Anti-saturation surface topography observer for amplitude modulation atomic force microscope

This paper addresses the development of amplitude modulation atomic force microscopes (AM-AFM). The output of the AM-AFM is obtained from amplitude demodulation of the excited cantilever tip position. Thus, when the amplitude of the cantilever tip position is zero or maximum value, the output will be saturated. The output saturation prevents disturbance suppression. In this paper, the anti-saturation surface topography observer which improves the output saturation is proposed. The proposed method estimates the unsaturated output and uses it for the feedback loop. Finally, effectiveness of a proposed method is shown by simulation and experimental results.