Discrete implementation and generalization of the extended state observer

Abstract

A brief review of developments in disturbance observers, leading up to the extended state observer (ESO), is first presented. Various digital implementations of the ESO are investigated and compared. The realization in current discrete estimator form evidently helps to maintain stable operation at low sampling rates. Digitization using zero order hold is derived symbolically to further improve accuracy while preserving the simplicity of single parameter tuning. Finally, the ESO is reformulated using a generalized disturbance model which provides a wider range of solutions for disturbance estimation problems. Application of the proposed algorithm is shown on a realistic motion control simulation platform with favorable results.