Closing the loop: High-speed visual servoing and control of a commercial nanostage inside the SEM

In micro- and nanorobotics, it is important to increase closed-loop performance to achieve high-throughput for industrial applications. By using dedicated line scans instead of scanning microscope image acquisition, bottlenecks such as limited update rate, long latency and unpredictable jitter can be overcome. Earlier experiments used the line-scan approach for visual servoing of a custom made mobile robot. In this paper, the line-scan approach is used to guide the closed loop positioning of a Physik Instrumente (PI) nanostage. Additionally to the linescan controller and the commercial PI-stage controller, an FPGA system that acts as additional position controller was developed. Several evaluation measurements show the performance of the implementation in terms of accuracy and performance for the nanorobotic stage.