We propose a new reasoning method of crankshaft and propulsion shaft static alignment under any vessel condition. There are two measurement methods for alignment. One is called crankshaft deflection method. The other is bearing load method. Those methods do not lead directly to shaft alignment. It is necessary to solve the heights of each bearing by an inverse solution. Firstly, Crankshaft of n-cylinder engine and propulsion shaft is modeled simply in order to calculate the crankshaft deflections and the bearing loads. The model is solved by using transfer matrix method. Secondly to solve the inverse problem, the bargaining game theory is applied. In the game, each bearing height is defined as player. The utility function is defined as the error function as compared with the measured results. The solution of the game is the maximum of the multiplication of utility values based on Nash bargaining solution. Genetic algorithm is used to calculate the solution. As the results, to apply on some actual vessel data, newly developed method is effective to reason the bearing height.
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