Real‐Time Sliding Mode Observer Scheme for Shear Force Estimation in a Transverse Dynamic Force Microscope

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Asian Journal of Control, Vol. 19, No. 2, pp. 1-12, March 2017 Published online in Wiley Online Library (wileyonlinelibrary.com ABSTRACTThis paper describes a sliding mode observer scheme for estimation of the shear force affecting the cantilever in a Transverse Dynamic Force Microscope (TDFM). The vertically oriented cantilever is oscillated in the proximity to the specimen under investigation. The amplitude of oscillation of the cantilever tip is affected by these shear forces. They are created by the ordered-water layer above the specimen. The oscillation amplitude is therefore a measure of distance between the tip and the surface of the specimen. Consequently, the estimation of the shear forces provides useful information about the specimen characteristics. For estimating the shear forces, an approximate finite dimensional model of the cantilever is created using the method of lines. This model is subsequently reduced in terms of its order. An unknown input sliding mode observer has been used to reconstruct the unknown shear forces using only tip position measurements and the cantilever excitation. This paper describes the development of the sliding mode scheme and presents experimental results from the TDFM set up at the Centre for Nanoscience and Quantum Information (NSQI) at Bristol University.

State Estimation For An Agonistic‐Antagonistic Muscle System

“…Therefore, e = 0 for ≥ ⋆ = max{ ⋆ 1 , ⋆ 2 , ⋆ 3 }. According to [9,15], the injection signals v 12 , v 2 , and v 3 are employed to estimate Δ Φ , u 1 , and u 2 in (49), (50), (51), from whichΔ Φ → Δ Φ andû → u.…”

“…High gain observers can offer a high level of accuracy in estimating state variables and uncertainties [10,11]. Sliding mode observers exhibit similar performance in estimating state variables and unknown inputs [8,9,12,[19][20][21][22]. A recent work [20] studies sliding mode control in combination with fuzzy logic to deal with matched/unmatched uncertainties and external disturbances.…”

Real-Time Force Reconstruction in a Transverse Dynamic Force Microscope

“…For TDFMs, a theoretical framework is developed in [18], proposing a two-inputs-singleoutput model of the cantilever: one of the inputs is the known cantilever excitation, the other input is the unknown interaction shear force at the tip of the cantilever, and the output is the measurable cantilever oscillation motion in the complex scan medium. In particular, a suitable solution that estimates the interaction force using a sliding mode observer is discussed and analysed in [18], [19]. The recent work [19] succeeds in estimating the unknown shear-force input by processing practical data for specific points on the specimen using a separate data processing PC.…”

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“…With respect to the existing literature on observer design and control for DFIG machine , the present work features the following novelties: A sensor‐less controller avoiding the measurement of mechanical variables and flux sensor (costly sensors) and supporting a large variation of all system states‐variables , ensure MPPT objectives, a control of the flux norm to ensure a linear behaviour of the magnetic circuit of the DFIG, a control of the DC‐bus voltage to ensure a protection of the considered inverter and rectifier, the Power Factor Correction (PFC) to ensure a clean energy injection and a use of a nonlinear observer that can cover a large scale of states variables variations .…”