Moving mass trim control for aerospace vehicles

A moving mass trim controller is proposed to increase the accuracy of axisymmetric, ballistic vehicles. The moving mass trim controller differs from other moving mass schemes because it generates an angle of attack directly from the mass motion. The nonlinear equations of motion for a ballistic vehicle with one moving point mass are derived and provide the basis for a detailed simulation model. The nonlinear equations are linearized to produce a set of linear, time-varying autopilot equations. These autopilot equations are analyzed and used to develop theoretical design tools for the creation of moving mass trim controllers for both fast and slow spinning vehicles. A fast spinning moving mass trim controller is designed for a generic artillery rocket that uses principal axis misalignment to generate a trim angle of attack. A slow spinning moving mass trim controller is designed for a generic re-entry vehicle that generates a trim angle of attack with a center of mass offset and aerodynamic drag. The performance of both moving mass trim controllers are evaluated with the detailed simulation.