Coordinated motion control of multiple robotic devices for welding and redundancy coordination through constrained optimization in Cartesian space

The authors consider the problem of coordinating multiple motion devices for welding purposes. They focus on the problem of controlling a positioning table and a seven-axis manipulator, given the parametric definition of a trajectory on a weld piece. The problem is complex as there are more than nine axes involved and a number of permutations are possible which achieve the same motions of the weld torch. The system is redundant and the robot has singular configurations. As a result, manual programming of the robot system is rather complex. The authors illustrate an approach to redundancy control and coordination of a multiple-robotic-device arc welding system that does not require manual teaching of the intermediate trajectory points. The system requires only the start and end points of the trajectory for setting up and calibration. The redundancy coordination scheme is based on constrained optimization of the maneuverability of the manipulator in Cartesian space. To bypass accuracy issues related to joint rate control, inverse kinematics is directly used in the kinematic control of the manipulator