Research On Path Planning Of Sub-Assembly And Unit-Assembly Arc-Weld Robot In Ship Group

With the development of modern control technology,computer technology,and robot technology,the welding tasks of welding robots are becoming more and more complicated.Welding plays an important role in the shipbuilding industry,which is closely related to the quality and efficiency of shipbuilding.There are some problems in the welding of sub-assembly and unit-assembly components of ships,such as complex weld positions,various types of welds and difficult arc weld path planning.In order to make the welding robot better used in the sub-assembly and unit-assembly welding in ships,it is very meaningful to study the trajectory planning of the welding robot.In this paper,the structure analysis,kinematics analysis,workspace accessibility and flexibility analysis and welding trajectory planning of the welding workstation are carried out on the background of the sub-assembly and unit-assembly welding robot in the ship.The main research contents of this paper are as follows:(1)Firstly,the working requirements of sub-assembly and unit-assembly welding of ships are analyzed,and the gantry is introduced as a positioner to form a welding workstation system with a welding robot to expand the moving distance in space.Secondly,the mechanical structure and related parameters are introduced.The connection and operation modes of different joint connecting rods are analyzed,and the problem of degree of freedom is also analyzed.(2)The kinematics analysis of sub-assembly and unit-assembly welding workstation on ship is carried out.Firstly,the modeling method of robot is analyzed.Taking the welding workstation system as the research object,the kinematics model is established by using the improved D-H method,the forward kinematics equation is solved,the inverse kinematics of the welding robot is analyzed,and the simulation is verified by using the robot toolbox of MATLAB.Finally,the Jacobian matrix and differential kinematics equations of each joint of the system are established by using the vector method.(3)In order to solve the precise operation space and accessibility distribution at the end of thesub-assembly and unit-assembly welding robot,the workspace was analyzed.Firstly,the Monte Carlo method derived from numerical method is selected as the solution method,and the point cloud map of the workspace is obtained by programming in Matlab,and the cavity cavity analysis is carried out.Secondly,the calculation method for the flexibility of any point in the workspace is given,and the flexibility of the representative specific point is analyzed.Finally,a dexterous workspace is obtained,which lays the foundation for the research of the trajectory planning of the welding robot.(4)The trajectory planning algorithm of sub-assembly and unit-assembly welding robots in joint space and cartesian space coordinate systems is studied.Fifth and seventh degree polynomial algorithms are analyzed in joint space.Linear interpolation and circular interpolation algorithms based on trapezoidal and S-shaped acceleration and deceleration control are proposed in Cartesian space.The typical welds of sub-assembly and unit-assembly parts are straight welds and arc welds.Based on the above algorithm,the simulation results show that the curve changes gently,which indicates the correctness of the algorithm.(5)Carry out collaborative trajectory planning research for typical welds in sub-assembly and unit-assembly of ships.Firstly,the typical welds in sub-assembly and unit-assembly are analyzed,including straight welds,vertical fillet welds and arc welds.Secondly,the discretization of weld position and attitude is analyzed.Then,a strategy of motion priority division for different joints in the welding workstation and separate planning for decoupled dual-arm systems into single-arm systems was proposed.A simulation model was built in Matlab Simulink to study the welding trajectory planning.The small rib plate and bottom plate workpiece in the sub-assembly of ship were taken as objects.The simulation results show that each joint moves at a reasonable angle and changes smoothly,which verifies the correctness of the proposed strategy and trajectory planning algorithm.