Study of kinematics analysis and trajectory planning for welding robot

LIU Peng， SONG Tao， YUN Chao， GAO Zhi-hui
（School of Mechanical Engineering and Automation， Beihang University， Beijing 100191， China）

Abstract： Aiming at the welding difficulties of beam structures，liquefied petroleum gas containers and other large weldments，a 7 degrees of freedom （DOF） large welding robot was developed. After the analysis of the mechanical structure，robot kinematics equations were built to analyze robot kinematics problems，based on D-H coordinate system theory. A new cubic polynomial interpolation method，characterized by pass waypoints，was proposed to plan robot joint trajectory by interpolation calculation in joint space combined with motion parameters in operation space. Robot kinematics and trajectory planning method were simulated，according to the robot model，built by Robotics Toolbox on the platform of Matlab7.8. The results indicate that the robot parameter design is reasonable and the planning robot joint trajectory by interpolation calculation in joint space is feasible，which will provide a basis for future studies on kinetics，and this technology has been applied to spot and fillet welding operation.
Key words： welding robot； kinematics； trajectory planning； D-H coordinate system theory； Matlab