Dynamic Modeling And Control Of Underwater High Speed Robot

The conventional underwater robot is completely wrapped by fluid,the fluid resistance it suffers is large,and it has been difficult for the navigation speed to exceed 40 m/s for a long time.The supercavitation drag reduction technology can reduce the navigation resistance of underwater robots by more than 90%,and the navigation speed can be increased to the order of 100 m/s.Therefore,the use of supercavitation drag reduction technology for underwater robots has important research significance.The supercavitation drag reduction technology is to wrap a layer of cavitation on the outer surface of the robot so that it does not directly contact the liquid,thereby greatly reducing the fluid resistance,but it will also lose most of the buoyancy due to the cavitation wrap.Therefore,based on the super while the underwater high-speed robot with cavitation drag reduction technology achieves high speed,its dynamic modeling and control system design are more complicated than traditional underwater robots.This thesis is based on the "Thirteenth Five-Year" scientific and technological research project of Jilin Province,"Research on Time-Varying Dynamics Modeling and Control Technology of Underwater High-Speed Supercavitation Torpedo"(approval number: JJKH20181139KJ),based on supercavitation drag reduction technology research on the time-varying dynamic model and control technology of the underwater high-speed robot.The main work and research results of this paper are as follows.A detailed force analysis of the main parts of the underwater high-speed robot is carried out.Based on the consideration of the cavity axis offset and the efficiency of the tail,the nonlinear time-varying dynamics equations are established using the dynamic theorem.Then,according to the motion characteristics of the longitudinal plane,the established nonlinear time-varying dynamics equations are simplified into the longitudinal plane to obtain the nonlinear time-varying dynamic model of the longitudinal plane.The simulation analysis of the dynamic characteristics of the dynamics shows that the open-loop underwater high-speed robot system cannot maintain the motion stability,and a suitable motion controller needs to be designed for it.Due to uncertain factors such as model parameter uncertainty and external interference,and the above uncertain factors satisfy the matching conditions for underwater high-speed robots,a trajectory tracking controller is designed for it using sliding mode variable structure control theory.The simulation results show that the underwater high-speed robot with model parameter uncertainty and external interference can track the predetermined trajectory well,but the state variables and control variables have a certain degree of chattering.Aiming at the chattering problem of sliding mode variable structure controller,an adaptive sliding mode variable structure controller based on RBF neural network is designed.The RBF neural network is used to compensate for the uncertainty and external interference of the model parameters,and the Lyapunov theory is used to derive the weight change rate of the RBF neural network,which proves the stability of the control strategy.The simulation results show that the underwater high-speed robot with model parameter uncertainty and external interference can not only track the predetermined trajectory well,but also greatly reduces the chattering phenomenon of state variables and control variables.