The Experts below are selected from a list of 3351 Experts worldwide ranked by ideXlab platform
Mohamed Belhaq - One of the best experts on this subject based on the ideXlab platform.
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contact Stiffness Modulation in contact mode atomic force microscopy
International Journal of Non-linear Mechanics, 2013Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:Abstract The effect of fast contact Stiffness Modulation on the frequency response in contact-mode atomic force microscopy is studied analytically near primary resonance. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the contact-mode dynamics between the tip of the microbeam and the sample. Averaging method and perturbation analysis are performed to obtain the Modulation equations of the slow dynamic. The influence of the contact Stiffness Modulation on the non-linear characteristic of the frequency response is examined. We find that the amplitude of the contact Stiffness Modulation influences significantly the amplitude of the tip oscillation as well as the shift direction of the frequency response indicating that such a Modulation can be used to characterize the local elastic properties of the sample. Comparison between the analytical predictions and the numerical simulations is given and application to a real atomic force microscope example is provided.
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effect of contact Stiffness Modulation in contact mode afm under subharmonic excitation
Communications in Nonlinear Science and Numerical Simulation, 2013Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:We report on the effect of fast contact Stiffness Modulation on frequency response to 2:1 subharmonic resonance in contact-mode atomic force microscopy. The model of the contact-mode dynamic between the tip of the microbeam and the moving surface consists of a lumped single degree of freedom Hertzian contact oscillator. Perturbation methods are applied to obtain the frequency response of the slow dynamic of the system. We focus on the effect of the amplitude and the frequency of the Modulation on the nonlinear characteristic of the contact Stiffness, the jump phenomenon and the shift in the frequency response of the subharmonic. We also show the effect of the contact Stiffness Modulation on the interval of the unstable trivial solution which is directly correlated to the depth of the jump. The obtained results can directly influence the material properties and the loss of contact between the tip and the sample.
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frequency shift and hysteresis suppression in contact mode afm using contact Stiffness Modulation
MATEC Web of Conferences, 2012Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:In this paper the frequency response shift and hysteresis suppression of contact-mode atomic force microscopy is investigated using parametric Modulation of the contact Stiffness. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the cantilever dynamics contact- mode atomic force microscopy. We use the technique of direct partition of motion and the method of multiple scales to obtain, respectively, the slow dynamic and the corresponding slow flow of the system. As results, this study shows that the amplitude of the contact Stiffness Modulation has a significant effect on the frequency response. Specifically, increasing the amplitude of the Stiffness Modulation suppresses hysteresis, decreases the peak amplitude and produces shifts towards higher and lower frequencies.
Ilham Kirrou - One of the best experts on this subject based on the ideXlab platform.
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contact Stiffness Modulation in contact mode atomic force microscopy
International Journal of Non-linear Mechanics, 2013Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:Abstract The effect of fast contact Stiffness Modulation on the frequency response in contact-mode atomic force microscopy is studied analytically near primary resonance. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the contact-mode dynamics between the tip of the microbeam and the sample. Averaging method and perturbation analysis are performed to obtain the Modulation equations of the slow dynamic. The influence of the contact Stiffness Modulation on the non-linear characteristic of the frequency response is examined. We find that the amplitude of the contact Stiffness Modulation influences significantly the amplitude of the tip oscillation as well as the shift direction of the frequency response indicating that such a Modulation can be used to characterize the local elastic properties of the sample. Comparison between the analytical predictions and the numerical simulations is given and application to a real atomic force microscope example is provided.
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effect of contact Stiffness Modulation in contact mode afm under subharmonic excitation
Communications in Nonlinear Science and Numerical Simulation, 2013Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:We report on the effect of fast contact Stiffness Modulation on frequency response to 2:1 subharmonic resonance in contact-mode atomic force microscopy. The model of the contact-mode dynamic between the tip of the microbeam and the moving surface consists of a lumped single degree of freedom Hertzian contact oscillator. Perturbation methods are applied to obtain the frequency response of the slow dynamic of the system. We focus on the effect of the amplitude and the frequency of the Modulation on the nonlinear characteristic of the contact Stiffness, the jump phenomenon and the shift in the frequency response of the subharmonic. We also show the effect of the contact Stiffness Modulation on the interval of the unstable trivial solution which is directly correlated to the depth of the jump. The obtained results can directly influence the material properties and the loss of contact between the tip and the sample.
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frequency shift and hysteresis suppression in contact mode afm using contact Stiffness Modulation
MATEC Web of Conferences, 2012Co-Authors: Ilham Kirrou, Mohamed BelhaqAbstract:In this paper the frequency response shift and hysteresis suppression of contact-mode atomic force microscopy is investigated using parametric Modulation of the contact Stiffness. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the cantilever dynamics contact- mode atomic force microscopy. We use the technique of direct partition of motion and the method of multiple scales to obtain, respectively, the slow dynamic and the corresponding slow flow of the system. As results, this study shows that the amplitude of the contact Stiffness Modulation has a significant effect on the frequency response. Specifically, increasing the amplitude of the Stiffness Modulation suppresses hysteresis, decreases the peak amplitude and produces shifts towards higher and lower frequencies.
Massimo Ruzzene - One of the best experts on this subject based on the ideXlab platform.
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time periodic Stiffness Modulation in elastic metamaterials for selective wave filtering theory and experiment
Physical Review Letters, 2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Yiwei Xia, Massimo RuzzeneAbstract:Elastic waveguides with time-modulated Stiffness feature a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the Modulation frequency and over a finite wave number range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a nonmodulated medium and a time-modulated one, which converts a broadband input into a narrow-band output centered at the half Modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where Modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. The switching schedule defines the Modulation frequency and allows the selection of the output frequency. This implementation is suitable for the investigation of numerous properties of time-space modulated elastic metamaterials, such as nonreciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.
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time periodic Stiffness Modulation in elastic metamaterials for selective wave filtering theory and experiment
Physical Review Letters, 2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Massimo RuzzeneAbstract:We report on broadband-to-narrowband elastic wave filtering resulting from time-periodic Modulation of the Stiffness of a one-dimensional elastic waveguide. Time Modulation produces flat dispersion bands at frequencies that are multiple integers of half the Modulation frequency. These flat bands lead to the selective reflection of a broadband incident wave at the interface between a non-modulated medium, and one with time-modulated Stiffness properties. This results from the vanishing group velocity at the flat band frequencies, which prevents their propagation into the modulated domain. Thus, the considered modulated waveguide is understood as a single port system, in which a broadband incident wave (input) results in a narrowband reflected wave (output) at a frequency defined by Modulation. The appearance of the flat bands for a time-modulated waveguide is here illustrated analytically and through numerical simulations. The filtering characteristics of a non-modulate/modulated interface are observed experimentally by implementing a square-wave Modulation scheme that employs an array of piezoelectric patches bonded to an elastic waveguide subject to transverse motion. The patches are shunted through a negative electrical capaticance that, when connected, implements a Stiffness reduction for the resulting electromechanical waveguide. Switching the capacitance on and off effectively modulates the Stiffness of the waveguide, and illustrates the filtering characteristics associated with time-Modulation of the equivalent elastic properties. We envision that a similar approach could be extended to investigate other properties of time-modulated elastic metamaterials, such as non-reciprocity and one-way filtering of elastic waves.
David J. Braun - One of the best experts on this subject based on the ideXlab platform.
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Variable Stiffness Spring Actuators for Low-Energy-Cost Human Augmentation
IEEE Transactions on Robotics, 2019Co-Authors: David J. Braun, Vincent Chalvet, Tze-hao Chong, Salil S. Apte, Neville HoganAbstract:Theoretical studies suggest and experimental evidence confirms that maintaining and changing human joint Stiffness by coactivated antagonistic muscles are metabolically expensive, even if muscles do not perform net mechanical work. Based on this observation, we posit that effective human augmentation can be achieved by actuators operated in parallel to human joints, even if these actuators only supplement joint Stiffness without doing net mechanical work. In this article, we present a prototype variable-length leaf-spring actuator capable of large-range Stiffness Modulation. The key feature of the actuator is that it provides intrinsically low-energy-cost Stiffness Modulation even for large output deflection, by keeping the force on the driving motor low. Variable Stiffness actuators use two motors to provide both Stiffness and equilibrium position Modulation as they are designed to do net mechanical work. The proposed actuator conceptually differs from variable Stiffness actuators because first, it uses a single motor to only provide Stiffness Modulation, second, it does not provide equilibrium position Modulation, and third, unless externally loaded, it cannot do net mechanical work. Using this actuator, we demonstrate Stiffness augmentation during human-machine collaboration in challenging postural stabilization and weight-bearing tasks. Our results indicate that the proposed actuator can be used to complement a biological system by restoring or extending its functionality with low energy cost, and that variable Stiffness spring actuators could effectively augment humans by doing no or a limited amount of mechanical work.
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Criterion for the Design of Low-Power Variable Stiffness Mechanisms
IEEE Transactions on Robotics, 2017Co-Authors: Vincent Chalvet, David J. BraunAbstract:Designing robotic systems capable of low-power operation, inherent to their compliant actuation, has been elusive in practical application. In this paper, we propose a physical measure to mathematically define mechanical designs that are suitable to realize Stiffness Modulation with low power cost. Using this measure, we present a mathematical formulation of an ideal variable Stiffness mechanism unaffected by the external load during its operation. We then analyze several existing mechanisms from the literature to relate design features with analytical conditions inherent to low power Stiffness Modulation in practical designs. Through this analysis, we identify an approximate practical realization of an ideal actuator capable of Stiffness Modulation with inherently low power cost. Similar to a number of existing efficient variable Stiffness mechanisms, this mechanism is able to hold a given Stiffness setting with zero input force under no external load. However, unlike many other previously designed mechanisms, it enables infinite range Stiffness Modulation using finite control forces. A practical variable Stiffness mechanism that is capable of infinite range Stiffness Modulation using finite control forces leads to lower power cost and reduced energy consumption.
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exploiting variable physical damping in rapid movement tasks
International Conference on Advanced Intelligent Mechatronics, 2012Co-Authors: Andreea Radulescu, David J. Braun, Matthew Howard, Sethu VijayakumarAbstract:Until now, design of variable physical impedance actuators (VIAs) has been limited mainly to realising variable Stiffness while other components of impedance shaping, such as damping, are either fixed (e.g., with the addition of fixed passive dampers) or modulated with active feedback control schemes. In this work we introduce an actuator that is capable of simultaneous and independent physical damping and Stiffness Modulation. Using optimal control techniques, we explore how variable physical damping can be exploited in such an actuator in the context of rapid movement. Several numerical simulation results are presented, in addition to an experiment realised on variable impedance robotic hardware.
Giuseppe Trainiti - One of the best experts on this subject based on the ideXlab platform.
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time periodic Stiffness Modulation in elastic metamaterials for selective wave filtering theory and experiment
Physical Review Letters, 2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Yiwei Xia, Massimo RuzzeneAbstract:Elastic waveguides with time-modulated Stiffness feature a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the Modulation frequency and over a finite wave number range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a nonmodulated medium and a time-modulated one, which converts a broadband input into a narrow-band output centered at the half Modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where Modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. The switching schedule defines the Modulation frequency and allows the selection of the output frequency. This implementation is suitable for the investigation of numerous properties of time-space modulated elastic metamaterials, such as nonreciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.
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time periodic Stiffness Modulation in elastic metamaterials for selective wave filtering theory and experiment
Physical Review Letters, 2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Massimo RuzzeneAbstract:We report on broadband-to-narrowband elastic wave filtering resulting from time-periodic Modulation of the Stiffness of a one-dimensional elastic waveguide. Time Modulation produces flat dispersion bands at frequencies that are multiple integers of half the Modulation frequency. These flat bands lead to the selective reflection of a broadband incident wave at the interface between a non-modulated medium, and one with time-modulated Stiffness properties. This results from the vanishing group velocity at the flat band frequencies, which prevents their propagation into the modulated domain. Thus, the considered modulated waveguide is understood as a single port system, in which a broadband incident wave (input) results in a narrowband reflected wave (output) at a frequency defined by Modulation. The appearance of the flat bands for a time-modulated waveguide is here illustrated analytically and through numerical simulations. The filtering characteristics of a non-modulate/modulated interface are observed experimentally by implementing a square-wave Modulation scheme that employs an array of piezoelectric patches bonded to an elastic waveguide subject to transverse motion. The patches are shunted through a negative electrical capaticance that, when connected, implements a Stiffness reduction for the resulting electromechanical waveguide. Switching the capacitance on and off effectively modulates the Stiffness of the waveguide, and illustrates the filtering characteristics associated with time-Modulation of the equivalent elastic properties. We envision that a similar approach could be extended to investigate other properties of time-modulated elastic metamaterials, such as non-reciprocity and one-way filtering of elastic waves.