Automatic Collision Avoidance Manoeuvres for Surface Ships

This paper discusses a method to transfer the conventional nautical approach to plan and execute collision avoidance (CA) manoeuvres for surface vessels into an automatic operation. The method requires a digital manoeuvre plan or rather the planned route berth to berth based on specific dynamic motion model of the vessel. The automatic operations are systematically processed by a supervisor module combined with a generic structure for guidance, navigation and control. In a dangerous encounter situation, new way and manoeuvre points of the evasive manoeuvre are calculated automatically depending on given parameters of captain's order, collision avoidance regulations at sea as well as specific ship characteristics. The new plan is used in a feedforward control system which bases on inverted straightforwardly structured, control-oriented model. The feedback controller minimizes the differences to the target route because of model uncertainties and disturbances in the environment. A line-of-sight based guidance algorithm continuously calculates a commanded course over ground, which is used by a heading controller. The algorithms are validated in ship handling simulator trials.