| Ship motion simulator is used to reproduce the motion state of the ship,and it has the advantages such as reliability,economy and controllability.The hydraulic driven ship motion simulator is influenced by the nonlinear factors of the hydraulic system,which has the problems including poor tracking precision and low frequency bandwidth,etc.Traditional linear model based control strategy can hardly meet the precision requirements of the motion simulation system.This subject takes the hydraulic 6-DOF platform system of the ship motion simulator as the research object,and studies the nonlinear modeling and control strategy of the system.In the second chapter,the co-simulation modeling of the hydraulic 6-DOF platform system is mainly studied.The flow equations of asymmetric throttle valve orifice,the continuity equation of asymmetric cylinder flow and the force balance equation of load are derived respectively.Based on the Matlab/Simulink platform,a simulation model of asymmetric valve controlled asymmetric cylinder power mechanism is built.The three-dimensional model of the mechanical system of the ship motion simulator is constructed,and it is introduced into the ADAMS platform and the simulation model of the mechanical system is established.A control system model is established by using Matlab/Simulink,and a co-simulation model of 6-DOF platform for ship motion simulator is established through interaction interface between software,so as to lay the foundation for selecting appropriate control strategy.In the third chapter,the control strategy of hydraulic 6-DOF platform based on nonlinear model is studied.Specifically,the position and position instruction of the platform is converted to the displacement instruction of six hydraulic cylinders by virtue of inverse kinematics analysis.To meet the requirements of dynamic response such as step response and bandwidth of motion simulator,a vibration control compensation and feedback linearization control strategy based on frequency characteristics is proposed.In the vibration control compensation method,the feedback correction controller is designed based on the system transfer function in the outer loop,and the deviation between the response signal and the desired signal is reduced by modifying the driving signal,and the system bandwidth is increased.Within the control strategy,the nonlinear link in the hydraulic power mechanism is counteracted based on state feedback,and it is converted to a linear system.Then pole placement method is adopted to improve the dynamic performance index of the system.In the fourth chapter,the effectiveness of the nonlinear mathematical model of hydraulic 6-DOF platform is verified by step response,sinusoidal motion and frequency characteristic experiments.Then,the vibration control compensation link is designed based on the frequency characteristic analysis,and the effectiveness of the control strategy is further verified by the sinusoidal motion test. |
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