On Modified ADRC Design for Uncertain Systems Under Actuator Dynamics of Limited Bandwidth With Application to 2-DOF Helicopters

In this article, the control problem for a class of uncertain systems under limited actuator dynamics is considered. A new modified active disturbance rejection control (ADRC) design is proposed to deal with external disturbance and unmodelled uncertainties despite actuator dynamics with limited bandwidth. First, it is shown that the traditional ADRC may lead to instability of the closed-loop system under actuator dynamics of limited bandwidth. Second, the tracking error between the system state vectors and the desired trajectory under the proposed ADRC is rigorously analyzed for transient and steady performance. It is proven that the tracking error can converge to the desired region by tuning the parameters of the extended state observer (ESO) under the bandwidth in actuator dynamics. Finally, the proposed method is applied to a Quanser Aero two-degree-of-freedom (2-DOF) helicopter with external disturbance and unmodelled dynamics. The experimental results show the superiority of our method over traditional ADRC.