Conceptual Design And Dynamics Analysis Of Negative Buoyancy Underwater UAV

Underwater vehicles are playing an increasingly important role in the exploration and utilization of marine resources.The complex marine survey and marine engineering tasks are also having higher and higher performance requirements for underwater vehicles.Currently,most underwater vehicles are designed for neutral buoyancy and need to carry large volume of buoyancy materials,resulting in its larger size and weight,low volume utilization,and low capacity.Moreover,the traditional underwater vehicle has to be changed for layout design and then re-trimmed,for different load requirements,which will bring inconvenience for designing and maintenance.Therefore,this paper presents a new type of negative buoyancy underwater unmanned aerial vehicle(UAV)which has reduced the requirements of re-trim and space layout,thus having a higher space utilization and high capacity.In this paper,the dynamic behaviors of negative buoyancy underwater UAV is studied by using a 6-DOF dynamic model and the hydrodynamic coefficients.The main contents are as follows:(1)A new type of negative buoyancy underwater UAV is proposed,which uses a pair of wings with large lift-to-drag ratio and variable angle of attack to provide lift to offset the negative buoyancy during the voyage.Through the analysis of working principle,numerical calculation and simulation,the proposed underwater UAV is proved to be feasible and advanced.(2)A 6-DOF dynamic model of the underwater UAV considering the controlling parameters of the rotational speed of propeller,angles of rudder and elevator,and setting angle of wing is established.The model can show the dynamic behaviors of the negative buoyancy underwater UAV accurately.The validity of the model is verified by the simulation results.(3)By using the FLUENT software,part of the hydrodynamic coefficients of negative buoyancy underwater UAV are simulated,and then compared with those of the traditional Autonomous Underwater Vehicle(AUV).Hydrodynamic coefficients of negative buoyancy under water UAV provides accurate basis for simulation.(4)The dynamic behaviors of negative buoyancy underwater UAV is studied.In this paper,motions of the negative buoyancy underwater UAV in horizontal plane,vertical plane and space are simulated by the fourth-order Runge-Kutta numerical method using Matlab software.The validity of the dynamic model and the principle of negative buoyancy underwater UAV are verified.(5)The dynamic behaviors of motions in vertical plane and horizontal plane are studied and compared with those of traditional AUV.The proposed underwater UAV is proved to have the same motion performance as the traditional AUV.The coupling between swaying motion and rolling motion and that between motions in horizontal plane and vertical plane are analyzed.An effective decoupling method is proposed.