Observer Based Design of Normal Mode Attitude Control for IRS Satellite

Abstract

The attitude and orbital control system for the Indian Remote Sensing (IRS) Satellite to be put into the Sun-synchronous 10 O’clock polar orbit during 1986, has to meet very stringent body rate specifications of the order 0.0003 deg sec^-1 in the normal-mode operation. In order to meet these low body rate specifications, an onboard microprocessor based observer is envisaged. Initial design of observer with errors and body rate estimates alone was found to be inadequate in the presence of disturbance torques. It was thus found necessary to modify the observer design in order to estimate the disturbance torques, thereby, improving the estimates of the body rates and attitude errors. In this paper various refinements attempted are examined, and some of the simulation results are presented.