THREE-AXIS ACCELEROMETER

• US 3,680,392 A
• Filed: 10/08/1970
• Issued: 08/01/1972
• Est. Priority Date: 10/08/1970
• Status: Expired due to Term

• Current Assignee: Kearfott Guidance and Navigation Corporation
• Original Assignee: Jay Hoffman, Robert M. Hohenstein
• Inventors: Hoffman, Jay, Hohenstein, Robert M.
• Primary Examiner(s): Gill, James J.
• Application Number:
  US05/079,248
• Time in Patent Office: 663 Days
• Field of Search: 73/516R,517B,505
• US Class Current: 73/514.05
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A three-axis electrostatic accelerometer in which a proof mass is adapted to move relative to a casing with respect to three reference positions established along three coordinate axes, in response to accelerations along these axes. A signal is generated in response to the proof mass movement, and the proof mass is restored to a null position by means of an electrostatic force.

Claims

1. A three-axis accelerometer comprising a casing having an inner surface of spherical shape and having three coordinate axes arranged in quadrature, a proof mass having an outer surface of spherical shape and disposed in said casing forming a gap of spherical shape therebetween, force means to establish a reference position for said proof mass with respect to each of said three coordinate axes, said proof mass being adapted to move relative to said casing and with respect to said reference position in response to accelerations along said axes, pickoff means to generate a signal in response to said movement, said force means comprising at least three fixed ring-shaped capacitor plates fixedly mounted on said casing in proximity to said proof mass, said three force capacitor plates being arranged respectively along said three axes, each said force capacitor plate forming an electrical capacitor with at least a portion of said proof mass, said pickoff means comprising at least three fixed capacitor plates fixedly mounted on said casing in proximity to said proof mass, said three pickoff capacitor plates being arranged respectively along said three axes, each of said three pickoff capacitor plates being respectively coaxial with and surrounded by one of said three force capacitor plates, each said pickoff capacitor plate forming an electrical capacitor with at least a portion of said proof mass, means to establish an electrical circuit including said pickoff capacitor plates and said force capacitor plates, said movement of said proof mass adapted to vary the capacitances of said pickoff capacitor plates and to generate respective signals, said force capacitor plates being respectively responsive to said signal of its respective coaxial pickoff plate for applying an electrostatic force along its rEspective axis to said proof mass to realign said proof mass to its reference position, wherein said spherical gap between the proof mass and the casing contains a dielectric liquid, and wherein said proof mass includes an inner core portion and includes an outer membrane portion having an outer surface of spherical shape, said membrane portion being composed of a cationic-type material.

2. The accelerometer of claim 1 wherein said proof mass has a conductor, said conductor having one end fixedly connected to said proof mass inner portion and having an intermediate portion extending through said dielectric liquid and having an opposite end portion fixedly mounted on said casing, said conductor being composed of a flexible material.

3. The accelerometer of claim 2 wherein said casing is composed of a non-conductive material, said casing material being stable when in contact with said dielectric liquid, and wherein said dielectric liquid is composed of acetonitrile, and wherein said proof mass inner portion is composed of a metal.