Multi-model cascade control strategy design based on gap metric for nonlinear processes

A multi-model control system in cascade configuration using hard and soft switching for the nonlinear process is addressed in this research. Cascade control is a widely known strategy in process plants to improve control performance in the presence of disturbances. It has been found that the incorporation of conventional cascade controllers was ineffective when applied to nonlinear processes. Multi-model control schemes are capable of providing enhanced performance when compared to the conventional control schemes for nonlinear systems. This paper presents the multi-model approach (MMA) in the cascade control strategy by using hard and soft switching for selection of the controller. Simulation studies are demonstrated on nonlinear processes (isothermal CSTR, conical tank and spherical tank) and experimentally applied on the conical tank process. The performance of the cascade multi-model control strategy is superior when compared to the classical multi-model control strategy. It is observed that the cascade multi-model control strategy has provided faster response and improved disturbance rejection. [GRAPHICS]