Multivariable H2 and robust control

The //2-optimal eontrol problem is to find a stabilizing eontroller C(.v) in equation (9.163) for an augmented plant P(.v) in equation (9.161), sueh that the elosed-loop transfer funetion matrix Tyiui in equation (9.162) is minimized. 

Equation (9.173) is also ealled the small gain infinity-norm eontrol problem. 

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