Research On Switching Control Technology Of Underwater High-speed Vehicle

Supercavitation technology is a revolutionary drag reduction technology. Due to the cavitation wrapped completely, the vehicle almost lost most of the buoyancy which greatly reduces the contract area of the vehicle and water.Therefor, the speed of the vehicle can be improved in the water. According to the excellent characteristics of the supercavitation technology, the underwater weapon can be made with high speed and far range. So the major world powers have a research on supercavitation technology and supercavitation high-speed vehicle. Although supercavitation technology can greatly improve the vehicle speed, the hydrodynamic characteristics will have great changes with the cavitation. The dynamic characteristics will have large difference compared with the ordinary underwater vehicle. This makes the modeling and controlling more difficult of the underwater high-speed vehicle.This paper mainly studies the longitudinal plane of the vehicle, and the mathematics model is established on the basis of the stress analysis. Considering the nonlinearity of the planing force, the mathematical model is divided into the linear part and the nonlinear part. Then the controllers will be designed aimed at two models. According to a switching control strategy,the two sub controllers can do a smooth switch in order to achieve the requirement of the depth control.First, introduce the research background and the significance of the underwater high-speed vehicle, and introduce the present research situation of switching control.Next,introduce the basic theory of supercavitation and analyse the stress. Then, the dynamic equation is established based on dynamic principle. So the mathematical model is achieved.Second,considering the characteristics of mathematical model,the mathematical model is divided into the linear part without planing force and the nonlinear part with planing force.According to the linear model, the state feedback controller is designed by the pole assignment method. According to the nonlinear model, variable structure controller is designed with the uncertain factors and disturbance to realize the depth control.Finally, according to two different sub controllers, the control strategy based on switching threshold is proposed. Make the two controllers do a switching to achieve the depth control.Due to the existence of the planing force, the sufficient condition for the global stability of the system is obtained by the circle criterion and the absolute stability. To improve the system performance,a switching control strategy is proposed, in which a nonlinear excitation is introduced to weaken the inherent nonlinearity. Because the threshold switching having some stiff,not enough smooth, a fuzzy switching control method is raised based on fuzzy rules.The method can meet the requirements of stable switching, and it has a good physical realization.