Nonlinear and adaptive nonlinear controllers for attitude stabilization and tracking of a spacecraft

With a minimal set of three Euler angles, the attitude motion of a spacecraft is exactly described as a nonlinear, multiple input/multiple output, and cross-coupled system. In this work, the attitude motion equations are viewed as two blocks, a kinematics block and a dynamics block. Based on Lyapunov stability theory and backstepping technique, a new controller is derived from the nonlinear equations. The approach is then extended to a nonlinear attitude tracking case. Moreover, in practical attitude control, usually the moments of inertia are uncertain in value, but always positive. For this case, an adaptive nonlinear controller is developed. The effectiveness of the presented controllers is verified by simulation.