Nonlinear Modeling And Simulation Of Azimuth Tugboat

In order to predict the motion of the azimuth tugboat for its operators, and decrease or avoid the port operation incidents, the research works about azimuth tugboat's motion are very important. Therefore, this article tries to suggest a model suited for the azimuth tugboat.Firstly, taking into account for the importance of the rolling movement in azimuth tugboat's actual movement, this paper builds up a four degree-of-freedom mathematical model including the plane motion and the coupling rolling motion. And the azimuth tugboat is bound to drift across the condition of the low speed and large drift angle, so this article provides a math model which combined the Kijima model and Yoshimura model. The mixed model was suitable for the entire maneuvering range including normal speed, low speed, small or large drift angle and so on.Secondly, to meet the demand of the azimuth tugboat multi-state dynamic simulation, this paper proposed a method for calculating the thrust and torque coefficients of the ducted propeller. And the above mentioned coefficients can be calculated directly by computer according to the ducted propeller principal particulars.Finally, in order to validate the model suggested by this article was correct and effective, this paper developed a simulation platform for the azimuth tugboat's manipulation motion by Visual Basic. The realistic simulations of the azimuth tugboat's typical movement including turning ability, swaying ability were made. Among the simulations, the effects of wind and current were taken into account for the sake of reality. The results were satisfactory by comparing with ship trails and testified the correction and validation of the model. Hence this model can be used for calculation and prediction of azimuth tugboat's maneuverability.