| The vessel is mainly affected by the propeller, main engine, wave and wind force. In this environment, harmful vibration will occur easily, and it will affect the invisibility, safety and comfortableness of the vessel. So, it is very significant to research on the active vibration of ship structures. In this paper, the active vibration control is researched for beam or plate which is the basic component in ship.The finite element model of the 4-node quadrilateral piezoelectric composite structure is developed based on the Mindlin bending theory and Hamilton's principle, considering the electric and mechanical properties. An Independent Modal Space Control (IMSC) technique based on Linear Quadratic Regulator (LQR) method is adopted to carry out the active vibration control of piezoelectric smart structures, control equation in state space is derived and the High Precise Direct (HPD) integration method is used to calculate the response of the structure's controlled modal before and after control. The corresponding programs are composed in FORTRAN. Active vibration control for a discontinuous distributed piezoelectric cantilever, which is subjected to harmonic and the vessel's vibration signal excitation, is used in simulation examples, the vibration of the cantilever is suppressed effectively, and the method in this paper is verified to be effective. For the situation that piezoelectric patches are laid discretely, taking the control method into account, Linear Quadratic Regulator performance index is used as optimal criteria, and adaptive evolutionary strategy method is adopted as optimal algorithm. Combining optimal theory with finite element theory together, the corresponding program is composed. The optimal example result shows that the control effect of optimal placement is better than the control effect of discontinuous distributed placement. The researches in this paper provide a theoretical basis for active vibration control of vessel structure. |
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