Nonlinear attitude and shape control of spacecraft with articulated appendages and reaction wheels

Abstract

Three-dimensional attitude and shape control problems are studied for a class of spacecraft with articulated appendages and reaction wheels. A number of special cases of such attitude control problems have been studied previously. We provide a unified formulation and a comprehensive set of results for planning of attitude and shape maneuvers of a spacecraft, assuming that joint actuators and reaction wheels provide a sufficiently rich set of inputs. The development is based on a nonlinear, drift-free, control model that characterizes the attitude and shape change dynamics, assuming zero angular momentum of the system. Controllability results are presented for the general case, and specialized results are identified for interesting multibody spacecraft configurations. These results are made explicit by providing computable formulas for the Lie brackets in terms of the spacecraft geometry, mass properties, and shape. Constructive motion planning approaches are described to achieve spacecraft attitude and shape change maneuvers. A distinct feature of these approaches is that they require only simple computations, as is desirable for online implementation. Emphasis is given to the interplay between the shape change dynamics and the attitude change dynamics in achieving the maneuver planning objectives.