On automating atomic force microscopes: an adaptive control approach

The atomic force microscope (AFM) requires the user to manually tune controller gains and scan parameters in a trial and error fashion for different sample cantilever combinations. In this paper, steps towards automating this process are presented. Modeling and experimental results are shown revealing the structure of AFM dynamics and how it is impacted by different choices of scan and controller parameters. A robust adaptive controller is designed to address these issues. The performance of the designed adaptive controller is verified by simulating scanning experiments. The adaptive controller eliminates the need for the user to manually tune controller gains for different sample cantilever combinations and compensates for uncertainties arising from the user choice of different scan parameters. In addition, a substantial reduction in contact force and retrace line setpoint error can be achieved with the adaptive controller in comparison with a well-tuned integral controller.