Design of optimal controllers for interval plant via a two-phase evolutionary approach

Design of optimal controllers minimizing the integral of squared error (ISE) of the closed-loop system for interval plant via an evolutionary approach is proposed in this paper. By using a worst-case design approach, the design problem is formulated as a minimax optimization problem, and subsequently solved by two interactive genetic algorithms. To ensure robust stability of the closed-loop system, root locations associated with the characteristic polynomial are used to construct a penalty function for incorporation into the fitness function to effectively evaluate chromosomes in the current population. Thus, the optimal controllers evolutionarily derived not only stabilize the interval plant, but also minimize the ISE criterion of the closed-loop system.