Research On Attitude Prediction And Compensation Control Algorithm Of Six-Degree-of-Freedom Motion Platform

In the background of the ocean power strategy,China has entered the period of large-scale development and utilization of the ocean,and offshore operations and distant sea operations will become the norm.The sea environment is changing rapidly,and the six degrees of freedom motion of the operating platform under the influence of sea wind,waves and currents is the main factor that hinders the smooth development of offshore operations and threatens the personal safety of operators.Therefore,in this thesis,the short-time prediction of motion attitude and active sixdegree-of-freedom motion compensation technology are carried out to address the above problems,and the specific research contents include:(1)To address the problem that safety accidents are prone to occur after operators’ decision errors in the operation of ships and offshore equipment under high sea state,a combined EEMDLSTM-based prediction model is proposed in this thesis for the prediction of the motion attitude of offshore platforms.The ship’s transverse rocking motion data under 4 levels of sea state are simulated and used as the prediction experimental data set.The prediction experimental results show that compared with the prediction method using a single LSTM model,the RMSE error based on the combined EEMD-LSTM model prediction decreases by 29.6%,MAE error decreases by 29.3%,and MAPE decreases by 52.7%.(2)Aiming at the problems of slow progress and safety hazards of offshore operations caused by six-degree-of-freedom motions of the operating platform influenced by wind,waves and currents,this thesis designs an experimental system scheme of motion compensation based on Stewart parallel platform.Through the analysis of the motion compensation experimental system,the algorithm for solving the spatial position of the operating platform under the global coordinate system when excited by the six degrees of freedom motion of waves is proposed,based on which the six degrees of freedom motion platform compensation control algorithm is further proposed.Finally,a simulation model of the system is built to verify the correctness of the relevant algorithm.(3)The construction of the motion compensation experimental system was completed,and then the PID-based AC servo system controller was designed based on the completion of the derivation of the kinematic inverse solution formula of Stewart parallel robot through the study of the control strategy of the motion compensation experimental system.Finally,the design of the control software of the motion compensation experimental system is completed,which realizes the functions of human-computer interaction,hardware data communication,motion compensation control and motion simulation.(4)On the basis of completing the construction of the motion compensation experimental system,the basic control experiments related to the experimental platform were first designed,and the experimental results proved that the control scheme of the experimental system could meet the demand of the motion compensation experiments.Then the motion compensation experiment was designed to experimentally verify the motion compensation control algorithm.compared with the method of using attitude sensors to measure data first and then perform motion compensation.The average absolute errors of compensation decreased by 86.7%,92.9%,55.9%,87.9%,93.5%,and90.7%,respectively.The experimental results demonstrate that the compensation algorithm proposed in this thesis can effectively compensate the motion of six degrees of freedom,and also verify the feasibility of combining the short-time prediction technique of motion pose with the motion compensation technique to reduce the motion compensation time lag,which provides ideas for the subsequent research.