# Controller order reduction of continuous-time and discrete-time $H_\infty$ problems based on bilinear transformations

Takao Watanabe, Antonie Arij Stoorvogel

This paper establishes a new class of the reduced-order controllers in the continuous-time as well as discrete-time $H_\infty$ control problems. The reduced-order controllers are characterized by unstable transmission zeros of off-diagonal subsystems in the generalized plant. Algorithms to obtain the reduced-order controllers are presented in both problems.