| With the developing of globalization in the 21st century,marine strategy has been treated as one of the most important national strategies.Currently,marine security has also been one of the primary issues for China to achieve security and comprehensive development of the country.As the marine conflict becomes more localized,sudden,and urgent,adopting unmanned platform becomes the best way to realize marine information perception,early monitoring and early warning.As an offshore small floating platform,it can provide a portable and autonomous stabilization platform for marine information detection.Besides,it also can be regarded as a stable detecting and tracking platform with advantages of the quick loading system,storm and surge disturbance rejection,which are realized via the stability control system.Therefore,the disturbance response and attitude stabilization control of offshore small floating platform have been studied in this dissertation,which can also provide the foundation for the follow-up studies of similar platforms.A multi-floating platform program has been proposed with compact structure,fast floating autonomous stability.Taking the offshore small floating platform as the research object,the hytrodynamic model of small floating platform with flexible connection is studied.Also,the disturbance response characteristics of floating platform are discussed under different structure parameters.Aiming at the large-load and high-inertia characteristics of the floating stability platform,the space rigid-flexible coupling dynamic characteristics of the stabilization platform are analyzed.The attitude stabilization control strategy of the floating platform is designed based on the dynamic model and workspace.Finally,the scale model experiment,stability and tracking experiments are carried out to verify the correctness and validity of the dynamic model and attitude stabilization control strategy.The main research contents and innovations are concluded as follows:Aiming at the structure characteristics and working environment of the floating platform,the composition and overall structure program of the floating platform are worked out.A compact floating attitude stabilization platform is designed,and the structure principle and freedom are analyzed.Finally,the analysis method of the offshore small floating platform is summarized.A hydrodynamic model of the small floating platform with flexible connection has been established,and the influence of platform structure parameters on system response has been analyzed.The buoyancy and wave force of the platform body and floating system are calculated based on the ideal fluid hypothesis and the Morison equation.Besides,the restoring force of the elastic joint is calculated by the connection point displacement vector.Then a hydrodynamic model of the small floating platform with flexible connection is established.Afterwards,the frequency-domain and time-domain disturbance response of the floating platform are derived under the three sea level of sea conditions.Then the influences of connection stiffness,float diameter and system center of gravity on the disturbance response of the small floating platform system are analyzed.Based on these,the floating platform structure parameters are optimized.The space rigid-flexible coupling dynamic model of floating attitude stabilization platform has been established,and the influences of inertia parameters and link elasticity on system attitude stability are analyzed.Based on the spatial characteristics and stability requirements of the floating platform,the floating attitude stabilization platform is designed,and its kinematic model and Jacobian matrix are deduced.Then the reachable work space of the platform is calculated with the consideration of its pose constraints and corner characteristics.The dynamic model of the stabilization platform is developed.The dynamic equation of the second order vector is obtained,and the variation law of the equivalent inertia parameters has been analyzed.Based on the space model of the elastic link,the rigid-flexible coupling dynamics model of attitude stabilization platform is built,and the influence of the elastic link on the dynamic performance of the stabilization platform is analyzed.Based on nonlinear disturbance observer,an integral sliding mode control strategy suitable for small floating platform has been proposed,and it improves the attitude stability accuracy of floating platform.The attitude stabilization system of floating platform is constructed.Considering the external disturbance and the electromechanical response time,a nonlinear state space model with un-modeled dynamic and uncertain disturbances is deduced.Based on its workspace,an adaptive sliding mode controller is designed.Furthermore,a nonlinear disturbance observer is designed to observe the external disturbance.Combining the integral term and the conventional sliding mode controller,an integral sliding mode controller is designed to reduce the zero steady state error of the control system.Finally,the validity and robustness of the control strategy has been verified via simulation.The scale model experiment and attitude stabilization and tracking experiment of the offshore small floating platform has been conducted,and the correctness and validity of the numerical model and control strategy established are verified.The overall and subsystem design of the offshore small floating platform are achieved.For the free floating system,the mobile guide is used to track the movement of the scale model,and the hydrodynamic characteristics experiment is designed based on the scale model.Under different wave conditions and structural parameters,the influences on the disturbance response of the system are analyzed.The experimental results have verified the correctness of the hydrodynamic model.The swing test bench is designed to simulate the different direction and frequency disturbance,and the characteristic test system of floating platform is set up.After that,attitude stabilization experiments of the floating platform are carried out for different motion input and load characteristics in the laboratory.The water surface stability and target tracking experiment of the floating platform are carried out,by testing the attitude stability of the floating platform under different disturbance.The experimental results have verified the correctness and validity of the control strategy established. |
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