Optimal Guidance Command Generation And Tracking For The Reentry Of A Reusable Launch Vehicle Preprint

In this work, optimal outer-loop guidance commands are generated from an off-line reference trajectory and then tracked by a reconfigurable inner-loop control law. The primary motivation for this work is a "stepping-stone" towards online, optimal trajectory generation, footprint determination, and retargeting capabilities in the presence of control effector failures or vehicle structural/ aerodynamic degradation, uncertainty, and external disturbances. The presented guidance and control architecture uses a 6-degree-of-freedom simulation and an inner-loop controller to track body-name angular rates (roll, pitch, and yaw), generated from an optimal psuedo-4-degree-of-freedom reference trajectory that is computed using a direct pseudo spectral method. The innerloop control law is capable of reacting and compensating for off-nominal conditions by employing its nonlinear control allocation, dynamic inversion, and model-following/anti-windup prefilters. The results show that the inner-loop control can adequately track the desired optimal guidance commands; thus, confirming the applicability of this control architecture for future development involving on-line, optimal trajectory generation and high-fidelity footprint determination for reentry vehicles.