Kinematics and dynamics analysis of a new-type friction stir welding robot and its simulation

Haitao Luo,Guangming Liu,Lichuang Jiao,Jia Fu,Changshuai Yu,Tingke Wu

doi:10.1177/1687814019866518

Abstract

The mechanical configuration, structural composition, and five typical working conditions of a newly developed friction stir welding robot are introduced. The kinematics model of the friction stir welding robot is established and the forward kinematics equations, inverse kinematics equations, and the Jacobian matrix are solved. In addition, the dynamics model of the friction stir welding robot is also built by using the Lagrange method. The centroid position coordinate and inertia matrix of each part are obtained. Finally, the dynamic equation of friction stir welding robot is determined. According to the kinematics and dynamics model of robots, simulation analysis for friction stir welding robot based on virtual prototyping technology was carried out. The trajectory equation of the weld joint under the condition of melon petal welding is established, the spline trajectory is fitted by many discrete points measured by the contact probe, and the trajectory planning of each joint and the changing laws of motion parameters under the friction stir welding robot melon petal welding condition are obtained. The movement laws and the loading conditions of each joint can be better controlled by designers, and provide solid theoretical support for the static and dynamic characteristics analysis and structural optimization of the friction stir welding robot.

Highlights

Friction stir welding (FSW) is widely used in aerospace as a solid phase joining technology
In order to make the designed robots meet the technical specifications of the actual welding requirements, the kinematics and dynamics of FSW robot (FSWR) should be analyzed.[9,10,11]
From the kinematic equation (5) of the FSWR, it can be seen that the attitude matrix is decoupled, and the rotational joint variables u4 and u5 uniquely determine the attitude of the end of the FSW tool

Summary

Introduction

Friction stir welding (FSW) is widely used in aerospace as a solid phase joining technology. In order to make the designed robots meet the technical specifications of the actual welding requirements, the kinematics and dynamics of FSWR should be analyzed.[9,10,11] This work mainly includes the solutions of kinematics, dynamics, and the Jacobian matrix.[12,13] Among them, the forward kinematics solution determines the position and posture of the robot from joint space to end tool space, and the inverse kinematics solution is the opposite, its goal is corresponding trajectory planning. The inverse solution of the kinematics of the FSWR is the position ~p and the attitude ~n ~o ~a of the end FSW in the known working space, and the values of the respective joint variables d1, d2, d3, u4, u5, and d6 in the joint space range are inversely obtained. From the kinematic equation (5) of the FSWR, it can be seen that the attitude matrix is decoupled, and the rotational joint variables u4 and u5 uniquely determine the attitude of the end of the FSW tool. By performing coordinate transformation and theoretical derivation on the coordinate system of the connecting rod, the following equations are obtained

Recursive formula for the acceleration of the moving joint link

The Lagrangian function L of the robot is solved

Conclusion