Optimization of piezoelectrical actuators for fast scanning applications

摘要

Compared to conventional electromagnetic actuators e.g. voice coil devices, piezoactuators succeed in a wide spectrum of today's applications that require positioning with nm-accuracy, nm-reproducibility, sub-nm-step resolution and long-term stability even within the micron range. Additionally, piezoactuators show a high degree of electromechanical coupling, work abrasion-free, and show no measurable outgassing -they are UV and UHV compatible down to sub-uPa. They function down to almost zero Kelvin and are neither affected by magnetic field strengths, nor do they produce them. Due to their excellent behavior, piezoactuators are well suited for optical applications like fine cell tracking, beam deflection within ion-accelerators, beam shuttering in cryonic UHV spectrometers, sample positioning in UV environments et cetera. Additionally, piezoactuators respond at almost sonic velocities and generate pressure forces up to 100MPa. They are also well suited for optical scanning applications. However, when using piezoelectric positioning systems in the field of fast scanning applications, e.g. scanning microscopy, you have to regard application specific criteria. Generally the optimization of the piezoelectric geared stage has to result in the highest dynamic behavior together with excellent trajectory accuracy while maintaining the highest step resolution. Depending on scanning mode requirements, e.g. harmonic or step shape of motion, working frequency and applied load, the piezoelectric device's stiffness, inertia and robustness should be matched. Additionally state-of-the-art digital amplifiers allow in-situ configuration of controlling parameters, e.g. slew rate adjustment, PID-parameter modification and notch filtering.