Techno Press
Techno Press

Structural Engineering and Mechanics   Volume 30, Number 6, December20 2008, pages 679-698
DOI: http://dx.doi.org/10.12989/sem.2008.30.6.679
 
Semi-active control of ship mast vibrations using magneto-rheological dampers
Y.S. Cheng, F.T.K. Au and J.P. Zhong

 
Abstract     [Full Text]
    On marine vessels, delicate instruments such as navigation radars are normally mounted on ship masts. However the vibrations at the top of mast where the radar is mounted often cause serious deterioration in radar-tracking resolution. The most serious problem is caused by the rotational vibrations at the top of mast that may be due to wind loading, inertial loading from ship rolling and base excitations
induced by the running propeller. This paper presents a method of semi-active vibration control using magneto-rheological (MR) dampers to reduce the rotational vibration of the mast. In the study, the
classical optimal control algorithm, the independent modal space control algorithm and the double input-single output fuzzy control algorithm are employed for the vibration control. As the phenomenological
model of an MR damper is highly nonlinear, which is difficult to analyse, a back-propagation neural network is trained to emulate the inverse dynamic characteristics of the MR damper in the analysis. The
trained neural network gives the required voltage for each MR damper based on the displacement, velocity and control force of the MR damper quickly. Numerical simulations show that the proposed control methods can effectively suppress the rotational vibrations at the top of mast.
 
Key Words
    magneto-rheological damper; neural network; semi-active control; ship mast; structural vibration.
 
Address
Y.S. Cheng: Dept. of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China
F.T.K. Au: Dept. of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
J.P. Zhong: Dept. of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China
 

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