Design and analysis of an augmented reduced-order active disturbance rejection control for nonlinear uncertain system

This paper proposes an augmented reduced-order active disturbance rejection control (ARADRC) to address the control challenges in nonlinear systems with unknown disturbances.An augmented reduced-order extended state observer (ARESO) is constructed to estimate the unmeasured states, the total disturbance, and its derivatives.Compared to conventional ESOs, the proposed ARESO can enhance the estimation performance by actively estimating the derivatives of the total disturbance.In the time domain, by an inductive decoupling-based bound analysis method, this paper rigorously investigates the closed-loop transient performance without the prior assumption on the boundedness of derivatives of nonlinear uncertainties.In the frequency domain, a comparative analysis demonstrates the superiority of ARADRC in both disturbance estimation and rejection.Finally, the magnetic levitationexperiments validate the effectiveness of the proposed method.