GPS/IRS global position determination method and apparatus with integrity loss provisions
DCFirst Claim
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1. A combined inertial reference system and a satellite positioning system for determining user position comprising:
- an inertial reference system employing inertial sensors for providing IRS position and inertial reference information, including IRS velocity information, derived from output information from said inertial sensors;
a satellite positioning system receiver for providing a GPS position solution including a resultant GPS position and resultant GPS velocity information derived form satellite information from signals transmitted from a plurality of satellites;
validation means responsive to at least the number of said plurality of satellites transmitting said satellite information signals for indicating a non-availability time period when said number is below that which is required to provide at least one integrity limit value associated with the accuracy of said GPS solution, as opposed to an integrity time period when said number is sufficient to provide said at least one integrity limit value;
error estimator means for determining velocity and acceleration error estimates associated with said IRS inertial information as a function of said IRS velocity information and said resultant GPS velocity information;
coast position estimator means for determining a first estimated position of the user'"'"'s position during said non-availability time period as function of said velocity and acceleration error estimates occurring at the beginning of said non-availability time period, the elapsed time accumulated since the beginning of said non-availability time period, and the IRS position.
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Abstract
A system for use with an inertial reference system and a global position receiver for calculating a position error after a loss of integrity by utilizing the global position system values for position and velocity at a time just before the loss of integrity and by utilizing the inertial reference system position modified by the known error in inertial reference system position as it varies with time and the position error as calculated by the global position system velocity extrapolated over the time since integrity loss.
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Citations
19 Claims
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1. A combined inertial reference system and a satellite positioning system for determining user position comprising:
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an inertial reference system employing inertial sensors for providing IRS position and inertial reference information, including IRS velocity information, derived from output information from said inertial sensors; a satellite positioning system receiver for providing a GPS position solution including a resultant GPS position and resultant GPS velocity information derived form satellite information from signals transmitted from a plurality of satellites; validation means responsive to at least the number of said plurality of satellites transmitting said satellite information signals for indicating a non-availability time period when said number is below that which is required to provide at least one integrity limit value associated with the accuracy of said GPS solution, as opposed to an integrity time period when said number is sufficient to provide said at least one integrity limit value; error estimator means for determining velocity and acceleration error estimates associated with said IRS inertial information as a function of said IRS velocity information and said resultant GPS velocity information; coast position estimator means for determining a first estimated position of the user'"'"'s position during said non-availability time period as function of said velocity and acceleration error estimates occurring at the beginning of said non-availability time period, the elapsed time accumulated since the beginning of said non-availability time period, and the IRS position. - View Dependent Claims (2, 3, 4)
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5. An apparatus for determining the position of a vehicle, the apparatus comprising:
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a global positioning system (GPS) communicating with a plurality of satellites and providing a GPS position signal; an inertial reference system (IRS) providing an IRS position signal; a position estimator providing a hybrid position signal based upon th eGPS position signal and the IRS position signal; an IRS position estimator providing an estimated IRS position signal based upon the IRS position signal, the velocity of the vehicle, and the acceleration of the vehicle; and a position selector providing a vehicle position signal, wherein the vehicle position signal corresponds to the hybrid position signal when the GPS position signal is reliable, and wherein the vehicle position signal corresponds to the estimated IRS position signal when the GPS position signal is unreliable. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of determining the position of a vehicle having a velocity and an acceleration, the method comprising the steps of:
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providing a GPS position signal from a global positioning system; providing an IRS position signal from an inertial navigation system; determining if the GPS position signal is reliable; providing a hybrid position signal to a flight control when the GPS position signal is reliable, the hybrid position signal being based upon the GPS position signal and the IRS position signal; and providing an estimated IRS position signal to a flight control when the GPS position signal is unreliable, the estimated IRS position signal being based upon the velocity of the vehicle, the acceleration of the vehicle and the IRS position signal. - View Dependent Claims (16, 17, 18, 19)
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Specification