Research On Dynamic Hydrodynamic Model And Electro-servo System Of Fin Stabilizers

Fin stabilizer is one of the most effective ship roll reducing equipments, which detects the roll angle through the sensors, converts it into fin-angle information, then drives the fins by electro-hydraulic servo system. With the control system, it will produce lift that comes into being torque to counteract the wave's interfering torque. But it still has some defects because there are many uncertain factors in the ship motions. Sometimes the uncertain is considerable and leave much error to be desired performance..In this dissertation the difference between linear model and nonlinear model of the ship roll the applicability of the ship roll linear model and nonlinear model are studied. And getting the conclusion which the factor of nonlinear damp has more effect than the factor of nonlinear comeback torque in the nonlinear model of ship roll. Based on MATLAB simulation, it proved that the nonlinear model without 5-th power function term is used instead of the nonlinear model , can simplify the nonlinear model and reduce the calculation.The mapping of fin-angle/lift fin-angle/torque in the fin stabilizers dynamic hydrodynamic model is studied. Based on towing tank test data of fin model and the Theodorsen theory, the mapping of fin-angle/lift fin-angle/torque in the fin stabilizers dynamic hydrodynamic model is presented. Using the fin dynamic hydrodynamic model, the dynamic feedback lift and torque are obtained and used as the feedback information in ship stabilizer control systems. So that it will avoid the uncertain caused by the mapping of fin-angle/lift.Base on DTC control technology of asynchronism electromotor, the structureand control law of fin stabilizer electro-servo systems are studied.. The proposal of replacing electro-hydraulic servo system by asynchronism electromotor electro-servo system is presented. Engineering application Feasibility of asynchronism electromotor servosystem are proved by simulating and some laboratory tests. Hardware circuits and software programming of the asynchronism electromotor servo system are designed.A single nerve centre controller is proposed to improve the used PID controller. A new performance index of Pe2 (k + d) + Qâ–³u2 (k) is applied in thefin stabilizer control system using the single nerve centre controller. The ship roll motions without stabilization, with fin stabilizer of used PID controller and single nerve centre controller fin stabilizer are studied for different sea states. The simulation results of single nerve centre PID controller is better than other two controllers. And the fin stabilizer of single nerve centre PID controller in ship fin stabilizers.