Eigenstructure retention with frequency weighting

This paper illustrates a design methodology which allows one to trade-off performance with robustness, as characterized by frequency domain properties such as loop gain. The basic performance and stability goals are achieved with a nominal linear quadratic regulator design. Frequency domain issues are then integrated into the design by using in the next phase of design, a frequency weighted performance criterion. The structure of this performance criterion allows the eigenstructure associated with the nominal design to be retained. An unstable nonminimum phase example illustrates the methodology.