No title available

• US 3,630,079 A
• Filed:
• Issued:
• Est. Priority Date: 03/27/1969
• Status: Expired due to Term

• Current Assignee: Halliburton Company
• Original Assignee: Halliburton Company
• Time in Patent Office: Days
• US Class Current: 73/178.00R
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence

Abstract

The disclosure is directed to a navigation system for a vessel including a radio navigation system for generating signals representative of the absolute position of the vessel. A second independent system utilizing radio signals from an orbiting satellite also generates signals representative of the absolute position of the vessel. Other sensors including an acoustic doppler, navigation unit, a water speed indicator and a gyrocompass generate signals which can be combined to produce a signal representative of the position of the vessel relative to a reference location. A computer combines each of the signals according to certain weighting functions in order to generate a resultant output signal which to a minimum mean squared error sense provides extremely accurate and reliable position information for the vessel.

Claims

1. A navigational system for a vehicle comprising:

at least one sensing system for generating a signal indicative of the absolute position of the vehicle, at least one other sensing system for generating a signal representative of the position of the vehicle relative to a reference location, and means for applying optimum weighting coefficients to said signals to vary the amplitude thereof, said weighting coefficients being determined in accordance with measurement error statistics of the respective systems and statistics of position determination to generate a resultant navigational signal having a minimum mean squared error thereby locating the absolute position of said vessel within a significantly reduced circle of error probability.

2. The system of claim 1 wherein said one sensing system comprises receivers for intermittently receiving radio signals transmitted from an orbiting satellite.

3. The system of claim 2 and further comprising:

radio navigation means for generating navigation data in response radio signals received from fixed transmitting stations.

4. The system of claim 3 and further comprising:

gyrocompass means for generating substantially real time representations of the vessel position relative to a location determined by said radio signals transmitted from the orbiting satellite.

5. The system of claim 4 and further comprising:

means for comparing the output signals from said radio navigation means and said gyrocompass means to generate an error signal, and means for correcting the resultant navigational signal in response to said error signal.

6. The system of claim 3 and further comprising:

means for correcting the output of said radio navigation means according to predetermined diUrnal variations.

7. A navigation system comprising:

means for generating position signals in response to reception of radio signals transmitted from known locations, said means including a satellite navigation system and a VLF radio navigation system, sensor means for generating speed and heading signals, means for combining said position signals and said speed and heading signals to produce a resultant navigational signal having a minimum mean squared error, means for comparing the position signals with said speed and heading signals to generate an error signal, and means responsive to said error signal for correcting said resultant navigation signal.

8. The navigation system of claim 7 wherein said means for generating speed and heading includes:

means for generating indications of water speed, gyrocompass means, and doppler radar means.

9. The navigation system of claim 7 wherein the means for comparing signals determines varying weighting coefficients for each signal according to the sensed relative accuracy of said resultant navigation signal.

10. The navigation system of claim 7 wherein said means for combining the position signals with the speed and heading signals comprises a digital computer.

11. The navigation system of claim 7 wherein said position and speed and heading signals are varied by weighting coefficients having magnitudes determined by a minimum means square error function, said function being dependent upon the relative accuracy of said means for generating position signals, said means for generating speed and heading signals, and the time interval between satellite radio signals.

12. The navigation system of claim 7 and further comprising:

first digital computer means responsive to the reception of radio signals from an orbiting satellite to generate digital signals representative of the absolute position of the vessel, and second digital computer means responsive to the output of said first digital computer means, said radio navigation means and said sensor means for generating said resultant navigation output.

13. A method of navigation comprising:

generating a first signal representative of the absolute position of a vehicle, generating a second signal representative of the position of the vehicle relative to a fixed known location, varying the magnitude of said first and second signals by applying weighting coefficients determined in accordance with preselected criteria including measurement error statistics associated with said first and second signals and statistics of position determination, and generating a minimum mean squared error resultant output navigation signal in response to the weighted first and second signals, said output navigational signal defining the absolute position of said vehicle in terms of latitude and longitude with a greater accuracy and reliability than either one of said first or second signals independently.

14. The method of claim 13 wherein said preselected criteria is further characterized as comprising:

a fixed relationship between the accuracy of said first and second signals, the speed of the vehicle, and the time intervals between new position fixes provided by said first and second signals.

15. The method of claim 14 wherein said first signal is generated in response to radio signals received from fixed remote locations.

16. The method of claim 14 wherein said second signal is generated in response to indications of the vehicle speed and heading.

17. The method of claim 14 and further comprising:

sensing said first and second signals, and decreasing the weighting of said signals in case of inaccuracies or inconsistencies induced by external factors.

18. The method of claim 13 wherein said first signal is generated in response to signals received from an orbiting satellite.

19. An all weather navigational system for accurately plotting the absolute location of a vessEl comprising:

a first sensing system for periodically receiving radio signals from an orbiting satellite to thereby accurately locate the absolute position of said vessel at a given point in time, a second sensing system including an EM log, gyrocompass, and VLF receivers to provide continuous navigation information during the interval between satellite signals, and means for combining signals from said first and second systems to provide a resultant minimum means squared error navigational signal that accurately plots a trajectory of the absolute position of the vessel between satellite signals, said combination of signals being effected by the determination of optimum weighting coefficients to be applied to each sensor output considering measurement error statistics of the respective sensors and statistics of the position determination.

20. A navigational system as set forth in claim 19 wherein said means for combining the signals from said first and second sensing systems include:

a first digital computer responsive to the reception of radio signals from said orbiting satellite;

a second digital computer responsive to the output of said first digital computer and said second sensing system, and formatting circuitry for translating the outputs of said first and second sensing systems to digital signals for inputs to said computers.