Uncertainty Modeling for Multivariable-Control Robustness Analysis of Elastic High-Speed Vehicles

High-speed (supersonic or hypersonic ) atmospheric e ight vehicles are typically characterized by a signie cant degree of interaction between the highly elastic airframe and the propulsion system. To achieve adequate stability and performance requirements, robust, integrated multivariable control laws will be required. But to apply robust-control analysis or synthesis techniques such as structured-singular-value techniques (π) or quantitative feedbacktheory,theuncertaintyintheplantdynamicsmustbecharacterized inspecialways.Furthermore,certain assumptions regarding the uncertainties present are frequently made in the application of these techniques. The focus of this research is the development of uncertainty models for this class of e ight vehicle that are derived from the physics of the system, yet are compatible with the cited control synthesis techniques. The potential sources of uncertainty for this class of vehicle are discussed, and three forms of uncertainty models are developed: real parameter,unstructured,and structured. Weareespecially interestedinhowtheusualsourcesofuncertaintymanifest themselves in this context. It will be shown that for this class of vehicle care is required in making the usual assumptions regarding the uncertainty. It is also shown that the e exible degrees of freedom must be considered in the e ight-control synthesis for this class of vehicle.