Model-based guidance and control for atmospheric guided entry

Abstract

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.

Model-based aerodynamic-angle attitude control of an atmospheric entry capsule

“…It is arranged following EMC into (i) a reference generator (the open-loop control, Fig 5) providing the reference bank angle  together with the first and second derivatives  and u     , (ii) a control law, combination of open-loop command, state feedback and disturbance rejection, (iii) the discrete time embedded model (combination of controllable and disturbance dynamics, Fig 6) and (iv) the noise estimator (Fig 6) providing in real-time the noise vectors updating the unknown disturbance dynamics. The bank angle control becomes the actuator of the translational control in Canuto et al 2 . The latter provides the required bank angle profile des  , which is decomposed into the reference bank angle cosine cos p  and the time instants br t of the bank reversal maneuvers.…”

“…Specifically, restricting the treatment to a biconic capsule with a fixed center of mass (CoM), the total angle of attack  and the (aerodynamic) roll  shall fluctuate around their natural equilibriums. On the contrary, the bank angle must be adjusted by a reaction control system, to drive the flight-path angle  and heading  of the vehicle entry trajectory (see Canuto et al 2 for the translation state equations).…”

“…This paper is devoted to the attitude control; path-planning and reference path-tracking algorithms are detailed in Canuto et al 2 .…”