General ADRC Design for Systems with Periodic Disturbances of Unknown and Varying Frequencies

A new active disturbance rejection control-based (ADRC) scheme is proposed in this work to address the problem of tracking/rejecting periodic signals of unknown and varying frequencies. The frequencies are obtained online with a dedicated adaptive estimator and used in real-time as partial model information to an observer that reconstructs (among other things) the negative influence of periodic terms on the controlled output. A continuously updated two-tier control action is then applied to compensate the periodic interference and govern the resultant (simplified) plant dynamics. The proposed control topology is derived here in its general form and validated with an experimental case study.