Adaptive Reduced Attitude Control for Rigid Spacecraft With Elliptical Pointing Constraints

This article investigates the reduced attitude control problem of a rigid spacecraft subject to elliptical pointing constraints and parameter uncertainties. Specifically, a diffeomorphic projection is proposed to map the constraints from 2-sphere to elliptical 2-sphere while with the pointing direction preserved. Then, the constrained reduced attitude control problem is transformed into a conventional obstacle avoidance problem on the 2-dimensional (2-D) Euclidean space via the elliptical stereographic projection. Benefiting from properties of the diffeomorphism and Kodischek–Rimon navigation functions, a sufficient condition to exclude local minima is obtained. A constrained adaptive reduced attitude controller is further developed and it is shown that almost asymptotical stability of the resulting closed-loop system can be ensured in the sense of a measure zero set. Finally, numerical examples are furnished to illustrate the effectiveness of the proposed controller.