Worst case analysis of the flight control system X-38 crew return vehicle

摘要

A linear fractional transformation (LFT) model of the linearized equation of the lateral-directional axes of the X-38 Crew Return Vehicle is developed to facilitate the analysis of flight control systems. ^The LFT model represents the uncertainty in nine aerodynamic stability derivatives at a given flight condition with frequency domain performance specification. ^The X-38 LFT model combined with a controller at specific flight conditions is used to determine the aerodynamic coefficients that result in the worst-case performance and gain/phase margin of the closed-loop system. ^The objective is to verify that a given controller remains stable and achieves desired performance objectives for all defined aerodynamic variations at select operating conditions along its flight trajectory. ^(Author)