Fusing force and vision feedback for micromanipulation

In this paper we present experimental results that investigate the integration of two disparate sensing modalities, force and vision, for sensor-based microassembly. By integrating these sensing modes, we are able to provide feedback in a task-oriented frame of reference over a broad range of motion with an extremely high precision. An optical microscope is used to provide visual feedback down to micron resolutions. We have developed an optical beam deflection sensor (based on a modified atomic force microscope) to provide nanonewton level force feedback or nanometric level position feedback. The value of integrating these two disparate sensing modalities is demonstrated during controlled micropart impact experiments. Using force feedback alone to control micropart contact transitions, impact forces of over 140nN were generated before the desired contact force of 2nN was achieved When visual servoing is integrated with the force control framework, micropart impact forces of only 9nN and final contact forces of 2nN were easily achieved.