Robot Base Placement and Kinematic Evaluation of 6R Serial Manipulators to Achieve Collision-Free Welding of Large Intersecting Cylindrical Pipes

This paper presents a systematic approach for identifying feasible robot base placement regions within a workcell, and evaluating performance of industrial robots for the design of mobile industrial robotic system to perform collision-free automated welding of large intersecting cylindrical pipe structures. First, a mathematical model based on the geometry of intersecting cylindrical pipes is used to generate the welding task and torch orientation. Next, collision detection is performed using line geometry and possible robot base positions are identified and rated according to the manipulability measure. This yields a graph of feasible robot base placement regions that perform collision-free welding rated in terms of its dexterity. Finally, a task metric based on kinematic measures to evaluate the robot’s performance is proposed and discussed. An implementation of this approach for evaluating two different 6R industrial robots for welding jack-up rig structures was used as examples. This technique will also be applicable for designing mobile robotic system for tasks other than welding which may require trajectory-following end-effector motion uninterrupted by objects within the workspace such as painting, taping, blasting, cutting, etc.