共查询到20条相似文献,搜索用时 15 毫秒
1.
Kazuyuki Yagasaki 《Nonlinear dynamics》2017,87(4):2335-2343
External feedback control of microcantilevers was previously demonstrated to be one of promising techniques to develop high-performance noncontact atomic force microscopy, but it has a difficulty in reproducing oscillatory waveforms of fast vibrating microcantilevers. Here we propose an approach to overcome this difficulty by using approximate waveforms for vibrations of the cantilevers, instead of the actual ones, as control signals. The approximations are very simple and consist of the lowest frequency and constant components. We call the proposed technique, rough external feedback control, to distinguish it from the original one. The efficiency and validity of our approach are demonstrated by numerical simulations, and numerical bifurcation analyses are carried out. 相似文献
2.
Kazuyuki Yagasaki 《International Journal of Non》2007,42(4):658-672
We study the dynamics of a microcantilever in tapping mode atomic force microscopy when it is close to the sample surface and the van der Waals force has an important influence. Utilizing the averaging method, the extended version of the subharmonic Melnikov method and the homoclinic Melnikov method, we show that abundant bifurcation behavior and chaotic motions occur in vibrations of the microcantilever. In particular, in the subharmonic Melnikov analyses, a degenerate resonance is treated appropriately. Necessary computations for the subharmonic and homoclinic Melnikov methods are performed numerically. Numerical bifurcation analyses and numerical simulations are also given to demonstrate the theoretical results. 相似文献
3.
On the dynamics of tapping mode atomic force microscope probes 总被引:1,自引:0,他引:1
A?mathematical model is developed to investigate the grazing dynamics of tapping mode atomic force microscopes (AFM) subjected to a base harmonic excitation. A?multimode Galerkin approximation is utilized to discretize the nonlinear partial differential equation of motion governing the cantilever response and associated boundary conditions and obtain a set of nonlinearly coupled ordinary differential equations governing the time evolution of the system dynamics. A?comprehensive numerical analysis is performed for a wide range of the excitation amplitude and frequency. The tip oscillations are examined using nonlinear dynamic tools through several examples. The non-smoothness in the tip/sample interaction model is treated rigorously. A?higher-mode Galerkin analysis indicates that period doubling bifurcations and chaotic vibrations are possible in tapping mode microscopy for certain operating parameters. It is also found that a single-mode Galerkin approximation, which accurately predicts the tip nonlinear responses far from the sample, is not adequate for predicting all of the nonlinear phenomena exhibited by an AFM, such as grazing bifurcations, and leads to both quantitative and qualitative errors. 相似文献
4.
The nonlinear dynamical behavior of a single-mode model of noncontact AFM is analyzed in terms of attractors robustness and basins integrity. The model considered for the analyses, proposed in (Hornstein and Gottlieb in Nonlinear Dyn. 54:93–122, 2008), consistently includes the nonlinear atomic interaction and is studied under scan excitation (which appears as parametric excitation) and vertical excitation (which is prevalently external). Local bifurcation analyses are carried out to identify the overall stability boundary in the excitation parameter space as the envelope of system local escapes, to be compared with the one obtained via numerical simulations. The dynamical integrity of periodic bounded solutions is studied, and basin erosion is evaluated by means of two different integrity measures. The obtained erosion profiles allow us to dwell on the possible lack of homogeneous safety of the stability boundary in terms of robustness of the attractors, and to identify practical escape thresholds ensuring an a priori design safety target. 相似文献
5.
《Acta Mechanica Solida Sinica》2017,(5)
Timoshenko beam model is employed to investigate the vibration of atomic force microscope(AFM)cantilevers in contact resonance force microscopy(CRFM).Characteristic equation with both vertical and lateral tip-sample contact is derived.The contact resonance frequencies(CRFs)obtained by the Timoshenko model are compared with those by the Euler-Bernoulli model.A method is proposed to correct the wave number obtained by the Euler-Bernoulli model.The forced vibration is compared between the two models.Results reveal that the Timoshenko model is superior to the Euler-Bernoulli model in predicting the vibration characteristics for cantilevers’higher eigenmodes. 相似文献
6.
Nonlinear dynamics of a regenerative cutting process 总被引:1,自引:0,他引:1
We examine the regenerative cutting process by using a single degree of freedom nonsmooth model with a friction component and a time delay term. Instead of the standard Lyapunov exponent calculations, we propose a statistical 0-1?test analysis for chaos detection. This approach reveals the nature of the cutting process signaling regular or chaotic dynamics. For the investigated deterministic model, we are able to show a transition from chaotic to regular motion with increasing cutting speed. For two values of time delay showing the different response, the results have been confirmed by the means of the spectral density and the multiscaled entropy. 相似文献
7.
Hendrik Hölscher 《International Journal of Non》2007,42(4):608-625
The present text reviews the fundamentals of amplitude-modulation atomic force microscopy (AM-AFM), which is frequently also referred to as dynamic force microscopy, non-contact atomic force microscopy, or “tapping mode” AFM. It is intended to address two different kinds of readerships. First, due to a thorough coverage of the theory necessary to explain the basic features observed in AM-AFM, it serves theoreticians that would like to gain overview on how nanoscale cantilevers interacting with the surrounding environment can be used to characterize nanoscale features and properties of suitable sample surfaces. On the other hand, it is designed to introduce experimentalists to the physics underlying AM-AFM measurements to a degree that is not too specialized, but sufficient to allow them measuring the quantities they need with optimized imaging parameters.More specifically, this article first covers the basics of the various driving mechanisms that are used in AFM imaging modes relying on oscillating cantilevers. From this starting point, an analytical theory of AM-AFM is developed, which also includes the effects of external resonance enhancement (“Q-Control”). This theory is then applied in conjunction with numerical simulations to various situations occurring while imaging in air or liquids. In particular, benefits and drawbacks of driving exactly at resonance frequency are examined as opposed to detuned driving. Finally, a new method for the continuous measurement of the tip-sample interaction force is discussed. 相似文献
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按照非线性理论,实施了犬的深低温停循环(Profound Hypothermia and Circulatory Arrest,简称PHCA)实验,并应用混沌理论对实验中采集的心电信号进行了研究,得出以下结论:(1)混沌特征参数可反映心脏的总体动态特征,并可作为心血管疾病早期诊断的依据。(2)在正常的生理状态下心脏的运动是混沌的,而在病理状态下则趋于有序。 相似文献
10.
Yieh -Hei Wan 《Archive for Rational Mechanics and Analysis》1990,112(1):83-95
Communicated by
P. Holmes 相似文献
11.
Nonlinear dynamics and control for single-axis gyroscope systems 总被引:1,自引:0,他引:1
A nonlinear feedback control system of the single-axis gyroscope governed by a servo motor is studied in this paper. The closed-loop feedback is designed to account for the gimbal nutation as the gyroscope undergoing an angular velocity in the perpendicular directions. This paper integrates the singular perturbation modeling technology and sliding mode control strategy, while the stability of the closed-loop system is ensured by proof via Lyapunov direct method. Finally, comparisons among pole placement, sliding mode control and angular displacement feedback with respect to regulation capability and transient performance are reported. The simulation results demonstrate the superiority of singular perturbation sliding mode control and its potential to be facilitated in the aircraft safety module on detection and prevention from rollover during flight. 相似文献
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13.
Nonlinear Dynamics - 相似文献
14.
We consider the stochastic dynamics of an array of two closely spaced atomic force microscope cantilevers in a viscous fluid for use as a possible biomolecule sensor. The cantilevers are not driven externally, as is common in applications of atomic force microscopy, and we explore the stochastic cantilever dynamics due to the constant buffeting of fluid particles by Brownian motion. The stochastic dynamics of two adjacent cantilevers are correlated due to long range effects of the viscous fluid. Using a recently proposed thermodynamic approach the hydrodynamic correlations are quantified for precise experimental conditions through deterministic numerical simulations. Results are presented for an array of two readily available atomic force microscope cantilevers. It is shown that the force on a cantilever due to the fluid correlations with an adjacent cantilever is more than 3 times smaller than the Brownian force on an individual cantilever. Our results indicate that measurements of the correlations in the displacement of an array of atomic force microscopes can detect piconewton forces with microsecond time resolution. 相似文献
15.
A new microtensile tester for the study of MEMS materials with the aid of atomic force microscopy 总被引:4,自引:0,他引:4
An apparatus has been designed and implemented to measure the elastic tensile properties (Young's modulus and tensile strength)
of surface micromachined polysilicon specimens. The tensile specimens are “dog-bone” shaped ending in a large “paddle” for
convenient electrostatic or, in the improved apparatus, ultraviolet (UV) light curable adhesive gripping deposited with electrostatically
controlled manipulation. The typical test section of the specimens is 400 μm long with 2 μm×50 μm cross section. The new device
supports a nanomechanics method developed in our laboratory to acquire surface topologies of deforming specimens by means
of Atomic Force Microscopy (AFM) to determine (fields of) strains via Digital Image Correlation (DIC). With this tool, high
strength or non-linearly behaving materials can be tested under different environmental conditions by measuring the strains
directly on the surface of the film with nanometer resolution. 相似文献
16.
J. Pouget 《Meccanica》1995,30(5):449-458
With the view of understanding how precise macroscopic properties of a material emerge from the underlying physics of homogeneous microstructures, a lattice model which can describe complex non-linear patterns made of elastic domains and interfaces is proposed. On the basis of a two-dimensional lattice model involving non-linear and competing interactions the dynamics of microstructure formation is examined. The emphasis is placed especially on an instability mechanism of a strain band producing localized domains. The influence of applied forces and dissipative effects on the dynamics of two perpendicular strain bands is studied. The results are interpreted as a microtwinning in crystalline alloys. The physical conjectures are checked by means of numerical simulations performed directly on the microscopic system.
Sommario Si propone un modello reticolare che può descrivere complessi arrangiamenti fatti di domini elastici ed interfacce. Sulla base di un modello bidimensionale in cui sono presenti interazioni contrastanti e nonlineari si esamina la dinamica della formazione di microstrutture. L'accento è posto sui meccani'smi di instabilità che determinano bande di deformazione localizzata. Si studia l'influenza delle forze applicate e degli effetti dissipativi sulla dinamica di due bande perpendicolari e si interpretano i risultati come un microtwinning in leghe cristalline. Si verificano le congetture fisiche per mezzo di simulazioni numeriche del modello microscopico.相似文献
17.
Nonlinear Dynamics - Atomic force microscope (AFM) is one of the most versatile and powerful devices capable of producing high-resolution images of nanomaterial. Many researchers are widely... 相似文献
18.
The present paper reports some interesting phenomena observed in the nonlinear dynamics of two self-excitedly coupled harmonic oscillators. The system under consideration consists of two mechanical oscillators coupled by the Rayleigh type self-exciting force. Both autonomous and nonautonomous cases for weakly coupled systems are analyzed. When the natural frequencies of the two oscillators are close to each other, only one mode of oscillation exists. As two modes of oscillations get locked to a single mode, the system is said to be in a mode-locked condition. Under a mode-locked condition, the oscillators can oscillate with only a single frequency. However, when two oscillators are sufficiently detuned, the mode-locking condition does not persist and two distinct modes of oscillations emerge. Under these circumstances, particularly when detuning is large, one of the oscillators, depending on the initial conditions, oscillates with much larger amplitude as compared to the other oscillator, and hence mode localization is observed. When one of the oscillators is subject to a harmonic excitation, at two different frequencies, termed here as the decoupling frequencies, the coupling between the oscillators is almost lost, resulting in almost zero response of the unexcited oscillator. Analytical and numerical results are presented to analyze the above mentioned phenomena. Some potential applications of the aforesaid phenomena are also discussed. 相似文献
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20.
József Kövecses László L. Kovács Gábor Stépán 《Archive of Applied Mechanics (Ingenieur Archiv)》2007,77(5):293-299
This paper investigates the dynamic behavior of robotic echanical systems with discrete-time force control. Force control
is associated with the constrained motion of a mechanical system. A novel approach is presented to analyze the stability and
performance based on the separation of constrained and admissible motions. This results in a model representing the dynamics
of the constrained motion of the system. The analysis connects the complex nonlinear model of a mechanical system to a set
of abstract delayed oscillators. These oscillator models make it possible to perform a detailed closed-form mathematical analysis
of the stability behavior. A planar two-degree-of-freedom (DoF) mechanism is presented as an example to illustrate the material.
Results are illustrated by stability charts in the parameter space of mechanical parameters, control gains and the sampling
rate. 相似文献