Research On Virtual Anchor Buoy Navigation And Control Strategy

As a new marine environment observation platform that abandons the traditional mooring cable,virtual mooring buoy can capture various environmental energy for its capabilities of autonomous mooring point switching,precise virtual mooring and long-time fixed point.observation of global meteorology and hydrology.However,control algorithms for mooring point switching and virtual mooring are relatively rare in the present references.Thus,a new navigation control strategy for the virtual mooring buoy was proposed,which integrated mooring point switching control algorithm and virtual mooring control algorithm.Simulations were carried out to verify the correctness and effectiveness of the control strategy.The main research contents are as follows:Firstly,the movement mechanism of the virtual mooring buoy was studied,the 4-DOF dynamic model of the virtual mooring buoy with surge,sway,heave and yaw was built using Fossen matrix,and the dynamic behavior of the virtual mooring buoy was simulated.These laid the foundation for the research of the following navigation control strategy.Secondly,to deal with the location switching problem of the virtual mooring buoy between mooring points,the mooring point switching control algorithm was put forward.The navigational information was obtained by the sight tracking algorithm based on inverse solution of the Gauss geodetic problem,and the improved single-neuron adaptive PID controller was adopted to switch the position of the virtual mooring buoy between the preset mooring points.The controller with simple structure has good adaptability,self-learning capability and strong robustness.Thirdly,the virtual mooring control algorithm was presented to deal with the difficulty in stably mooring with high control precision when the virtual mooring buoy was in motion state.The virtual mooring circle was introduced to convert the virtual mooring problem into the path tracking problem.Besides,the Serret-Frenet coordinate transformation and redefinition of output variables were utilized to convert single-input and multi-output underactuated nonlinear system into single-input and single-output nonlinear system.Then RBF neural network fuzzy sliding mode controller was put forward to realize the virtual mooring within a certain range of mooring point.The chattering phenomenon of the siding mode control was alleviated and adjusted by the fuzzy algorithm in real time.The uncertainty of the dynamic model was approximated using the RBF neural network,which greatly helped the sliding mode controller escape the dependence on the system model and improved the robustness of the controller.The stability of the controller was proved using the Lyapunov stability theory.Finally,to verify the proposed navigation control strategy,simulations and analysis on the mooring point switching control algorithm and the virtual mooring control algorithm were carried out.The results showed that the navigation control strategy could reliably accomplish the ocean navigation and mooring missions with strong stability and robustness.