Passive navigation system
First Claim
1. An apparatus for navigating a vehicle, of the type having a gravity sensor, a gravity gradiometer, gravity reference map memory storing geographic gravity data, a vehicle position and velocity sensor, and an optimum filter which utilizes data supplied to provide a state vector, the components of which are used to update navigational data comprising:
- an integrator, coupled to said vehicle position and velocity sensor and to said gravity gradiometer, to provide signals representative of an integration, over a selected time interval, of a product of gravity gradient and vehicle velocity, thereby providing output signals representative of a gravity vector having a gravity north component, a gravity east component, and a gravity down component;
a gravity vertical deflection map memory, storing geographic gravity vertical deflection data;
a complementary filter, coupled said gravity vertical deflection memory and to said integrator, to provide signals representative of gravity vertical deflection estimates;
a first comparator coupled to said complementary filter, to said gravity vertical deflection map memory, and to said optimum filter to provide signals representative of differences between gravity vertical deflection read from said gravity vertical deflection map memory and gravity vertical deflection established by said complementary filter; and
a correction processor coupled to said optimum filter for updating position, velocity, and attitude of said vehicle.
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Accused Products
Abstract
A Passive Navigation System (PNS) provides continuous updating of position, velocity, and attitude information of a vehicle without recourse to radiating or external navigation aids. The system accurately computes navigation information with the utilization of gravity sensors, gravimetric maps, vertical position, and velocity measurements. Sensor and map data are optimally processed by real time filtering to compute the best position, velocity, and attitude of the vehicle. The products of measured gravity gradients and the velocity of the vehicle are integrated over time to obtain a north, east, down gravity vector components which are combined with corresponding components obtained from a vertical deflection map in a complementary filter. North and east components of the combination are compared with the corresponding components from the vertical deflection map, while the down component of the gravity is compared to the down value obtained from a gravimeter. Residuals from these comparisons are utilized in a Kalman filter to provide corrections that render inertial measuring units in the system independent of the vertical deflections and gravity anomalies. Measured gravity gradients are compared to reference map gradients, the residuals being utilized in the kalman filter to estimate long term position errors and to provide correction for gradiometer bias and drift. A vertical position loop mixes gravity down data obtained from a gravimeter and gravity down data obtained from the integrator to provide vertical position which is compared to a reference derived from the difference between a measured vehicle height and terrain height obtained from a geoidal map. The residual of this comparison is utilized in the Kalman filter to improve estimates of east velocity.
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Citations
17 Claims
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1. An apparatus for navigating a vehicle, of the type having a gravity sensor, a gravity gradiometer, gravity reference map memory storing geographic gravity data, a vehicle position and velocity sensor, and an optimum filter which utilizes data supplied to provide a state vector, the components of which are used to update navigational data comprising:
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an integrator, coupled to said vehicle position and velocity sensor and to said gravity gradiometer, to provide signals representative of an integration, over a selected time interval, of a product of gravity gradient and vehicle velocity, thereby providing output signals representative of a gravity vector having a gravity north component, a gravity east component, and a gravity down component; a gravity vertical deflection map memory, storing geographic gravity vertical deflection data; a complementary filter, coupled said gravity vertical deflection memory and to said integrator, to provide signals representative of gravity vertical deflection estimates; a first comparator coupled to said complementary filter, to said gravity vertical deflection map memory, and to said optimum filter to provide signals representative of differences between gravity vertical deflection read from said gravity vertical deflection map memory and gravity vertical deflection established by said complementary filter; and a correction processor coupled to said optimum filter for updating position, velocity, and attitude of said vehicle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for navigating a vehicle, the apparatus being of the type having gravity gradiometer for determining gravity gradients, gravity reference map memory which stores geographic gravity data, and a optimum filter which utilizes data supplied to provide a state vector, the components of which are used to update navigation data
wherein said gravity gradiometer provides a measured gravity gradient matrix and said gravity reference map memory provides a reference gravity gradient matrix; - and further comprising;
a first comparator coupled to said gravity gradiometer, said gravity reference map memory, and said optimum filter for providing signals respectively representative of differences between corresponding components of said measured gravity matrix and said reference gravity gradient matrix from which signals representative of long term position errors and signals for correcting gradiometer bias and drift are determined. - View Dependent Claims (10, 11)
- and further comprising;
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12. A method of vehicle navigation comprising the steps of:
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providing a gravity gradiometer to measure gravity gradients; storing geographic gravity data in a gravity reference map memory; establishing an optimum filter to provide a state vector, the components of which are utilized to update sensors of the navigation system; utilizing said gravity gradiometer and said gravity reference map memory to establish a gravity gradient matrix and a reference gravity gradient matrix, respectively; determining differences between respective components of said gravity gradient matrix and said reference gravity gradient matrix, thereby establishing gravity gradient component differences; coupling said gravity gradient matrix component differences to said filter for utilization in said state vector to determine long term position errors and to provided correction data for gradiometer bias and drift. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification