System and method for determining vehicle position

Abstract

An illustrative example embodiment of a system includes a detector configured to detect a signal from a source and provide first signal information about a distance traveled by the detected signal between the source and the detector. A processor is configured to determine whether the first signal information corresponds to a direct signal path between the detector and the source or the first signal information corresponds to a reflected signal based on second signal information from at least one other detector that does not have a direct signal path between the other detector and the source. The processor determines a position of the detector based on the first signal information only if the first signal information corresponds to a direct signal path between the detector and the source.

Description

Background Art

[0001] Modern motor vehicles include an increasing amount of electronic technology, such as, for example, navigation systems that can be used for route guidance or autonomous vehicle control. Many navigation systems operate based on detecting satellite signals and using known algorithms to determine the current vehicle position. The accuracy of the system depends on the quality of the satellite signals received and processed. There are situations where satellite signals may not be completely reliable.

[0002] For example, a satellite signal may reflect off a nearby structure before being received by a navigation system antenna or detector. Such reflections increase the distance the signal travels before reaching the antenna or detector compared to a signal that travels directly from the satellite to the antenna or detector. Since the known position of the satellite from which such a signal originates is used to determine the position of the vehicle, any intermediate reflections and the resulting increased signal travel distance may introduce errors in the vehicle position determination. Summary of the invention

[0003] An illustrative example embodiment of a system includes a detector configured to detect a signal from a source and provide first signal information about a distance traveled by the detected signal between the source and the detector. A processor is configured to determine whether the first signal information corresponds to a direct signal path between the detector and the source or the first signal information corresponds to a reflected signal based on second signal information from at least one other detector that does not have a direct signal path between the other detector and the source. The processor determines a position of the detector based on the first signal information only if the first signal information corresponds to a direct signal path between the detector and the source.

[0004] In an example embodiment including at least one of the features of the system of the preceding paragraph, the first signal information includes a pseudorange between at least one source and at least one detector, and the second signal information includes a distance traveled by a reflected signal between at least one source and at least one other detector.

[0005] In an example embodiment including at least one of the features of the system of any of the preceding paragraphs, the processor is configured to determine that the first signal information corresponds to a reflected signal by determining a difference between a pseudorange of the first signal information and a distance of the second signal information, and determining that the determined difference is below a threshold.

[0006] In an example embodiment including at least one of the features of the system of any preceding paragraph, the processor is configured to determine that the first signal information corresponds to a reflected signal by determining that a pseudorange of the first signal information is greater than a distance of the second signal information.

[0007] In an example embodiment including at least one of the features of the system of any preceding paragraph, the at least one detector is associated with a vehicle and the determined position is the position of the vehicle.

[0008] In an example embodiment of at least one of the features of the system of any of the preceding paragraphs, the processor is configured to determine whether the second signal information corresponds to a reflected signal between at least one source and at least one other detector by: determining a position of the at least one other detector relative to the vehicle; determining a position of the vehicle relative to at least one source; and based on the determined respective positions, determining that at least a portion of the vehicle obstructs a direct signal path between the at least one source and the at least one other detector.

[0009] In an example embodiment including at least one of the features of the system of any of the preceding paragraphs, at least a portion of the vehicle includes a roof of the vehicle, and the processor uses information about at least one of a size of the roof and a shape of the roof to determine that the roof obstructs a direct signal path between at least one source and at least one other detector.

[0010] An example embodiment of at least one of the features of the system of any of the preceding paragraphs includes at least one other detector, and wherein the at least one other detector is located in a known position relative to a portion of a vehicle, wherein the portion of the vehicle obstructs a direct signal path between the at least one other detector and the at least one source.

[0011] In an example embodiment including at least one of the features of the system of any preceding paragraph, at least one source is a satellite having a known position within an Earth-centered, Earth-fixed reference frame.

[0012] An illustrative example embodiment of a method includes: detecting a signal from at least one source; generating first signal information about a distance traveled by the detected signal between the at least one source and at least one detector; and determining, based on second signal information from at least one other detector, whether the first signal information corresponds to a direct signal path between the at least one detector and the at least one source, or whether the first signal information corresponds to a reflected signal, the at least one other detector not having a direct signal path between the at least one other detector and the at least one source; and determining a position of the at least one detector based on the first signal information when the first signal information corresponds to a direct signal path between the at least one detector and the at least one source.

[0013] In an example embodiment including at least one of the features of the method of the preceding paragraph, the first signal information includes a pseudorange between at least one source and at least one detector, and the second signal information includes a distance traveled by a reflected signal between at least one source and at least one other detector.

[0014] An example embodiment including at least one of the features of the method of any preceding paragraph comprises determining that the first signal information corresponds to a reflected signal by determining a difference between a pseudorange of the first signal information and a distance of the second signal information, and determining that the determined difference is below a threshold.

[0015] An example embodiment including at least one of the features of the method of any preceding paragraph comprises determining that the first signal information corresponds to a reflected signal by determining that a pseudorange of the first signal information is greater than a distance of the second signal information.

[0016] In an example embodiment including at least one of the features of the method of any preceding paragraph, at least one detector is associated with the vehicle and the method includes determining the position of the vehicle based on the determined position of the at least one detector.

[0017] An example embodiment of at least one of the features of the method of any of the preceding paragraphs includes determining whether the second signal information corresponds to a reflected signal between at least one source and at least one other detector by: determining a position of the at least one other detector relative to the vehicle; determining a position of the vehicle relative to at least one source; and based on the determined respective positions, determining that at least a portion of the vehicle obstructs a direct signal path between the at least one source and at least one other detector.

[0018] In an example embodiment including at least one of the features of the method of any of the preceding paragraphs, at least a portion of the vehicle includes a vehicle roof, and the method includes: using information about at least one of a size of the roof and a shape of the roof to determine that the roof obstructs a direct signal path between at least one source and at least one other detector.

[0019] In an example embodiment including at least one of the features of the method of any preceding paragraph, at least one other detector is located in a known position relative to a portion of the vehicle, wherein the portion of the vehicle obstructs a direct signal path between the at least one other detector and the at least one source.

[0020] In an example embodiment including at least one of the features of the method of any preceding paragraph, at least one source is a satellite having a known position within an Earth-centered, Earth-fixed reference frame.

[0021] An illustrative example embodiment of a vehicle navigation system includes: a detection device for detecting a signal from at least one source and providing first signal information about a distance traveled by the detected signal between the at least one source and at least one detector; and a device for: determining, based on second signal information from at least one other detector, whether the first signal information corresponds to a direct signal path between the at least one detector and the at least one source, or whether the first signal information corresponds to a reflected signal, the at least one other detector not having a direct signal path between the at least one other detector and the at least one source, and determining a position of the vehicle based on the first signal information when the first signal information corresponds to a direct signal path between the at least one detector and the at least one source.

[0022] In an example embodiment of at least one of the features of the system of the preceding paragraphs, at least one source is a satellite having a known position relative to an Earth-centered, Earth-fixed reference system, the first signal information includes a pseudorange between the satellite and at least one detector, and the second signal information includes a distance traveled by a reflected signal between the at least one source and at least one other detector.

[0023] The numerous features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description.The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An example embodiment of a system for determining a position of a vehicle is schematically illustrated.

[0025] Figure 2 is a flow chart outlining an example embodiment of a method of determining a location.

[0026] Figure 3 is a flow chart outlining an example method for determining when a direct signal path is available between a source and a detector. DETAILED DESCRIPTION

[0027] Figure 1 The system 20 is schematically shown to include a detector 22 and a processor 24. The detector 22 includes an antenna or another device capable of detecting a signal from at least one source. Figure 1 In the illustrated embodiment, the detector 22 is configured to detect a satellite signal from a satellite 26. For discussion purposes, only one satellite is shown, but the detector 22 will often detect multiple satellites. The detector 22 is configured to generate first signal information about the distance traveled by the detected signal between the satellite 26 and the detector 22.

[0028] The processor 24 includes a computing device and associated memory. In some embodiments, the processor 24 is a device dedicated to processing signals from the detector 22, while in other embodiments, the processor 24 is a device that performs other functions that may be unrelated to processing signals from the detector 22. The processor 24 is configured to determine whether the first signal information from the detector 22 corresponds to a direct signal path between the detector 22 and the satellite 26, or whether the first signal information corresponds to a reflected signal. The processor 24 makes this determination based on second signal information from at least one other detector 208, which provides the second signal information. When the detector 28 does not have a direct signal path between it and the satellite 26, any second signal information from the detector 28 related to the signal detected from the satellite 26 is the result of the reflected signal detected by the detector 28.

[0029] exist Figure 1 In the illustrated embodiment, system 20 is associated with vehicle 30 and is useful for determining the location of vehicle 30. Detector 28 is located within vehicle 30 such that one or more portions of vehicle 30 obstruct a direct signal path between detector 28 and satellite 26 in at least some circumstances.

[0030] Figure 1 The illustrated situation includes a direct signal path 32 from the satellite 26 to the detector 22. First signal information from the detector 22 resulting from detecting a signal traveling along the direct signal path 32 is useful for determining the position of the detector 22 and the vehicle 30 because the satellite 26 has a known position relative to an Earth-centered, Earth-fixed (ECEF) reference frame.

[0031] exist Figure 1 In the case shown, it is also possible that the detector 22 detects a signal from the satellite 26 that is a reflected signal that should not be used to make a position determination because the distance traveled by the reflected signal would introduce errors into the position determination that is based in part on the known position of the satellite 26. For example, the signal from the satellite 26 may travel along a path shown at 34 and reflect off a structure 36, such as a building near the path of the vehicle 30. The reflected signal may follow a path as schematically shown at 38 and be detected by the detector 22. The distance traveled by the signal along the paths 34, 38 is different than the distance traveled by the signal along the direct signal path 32 between the satellite 26 and the detector 22. The processor 24 utilizes the first signal information from the detector corresponding to the signal along the direct signal path 32, but does not use the first signal information from the detector 22 derived from the reflected signal detected by the detector 22.

[0032] The processor 24 uses second signal information from at least one other detector, such as a detector 28 located in the vehicle 30, to determine whether the first signal information corresponds to a reflected signal. Given the current position of the satellite 26 and the position of the vehicle 30 relative to the satellite 26, there is no direct signal path between the satellite 26 and the detector 28. Potential direct signal path 40 is blocked by the top 42 of the vehicle 30. The position of the detector 28 in the vehicle 30 allows the detector 28 to detect the reflected signal from the satellite 26. For example, a signal along the path schematically shown at 34, reflected off the structure 36 and then along the path schematically shown at 44 can pass through the windshield of the vehicle 30 and be detected by the detector 28. The processor 24 receives second signal information from the detector 28 indicating or corresponding to the distance traveled by the reflected signal along the path 34, 44. The processor 24 uses such second signal information to determine whether the first signal information from the detector 22 should be used to determine the position of the detector 22 and the vehicle 30.

[0033] Figure 2 A flow chart 50 is included that summarizes an example method of determining a position. At 52, the detector 22 detects a signal from a satellite 26. At 54, the detector 22 generates first signal information about the distance traveled by the detected signal between the satellite 26 and the detector 22. In this example embodiment, the first signal information includes a pseudorange corresponding to the distance traveled by the signal. The first signal information is provided to the processor 24. At 56, the processor 24 determines whether the first signal information corresponds to a direct signal path distance or a reflection distance based on the second signal information from the detector 28, in this example, the second signal information is another pseudorange. The processor 24 determines the difference between the distance of the first signal information and the distance of the second signal information. The processor 24 determines whether the difference between the distance of the first signal information and the distance of the second signal information is below a threshold or within a preselected range. When it is known that the second signal information corresponds to a reflected signal and the distance of the first signal information is sufficiently close to the distance of the reflected signal, the processor 24 determines that the first signal information is the result of the detector 22 detecting the reflected signal rather than a signal along the direct signal path between the satellite 26 and the detector 22.

[0034] For example, when the location of interest is the location of the vehicle 30, it may be assumed that any nearby structure 36 from which the satellite signal may reflect, resulting in the reflected signal, is at least 1.5 meters away from the vehicle 30. The reflected signal may travel through such a spacing twice, resulting in the reflected signal traveling a distance that differs by about three meters from a direct signal path that does not involve reflection off of the nearby structure 36. In this example, whenever the difference between the distance of the first signal information and the distance of the second signal information is within three meters, the processor 24 determines that the pseudorange or distance of the first signal information is the result of the reflected signal because the second signal information is known to be the result of detecting the reflected signal.

[0035] At 58, when the first signal information corresponds to detection of a signal received along a direct signal path, the processor 24 determines the location of the detector 22 or the vehicle 30 based on the first signal information. In some embodiments, any signal that appears to be a reflected signal is rejected or excluded from the information used to determine the location of the vehicle 30, but some embodiments include using such signal information when the processor 24 is able to make sufficiently reliable corrections or adjustments.

[0036] In some embodiments, detector 28 is part of system 20 and is located in a known position on vehicle 30 where it may only be able to detect reflected signals from satellite 26. For example, detector 28 may be located relative to the interior of vehicle 30 where it would be effectively shielded by the top of vehicle 42 from any direct signal path from satellite 26 or other satellites that may be used for position determination. In such embodiments, it is always known that the second signal information from detector 28 corresponds to the reflected signal.

[0037] In other embodiments, detector 28 may be located on vehicle 30 at a location that may obstruct a direct satellite signal path depending on the relative positions of vehicle 30 and satellites 26. For example, there may be a situation where detector 28 has a direct line of sight through the windshield of vehicle 30 to one or more satellites, depending on the relative positions of those satellites to vehicle 30.

[0038] Figure 3A flowchart 60 is included that outlines an example technique for the processor 24 to determine whether the second signal information from the detector 28 corresponds to a reflected signal. At 62, the processor 24 determines the position of the detector 28 relative to the vehicle. Depending on the embodiment, this can be implemented in different ways known to those skilled in the art. When the detector 28 is at a dedicated location on or in the vehicle 30, the position of the detector 28 is known. In other embodiments, such as when the detector 28 is a personal communication device (such as a cell phone) with GPS capabilities, the detector 28 is movable relative to the vehicle 30. In such an embodiment, the processor 24 uses known positioning techniques to locate the position of the detector 28 relative to the vehicle 30. In an example, the position of the movable detector relative to the vehicle is determined using a radio frequency transmission from the detector, which is received by multiple antennas distributed around the vehicle. In this example, the multiple antennas can be components of a passive entry / passive start (PEPS) system that can be installed on the vehicle. Details for determining the position of the movable detector are disclosed in U.S. Patent Application No. 16 / 275,374, the entire contents of which are incorporated herein by reference.

[0039] At 64, the processor 24 determines the position of the vehicle 30 relative to the satellite 26. This may be accomplished, for example, by using the last known position or fix of the vehicle 30 and the current known position of the satellite 26, which may be obtained via a known GNSS almanac accessed by the processor 24. Based on this relationship and the position of the detector 28 relative to the vehicle 30, the processor 24 is able to determine if a portion of the vehicle 30 is obstructing a direct signal path between the satellite 26 and the detector 28, which provides the second signal information.

[0040] In some embodiments, processor 24 is provided with information about the size, shape, or both of vehicle roof 42 and uses this information in conjunction with the relative positions of vehicle 30 and satellite 26 to determine when roof 42 will obstruct a direct signal path between detector 28 and satellite 26 .

[0041] The illustrated example embodiments provide enhanced accuracy for position determination, such as locating a vehicle. Accurate vehicle position is useful for guided navigation or autonomous vehicle control. By eliminating reflected signals from the position determination, the example system improves the accuracy and reliability of the position determination, thereby allowing tighter error bound requirements to be met.

[0042] The various features of the disclosed embodiments are not necessarily limited to the arrangements shown. Other combinations of disclosed features are possible to implement additional or different embodiments.

[0043] The foregoing description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of the invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

Claims

1. A system comprising: at least one detector configured to detect a signal from at least one source and provide first signal information regarding a distance traveled by the detected signal between the at least one source and the at least one detector, wherein the at least one detector is associated with a vehicle; as well as A processor configured to determining whether the first signal information corresponds to a reflected signal or a direct signal path between the at least one detector and the at least one source by determining whether the first signal information indicates a distance or pseudorange that is greater than a distance or pseudorange indicated by second signal information from at least one other detector, wherein the at least one other detector is configured to be located at a different position relative to the vehicle than the at least one detector and the at least one other detector is determined to have no direct signal path between the at least one other detector and the at least one source, and When the first signal information corresponds to the direct signal path between the at least one detector and the at least one source, determining the position of the at least one detector based on the first signal information The processor is further configured to determine that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source by: determining a position of the at least one other detector relative to the vehicle; determining a position of the vehicle relative to the at least one source; Based on the determined respective positions, it is determined that at least a portion of the vehicle obstructs a direct signal path between the at least one source and the at least one other detector; and when the at least a portion of the vehicle obstructs the direct signal path, it is determined that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source, and the second signal information corresponds to a reflected signal between the at least one source and the at least one other detector.

2. The system according to claim 1, characterized in that The pseudorange indicated by the first signal information comprises a pseudorange between the at least one source and the at least one detector; and The distance indicated by the second signal information comprises a distance travelled by a reflected signal between the at least one source and the at least one other detector.

3. The system according to claim 2, characterized in that The processor is configured to determine that the first signal information corresponds to a reflection signal by: determining a difference between the pseudorange of the first signal information and the range of the second signal information, and It is determined that the determined difference is below a threshold value.

4. The system according to claim 2, characterized in that The processor is configured to determine that the first signal information corresponds to a reflected signal by determining that the pseudorange of the first signal information is greater than the distance of the second signal information.

5. The system according to claim 1, wherein: The determined position is the position of the vehicle.

6. The system according to claim 1, characterized in that: The at least a portion of the vehicle includes a roof of the vehicle; and The processor uses information about at least one of a size of the top and a shape of the top to determine that the top obstructs the direct signal path between the at least one source and the at least one other detector.

7. The system according to claim 5, characterized in that The at least one other detector is included, and wherein the at least one other detector is located in a known position relative to a portion of the vehicle, wherein the portion of the vehicle obstructs a direct signal path between the at least one other detector and the at least one source.

8. The system of claim 1, wherein: The at least one source is a satellite having a known position in an Earth-centered, Earth-fixed reference frame.

9. A method comprising: detecting a signal from at least one source; generating first signal information regarding a distance traveled by a detected signal between the at least one source and the at least one detector, wherein the at least one detector is associated with a vehicle; as well as determining whether the first signal information corresponds to a reflected signal or a direct signal path between the at least one detector and the at least one source by determining whether the first signal information indicates a greater distance or pseudorange than a distance or pseudorange indicated by second signal information from at least one other detector; as well as determining a position of the at least one detector based on the first signal information when the first signal information corresponds to the direct signal path between the at least one detector and the at least one source, wherein the at least one other detector is configured to be located at a different position relative to the vehicle than the at least one detector and the at least one other detector is determined to have no direct signal path between the at least one other detector and the at least one source, The method further includes determining that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source by: determining a position of the at least one other detector relative to the vehicle; determining a position of the vehicle relative to the at least one source; determining, based on the determined respective positions, that at least a portion of the vehicle obstructs a direct signal path between the at least one source and the at least one other detector; and When at least a portion of the vehicle obstructs the direct signal path, it is determined that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source, and the second signal information corresponds to a reflected signal between the at least one source and the at least one other detector.

10. The method according to claim 9, It is characterized by: The pseudorange indicated by the first signal information comprises a pseudorange between the at least one source and the at least one detector; and The distance indicated by the second signal information comprises a distance travelled by a reflected signal between the at least one source and the at least one other detector.

11. The method according to claim 10, characterized in that The method comprises determining that the first signal information corresponds to a reflected signal by performing the following operations: determining a difference between the pseudorange of the first signal information and the range of the second signal information, and It is determined that the determined difference is below a threshold value.

12. The method according to claim 10, characterized in that The method includes determining that the first signal information corresponds to a reflected signal by: determining that the pseudorange of the first signal information is greater than the distance of the second signal information.

13. The method according to claim 9, characterized in that Also included is determining a position of the vehicle based on the determined position of the at least one detector.

14. The method according to claim 9, characterized in that The at least a portion of the vehicle includes a vehicle roof, and the method includes using information about at least one of a size of the roof and a shape of the roof to determine that the roof obstructs the direct signal path between the at least one source and the at least one other detector.

15. The method according to claim 13, characterized in that The at least one other detector is located in a known position relative to a portion of the vehicle, wherein the portion of the vehicle obstructs a direct signal path between the at least one other detector and the at least one source.

16. The method according to claim 9, characterized in that The at least one source is a satellite having a known position in an Earth-centered, Earth-fixed reference frame.

17. A vehicle navigation system comprising: detection means for detecting a signal from at least one source and providing first signal information regarding a distance travelled by the detected signal between said at least one source and said at least one detector; as well as Devices for: determining whether the first signal information corresponds to a reflected signal or a direct signal path between the at least one detector and the at least one source by determining whether the first signal information indicates a greater distance or pseudorange than a distance or pseudorange indicated by second signal information from at least one other detector, and determining the position of the vehicle based on the first signal information when the first signal information corresponds to the direct signal path between the at least one detector and the at least one source, wherein the at least one other detector is configured to be located at a different position relative to the vehicle than the at least one detector and the at least one other detector is determined to have no direct signal path between the at least one other detector and the at least one source, The vehicle navigation system also includes means for determining that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source by: determining a position of the at least one other detector relative to the vehicle; determining a position of the vehicle relative to the at least one source; determining, based on the determined respective positions, that at least a portion of the vehicle obstructs a direct signal path between the at least one source and the at least one other detector; and When at least a portion of the vehicle obstructs the direct signal path, it is determined that the at least one other detector does not have a direct signal path between the at least one other detector and the at least one source, and the second signal information corresponds to a reflected signal between the at least one source and the at least one other detector.

18. The vehicle navigation system of claim 17, wherein The at least one source is a satellite having a known position relative to an Earth-centered Earth-fixed reference system; The pseudorange indicated by the first signal information includes a pseudorange between the satellite and the at least one detector; The distance indicated by the second signal information comprises a distance travelled by a reflected signal between the at least one source and the at least one other detector.

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