Some remarks on H∞-sensitivity minimization

Recently a new approach to the disturbance response problem in feedback design has been presented by Zames [1] and Zames and Francis [2]. This approach poses design as an optimization problem minimizing the weighted H^∞ norm of the system sensitivity function subject to the condition that the closed loop system be stable. In particular, limitations imposed by non-minimum phase plant zeros are addressed. The purpose of the present paper is to discuss H^∞ designs with regard to satisfaction of design specifications on the magnitude of the sensitivity function.