Nonlinear model predictive control for trajectory tracking and collision avoidance of surface vessels
This thesis presents a combined Nonlinear Model Predictive Control for trajectory tracking of surface vessels, and collision avoidance into a single control scheme. This scheme is suitable for critical maneuvering of autonomous vessels in near collision situation due to the explicit utilization of the dynamic model and the ship domain in the design. A nonlinear optimization problem is formulated to minimize the deviation of the vessel states from a time varying reference generated over a finite horizon by a virtual vessel with sideslip angle compensation. Collision avoidance is embedded into the trajectory tracking control problem as a time varying nonlinear constraint of position states to account for static and dynamic obstacles. The ship domain of the vessel is assumed to be either circular or elliptical disk. The effectiveness of the presented approaches are evaluated using MATLAB and ACADO toolkit for automatic control and dynamic optimization.