Cascade Active Disturbance Rejection Control of a High-Purity Distillation Column with Measurement Noise

Control of high-purity distillation columns is a challenging problem due to their unique characteristics, such as complex dynamics, high nonlinearity, and interaction between the control loops. In this paper, a cascade control strategy, based on active disturbance rejection control, is proposed for a high-purity distillation column. With the proposed strategy, it is shown that the distillation column is almost decoupled by using the extended state observer to estimate and reject the effects of both the internal plant dynamics and the external disturbances. Considering measurement noise, an extended state observer that switches between two gain values is proposed. On the basis of this scheme, the extended state observer can quickly estimate the system state and also reduce the effect of measurement noise. Finally, the simulation results evidence the efficacy of the proposed method.