Parametric uncertainty reduction in robust missile autopilot design

The mu-synthesis design procedure provides a very general framework for the design of robust autopilots. The mu-synthesis technique seeks to minimize the structured singular value of the closed-loop transfer function from disturbances and perturbations to reference outputs and the outputs to the perturbations. In a number of missile autopilot design applications, it has been found that the mu-synthesis algorithm performs better if the number of perturbations can be reduced. A method of reducing the number of modeled uncertainties is presented which can alleviate the associated convergence and numerical problems before application of mu-synthesis. The reduction is accomplished by deleting some uncertainties and scaling the remaining uncertainties to compensate for those deleted. After completion of the mu-synthesis design procedure, robust performance is analyzed using the complete set of uncertainties. The application of this procedure yielded improvements in the robust performance of autopilots when compared to the direct application of mu-synthesis. (AIAA)