Prediction of the hydrodynamic parameters in the coupled heave and pitch motion equations for underwater robotic vehicles using measured responses atsea

A method for the identification of the damping, restoring, and coupling par ameters in the equations describing the coupled heave and pitch motions for an underwater robotic vehicle (URV) sailing near sea surface in random wav es rising only its' measured responses at sea is presented, The random decr ement equations are derived for the URV performing coupled heave and pitch motions in random waves. The hydrodynamic parameters in these equations are identified using a new identification technique called RDLRNNT which uses a combination of a multiple linear regression algorithm and a neural networ ks technique. The combination of the classical parametric identification te chniques and the neural networks technique provides robust results and does not require a large amount of computer time. The developed identification technique would be particularly useful in identifying the parameters for bo th moderately and lightly damped motions tinder the action of unknown excit ations effected by a realistic sea. Numerically generated data for the coup led heave and pitch motion of a URV are used initially to test the accuracy of the technique. Experimental data are also used to validate the identifi cation technique. It is shown that the developed technique is reliable in t he identification of the parameters in the equations describing the coupled heave and pitch motions for an URV.