1,124 research outputs found
Suppression of Limit Cycle Oscillations using the Nonlinear Tuned Vibration Absorber
The objective of the present study is to mitigate, or even completely
eliminate, the limit cycle oscillations in mechanical systems using a passive
nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA). An
unconventional aspect of the NLTVA is that the mathematical form of its
restoring force is not imposed a priori, as it is the case for most existing
nonlinear absorbers. The NLTVA parameters are determined analytically using
stability and bifurcation analyses, and the resulting design is validated using
numerical continuation. The proposed developments are illustrated using a Van
der Pol-Duffing primary system
A principle of similarity for nonlinear vibration absorbers
This paper develops a principle of similarity for the design of a nonlinear
absorber, the nonlinear tuned vibration absorber (NLTVA), attached to a
nonlinear primary system. Specifically, for effective vibration mitigation, we
show that the NLTVA should feature a nonlinearity possessing the same
mathematical form as that of the primary system. A compact analytical formula
for the nonlinear coefficient of the absorber is then derived. The formula,
valid for any polynomial nonlinearity in the primary system, is found to depend
only on the mass ratio and on the nonlinear coefficient of the primary system.
When the primary system comprises several polynomial nonlinearities, we
demonstrate that the NLTVA obeys a principle of additivity, i.e., each
nonlinear coefficient can be calculated independently of the other nonlinear
coefficients using the proposed formula
Nonlinear Generalization of Den Hartog's Equal-Peak Method
This study addresses the mitigation of a nonlinear resonance of a mechanical
system. In view of the narrow bandwidth of the classical linear tuned vibration
absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber
(NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is
that the mathematical form of its restoring force is tailored according to the
nonlinear restoring force of the primary system. The NLTVA parameters are then
determined using a nonlinear generalization of Den Hartog's equal-peak method.
The mitigation of the resonant vibrations of a Duffing oscillator is considered
to illustrate the proposed developments
Performance, robustness and sensitivity analysis of the nonlinear tuned vibration absorber
The nonlinear tuned vibration absorber (NLTVA) is a recently-developed
nonlinear absorber which generalizes Den Hartog's equal peak method to
nonlinear systems. If the purposeful introduction of nonlinearity can enhance
system performance, it can also give rise to adverse dynamical phenomena,
including detached resonance curves and quasiperiodic regimes of motion.
Through the combination of numerical continuation of periodic solutions,
bifurcation detection and tracking, and global analysis, the present study
identifies boundaries in the NLTVA parameter space delimiting safe, unsafe and
unacceptable operations. The sensitivity of these boundaries to uncertainty in
the NLTVA parameters is also investigated.Comment: Journal pape
Coexisting attractors in floating body dynamics undergoing parametric resonance
This study pertains to analysing the dynamical behaviour of a floating body undergoing parametric resonances. A simple vertical cylinder, representing a classical spar-buoy, is considered, limiting its motion to heave and pitch degrees of freedom. Its geometry and mass distribution are chosen such that a 2:1 ratio of heave to pitch/roll natural frequency makes the spar-buoy prone to parametric resonance. The system is then studied by the shooting method, combined with a pseudo-arclength continuation, and the harmonic balance procedure. Results show that an extensive bistable region exists, where stable parametric resonance coexists with a regular resonance response. The analysis also unveiled the existence of stable quasiperiodic motions existing in correspondence of both pitch and heave resonance. Results are qualitatively validated using a model based on the explicit nonlinear Froude–Krylov force calculation
analytical investigation of single and double neimark sacker bifurcations
The analytical investigation of bifurcations is a very challenging task for many applied scientists and engineers. Often, numerical simulations cannot clarify the complicated dynamics of mechanical systems, in this cases, preprogrammed softwares can be of valid help during the investigation. Also, in the literature, methodology to study bifurcations are presented for most of the cases. However, the presented procedures, are often very hard to be understood from applied scientists with low mathematical background. In this paper we present in details the typical procedure to analyze single and double Neimark-Sacker bifurcations. Especially regarding the double Neimark-Sacker bifurcations of maps, very few sources can be found in the literature, although this kind of bifurcation is very common in many dynamical systems
Passive Linearization of Nonlinear System Resonances
In this work we demonstrate that the addition of properly-tuned nonlinearities to a nonlinear system can increase the range over which a specific resonance responds linearly. Specifically, we seek to enforce two important properties of linear systems, namely the force-displacement proportionality and the invariance of resonance frequencies. Theoretical findings are validated through numerical simulations and experiments
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