Study On Control System Of Fin Stabilizer Base On Wave Spectrum

Ocean plays an important role in human's survival and development. With the exploration of oceanresources, more and more ships sail on the ocean to complete different missions.Ocean waves causes extremely large disturbance on the ships such as swaying in different directions, among which roll motion is one of the most severe motions having serious impact on the life and safety of ships, comfort of staff and normal use of ship equipments. At present, fin stabilizer is the best active stabilization devices with the rolling effect up to 90%. Besides, research on control system of fin stabilizer also canrries great importance.This thesis focuses on two factors. Firstly, wave signal haven't been fully utilized by traditional fin stabilizer control system; Secondly, PID control system of traditional fin stabilizer based on torque against principle doesn't work well in complex situations, the main work is to improve these two aspects. First, spectrum estimation methods was employed to estimate sway spectrum when ship is swaying, and then current power spectrum and the wave directional spectrum was ani-launched. This method does not require any special equipment, instead accurate wave spectrum can be obtained only by simple mathematical caculation. The simulation proved that the wave spectrum method was quite accurate.As for the control methods, compared with the traditional control theory, intelligent control has been well recognized in dealing with complex environments. Neural network control has enjoyed good learning abilities, but difficult to express the input and output; while the expression of fuzzy control is easy to accept with weak learning capabilities. Thus, strengths of both neural networks and fuzzy control were utilized to form a new intelligent control technology, with which fuzzy neural control system of fin stabilizer was designed. Wave-class regulator was redesigned with wave spectrum and fuzzy control technology. Significant wave height extracted from wave spectrum was used as input signal to control its output, making wave signal to be more fully utilized.In order to verify the rolling effect of designed wave-class regulator and intelligent control system compared with the traditional PID control system, ship control system model was set up to simulate the rolling effects under different sea conditions and ship speed. It is shown that fuzzy neural control system is better than the traditional rolling PID controller.