<title>Design for visually guided microassembly</title>

Abstract

Development of hybrid MEMS devices has demonstrated a need for automatic microassembly strategies. Visual servoing techniques have shown great promise as a control strategy capable of sub-micron precision while compensating for many of the problems that exist in the micro domain, including thermal expansion of assembly devices and imprecisely modeled and calibrated sensors and actuators. This project develops rules for micropart design to aid in device assemblability with visual servoing techniques by ensuring that the microparts can be easily tracked and controlled using vision feedback. A criterion is presented that estimates part trackability based on the visual appearance of the part. This criterion is then used to microfabricate features to improve part trackability and hence, the assemblability of the device. The criterion considers the feature appearance when the part lies out of the optical systems's depth-of-field. A Fourier optics based approach is used to simulate the visual appearance of microparts represented by CAD models using high resolution optical systems. This simulation is used to automatically design microfabricated features on microparts. These features are used to estimate the tracking accuracy of the MEMS parts to subpixel levels using interpolation techniques in optical flow based tracking. This allows MEMS parts to be assembled with sub-micron precisions using visual servoing strategies. Results demonstrating the capabilities of our design-for- microassembly rules using visual servoing microassembly strategies are presented.