Calibration strategies for a micromanipulation work-cell

The paper presents and compares some calibration procedures used to calibrate a work-cell for micromanipulation of sub-millimetric objects by means of a variety of grippers. The experimental setup is based on a 4-degree-of-freedom robot, a vacuum gripping system and a two-camera vision system. Since the robot and the vision system have to cooperate within the same working area, a robot calibration, a camera calibration and a robot-camera georeferencing are required. Standard calibration methods result in a very onerous process at the microscale, thus non-conventional calibration strategies have been developed and implemented in the work-cell. This paper discusses the results obtained with the different approaches, analyzing performance and limitations. Moreover, since the microgripper can be affected by misalignment and orientation errors with respect to vertical rotational axis of the manipulator, a simple and agile kinematic calibration of the robot end-effector has been developed. The paper describes the method and shows the achieved improvements.