Design of predictive active disturbance rejection controller for turbidity

Turbidity process, which involves complex physical and chemical reactions, is difficult to control for engineers due to its characteristics of large time-delay, uncertainties and disturbances. For this reason, a novel predictive active disturbance rejection control (PADRC) strategy is proposed, which owns the advantages of predictive control and active disturbance rejection control (ADRC). The ADRC part aims to estimate the total disturbances, and cancel from the control output to deal with the uncertainties; the predictor part is adopted to predict the output to compensate the lack of data resulted from large time delay. The performance of PADRC has been analyzed in detail. In addition, a general method to solve the open-loop frequency parameters is provided, as well as the parameter tuning equations. Finally, simulation-based comparisons of PADRC and three regular control approaches has been made. The results show that PADRC has a better performance, especially in set point tracking and disturbances rejecting. Moreover, PADRC is simple, practical and easy to tune parameters, thus providing guidelines for industrial applications of similar systems.