Multi-variable resonant controller for fast atomic force microscopy

This paper presents the experimental implementation of the multi-variable resonant control scheme with an integral action to compensate the vibration and the cross coupling effect between the axes of the piezoelectric tube scanner (PTS) in an atomic force microscope (AFM) for fast image scanning. The aim of the current work is to improve the high speed imaging performance of the AFM through multi-variable resonant control approach. The optimal parameter of the proposed control scheme has been chosen by minimizing the H₂ norm of the error transfer function between the desired plant model and the existing system closed-loop model. In order to justify the performance improvement of the proposed scheme, a comparison of the scanned images have been made between the proposed scheme and the open loop AFM system. The experimental results show that, by implementing the proposed scheme in the AFM, relatively good images can still be obtained up to 125 Hz.