Two-Stage Robotic Bin Picking of Small Metallic Objects

Abstract Robotic grasping of small metallic objects such as bolts is a challenging task due to the small dimensions and textureless reflective surfaces. Depth images acquired of such objects are often noisy and error-prone. In addition, overlapping of parts occur as they are provided randomly oriented in a box such as a small load carrier. To overcome the limitations of existing solutions for bolt separation, a flexible and cost-effective system is developed using an industrial robot and a magnetic gripper. In a two-stage procedure, the bolts are first grasped blindly from a box and placed on a flat surface. In the second step, object detection and pose estimation is performed and the individual bolts are grasped and inserted into a fixture, so that finally the bolts are in a defined position. Industrial use cases for this system are the automated preparation of bolts for robotic screwing processes or automated commissioning of small objects for assembly tasks. The methodology, implementation and evaluation of the proposed solution is presented in this paper.