TWO GIMBAL ERROR AVERAGING ASTRO-INERTIAL NAVIGATOR

Assignee

NORTHROP CORPORATION, LOS ANGELES, CA A CORP. OF DE

Filed

Apr 3, 1989

Granted

Mar 7, 1995

Location

HUNTINGTON BEAC CA US

Abstract

A strapped down astro-inertial navigator includes a roll outer gimbal, a pitch inner gimbal and a platform coupled to the inner gimbal. An instrument cluster which includes X-axis, Y-axis and Z-axis ring laser gyros (RLGs) and associated accelerometers is mounted to the platform. Also hard mounted to the platform is a stellar sensor which includes a telescope and a solid state focal plane array which views stellar reference objects. In an astro-inertial mode of operation one or more stellar objects are tracked for a period of time. The roll and the pitch gimbals are employed to point the telescope and, periodically, to observe and average out the effects of star sensor and horizontal accelerometer errors. The star sensor error observability is accomplished by periodically rotating the inner and outer gimbals through 180° and the stellar objects once again tracked. Due to the 180° rotation boresight errors within the stellar tracker are observed and compensated for. The 180° rotation also serves to reorient the accelerometer input axes by 180°, thereby also beneficially causing accelerometer errors to average out. In a free inertial mode of operation the inner and outer gimbals are both continuously rotated through plus and minus 360° but at different rotational rates to provide 3 axis error averaging of both gyro and accelerometer errors.

Source: Google Patents