Electromechanical Oscillator Research Articles

Dynamics and energy harvesting from parametrically coupled self-excited electromechanical oscillator

The investigated parametrically coupled electromechanical structure is composed of a mechanical Duffing oscillator whose mass sits on a moving belt surface. The driving electrical network is a van der Pol oscillator whose aim is to actuate the attached DC motor to provide some rotatry unbalances and parametric coupling in the vibrating structure. The coupled oscillator is applied to energy harvesting and overcomes the limitation of low energy generation associated with a single oscillator of this kind. The system was solved analytically and validated by numerical methods. The global dynamics of the structure were investigated, and nonlinear phenomena such as Neimark–Sacker bifurcation, discontinuity-induced bifurcation, grazing–sliding, and bifurcation to multiple tori were identified. These nonlinear behaviors affect the harvested energy at bifurcation points, resulting in jumps from one energy level to another. In addition to harnessing the highest energy under hard parametric coupling, the coupling ensures that higher and more useful energy is harvested over a wider range of belt speeds. Finally, the qualitative validation of the numerical concept by experimental setup verifies the workings of the model.

Use of computer vision to analyze cyclic loads on the Guamo sand

Some effects have been evidenced during several earthquakes around the world. For example, the liquefaction phenomenon, and structural collapse, among others. However, granular soil behaviour during this event has not been completely understood; this is proved by the number of investigations in physical models, constitutive models, and laboratory testing proposals about this topic. A question appears at this point: when do the effects take place? To cope with this issue, it is proposed to create an experimental model composed of a Single Degree of Freedom Oscillator (SDOFO) designed to try to assess the liquefaction. Likewise, the device could transmit cyclic loadings to the soil. This SDOFO was an electromechanical oscillator servo-controlled appropriated to manage the frequency of excitation and amplitude of the oscillatory movement. The measurement methodology was based on computer vision using Open CV by Python, which allowed measuring displacements and times of the SDOFO instead of using LVDT sensors located directly at the actuator; thus, computer vision permitted a “free movement” of the actuator similar to the actual behavior of buildings in seismic events. The samples required for this study were the Guamo sand collected in a natural deposit in Colombia (South America) and the Ottawa sand to compare results. A simple criterion was used to try to determine the possible liquefaction onset. It was defined based on the evolution of displacements relying on the number of cyclical loads. According to the results, it was able to define that the relationship between the excitation frequency, the amplitude of the oscillatory movement, and the number of cycles required to reach the possible liquefaction state was inverse.

Droplet-on-chip electro-spectroscopy detects the ultra-short relaxation time of a dilute polymer solution.

We report an electrode-embedded on-chip platform technology for the precise determination of ultra-short (of the order of a few nanoseconds) relaxation times of dilute polymer solutions, by deploying time-alternating electrical voltages. Our methodology delves into the sensitive dependence of the contact line dynamics of a droplet of the polymer solution atop a hydrophobic interface in response to the actuation voltage, resulting in a non-trivial interplay between the time-evolving electrical, capillary, and viscous forces. This culminates into a time-decaying dynamic response that mimics the features of a damped oscillator having its 'stiffness' mapped with the polymeric content of the droplet. The observed electro-spreading characteristics of the droplet are thus shown to correlate explicitly with the relaxation time of the polymer solution, drawing analogies with a damped electro-mechanical oscillator. By corroborating well with the reported values of the relaxation times as obtained from more elaborate and sophisticated laboratory set-ups. Our findings provide perspectives for a unique and simple approach towards electrically-modulated on-chip-spectroscopy for deriving ultra-short relaxation times of a broad class of viscoelastic fluids that could not be realized thus far.

Identification-based Adaptive Tracking Control of Uncertain Bistable Electromechanical Duffing Oscillator

Identification-based Adaptive Tracking Control of Uncertain Bistable Electromechanical Duffing Oscillator

Experimental Investigation and Empirical Analysis of a Shape-Memory-Alloy-Actuated Electromechanical Oscillator

Experimental Investigation and Empirical Analysis of a Shape-Memory-Alloy-Actuated Electromechanical Oscillator

Dynamics of a discontinuous coupled electro-mechanical system oscillator with strong irrational nonlinearities and with two outputs

The dynamics of the nonlinear electromechanical device, consisting of a mechanical part with two outputs and an electrical part which acts as the server is strongly investigated in the present work. The mechanical part consists of two nonlinear oscillators with strong irrational nonlinearities having smooth or discontinuous characteristics, where nonlinearity is just due to the inclination of springs, the geometric configuration, which are both elastically coupled. While the electrical part is the Rayleigh equation. By using the Lagrangian formulation, the model equations are established and used to investigate the equilibrium points and their stabilities. Nest by using the multiple time scales method, the analytical solutions are found both for the case of large amplitude and the weak amplitude, leading to interesting bifurcation sets of the equilibria by varying the control parameters, the inclination angles and driven frequency. Finally, numerical investigations of the exact equation of the system are used to justify the validity of analytical results and to find new phenomena such as chaotic impulses, chaotic bursting and the train of kink signal generations.

Dynamics of a discontinuous coupled electro-mechanical system oscillator with strong irrational nonlinearities and with two outputs

Dynamics of a discontinuous coupled electro-mechanical system oscillator with strong irrational nonlinearities and with two outputs

Towards One-Dollar Robots: An Integrated Design and Fabrication Strategy for Electromechanical Systems

SUMMARYTo improve the accessibility of robotics, we propose a design and fabrication strategy to build low-cost electromechanical systems for robotic devices. Our method, based on origami-inspired cut-and-fold and E-textiles techniques, aims at minimizing the resources for robot creation. Specifically, we explore techniques to create robots with the resources restricted to single-layer sheets (e.g., polyester film) and conductive sewing threads. To demonstrate our strategy’s feasibility, these techniques are successfully integrated into an electromechanical oscillator (about 0.40 USD), which can generate electrical oscillation under constant-current power and potentially be used as a simple robot controller in lieu of additional external electronics.

Experimental and Theoretical Investigation of an Oscillator with Collisions

The oscillations of a nonlinear electromechanical oscillator with elastic collisions have been studied. A theoretical model has been built around the equation of motion including an elastic force that is calculated in terms of the Hertz contact theory. It has been shown that an oscillator with collisions may exhibit bifurcations and stable-focus and limit-cycle attractors. Fourier filtration has been applied to analyze the spectral characteristics of signals.

Efficient harmonic oscillator chain energy harvester driven by colored noise

We study the performance of an electromechanical harmonic oscillator chain as an energy harvester to extract power from finite-bandwidth ambient random vibrations, which are modelled by colored noise. The proposed device is numerically simulated and its performance assessed by means of the net electrical power generated and its efficiency in converting the external noise-supplied power into electrical power. Our main result is a much enhanced performance, both in the net electrical power delivered and in efficiency, of the harmonic chain with respect to the popular single oscillator resonator. Our numerical findings are explained by means of an analytical approximation, in excellent agreement with numerics.

Study of a piezoelectric plate based self-sustained electric and electromechanical oscillator

This work deals with the electrical characterization of a piezoelectric plate and its use to generate self-sustained electrical and mechanical oscillations. An experimental frequency-impedance curve of the piezoelectric plate is obtained leading to the electric equivalent of the piezoelectric plate constituted of a capacitive branch in parallel with many RLC resonant branches. The values of the electric components for each branch are determined using the resonant and anti-resonant frequencies. It is demonstrated theoretically that these branches can be understood in terms of vibration modes of the plate; each of which has its own resonant frequency. It is then demonstrated theoretically and experimentally that putting the piezoelectric plate in series with a resistor presenting a nonlinear I − V characteristics having a negative slope, autonomous oscillations of the Van der Pol type can be observed. A theoretical development has led to the appearance of self-sustained periodic and mixed modes mechanical oscillations of the plate deflection.

Экспериментальное и теоретическое исследование осциллятора с соударениями

The results of a study of a nonlinear mechanical oscillator with elastic impacts are presented. The experiment was carried out using an electromechanical impact oscillator. The theoretical model is based on the equations of motion, taking into account the elastic force, which is calculated under the Hertz contact theory. It is shown that bifurcations and attractors of the “stable focus” and “limit cycle” types can occur for the impact oscillator. Fourier filtering was used to analyze the spectral characteristics of the signals.

A coherent nanomechanical oscillator driven by single-electron tunnelling.

A single-electron transistor embedded in a nanomechanical resonator represents an extreme limit of electron-phonon coupling. While it allows fast and sensitive electromechanical measurements, it also introduces backaction forces from electron tunnelling that randomly perturb the mechanical state. Despite the stochastic nature of this backaction, it has been predicted to create self-sustaining coherent mechanical oscillations under strong coupling conditions. Here, we verify this prediction using real-time measurements of a vibrating carbon nanotube transistor. This electromechanical oscillator has some similarities with a laser. The single-electron transistor pumped by an electrical bias acts as a gain medium and the resonator acts as a phonon cavity. Although the operating principle is unconventional because it does not involve stimulated emission, we confirm that the output is coherent. We demonstrate other analogues of laser behaviour, including injection locking, classical squeezing through anharmonicity, and frequency narrowing through feedback.

Synchrony in networks of Franklin bells

Abstract The Franklin bell is an electro-mechanical oscillator that can generate a repeating chime in the presence of an electric field. Benjamin Franklin famously used it as a lightning detector. The chime arises from the impact of a metal ball on a metal bell. Thus, a network of Franklin bells can be regarded as a network of impact oscillators. Although the number of techniques for analysing impacting systems has grown in recent years, this has typically focused on low-dimensional systems and relatively little attention has been paid to networks. Here we redress this balance with a focus on synchronous oscillatory network states. We first study a single Franklin bell, showing how to construct periodic orbits and how to determine their linear stability and bifurcation. To cope with the non-smooth nature of the impacts we use saltation operators to develop the correct Floquet theory. We further introduce a new smoothing technique that circumvents the need for saltation and that recovers the saltation operators in some appropriate limit. We then consider the dynamics of a network of Franklin bells, showing how the master stability function approach can be adapted to treat the linear stability of the synchronous state for arbitrary network topologies. We use this to determine conditions for network induced instabilities. Direct numerical simulations are shown to be in excellent agreement with theoretical results.

A controllable superconducting electromechanical oscillator with a suspended membrane

We fabricate a microscale electromechanical system, in which a suspended superconducting membrane, treated as a mechanical oscillator, capacitively couples to a superconducting microwave resonator. As the microwave driving power increases, nonmonotonic dependence of the resonance frequency of the mechanical oscillator on the driving power has been observed. We also demonstrate the optical switching of the resonance frequency of the mechanical oscillator. Theoretical models for qualitative understanding of our experimental observations are presented. Our experiment may pave the way for the application of a mechanical oscillator with its resonance frequency controlled by the electromagnetic and/or optical fields, such as a microwave-optical interface and a controllable element in a superqubit-mechanical oscillator hybrid system.

Nonlinear damping in energy harvesters driven by colored noise

We study the performance of an electromechanical oscillator as an energy harvester driven byfinite-bandwidth random vibrations under the influence of both a stiffness-type nonlinearity and anonlinear damping that has recently been found to be relevant in the dynamics of submicrometermechanical resonators. The device was numerically simulated and its performance assessed by meansof the net electrical power and the efficiency of the conversion of the supplied power by the noiseinto electrical power for exponentially correlated noise. We tune the parameters to achieve a goodperformance of the device for non-negligible amplitudes of the nonlinearity of the oscillator and thedamping.

Active vibration suppression of a nonlinear electromechanical oscillator system with simultaneous resonance

In this paper, we explored the nonlinear dynamics behavior and vibration suppression of a nonlinear electromechanical oscillator system under harmonic and parametric excitation. The model comprises of an electrical part coupled to mechanical part and displayed by a coupled nonlinear ordinary differential equations. The analytical up to second order approximate solutions are sought applying the method of multiple scales method. We utilized the time-series and method of averaging to analyze the response and stability of the solutions at the worst resonance cases. We checked the results of perturbation solution through numerical simulations and the effects of different system parameters have been reported. Comparison between analytical and numerical solutions is obtained. Also, the numerical results are obtained using MAPLE and MATLAB algorisms.

Inverse design of nonlinearity in energy harvesters for optimum damping

This paper presents the inverse design method for the nonlinearity in an energy harvester in order to achieve an optimum damping. A single degree-of-freedom electromechanical oscillator is considered as an energy harvester, which is subjected to a harmonic base excitation. The harvester has a limited throw due to the physical constraint of the device, which means that the amplitude of the relative displacement between the mass of the harvester and the base cannot exceed a threshold when the device is driven at resonance and beyond a particular amplitude. This physical constraint requires the damping of the harvester to be adjusted for different excitation amplitudes, such that the relative displacement is controlled and maintained below the limit. For example, the damping can be increased to reduce the amplitude of the relative displacement. For high excitation amplitudes, the optimum damping is, therefore, dependent on the amplitude of the base excitation, and can be synthesised by a nonlinear function. In this paper, a nonlinear function in the form of a bilinear is considered to represent the damping model of the device. A numerical optimisation using Matlab is carried out to fit a curve to the amplitude-dependent damping in order to determine the optimum bilinear model. The nonlinear damping is then used in the time-domain simulations and the relative displacement and the average harvested power are obtained. It is demonstrated that the proposed nonlinear damping can maintain the relative displacement of the harvester at its maximum level for a wide range of excitation, therefore providing the optimum condition for power harvesting.

A New Chaotic Electro-Mechanical Oscillator

In this paper, a new electro-mechanical chaotic oscillator is presented. The system is based on the motion of the metal tip of a beam in a double-well potential generated by two magnets, and works thanks to the vibrations generated in the flexible mechanical structure by two rotating coils that produce noise-like signals. As the source of vibration is internal, the system may be considered an autonomous oscillator. Chaotic motion is experimentally observed and verified with a mathematical model of the phenomenon.

Energy harvesting using parametric resonant system due to time-varying damping

In this paper, the problem of energy harvesting is considered using an electromechanical oscillator. The energy harvester is modelled as a spring-mass-damper, in which the dissipated energy in the damper can be stored rather than wasted. Previous research provided the optimum damping parameter, to harvest maximum amount of energy, taking into account the stroke limit of the device. However, the amount of the maximum harvested energy is limited to a single frequency in which the device is tuned. Active and semi-active strategies have been suggested, which increases the performance of the harvester. Recently, nonlinear damping in the form of cubic damping has been proposed to extend the dynamic range of the harvester. In this paper, a periodic time-varying damper is introduced, which results in a parametrically excited system. When the frequency of the periodic time-varying damper is twice the excitation frequency, the system internal energy increases proportionally to the energy already stored in the system. Thus, for certain parametric damping values, the system can become unstable. This phenomenon can be exploited for energy harvesting. The transition curves, which separate the stable and unstable dynamics are derived, both analytically using harmonic balance method, and numerically using time simulations. The design of the harvester is such that its response is close to the transition curves of the Floquet diagram, leading to stable but resonant system. The performance of the parametric harvester is compared with the non-parametric one. It is demonstrated that performances and the frequency bandwidth in which the energy can be harvested can be both increased using time-varying damping.