A hybrid model-assisted LADRC framework for underactuated non-minimum-phase control: implementation on a single-link inverted pendulum

This paper proposes a novel switching control strategy based on model-assisted linear active disturbance rejection control (MA-LADRC) to address control accuracy reduction in underactuated, non-minimum-phase systems under uncertainties. By incorporating partial model information into the LADRC framework, a model-assisted linear extended state observer (MA-LESO) is developed to enhance disturbance estimation while preserving the model-free nature and robustness of LADRC. This enables seamless and bumpless mode transitions between the swing-up and stabilization phases, with Lyapunov-based guarantees of time-domain stability and input continuity. Experimental studies on a single-link inverted pendulum under no-load, rigid-load, and flexible-load conditions demonstrate that the proposed method outperforms traditional PID, LQR, and LADRC controllers, achieving up to 27% lower IAE and consistent reductions in ISE and ITAE across varying operating conditions. The proposed MA-LADRC framework shows clear benefits on this representative underactuated platform. While the design principles are expected to generalize related single-DoF non-minimum-phase systems, broader validation on structurally different plants will be pursued in future work.