Nonlinear Spacecraft Attitude Control Design Using Modified Rodrigues Parameters

This paper addresses the problem of spacecraft attitude control while optimizing the energy usage, which is nonlinear and coupled in nature. A suboptimal controller is derived using the state-dependent Riccati equation approach within a nonlinear setting. Modified Rodrigues parameters are utilized for describing the attitude of the spacecraft. It is also shown that single state-dependent coefficients parameterization based on these parameters never fails to operate, resulting in maximum point-wise controllable space, and is applicable to the whole maneuvering domain without any breakdowns. The proposed controller design also renders local asymptotic stability of the system. Owing to the nonlinear framework used, the controller remains effective even for the scenarios where deviations are significantly higher. Finally, comparative simulation results are presented for various initial conditions to highlight the superiority of the proposed scheme over existing ones.