Model-based guidance and control for atmospheric guided entry

This paper presents a solution of the translational control for a biconic atmospheric entry capsule using the bank angle as a command. The control algorithm is separated into path planning and reference-path tracking. The path-planning algorithm computes the entry trajectory from the navigated state at the Entry Interface Point until the desired Parachute Deployment Point. The algorithm aims to recover the landing site uncertainty caused by Entry Interface Point dispersions. Atmospheric and aerodynamic dispersions are compensated in real-time following the Embedded Model Control methodology in which parametric uncertainty is estimated and rejected as an external disturbance. A hierarchical control structure is designed for facilitating non-linear dynamic inversion of the altitude/density relation and tuning of noise estimators and control laws. Both path planning and reference-path tracking exploit longitudinal and lateral decomposition of the translational dynamics, as well as state equation linearization around a reference trajectory. The main concepts and solutions of the algorithms are presented without formal proofs of convergence, performance and stability. The results of a Monte Carlo simulation campaign conducted on a high fidelity simulator are provided and discussed.