| The traditional modeling of underwater vehicle is usually based on the theory of fluid dynamics to establish a nonlinear dynamic model,and rely on professional fluid analysis software or design special experiments to determine the system parameters in the dynamic model.This method is often very complex,and sometimes the accuracy of the system parameters is not high.For the tail-driven underwater vehicle,its dynamic model has the characteristics of nonlinear coupling of motion parameters,time-varying swing input and underactuation,which makes its control design very challenging.Aiming at the problem of modeling and control of the tail-driven underwater vehicle,this paper studies the modeling and control method of the robot based on the first principle,avoiding the previous idea of determining system parameters through fluid simulation analysis and experiment.In order to achieve this task,this paper mainly includes the following research contents: the dynamic modeling of the underwater vehicle,the system parameter identification of the dynamic model of the underwater robot and the motion control of the underwater vehicle based on Lyapunov stability analysis.In this paper,firstly,the research status of kinematics modeling and control,hydrodynamics modeling method and motion control of underwater vehicles at home and abroad are summarized.Aiming at the difficulties of current research,the research content of this paper is determined.(1)In order to solve the dynamic modeling problem of a tail-driven underwater vehicle with a movable mass,the Newton Euler method is used to establish the whole dynamic model of the underwater vehicle,and then each term is determined to get the specific form of the dynamic model.The internal movable mass block is simplified as point mass,and the specific expression of momentum and angular momentum in the dynamic model is obtained through the derivation of the system kinetic energy with respect to the velocity and angular velocity matrix respectively.Then,the hydrodynamic forces and moments,the tail forces and moments and other forces and moments are analyzed,and the specific form of the dynamic model is finally determined.(2)Aiming at the determination of hydrodynamic parameters in the dynamic model,the method of system identification is proposed to determine the system parameters in the dynamic model.In this paper,the system parameter identification problem is transformed into a convex optimization problem by using the linear characteristics of the hydrodynamic forces and moments in the dynamic model with respect to the hydrodynamic force and moment coefficients and the system parameters are obtained by solving the convex optimization problem.Then the corresponding experiments are designed,and the simulation results and experimental results of the dynamic model are compared to verify the accuracy of the dynamic model.(3)In the problem of target tracking,according to the characteristics of the periodic swing of the robot tail,this paper designs the corresponding controller based on the Lyapunov stability analysis using the average dynamic model of the underwater vehicle.Two auxiliary state variables are introduced to describe the tracking state of the target.Using backstepping control technology,a closed-loop distance controller is designed to make the trajectory of the underwater robot converge to the target within a certain error range.An open-loop turn controller is proposed to control the azimuth deviation within the specified range.At the same time,a hysteretic switching strategy is proposed to determine which controller is activated.The simulation results verify the feasibility of the method. |
