Disturbance Observer-Based Robust Safety-Critical Control of Nonlinear Systems with External Disturbances

This paper proposes a robust safety-critical control design approach for nonlinear systems subjected to external disturbances. The external disturbances are modeled by a linear exogenous system, representing a class of partially known harmonic disturbances. To address such disturbances, a corresponding nonlinear disturbance observer is designed for estimation. By utilizing the estimated disturbance from the disturbance observer, novel Control Barrier Function (CBF) constraints and Control Lyapunov Function (CLF) constraints are formulated. Subsequently, a safety-critical controller based on Nonlinear Disturbance Observer-Control Lyapunov Function-Control Barrier Function-Quadratic Programming (NDOB-CLF-CBF-QP) is designed to suppress the disturbances, ensuring the safety and stability of the nonlinear system. Finally, a numerical simulation is conducted to validate the effectiveness of the proposed method through comparisons with existing approaches.