Modified ESO based RC for improved disturbance rejection capability for the plant with time-varying uncertainty

A modified robust controller is proposed, to regulate uncertainties in system dynamics and external disturbances, for the plant with relative degree greater than zero. The design is based on the concept of extended state observer (ESO) with repetitive controller (RC). In real time estimation and mitigation of the total effect of various uncertainties, ESO based RC is particularly effective against a wide range of parameter variations, model uncertainties, and large disturbances. With only two tuning parameters, the controller provides a simple and user friendly solution to complex engineering problems in practice. The comparison results verified the effectiveness of the ESO based RC over state observer (SO) based RC.