Estimation of Ship Hydrodynamic Coefficients at Low Speed Range and Application to Control Ships

抄録

This paper presents results of hydrodynamic coefficient estimation of a VLCC model at low speed range by free-running method and application to ship control. Various kinds of manoeuvring motions such as drifting, turning were performed in the tank by use of air propeller systems of 3 sets. To achieve high accuracy of ship position measurement, a remote position sensing system was developed and utilized. A multi-terms mathematical model describing forces and moment acting on a hull was adopted to express ship motions so that the mathematical model could cover a wide range of ship manoeuvres. In the present study, many coefficients of the model, so-called the hydrodynamic coefficients were identified from these free-running tests. Basically, the ship hydrodynamic coefficients were estimated using the Least Square (LS) Method but the Extended Kalman Filter was also applied for achieving high accuracy of added mass estimation. The coefficients were successfully estimated by the present procedures. Simulations of the free-running tests were carried out and good agreement was found between observed and simulated motions. The mathematical model of manoeuvring motions in low speed was used as an application of the model for simulating the manoeuvring motions in harbour under strong wind. A simple control law was applied for keeping ship longitudinal speed zero. The result shows us that drifting performance induced by wind can be improved remarkably by the simple control law.