Hierarchical approach for H∞ robust control design: S/KS mixed sensitivity with genetic algorithm

The issue of introducing generic design constraints (practical or `real-life´ constraints) in robust control design procedures is discussed. A strategy, based on a hierarchy of optimisation methods, is proposed here. An H<sub>infin</sub> design algorithm constitutes the bottom level of this hierarchy, and a general-purpose optimisation algorithm (a genetic algorithm) is employed for tuning the parameters of the H<sub>infin</sub> controller, searching for the solutions that satisfy the earlier mentioned `practical constraints´. Practical results obtained in a pilot-scale plant with fluid-level and flow-rate control as controlled variables are included to show the applicability of the proposed method.