Ship Fin Stabilizer Nonlinear Control Based On Closed-loop Shaping Filter

While sailing in unknown and complex ocean environment,the ship will shake due to the influence of external disturbances such as waves and wind.In particular,rolling motion has the greatest impact on the safety of the ship.Considering the uncertain parameters perturbations of ship roll motion model and external interference of sea waves,a ship fin stabilizer L₂ gain robust control scheme based on closed-loop shaping filter was proposed in this paper,so as to reduce the ship roll amplitude and guarantee the safety of navigation.First of all,the nonlinear mathematical model of the ship fin stabilizer system is analyzed in this paper.Then the L₂ gain robust control scheme based on the time domain control theory is used to design the ship fin stabilizer controller.While the concept of closed-loop shaping filtering based on the frequency domain control theory is introduced to define the filtering error signal.Furthermore,the effective compensation control of the uncertain parameters of the system model is realized,and the combination of frequency domain controller design and time domain controller design is implemented.Moreover,the Lyapunov stability theory is used in the whole controller design process to guarantee the stability of the designed controller.Then,the motor vessel YUKUN was used as the numeric simulation control plant and the nonlinear characteristics of the vessel YUKUN roll motion were analyzed.Also improved JONSWAP wave frequency spectrum and sea wave direction function were used to simulate the multi-directional irregular waves,and the comparison experiment was carried out under the condition of regular wave and multi-directional irregular wave to verify the performance of the fin stabilizer scheme.Subsequently,half-speed simulation experiments were used to verify the stability and robustness of the designed controller.Finally,a small intelligent ship fin stabilization experiments was conducted to verify the controller design method proposed in this paper.Firstly,the free roll decay experiment in calm water was carried out,and the least square method was used to identify the coefficients of the damping terms and the restoring moment terms of the small intelligent ship nonlinear roll motion equation.Then with the utilization of the rolling motion model identification results,the fin stabilizer controller for the small intelligent ship was designed based on the proposed control scheme in this paper.Then the fin roll stabilization test with the small intelligent ship autonomous navigation situation proved the effectiveness and feasibility of the controller designed in this paper.The experimental results show that the proposed fin stabilizer controller has the advantages of concise structure,distinctive meaning of tuning parameter,easy implementation,strong robustness and good control performance.The design scheme and controller structure of the ship fin stabilizer controller can be simplified with the consideration of the system robustness and control performance,so that it can be better applied to ship engineering practice.