Integration of Control Design and System Operation of a High Performance Piezo-Actuated Fast Steering Mirror

This article presents a novel piezo-actuated fast steering mirror (FSM) and focuses on the integration of control design and system operation in order to improve its tracking performance for high-speed scanning. The FSM is centered around a membrane-like flexure design and two pairs of stack actuators operated in a push-pull configuration, employing an optical sensor for position measurement. With the flexure membrane, the first fundamental resonance mode is placed as high as 6.7 kHz, while still enabling an angular range of $\pm$2.4 mrad mechanical. This results in the highest performance metric given by the product of mechanical range times main resonance mode frequency reported for piezo FSMs so far. To improve the tracking performance under high-speed scanning compared to a conventional raster scan operation, an integrated control and trajectory design yields a Lissajous trajectory together with tailored single tone and dual tone feedback controllers. It is demonstrated that in the Lissajous scan case, the rms tracking error can be reduced by one order of magnitude, as compared to the conventional raster scan case with a PI+ controller providing a closed-loop bandwidth of 2.7 kHz.