Sliding Mode Control Chattering Reduction using Output-Based Torque Filter: Design and Implementation for Low-Chatter Control of a Two-Rotor Aerodynamic System

The inherent cross-coupling, under-actuation, and strong nonlinearities of the Two-Rotor Aerodynamic System (TRAS) present significant challenges in achieving high-precision tracking and robust disturbance rejection. While Sliding Mode Control (SMC) is a proven strategy in mitigating such uncertainties, its practical implementation is frequently hindered by the chattering phenomenon. This high-frequency switching, caused by the discontinuous signum function, can excite unmodeled high-frequency actuator dynamics and lead to mechanical wear and reduced control effectiveness. To alleviate this, this paper proposes an Output-Based Torque Chattering Filter (OBTCF) integrated into a conventional SMC framework. The OBTCF is formulated as a second-order dynamic filter designed to attenuate the discontinuous component of the control law, thereby suppressing high-frequency oscillations while maintaining the phase margin and avoiding significant delays. Global practical convergence of the sliding manifold under the hybrid SMC-OBTCF architecture is rigorously established via Lyapunov stability analysis. The efficacy of the proposed scheme was validated through numerical simulations and real-time experimental implementation on the INTECO 2-DOF TRAS platform. Comparative performance was quantified using Chattering Index (CI), Energy Consumption (EN), and Root Mean Square Error (RMSE). Results demonstrate that the SMC-OBTCF significantly outperforms conventional SMC and Integral SMC (ISMC), achieving a chattering reduction of approximately 94% in simulation and 68% in experimental assessments. These findings confirm that the proposed hybrid controller provides a robust, hardware-friendly solution for chattering attenuation in high-precision, nonlinear electromechanical systems.