Parameter identification of a compliant nonlinear SDOF system in random ocean waves by reverse MISO method

The determination of the drag and inertia coefficients, which enter into th e wave force model given by Morison's equation, is particularly uncertain a nd difficult when a linear spectral model is used for ocean waves, and the structure is compliant and has nonlinear dynamic response. In this paper, a nonlinear System Identification method, called Reverse Multiple Inputs-Sin gle Output (R-MISO) is applied to identify the hydrodynamic coefficients as well as the nonlinear stiffness parameter for a compliant single-degree-of -freedom system. Four different types of problems have been identified for use in various situations and the R-MISO has been applied to all of them. O ne of the problems requires iterative solution strategy to identify the par ameters. The method has been found to be efficient in predicting the parame ters with reasonable accuracy and has the potential for use in the laborato ry experiments on compliant nonlinear offshore systems. (C) 2001 Elsevier S cience Ltd. All rights reserved.