@ARTICLE{Michalski_Jacek_Active_2026,
 author={Michalski, Jacek and Mrotek, Mikołaj and Brock, Stefan and Retinger, Marek and Kozierski, Piotr},
 volume={74},
 number={3},
 journal={Bulletin of the Polish Academy of Sciences Technical Sciences},
 pages={e158301},
 howpublished={online},
 year={2026},
 abstract={The paper deals with the application of Active Disturbance Rejection Control (ADRC) to underactuated systems with rate-controlled input dynamics, illustrated by a reaction wheel pendulum (RWP). In this class of plants, the derivative of the control signal appears in the input–output dynamics, which violates the standard integrator-chain assumption underlying classical ADRC and may degrade observer performance and closed-loop quality. To overcome this difficulty, two ADRC modifications that exploit partial model information are proposed. First, a reduced-order input–output model is derived, in which the derivative behavior of the input is analytically compensated, resulting in an affine input form compatible with the conventional ADRC structure. Second, a dual-output ADRC scheme is developed, combining an extended state observer with an inner-loop LQR-based state feedback, which enables simultaneous stabilization of the pendulum angle and the wheel speed despite a single actuator. For both variants, Lyapunov-based stability conditions are obtained. The proposed controllers are implemented and experimentally verified on a real reaction wheel pendulum setup. Swing-up-and-balance experiments around the lower and upper equilibrium positions show that the modified ADRC schemes reduce overshoot and oscillations, mitigate steady-state drift, and improve control performance with respect to a baseline model-free ADRC.},
 type={article},
 title={Active disturbance rejection control for rate-controlled input underactuated systems: Application to a reaction wheel pendulum},
 URL={http://journals.pan.pl/Content/138290/PDF/BPASTS-05514-EA.pdf},
 doi={10.24425/bpasts.2026.158301},
 keywords={active disturbance rejection control, extended state observer, reaction wheel pendulum, underactuated systems, rate-controlled input},
}