Micromachined acceleration and coriolis sensor

• US 5,656,778 A
• Filed: 04/24/1995
• Issued: 08/12/1997
• Est. Priority Date: 04/24/1995
• Status: Expired due to Term

• Current Assignee: Kearfott Corp. (Astronautics Corporation of America)
• Original Assignee: Kearfott Guidance and Navigation Corporation
• Inventors: Roszhart, Terry V.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/427,449
• Time in Patent Office: 841 Days
• Field of Search: 73/504.03, 73/504.04, 73/514.29, 73/504.02
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5656 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A solid state silicon micromachined acceleration and Coriolis (MAC) sensor that measures linear and angular motion. The MAC sensor is a single device that performs the functions of a conventional accelerometer and a gyroscope simultaneously. The MAC sensor is unique in that it is a differential dual stage device using only one micromachined proof mass to measure both linear and angular motions. The single proof mass is connected to opposing electromechanical resonators in a monolithic microstructure made from single crystal silicon. This unique design offers improvements in measurement performance and reductions in fabrication complexity that are beyond the state the art of earlier micromachined inertial sensors.

Claims

1. A micromachined accelaration an Coriolis sensor for measuring linear and angular motion, said sensor comprising:

a substrate having a proof mass, a plurality of resonators formed therein, and a frame-like main body portion surrounding said proof mass and said plurality of resonators, said plurality of resonators being formed between said proof mass and said main body portion thereby supporting said proof mass within said main body portion, said proof mass having a first natural resonant frequency, and said plurality of resonators each having a second natural resonant frequency, wherein said proof mass is capable of applying linear acceleration and rotational Coriolis forces to said plurality of resonators in response to linear and angular motion of said sensor, wherein at least two of said plurality of resonators are disposed on opposite sides of said proof mass;

a first plurality of electrodes disposed adjacent said proof mass, said first plurality of electrodes providing electrostatic forces to said proof mass thereby causing vibration of said proof mass at said first natural resonant frequency;

a second plurality of electrodes disposed adjacent said plurality of resonators, said second plurality of electrodes providing electrostatic forces to said plurality of resonators thereby causing vibration of said plurality of resonators at said second natural resonant frequency;

electronic circuitry for exciting said first plurality of electrodes and said second plurality of electrodes and for sensing modulations in said second natural resonant frequency of said plurality of resonators caused by said linear acceleration and rotational Coriolis forces so as to produce acceleration and rotation signals indicative of said linear and angular motion of said sensor;

means for mounting said first and second plurality of electrodes adjacent said proof mass; and

means for connecting said electronic circuitry to said first and second plurality of electrodes.

2. The sensor as defined in claim 1, wherein said first natural resonant frequency is smaller in magnitude than said second natural resonant frequency.

3. The sensor as defined in claim 1, wherein said means for mounting further comprises a pair of caps bonded to said substrate wherein said substrate is disposed between said pair of caps defining a sandwich assembly, and wherein said first plurality of electrodes and said second plurality of electrodes are disposed on at least one of said pair of caps and adjacent said substrate.

4. The sensor as defined in claim 3, wherein said pair of caps further comprises a top cap and a bottom cap, wherein said top cap is bonded to a top surface of said frame-like main body portion, wherein said bottom cap is bonded to a bottom surface of said frame-like main body portion, wherein said top and bottom caps have wells formed therein for allowing vibration of said proof mass at said first natural resonant frequency and for allowing vibration of said plurality of resonators at said second natural resonant frequency, wherein said wells are adjacent said proof mass and wherein said first and second plurality of electrodes are disposed within at least one of said wells.

5. The sensor as defined in claim 4, wherein said top cap has electroplated feedthrough holes formed therein for providing electrical connections between said electronic circuitry and said first plurality of electrodes and said second plurality of electrodes.

6. The sensor as defined in claim 1, wherein said electronic circuitry further comprises a proof mass oscillator for exciting said proof mass through said first plurality of electrodes.

7. The sensor as defined in claim 6, wherein said proof mass oscillator senses said first natural resonant frequency of said proof mass and provides a reference frequency output relating thereto.

8. The sensor as defined in claim 1, wherein said electronic circuitry further comprises at least one resonator oscillator for exciting said at least one resonator through said second plurality of electrodes.

9. The sensor as defined in claim 8, wherein said resonator oscillators sense modulations in said second natural resonant frequency of said plurality of resonators and provide frequency modulated outputs relating thereto.

10. The sensor as defined in claim 9, wherein said electronic circuitry further comprises demodulators for processing said frequency modulated outputs and for providing linear acceleration signals and rotational velocity signals.

11. The sensor as defined in claim 10, wherein said electronic circuitry further comprises a differential synchronous detector for processing said rotational velocity signals and for providing differential rotational velocity signals.

12. The sensor as defined in claim 10, wherein said electronic circuitry further comprises a differential frequency counter for processing said linear acceleration signals and for providing differential linear acceleration signals.

13. The sensor as defined in claim 1 further comprising at least one pair of opposing flexure supports connecting said proof mass to said frame-like main body portion thereby further supporting said proof mass within said frame-like main body portion.