Passivity-based attitude control for an integrated power and attitude control system using variable speed control moment gyroscopes

The attitude control of a rigid spacecraft with a cluster of N variable speed control moment gyroscopes is considered from a perspective of passivity. The dynamics are derived using a special form of Euler-Lagrange equations. The spacecraft dynamics and unit quaternion kinematics are shown to be passive. A proportional-integral controller is proposed to make the feedback system passive, which closely resembles previous controller designs using Lyapunov analysis. Consequently, the attitude errors are shown to be globally asymptotically stable. A null space solution is used to provide power tracking of the spacecraft. Numerical simulations are provided for validation.