Continuous Sliding-Mode Control for a Class of Underactuated Systems Subject to Disturbances and Uncertainties

This brief focuses on the control problem of underactuated systems, which have fewer control inputs than states to be controlled and have gained widespread usage in practice in recent years. To overcome the underactuated characteristics, a new actuated state is designed to transform the underactuated dynamic model into an actuated form. The total disturbance of the proposed model is then estimated by the linear extended state observer (LESO). With the estimated total disturbance, a sliding mode control (SMC) strategy is proposed based on disturbance compensation. A control law is designed to guarantee the smoothness of the control inputs and the asymptotic stability of the system. Moreover, simulation and experimental results for the rotational-translational actuator (RTAC) are provided to demonstrate the effectiveness of the proposed method. Comparisons with existing methods indicate that the proposed controller can achieve better performance and robustness.