Nonlinear dynamics and energy harvesting of a pendulum-inspired bistable triboelectric vibration energy harvester

With the progress of the micro-electromechanical technology, the systems self-powered by ambient vibration have become a focus in nonlinear dynamics. The concept of bistable electromagnetic vibration energy harvesters with auxiliary nonlinear oscillators was proposed through combination of a mass-spring-damper system with a bistable vibration energy harvester, and the mechanical model and control equations for this system were established, the dynamic responses of the bistable electromagnetic vibration energy harvester with a nonlinear oscillator under harmonic excitation were investigated with the parametrical changes of the mass ratio and the tuning ratio through numerical simulation. Then, in comparison with that on the bistable system with an auxiliary linear oscillator, the influence rule of the above changing parameters on the bistable electromagnetic vibration energy harvester with an auxiliary nonlinear oscillator, which would get into chaotic movement, was obtained, and the superiority of the one with an auxiliary nonlinear oscillator was demonstrated. Moreover, the optimal parameters for the bistable electromagnetic vibration energy harvester with an auxiliary nonlinear oscillator in continuous large-amplitude chaotic motion were given. These above results provide a theoretical basis for the research of bistable electromagnetic vibration energy harvesters.

Low reliability and high maintenance cost of using power and data cables are two main reasons motivating the application of the self-powered wireless sensors for structural health monitoring (SHM) systems in bridge structures. On the other hand, energy harvesting systems have been introduced as a solution for the current limitations of the batterypowered wireless sensors associated with the finite life-span of batteries and their replacements. The objective in this paper is to propose a new optimized nonlinear energy harvesting concept, namely Bistable Energy Harvesting (BEH) system, for smart SHM of bridge structures. In this study, a dynamic analysis of the energy harvesting system for cablesupported bridges subject to wind-induced vibration is carried out and the feasibility of the energy harvesting device is investigated. This paper presents efficient linear and nonlinear energy harvesting systems for wireless monitoring of long-span cable-supported bridges. It is shown that level of the extracted energy from such energy harvesting system is quite sufficient to supply energy for self-powered sensors of a bridge health monitoring system. This study is to promote the recent line of research on self-powered sensor networks for smart bridge monitoring being performed at the Florida International University.

Through a snap-through process, the bistable vibration energy harvester (EH) could undergo large amplitude motion and yield a large energy output. But realizing the transitions between the stable states is a prerequisite for high power output of the bistable piezoelectric EH. To explore the conditions under which the harvester could switch from one stable state to the other, a bistable vibration EH based on PVDF film and its analytical model are investigated. The mechanisms responsible and the transitions of the harvester between the stable states are derived. The relationship between the PVDF axial compression distance, the mass of the proof mass, the excitation frequency and the critical switching force is obtained. The numerical simulation analysis of the bistable vibration EH is conducted. The effects of the different design parameters on the output performance of the EH are analyzed. The boundary conditions for the PVDF beam to realize the transitions between the stable states are obtained. A prototype of a bistable vibration EH was fabricated and measured. When the excitation frequency is 14 Hz, the mass of the proof mass is 12 g, the axial compression distance of the PVDF beam is 0.2 mm, the EH’s RMS output voltage value is 4.2 V with the load resistance of 1 MΩ. The maximum output power of 22.85 μW is obtained at the load resistance of 0.7 MΩ. It is found that the excitation frequency of implementing the transitions between the stable states increases with increasing the axial compression distance of the PVDF beam. The characteristic experimental results are contrasted with the simulation analysis results, which prove the validity of the presented model.

With the development of micro electromechanical systems, many researchers focus their attention on nonlinear energy harvesting device. The stochastic equivalent linearization method is used to analyze an energy harvesting system under ambient noise. First, according to the bistability of beam axially loaded, a model of bistable nonlinear vibration energy harvester under the stochastic condition is proposed. A close-form approximation expression for the ensemble average of harvested power is derived and the numerical simulation of the system shows stochastic resonance. The results show that it is possible to optimally design system such that the harvest power is maximized for a given density or variance of random excitation.

In recent years, the energy harvester is becoming more and more diversified, its aim is to increase the output power, the model of bistable electromagnetic vibration energy harvester with an auxiliary nonlinear oscillator through combining the mass-spring-damper system and a conventional bistable electromagnetic vibration energy harvester is first proposed, the bistable, nonlinear and two degrees of freedom of the system are simultaneously achieved, and the dimensionless governing equations of the system are established. Building white noise excitation signal, the effects of noise intensity, mass ratio and frequency ratio to the dynamic behavior and root mean square power of the system are studied respectively by matlab numerical simulation, the influences of these changing parameters are obtained. The research results can provide a theoretical basis for the related researches of bistable electromagnetic vibration energy harvester system.

Performance and dynamics of a novel bistable vibration energy harvester with appended nonlinear elastic boundary

Practical asymmetry and its effects on power and bandwidth performance in bi-stable vibration energy harvesters

Research in broadband nonlinear piezoelectric energy harvesting has gained traction in recent years as resonant, linear harvesters do not operate optimally in dynamic environments. By placing a linear harvester in a symmetric magnetic field, a nonlinear restoring force allows the system to realize motion across two potential wells. Different levels of excitation enable the system to oscillate solely in one potential well, periodically across both potential wells, or aperiodically across both potential wells. Periodic interwell motion is considered desirable for nonlinear energy harvesting systems, however, coexistent attractors inhibit uniqueness of such a solution. The authors have previously shown that chaotic, aperiodic motion between potential wells can be optimized for improved energy harvesting. The technique applied a chaotic controller to stabilize a large amplitude periodic orbit within the chaotic attractor. This work considers the basins of attraction of the two concurrent attractors and applies an intermittent control law in which the system is perturbed from a chaotic, aperiodic interwell response into the desirable large amplitude, periodic, interwell response.

Broadband spring-connected bi-stable piezoelectric vibration energy harvester with variable potential barrier

In order to broaden the working frequency band of the piezoelectric energy harvester and improve the energy harvesting efficiency, a new two degree of freedom bistable piezoelectric vibration energy harvester is designed in this paper. It consists of a basic cantilever beam, a mass, a piezoelectric cantilever beam and magnets. The equivalent model of the system is established using lumped parameter method, and the two degree of freedom bistable motion equation is established considering the influence of electromechanical coupling. Using Matlab, the motion equation is calculated, and the curve of the system voltage with time and frequency is obtained. The voltage output characteristics of the system under bistable vibration and the influence of the stiffness and the mass of the basic cantilever beam on the output performance of the system are analyzed. Under the excitation of 0.3 g simple harmonics, the two degree of freedom bistable piezoelectric energy harvester is experimented using one-way frequency-increasing sweep. The results show that the maximum output voltage of the two resonance band of the energy harvester is 26 V and 13 V. Compared with the single degree of freedom bistable structure, the frequency band is widened by 10 Hz. In addition, reducing the stiffness of the basic cantilever beam and increasing the mass of mass block are all beneficial to broadening the working band of the harvester.

Multi-solution phenomena and nonlinear characteristics of tristable galloping energy harvesters with magnetic coupling nonlinearity

Numerical analysis and experimental validation of nonlinear broadband monostable and bistable energy harvesters

Equivalent damping and frequency change for linear and nonlinear hybrid vibrational energy harvesting systems

In this paper, numerical and experimental investigations of broadband random vibrational energy harvesting using monostable and bistable piezoelectric cantilevers are presented along with relative performance comparisons. Simulations and experiments reveal that a linear-monostable energy harvester can outperform its bistable counterpart for very low and relatively high random excitation levels. The bistable configuration generates more power only for a limited excitation intensity range slightly above the threshold of interwell oscillations. Under broadband stochastic excitation, a bistable energy harvester can potentially be preferred only if it is designed to operate at a known excitation intensity, otherwise using a monostable harvester is more robust and practical.

To improve the efficiency of vibration energy harvesting, a levitation magnet couple is introduced to the bi-stable energy harvester (BEH) to create a desired potential energy, by which the harvester’s response and output can be increased greatly. Compared to the classical BEH, the novel harvester has a lower potential barrier and a flatter bottom of its potential well, which can help increase the response and outputs. The experimental results show that the introduction of levitation magnet couple effectively extends the working frequency bandwidth of the harvester. The inter-well jump can be executed easily under weak stochastic excitations and the amplitude is larger than the classical one, even in the case of executing the same kind of intra-well oscillation. The experiments prove that the output voltage of the novel harvester outperforms the classical BEH over the whole intensity range. This study may provide a good guidance to improving the performance of bistable energy harvester.