Study On High Speed Inclined Water Trajectory Prediction And Nonlinear Control Method

With the rising of modern weapons,the traditional single medium combat weapon is hard to meet the demand of the battlefield environment,supercavitation bodies,to the largest extent,joint air and underwater navigation gap,the speed of the two kinds of different medium condition and supercavitation bodies with supercavitation drag reduction technology,can greatly improve the sailing body sailing speed and distance,So as to improve the operational effectiveness of the vehicle.In this paper,the entry trajectory prediction and the leveling control of the vehicle are studied based on the high speed entry of the vehicle.Firstly,the research status of water entry problems at home and abroad is investigated.The main content of the investigation is to report the development situation and trend of water entry test,water entry simulation and water entry theory.Secondly,based on the homogeneous multiphase flow theory,the governing equation is based on the conservation equation of mass,momentum and energy.The VOF model is introduced,and the standard k-? turbulence model is selected to solve the RANS equations.At the same time,the mass transfer caused by cavitation effect is considered for numerical calculation.On this basis,a numerical method for calculating the characteristics of multiphase flow with high speed oblique water entry was established by using overlapping grid calculation.The cavitation evolution process,the ballistic characteristics of the vehicle and the dynamic characteristics of the fluid are analyzed.Then,based on momentum conservation and Logvinovich’s independent expansion principle,the cavitation model was deduced,and the trajectory prediction model was established for the water entry process in combination with the classical mechanics theory.Based on this model,the ballistic characteristics under different water entry conditions were studied.Finally,the research on the active leveling control of vehicle entering water at high speed is carried out.The aft rudder force model was established,and then the longitudinal control model of high-speed entry vehicle was deduced.A backstepping tracking controller was designed based on the longitudinal plane model of the vehicle.Finally,the leveling ability of the controller was verified by simulation analysis.