Abstract
Autonomous shipping refers to the ability of a ship to independently control its own actions while transporting cargo from one port to another, which places higher requirements on ship motion control methods. When a ship enters a port, it is important to ensure that the ship sails from the fairway area to the assigned position at the berth with a desirable speed and that it finally stops at the desired position. Ship docking is known as one of the most challenging tasks due to the non-linearity of low-speed ship movements and the high requirements on collision avoidance with the quayside. This paper proposes a nonlinear model predictive control (NMPC) -based approach for underactuated ships, providing optimal ship rudder angles and propeller revolution rate to automate the ship docking process. At each sampling instant, a finite horizon optimal control problem is formulated based on a nonlinear ship maneuverability model. A lexicographic multi-objective optimization strategy is proposed in the design of the NMPC controller, saving the efforts on control parameters tuning. Simulation experiments are carried out to evaluate the effectiveness of the proposed approach.
Highlights
With the trends towards autonomous shipping, advanced ship motion control techniques are being developed to ensure that ships can independently control their own actions, especially in complicated situations
When a ship is moving at a low speed, the ship maneuverability reduces, which makes it difficult to steer the ship in a flexible way
The nonlinear model predictive control (NMPC) controller is implemented with MATLAB Model Predictive Control Toolbox
Summary
With the trends towards autonomous shipping, advanced ship motion control techniques are being developed to ensure that ships can independently control their own actions, especially in complicated situations. When a ship enters a port, it is important to ensure that the ship sails from the fairway area to the assigned position at the berth with a desirable speed and that it stops at the desired position. Is reduced due to the low speed, which makes it difficult to maneuver the ship with rudder; thirdly, the main engine is stopped at the appropriate time, and the ship moves to the berth with the remaining speed. A ship docking procedure includes course changing, speed deceleration, and engine stopping. As well as to contribute to the development of smart ships and autonomous shipping, automatic ship docking techniques are required. When a ship is moving at a low speed, the ship maneuverability reduces, which makes it difficult to steer the ship in a flexible way. Most marine ships are under-actuated systems, only the yaw and surge movements
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