A survey on active disturbance rejection control

The conventional PID controllers have been in existence in the process industry from its very birth for almost a century. The empirical approach of the PID presents a limitation in tuning for practising engineers, since it requires ample experience and a sound knowledge of the plant. Another approach that came up with the development of modern control paradigm also had an inherent drawback of model dependency. Tuning of controllers in model based approach was challenging due to the mismatch of the actual system with approximate model. This situation demanded, a model independent approach to take care of the uncertainties of the plant, including the disturbances and the unknown dynamics of the plant. The principle of Active Disturbance Rejection Control(ADRC) satisfactorily tackles the drawbacks of both PID and model based approaches. It proves successful in a variety of industrial applications. The unique features of ADRC are the robustness of the controller and its rich capability in uncertainty reduction. This paper presents a survey on Active Disturbance Rejection Control and its developments.