Steering laws of Single Gimbal Control Moment Gyros applied to spacecraft manoeuvres and tracking - A comparison

In this paper an attempt is made to compare four steering laws used for Single Gimbal Control Moment Gyros (SG CMGs). The performance of a rigid spacecraft to execute multi-target acquisition and tracking with four SG CMGs in pyramid configuration is studied and steering law performance evaluated. The first steering law under consideration is the classic Moore-Penrose Pseudo Inverse(MPI). Subsequently, this is modified by adding null motion using inverse gain and null projection method. Then a steering law based on Preferred Gimbal Angles (PGA) is studied. The laws are compared based on the normalized singularity measure, gimbal rates, gimbal angles, output torque, attitude performance and angular momentum demand. The gimbal motor rates are restricted owing to hardware limits. This results in torque errors which affect the attitude of the spacecraft.