Indirect force measurement system in a mechanical microgripper

Sensing the grasping force is crucial in microassembly processes. In contrast to commonly used expensive and fragile laser-based or piezoelectric sensors the authors present a diverse methodology based on an indirect force measurement without sensors while exploiting the present camera equipment. Therefore, a unique compliant 2D microgripper with a carefully developed amplification and pointing mechanism was designed and manufactured. The detection of the pointer via a camera allows the authors to differentiate between the free movement of the gripper and the contact with the object, and to determine the grasping force. The behavior of the gripper was first simulated numerically for the grasping of different sized pins and eventually investigated experimentally. The recorded video was being processed in real time by an object detection software. To eliminate distortion and parallax errors the visual system was subjected to a standard calibration. The simulated and the experimental results displayed satisfying coherence.