Showing papers on "Inertial reference unit published in 1976"

Tetrahedral redundant inertial reference unit

Abstract: A redundant inertial reference system is provided with four gyroscope units, with the spin axes of the gyroscopes in the units being oriented, respectively, perpendicular to the four faces of an equilateral tetrahedron. Incidentally, a tetrahedron is a four sided body, and an equilateral tetrahedron is a four sided body having equilateral triangles for the four sides. With the four gyroscopes mounted perpendicular to the four sides of an equilateral tetrahedron, each of the gyroscopes is located symmetrically with respect to the others, with an angle of approximately 109.4 degrees between the spin axes of the gyroscopes. The system is particularly applicable to strapdown type inertial guidance systems and can provide three dimensional orientation information even if two of the gyros fail. The system uses four gyro units, a minimum number which can accomplish a foregoing function, with the four gyro units arranged substantially symmetrically with respect to one another.

Error Analysis of Two New Gradiometer-Aided Inertial Navigation Systems

Abstract: Two Kalman filtering integration techniques are presented for using gradiometer measurements to compensate an inertial navigation system for gravity disturbances. Both approaches use knowledge of the reference ellipsoid gravity field in addition to gradiometer data and lead to bounded residual gravity-induced navigation errors. Although the two compensation techniques are similar, one appears to offer significant theoretical and practical advantages. The mechanization and error equations for each technique are outlined and the significance of various terms which appear in these equations is discussed in the context of gradiometer-aided inertial navigation.

Inertial Navigation System Tests having Improved Observability of Error Sources

Abstract: Optimal filtering of simulated inertial navigation system (INS) test data is used to evaluate alternate laboratory and flight test echniques, which are intended to determine the value of each significant source of navigation error. Tests of both gimbaled and strapdown systems are evaluated. The major problem preventing more accurate determination of the dozens of sources of error in an INS is the high correlation between the contributions of many of the sources of error. Laboratory test sequences and flight test trajectories are presented that reduce these correlations and improve the observability of the individual sources of error. Parametric studies include the effects of flight duration and distance, multi directional flights versus straight out-and-out flights, frequency and direction of maneuvers, and supersonic flights vs subsonic flights. The effects of the range instrumentation (reference system) accuracy and measurement frequency are demonstrated.

Integrated Inertial Reference - Inertial Navigation System

Abstract: The value of Inertial Navigation Systems (INS) is reduced for long time-duration flights because uncertainties produce increased position errors with time. A reduction in this position error buildup is obtained from a mechanization concept described in this .paper. This mechanization comprises an Electrically Suspended Gyroscope (ESG) mounted on the stabilized platform of a local-level INS. Position is estimated by tracking the local vertical while accounting for the Earth's rotation with an accurate clock. Subsystems are integrated by means of a Kalman-Bucy filter. An accuracy of 0.2 n. mi./hr for 12 hr of flight was obtained in a simulation study using an ESG and a 1 n. mi./hr INS.