||Dr. Ognjen Kuljaca, Department of Advanced Technologies Assistant Professor and Systems Research Institute researcher published as a coauthor a journal paper titled “Nonlinear Resonant Jump in Rudder Positioning Electrohydraulic Systems”. Authors of this original scientific paper are Dr. Krunoslav Horvat from Control Systems Department, Brodarski Institute, Croatia, Dr. Ognjen Kuljaca and Dr. Vladimir Koroman, CEO of Brodarski Institute and Professor at Faculty of Mechanical Engineering and Naval Architecture of University of Zagreb, Croatia.
Paper went through peer review and after acceptance was published in journal Shipbuilding, in June 2008 issue, Vol. 59, No. 2, ISSN O007-215X. Older issues of the journal can be viewed free of charge at
http://www.hrbi.hr/brodogradnja/index_eng.php. Shipbuilding is referenced in following databases: BMT Abstracts, Marine Technology Abstracts, VINITI Abstracts Journal, EI Compendex, MEchanicla Engineering Abstracts, World Translation Index, and Fluidex.
Published research was in part supported by funds from Crossing Borders grant from the Unity through Knowledge Fund, awarded, project “Applied neuro-fuzzy control of turbine governors and ship rudder systems”.
Paper deals with phenomenon of nonlinear resonance jumps in rudder systems. The rudder positioning electrohydraulic system, as many other complex systems, is a nonlinear system. In nonlinear systems, a nonlinear resonant jump can occur. The paper deals with the analysis of the rudder positioning electrohydraulic system regarding the nonlinear resonant jump caused by saturation of the electrohydraulic proportional valve. The meaning of the term "resonant jump" is explained in the introduction. Then, the basics needs for occurrence of nonlinear resonant jump phenomenon are given. The rudder positioning electrohydraulic system is also described. Two methods of analyzing system with respect to resonant jumps are described: the analytical method and the simulation method. When performing the analytical analysis based on the describing function approach, the analysis of the variations of important parameters, including saturation, is performed. Then, the confirmation of the results of analytical analysis is illustrated by the simulation method. Also, the simulation procedures, like creating an excitation signal and accelerating the simulation by using vectors in Simulink/Matlab simulation software package, are explained in detail.