Electrostatic accelerometer

• US 4,583,404 A
• Filed: 02/28/1984
• Issued: 04/22/1986
• Est. Priority Date: 02/28/1983
• Status: Expired due to Term

• Current Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Original Assignee: Office National D'Etudes et de Recherches Aerospatiales
• Inventors: Bernard, Alain M., Sacleux, Bernard
• Primary Examiner(s): Levy, Stewart J.
• Assistant Examiner(s): Chapman, Jr., John E.
• Application Number:
  US06/584,405
• Time in Patent Office: 784 Days
• Field of Search: 73/517 B
• US Class Current: 73/514.18
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A tridimensional electrostatic accelerometer comprises a cube-shaped test ight. On each of the six faces of the cube is a pair of conducting electrodes. A hollow cage accommodates the test weight and twelve electrodes on the cage to form, with the test weight electrodes, three sets of four capacitors C_ij, where i varies from 1 to 4 and j is x, y and z respectively. Measurements are made for each value of j of the sums and differences of the capacities

(C.sub.1 -C.sub.2).sub.j (C.sub.3 -C.sub.4).sub.j

(C.sub.1 +C.sub.2).sub.j (C.sub.3 +C.sub.4).sub.j

From these quantities voltages are derived for positioning the test weight. The voltages are applied selectively to the electrodes of the set of capacitors C_ij.

Claims

1. A tridimensional electrostatic accelerometer comprising:

a cube-shaped test weight having six faces;

a pair of conducting electrodes on each of the six faces of said cube-shaped test weight, two of said electrodes being adjacent on each face and the electrodes on two parallel faces of the cube being opposite two by two, whereby each first electrode on a face has an adjacent second electrode on the same face, an opposite third electrode on the parallel face and a diagonally opposite fourth electrode on said parallel face, the electrodes thereby forming three sets of four electrodes, each set comprising one of said first electrodes, one of said adjacent second electrodes, one of said opposite third electrodes and one of said diagonally opposite fourth electrodes, each of said sets being respectively associated with a given one among three orthogonal coordinate axes;

a hollow cage accomodating said test weight;

twelve electrodes on said cage, forming with the test weight electrodes three sets of four capacitors C_ij, where i varies from 1 to 4 and j is selectively each x, y and z, respectively associated with said orthogonal coordinate axes;

means for measuring for each value of j the quantities

space="preserve" listing-type="equation">(C.sub.1 -C.sub.2).sub.j (C.sub.3 -C.sub.4).sub.j

space="preserve" listing-type="equation">(C.sub.1 +C.sub.2).sub.j (C.sub.3 +C.sub.4).sub.j ;

means for forming with said above quantities signals indicative of;

space="preserve" listing-type="equation">V.sub.tr,j =(C.sub.1 +C.sub.3).sub.j -(C.sub.2 +C.sub.4).sub.j

space="preserve" listing-type="equation">V.sub.rot,j =(C.sub.3 -C.sub.4).sub.j -(C.sub.1 -C.sub.2).sub.j ;

means responsive to the signals representing V_tr,j and V_rot,j for;

applying a voltage proportional to -V_tr,j +V_rot,j across the capacitor including said first electrode of an electrode set,

and applying a voltage proportional to V_tr,j -V_rot,j across the capacitor including said third opposite electrode of said set,

and applying a voltage proportional to V_tr,j +V_rot,j across the capacitor including said second adjacent opposite electrode of said set,

and applying a voltage proportional to -(V_trj, +V_rot,j) across the capacitor including said fourth diagonally opposite electrode of said set.

2. A three dimensional electrostatic accelerometer comprising:

a test weight shaped as a parallelpiped having first, second and third sets of faces, a pair of parallel faces being included in each set, the faces of said first, second and third sets being mutually orthogonal, each set of faces being at right angles to separate mutually orthogonal axes x, y and z of the test weight,

a first pair of electrodes on each face whereby there are first, second and third sets of said first pair of electrodes and a total of twelve separate electrodes on the test weight, the electrodes on each face being on opposite sides of the axis intersecting the particular face;

first, second and third sets of fixed second electrodes, each set of second electrodes including two further pairs of electrodes, the first, second and third sets of second electrodes being mutually orthogonal along said x, y and z axes, the first, second and third sets of second electrodes being nominally parallel to and aligned with corresponding electrodes of the first, second, and third sets of first electrodes, respectively, whereby a separate capacitor is formed between each of the corresponding electrodes and twelve separate capacitors are thereby formed by the electrodes with four capacitors C_i being provided for each of axes x, y and z, where i is selectively each of 1 to 4, capacitors C₁, C₂, C₃ and C₄ of each of axes x, y and z respectively including first, second, third and fourth electrodes of the first set, the first and second electrodes of each axis j being positioned on the same one of said faces perpendicular to axis j, where j is selectively each of axes x, y and z, the third and fourth electrodes of said axis j being positioned on the other one of said faces perpendicular to said axis j, the first and third electrodes of axis j being on the same one side of said axis j, the second and fourth electrodes of axis j being on the same other side of said axis j;

means responsive to the capacitances C₁, C₂, C₃ and C₄ for each of said axes j for deriving signals representing;

space="preserve" listing-type="equation">V.sub.tr,j =(C.sub.1 +C.sub.3).sub.j -(C.sub.2 +C.sub.4).sub.j

space="preserve" listing-type="equation">V.sub.rot,j =(C.sub.3 -C.sub.4).sub.j -(C.sub.1 -C.sub.2).sub.j ;

means responsive to the signals representing V_tr,j and V_rot,j for;

(a) applying a voltage proportional to -V_tr,j +V_rot,j across capacitor C₁ of axis j,

(b) applying a voltage proportional to V_tr,j -V_rot,j across capacitor C₃ of axis j,

(c) applying a voltage proportional to V_tr,j +V_rot,j across capacitor C₂ of axis j, and

(d) applying a voltage proportional to -(V_tr,j +V_rot,j) across capacitor C₄ of axis j.

3. The accelerometer of claim 2 wherein the test weight is shaped as a cube including the first, second and third sets of faces.