Observer-based motion control system for the approach ship with propeller and rudder in the process of underway replenishment

Abstract

To avoid collisions between guide ship and approach ship during the underway replenishment process, it is important to maintain a certain distance between them. Based on trajectory tracking requirements, a control strategy suitable for engineering applications is proposed for an approach ship without velocity measurements. First, considering the effects of wind, waves, currents, hydrodynamic interactions and the highline cable system, models are established for the two ships. Second, a leader-follower approach is used to maintain the expected longitudinal and transverse distances between the two ships. Third, an extended state observer is designed according to the position, heading, propeller speed and rudder angle of the approach ship. Two time-varying parameters in the observer are estimated in the controller design process. Therefore, the linear speeds, yaw rate, and total system uncertainties can be observed. Fourth, the propeller speed and rudder angle, other than the surge force and steering moment, are considered as the control inputs, which are constructed by the command filter backstepping method. The stability of the proposed control system is verified. Finally, a simulation is performed to demonstrate the effectiveness of the proposed method.