Chapter 5 - RH∞ Control

Abstract

The control problem for linear time-invariant systems has been classically tackled in the frequency domain. In general, the philosophy underlying the adopted synthesis procedure strongly affects the result: having either ignored or taken into account the inaccurate knowledge of the process model makes the controller quite different. Moreover, the design procedure significantly depends on the adopted description of the uncertainty. The design problem is faced in nominal conditions—that is the process is supposed perfectly known. Some typical situations in which the process model is not precisely known are conveniently described by inserting a suitable perturbation into the block scheme. The topology of this scheme does therefore reflect the particular nature of the considered uncertainty. The design problem is tackled in a robust way, namely it is stated within various uncertainty scenarios, modeled in accordance with the previous discussion.