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Nonlinear and Chaos Control in Atomic Force Microscopy

In this project, the active chaos control of AFM systems is studied. It is known that chaotic phenomena have been observed in numerous fields of science such as physics, chemistry, biology, and ecology. The existence of chaotic behavior in AFM is highly undesirable for its bad effects on the system since this type of complex irregular motion causes the AFM to give inaccurate measurements and low resolution of the achieved sample topography. Atomic force microscopy (AFM) has been widely used for surface inspection with nanometer resolution in engineering applications and fundamental research, since the time of its invention, 1986. An Atomic Force Microscopic can be properly described by a sinusoidal excitation of its base and nonlinear potential interaction with sample. Thus the cantilever may cause chaotic behavior as the system is a non‐autonomous second order with high nonlinearity function. Based on Poincare map of the system, its maximum Lyapunov exponents and via Bifurcation diagram one may find the stability and chaotic regions of such system. In order to suppress such irregularity, a controller is designed to stabilize the system on its working manifold. Firstly, assuming some lumped parameters and continuous models the nonlinear and chaotic behavior of AFM systems is investigated. Then by presenting some control methods such as DFC and sliding mode control the first order Unstable Periodic Orbits (UPOs) of the system is stabilized. Proposed controllers were modified to implement in assumed dynamical models. A GUI C# code was developed to show the validity of the designed controllers.

Type of Seminar:
IfA Seminar
Hoda Sadeghian
in Sharif University of Technology, Tehran. Iran
Jan 14, 2008   14:00 /

ETL K 25
Contact Person:

Prof. John Lygeros
No downloadable files available.
Biographical Sketch:
I am currently doing my M.Sc thesis on nonlinear control of chaos in AFM systems. My B.Sc thesis was also about modeling and controlling chaos in Electrical circuits.