Inertial measurement unit with gas plenums

• US 7,762,133 B2
• Filed: 07/17/2007
• Issued: 07/27/2010
• Est. Priority Date: 07/17/2007
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bowen, David A., Chappell, Charles D.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US11/778,965
• Publication Number:
  US 20100024550A1
• Time in Patent Office: 1,106 Days
• Field of Search: 734/93, 735/10, 735/140.1, 731/78.R, 701/220
• US Class Current: 73/493
• CPC Class Codes: F16C 2370/00 Apparatus relating to physics, e.g. instruments
• CPC Class Codes: F16C 32/0622 via nozzles, restrictors
• CPC Class Codes: F16C 32/0666 of bearing pads
• CPC Class Codes: G01C 19/20 in fluid
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values

Abstract

An inertial measurement unit comprises a mounting plate with an opening therethrough, and a sensor assembly disposed in the opening of the mounting plate. Upper and lower support shells having shell flanges are attached to upper and lower surfaces of the mounting plate. The upper and lower support shells surround the sensor assembly. A plurality of gas bearing pads each extends through apertures in the upper and lower support shells. Upper and lower gas plenums have plenum flanges attached to the shell flanges of the upper and lower support shells, with the upper and lower gas plenums surrounding the upper and lower support shells. Pressure relief valves are coupled to the plenum flanges of the upper and lower gas plenums. The gas bearing pads and the sensor assembly are separated by a gap when pressurized gas is fed into the upper and lower gas plenums, thereby creating a gas bearing that allows the sensor assembly to be freely suspended and rotated in all directions.

Claims

1. An inertial measurement unit, comprising:

a mounting plate with an upper surface, a lower surface, and an opening therethrough;

a sensor assembly disposed in the opening of the mounting plate;

an upper support shell having a shell flange attached to the upper surface of the mounting plate, the upper support shell surrounding an upper portion of the sensor assembly and having a plurality of apertures;

a lower support shell having a shell flange attached to the lower surface of the mounting plate, the lower support shell surrounding a lower portion of the sensor assembly and having a plurality of apertures;

a plurality of gas bearing pads extending through the apertures in the upper and lower support shells, the plurality of gas bearing pads configured to receive pressurized gas;

an upper gas plenum having a plenum flange attached to the shell flange of the upper support shell, the upper gas plenum surrounding the upper support shell;

a first pressure relief valve coupled to the plenum flange of the upper gas plenum;

a lower gas plenum having a plenum flange attached to the shell flange of the lower support shell, the lower gas plenum surrounding the lower support shell; and

a second pressure relief valve coupled to the plenum flange of the lower gas plenum;

wherein the gas bearing pads and the sensor assembly are separated by a gap when pressurized gas is fed into the upper and lower gas plenums, thereby creating a gas bearing that allows the sensor assembly to be freely suspended and rotated in all directions.

2. The inertial measurement unit of claim 1, wherein the sensor assembly comprises an outer shell with a substantially spherical shape.

3. The inertial measurement unit of claim 1, wherein the upper and lower gas plenums each comprise an outer casing with a side portion having a first thickness and a rim portion having a second thickness greater than the first thickness.

4. The inertial measurement unit of claim 3, wherein the side portions of the outer casings gradually taper in thickness to the rim portions.

5. The inertial measurement unit of claim 1, wherein the upper and lower gas plenums are each adapted to provide radiation shielding.

6. The inertial measurement unit of claim 1, further comprising:

a first O-ring disposed in a slot that circumscribes the shell flange of the upper support shell; and

a second O-ring disposed in a slot that circumscribes the shell flange of the lower support shell;

wherein the first and second O-rings respectively provide a fluid-tight seal between the shell flanges of the upper and lower support shells and the corresponding plenum flanges attached thereto.

7. The inertial measurement unit of claim 3, further comprising an O-ring disposed in a slot on a surface of a lip portion of the upper and lower support shells, the O-ring providing a fluid-tight joint between the lip portions and the rim portions of the gas plenums.

8. The inertial measurement unit of claim 1, wherein the upper and lower support shells have a substantially hemispherical shape, and the upper and lower gas plenums have a substantially hemispherical shape.

9. The inertial measurement unit of claim 1, wherein the sensor assembly comprises one or more inertial sensors.

10. The inertial measurement unit of claim 9, wherein the inertial sensors comprise one or more accelerometers, gyroscopes, velocity meters, or combinations thereof.

11. The inertial measurement unit of claim 1, further comprising a plurality of gas jet nozzles coupled to the mounting plate, the gas jet nozzles configured to provide three-dimensional rotation of the sensor assembly.

12. The inertial measurement unit of claim 1, further comprising at least one gas inlet in the mounting plate for feeding gas into the upper gas plenum, and at least one gas inlet in the mounting plate for feeding gas into the lower gas plenum.

13. The inertial measurement unit of claim 1, wherein the lower gas plenum is set in a support frame attached to the mounting plate.

14. The inertial measurement unit of claim 1, further comprising a monitoring device placed in openings of the upper gas plenum and the upper support shell, the monitoring device configured to monitor rotation and position of the sensor assembly.

15. The inertial measurement unit of claim 1, further comprising an upper gas outlet in the upper gas plenum, and a lower gas outlet in the lower gas plenum.

16. The inertial measurement unit of claim 1, wherein the gas bearing pads are substantially evenly spaced around the upper and lower support shells.

17. The inertial measurement unit of claim 2, wherein the gas bearing pads each comprise:

a hollow stem defining a plenum, the hollow stem having an inlet and an outlet;

an elastomeric joint having an opening therethrough and coupled to the hollow stem over the outlet;

a gas bearing cup having a cavity surface with an aperture therethrough and coupled to the elastomeric joint; and

a porous material on the cavity surface, wherein the porous material has a concave-shaped surface that faces a convex curvature of the spherical outer shell of the sensor assembly.

18. The inertial measurement unit of claim 1, wherein the gas bearing pads are configured to receive pressurized gas from the upper and lower gas plenums.

19. The inertial measurement unit of claim 1, wherein the upper and lower gas plenums are configured to operate at different gas pressures.

20. An inertial measurement unit, comprising:

an upper gas plenum comprising an upper outer casing with a side portion having a first thickness and a rim portion having a second thickness greater than the first thickness;

a lower gas plenum comprising a lower outer casing with a side portion having a first thickness and a rim portion having a second thickness greater than the first thickness of the rim portion of the lower outer casing;

an upper support shell surrounded by the upper gas plenum, the upper support shell having a plurality of apertures;

an upper gas chamber between the upper outer casing and the upper support shell;

a lower support shell surrounded by the lower gas plenum, the lower support shell having a plurality of apertures;

a lower gas chamber between the lower outer casing and the lower support shell;

a sensor assembly surrounded by the upper and lower support shells;

a plurality of gas bearing pads extending through the apertures in the upper and lower support shells, the plurality of gas bearing pads configured to receive pressurized gas from the upper and lower gas chambers;

wherein the gas bearing pads and the sensor assembly are separated by a gap when pressurized gas is fed into the upper and lower gas chambers, thereby creating a gas bearing that allows the sensor assembly to be freely suspended and rotated in all directions.