# Research on a Support System for Automatic Ship Navigation in Fairway
## 1 Introduction  
Marine navigation plays an important role in maritime transportation and sea environment protection. To ensure ships' operation safely and effectively from berth to berth, modern equipment has been produced to assist the deck officers in ship control and maneuvering. In fact, the ship navigation process includes three stages. First, the ship is navigated by autopilot to keep the ship heading on the desired course, and the autopilot is usually adjusted manually to track the planned route; this stage is conducted in open sea at the full speed of the main engine and is subject to an insignificant effect of waves. Second, the ship is controlled by the helmsmen in the fairway of the port area to continue on the planned track. In this stage, the ship's speed is decreased at an appropriate time so that the ship is led to a certain area. In the last step of this stage, the ship heading is brought into the desired one before performing the berthing process. Finally, the ship is maneuvered into the berth by changing the rudder angle and propeller revolution simultaneously. In the second and third stages, the control process for ship navigation is fully operated by the navigators. With the development of a global economy, new requirements have been introduced into shipping transport, such as the optimization of the amount of crew on board, energy saving, and cost reductions in ship operation. For that purpose, the automation of ship operation is a feasible solution to reduce the amount of crew and operation cost. To date, many reports have been undertaken regarding the automation of the issues of ship motion control, such as ship course keeping, track-keeping, automatic berthing, automatic collision avoidance, and so on. This research is seen as the basis for automatic machines and systems in the real world for maritime applications. The first automatic steering mechanism for ships was introduced by [PERSON] in 1911 [1], and the proportional-integral-derivative (PID)-based autopilot was constructed in 1922 by [PERSON] [2]. The task of this autopilot is the course-keeping control of ships. To enhance the performance of this function, different theories of control engineering were proposed, such as artificial neural networks, fuzzy logic, the back-stepping algorithm, sliding mode control, adaptive control, optimal control, and so on. However, these course-keeping systems have no ability to track a predetermined route, especially under strong external disturbance. In fact, navigators have to set a new course for the autopilot manually rather than automatically. To obtain the track-keeping ability from the course-keeping function for ship control systems, the drift distance determined from the ship to the route needs to be described when designing the controller. In addition, this function was also developed for unmanned surface vehicles. However, when designing the controller, these control systems either simplified ship dynamic models or considered the ship speed as a constant value. Therefore, these systems are only employed to follow a ship's route in open sea, and they have difficulty in satisfying the demand of track-keeping systems of ships in maritime practice when ships navigate in a fairway area. On the other hand, since the ship motion is complex at low speed, the berthing control system needs exact controllers to regulate the rudder and propeller simultaneously. To assist the ship in maneuvering processes at low speed, auxiliary devices, such as bow thrusters and azimuth propellers are installed in ships to increase their maneuverability. As summarized above, there are two main systems proposed to navigate the ship automatically; these are the track-keeping control system of a ship in the open sea and the automatic berthing system of the ship. The ship's speeds in the automatic berthing system are absolutely different to those in the track-keeping system in the open sea.