Computational Investigation of the Effect of Atomic Thermal Fluctuations on the Stick-Slip Motion in Friction Force Microscopy

Friction force microscopy (FFM) enables the unprecedented measurement of friction at the nanoscale. It is known that when FFM microcantilevers are dragged across surface, the nanometer tip executes stick-slip motions as the tip “plucks” individual atoms on the surface. Tomlinson’s model is usually used to explain these effects. In what follows we investigate the effects of tip compliance on the stick-slip motions in FFM. New results are predicted describing the transition from steady sliding to single and multiple atom stick-slip. Additionally, the effect of these different motions on the average frictional force is calculated.

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Observer-based friction force estimation for brake system under low-frequency vibration

Journal of Vibration and Control ◽

10.1177/10775463211000496 ◽

2021 ◽

pp. 107754632110004

Author(s):

Lu Qian ◽

Xingwei Zhao

Keyword(s):

Friction Force ◽

Low Frequency ◽

Brake System ◽

Estimation Methods ◽

Force Estimation ◽

Stick Slip ◽

Modeling Methods ◽

Low Frequency Vibration ◽

Stick Slip Motion ◽

Slip Motion

Creep groan is a low-frequency vibration, which is produced by the stick–slip motion from the pad–disc contact in the brake. Friction plays a key role in generating the stick–slip motion. However, directly measuring the friction force in an actual brake system is difficult. Therefore, force estimation methods are proposed to estimate the friction force based on unknown input observers. A proportional integral observer is applied to estimate the friction force amplitude from the torsional angle of the driven shaft. An approximate H2 observer is designed to distinguish the stick region and slip region from the acceleration of the pad. Different from modeling methods, designing observers do not introduce modeling deviation and have a relatively low requirement on parameter identification. In addition, the observer methods can extract more detailed information of friction force than modeling methods. The observed friction force can be considered an index to evaluate the severity of the brake defect. The performance and effectiveness of the proposed methods are confirmed by experiments on a brake test rig.

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Modulation of contact resonance frequency accompanying atomic-scale stick–slip in friction force microscopy

Nanotechnology ◽

10.1088/0957-4484/20/49/495701 ◽

2009 ◽

Vol 20 (49) ◽

pp. 495701 ◽

Cited By ~ 13

Author(s):

Pascal Steiner ◽

Raphael Roth ◽

Enrico Gnecco ◽

Thilo Glatzel ◽

Alexis Baratoff ◽

...

Keyword(s):

Resonance Frequency ◽

Friction Force ◽

Atomic Scale ◽

Friction Force Microscopy ◽

Stick Slip ◽

Force Microscopy ◽

Contact Resonance

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Effects of friction models on simulation of pneumatic cylinder

Mechanical Sciences ◽

10.5194/ms-10-517-2019 ◽

2019 ◽

Vol 10 (2) ◽

pp. 517-528

Author(s):

Xuan Bo Tran ◽

Van Lai Nguyen ◽

Khanh Duong Tran

Keyword(s):

Friction Force ◽

Servo System ◽

Pneumatic Cylinder ◽

Lugre Model ◽

Stick Slip ◽

Comparison Results ◽

Pneumatic Servo System ◽

Friction Models ◽

Stick Slip Motion ◽

Slip Motion

Abstract. This study examines effects of three friction models: a steady-state friction model (SS model), the LuGre model (LG model), and the revised LuGre model (RLG model) on the motion simulation accuracy of a pneumatic cylinder. An experimental set-up of an electro-pneumatic servo system is built, and characteristics of the piston position, the pressures in the two-cylinder chambers and the friction force are measured and calculated under different control inputs to the proportional flow control valves. Mathematical model of the electro-pneumatic servo system is derived, and simulations are carried out under the same conditions as the experiments. Comparisons between measured characteristics and simulated ones show that the RLG model can give the best agreement among the three friction models while the LG model can only simulate partly the stick-slip motion of the piston at low velocities. The comparison results also show that the SS model used in this study is unable to simulate the stick-slip motion as well as creates much oscillations in the friction force characteristics at low velocities.

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A Mobile Mechanism With Slant Leg on a Vibratory Floor

Volume 6B: 18th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc2001/vib-21513 ◽

2001 ◽

Author(s):

Hideya Yamaguchi ◽

Masahito Yashima

Keyword(s):

Numerical Simulation ◽

Friction Force ◽

Coefficient Of Friction ◽

Stick Slip ◽

Main Mass ◽

Rotational Spring ◽

Exciting Frequency ◽

The Difference ◽

Stick Slip Motion ◽

Slip Motion

Abstract This paper investigates the characteristics of a mobile mechanism that consists of a main mass and a slant leg with a rotational spring at the joint. The device travels on an oscillating floor due to the difference in the friction force between forward and backward directions during the stick-slip motion. Numerical simulation and experimentation show that the direction and velocity of movement are controlled by the exciting frequency. Furthermore, the effects of the angle of the slant leg and the sliding coefficient of friction on those characteristics are investigated.

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