Research ArticleSurvey on methods of increasing the efficiency of extended state disturbance observers

- Various methods of improving the estimation quality in extended state disturbance observers (ESOs) are presented.
- Survey is motivated by the growing interest put in the active disturbance rejection control (ADRC) techniques.
- Various techniques are presented and supported with a reference, dedicated simulation, or experimental result.
- Work is dedicated to researchers and practitioners interested in increasing the efficiency of their ADRC systems.

This survey presents various methods of improving the overall estimation quality in the class of extended state observers (ESO), which estimate not only the conventional states of the system, but the acting disturbance as well. This type of observers is crucial in forming the active disturbance rejection control structure (ADRC), where the precision of online perturbation reconstruction and cancellation directly influences the robustness of the closed-loop control system. Various aspects of the observer-based disturbance estimation/rejection loop are covered by this work and divided into three categories, related with observer: structure, tuning, and working conditions. The survey is dedicated to researchers and practitioners who are interested in increasing the efficiency of their ADRC-based governing schemes.