3,158 research outputs found
Synchronization of Micromechanical Oscillators Using Light
Synchronization, the emergence of spontaneous order in coupled systems, is of
fundamental importance in both physical and biological systems. We demonstrate
the synchronization of two dissimilar silicon nitride micromechanical
oscillators, that are spaced apart by a few hundred nanometers and are coupled
through optical radiation field. The tunability of the optical coupling between
the oscillators enables one to externally control the dynamics and switch
between coupled and individual oscillation states. These results pave a path
towards reconfigurable massive synchronized oscillator networks
Duffing revisited: Phase-shift control and internal resonance in self-sustained oscillators
We address two aspects of the dynamics of the forced Duffing oscillator which
are relevant to the technology of micromechanical devices and, at the same
time, have intrinsic significance to the field of nonlinear oscillating
systems. First, we study the stability of periodic motion when the phase shift
between the external force and the oscillation is controlled -contrary to the
standard case, where the control parameter is the frequency of the force.
Phase-shift control is the operational configuration under which self-sustained
oscillators -and, in particular, micromechanical oscillators- provide a
frequency reference useful for time keeping. We show that, contrary to the
standard forced Duffing oscillator, under phase-shift control oscillations are
stable over the whole resonance curve. Second, we analyze a model for the
internal resonance between the main Duffing oscillation mode and a
higher-harmonic mode of a vibrating solid bar clamped at its two ends. We focus
on the stabilization of the oscillation frequency when the resonance takes
place, and present preliminary experimental results that illustrate the
phenomenon. This synchronization process has been proposed to counteract the
undesirable frequency-amplitude interdependence in nonlinear time-keeping
micromechanical devices
Harmonic vibration synchronization phenomenon analysis of dual excitation rotors nonlinear vibration system
Based on the electromechanical coupling nonlinear dynamic model of nonlinear vibration system that driven by dual excitation rotors, the theoretical analysis of the harmonic vibration synchronization conditions for dual excitation rotors have been conducted at the balance singularity of the nonlinear vibration system. And the harmonic vibration synchronization phenomena of dual excitation rotors in nonlinear vibration system have also been quantitatively analyzed and interpreted. Under different parameter conditions, the validity of the harmonic vibration synchronization theoretical research has been verified by the numerical simulation and practical application experiments. And research results also demonstrate that with certain systemic characteristic conditions, the harmonic vibration synchronization movement phenomenon of dual excitation rotors could realize because of the harmonic vibration response of nonlinear vibration system. But the harmonic vibration synchronization phenomena only occur at certain order ratio of p/q. Compared to the frequency multiplication harmonic vibration synchronization and fractional frequency harmonic vibration synchronization, the prime harmonic vibration synchronization of dual excitation rotors is much easier to implement. The research of this paper can used to provide the theoretical basis and experiment support for the design and application of this kind of high-efficiency, energy-saving nonlinear vibration machine that driven by multiple excitation rotors, in vibration application engineering technical field
Amplitude and frequency control of a vibratory pile driver
Abstract—This paper describes the digital control of a vibratory pile driver in which the vibration is generated via two tandem pairs of electrically driven, geared, contra-rotating eccentrics. Experimental results are included to show the controller-induced system dynamics for a variety of load condtions, and to highlight the fact that, if the relative phase of the eccentric pairs is not controlled, the
natural tendency at high excitation frequency is for the pile driver to operate with a low vibration amplitude. An analytical technique for identifying the system parameters is presented, and analytical performance predictions are compared with experimental results. Analysis of the power flow in the system shows that, although significant
power transfer occurs between the two electrical drives,
the net power dissipation during pile driving is relatively low
Synchronization of van der Pol oscillators with delayed coupling
The synchronization of self-sustained oscillators such as the van der Pol oscillator is a model for the adjustment of rhythms of oscillating objects due to their weak interaction and has wide applications in natural and technical processes. That these oscillators adjust their frequency or phase to an external forcing or mutually between several oscillators is a phenomenon which can be used in sound synthesis for various purposes. In this paper we focus on the influence of delays on the synchronization properties of these oscillators. As there is no general theory yet on this topic, we mainly present simulation results, together with some background on the non-delayed case. Finally, the theory is also applied in Neukom’s studies 21.1-21.9
Vortex-induced vibration of catenary riser: reduced-order modeling and lock-in analysis using wake oscillator
A new reduced-order model capable of analyzing the vortex-induced vibration of catenary riser in the ocean current has been developed. This semi analytical-numerical approach is versatile and allows for a significant reduction in computational effort for the analysis of fluid-riser interactions. The incoming current flow is assumed to be steady, uniform, unidirectional and perpendicular to the riser plane of initial equilibrium curvatures
Nonlinear multi-mode interactions in subsea risers undergoing vortex-induced vibrations
This paper investigates nonlinear multi-mode interactions in subsea risers undergoing vortex-induced vibrations based on a computationally efficient reduced-order fluid-structure interaction model. Cross-flow responses as a result of a steady uniform current are considered. The geometrically nonlinear equations of riser motion are coupled with nonlinear wake oscillators which have been modified to capture the effect of initial curvatures of curved cylinder and to approximate the space-time varying hydrodynamic lift forces. The main objectives are to provide new insights into the vortex-induced vibration characteristics of risers under external and internal resonances and to distinguish nonlinear dynamic behaviors between curved catenary and straight toptensioned risers. The analyses of multi-mode contributions, lock-in regimes, response amplitudes, resonant nonlinear modes and curvatures are carried out and several interesting aspects are highlighted
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