Specified-performance active disturbance rejection control for position stabilization of the tip of gangways

Abstract

In the presence of uncertain dynamics, uncertain wave-induced vessel motion disturbances, and uncertain mechanical friction, a position stabilization control scheme with specified performance is proposed for the tip of the gangway (ToG) to achieve wave-induced vessel motion compensation in this article. Based on a barrier function, a specified-time extended state observer (STESO) is innovatively constructed, which, in a specified settling time, provides the estimates of the total disturbances lumped by uncertain dynamics, uncertain wave-induced vessel motion disturbances, and uncertain mechanical friction. Further, based on the constructed STESO and another barrier function, an active disturbance rejection control law with specified performance for the position stabilization of the ToG is created such that the position stabilization errors of the ToG reach and stay within the specified tolerance error bands in the specified settling times. Therein, it is solved that in the existing literature, the bandwidth of the prescribed-time extended state observer or controller will approach infinity when the time approaches the specified settling time. This is because our properly designed envelops of the ToG position estimation errors of STESO and the ToG position stabilization errors guarantee that the bandwidths of the STESO and the controller are bounded. Simulation results with comparisons show the effectiveness and the superiority of the proposed control scheme.