A distributed anti-collision decision support formulation in multi-ship encounter situations under COLREGs

A multi-ship anti-collision decision support formulation is studied in a distributed and real time way. Under the general requirements from COLREGs rules and regulations, the performance of course alteration and changing speed in collision avoidance in some typical encounter situations is graphically analysed for both give-way and stand-on ships. Based on the analysis, the initial decision on collision avoidance by course alteration or speed changing is made according to the encounter situation between own ship and target ships. Linear extension algorithms are designed for both course alteration and speed reduction to keep clearance of all the target ships that own ship should avoid. Simulation results indicate that the anti-collision formulation can avoid collision when all ships have complied with COLREGs as well as when some of them do not take actions. The results also show that in multi-ship encounter situations, the violation of COLREGs by one ship can sometimes bring more difficulties to other ships to avoid collision while undesirable manoeuvre actions have to be taken.