Design of quaternion-based synergetic attitude control for microsatellite using control moment gyros

Abstract

Control moment gyros (CMGs) are some of the most effective actuators for the attitude control of spacecrafts. They can be considered as ideal actuators for achieving the large angular momentum within the limited space, size, and power consumption. However, the use of CMGs is complicated due to their nonlinearity and geometric singularity. In this research, four constant-speed CMGs formed in a pyramidal configuration are adopted as the attitude actuators for a microsatellite. The dynamics and the kinematics of the satellite are represented by Euler's and quaternion equations, respectively. To deal with the nonlinearity, the attitude controller is derived based on a synergetic control approach, and the stability of the control system is guaranteed by showing the existence of a Lyapunov function. The singularity is avoided by utilizing a modified singularity robust steering law. The effectiveness of the proposed control system is demonstrated in computer simulations.