Flight Controller Design Using Mixed H\u3csub\u3e2\u3c/sub\u3e/H\u3csub\u3e∞\u3c/sub\u3e Optimization with a singular H\u3csub\u3e∞\u3c/sub\u3e Constraint

This thesis explores the effectiveness of mixed H2/H∞ optimal control design applied to a realistic flight control problem. The application used by this thesis is a single input single output problem dealing with a normal acceleration command following model of the AFTI F-16. The mixed H2/H∞ control problem is broken into its component H2 and H∞ parts the H2 part is formulated as an LQG problem, and a weight is applied to system sensitivity in the H∞ problem to obtain tracking performance. The sensitivity weight in the underlying H∞ part results in a singular constraint on the mixed problem. A newly-developed numerical technique is applied and solutions are obtained for controllers of order equal to, first, the order of the underlying H2 problem and, second, the order of the underlying H∞ problem. Performance characteristics of these controllers are compared to controllers designed using the more-conventional LQGLTR design method. The results indicate the potential for controllers obtained through mixed H2H∞ optimization to provide excellent performance and robustness characteristics at orders less than those obtained through LQGLTR. Since this conclusion grows in significance when applied to multiple input multiple output MIMO problems, a three input, five output example is introduced and the underlying H2 and H∞ problems for two solution approaches are formulated