Dynamic Analysis And Sliding Mode Control For Trajectory Tracking Of Underwater Manipulator

In recent years,the underwater manipulator has been continuously developed,and hasbeen applied to the research and application of marine resources development engineering.The working environment of underwater manipulator is highly nonlinear.The operation precision of underwater manipulator in shallow water environment is easily influenced by the actual conditions of fluid viscous resistance and other actual working conditions.The design of the trajectory tracking controller for underwater manipulator is related to the stable work of the underwater robot,and the motion control of the angle and angular velocity between the joints of the manipulator is the prerequisite for the accurate work of the end actuator of the manipulator.Therefore,it is great theoretical and applied value to study the tracking and motion control of the underwater manipulator.First of all,a general method of D-H modeling for the connecting rod of manipulator is introduced.The D-H method is used to establish the coordinate system of the underwater manipulator.The information list of the connecting rod twist angle,the bias of the connecting rod,the joint angle,the length of the connecting rod and so on is arranged and filled in.Then the geometric relationship of the manipulator in Cartesian space is established through the homogeneous coordinate transformation.The study of forward kinematics is based on knowing the parameters of each link of the manipulator,and using the homogeneous transformation matrix to extrapolate the pose of the end effector.On the contrary,the inverse kinematics problem is to calculate the joint angle of the connecting rod of the manipulator by the Euler transformation in the case of the connecting rod twist angle,the linkage bias,the length of the connecting rod and other parameters of the known underwater manipulator.Then,using the slice theory to analyze and deduce the nonlinear forces such as the hydraulic drag and the additional mass force of the connecting rod of the manipulator,and establish a more accurate dynamic equation of the underwater two joints manipulator system.The simulation model of underwater manipulator is built and ODE45 is used to solve the dynamic equation.The influence of hydraulic drag on the trajectory of the manipulator is compared and analyzed.Finally,by using the sliding mode control theory,the sliding mode adaptive control law is designed by constructing the sliding mode surface related to the angle tracking error and the angular velocity tracking error,and the simulation of the angle and angular velocity tracking of the underwater manipulator is completed.Finally,on the basis of sliding mode control theory,the radial basis neural network model is introduced to track the trajectory tracking problem of multi-joint underwater manipulator,and a trajectory tracking sliding mode controller based on neural network is established.The nonlinear function of the nonlinear coupling force,such as hydraulic drag,additional mass force and uncertain wave disturbance,is approximated by radial basis neural network,and the robust term is added to the control law to eliminate the approximation error,and the update rate of weight matrix is designed by Lyapunov stability theory,the global stability of the system is ensured.Finally,a simulation experiment of a two joints underwater manipulator is simulated to verify that the control algorithm based on this method has high tracking accuracy and robustness.