Automatic track keeping to realize the realistic operation of a ship

This paper introduces an automatic track keeping algorithm consisted of two systems, which are a waypoints switching system and a rudder control system. Fuzzy inference based on human manipulation experiences is applied to the both system to realize the actual ship operation. In the waypoints switching system, a course change angle is reflected as input data to find out optimal point at where rudder is used. The obtained optimal point allows the ship to follow a route accurately without overshoots such as cross track error and heading error. Heading error, cross track error and difference between current yaw rate and desired yaw rate are considered to control rudder appropriately. The desired yaw rate is derived using the heading error and the cross track error, and suitable rudder angle is inferred by comparing current yaw rate with the desired yaw rate. Numerical simulations were carried out to verify the effectiveness of the proposed algorithm. Instead of evaluating the algorithm under virtual environment with geometrical route and assumed external disturbance, scenarios for simulations were created by utilizing route plans used in actual operations. Actual conditions of wind and current at sea were applied to prove capability in the real world situation. It was observed by the simulation results that a ship traveled on a pre-planned path defined in a route plan and overshoots hardly occurred. It can be said that the algorithm has sufficient performance for ship track keeping.