplitude as appropriate. A frequency-tuning loop measures the oscillation frequency, compares this value with a highly stable reference, and adjusts the gain in the force-feedback loop to keep the drive-axis oscillation frequency at the reference value. The combined topology simultaneously controls both amplitude and frequency. Advantages of the combined topology include improved stability, fast oscillation start-up, low power consumption, and excellent shock rejection.
71 Citations
24 Claims
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1. An oscillation-sustaining system for a vibrating microstructure comprising:
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a microstructure having a resonant frequency anchored to a substrate by a suspension having compliance along a dither axis;
a sensor for measuring displacement of the microstructure along the dither axis;
sensing circuitry to infer positioning of the microstructure based upon an output of the sensor;
an amplitude detection circuit having an output;
a filter circuit for filtering the output of the amplitude-detection circuit;
a filter having a phase shift about the resonant frequency, the phase shift having a magnitude and a sign which are adjustable by the filtered representation of the amplitude-detection circuit output; and
a force transducer for applying an oscillation-sustaining force along the dither axis based upon a phase-shifted representation of the microstructure position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
a first substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a second conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the first comb, the first and second combs forming electrodes of a first capacitor with capacitance changing for displacements along the dither axis.
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3. The system of claim 1 wherein the force transducer includes:
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a third substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a fourth conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the third comb, the third and fourth combs forming electrodes of a second capacitor with capacitance changing for displacements along the dither axis.
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4. The system of claim 2 wherein said first capacitor is additionally used as a force transducer by time multiplexing connectivity of said first capacitor between a position-sense interface and a pair of terminals having a voltage across the pair.
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5. The system of claim 2 wherein said first capacitor is additionally used as a force transducer using frequency multiplexing of voltages applied to said first capacitor.
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6. The system of claim 1 wherein said sensing circuitry, said amplitude detection circuit, and said filter having a phase shift about the resonant frequency operate at discrete time periods.
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7. The system of claim 1 wherein said sensing circuitry, said amplitude detection circuit, and said filter having a phase shift about the resonant frequency, operate continuously.
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8. The system of claim 1 additionally including a phase-locked loop for synchronization of a clock circuit to the position of the microstructure during oscillation.
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9. An oscillation-sustaining system for a vibrating microstructure comprising:
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a microstructure having a resonant frequency anchored to a substrate by a suspension having compliance along a dither axis;
a sensor for measuring displacement of the microstructure along the dither axis;
sensing circuitry to determine the position of the microstructure based upon an output of the sensor;
a reference frequency;
a phase detection circuit having an output;
a filter circuit for filtering the output of the phase detection circuit;
a filter having a substantially constant phase shift about the resonant frequency;
a circuit producing a gain having a magnitude which is adjustable by the filtered representation of the output of the phase-detection circuit; and
a force transducer for applying an oscillation-sustaining force along the dither axis based upon a phase-shifted representation of the microstructure position. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
a first substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a second conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the first comb, the first and second combs forming electrodes of a first capacitor with capacitance changing for displacements along the dither axis.
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11. The system of claim 9 wherein the force transducer includes:
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a third substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a fourth conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the third comb, the third and fourth combs forming electrodes of a second capacitor with capacitance changing for displacements along the dither axis.
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12. The system of claim 10 wherein said first capacitor is additionally used as a force transducer by time multiplexing connectivity of said first capacitor between a position-sense interface and a pair of terminals having a voltage across the pair.
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13. The system of claim 10 wherein said first capacitor is additionally used as a force transducer using frequency multiplexing of voltages applied to said first capacitor.
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14. The system of claim 9 wherein said sensing circuitry, said phase detection circuit, and said filter having a substantially constant phase shift about the resonant frequency operate at discrete time periods.
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15. The system of claim 9 wherein said sensing circuitry, said phase detection circuit, and said filter having a substantially constant phase shift about the resonant frequency operate.
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16. The system of claim 9 additionally including a phase-locked loop for synchronization of a clock circuit to the position of the microstructure during oscillation.
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17. An oscillation-sustaining system for a vibrating microstructure comprising:
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a microstructure having a resonant frequency anchored to a substrate by a suspension having compliance along a dither axis;
a sensor for measuring displacement of the microstructure along the dither axis;
sensing circuitry to determine the position of the microstructure based upon an output of the sensor;
an amplitude detection circuit having an output;
a filter circuit for filtering the output of the amplitude-detection circuit;
a filter having a phase shift about the resonant frequency, the phase shift having a magnitude and a sign which are adjustable by the filtered representation of the amplitude-detection circuit output;
a reference frequency;
a phase-detection circuit having an output;
a filter circuit for filtering the output of the phase-detection circuit;
a circuit outputting a gain having a magnitude adjustable by the filtered representation of the phase-detection circuit output; and
a force transducer for applying an oscillation-sustaining force along the dither axis, where the input to the transducer is a phase-shifted representation of the microstructure position. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
a first substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a second conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the first comb, the first and second combs forming electrodes of a first capacitor with capacitance changing for displacements along the dither axis.
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19. The system of claim 17 wherein the force transducer includes:
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a third substantially stationary conductive comb anchored to said substrate having a plurality of fingers extending towards the microstructure; and
a fourth conductive comb connected to the microstructure having a plurality of fingers that interdigitate with the fingers of the third comb, the third and fourth combs forming electrodes of a second capacitor with capacitance changing for displacements along the dither axis.
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20. The system of claim 18 wherein said first capacitor is additionally used as a force transducer by time multiplexing connectivity of said first capacitor between a position-sense interface and a pair of terminals having a voltage across the pair.
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21. The system of claim 18 wherein said first capacitor is additionally used as a force transducer using frequency multiplexing of voltages applied to said first capacitor.
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22. The system of claim 17 wherein said sensing circuitry, said amplitude detection circuit, said phase detection circuit, and said filter having a phase shift about the resonant frequency, operate at discrete time periods.
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23. The system of claim 17 wherein said sensing circuitry, said amplitude detection circuit, said phase detection circuit, and said filter having a phase shift about the resonant frequency, operate continuously.
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24. The system of claim 17 additionally including a phase-locked loop for synchronization of a clock circuit to the position of the microstructure during oscillation.
Specification