Abstract
Generally, chemical processes behave nonlinearly. But existing well-developed controller design techniques are based on linearized models of nonlinear processes. The neglected nonlinear effects affect the stability of control systems. Robustness degree, a new measure for robust control, is introduced and studied from the engineering point of view. The concept of robustness degree, proposed by applying the semigroup theory of functional analysis, can play a role in analysis and design of control systems. It is a sufficient and quantitative measure of the margin of stability within which certain nonlinear functions and modelling errors can be tolerated. Robustness degree of an open-loop or closed-loop system is linked with system matrix measure as an estimation that is straightforward and easy to calculate. A chemical reactor is studied as an example of robust control system design by this approach.
