Research On Control Of Winch Heave Compensation System Based On Platform Motion Prediction

Heave compensation system is one of the essential equipment for floating operation of offshore floating operation platform(such as drilling platform,wind power installation ship and CTV ship).Winch heave compensation system is a new type of heave compensation system with great research significance and application prospect because of its special advantages such as small occupation of platform operation space and unlimited compensation stroke.The previous research work shows that the designed compensation winch can achieve the expected compensation function,but the compensation accuracy needs to be further improved.Considering the large inertia of the power mechanism of the compensation winch and the lag of control response,if the platform heave speed can be accurately predicted in a short time,the compensation control signal can be sent in advance to realize the synchronous compensation of disturbance,the compensation accuracy of the system can be greatly improved and the operation safety can be increased.Taking the energy-saving winch heave compensation system suitable for the actual working conditions and the laboratory heave compensation simulation test-bed as the application object,this thesis studies the practical prediction method of the heave motion speed of the floating platform.Aiming at improving the compensation accuracy of the compensation system,the following research work is done:(1)Analyse the influence of ocean wave disturbance on offshore floating platform,use ITTC dual parameter spectrum to obtain the wave spectrum under level 5,6 and 7 sea conditions,and simulate the displacement and velocity data of wave and floating platform under different levels of sea conditions according to the transmission relationship between floating platform and wave;(2)Explain the construction principle and process of wavelet neural network prediction model.With the floating platform heave velocity data as the source data,the current and the first three prediction periods as the model input values,and the platform heave velocity in the next prediction period as the model output values,a wavelet neural network velocity prediction model based on time series is constructed.The simulation results verify the prediction accuracy of the model under level 5,level 6 and level 7 sea conditions when the prediction step size is 0.1 s,0.3 s and 0.5 s respectively;(3)Analyze the application methods of support vector machine and libsvm toolbox.Five quantities of platform heave speed,current platform heave speed and displacement and wave heave displacement in the previous two prediction cycles are used as model inputs.Using the method of cross validation,determine the best values of penalty parameters and kernel function parameters under level 5,level 6 and level 7 sea conditions when the prediction step size is 0.1 s,0.3 s and 0.5 s respectively,And predict the heave velocity of the floating platform in the next prediction cycle;(4)Build the co-simulation model of energy-saving winch heave compensation system according to the actual sea conditions,briefly explain the co-simulation implementation method based on the special interface between Amesim-UG/Simcenter 3D motion and MATLAB/Simulink-Amesim software,and verify the compensation effectiveness of energysaving winch heave compensation system under level 5,6 and 7 sea conditions,as well as the assumption that the method based on platform speed prediction can improve the compensation control accuracy;(5)The virtual prototype model of the winch heave compensation simulation test-bed in the laboratory is built.The simulation results show that the 6-DOF platform simulation model can ideally simulate the heave motion of the floating platform,and the compensation effect can be improved to a certain extent by involving the wavelet neural network speed prediction into the compensation control algorithm;(6)Finally,the laboratory heave compensation simulation test-bed and its measurement and control system are improved.The experimental and simulation results show that the hydraulic 6-DOF platform can track sinusoidal heave motion well,and the method based on platform motion speed prediction can improve the compensation accuracy of heave compensation system of winch.