On Compensation Function Observer-Based Active Disturbance Rejection Control for MIMO Uncertain Systems and Its Application to 2-DOF Helicopter System

This article investigates the control problem for multiple-input multiple-output systems with nonlinear uncertainties. By introducing a prediction-correction mechanism, a new compensation function observer (CFO) is constructed to enhance the estimation accuracy of the total disturbance. Subsequently, the CFO-based active disturbance rejection control (CADRC) is designed to mitigate the total disturbances and attain the desired control performance. Based on an inductive decoupling-based Lyapunov method, this article rigorously establishes the closed-loop stability of the CADRC under a broad class of nonlinear state-dependent uncertainties. Moreover, a comparative frequency-domain analysis quantitatively reveals the superior disturbance estimation and rejection capabilities of the CADRC. Finally, the proposed CADRC is implemented on a Quanser two-degree-of-freedom helicopter system subject to additional digital uncertainties, and the experimental results demonstrate its clear superiority over the conventional ADRC.