System and method for measuring rotational movement about an axis

• US 7,669,475 B2
• Filed: 06/18/2007
• Issued: 03/02/2010
• Est. Priority Date: 09/28/2006
• Status: Active Grant

• Current Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rosemount Aerospace, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Goldenberg, Felix, Nielsen, Ryan
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/764,558
• Publication Number:
  US 20080121054A1
• Time in Patent Office: 988 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.3, 735/041.4, 735/041.5
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/08 electrically driven G01C19/14 takes precedence
• CPC Class Codes: Y10T 74/1282 with rotor drive

Abstract

In one embodiment, a micro-gyro device for measuring rotational movement about an input axis includes a driving element generating a driving signal. A MEMS gyro includes a motor rotor and a motor assembly. The motor rotor receives the driving signal and oscillates about a motor axis at a frequency determined as a function of the driving signal. The motor assembly oscillates around a rate axis, which is orthogonal to the motor axis, as a function of the frequency of the motor rotor oscillation. A capacitance of the motor assembly changes as a function of the oscillation of the motor assembly. Driving element feedback circuitry, including a first band-pass filter, is between the motor rotor and the driving element. The driving element feedback circuitry causes the driving element to generate the driving signal as a function of an amplitude of the motor rotor oscillation for maintaining the amplitude of the motor rotor oscillation within a predetermined range. Output circuitry, including a second band-pass filter, produces an output signal as a function of the changing capacitance of the motor assembly. The first and second band-pass filters have central frequency phase characteristics not exceeding about 0.1°/Hz.

Claims

1. A micro-gyro device for measuring rotational movement about an input axis, comprising:

a driving element generating a driving signal;

a MEMS gyro including a motor rotor and a motor assembly, the motor rotor receiving the driving signal and oscillating about a motor axis at a frequency determined as a function of the driving signal, the motor assembly oscillating around a rate axis, which is orthogonal to the motor axis, as a function of the frequency of the motor rotor oscillation, a capacitance of the motor assembly changing as a function of the oscillation of the motor assembly;

driving element feedback circuitry, including a first band-pass filter, between the motor rotor and the driving element, the driving element feedback circuitry causing the driving element to generate the driving signal as a function of an amplitude of the motor rotor oscillation for maintaining the amplitude of the motor rotor oscillation within a predetermined range; and

output circuitry, including a second band-pass filter, producing an output signal as a function of the changing capacitance of the motor assembly, the first and second band-pass filters having central frequency phase characteristics not exceeding about 0.1°

/Hz.

2. The micro-gyro device as set forth in claim 1, wherein a Coriolis force, created by oscillation of the motor rotor, causes the motor assembly to oscillate.

3. The micro-gyro device as set forth in claim 1, further including:

a third band-pass filter electrically connected in series with the first band-pass filter; and

a fourth band-pass filter electrically connected in series with the second band-pass filter, the third and fourth band-pass filters having central frequency phase characteristics not exceeding about 0.1°

/Hz.

4. The micro-gyro device as set forth in claim 1, wherein:

the phase shift between both of the first and second band-pass filters at a central frequency is about zero.

5. The micro-gyro device as set forth in claim 4, wherein the central frequency is about 6.0 kHz.

6. The micro-gyro device as set forth in claim 1, wherein the first and second band-pass filters have a Q of at least about 10 and a bandwidth of at least about 250 Hz at a central frequency of about 6.0 kHz.

7. The micro-gyro device as set forth in claim 1, further including:

a plurality of first additional band-pass filters electrically multi-cascaded with the first band-pass filter; and

a plurality of second additional band-pass filters electrically multi-cascaded with the second band-pass filter, the plurality of first and second additional band-pass filters having central frequency phase characteristics not exceeding about 0.1°

/Hz.

8. The micro-gyro device as set forth in claim 7, wherein:

a bandwidth of the first band-pass filter and the first additional band-pass filters is about 250 Hz at a central frequency of about 6.0 kHz; and

a bandwidth of the second band-pass filter and the second additional band-pass filters is about 250 Hz at a central frequency of about 6.0 kHz.

9. The micro-gyro device as set forth in claim 8, wherein:

the first band-pass filter and the first additional band-pass filters have respective predetermined and respective incrementally spaced resonance frequencies; and

the second band-pass filter and the second additional band-pass filters have the respective predetermined and the respective incrementally spaced resonance frequencies.

10. A micro-gyro device for measuring rotational movement about an input axis, comprising:

a driving element generating a driving signal;

a MEMS gyro including a motor rotor and a motor assembly, the motor rotor receiving the driving signal and oscillating about a motor axis at a frequency determined as a function of the driving signal, the motor assembly oscillating around a rate axis, which is orthogonal to the motor axis, as a function of the frequency of the motor rotor oscillation, a capacitance of the motor assembly changing as a function of the oscillation of the motor assembly;

driving element feedback circuitry, including a first plurality of cascaded band-pass filters, between the motor rotor and the driving element, the driving element feedback circuitry causing the driving element to generate the driving signal as a function of an amplitude of the motor rotor oscillation for maintaining the amplitude of the motor rotor oscillation within a predetermined range; and

output circuitry, including a second plurality of cascaded band-pass filters, producing an output signal as a function of the changing capacitance of the motor assembly, the first and second plurality of band-pass filters having matching phase characteristics.

11. The micro-gyro device as set forth in claim 10, wherein:

the first plurality of band-pass filters have respective predetermined and respective incrementally spaced resonance frequencies; and

the second plurality of band-pass filters have respective predetermined and respective incrementally spaced resonance frequencies.

12. The micro-gyro device as set forth in claim 11, wherein:

a bandwidth of the first plurality of band-pass filters is about 250 Hz at a central frequency of about 6.0 kHz; and

a bandwidth of the second plurality of band-pass filters is about 250 Hz at a central frequency of about 6.0 kHz.

13. The micro-gyro device as set forth in claim 12, wherein:

the spaced resonance frequencies between each of the band-pass filters in the first plurality and second plurality of band-pass filters is about 62 Hz; and

respective central frequencies of the bandwidths of the first and second plurality of band-pass filters is about 6.0 kHz.

14. The micro-gyro device as set forth in claim 13, wherein each of the band-pass filters in the first plurality and second plurality of band-pass filters includes:

a respective resistor, the respective resonance frequencies of the band-pass filters being determined as a function of the resistances of the respective resistors.

15. The micro-gyro device as set forth in claim 10, wherein each the band-pass filters in the first plurality and the second plurality of band-pass filters have a Q of at least about 10 and a bandwidth of at least about 250 Hz at a central frequency of about 6.0 kHz.

16. The micro-gyro device as set forth in claim 10, wherein the first plurality and the second plurality of band-pass filters reduce higher order harmonics.

17. A method for filtering signals, the method comprising:

generating a driving signal;

creating an oscillation about a motor axis at a frequency determined as a function of the driving signal;

creating an oscillation about a rate axis, which is orthogonal to the motor axis, as a function of the frequency of the oscillation about the motor axis;

filtering a feedback signal representing the oscillation about the motor axis via a central frequency phase characteristic not exceeding about 0.1°

/Hz;

producing an output signal as a function of the oscillation around the rate axis; and

filtering the output signal via a central frequency phase characteristic not exceeding about 0.1°

/Hz.

18. The method for filtering signals as set forth in claim 17, further including:

maintaining an amplitude of the oscillation about the motor axis within a predetermined range as a function of the filtered feedback signal.

19. The method for filtering signals as set forth in claim 17, wherein:

the step of filtering the feedback signal includes reducing higher order harmonics; and

the step of filtering the output signal includes reducing the higher order harmonics.

20. The method for filtering signals as set forth in claim 17, wherein:

the step of filtering the feedback signal includes filtering the feedback signal through a bandwidth of about 250 Hz; and

the step of filtering the output signal includes filtering the output signal through a bandwidth of about 250 Hz.