Improvement of accuracy and speed of a commercial AFM using Positive Position Feedback control

Mahmood, Iskandar Al-Thani and Moheimani, S.O. Reza (2009) Improvement of accuracy and speed of a commercial AFM using Positive Position Feedback control. In: American Control Conference, 10 - 12 June 2009, Hyatt Regency Riverfront, St. Louis, MO, USA.

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Abstract

The atomic force microscope (AFM) is a device capable of generating topographic images of sample surfaces with extremely high resolutions down to the atomic level. It is also being used in applications that involve manipulation of matter at a nanoscale. Early AFMs were operated in open loop. As a result, they were susceptible to piezoelectric creep, thermal drift, hysteresis nonlinearity and scan-induced vibration. These effects tend to distort the generated image. The distortions are often minimized by limiting the scanning speed and range of the AFMs. Recently a new generation of AFMs has emerged that utilizes position sensors to measure displacements of the scanner in three dimensions. These AFMs are equipped with feedback loops that work to minimize the adverse effects of hysteresis, piezoelectric creep and thermal drift on the obtained image using standard PI controllers. These feedback controllers are often not designed to deal with the highly resonant nature of an AFM's scanner, nor with the cross-coupling between various axes. In this paper we illustrate the drastic improvement in accuracy and imaging speed that can be obtained by proper design of a feedback controller. Such controllers can be incorporated into most modern AFMs with minimal effort since they can be implemented in software with the existing hardware.

Item Type:	Conference or Workshop Item (Full Paper)
Additional Information:	3614/5305 (ISBN: 9781424445240)
Uncontrolled Keywords:	atomic force microscope; feedback controllers design; feedback loops; hysteresis nonlinearity; open loop; piezoelectric creep; position sensors; positive position feedback control;scan-induced vibration;standard PI controllers; thermal drift; topographic images; PI control; atomic force microscopy; control system synthesis; feedback; position control;
Subjects:	Q Science > Q Science (General) T Technology > TJ Mechanical engineering and machinery > TJ212 Control engineering
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Engineering > Department of Mechatronics Engineering
Depositing User:	Dr. Iskandar Al-Thani bin Mahmood
Date Deposited:	31 Oct 2011 16:39
Last Modified:	31 Oct 2011 16:39
URI:	http://irep.iium.edu.my/id/eprint/5305

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