H∞ missile autopilot design with and without imaginary axis zeros

An acceleration command missile autopilot design using H_∞ state feedback is developed for a singular design problem that has imaginary axis zeros at infinity. A frequency domain loop shifting method is used to derive a full information state feedback controller. Results from the singular design problem are compared with results obtained from a nonsingular design problem. Two important lessons were learned from the study. The first was that the numerical conditioning of the algebraic Riccati solution matrix is closely related to the weighting functions used in the design. The second lesson was that the bilinear transform, by mapping the jw axis zero far into the right half plane, resulted in a high bandwidth control that had high actuator rate requirements. Significant rework of the weighting function design was required to make the design workable.