Constant force feedback controller design using fuzzy technique for a tapping mode Atomic Force Microscope

A constant force feedback mechanism based on fuzzy logic for a tapping mode atomic force microscope is proposed in this paper. A nonlinear dynamic model for characterizing the cantilever-sample interaction is first developed. Then, a PD-like fuzzy controller is designed to overcome the shortcomings of a traditional PID controller in a tapping mode atomic force microscope. By using the PD-like fuzzy controller, the cantilever tip can track the surface of the sample rapidly and accurately even though the topology of the surface is arbitrary and not given a priori. The rapid tracking response allows us to observe high aspect ratio microstructure accurately and quickly. In final, a computer simulation is provided to demonstrate the effectiveness and confirm validity of the proposed controller.