Method and system for degimbalization of vehicle navigation data

• US 20070288165A1
• Filed: 05/26/2006
• Published: 12/13/2007
• Est. Priority Date: 05/26/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: May, Reed, Symonds, Michael, Willis, Jeff, Eckert, Charles, Sowada, Delroy, Vaujin, Michael, Shrader-Frechette, Maurice
• Granted Patent: US 7,409,292 B2
• Time in Patent Office: Days
• US Class Current: 701/220
• CPC Class Codes: G01C 21/18 Stabilised platforms, e.g. by gyroscope
• CPC Class Codes: H01Q 1/18 Means for stabilising antennas on an unstable platform

Abstract

A method and system for degimbalization of sensor outputs is provided. Data output from an embedded GPS inertial navigation system (EGI), which is mounted within a gimbaled system on a vehicle, is processed to provide degimballed navigation data. Generally, motion of the EGI is due to the vehicle motion and the gimbal motion. To provide navigation information relating solely to the vehicle, effects of the gimbal motion within the EGI outputs can be removed.

Claims

1. A method comprising:

receiving data from an inertial sensor mounted on a gimbal assembly that is positioned within a moving vehicle, wherein motion of the inertial sensor is due to motion of the gimbal assembly and motion of the moving vehicle, and wherein data output from the inertial sensor reflects the motion of the gimbal assembly and the motion of the moving vehicle;

receiving time-of-validity data for the inertial sensor data; and

removing effects of the motion of the gimbal assembly from the data to produce data approximately reflecting motion of the moving vehicle.

3. The method of claim 1, further comprising receiving data from an angular sensor that indicates an angular offset of the gimbal assembly with respect to the moving vehicle and corresponding time-of-validity data.

4. The method of claim 3, further comprising time synchronizing the data received from the inertial sensor and the data received from the angular sensor.

5. The method of claim 4, wherein removing effects of the motion of the gimbal assembly from the data to produce data approximately reflecting motion of the moving vehicle comprises applying a linear least squares curve fit to the data from the angular sensor to extrapolate an angular offset of the gimbal assembly at a time-of-validity for corresponding inertial sensor data.

6. The method of claim 5, further comprising determining an estimate of a gimbal angle rate data from a slope of the least squares curve fit.

7. The method of claim 6, further comprising applying a linear least squares curve fit to the gimbal angle rate data to extrapolate gimbal rate data at a time-of-validity for corresponding inertial sensor data.

8. The method of claim 1, wherein removing the effects of the motion of the gimbal assembly from the data to produce data approximately reflecting the motion of the moving vehicle comprises transforming the data from a frame of reference with respect to the gimbal into a frame of reference with respect to the moving vehicle.

9. The method of claim 8, wherein transforming the data from a frame of reference with respect to the gimbal into a frame of reference with respect to the moving vehicle comprises using direction cosine matrices (DCM) to transform the data having a first set of x,y,z axes to a second set of x,y,z axes.

10. The method of claim 9, wherein using the DCM to transform the data comprises:

multiplying a mathematical transformation that rotates axes of the inertial sensor to coincide with axes of the gimbal assembly by a mathematical transformation that rotates the axes of the gimbal assembly to coincide with axes of the moving vehicle to determine a mathematical transformation that rotates the axes of the inertial sensor to coincide with the axes of the moving vehicle.

11. The method of claim 10, wherein using the DCM to transform the data comprises:

multiplying the mathematical transformation that rotates the axes of the inertial sensor to coincide with the axes of the moving vehicle by a mathematical transformation that rotates axes of a local level navigation frame to coincide with the axes of the inertial sensor to determine a mathematical transformation that rotates the axes of a local level navigation frame to coincide with the axes of the moving vehicle.

12. The method of claim 11, further comprising determining an attitude of the moving vehicle within a frame of reference of the moving vehicle from the data output from the inertial sensor using the mathematical transformation that rotates the axes of a local level navigation frame to coincide with the axes of the moving vehicle.

2. (canceled)

13. A method for transforming gimbaled data output from an inertial sensor positioned on a gimbaled assembly within a moving vehicle into a frame of reference with respect to the moving vehicle, the method comprising:

receiving data output from the inertial sensor positioned on the gimbaled assembly, wherein the data reflects motion of the gimbaled assembly and motion of the moving vehicle;

receiving data output from an angular sensor that indicates an angular offset of the gimbaled assembly with respect to the moving vehicle;

synchronizing the data output from the inertial sensor and the data output from the angular sensor; and

removing effects of the motion of the gimbaled assembly from the data output from the inertial sensor to produce data approximately reflecting motion of the moving vehicle.

14. The method of claim 13, wherein removing the effects of the motion of the gimbaled assembly from the data output from the inertial sensor to produce data approximately reflecting motion of the moving vehicle comprises removing the angular offset of the gimbaled assembly from the data output from the inertial sensor.

15. The method of claim 13, wherein removing the effects of the motion of the gimbaled assembly from the data output from the inertial sensor to produce data approximately reflecting motion of the moving vehicle comprises transforming the data output from the inertial sensor from a frame of reference with respect to the gimbal into a frame of reference with respect to the moving vehicle.

16. A sensing device assembly comprising:

a sensing device mounted on a gimbaled assembly;

an Embedded Global Positioning System/Inertial Navigation System (EGI) mounted on the gimbaled assembly to provide data in a gimbaled frame of reference to the sensing device;

a gimbaled assembly angle sensor to provide outputs that indicate an angular offset of the gimbaled assembly; and

a processor for (i) receiving the data in the gimbaled frame of reference from the EGI and the outputs from the gimbaled assembly angle sensor, (ii) synchronizing the outputs from the EGI and the outputs from the gimbaled assembly angle sensor, and (iii) subtracting the outputs from the gimbaled assembly angle sensor from the outputs of the EGI.

17. The sensing device assembly of claim 16, wherein the sensing device is a Synthetic Aperture Radar (SAR).

18. The sensing device assembly of claim 16, wherein the EGI includes inertial sensors selected from the group consisting of gyroscopes and accelerometers.

19. The sensing device assembly of claim 16, wherein the processor applies a linear least squares curve fit to the data from the gimbaled assembly angle sensor to extrapolate an angular offset of the gimbaled assembly at a time-of-validity for corresponding EGI data.

20. The sensing device assembly of claim 19, wherein the processor removes effects of motion of the gimbaled assembly from the EGI data using the angular offset of the gimbaled assembly.