Method for rapid recovery from dead reckoning system heading loss
First Claim
1. A method of recovering a heading of a vehicle having a navigation system installed thereon, the navigation system including a Global Positioning System (GPS) receiver and a dead reckoning system whereby the dead reckoning system includes a heading rate sensor, the method comprising the steps of:
- determining heading change information from the navigation system;
running anomaly detection tests to determine if a current heading from the dead reckoning system is in error;
incrementing a heading uncertainty in response to positive anomaly detection test results;
determining whether the heading uncertainty is excessive;
if the heading uncertainty is excessive, determining a recovered heading in response to information from both the GPS receiver and the dead reckoning system and when the GPS receiver is unable to determine a reliable heading;
determining if a difference between the current heading and the recovered heading is excessive;
resetting the current heading and the heading uncertainty if the difference is excessive; and
resetting a position of the vehicle in response to the reset current heading.
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Accused Products
Abstract
A method of recovering the heading of a terrestrial vehicle navigation system having a GPS receiver integrated with a dead reckoning system. After determining that a current estimate of the heading may be in error (12, 14), Doppler measurement double difference observables are computed for all GPS satellites whose L band carriers are in phase or frequency track, available distance traveled and heading change information is extracted, and the results are combined and processed (20) to produce a new current heading estimate. A recursive estimator is used to guarantee convergence to an accurate result. Conventional GPS/dead reckoning combined systems generally reset to the first available GPS position following a heading loss. Gross positioning errors can accumulate up to this point, however. The methods described can recover the dead reckoning system heading by processing Doppler information from a single GPS satellite, and thus reduce position error growth occurring when the heading is unknown.
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Citations
25 Claims
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1. A method of recovering a heading of a vehicle having a navigation system installed thereon, the navigation system including a Global Positioning System (GPS) receiver and a dead reckoning system whereby the dead reckoning system includes a heading rate sensor, the method comprising the steps of:
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determining heading change information from the navigation system; running anomaly detection tests to determine if a current heading from the dead reckoning system is in error; incrementing a heading uncertainty in response to positive anomaly detection test results; determining whether the heading uncertainty is excessive; if the heading uncertainty is excessive, determining a recovered heading in response to information from both the GPS receiver and the dead reckoning system and when the GPS receiver is unable to determine a reliable heading;
determining if a difference between the current heading and the recovered heading is excessive;resetting the current heading and the heading uncertainty if the difference is excessive; and resetting a position of the vehicle in response to the reset current heading. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of recovering the heading of a terrestrial vehicle navigation system comprising a GPS receiver integrated with a dead reckoning system, the method comprising the steps of:
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determining that a current estimate of the heading may be in error by a predetermined excessive amount; if the current estimate is in error by the predetermined excessive amount, computing Doppler measurement double difference observables derived by the GPS receiver when the GPS receiver is unable to determine a reliable heading; extracting distance traveled and heading change information from heading sensors of the dead reckoning system; combining the Doppler measurement double difference observables with the distance traveled and the heading change information to produce a new current estimate of the heading; using a recursive estimator to process the new current estimate of the heading with the heading change information to guarantee convergence to an accurate estimate of the heading; comparing the accurate estimate of the heading with the current estimate of the heading; and resetting the current estimate of the heading if a difference between the accurate estimate and the current estimate is excessive. - View Dependent Claims (10)
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11. A method of recovering a heading for a vehicle with a terrestrial navigation system comprising a GPS receiver integrated with wheel sensors providing pulse count information, the method comprising the steps of:
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determining that a current estimate of the heading may be in error by a predetermined excessive amount; if the current estimate is in error by the predetermined excessive amount, computing Doppler measurement double difference observables derived by the GPS receiver when the GPS receiver is unable to determine a reliable heading; extracting distance traveled and heading change information from the pulse count information; combining the Doppler measurement double difference observables with the distance traveled and the heading change information to produce a new current estimate of the heading; using a recursive estimator to process the new current estimate of the heading with the heading change information to guarantee convergence to an accurate estimate of the heading; comparing the accurate heading estimate with the current heading estimate; and resetting the current heading estimate if a difference between the accurate estimate and the current heading estimate is excessive. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method of recovering the heading of a terrestrial vehicle navigation system comprising a GPS receiver integrated with a transmission odometer and a heading rate sensor, the method comprising the steps of:
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determining that a current estimate of said heading may be in error by a predetermined excessive amount; if the current estimate is in error by the predetermined excessive amount, computing Doppler measurement double difference observables derived by the GPS receiver when the GPS receiver is unable to determine a reliable heading; extracting distance traveled information from the transmission odometer and heading change information from the heading rate sensor; combining said satellite Doppler measurement double difference observables with the distance traveled information and the heading change information to estimate a new current estimate of the heading; using a recursive estimator to process the new estimate of the heading with the heading change information to guarantee convergence to an accurate estimate of the heading; comparing the accurate estimate of the heading estimate with the current heading estimate; and resetting the current heading estimate if a difference between the accurate estimate and the current heading estimate is excessive. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification