Robotic assembly of smartphone back shells with eye-in-hand visual servoing

Research concerning smartphone assembly has attracted increasing attention from the manufacturing industry. This paper presents an automatic back shell assembly system using real-time visual servoing in an eye-in-hand configuration. Look-then-move and look-and-move control approaches are sequentially proposed to handle distal and proximal assembly tasks, respectively. During distal assembly, binocular vision is employed to assist a robotic manipulator to locate and reconstruct the positions and orientations of a cellular phone and its back shell in the work space. After lifting the back shell up and then reaching the top of the cellular phone, there is no binocular field of view. A seemingly novel way of 3-D reconstruction by two uniocular fields of view of the two cameras is proposed. With the pair of monocular vision sensors, two monocular visual servo control laws are employed sequentially to perform the proximal assembly task autonomously. Based on the experimental results, the robotic manipulator can be driven to hold the back shell by a vacuum absorption device and position it precisely onto the smartphone to accomplish the automatic assembly task even if the vision system is only roughly calibrated. The proposed control approach for distal and proximal assembly appears to be efficient, flexible, and reliable for potential applications in industrial manufacturing.