Method of simultaneously and directly generating an angular position and angular velocity measurement in a micromachined gyroscope

US 20050150296A1
Filed: 11/23/2004
Published: 07/14/2005
Est. Priority Date: 12/04/2003
Status: Active Grant

First Claim

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1. An improvement in a method for controlling a micromachined gyroscope comprising a substrate, a proof mass coupled to the substrate by an isotropic suspension such that the proof mass can move in any direction in a working plane, one or more drive electrodes configured to cause the proof mass to oscillate in the working plane in a precessing elliptical path, and one or more sense electrodes configured to sense the motion of the proof mass in the working plane, the improvement comprising:

measuring the angle of precession of the elliptical path in the working plane from which an angle of rotation of the gyroscope is determined; and

simultaneously measuring the angular rate of rotation of the gyroscope.

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Abstract

A sensor is fabricated with micron feature sizes capable of simultaneously measuring absolute angles of rotation and angular rotational rates. The measurements are made directly from the position and velocity of the device without the need for electronic integration or differentiation. The device measures angle directly, avoiding the integration of electronic errors and allowing for higher performance in attitude measurement. These performance improvements and flexibility in usage allow for long term attitude sensing applications such as implantable prosthetics, micro-vehicle navigation, structural health monitoring, and long range smart munitions. Through the fabrication of the device using lithographic methods, the device can be made small and in large qualities, resulting in low costs and low power consumption.

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26 Claims

1. An improvement in a method for controlling a micromachined gyroscope comprising a substrate, a proof mass coupled to the substrate by an isotropic suspension such that the proof mass can move in any direction in a working plane, one or more drive electrodes configured to cause the proof mass to oscillate in the working plane in a precessing elliptical path, and one or more sense electrodes configured to sense the motion of the proof mass in the working plane, the improvement comprising:
- measuring the angle of precession of the elliptical path in the working plane from which an angle of rotation of the gyroscope is determined; and
  
  simultaneously measuring the angular rate of rotation of the gyroscope.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- - 2. The improvement of claim 1 where measuring the angle of precession or angle of rotation of the gyroscope and simultaneously measuring the angular rate of rotation of the gyroscope comprises measuring the position and the velocity of the proof mass in the working plane and generating the angle of precession and the angular rate of rotation of the gyroscope therefrom.
  - 3. The improvement of claim 2 where generating the angle of precession or angle of rotation of the gyroscope comprises generating an angle of precession signal according to:
    - $ϕ = \frac{1}{2} \tan^{- 1} [\frac{2 (ω_{n}^{2} x y + \dot{x} \dot{y})}{ω_{n}^{2} (x^{2} - y^{2}) + ({\dot{x}}^{2} - {\dot{y}}^{2})}] = - Ω$ where x and y are the position of the proof mass in the working plane, {dot over (x)} and {dot over (y)} are the velocity of the proof mass in the working plane, ω
      
      _nis the natural frequency of the gyroscope, where φ
      
      is the angle of precession and where Ω
      
      is the angle of rotation of the gyroscope.
  - 4. The improvement of claim 2 where measuring the angular rate of rotation of the gyroscope comprises generating an angular momentum signal of the proof mass from the position and velocity of the proof mass in the working plane, synchronously demodulating the angular momentum signal, filtering the demodulated angular momentum signal to remove all frequencies higher than the fundamental frequency of the gyroscope, and generating a signal corresponding to the angular rate of rotation of the gyroscope according to $- 2$
    - ⁢
      
      H * ⁢
      
      ω
      
      n 2 E = 
      
      Ω
      
      
      
      ⁢
      
      ⁢
      
      cos ⁢
      
      ⁢
      
      ω
      
      q where H* is the demodulated angular momentum signal, ω
      
      _nis the natural frequency of the gyroscope, E is the mass normalized energy of the gyroscope as a function of the position and velocity of the proof mass and ω
      
      _nthe natural frequency, and ω
      
      _qis the frequency of sensed rotation and where ω
      
      _q<
      
      <
      
      ω
      
      _nand where H*<
      
      <
      
      E.
  - 5. The improvement of claim 3 where measuring the angle of rotation of the gyroscope comprises generating the generating an angle of precession signal in hardware.
  - 6. The improvement of claim 4 where generating an angular momentum signal of the proof mass from the position and velocity of the proof mass in the working plane, synchronously demodulating the angular momentum signal, filtering the demodulated angular momentum signal to remove all frequencies higher than the fundamental frequency of the gyroscope, and generating a signal corresponding to the angular rate of rotation of the gyroscope comprises generating an angular momentum signal in hardware, synchronously demodulating the angular momentum signal in hardware, filtering the demodulated angular momentum signal in hardware, and generating a signal corresponding to the angular rate of rotation of the gyroscope in hardware.
  - 7. The improvement of claim 1 where measuring the angle of precession and simultaneously measuring the angular rate of rotation of the gyroscope comprises sensing the position and velocity of the proof mass, generating signals corresponding to the position and velocity of the proof mass and simultaneously generating the angle of rotation of the gyroscope and the rate of the angle of rotation of the gyroscope therefrom.
  - 8. The improvement of claim 7 where sensing the position and velocity of the proof mass comprises capacitively sensing the position and velocity of the proof mass.

9. An improvement in a method for controlling a MEMS gyroscope comprised of vibrational lumped mass system rigidly attached to a substrate via suspension members which are attached to a proof mass on one end and anchored to the substrate through the anchors, the suspension members allowing isotropic compliance of movement of the proof mass within a working plane while restricting motion along an axis of rotation, electrostatic forces being used for the vibrational actuation of the gyroscope by means of fixed electrodes wherein position and velocity of the proof mass are detected by an output current induced by the motion of the gyroscope, the improvement comprising:
- driving the gyroscope in a mode where the equations of state for detected positions of the proof mass as a function of time form an elliptical orbit which is characterized after time averaging by orbital parameters including an inclination φ
  
  of the elliptical path from a fixed inertial reference frame wherein the rate change of the inclination φ
  
  is physically equal and opposite to the input rotation Ω
  
  of the gyroscope
  {dot over (φ
  
  )}=−
  
  Ω
  
  and where the magnitude of the inclination φ
  
  is physically equal to the negative angle of rotation of the gyroscope $ϕ = - \int_{0}^{t} Ω ⅆ t$
- View Dependent Claims (10, 11, 12, 13)
- - 10. The improvement of claim 9 further comprising measuring the angle of rotation of the gyroscope or angular inclination φ
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating φ
      
      according to;
      
      $\tan 2 ϕ = \frac{2 (ω_{n}^{2} x y + \dot{x} \dot{y})}{ω_{n}^{2} (x^{2} - y^{2}) + ({\dot{x}}^{2} - {\dot{y}}^{2})}$
  - 11. The improvement of claim 9 further comprising measuring the angular velocity Ω
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating Ω
      
      according to $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q}$ where ω
      
      _nis the natural frequency of the proof mass, ω
      
      _qis the input frequency applied to the gyroscope, where H* is the mass normalized angular momentum which as been demodulated at by multiplying by cos 2ω
      
      _nt and removing all high frequency components above a predetermined cutoff frequency, so that $H^{*} = - \frac{(a^{2} - b^{2}) \langle Ω \rangle}{4} \cos ω_{q}$ $where  (a^{2} - b^{2}) = \frac{2}{ω_{n}^{2}} E$ $E = \frac{ω_{n}^{2} (x^{2} + y^{2}) + ({\dot{x}}^{2} + {\dot{y}}^{2})}{2}$ where E is the normalized system conserved energy, thus resulting in an angular rate Ω
      
      given by $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q} .$
  - 12. The improvement of claim 10 further comprising measuring the angular velocity Ω
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating Ω
      
      according to $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q}$ where ω
      
      _nis the natural frequency of the proof mass, ω
      
      _qis the input frequency applied to the gyroscope, where H* is the mass normalized angular momentum which as been demodulated at by multiplying by cos 2ω
      
      _nt and removing all high frequency components above a predetermined cutoff frequency, so that $H^{*} = - \frac{(a^{2} - b^{2}) \langle Ω \rangle}{4} \cos ω_{q}$ $where  (a^{2} - b^{2}) = \frac{2}{ω_{n}^{2}} E$ $E = \frac{ω_{n}^{2} (x^{2} + y^{2}) + ({\dot{x}}^{2} + {\dot{y}}^{2})}{2}$ where E is the normalized system conserved energy, thus resulting in an angular rate Ω
      
      given by $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q} .$
  - 13. The improvement of claim 12 where measuring the angular velocity Ω
    - of the gyroscope is performed simultaneously with measuring the angle of rotation of the gyroscope or angular inclination φ
      
      of the gyroscope.

14. An improvement in a micromachined gyroscope comprising a substrate, a proof mass coupled to the substrate by an isotropic suspension such that the proof mass can move in any direction in a working plane, one or more drive electrodes configured to cause the proof mass to oscillate in the working plane in a precessing elliptical path, and one or more sense electrodes configured to sense the motion of the proof mass in the working plane, the improvement comprising:
- means for measuring the angle of precession of the elliptical path in the working plane or an angle of rotation of the gyroscope; and
  
  means for simultaneously measuring the angular rate of rotation of the gyroscope.
- View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
- - 15. The improvement of claim 14 where the means for measuring the angle of precession or angle of rotation of the gyroscope and the means for simultaneously measuring the angular rate of rotation of the gyroscope comprises means for measuring the position and the velocity of the proof mass in the working plane and generating the angle of precession and the angular rate of rotation of the gyroscope therefrom.
  - 16. The improvement of claim 15 where the means for generating the angle of precession or angle of rotation of the gyroscope comprises means for generating an angle of precession signal according to:
    - $ϕ = \frac{1}{2} \tan^{- 1} [\frac{2 (ω_{n}^{2} xy + \dot{x} \dot{y})}{ω_{n}^{2} (x^{2} - y^{2}) + ({\dot{x}}^{2} - {\dot{y}}^{2})}] = - Ω$ where x and y are the position of the proof mass in the working plane, {dot over (x)} and {dot over (y)} are the velocity of the proof mass in the working plane, ω
      
      _nis the natural frequency of the gyroscope, where φ
      
      is the angle of precession and where Ω
      
      is the angle of rotation of the gyroscope.
  - 17. The improvement of claim 15 where the means for measuring the angular rate of rotation of the gyroscope comprises means for generating an angular momentum signal of the proof mass from the position and velocity of the proof mass in the working plane, means for synchronously demodulating the angular momentum signal, means for filtering the demodulated angular momentum signal to remove all frequencies higher than the fundamental frequency of the gyroscope, and means for generating a signal corresponding to the angular rate of rotation of the gyroscope according to $- 2$
    - H * ⁢
      
      ω
      
      n 2 E = 
      
      Ω
      
      
      
      ⁢
      
      cos ⁢
      
      ⁢
      
      ω
      
      q where H* is the demodulated angular momentum signal, ω
      
      _nis the natural frequency of the gyroscope, E is the mass normalized energy of the gyroscope as a function of the position and velocity of the proof mass and ω
      
      _nthe natural frequency, and ω
      
      _qis the frequency of sensed rotation and where ω
      
      _q<
      
      <
      
      ω
      
      _nand where H*<
      
      <
      
      E.
  - 18. The improvement of claim 16 where the means for measuring the angle of rotation of the gyroscope comprises means for generating the generating an angle of precession signal in hardware.
  - 19. The improvement of claim 17 where the means for generating an angular momentum signal of the proof mass from the position and velocity of the proof mass in the working plane, the means for synchronously demodulating the angular momentum signal, the means for filtering the demodulated angular momentum signal to remove all frequencies higher than the fundamental frequency of the gyroscope, and the means for generating a signal corresponding to the angular rate of rotation of the gyroscope comprises means for generating an angular momentum signal in hardware, means for synchronously demodulating the angular momentum signal in hardware, means for filtering the demodulated angular momentum signal in hardware, and means for generating a signal corresponding to the angular rate of rotation of the gyroscope in hardware.
  - 20. The improvement of claim 14 where the means for measuring the angle of precession and the means for simultaneously measuring the angular rate of rotation of the gyroscope comprises means for sensing the position and velocity of the proof mass, means for generating signals corresponding to the position and velocity of the proof mass and means for simultaneously generating the angle of rotation of the gyroscope and the rate of the angle of rotation of the gyroscope therefrom.
  - 21. The improvement of claim 20 where the means for sensing the position and velocity of the proof mass comprises means for capacitively sensing the position and velocity of the proof mass.

22. An improvement in a MEMS gyroscope comprised of vibrational lumped mass system rigidly attached to a substrate via suspension members which are attached to a proof mass on one end and anchored to the substrate through the anchors, the suspension members allowing isotropic compliance of movement of the proof mass within a working plane while restricting motion along an axis of rotation, electrostatic forces being used for the vibrational actuation of the gyroscope by means of fixed electrodes wherein position and velocity of the proof mass are detected by an output current induced by the motion of the gyroscope, the improvement comprising:
- means for driving the gyroscope in a mode where the equations of state for detected positions of the proof mass as a function of time form an elliptical orbit which is characterized after time averaging by orbital parameters including an inclination φ
  
  of the elliptical path from a fixed inertial reference frame wherein the rate change of the inclination φ
  
  is physically equal and opposite to the input rotation Ω
  
  of the gyroscope
  {dot over (φ
  
  )}=−
  
  Ω
  
  and where the magnitude of the inclination φ
  
  is physically equal to the negative angle of rotation of the gyroscope $ϕ = - \int_{0}^{t} Ω ⅆ t .$
- View Dependent Claims (23, 24, 25, 26)
- - 23. The improvement of claim 22 further comprising means for measuring the angle of rotation of the gyroscope or angular inclination φ
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating φ
      
      according to;
      
      $\tan 2 ϕ = \frac{2 (ω_{n}^{2} xy + \dot{x} \dot{y})}{ω_{n}^{2} (x^{2} - y^{2}) + ({\dot{x}}^{2} - {\dot{y}}^{2})}$
  - 24. The improvement of claim 22 further comprising means for measuring the angular velocity Ω
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating Ω
      
      according to $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q}$ where ω
      
      _nis the natural frequency of the proof mass, ω
      
      _qis the input frequency applied to the gyroscope, where H* is the mass normalized angular momentum which as been demodulated at by multiplying by cos 2ω
      
      _nt and removing all high frequency components above a predetermined cutoff frequency, so that $H^{*} = - \frac{(a^{2} - b^{2}) \langle Ω \rangle}{4} \cos ω_{q} where$ $\begin{matrix} (a^{2} - b^{2}) = \frac{2}{ω_{n}^{2}} E \\ E = \frac{ω_{n}^{2} (x^{2} + y^{2}) + ({\dot{x}}^{2} + {\dot{y}}^{2})}{2} \end{matrix}$ where E is the normalized system conserved energy, thus resulting in an angular rate Ω
      
      given by $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q} .$
  - 25. The improvement of claim 23 further means for comprising measuring the angular velocity Ω
    - of the gyroscope by measuring the detected position and velocity of the proof mass and generating Ω
      
      according to $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q}$ where ω
      
      _nis the natural frequency of the proof mass, ω
      
      _qis the input frequency applied to the gyroscope, where H* is the mass normalized angular momentum which as been demodulated at by multiplying by cos 2ω
      
      _nt and removing all high frequency components above a predetermined cutoff frequency, so that where $H^{*} = - \frac{(a^{2} - b^{2}) \langle Ω \rangle}{4} \cos ω_{q} where$ $\begin{matrix} (a^{2} - b^{2}) = \frac{2}{ω_{n}^{2}} E \\ E = \frac{ω_{n}^{2} (x^{2} + y^{2}) + ({\dot{x}}^{2} + {\dot{y}}^{2})}{2} \end{matrix}$ where E is the normalized system conserved energy, thus resulting in an angular rate Ω
      
      given by $\frac{- 2 H^{*} ω_{n}^{2}}{E} = \langle Ω \rangle \cos ω_{q} .$
  - 26. The improvement of claim 25 where the means for measuring the angular velocity Ω
    - of the gyroscope operates simultaneously with the means for measuring the angle of rotation of the gyroscope or angular inclination φ
      
      of the gyroscope.

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Current Assignee
Andrei M. Shkel, Chris Painter
Original Assignee
Andrei M. Shkel, Chris Painter
Inventors
Shkel, Andrei M., Painter, Chris

Granted Patent

US 7,040,164 B2
Time in Patent Office

Days
Field of Search
US Class Current

73/504.120
CPC Class Codes

G01C 19/5719 using planar vibrating mass...

Method of simultaneously and directly generating an angular position and angular velocity measurement in a micromachined gyroscope

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Method of simultaneously and directly generating an angular position and angular velocity measurement in a micromachined gyroscope

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