A robust loop-shaping approach to fast and accurate nanopositioning

• Robust control for fast and accurate raster scanning for atomic force microscopy.
• Piezoelectric nanoactuators.
• Hysteresis, creep, nonlinearities of piezoelectric actuators.

Inherent nonlinearities as well as their sharp lightly-damped resonant mode severely limit the positioning bandwidth of commercially available piezoelectric stack actuated nanopositioners. In this paper, we propose a hybrid control scheme that incorporates a H∞-based loop-shaping control scheme for resonance damping and an integral control for tracking. Experimental raster scans recorded in both open-loop and closed-loop operation are presented to show the substantial increase in positioning performance achieved by the implemented control scheme. It is also shown that the control scheme is robust under relatively large changes in platform resonance, an effect of platform loading.