Development of a large scanning-range atomic force microscope with adaptive complementary sliding mode controller

Atomic force microscopy (AFM) is a powerful technique to provide high resolution, three-dimensional data for measuring topography of samples. However, the scanning range of conventional AFM systems hardly exceeds hundreds of micrometers due to the piezoelectric actuation. In this research, we develop a large scanning-range AFM system with a z-scanner separated from the xy-scanner. The z-scanner actuated by piezoelectric stack provides high speed scanning and the homemade xy-scanner actuated by electromagnetic actuation is capable of 2 mm×2 mm large field positioning with 17 nm rms error. The overall AFM system consists of a commercial piezoelectric positioner, four sets of electromagnetic actuator, a monolithic parallel compliant mechanism, and an eddy current damper. Moreover, a compact disk/digital versatile disk pick-up-head (CD/DVD PUH) is applied to measure the amplitude of the cantilever. Furthermore, we design an adaptive complementary sliding mode controller to deal with the unknown parameters, unmodeled system uncertainties, and the external disturbances. Finally, preliminary experimental results demonstrate the capability of the proposed system.