Communications: directive radio wave systems and devices (e.g. – Directive – Position indicating
Reexamination Certificate
2000-08-16
2003-05-13
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Position indicating
C342S357490
Reexamination Certificate
active
06563461
ABSTRACT:
TECHNICAL FIELD
The present invention concerns position-measurement systems and methods, particularly methods of using range measurements to estimate position.
BACKGROUND OF THE INVENTION
Some position measurement systems use radio signals broadcast from transmitters to measure the position of a radio receiver that receives the radio signals. A seminal example of one such system is a global positioning system.
The typical global positioning system (GPS) measures the three-dimensional, global position of a radio receiver. The receiver, sometimes mounted to a vehicle such as an automobile or aircraft, receives signals from a set of earth-orbiting satellite transmitters. Each signal indicates not only the position of its transmitter but also its is transmission time, enabling the receiver to approximate signal transit times and to estimate or measure the distances to the transmitters. A processor coupled to the receiver uses at least four of these measured distances, known as range measurements, to approximate or estimate the position of the receiver and the associated vehicle.
Estimating the position of the receiver from the range measurements generally entails solving a set of nonlinear range equations using an iterative calculation process. The iterative process entails starting with an initial position estimate, computing a second estimate using the initial estimate, computing a third estimate using the second estimate, and so on, with each successive estimate being better than the previous one and thus converging toward the actual receiver position. This process continues until the change between successive position estimates become insignificantly small.
Unfortunately, this iterative process is not only time consuming, but often fails to converge toward the actual receiver position when the receiver is not between the earth and the earth-orbiting satellite transmitters. Thus, for example, vehicles traveling in space outside the constellation of satellite transmitters cannot rely on a global positioning system for navigation.
In trying to solve these problems, others have sought to develop non-iterative, or closed-form, solutions to the range equations. See, for example, Bancroft and Chaffee, “An Algebraic Solution of the GPS Equation,” IEEE Trans on Aerospace and Elect Systems, January 1985. However, this and other approaches have not been entirely acceptable, because they either fail to consistently converge on a single solution or give multiple solutions to the pseudorange equations, and thus require further analysis to pick the right one.
Accordingly, there remains a need for better ways of estimating position from range measurements.
SUMMARY OF THE INVENTION
To address this and other problems, the inventors devised new methods as well as systems and software embodying these methods, for using range measurements to estimate position. One exemplary method entails receiving a set of two or more range measurements; defining an error function based on the set of range measurements, with the error function having only one local minimum; and then determining a position estimate based the one local minimum of the error function. Other embodiments use this position estimate as an initial position estimate in an iterative process, such as Kalman filtering, to promote its rapid and consistent convergence to an appropriate position solution.
One exemplary application for this and other embodiments of the invention is GPS-based position estimation for spacecraft outside a GPS satellite constellation. Other applications include position estimation of cellular phones outside a triangle of three base towers, and in distributed robotic systems, position estimation of scout robots outside a triangle of three ranger robots.
REFERENCES:
patent: 5740048 (1998-04-01), Abel et al.
patent: 5914686 (1999-06-01), Schipper
patent: 5986603 (1999-11-01), Schipper
MATLAB Worksheet for 09/640,129.*
Abel, J.S., et al., “Existence and Uniqueness of GPS Solutions”,IEEE Transactions on Aerospace And Electronic Systems, 27(6), pp. 952-956, (Nov. 1991).
Bancroft, S., “An Algebraic Solution of the GPS Equations”,IEEE Transactions on Aerospace and Electronic Systems, AES-21(7), pp. 56-59, (Jan. 1985).
Biton, I., et al., “Direct Solution of the GPS Equations”,The 9th International Technical Meeting of The Satellite Division of the Institute of Navigation, ION GPS-96, Part 2 of 2, Kansas City Convention Center, Kansas City, Missouri, pp. 1313-1320, (1996).
Chaffee, J., et al., “GPS Positioning, Filtering, And Integration”,IEEE National Aerospace and Electronics Conference, NAECON, Held at the Dayton Convention Center, pp. 327-332, (1993).
Chaffee, J., et al., “On the Exact Solutions of Pseudorange Equations”,IEEE Transactions on Aerospace and Electronic Systems, 30(4), pp. 1021-1030, (Oct. 1994).
Chaffee, J.W., et al., “Bifurcation of Pseudorange Equations”,Proceedings of the National Technical Meeting, pp. 203-211, (1993).
Chaffee, J.W., et al., “The GPS Filtering Problem”,IEEE, pp. 12-20, (1992).
Hoshen, J., “The GPS Equations and the Problem of Apollonius”,IEEE Transactions on Aerospace and Electronic Systems, 32(3), pp. 1116-1124, (Jul. 1996).
Krause, L.O., “A Direct Solution to GPS-Type Navigation Equations”,IEEE Transactions on Aerospace And Electronic Systems, AES-23(2), pp. 225-232, (Mar. 1987).
Rudel, M., et al., “GPS Relative Accuracy for Collision Avoidance”,Proceedings of the National Technical Meeting, pp. 971-977, (1997).
Elgersma M: “Initial Solution of Pseudo-Range Equations” Workshop Mathematical Challenges in Global Positioning Systems (GPS), Aug. 16-18, 2002, Institute for Mathematics and Its Applications (IMA), University of Minnesota, Online! XP002196393 Retrieved from the Internet: URL:http://www.ima.umn.edu/gps/abstract/elgersma1.html retrieved on Apr. 15, 2000! Abstract.
Leva J L: “An Alternative Closed-Form Solution to the GPS Pseudo-Range Equations” IEEE Transactions on Aerospace and Electronic Systems, IEEE Inc., New York, US, vol. 32, No. 4, Oct. 1, 1996, pp. 1430-1439, XP000688912, ISSN: 0018-9251 Section “Introduction”.
Elgersma Michael R.
Morton Blaise G.
Honeywell International , Inc.
Mull Fred H
Tarcza Thomas H.
LandOfFree
System, method, and software for non-iterative position... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System, method, and software for non-iterative position..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System, method, and software for non-iterative position... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3068959