The Design Of Ship Attitude Motion Control Platform

Ship sailing in the sea, is bound to the ocean waves and other environmental factors and result swaying motion in the process of moving ship. Of course, a lot of swaying motion will have a negative impact on safe driving. How to maintain the stability of the process of moving ship, is becoming increasingly important. In order to study the attitude motion of ships on the effect of the disturbance waves, we design a motion device which can simulate the ship motion and wave disturbance under laboratory conditions, called the ship attitude motion control platform.Ship attitude motion control platform is a semi-physical simulation experimental device, it consist of a three dimensional structure of rotating machinery testing, two model computers, a hydraulic mechanism and some sensors witch can measure azimuth and angle. Ship control platform can simulate the rotation movement of ship and waves in the three directions, including yaw, roll and pitch. The ship layer of control is under the layer of the ship. Rotary motion of the wave has effect on the ship with disturbance. Ship attitude motion control platform could reflect the actual operation of ship attitude motion state and the results is more convincing.The main work of this paper is to complete the ship layer of the control platform, under the action of random disturbance in the waves, the ship closed-loop system can restrain the influence of the waves to run in according with the setting posture. First of all, the basic composition and working principle of ship control platform is introduced; secondly, we establish the wave random disturbance torque and responsiveness mathematical model of the ship; Finally, we input random disturbance by wave model computer and set status information by ship model computer, the ship attitude information feedback to the ship model computer by the sensor, then the controller sends out control instructions to restrain disturbance and make the ship to run in accordance with the reservation set attitude operation.The ship attitude control selects the closed-loop control for PID control at the beginning; Because of pure time delay, the system easily produces overshoot or oscillation, so we use the Smith prediction control combined with PID control. Through the control platform to verify the two algorithms and compared the control performance. The result shows that we can get better system performance after joining Smith prediction control.