Transfer Alignment for Space Vehicles Launched from a Moving Base

Abstract

Alignment of the inertial measurement unit (IMU) is a prerequisite for any space vehicle with self-contained navigation and guidance for any mission-critical application. Normally, inertial measurement unit is aligned through gyro-compassing using the stored data for heading. In case of launch from a moving base, it is essential to align the inertial measurement unit in the vehicle (slave unit) with that mounted on the moving platform (master unit). The master inertial navigation system is more accurate, stable, and calibrated wrt the slave unit. An error propagation system involving the misalignment between the master and the slave has been formulated involving the three misalignment angles, three velocity errors, and three positional errors. The manoeuvre of the moving base excites the sensors of both the master and the slave inertial navigation systems for the generation of data to be used in aligning the slave inertial measurement unit of the inertial navigation system (strapdown mode). The entire duration of manoeuvre has to be reduced to a minimum with minimum effort of manoeuvre. This involves the deployment of an adaptive estimator and a linear quadratic Gaussian regulator for alignment of the strapdown slave inertial navigation system.