The Infinite Dimensional Control of Flexible Cantilevers in AFM Based Nanomanipulation

Atomic force microscopy (AFM) has been extensively used and AFM based nanomanipulation has also been studied for many years. But efficiency and accuracy of AFM based nanomanipulation are still major issues. In order to accurately control the tip position, which is important to prevent the tip from missing the objects, the deformation of cantilever has to be compensated or eliminated during manipulation. An active AFM probe is used to eliminate the deformation of cantilever by directly controlling the cantilever´s flexibility or rigidity during manipulation. In this paper, the active probe is modeled as an infinite dimensional system based on Euler-Bernoulli theory. A periodic-output-feedback (POF) controller is designed and simulations are carried out to optimize the parameters of the controller. The POF controller is implemented in a real time Linux system. Experimental results demonstrated the validity of infinite dimensional model and POF controller. Experimental results on nanomanipulation have also shown that the control accuracy of tip position is improved by using this controller of active probe.