Experimental Study on Pitching Motion Mode of a SWATH-USV

Abstract

The importance of the research about ship motion model has become more prominent with the improvement of economic level. Mastering ship motion model is a necessary basis for studying ship's divisibility. The hydrodynamic parameters obtained by parameter identification methods are more precise, which is dissimilar from the parameters obtained by classical methods. In this paper, a SWATH-USV was taken as the research object to accomplish a series of pitch decay tests on the condition that the SWATH-USV was in different drafts and tilts angles in the hydrostatic state. And a mathematical model by the method of system identification based on genetic algorithms has been established, adopting VB language to program a systematic identification software. With this, the author obtained the pitch motion differential equations, and the changing regularities of hydrodynamic coefficients with draft and initial tilt angle of the model in different drafts and initial tilt angles and their kinematic equation. Using this equation to predict, the results are proved to be well matched with the experimental results. And the feasibility of the identification method is also confirmed. The analysis results and methods can provide essential technical support for the in-depth analysis of the wave resistance and the design of the boat.