Robustness of Multivariable Digital Controllers using Step-Response Method

In complex unknown multivariable plants, obtainig a detailed accurate mathematical model of the plant, in the state-space or transfer function matrix form, could be either very difficult or 'm some cases impossible Design of robust multivariable digital PID controllers using step response matrices of the plant, circumvent the need of such models. These controllers are applicable to linear multivariable stable plants and in the case of unstable plants, a further inner loop compensation for stabilization of the plant is necessary. In this paper the above robust multivariable digital PID controllers are designed for a 3-input 3output drum-type boiler model. This industrial plant is considered over a range of parameters which includes both stable and unstable models. The effectivness of the above control methodology for the boiler control are shown using simulation results.