Design And Performance Analysis Of A Rigid-flexible Friction Stir Welding Robot

In order to meet the design requirements of friction stir welding(FSW)equipment,a 3-degree-of-freedom rigid-flexible 3Cable-Driven/3UPS-UP(3CD/3UPS-UP)hybrid manipulator was applied to the main feed mechanism of the FSW robot.The kinematics analysis of the new hybrid manipulator was carried out,and the kinematics performance comparison with the traditional 3UPS-UP parallel mechanism was carried out.The static model of the cable mechanism was established,and the dynamic equation of the whole mechanism was established based on the Lagrange method.Compared the driving force with the traditional 3UPS parallel mechanism,it is proved that the rigid-flexible 3CD/3UPS-UP hybrid mechanism has higher load capacity and force balance.The main contents include:(1)Aiming at the welding requirements of aluminum alloy parts for aviation and automobiles and the design requirements of robot friction stir welding technology,a new three-degree-of-freedom redundant drive rigid-flexible 3CD/3UPS-UP hybrid mechanism was adopted as the main feed mechanism of the FSW robot.(2)The kinematics analysis of the rigid-flexible hybrid mechanism was carried out.The complete homogeneous dimensional Jacobian matrix of the 3CD/3UPS-UP manipulator was solved using the Jacobian matrices of the 3UPS parallel sub-mechanism,UP series sub-mechanism and cable sub-mechanism.And the kinematic performance indexes,such as the workspace,carrying capacity,dexterity,and stiffness were established.The concept of a composite quality workspace was proposed.(3)By compared the kinematics performance of 3CD/3UPS-UP hybrid mechanism and the traditional 3UPS-UP parallel mechanism,it was proved that the carrying capacity,dexterity,and stiffness of a rigid-flexible 3CD/3UPS-UP hybrid manipulator is significantly improved by adding a cable sub-mechanism.The composite workspace of 3CD/3UPS-UP mechanism was drawn,and based on the above performance indexes,the multi-objective size optimization of the mechanism was carried out.(4)Taking the mechanical model of the uniaxial shoulder mixing head as an example,the static model of the cable mechanism is established,and the mechanical simulation is carried out with Adams software.The simulation results show that the3CD/3UPS-UP hybrid mechanism can offset part of the forging force and feed resistance of the stirring head by the cable mechanism,thereby improving the overall load capacity.(5)The dynamic equation of the 3CD/3UPS-UP hybrid mechanism was established by Lagrangian method.The optimal driving force distribution was carried out,and compared with the traditional 3UPS-UP parallel mechanism.The comparison results show that the driving force of each branch of 3CD/3UPS-UP hybrid mechanism is lower than that of 3UPS-UP parallel mechanism under the same working condition,which proved that the 3CD/3UPS-UP hybrid mechanism has better control accuracy and force stability.