추사파중에서 자동조타로써 항행하는 선박의 추진에너지 손실량 평가에 관한 연구

A Study on Prediction of Propulsive Energy Loss Related to Automatic Steering of Ships in Following Seas

When an automatic course-keeping is concerned, as is quite popular in modern navigation, the closed-loop steering system consists of autopilot device, power unit (or telemotor unit), steering gear, magnetic or gyro compass and ship dynamics. The considerations of irregular disturbances to ship dynamics and a few non-linear mechanisms involved in the system inevitably or artificially, are known to be very important in properly evaluating or analyzing the automatic steering system. In the present study, the mathematical model of each element of an automatic steering system is derived, which takes account of a few non-linear mechanisms. PD (Proportional-Derivative) controller and low-pass filter with a weather adjustment are adopted to modelling the characteristics of an autopilot. The calculation method of imposing irregular disturbances to ship dynamics is proposed, where irregular disturbances implying irregular wave and the fluctuating component of wind. For the evaluation of automatic steering system of ships in the open seas, an important term, "performance index", is introduced from the viewpoint of energy saving, Which derived from the concept of energy loss on ship propulsion. Finally, the present methods are applied to two typical types of ship ; an ore carrier and a fishing boat. The various effects of linear and/or non-linear control constants of autopilot on propulsive energy loss are investigated to validate and clarify the present simulation technique.