Improved computation of mixed μ bounds for flight control law analysis

In this paper we describe an approach for improving the quality of upper and lower bounds on the structured singular value in the case of mixed real and complex uncertainty. The proposed approach uses constrained non-linear optimisation to improve the bounds on μ generated by standard algorithms, and is shown to be simple and computationally efficient to implement. The usefulness of the approach is demonstrated on the problem of checking a stability margin clearance criterion for a V/STOL aircraft flight control law.