LPV modeling and LFT Uncertainty Identification for Robust Analysis: application to the VEGA Launcher during Atmospheric Phase*

In this article, the development of a proper Linear Fractional Transformation model for the robust analysis of the atmospheric controllers of the European VEGA launcher is presented. By proper it is meant a model that: (i) captures the key launcher’s behavior during the ascent atmospheric phase, (ii) has a complexity in terms of number of parameters and repetitions that does not limit the applicability of robust analyses, (iii) can be easily updated with very different trajectory profiles, and (iv) arises from a methodology that is well connected with industrial practice and can be understood and used relatively easy. This last requirement is fundamental to transfer the LFT methodology into the VEGA program, which is critical if robust analysis is to be used within their verification and validation process. The potential of the proposed methodology and the validity of the developed LFT models for robust analysis have been successfully verified using simulation data from three of the four VEGA qualification flights.