STATE-SPACE MODELLING OF DYNAMIC SYSTEMS IN OCEAN ENGINEERING

Pertaining to dynamic systems in general,a review is given of relations between mathematical descriptions in the frequency domain or time domain and state-space descriptions.For the analysis of hydrodynamic problems in ocean engineering wave forces may be represented by convolution integrals.The paper presents a method to construct a finite-order state-space model which represents a good approximation to such a convolution integral.The method utilizes a particular algorithm to compute the partial derivative of the exponential function of a(state-space)matrix with respect to the matrix elements.The method is applied to an example of fitting a state space model of order five to the free oscillations corresponding to wave radiation in a transient experiment with an oscillating water column.