Axis alignment method

• US 6,276,203 B1
• Filed: 06/02/1999
• Issued: 08/21/2001
• Est. Priority Date: 02/08/1991
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Hulsing, Rand H. II
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US09/324,523
• Time in Patent Office: 811 Days
• Field of Search: 735/040.4, 735/040.2, 735/041.2, 735/10, 735/141.8, 735/142.9, 735/143.7, 735/143.8
• US Class Current: 73/504.03
• CPC Class Codes: F02G 1/044 having at least two working members, e.g. pistons, delivering power output
• CPC Class Codes: F02G 1/0445 Engine plants with combined cycles, e.g. Vuilleumier
• CPC Class Codes: F02G 2250/18 Vuilleumier cycles
• CPC Class Codes: F02G 2253/03 Stem seals
• CPC Class Codes: F16F 2230/0052 Physically guiding or influencing
• CPC Class Codes: F16F 2230/34 Flexural hinges
• CPC Class Codes: F16L 37/24 in which the connection is made by inserting one member axially into the other and rotating it to a limited extent, e.g. with bayonet action
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10S 73/01 Vibration

Abstract

An apparatus and method for determining the rate of angular rotation of a moving body and, in particular, for alignment of the dither motion and the Coriolis acceleration sensing direction in a sensor adapted to be formed, i.e. micromachined, from a silicon substrate.

Claims

1. An apparatus for measuring the specific force and angular rotation rate of a moving body, comprising:

a) a monolithic substrate having first and second substantially planar surfaces disposed substantially parallel to each other and an epitaxial layer adhered to at least one of said first and second planar surfaces;

b) a first accelerometer formed of said substrate and having a first force sensing axis for producing a first output signal indicative of the acceleration of the moving body along said first force sensing axis, said first accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

c) a second accelerometer formed of said substrate and having a second force sensing axis for producing a second output signal indicative of the acceleration of the moving body along said second force sensing axis, said second accelerometer having a proof mass, a support frame, and at least one flexure connecting said proof mass to said support frame;

d) a dither frame formed of said substrate;

e) a first pair of S-bend flexures connected between said support frame of said first accelerometer and said dither frame, and a second pair of S-bend flexures connected between said support frame of said second accelerometer and said dither frame, said S-bend flexures being formed of said substrate for mounting said first and second accelerometers such that said first and second force sensing axes are both oriented at substantially the same angle with respect to said first and second surfaces and such that said first and second accelerometers can be moved along a vibration axis substantially perpendicular to each of said first and second sensing axes;

f) a drive circuit coupled to each of said first and second accelerometers for imparting a dithering motion thereto of a predetermined frequency along said vibration axis;

g) said substrate having a rate axis substantially perpendicular to each of said first and second force sensing axes and said vibration axis; and

h) first and second axis alignment features, said first axis alignment feature disposed between said first accelerometer and said dither frame and rotating one of said first pair of S-bend flexures in response to a first rotational drive signal and said second axis alignment feature disposed between said second accelerometer and said dither frame and rotating one of said second pair of S-bend flexures in response to a second rotational drive signal, whereby said dithering motion is orthogonally aligned with said rate axis and said first and second output signals have a Coriolis component indicative of the angular rotation of the moving body about said rate axis.

2. The specific force and angular rotation rate measuring apparatus recited in claim 1, wherein each of said first and second axis alignment features further comprise:

a torsionally compliant flexure extending between said S-bend flexure and said dither frame; and

a force member mechanically coupled to said dither frame and oriented to impart a torsional force to said torsionally compliant flexure.

3. The specific force and angular rotation rate measuring apparatus recited in claim 2, wherein each said force member includes a highly resistive conductor deposited thereon.

4. The specific force and angular rotation rate measuring apparatus recited in claim 3, further comprising an electrical circuit generating a current in said highly resistive conductor deposited on one or more of said force members, whereby the temperature of said one or more force members is elevated relative to another of said force members.

5. The specific force and angular rotation rate measuring apparatus recited in claim 2, wherein said torsionally compliant flexure is formed in said substrate and said force member is formed in said epitaxial layer.

6. The specific force and angular rotation rate measuring apparatus recited in claim 5, wherein said force member further comprises two or more spaced apart parallel beams.

7. The specific force and angular rotation rate measuring apparatus recited in claim 5, therein said torsionally compliant flexure comprises a plurality of struts projecting radially from a common longitudinal axis.

8. The specific force and angular rotation rate measuring apparatus recited in claim 7, wherein said radially projecting struts form an X-shape extruded along said common longitudinal axis.

9. The specific force and angular rotation rate measuring apparatus recited in claim 8, wherein said struts are joined at said common longitudinal axis into an integrated X-shaped torsionally compliant flexure.

10. The specific force and angular rotation rate measuring apparatus recited in claim 8, wherein said struts forming said X-shaped torsionally compliant flexure are mechanically coupled at their first and second ends.

11. The specific force and angular rotation rate measuring apparatus recited in claim 2, wherein said force member acts on said torsionally compliant flexure through one or more struts disposed between said force member and said torsionally compliant flexure.

12. The specific force and angular rotation rate measuring apparatus recited in claim 2, wherein said force member acts on said torsionally compliant flexure through one or more levers pivotally suspended between said force member and said torsionally compliant flexure.