New tools for computing tight bounds on the real structured singular value

New tools are presented for the computation of tight lower bounds on the st ructured singular value mu for high-order plants subject to purely real par ametric uncertainty. The first approach uses the mu-sensitivity function to systematically reduce the order of the real uncertainty matrix, so that ex ponential time lower bound algorithms can be applied. The second approach f ormulates the search for a worst-case real destabilizing perturbation as a constrained nonlinear optimization problem. Both approaches are applied to the problem of analyzing the stability robustness properties of an integrat ed flight and propulsion control system for an experimental vertical/short takeoff and landing aircraft configuration. Currently available software to ols for calculating lower bounds on real mu fail for this problem, whereas both new approaches deliver tight bounds over the frequency range of intere st.