Robust Multi-Objective H∞ Control of GHAME Hypersonic Vehicle in Subsonic Flight

Abstract

This research is aimed at developing a comprehensive approach for robust hypersonic vehicle (HV) control utilizing modern H∞ techniques. Initial focus is placed on subsonic flight condition to validate the framework and controller design in a relatively familiar field, for which the HV are not primarily optimized. A 6-degree-of-freedom non-linear model of the GHAME hypersonic vehicle was constructed in MATLAB/Simulink, incorporating tensor-based equations of motion and embedded parametric uncertainty in the aerodynamic coefficients. The linear short-period longitudinal dynamics were then extracted at multiple operating points. A controller of fixed structure was synthesized using multi-objective (multidisk) H∞ mixed-sensitivity techniques with various performance and robustness requirements covering the pitch moment coefficient parametric uncertainty domain. Additionally, the design is extended to handle variations in Mach number, altitude, and fuel mass around the trim point using a multi-model approach. A single, structured control system successfully stabilized, rejected input and output disturbances and provided reference tracking for the uncertain short-period models and met the robustness margin requirements for the entire grid. It was then tested on the non-linear model and successfully performed the same tasks under parameter variations across the flight point grid.