Attitude Control of a Reentry Vehicle with Internal Dynamics

Abstract

A control design for the X-38 reentry vehicle is presented. During a certain phase of reentry e ight, attitude control has to be accomplished using only two control effectors. This limits the number of controlled variables for which decoupled tracking can be realized. It is shown that an inappropriate selection of the output gives rise to unacceptable internal dynamics when applying inversion-based control. Therefore, the zero dynamics are locally stabilized by means of an output-redee nition technique. An optimal pole placement enhances the robustness of the zero dynamics with regard to parametric model uncertainty. Further, a direct adaptive controller using a cerebellar model articulation controller neural network ensures tracking performance in the redee ned outputs in the presence of model uncertainty. Simulation results are presented to cone rm that stabilization of the zero dynamics, and adequate tracking performance are achieved. Because only a minimal set of control effectors is used, such a control scheme could represent a contribution toward a less costly return from space.