A Novel ADRC Design with Cascade of Observers for Rigid-body Motion Control Systems

This paper considers the disturbance rejection problem for general rigid-body motion control systems. A novel active disturbance rejection control (ADRC) design with cascade of one high gain observer and one reduced-order extended state observer is proposed. It is shown that compared with the regular ADRC, the proposed ADRC method only needs the control direction, avoiding the difficulty of choosing the nominal control input gain. Moreover, such novel design has the same order as that of normal extended state observer. Moreover, it can be proved that the resulting closed-loop system is semi-globally uniformly bounded (SGUB). Finally, simulation results of a 1 degree-of-freedom (DOF) manipulator control system demonstrate the effectiveness of our method.