High-Accuracy Robotized Industrial Assembly Task Control Schema with Force Overshoots Avoidance

The presented paper proposes an analytical force overshoots free control architecturefor standard industrial manipulators involved in high-accuracy industrial assemblytasks (i.e., with tight mounting tolerances). As in many industrial scenarios, the robotmanipulates components through (compliant) external grippers and interacts with partiallyunknown compliant environments. In such a context, a force overshoot mayresult in task failures (e.g., gripper losses the component, component damages), representinga critical control issue. To face such problem, the proposed control architecturemakes use of the force measurements as a feedback (obtained using a force/torquesensor at the robot end-effector) and of the estimation of the equivalent interactingelastic system stiffness (i.e., force sensor - compliant gripper - compliant environmentequivalent stiffness) defining two control levels: (i) an internal impedance controllerwith inner position and orientation loop and (ii) an external impedance shaping forcetracking controller. A theoretical analysis of the method has been performed. Then, themethod has been experimentally validated in an industrial-like assembly task with tightmounting tolerances (i.e., H7/h6 mounting). A standard industrial robot (a UniversalRobot UR 10 manipulator) has been used as a test-platform, equipped with an externalforce/torque sensor Robotiq FT 300 at the robot end-effector and with a RobotiqAdaptive Gripper C-Model to manipulate target components. ROS framework has beenadopted to implement the proposed control architecture. Experimental results show theavoidance of force overshoots and the achieved target dynamic performance.