Servoing Mechanisms for Peg-In-Hole Assembly Operations

Image-based effector servoing is a process of perception-action cycles for handling a robot effector under continual visual feedback. Apart from the primary goal of manipulating objects we apply servoing mechanisms also for determining camera features, e.g. the optical axes of cameras, and for actively changing the view, e.g. for inspecting the object shape. A peg-in-hole application is treated by a 6-DOF manipulator and a stereo camera head. The two robot components are mounted on separate platforms and can be steered independently. In the first phase (inspection phase), the robot hand carries an object into the field of view of one camera, then approaches the object along the optical axis to the camera, rotates the object for reaching an optimal view, and finally inspects the object shape in detail. In the second phase (insertion phase), the system localizes a board containing holes of different shapes, determines the relevant hole based on the extracted object shape, then approaches the object, and finally inserts it into the hole. At present, the robot system has the competence to handle cylindrical and cuboid pegs. For treating more complicated objects the system must be extended with more sophisticated strategies for the inspection and/or insertion phase.