Performance-Based Switched-EID Estimator for Unknown Disturbances

The equivalent-input-disturbance (EID) estimator is developed to cope with passive disturbances. However, existing EID estimators were designed only for disturbances of the single-mode characteristics. In this paper, a switched-EID (SEID) estimator is developed to deal with unknown disturbances of multi-mode characteristics. Firstly, the configuration of the SEID based control system is presented. Treating the state observer as an ideal plant free of disturbances, the output error between the real system and the observer is used to extract the dominant frequency information online by the windowed short-time Fourier transform (STFT) algorithm and then the switching logic of the SEID estimator is established. Further, the SEID estimator is analyzed and a sufficient condition is derived to guarantee the stability of the SEID closed-loop system. Lastly, a numerical simulation and comparisons with a conventional EID estimator validate the effectiveness of the developed method.