Navigation and positioning system and method using uncoordinated beacon signals in conjunction with an absolute positioning system

• US 5,774,829 A
• Filed: 12/12/1995
• Issued: 06/30/1998
• Est. Priority Date: 12/12/1995
• Status: Expired due to Term

• Current Assignee: Pinterra Corporation
• Original Assignee: Pinterra Corporation
• Inventors: Kelley, David C., Cisneros, Joseph S., Kiang, Michael, Greenbaum, Louis A.
• Primary Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US08/570,747
• Time in Patent Office: 931 Days
• Field of Search: 364/449.8, 364/449.95, 364/449.1, 364/460, 364/452, 342/357, 342/457, 340/995, 701/214, 701/216, 701/207, 701/300, 701/219
• US Class Current: 701/213
• CPC Class Codes: G01S 19/03 Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/10 providing dedicated supplementary positioning signals
• CPC Class Codes: G01S 19/26 involving a sensor measurement for aiding acquisition or tracking
• CPC Class Codes: G01S 19/31 Acquisition or tracking of other signals for positioning
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
• CPC Class Codes: G01S 5/145 Using a supplementary range measurement, e.g. based on pseudo-range measurements
• CPC Class Codes: H04B 7/18552 using a telephonic control signal and a second ranging satellite determining absolute distances from a plurality of spaced points of known location G01S5/14

Abstract

A navigation system in which an uncoordinated beacon positioning system (UBS) is used in conjunction with an absolute positioning system (APS) is described herein. The UBS employs a multiplicity of transmitters, at known locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters. Within a mobile unit, separate receivers are provided for receiving these beacon signals and for receiving APS signals. The absolute positioning system (APS) receiver is disposed to receive the APS signals, and to estimate an initial position of the mobile unit therefrom. The mobile unit processor is disposed to modify the estimated mobile unit position on the basis of the detected beacon signal phases. The mobile unit processor may also be programmed to determine the uncertainty of location information provided by the beacon signal receiver and by the APS receiver. This allows the current location of the mobile unit to be updated by selecting the location estimate having associated therewith the least amount of location uncertainty, or by weighting each estimate based on its uncertainty and combining the two weighted location estimates. In another implementation, the mobile unit includes an estimator operative to compute an estimate of mobile unit position on the basis of selected pseudorange measurements from the UBS and APS receivers. The estimator may include a Kalman filter configured to process residual pseudorange information provided by the UBS and APS receivers.

Claims

1. A positioning system for determining location of a mobile unit, said system making use of a multiplicity of transmitters, at known locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals being of a predetermined repetition rate, said system comprising:

an uncoordinated beacon positioning subsystem (UBS), said subsystem including a UBS receiver for receiving said beacon signals and for providing a UBS location of said mobile unit;

an absolute positioning subsystem (APS) including an APS receiver for receiving APS signals and for providing an APS location of said mobile unit; and

a processor for determining uncertainty of location information provided by said beacon signal receiver and said APS receiver, and updating a current location of said mobile unit based on said UBS and APS locations and said uncertainty of said location information;

wherein the processor determines the uncertainty of location information for the APS receiver by measuring and evaluating at least one signal parameter associated with the APS signals, and determines the uncertainty of location information for the UBS receiver by measuring and evaluating at least one signal parameter associated with the received beacon signals.

2. The positioning system of claim 1, wherein said APS receiver comprises a global positioning system (GPS) receiver for receiving GPS signals, said processor including software for computing an indication of quality of location information provided by said GPS receiver.

3. The positioning system of claim 1, wherein said UBS receiver includes logic for computing an indication of quality of said UBS location.

4. The positioning system of claim 1, wherein said processor includes software for assigning said APS location to said UBS location when uncertainty of location information provided by said APS receiver is determined to be less than uncertainty of location information provided by said UBS receiver.

5. The positioning system of claim 1, wherein said processor includes software for assigning said APS location to said UBS location when uncertainty of location information provided by said UBS receiver is determined to exceed a predetermined level.

6. The positioning system of claim 1, wherein said UBS receiver includes a beacon signal receiver for receiving at least two of said beacon signals, said beacon signal receiver including phase detection circuitry for detecting the phases of at least three of said beacon signals at the location of said mobile unit, and processor for computing said UBS location based on said detected phases and on an initial location estimate provided by said APS receiver.

7. The positioning system of claim 1, wherein said processor includes software for assigning said UBS location to said APS location when uncertainty of location information provided by said APS receiver is determined to exceed a predetermined level.

8. The positioning system of claim 1, wherein said UBS receiver also receives local traffic information from one of said multiplicity of transmitters, said local traffic information being useable for navigation.

9. The positioning system of claim 1, wherein the processor, when the determined uncertainty of the UBS location is less than the determined uncertainty of the APS location, updates the current position in a manner selected from the set consisting of (A) based solely on the UBS location, and (B) based on a weighted combination of the UBS and APS locations wherein the UBS location is weighted more heavily than the APS location.

10. A positioning system for determining position of a mobile unit, comprising:

a multiplicity of transmitters, at known locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency;

a first receiver, at a known location relative to the locations of said multiplicity of transmitters, which (A) receives said beacon signals, (B) determines the relative phases of said beacon signals, and (C) broadcasts phase data representing said relative phases;

a second receiver, disposed within said mobile unit, which receives said broadcast phase data from said first receiver and at least three of said beacon signals, said second receiver including phase detection circuitry for detecting the phases of said beacon signals at the location of said mobile unit, and data processing circuitry for computing a first estimated location of said mobile unit based on said broadcast values and said detected phases;

an absolute positioning system (APS) receiver, disposed within said mobile unit, for receiving APS signals and for providing a second estimated location of said mobile unit; and

a processor for evaluating positional uncertainty in said first and second estimated locations, and for updating a current position of said mobile unit based on said first and second estimated locations of said mobile unit and said positional uncertainty;

wherein the processor determines the uncertainty of the first estimated location by measuring and evaluating at least one signal parameter associated with the beacon signals, and determines the uncertainty of the second estimated location by measuring and evaluating at least one signal parameter associated with the received APS signals.

11. The positioning system of claim 10, wherein the processor, when the determined uncertainty of the first estimated location is less than the determined uncertainty of the second estimated location, updates the current position in a manner selected from the set consisting of (A) based solely on the first estimated location, and (B) based on a weighted combination of the first and second estimated locations wherein the first estimated location is weighted more heavily than the second estimated location.

12. A positioning system, comprising:

a multiplicity of transmitters, at known locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters;

each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency; and

a mobile unit including;

a beacon signal receiver for receiving at least three of said beacon signals, said beacon signal receiver including phase detection circuitry for detecting the phases of the at least three of said beacon signals received thereby,

an absolute positioning system (APS) receiver for receiving APS signals and for estimating an initial position of said mobile unit therefrom, and

a processor for computing a current location of said mobile unit based on;

(i) said detected phases of the at least three of said beacon signals, and (ii) said estimate of said initial position;

said processor including;

a memory for storing estimates of location of said mobile unit made by said APS receiver at first and second calibration times, and for storing phases and frequencies of said beacon signals received from a plurality of said transmitters at said first and second calibration times, and

software for determining phase and frequency drift of said beacon signals based on said stored estimates of location of said mobile unit and said stored phases and frequencies of said beacon signals.

13. The positioning system of claim 12, wherein said APS receiver comprises a global positioning system (GPS) receiver and wherein said processor includes:

a memory for storing GPS time indications extracted from GPS signals received by said GPS receiver at first and second calibration times, and for storing local time indications registered by a local clock within said mobile unit at said first and second calibration times, and

software for calibrating said local clock by comparing a difference between said local time indications to a difference between said GPS time indications.

14. The positioning system of claim 12, wherein said processor includes:

a memory for storing APS time indications extracted from said APS signals received by said APS receiver at first and second calibration times, and for storing local time indications registered by a local clock within said mobile unit at said first and second calibration times, and

software for calibrating said local clock by comparing difference between said local time indications to difference between said APS time indications.

15. The positioning system of claim 12, said beacon signal receiver including circuitry for acquiring position data specifying the positions of said multiplicity of transmitters;

said processor including software for performing a predefined position computation using said position data to generate a position value for said mobile unit which is consistent with said position data.

16. The positioning system of claim 12, wherein said beacon signal transmitted by each of said transmitters comprise FM radio station pilot signals having frequencies of approximately 19 kHz.

17. The positioning system of claim 12, wherein said APS receiver comprises a receiver selected from the set consisting of:

a global positioning system (GPS) receiver and a LORAN receiver.

18. The positioning system of claim 12, wherein said APS receiver comprises a receiver selected from the set consisting of:

an OMEGA receiver and a TRANSIT receiver.

19. The positioning system of claim 12, wherein said beacon signal receiver also receives local traffic information from one of said multiplicity of transmitters, said local traffic information being useable for navigation.

20. In a positioning system which makes use of:

(i) an uncoordinated beacon positioning subsystem (UBS), said subsystem including a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency, and

(ii) global positioning system (GPS) signals transmitted by a multiplicity of GPS satellites,

a method for determining location of a mobile unit, said method comprising the steps of;

receiving a plurality of said beacon signals and determining a UBS location of said mobile unit therefrom;

receiving a plurality of said GPS signals and determining a GPS location of said mobile unit therefrom; and

determining uncertainty of said GPS and UBS locations, and updating a current location of said mobile unit based on said UBS and GPS locations and said uncertainty thereof;

wherein the determining step includes determining the uncertainty of GPS location by measuring and evaluating at least one signal parameter associated with the GPS signals, and determining the uncertainty of UBS location by measuring and evaluating at least one signal parameter associated with the received beacon signals.

21. The method of claim 20 wherein said step of determining uncertainty includes the step of computing a dilution of precision associated with said plurality of received GPS signals.

22. The method of claim 21 wherein said step of determining uncertainty includes the step of computing a UBS dilution of precision associated with said plurality of beacon signals.

23. The method of claim 20 further including the step of assigning said APS location to said UBS location when uncertainty of said APS location is determined to be less than uncertainty of said UBS location.

24. The method of claim 23 further including the step of assigning said UBS location to said APS location when uncertainty of said UBS location is determined to be less than uncertainty of said APS location.

25. The method of claim 20 wherein said step of determining a UBS location includes the steps of:

receiving at least three of said beacon signals,

detecting the phases of at least three of said beacon signals at the location of said mobile unit, and

computing a change in UBS location based upon said detected phases.

26. The method of claim 20, further including receiving local traffic information from one of said multiplicity of transmitters, said local traffic information being useable for navigation.

27. The method of claim 20, wherein the determining step includes, when the determined uncertainty of the UBS location is less than the determined uncertainty of the APS location, updating the current position in a manner selected from the set consisting of (A) based solely on the UBS location, and (B) based on a weighted combination of the UBS and APS locations wherein the UBS location is weighted more heavily than the APS location.

28. In a positioning system which makes use of an uncoordinated beacon positioning subsystem and an absolute positioning subsystem (APS), said uncoordinated beacon positioning subsystem including a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency,

a method for determining location of a mobile unit comprising the steps of:

at a known location relative to the locations of said multiplicity of transmitters, receiving said beacon signals, determining the relative phases of said beacon signals, and broadcasting phase data representing said relative phases;

at said mobile unit, receiving said broadcast phase data and receiving at least three of said beacon signals, detecting the phases of said beacon signals received at said mobile unit, and computing a first estimated location of said mobile unit based on said broadcast values and said detected phases;

at said mobile unit, receiving APS signals generated at known locations within a coordinated system of said APS subsystem, and providing a second estimated location of said mobile unit using said received APS signals; and

evaluating positional uncertainty in said first and second estimated locations, and updating a current position of said mobile unit based on said first and second estimated locations of said mobile unit and said positional uncertainty;

wherein the evaluating step includes determining the uncertainty of the first estimated location by measuring and evaluating at least one signal parameter associated with the beacon signals, and determining the uncertainty of the second estimated location by measuring and evaluating at least one signal parameter associated with the received APS signals.

29. The method of claim 28, further including receiving local traffic information from one of said multiplicity of transmitters, said local traffic information being useable for navigation.

30. The method of claim 28, wherein the determining step includes, when the determined uncertainty of the first estimated location is less than the determined uncertainty of the second estimated location, updating the current position in a manner selected from the set consisting of (A) based solely on the first estimated location, and (B) based on a weighted combination of the first and second estimated locations wherein the first estimated location is weighted more heavily than the second estimated location.

31. A method of determining a mobile unit'"'"'s current location with respect to the positions of a multiplicity of transmitters that are positioned at known locations, wherein each transmitter transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency,

the steps of the method comprising:

receiving, at said mobile unit, at least three of said beacon signals, and detecting the phases of the at least three of said beacon signals received at said mobile unit;

receiving, at said mobile unit, signals provided by an absolute positioning system (APS), and estimating an initial position of said mobile unit using said APS signals received at said mobile unit; and

computing said current location of said mobile unit based on;

(i) said detected phases of the at least three of said beacon signals, and (ii) said estimate of said initial position;

said step of computing includes the steps of;

estimating location of said mobile unit based on APS signals received at said mobile unit at first and second calibration times, and storing phases and frequencies of ones of said beacon signals received from a plurality of said transmitters at said first and second calibration times, and

determining phase and frequency drift and drift rates of said beacon signals based on said stored estimates of location of said mobile unit and said stored phases and frequencies of said beacon signals.

32. The method of claim 31 wherein said absolute positioning system comprises the global positioning system (GPS), and wherein said step of computing includes the steps of:

storing GPS time indications extracted from GPS signals received at said mobile unit at first and second calibration times, and storing local time indications registered by a local clock within said mobile unit at said first and second calibration times, and

calibrating said local clock by comparing difference between said local time indications to difference between said GPS time indications.

33. The method of claim 31 further including the step of receiving, at said mobile unit, local traffic information useable for navigation.

34. In a positioning system which makes use of:

(A) an uncoordinated beacon positioning subsystem, said uncoordinated beacon positioning subsystem including a multiplicity of transmitters, at known fixed locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals having a frequency which is approximately equal to a predetermined target frequency, and

(B) a multiplicity of global positioning system (GPS) satellites, each of which transmits a GPS signal having a predefined phase relationship to the GPS signals transmitted by the other satellites, wherein each of said GPS signals includes information indicative of a position of the GPS satellite within a GPS coordinate system at the time of transmission of the GPS signal therefrom;

a method for determining location of a mobile unit comprising the steps of;

at said mobile unit,

(i) receiving at least three of said beacon signals and computing a first set of estimated ranges between a current position of said mobile unit within said predefined coordinate system and the three of said beacon signal transmitters from which were transmitted said at least three of said beacon signals;

(ii) receiving a plurality of said GPS signals and computing a second set of estimated ranges between a current position of said mobile unit within said GPS coordinate system and said GPS satellites from which were transmitted said plurality of GPS signals;

(iii) forming a set of simultaneous position equations based on said first and second sets of estimated ranges, said set of simultaneous position equations being referenced to said GPS coordinate system; and

(iv) solving said set of simultaneous equations in order to determine said current location of said mobile unit.

35. The method of claim 34 wherein said forming step includes forming said set of simultaneous position equations using four range estimates included within said first and second sets of estimated ranges, said set of simultaneous position equations being referenced to said GPS coordinate system and to a GPS time system.

36. A positioning system for determining location of a mobile unit, said system making use of a multiplicity of transmitters, at known locations, each of which transmits a beacon signal having a phase that is at least partially un-synchronized with the phases of the beacon signals of the other transmitters, each of said beacon signals being of a predetermined repetition rate, said system comprising:

an uncoordinated beacon positioning subsystem (UBS), said subsystem including a UBS receiver for receiving said beacon signals and for generating a UBS pseudorange residual signal;

an absolute positioning subsystem (APS) including an APS receiver for receiving APS signals and for generating an APS pseudorange residual signal, said APS receiving including a code loop detector that generates said APS pseudorange residual signal and a code loop oscillator in a feedback arrangement with said code loop detector; and

an estimator for filtering and combining said UBS pseudorange residual signal and said ABS pseudorange residual signal to generate a velocity signal used to control said code loop oscillator in said APS and to generate a change-in-position signal;

said feedback arrangement in said APS including apparatus for combining said change-in-position signal with a signal generated by said code loop oscillator to generate an a priori APS pseudorange signal that is feed back to said code loop detector.