Finite-time extended state observer-based robust control approach of RTG cranes

In this paper, a robust control method based on finite-time extended state observer is developed for the rubber-tired gantry crane under the influence of wind disturbance. Firstly, an extended state observer is proposed to estimate not only the wind disturbance from the marine environment but also to observe the velocity to address the difficulty in sensor installation. The settling time of the observer is analyzed and calculated to serve as the basis for evaluating the stability of the whole control system. Subsequently, a hierarchical sliding mode controller is presented based on the observer's estimation results. The stability of the control system is demonstrated using the Lyapunov’s stability theory to ensure that the estimated error converges to a bounded domain and the state error converges to zero. Finally, the effectiveness of the proposed method is validated through numerical simulations and compared with a standard sliding mode controller in the case of wind disturbance.