Frequency-domain design of multivariable control systems for insensitivity to large plant modeling errors

Characterization of the sensitivity of multiloop feed-back control systems to unknown-but-bounded frequency-dependent plant variations is considered. Recent L2 conic sector techniques for generating tight weighted L2-norm bounds on response variation are found to lead to a precise method for quantitative characterization of - and for practical computer-aided evaluation of - multiloop feedback sensitivity to large-but-bounded frequency-dependent plant variations. The results form a natural multivariable extension of classical single-input-single-output system sensitivity ideas. Design implications are discussed.