Fully-coupled positioning system

• US 20010020216A1
• Filed: 03/14/2001
• Published: 09/06/2001
• Est. Priority Date: 11/20/1998
• Status: Active Grant

• Current Assignee: American GNC Corporation
• Original Assignee: American GNC Corporation
• Inventors: Lin, Ching-Fang
• Granted Patent: US 6,449,559 B2
• Time in Patent Office: Days
• US Class Current: 701/216
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/26 involving a sensor measurement for aiding acquisition or tracking
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A positioning system is disclosed for measuring a position of a vehicle on land, air, and space, using measurements from a global positioning system receiver and an inertial measurement unit. In the present invention, an integrated Kalman filter processes the all-available measurements of the global positioning system: pseudorange, delta range, carrier phase, and the solution of an inertial navigation system. The integrated Kalman filter is a multi-mode, robust kalman filter, in which optimal integrated mode is selected based on the measurement availability and filter stability. The high accurate solution of the inertial navigation system, which is corrected by the Kalman filter, is used to aid on-the-fly resolution of the carrier phase integer ambiguity of global positioning system in order to incorporate the carrier phase measurements into the Kalman filter, and to aid the carrier phase and code tracking loops of the receiver of the global positioning system to improve the receiver jamming and high dynamic resistance.

Claims

1. A fully-coupled positioning system, comprising:

a global positioning system (GPS) radio frequency (RF) unit for receiving global positioning system (GPS) radio frequency (RF) signals, amplifying said GPS RF signals and down converting said GPS RF signals into intermediate frequency (IF) signals;

a GPS digital signal processing unit for sampling said IF signal and deriving GPS pseudorange, delta range, and carrier phase measurements;

an IMU data sampling unit for collecting angular rate and acceleration measurements of said vehicle from an inertial measurement unit (IMU);

a centralized navigation Kalman filter for receiving and processing said GPS pseudorange, delta range, and carrier phase measurements for said GPS and said angular rate and acceleration measurements from said IMU;

wherein said centralized navigation Kalman filter computes an initial inertial navigation solution based on initial position, velocity, and attitude measurements;

wherein said centralized navigation Kalman filter resolves a carrier phase ambiguity to obtain carrier phase ambiguity numbers and detects cycle slip to obtain a plurality of slip cycles based on said GPS pseudorange, said delta ranges, said carrier phase measurements, and said inertial measurements;

wherein said centralized Kalman filter computes a fully-coupled positioning solution for each epoch;

at least an interface for realizing said data and control communication with other avionics systems; and

a time synchronizer for providing said time signal and local reference signal to said avionics system devices.

2. A fully-coupled positioning system, as recited in

claim 1

, further comprises of at least one external sensor carried by said vehicle, wherein said external sensor provides a plurality of initial attitude measurements for said vehicles.

3. A fully-coupled positioning system, as recited in

claim 1

, wherein said initial attitude measurements are provided from a GPS receiving set.

4. A fully-coupled positioning system, as recited in

claim 1

, wherein said inertial measurement unit is a tactical inertial measurement unit installed on a platform and said external sensor is a platform inertial measurement unit, wherein measurements or navigation parameters of said tactical inertial measurement unit and said platform inertial measurement unit are filtered by an alignment filter to provide optimal initialization information for said tactical inertial measurement unit.

5. A fully-coupled positioning system, as recited in

claim 1

, wherein said inertial measurement unit is a tactical inertial measurement unit installed on a platform, wherein measurements or navigation parameters of said tactical inertial measurement unit are filtered by an alignment filter to provide optimal initialization information for said tactical inertial measurement unit.

6. A fully-coupled positioning system, as recited in

claim 1

, said GPS frequency signals are tracked by a plurality of carrier phase locked loops and a plurality of code tracking loops of said GPS receiving set, and said carrier phase locked loops and said code tracking loops of said GPS receiving set are aided by said fully-coupled positioning solution.

7. A fully-coupled positioning system, as recited in

claim 1

, wherein a plurality of errors of said inertial navigation solution are removed with said optimal estimates of said inertial navigation solution errors.

8. A fully-coupled positioning system, as recited in

claim 1

, wherein said centralized Kalman filter is a multi-mode robust Kalman filter that selects an operation modes from the following operation modes:

a GPS/INS position and velocity integration mode, wherein said position vector and said velocity vector from said GPS receiving set are combined with said inertial navigation solution to derive an integrated navigation solution;

a GPS/IMU pseudorange and delta range integration mode, wherein said GPS pseudoranges and said delta ranges are combined with said inertial navigation solution to derive an integrated navigation solution;

a GPS/IMU pseudorange and delta range integration mode with aiding of GPS tracking loops, wherein said GPS pseudoranges and said delta ranges are combined with said inertial navigation solution to derive an integrated navigation solution, wherein said global positioning system radio frequency signals are tracked by a plurality of carrier phase locked loops and a plurality of code tracking loops of said GPS receiving set, and said carrier phase locked loops and said code tracking loops of said GPS receiving set are aided by said fully-coupled positioning solution obtained in step (g);

a GPS/IMU pseudorange, delta range, and carrier phase integration mode, wherein said GPS pseudoranges, said delta ranges, and said carrier phase measurements are combined with said inertial navigation solution to derive an integrated navigation solution; and

a GPS/IMU pseudorange, delta range, and carrier phase integration mode with aiding of GPS tracking loops, wherein said GPS pseudoranges, said delta ranges, and said carrier phase measurements are combined with said inertial navigation solution to derive an integrated navigation solution, wherein said global positioning system radio frequency signals are tracked by a plurality of carrier phase locked loops and a plurality of code tracking loops of said GPS receiving set, and said carrier phase locked loops and said code tracking loops of said GPS receiving set are aided by said fully-coupled positioning solution.

9. A fully-coupled positioning system, as recited in

claim 1

, wherein said angular rate and said acceleration measurements from said inertial measurement unit is processed to derive said inertial navigation solution, and is passed to said integrated Kalman filter, wherein a plurality of error estimates, which are provided by said integrated Kalman filter, are fed back to said inertial navigation solution to remove errors of said position vector, said velocity vector, and inertial sensors.

10. A fully-coupled positioning system, as recited in

claim 1

, wherein said GPS radio frequency signals are received by a GPS antenna and processed in a GPS RF/IF Unit, carrier and code tracking loops, an ambiguity resolution and a message decoding being passed to said integrated Kalman filter, wherein optimal velocity and acceleration information of said integrated Kalman filter are fed back to said carrier and code tracking loops to aid a GPS signal tracking process, moreover position, velocity, attitude from said inertial navigation solution being input to said ambiguity resolution to aid a GPS carrier phase integer ambiguity resolution.

11. A fully-coupled positioning system, as recited in

claim 1

, wherein said centralized Kalman filter determines said carrier phase ambiguity numbers;

when said carrier phase ambiguity numbers are not available, said centralized Kalman filter selects one of said GPS/IMU position and velocity integration mode, said GPS/IMU pseudorange and delta range integration mode, and said GPS/IMU pseudorange and delta range integration mode with aiding of GPS tracking loops;

when said carrier phase ambiguity numbers are available, said Kalman filter switches to one of said GPS/IMU pseudorange, delta range, and carrier phase integration mode and said GPS/IMU pseudorange, delta range, and carrier phase integration mode with aiding of GPS tracking loops.

12. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/INS P-V (position and velocity) integration mode and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode.

13. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/IMU pseudorange and delta range integration mode and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode.

14. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/IMU pseudorange and delta range integration mode with aiding of GPS tracking loops and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode.

15. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/INS position and velocity integration mode and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode with aiding of GPS tracking loops.

16. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/IMU pseudorange and delta range integration mode and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode with aiding of GPS tracking loops.

17. A fully-coupled positioning system, as recited in

claim 1

, wherein before obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter works in said GPS/IMU pseudorange and delta range integration mode with aiding of GPS tracking loops and derives an accurate integrated navigation solution which is used to reduce measurement errors in said GPS pseudorange, said delta ranges, and said carrier phase measurements so as to facilitate searching for said carrier phase ambiguity numbers;

wherein after obtaining said carrier phase ambiguity numbers said centralized navigation Kalman filter switches to said GPS/IMU pseudorange, delta range, and carrier phase integration mode with aiding of GPS tracking loops.