Nonlinear Optimal Reentry Guidance and Control of RLV in Pitch Plane

A nonlinear optimal guidance and control scheme for the atmospheric reentry of an RLV using pitch plane maneuver is presented. The guidance law generates an angle of attack control command that satisfies the terminal constraints (considered as hard constraints) and the path constraints (considered as soft minimizable constraints). The guidance update process is done rapidly and in closed form using model predictive static programming (MPSP), a technique that provides a finite time nonlinear suboptimal guidance law. A nonlinear optimal controller for the reaction control system (RCS) and aerodynamic controls has been designed using dynamic inversion (DI) and optimal dynamic inversion (ODI) respectively. A fusion logic for the RCS and aerodynamic control combination provides the total control action required. After each guidance cycle, the guidance command updates the trajectory using the actual states obtained from the control design. The control design is found to track the guidance commands well for perturbations in the initial reentry conditions.