IQC-Based Robustness Analysis with Time-Varying Multipliers

This work deals with the use of time-varying integral quadratic constraint (IQC) multipliers when conducting robustness analysis. The main result enables robustness analysis of interconnections where the nominal plant and the IQC multiplier are general time-varying linear systems. When the nominal plant and the IQC multiplier are eventually periodic (not necessarily of the same period), robustness analysis can be accomplished by solving a finite-dimensional semidefinite program. Time-varying IQC multipliers are beneficial in analysis because they (1) provide the possibility of reducing conservatism and (2) are capable of expressing uncertainties which have unique characteristics in the time domain.