Ascent Flight Control System for Reusable Launch Vehicles: Full Order and Structured H∞ Designs

Abstract

In this work the problem of designing and analyzing Ascent Flight Control Systems for reusable launch vehicles in endo-atmospheric flight is tackled, with emphasis on the CALLISTO first stage demonstrator, a trilateral collaboration by DLR, JAXA and CNES; for which a set of different and advanced Guidance and Control methods are currently being developed. The dynamics of the system is presented in the form of a set of non-linear differential equations and their corresponding simplifications. The full order plant dynamics is reduced to more simpler, yet representative subsystems. The equations are then linearized along trajectory for the calculation of the nominal LTIs and LFTs using the reference perturbation envelope for the the baseline scenario. The controllers are built by employing the $\hinf$ synthesis framework with the full order and PD-like structured controller architectures. The mission objectives and requirements are translated into control objectives using loop-shaping functions. Furthermore, the results are a set of controllers that are validated into different simulation layers. Results are presented in the form of Monte Carlo simulations.