TETHERED, LEVITATED-MASS ACCELEROMETER

• US 20120240679A1
• Filed: 12/16/2010
• Published: 09/27/2012
• Est. Priority Date: 12/16/2009
• Status: Active Grant

• Current Assignee: Y-Sensors, Ltd.
• Original Assignee: Y-Sensors, Ltd.
• Inventors: Netzer, Yishay, Aharon, Oren, Girgel, Michael
• Granted Patent: US 8,984,941 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• 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

The present invention has three aspects: 1. A concept for a force-balanced accelerometer in which the proof mass is levitated inside an enclosure and has an electrically conductive path to the enclosure. 2. A planar Implementation of the invention. 3. Implementation of the invention using MEMS (Micro Electro Mechanical System) technology.

Claims

1. A force-balance accelerometer including X, Y and Z rectilinear reference axes and θ

, φ

, and Ψ

angular reference axes for measuring components of rectilinear acceleration relative to said 3 rectilinear reference axes and for measuring the components of angular acceleration relative to said 3 angular reference axes. The accelerometer comprising;

a) an enclosure having a null position in each of said rectilinear reference axis and in each said angular reference axis,

b) a proof mass included inside said enclosure and movable relative to each of said reference axes, and

c) at least one electrically conductive tether which is flexible in 6 degrees of freedom constituting an electrically conductive link between said proof mass and said enclosure said enclosure including a plurality of capacitive plates for sensing the position of said proof mass relative to the null position of each said 3 rectilinear axes and of each said 3 angular axes and for applying electrostatic forces on said proof mass along each of said in 3 rectilinear axes and for applying electrostatic torques on said proof mass around each of said 3 angular axes,

said accelerometer including 3 force balancing control loops for positioning said proof mass in each said rectilinear null position and 3 force balancing control loops for positioning said proof mass in each said angular null position.

2. An accelerometer as in claim 1 wherein said tether includes at least one spiral.

3. A planar accelerometer as in claim 1 fabricated using micromechanical technologies and comprising:

a) a top layer;

b) an intermediate device layer; and

c) a bottom layer,

said top and bottom layers being spaced apart to constitute at least part of said enclosure, said proof mass and said tether being fabricated by etching the device layer, the inner surfaces of said bottom and top layers include a plurality of capacitive plates on their inner surfaces employed for sensing a position of the proof mass within said enclosure, wherein a first end of said tether extends from the proof mass and a second end of the tether extends from at least one of said top and bottom layers.

4. An accelerometer as in claim 3 wherein the capacitive plates that serve the X and Y and θ

axes are capacitive (electrostatic) comb drives formed within said intermediate device layer.

5. An accelerometer as in claim 1 wherein the flexible tether includes at least one serpentine member.