Calibration Strategies for a Manipulation Work-Cell

The paper introduces an experimental setup for the automatic manipulation of microcomponents, based on a 4 dof robot with Shoenflies motion and a two-camera vision system. The general architecture of the work-cell is presented. The work-cell functionality was tested via repeatability experiments using a set of vacuum grippers. Due to their intrinsic simplicity, vacuum grippers are very cheap and appear a promising solution for micromanipulation. An innovative nozzle for a vacuum gripper was designed, fabricated and tested, comparing its performance with traditional needles. The design was conceived to reduce the frequency of occlusions of the gripper and handle a wide range of particles. The performed tests evaluate the success and precision of the part release. Indeed, this is a crucial aspect of micromanipulation because microparts tend to stick to the gripper preventing the successful performance of manipulation tasks. The results confirm that adhesive effects prevent the release of components. For this reason different strategies were adopted in order to improve the efficiency in the release of stuck components. This solution increases the percentage of release and, setting appropriately the intensity of the pressure, it does not affect negatively the accuracy nor the repeatability of the positioning.