Variable structure control based on grey prediction for ship fin stabilizer

Ship fin stabilizer is widely employed in reducing rolling motion. But the effectiveness of ship fin stabilizer can be severely deteriorated due to the nonlinear and uncertainty arising from ship parameter variations, unsteady hydrodynamic characteristics, and waves. Variable structure control can offer several desirable characteristics, such as fast dynamic response, insensitivity to parameter variations, and rejection to external disturbances. However, common variable structure controllers require not only the bound value of uncertainty be known in advance but also the existence of chattering, especially to discrete system. The grey prediction method requires only a few sampled data to develop the grey model and to forecast on future. In this paper, an improved reaching law and an improved grey prediction method are employed to enhance performance and reduce chattering.