MIXED SENSITIVITY OPTIMIZATION TO AVOID POLE ZERO CANCELLATION/

We give a detailed discussion of the mixed sensitivity formulation pro posed by Kwakernaak and explore the useful ideas behind it. We prove t hat this two-block mixed sensitivity problem is closely related to a f our-block problem, and therefore to some extent can attain a balanced design among all transfer functions of a closed-loop system. We make s ome interesting comparisons between this approach and the well-known l oop shaping design of McFarlane and Glover. We also show that this mix ed sensitivity approach is superior to others because it can provide u s with extra flexibility in shaping the sensitivity functions and lead to a controller of minimal order. (C) 1997 Elsevier Science Ltd.