RRT-Based Steering Law for Singularity Avoidance of Control Moment Gyros used for Spacecraft Target Acquisition

A cluster of single gimbal control moment gyroscopes (CMGs) is commonly employed on spacecraft for generating large torques, for fast in-track and cross-track maneuvers. It is well-known that the presence of singular configurations presents challenges when using CMGs for high-precision maneuvers. In this paper, we pose the problem of steering the attitude dynamics of a spacecraft in the context of robotic motion planning, and investigate the use of a Rapidly-Exploring Random Trees (RRT) algorithm for singularity avoidance. The analogy exploited in this approach is that between a singularity and a solid obstacle in the motion planning problem. We demonstrate the effectiveness of the singularity avoidance algorithm through numerical simulation of a CMG cluster on a rigid spacecraft performing target acquisition. The study compares the performance, based on the error in the torque tracking and value of the singularity index for the RRT algorithm vis-a-vis conventional steering laws.