Development Of High Angle Of Attack Control Laws For An Unstable Non Minimum Phase Aircraft Using Variations Of The Quantitative Feedback Technique PDF Download

This thesis discusses the application of variations of the quantitative feedback technique to a control problem with unstable, non-minimum phase plants. The X-29A research aircraft is used as the basis for developing a set of representative linearized aircraft dynamics models, which are modified to allow for the use of differential canard control inputs for enhanced maneuverability at extreme angles of attack. A specialized design approach is presented to develop frequency dependent weighting matrices, and the shortcomings of traditional methods are discussed. Four independent longitudinal compensators are developed by first designing loop transmission functions. Discussion is provided that addresses the limitations imposed on the designer by the numerous right half plane poles and zeros of the effective plants. The optimal blending method is applied in one case to achieve a marginally stable system for a virtually impossible problem. Prefilters are designed and their effects on closed-loop time responses are discussed. The singular-G method is used to improve the achievable stability characterisitics of a multi-input multi-output lateral-directional controller. The optimal blending method is then applied to develop an optimal loop transmission function. Finally, the required steps for completing the MIMO design are presented to aid future research efforts.