This chapter introduces the closed-form analytical design of proportional-integral (PI) controller parameters for the optimal control subjected to operational constraints. The main idea of the design is not only to minimize the control performance index but also to cope with the constraints in the process variable, controller output, and its rate of change. The proposed optimization-based approach is examined to regulatory and servo control of integrating processes with three typical operation constraints. To derive an analytical design formula, the constrained optimal control problem in the time domain was transformed to an unconstrained optimization in a new parameter space associated with closed-loop dynamics. By taking the advantage of the proposed analytical approach, the optimal PI parameters can be found quickly based on the graphical analysis without complex numerical optimization. The resulting optimal PI controller guarantees the globally optimal closed-loop response and handles the operational constraints precisely.
Part of the book: PID Control for Industrial Processes