Identification of hydrodynamic coefficients of a ship manoeuvring model based on PRBS input

A new method is proposed to obtain accurate hydrodynamic coefficients of 3-DOF ship models. This method includes two parts: identification algorithm and identification input design. Firstly, the manoeuvring modeling group model of an underactuated ship is introduced. Secondly, the nonlinear model of the ship is converted into a linear form by using the X-swapping technique. An on-line identification law, which is introduced for identification under relaxed excitation conditions, is used to estimate the unknown hydrodynamic coefficients of the ship dynamic model. Thirdly, two Pseudo-Random Binary Sequence signals are chosen as the identification inputs to excite the rudder and the propeller, which can improve identification performance. Finally, a simulation example is put forward to demonstrate the effectiveness of the proposed identification method. •A MMG model of an underactuated ship is established for identification.•A least-squares based identification algorithm for relaxed excitation condition is introduced.•PRBS signal is used to optimize the identification input.•Comparisons are carried out to show the superiority of the proposed method.