Research On Longitudinal Control Of Water Entry Of Supercavitating Vehicle

The research on supercavitating vehicle has been paid attention by many countries all over the world.Because supercavitation makes the resistance of the vehicle greatly reduced under water,it can achieve a very high speed under the propulsion of rocket engine,which is much higher than that of ordinary vehicle(such as conventional torpedo).However,because of the complex force acting on supercavitating vehicle,when its speed is too fast,the control of the vehicle becomes very important.Difficulties,how to effectively control the high-speed movement of supercavitating vehicle in water has always been the focus of research by domestic and foreign researchers.Longitudinal control of supercavitating vehicle underwater is a hot research field in many countries in the world.In this paper,the longitudinal control of the entry process of supercavitating vehicle is studied.The main research contents are as follows:Firstly,the force analysis of supercavitating vehicle in underwater environment is carried out,the body coordinate system of the vehicle is given,the dynamic equation of the vehicle is established according to the condition assumption and the force condition of the vehicle,and then the kinematics equation of the vehicle is established.The tail gliding force of the vehicle in the whole motion of entering water is analyzed,and the tail gliding force term is added into the kinematics by the approximate term substitution method.The equation makes the kinematics model of the vehicle describe the actual system more accurately.Secondly,the water entry experiment of supercavitating vehicle model is carried out,the specific flow of the whole experiment and the relevant important experimental equipment are introduced,the theoretical basis of the experiment is studied,and the data acquisition is carried out by using the self-designed acceleration measurement module inside the vehicle.The collected data are analyzed and the correlation of the change law of impact load on the vehicle model during the water entry process is obtained.In conclusion,two important parameters,optimal inflow angle and switching delay time,are determined,and two sub-stages of inflow motion are defined.Then,the mathematical model of the vehicle is improved to transform it into a standard LPV system model,and then the sub-controller control algorithm of the first entry stage of the vehicle is designed by the piecewise integrated control method based on the LPV system.Then,according to the standard model of the longitudinal motion of the vehicle established in the previous chapter,the second stage of the vehicle is designed by the sliding mode variable structure control method of control algorithm of sub-controller.Finally,the switching delay time is taken as the node time,and the switching control rules of time-dependent single-value method are given as the switching strategy of the global control of the vehicle,and the design of the global switching control algorithm is completed.Finally,in the environment of Matlab,the simulation validation of the piecewise integrated controller and sliding mode variable structure controller is carried out respectively,and then the global simulation of the piecewise control system is carried out according to the switching control rules.Based on the analysis of the actual simulation results,the design idea of the piecewise controller and the feasibility of the selection scheme of the two motion stage controllers are discussed again.