Underactuated joining system for moving assembly line

An underactuated joining system for use with a workpiece transported by a moving assembly line, comprising:

• a robot having a plurality of actuated joints;
• an articulated compliance mechanism coupled to the robot and having a range of motion, the articulated compliance mechanism including multiple linkages, an end-effector connected to the multiple linkages and configured to connect to a joining tool, a plurality of unactuated joints interconnecting the linkages, and one or more position sensors collectively configured to measure corresponding joint positions of the unactuated joints;
• and
• a controller in communication with the position sensors, wherein the controller is configured, in response to the corresponding joint positions, to selectively control a respective position of the actuated joints, and to thereby cause the articulated compliance mechanism to compliantly follow the workpiece as the workpiece is actively transported by the moving assembly line while the joining tool is engaged with the workpiece while the joining tool remains engaged therewith, such that mutually engaged rigid bodies are in motion, by:
• continuously determining a displacement in the articulated compliance mechanism as the workpiece is transported by the moving assembly line;
• and
• commanding a motion of the robot that closes the displacement and thereby maintains the articulated compliance mechanism in a center of the range of motion to thereby cause the underactuated joining system and the joining tool to compliantly follow or track the workpiece as the workpiece is transported by the moving assembly line.