Analysis of the Controlled NASA HL20 Atmospheric Re-Entry Vehicle Based on Dynamic IQCs

Abstract

The analysis of complicated nonlinear systems is mostly considered as very challenging. Moreover, the available methods and tools suggested in the literature are scarce and not well tested on complex applications. This paper proposes a general procedure based on linear fractional representations (LFR), Integral quadratic constraints (IQC) and mu-theory for the analysis of a linear parameter-varying (LPV) controller that was designed for the NASA HL20 vehicle for a re-entry mission. An LFR was obtained through trimming, linearization and polynomial interpolation of the strongly nonlinear dynamical equations and will be used for the analysis, in order to guarantee stability and a high performance certificate over a large operation range. Special attention is being paid to time invariant parametric uncertainties, smoothly time-varying parametric uncertainties with bounded rates-of-variation, odd-monotone and slope restricted uncertainties to analyze the closed-loop system subject to actuator saturation and uncertain time-delay.