Research On Control Method Of Parallel Motion Compensation Platform For Offshore Platforms

With the increasing severity of environment problems and energy crisis,all countries have strengthened the development and utilization of ocean resources.The motion compensation platform,which can effectively isolate the shaking caused by the ocean conditions,is of great importance to ensure the safety of the of the equipment and staff working on the platform.Based on a new type of 3-DOF parallel mechanism,the control strategy and implementation method of the the parallel motion compensation system for the offshore platform are deeply studied in this thesis.Firstly,the kinematics model of the parallel mechanism is established based on numerical iterative method,the mapping modles of the mechanism's velocity and acceleration are constructed according to the constraints of synchronous driving,and the dynamic model is established using virtual work principle.The mathematic models are verified by MATLAB and ADAMS.Secondly,according to the in-depth analysis of the traditional servo system's three-loop control principle,a torque-feedforward servo control strategy based on the mechanism's dynamic model is designed,programmed and developed on a highly open motion controller CK3M that supports EtherCAT bus technology.The effectiveness of the user-defined servo control algorithm is verified and the effect of each parameter in the algorithm is analyzed.As well,the controller parameters suitable for the parallel motion compensation platform are optimized.Then,the ship pose measurement system is built based on a dual-axis tilt sensor and a host computer,the motion control system is structured with the motion controller,servo drivers and servo motors,and the 3-DOF parallel mechanism is used as the motion compensation system,the whole parallel motion compensation platform is achieved.Next,the the software development of the parallel motion compensation platform control system is achieved with Lab VIEW,MATLAB and Power PMAC IDE,and the functions of ship pose acquisition and motion prediction,dynamic feedforward servo control and real-time compensation of the external attitude disturbance are achieved.Finally,the feasibility experiment of the user-defined dynamic feedforward control algorithm has been carried out.The experimental results show that the position tracking accuracy and dynamic response speed can be significantly improved using the dynamic feedforward control algorithm.