qConsider a feedback system
with uncertain plant PD , the weighted sensitivity function is
defined as the transfer function from d to e:
qTed
=We(I+ PD K)-1
q
Suppose our performance objective is
q ||Ted||¥ =sup{||d||2 £1} ||e||2 £1
qSuppose PD Î {(I+DW2)P: D Î RH¥ , ||D||¥ <1 } and K stabilizes P. Then the robust
performance is guaranteed if
•