A new approach for designing a PI controller via variable structure system theory

The reluctance of using variable structure system (VSS) theory is due to the concern of excess chatter that severely limits its practical applicability. This paper presents a new approach for designing a variable structure PI controller (VSPIC) via the VSS theory with freedom from chattering. The structure of the conventional model of the PI controller is modified and the integrator is considered as a part of the plant during the designing process of the VSPIC system. Chattering will now appear at the augmented plant´s input, which consists of the original plant and the integrator, instead of the original plant´s input. This approach is then applied in designing a VSPIC of a heating system for hot water and space heating. The simulation results demonstrate that control chattering is suppressed and the heating system is well controlled