Uncertainty Modeling and Robust Analysis of Atmospheric Launchers: Incremental Steps for Industrial Transfer

Nowadays Linear Fractional Transformations (LFT) and the Structured Singular Value (mu) are very well established concepts for respectively modeling uncertain systems and to perform robust analyses. Despite their ample use in academia and industry during the last 30 years, and the availability of consolidated software toolboxes, their introduction to a new industrial collaborator is not without angst. In this article, the steps followed to transfer this technology to the GNC group at ELV, in charge of the VEGA atmospheric launcher, are presented. The aim of the transfer was to introduce worst-case analysis tools into the VEGA verification and validation process as a complement to the standard LTI gain/phase margin analyses and the nonlinear simulation-based Monte Carlo campaigns. The successful transfer hinged on the reconciliation of the following two facets: (i) the physical behavior of the system with the LFT model capabilities, and (ii) the classical design experience from the VEGA GNC group with the results from the robust mu analyses.