Uncertainty Modeling and Fixed-Order Controller Design for a Hypersonic Vehicle Model

Control system design for hypersonic vehicles will be complicated by coupling effects between aerodynamics, propulsion, and structure. Using H1 and π-synthesis techniques, these features can be modeled as uncertainties and incorporated into the design procedure of a e ight control system. However, modern control theory techniques generallyleadtohigh-ordercontrollers.Thetimedelays,whicharecreatedwhenthesecontrollersareimplemented, may not be acceptable. A technique to constrain controller dimension a priori in the design process is used to design e xed-order π controllers that are robust to mixed real/complex uncertainties. Typical hypersonic effects such as propulsion system perturbations and aeroelastic fuselage bending are modeled as uncertainties in a robust control design framework. Three different e xed-order controllers are synthesized for a hypersonic vehicle model accelerating through Mach 8. A comparison with full-order and reduced-order designs is conducted and the results illustrate that the e xed-order controllers exhibit robustness properties similar to full-order designs while considerably reducing controller complexity.