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G. Schitter, W. Rijkée, N. Phan:
"Dual actuation for high bandwidth nano-positioning";
Talk: 2008 Conference on Decision and Control, Cancun (Mexico); 12-09-2008 - 12-11-2008; in: "Proceedings of the 2008 Conference on Decision and Control", (2008), 5176 - 5181.

The imaging speed of atomic force microscopes
(AFM) is limited by the bandwidth of the feedback loop to
measure the sample topography. In contact mode as well as
tapping mode operation, this feedback loop is crucial to control
and minimize the force between the probing tip and the sample,
which is done by controlling the vertical tip sample distance via
a piezo actuator. For fast imaging, control of the probe-sample
distance requires a high closed-loop bandwidth. To achieve this
goal without reducing the existing positioning range, a second,
high-bandwidth actuator is introduced to an existing AFM
setup. A model-based controller is designed and implemented
to improve the bandwidth of the primary feedback loop for
tapping mode and contact mode imaging. For highest imaging
bandwidth in contact mode, an accessory high-performance
controller is designed and implemented on the dual actuated
AFM system. The improved performance of the new controlsystem
is experimentally demonstrated.