Litton Systems, Inc.

Northrop Grumman Systems Corporation

Northrop Grumman Guidance and Electronics Company, Inc.

Northrop Grumman Corporation

James R Huddle

Daniel A Tazartes

Charles H Volk

Maureen Lipman, Legal Representative

Jerome S Lipman

Victor K Chueh

Emery L Moore

Hal W Banbrook

Jerome S Di Lipman

Suzanne J Northrop Grumman Corporation Heeg

Methods and apparatus for: (a) the correction of one or more elements determined from a first set of continuous gyro and accelerometer measurements comprising using a second set of discontinuously measured higher accuracy accelerometer measurements doubly integrated in an inertial coordinate system, (b) determining relative movement of a vehicle using a first set of acceleration measurements that do not include components of acceleration caused by the Earth's gravitational field, and a second set of acceleration measurements that do include components of acceleration caused by the Earth's gravitational field; and (c) correcting errors in an inertial navigation system positioned in a vehicle comprising using independently measured changes in position of the vehicle relative to an inertial coordinate frame.

Inertial navigation system error correction

An exemplary navigation system uses a master navigation component at a first location in a vehicle and a slave navigation component at a second location that is a variable displacement to the first location due to physical deformation of the vehicle. Static and dynamic location components provide static and dynamic information of the displacement between the first and second locations. An error estimator estimates errors in the navigational measurement data generated by the slave navigation component based on the navigational measurement data generated by the master navigation component and the displacement information provided by the static and dynamic location components. The master navigation component corrects the navigation measurement data of the slave navigation component based on the determined error and translates the corrected navigation measurement data of the slave navigation component into navigational measurement data in its coordinate system.

System for multiple navigation components

An exemplary navigation system uses a master navigation component at a first location with a first sensor in a vehicle and a slave navigation component with a second sensor at a second location that is a variable displacement to the first location due to physical deformation of the vehicle. Static and dynamic location components provide static and dynamic information of the displacement between the first and second locations. A flexural model based on the deformation characteristics calculates the dynamic displacement. An error estimator estimates errors in the navigation measurement data of the slave navigation component based on the displacement information. The master navigational component corrects the navigation measurement data of the slave navigation component based on the determined error, translates the corrected navigation measurement data of the slave navigation component into navigation measurement data in its coordinate system, and combines the output of the second sensor based on the corrected navigation measurement data with the output of the first sensor into a combined result.

System for interferometric sensing

Navigation systems provide accurate position, velocity and attitude information at one or more slave inertial measurement units (SIMU), mounted and spaced apart from a master inertial navigation system (MINS).

Transfer alignment of navigation systems

Embodiments of the system provide for processing non-continuous atom interferometer inertial instrument measurements and continuous wide bandwidth instrument measurements with a gravity database. An embodiment may have: a gravity disturbance vector database having gradients; a comparator that compares real-time gravity gradiometer gradient measurements with gradients from the database to provide an observation; and a Kalman filter that receives the observation on an input thereof, the Kalman filter outputting a modeled error state vector; wherein the gravity disturbance vector from the gravity database is used to remove a known portion of an actual gravity disturbance vector from specific force measurements of high bandwidth conventional inertial accelerometers to thereby form navigation data. An embodiment of the method that may have the steps of: providing a gravity disturbance vector database having stored gradients; providing real-time measurements of gravity gradients; and processing the stored gradients and the gravity gradients to form navigational data.

Method for the processing of non-continuous atom interferometer intertial instrument measurements and continuous wide bandwidth instrument measurements with a gravity database

The invention is a method and apparatus for generating navigation data. The method comprises the steps of (a) determining the position vector for one or more observation points in an earth-fixed reference frame and (b) determining either (1) the position vector for a target point in the earth-fixed reference frame from directions in either a model-based or a gravity-based reference frame from the one or more observation points to the target point or (2) the directions in either a model-based or a gravity-based reference frame from the one or more observation points to the target point from the position vector for the target point in the earth-fixed reference frame, the model-based reference frame having a vertical axis with a specified orientation with respect to a normal to an ellipsoidal model of the earth and having horizontal axes with specified orientations with respect to the earth-fixed reference, the gravity-based reference frame having a vertical axis with a specified orientation with respect to the gravity vector and having horizontal axes with specified orientations with respect to the earth-fixed reference frame. The apparatus for practicing the method for generating navigation data comprises an inertial navigation system, a GPS antenna and receiver, and direction-finding apparatus.

Method and apparatus for generating navigation data

A system, which uses inertial measurement units, is shown for determining the position and orientation of a towed array of sensors used for target detection. The system uses an onboard master inertial navigation system and a relative position determination mechanism to generate a first estimated position for each inertial measurement unit within the array. Each inertial measurement unit measures force and angular change information used by an onboard computer to create a second estimated position by known methods for each inertial sensor. An error signal represented by the difference between the two estimated positions for each inertial unit is processed over time by a Kalman filter to reduce the error in the heading and attitude determined for each inertial unit to establish an accurate location for each inertial unit and, thus, the towed array of such units.

Sensor array dynamic position and orientation determination system

The invention is a method and apparatus for determining the errors in the orientation coordinates of an antenna array and the spacings of the antennas in the array using radio waves from one or more sources having known positions and an inertial system, the antenna array comprising at least two antennas. The method comprises the steps of placing the antenna array in one or more specified orientations relative to a reference coordinate system, measuring the phase of each radio wave received by each of the antennas in the antenna array from the one or more radio-wave sources for each orientation of the antenna array, and then determining the errors in the array orientation coordinates using the measured phases. The method also includes determining the errors in the spacings of the antennas in the array and determining the errors in the orientation coordinates of the reference coordinate system, in both cases using the measured phases. The invention also includes apparatus for practicing the method utilizing an inertial system for maintaining the reference coordinate system.

Method and apparatus for calibrating an antenna array

A method and apparatus for performing on-board corrections to the computed navigation variables of an inertial system on an aircraft while flying over a body of water. Onboard instruments, including a barometric altimeter and a radar altimeter, measure the vertical distance of the aircraft above an ellipsoidal model of the earth and above the body of water respectively. An on-board computer calculates the differences between such heights over a plurality of points along the path the aircraft travels over the water as indicated by its inertial navigation system. The differences are compared with a map of the undulation of the geoid encompassing the region to determine the deviation of the navigated course from the true course. Appropriate corrections to the aircraft's inertial system may then be made to reduce error.

Self-contained method for correction of an inertial system over a body

Disclosed herein is a Fault-Tolerant Inertial Navigation System comprising, in a preferred embodiment, a Redundant Set of at least two Inertial Navigation Systems, from which one may identify and isolate at least one instrument within an Inertial Navigation Unit which shows substantial performance degradation. The two inertial navigation units are fully capable of performing navigational functions. Each of these inertial navigation units has a plurality of navigational instruments, including at least three linear sensors (such as accelerometers) and three angular change sensors (such as gyroscopes or ring laser gyroscopes). No two linear sensors nor any two angular change sensors of either unit are aligned colinearly. Each of the inertial navigation units produces a set of independent navigational solutions at each of their respective outputs. The independent navigational solutions of each of the navigation units are compared and any significantly degraded performance of any one linear sensor or any one angular change sensor is detected.

Fault-tolerant inertial navigation system

A navigation method and apparatus for reducing substantially the measurement errors such as accelerometer bias, gyro drift rate, gyro scale factor errors, and gyro sensing axis orientation uncertainty. The navigation apparatus includes a first gimbal for rotating a triad of gyroscopes and accelerometers about a first gimbal axis at a predetermined angular rate. The axis is positioned in a plane whose orientation is fixed in inertial space (as, for example, parallel to the earth's equatorial plane). The direction of rotation about the first gimbal axis is periodically reversed. A second gimbal is provided for rotating the triad of gyroscopes and accelerometers at a predetermined control angular rate. The second gimbal axis is directed along an axis orthogonal to the plane described above whose orientation is fixed in inertial space (as, for example, the earth's polar axis if this plane is parallel to the equatorial plane of the earth). The direction of rotation about the second gimbal axis is periodically reversed.

Method and apparatus for reducing measurement errors in a navigation

The present method involves the detection of variations of the direction of gravity from the mathematical model of the earth, which may be caused by the presence of a discontinuity in the earth's surface, with relatively heavy materials in the earth's crust causing a deflection of gravity toward such heavier material. In accordance with the present method an inertial system is mounted in a mobile vehicle and the vehicle is moved along a survey route from a first control point to a second control point, with the locations and the deflection from the vertical being known at the two control points. The vehicle is stopped periodically between the two control points in order to eliminate accumulate errors in the inertial system, and to record the position of intermediate points to the surveyed. At each of the stopping points the indicated position of the stopping points relative to latitude, longitude, and elevation are recorded, and additional inertial system parameters are recorded as required to determine the deflection of the vertical at each of the survey points. To avoid complex intermingling of errors associated with the inertial system with the change in the deflection of the vertical, the inertial platform is not releveled at each of the stopping points. When the vehicle reaches the second control point, the position indicated by the inertial guidance system is compared with the actual position of the second control point as to latitude, longitude, and elevation, and following the determination of errors, the position of the various intermediate stopping points are recalculated taking the overall error and the time at which each point was surveyed into consideration. Similarly, the error in the deflection of the vertical, which is separate from the error in position, is determined, and the deflection from the vertical of each of the intermediate survey points is then determined. The results of the survey may then be plotted on a map.

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Chatsworth, CA, United States of America

James R Huddle