Research On Modeling And Compliance Control Alogrithm Of Underwater Manipulator

With the decrease of land resources,it is necessary and urgent to expand the exploitation of marine resources nowadays.Because of the complexity of underwater environment,people usually use underwater robot to carry underwater manipulators to complete deep-sea exploration and development.As a highly mechatronic equipment,underwater manipulator is widely used in exploration of marine resources,underwater engineering construction,marine national defense and other fields.The technology of underwater manipulator fully reflects the advanced level of underwater robot.Different from the manipulator working in the air,the manipulator working in the water will be subject to the viscous resistance of the water and sometimes the impact force of the current.It is not enough to control the position of the underwater manipulator only,but also need to control the flexibility of the underwater manipulator.Therefore,it is necessary to study the compliance control method of the underwater manipulator,which is the basis of the normal operation of the manipulator.In this paper,aiming at a large-scale underwater manipulator,the kinematics model and dynamics model of the underwater manipulator are established,and the position based joint impedance control strategy is designed by combining kinematics analysis and dynamics analysis.The correctness and stability of the control strategy of the underwater manipulator are verified and analyzed by simulation experiments.The specific research contents are as follows:Firstly,according to the configuration of the underwater manipulator,the joint coordinate system of the manipulator is established by D-H standard method.The forward and inverse kinematics and Jacobian formula of the manipulator are derived in detail,and the kinematics simulation platform of the manipulator is built in the MATLAB robot toolbox.The workspace of the manipulator is obtained,and the correctness of the forward and inverse solutions is verified.Secondly,the dynamic analysis of the underwater manipulator is carried out,focusing on the hydrodynamics of the underwater manipulator.According to the Lagrange method,the dynamic equation of the underwater manipulator is established.The hydrodynamic term in the equation is calculated based on the Morrison formula,and the dynamic coefficients of water intake is calculated by fluid simulation software FLUENT.The hydro of the underwater manipulator is divided into two parts: the water stirring force in the still water environment and the sea current impact in the static state.The dynamic model of the underwater manipulator is established in ADAMS.According to the joint moment,the influence of buoyancy,water resistance,flow interference in different directions and sizes on the underwater manipulator is quantitatively analyzed.Finally,based on the kinematic and dynamic analysis of the underwater manipulator,an impedance control strategy based on the joint position is designed.The simulation platform of underwater manipulator control system is built by using ADAMS-MATLAB/Simulink.The influence of impedance parameters on the control system is studied,and several groups of comparative simulation experiments are carried out,which analyzes the influence of water environment and water resistance on underwater manipulator control system.