Estimation of Roll Motion Parameters using R-MISO System Identification Technique

摘要

While the heave and pitch motions of a ship follow a fairly linear behavior,the roll motion exhibits a strong nonlinear behavior due to the presenceof viscous damping and nonlinear stiffness. It exhibits complicateddynamics and hence is studied in much more detail as compared to otherseakeeping modes. One of the important tasks before analyzing the rollmotion of a ship is to get accurate estimates of these nonlinear parametersgoverning the dynamics. One of the easiest approach is to identifythe parameters (such as damping and nonlinear stiffness) using experimentaldata and is known as system identification. Although there are alot of system identification techniques available, in this paper we restrictourselves to one of the popular technique known as the Reverse-MultipleInput Single Output (R-MISO) method. While this method has extensivelybeen applied to obtain accurate predictions of heave and pitch hydrodynamicparameters, its applicability to the more sensitive roll motionhas not received enough attention. This paper investigates the applicabilityof the R-MISO technique to accurately predict the parameters of thenonlinear roll motion of a ship. We specifically apply this technique tosimulated data to later verify that the predicted parameters indeed matchthe values used in the simulations. While the results demonstrate the robustnessof the method and its applicability to the extremely sensitive rollmotion, the paper also discusses a few limitations of the approach.