For rudder angle servo mechanism in steer-by-wire (SBW) system of pleasure boats, this paper presents a sliding mode controller with continuous control input. The sliding mode control theory is applied to the controller so as to have high robustness against the normal pressure of a rudder, which is regarded as an unknown disturbance. Designed with the twisting algorithm and the describing function method, a switching input of the proposed controller could enforce a switching function into a limit cycle. As a price of abandoning the perfect sliding mode, the proposed controller can bring not infinite-frequency switching input but continuous control input. As a result, the improvement of the load of the actuator in SBW system can be achieved.

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The paper presents a method to get better maneuverability by improving steering feelings so that inexperienced captains can smoothly control pleasure boats in critical situation for collision avoidance. To achieve this aim, firstly in order to show how much difficult it can be to control the boats; the complicated dynamics of them are evaluated by using a developed simulator including a steering system with simulation software. Then, it is considered to vary whole rotation angles and to give a virtual reaction torque on a helm. The results show that it may be able to navigate stably and reduce the meanders if the reaction torque is appropriately supplied and the whole rotation angle on the helm is suitably determined for inexperienced captains.

As AIS receiver can acquire ship − moving inforIIlation on land ， it is expected as a new device of a marine traf丑c investigation ． This paper describes the systeln 七hat does the safety evalllation in real time in the marine tra田c continuously receiving ship −moving hユformation by the AIS receiver ， and using Environmental Stress model (ES model) ， which can evaluate ship − handling difficulty ．