Active Disturbance Rejection Control of a Neutralisation Process

This paper presents active disturbance rejection control (ADRC) of pH in a neutralisation process. As pH dynamics is highly nonlinear and not control-affine, direct application of ADRC using pH as the controlled variable is not effective. To overcome this problem, an artificial variable, which has one-to-one mapping with pH and is control affine, is defined as the controlled variable for ADRC. A method for tuning ADRC using step response data is proposed. Application results show that ADRC can give excellent control performance for pH control.