This paper presents a novel approach to the problem of almost global attitude stabilization. The reduced attitude is steered along a geodesic path on the n − 1-sphere. Meanwhile, the full attitude is stabilized on SO(n). This action, essentially two maneuvers in sequel, is fused into one smooth motion. Our algorithm is useful in applications where stabilization of the reduced attitude takes precedence over stabilization of the full attitude. A two parameter feedback gain affords further trade-offs between the full and reduced attitude convergence speed. The closed loop kinematics on SO(3) are solved for the states as functions of time and the initial conditions, providing precise knowledge of the transient dynamics. The exact solutions also help us to characterize the asymptotic behavior of the system such as establishing the region of attraction by straightforward evaluation of limits. The geometric flavor of these ideas is illustrated by a numerical example. the second category. The closed-loop kinematics on SO(3) are solved for the states as functions of time and the initial conditions, providing precise knowledge of the workings of the transient dynamics.Recent work on the problem of finding exact solutions to closed-loop systems on SO(n) includes [13,14]. Related but somewhat different problems are addressed in [6,16,22]. Earlier work [12] by the authors is strongly related but also underdeveloped; its scope is limited to the case of SO(3). This paper concerns a generalization of the equations studied in [12,14]. The results of [14] is also generalized in [13], partly towards application in model-predictive control and sampled control systems and without focus on the behavior of the reduced attitude. The work [15] addresses the problem of continuous actuation under discrete-time sampling. The exact solutions provide an alternative to the zero-order hold technique. The algorithm alternates in a fashion that is continuous in time between the closed-loop and open-loop versions of a single control law. The feedback law proposed in this paper can also be used in such applications by virtue of the exact solutions.
PreliminariesLet A, B ∈ C n×n . The spectrum of A is written as σ(A). Denote the transpose of A by A ⊤ and the complex conjugate by A * . The inner product is defined by A, B = tr(A ⊤ B) and the Frobenius norm by A F = A, A 1 2 .