Vibration Energy Harvesting System Research Articles

A novel configuration for high power-output and highly efficient vibration energy harvesting

The most commonly used vibration energy harvesting system is the single-degree-of-freedom (SDOF) system. However, the power output of the SDOF system is limited by the mechanical damping ratio and the efficiency is only 50% at the maximal power output. In this paper, we modified the SDOF configuration by adding a spring in series with the energy transducer, which results in a configuration where a parallel energy-harvesting damper and inerter are in series with the spring, similar to the Maxwell model. The parameters of the proposed configuration are analyzed and optimized. The optimization results show the new configuration can produce many times more power output compared with the conventional SDOF system if the primary spring is relatively soft and the added spring is properly selected. In addition, the energy-harvesting efficiency can be significantly increased at the maximal power output. A lab experiment of backpack setup demonstrated 82% power increase and an efficiency of 83%. Lab test using a bridge vibration induced by freight train finds out that the proposed configuration can double the power output compared with the conventional SDOF system. With the augment of a simple spring, the proposed configuration disrupts the fundamental limit on the power and efficiency of the conventional SDOF energy-harvesting system, which opens a new perspective in the energy-harvesting field.

Experiment Investigation of Bistable Vibration Energy Harvesting with Random Wave Environment

The energy harvested from the renewable energy has been attracting a great potential as a source of electricity for many years; however, several challenges still exist limiting output performance, such as the package and low frequency of the wave. Here, this paper proposed a bistable vibration system for harvesting low-frequency renewable energy, the bistable vibration model consisting of an inverted cantilever beam with a mass block at the tip in a random wave environment and also develop a vibration energy harvesting system with a piezoelectric element attached to the surface of a cantilever beam. The experiment was carried out by simulating the random wave environment using the experimental equipment. The experiment result showed a mass block’s response vibration was indeed changed from a single stable vibration to a bistable oscillation when a random wave signal and a periodic signal were co-excited. It was shown that stochastic resonance phenomena can be activated reliably using the proposed bistable motion system, and, correspondingly, large-scale bistable responses can be generated to realize effective amplitude enlargement after input signals are received. Furthermore, as an important design factor, the influence of periodic excitation signals on the large-scale bistable motion activity was carefully discussed, and a solid foundation was laid for further practical energy harvesting applications.

Transverse Vibration Energy Harvesting of Double Elastic Steel

This study uses the piezoelectric technology to collect vibration energy from the fixed-fixed nonlinear elastic beams attached with the piezo-patch between the two ends. Both single elastic steel sheet (SESS) and double elastic steel sheet (DESS) systems are investigated and correlated. To simulate the power generation of the vibration energy harvester (VEH) of both the SESS and the DESS in different engineering elements, the simple harmonic external force generated by a shaker at the location of the piezo-patch is used as the source. With this, more vibration converted electric energy is derived from the transverse deformation and flapping from the DESS than the SESS beam. The equation of a nonlinear Euler–Bernoulli beam is coupled with the electric energy equation of the piezo-patch to simulate the SESS VEH system. The flapping force from the DESS VEH system can be considered the concentrated external load applied on the SESS beam model. The method of multiple scales (MOMS) is employed to analyze this nonlinear problem. The fixed points plots and the numerical results confirm this theory presented for the two beam systems, which can be used for evaluating similar engineering systems. Experiments are also performed in this study. The Taguchi method is used to analyze the optimum locations of the shaker and piezo-patch, as well as the confidence level of the factors. The method of nonlinear analysis presented in this study demonstrates its accuracy compared with the linear case. The transverse DESS VEH model proposed is proved to be feasible and more effective than the SESS system.

On the use of metasurface for Vortex-Induced vibration suppression or energy harvesting

This paper explores the use of metasurface in designing an aerodynamic system for potential vortex-induced vibration (VIV) suppression or energy harvesting. Four kinds of metasurface patterns are designed to decorate an ordinary cylinder bluff body for modifying its aerodynamic characteristics. A theoretical model is developed for the VIV system by describing the wake as a van der Pol oscillator. The aerodynamic parameters, i.e., the lift and drag coefficients, used in the theoretical model, are determined from three-dimensional CFD simulations. A wind tunnel experiment is conducted to validate the theoretical model and investigate the aerodynamic behaviors of the VIV systems with different bluff bodies. It is found that the metasurface pattern has a significant influence on the aerodynamic characteristics of the bluff body. Using different metasurface patterns to decorate the bluff body, the vortex-induced vibration of the system could be either enhanced or suppressed, compared with the baseline reference using an ordinary bluff body with a smooth surface. Furthermore, the vortex shedding processes are simulated to give further insights into the wake oscillating motions. The roles of the metasurface in suppressing or enhancing the vortex-induced vibration are reasonably explained: the existence of metasurfaces could alter the flow field around the bluff bodies and consequently the aerodynamic force. In addition, based on the validated theoretical model, it is learned from a parametric study that the power output reaches saturation when the electromechanical coupling strength is increased to a certain level. Therefore, piezoelectric transducers with moderate coupling coefficients are recommended for practical applications from the cost-effective perspective.

Multiple electrically tunable parametric resonances in a capacitively coupled electromechanical resonator for broadband energy harvesting

Parametric excitation (PE) has widely been employed as a method of mechanical pre-amplification in nonlinear vibration energy harvesting systems. However, despite their advantages, most current PE systems are limited to degenerate parametric operation within a narrow frequency band around the primary instability tongue. In this paper, we simulate and experimentally demonstrate a parametrically driven capacitive electromechanical resonator having multiple electrical degrees of freedom. Multiple modes allow for several frequency bands in which the electrical resonator is driven into nondegenerate (combination) parametric resonance (PR) in addition to degenerate resonance, thereby enabling operation over a broader range of frequencies while maintaining the same mechanical footprint. These frequency bands and PR thresholds are tunable by simply changing the electrical circuit parameters and PR can be achieved in the presence of high mechanical damping making the method more adaptable than purely mechanical approaches. Experimental results are extended by simulations indicating that proper selection of operating parameters can enable the merging of instability tongues to produce a broadband region of PR for elastic wave energy harvesting thereby obtaining superior performance when compared to an equivalent single degree of freedom PE energy harvester.

Leveraging circuit theory and nonlinear dynamics for the efficiency improvement of energy harvesting

We study the performance of vibrational energy harvesting systems with piezoelectric and magnetic inductive transducers, assuming the power of external disturbance concentrated around a specific frequency. Both linear and nonlinear harvester models are considered. We use circuit theory and equivalent circuits to show that a large improvement in both the harvested energy and the power efficiency is obtained, for linear systems, through a proper reactive modification of the load. For nonlinear systems, we use methods of nonlinear dynamics to derive analytical formulae for the output voltage, the harvested energy and the power efficiency. We show that also for the nonlinear case, the modified load significantly boosts the performance.

Digital Evaluation Algorithm for Upper Limb Motor Function Rehabilitation Based on Micro Sensor

The electroencephalogram (EEG) of the cerebral cortex reflects the upper limb motion control information of the human body. The electro myographic signal (EMG) of the body muscle tissue reflects the response of the upper limb muscle to the brain control. The intersection of two physiological electrical signals has become a new hot field in artificial intelligence, medical rehabilitation and neuroscience. Firstly, starting with the analysis of the power consumption characteristics of the micro-sensor system, by studying the working principle and design scheme of the energy self-capture technology, various energy supply methods of the combined vibration energy harvesting system, the thermoelectric energy harvesting system and the RF energy harvesting system are proposed. Combined upper limb exercise rehabilitation energy is self-capture program. Secondly, the upper limb motor EEG and EMG signal acquisition experiments were designed to preprocess the acquired signals. Based on the wavelet threshold denoising method, an improved threshold algorithm is proposed to remove the noise in the EEG signal and improve the signal-to-noise ratio of the EEG signal. On the basis of the wavelet analysis method, the stratified threshold denoising method is applied to the collected EMG signals for denoising processing and digital evaluation of upper limb motor function rehabilitation. Finally, a digital evaluation method for upper limb motor function rehabilitation combined with wavelet low-frequency coefficients and significant information is proposed. The algorithm combines wavelet transform, motion estimation, and significant information to design a video quality evaluation algorithm. It can be seen from the experimental results that the performance of this algorithm is superior and maintains high consistency with the human motion system.

Power–bandwidth–voltage interaction in piezoelectric vibration energy harvesters with constrained load voltage

This paper analyzes the power–bandwidth–voltage interaction in a piezoelectric vibration energy harvester (PVEH) system, specifically accounting for the operating voltage constraint imposed by the interface power electronics (PE). The analysis is sufficiently generic to apply to different linear PVEHs with their interface PE. The power–bandwidth–voltage relation derived here outlines the best possible PVEH system performance when the PVEH-PE interface voltage is constrained, as is often the case in IoT applications. Alternatively, it can serve as a figure of merit with which to benchmark the performance of existing PVEH systems, and identify best design practices.

Probabilistic response of a fractional-order hybrid vibration energy harvester driven by random excitation.

The stochastic response of a fractional-order hybrid vibration energy harvester is investigated in this paper. Equivalent system can be derived by the variable transformation. Then, the probability density functions of mechanical states are obtained by the stochastic averaging technique. The good agreement between numerical simulation and analytical results demonstrates the effectiveness of the proposed method. Mean square voltage, mean square current, and mean output power are presented to illustrate the device output performance. Results imply that the hybrid vibration energy harvesting system can generate higher mean output power than that from a separate piezoelectric system and an electromagnetic system.

Static and dynamic analysis of a bistable plate under nonlinear magnetic force

In this article, bistable laminates are statically and dynamically studied under the existence of nonlinear magnetic force. The bistable laminates with magnetic forces are considered as a nonlinear system for vibration energy harvesting. First, a semi-analytical model was established based on the energy approach for the bistable plate together with magnets. The magnetic force versus distance was measured, and then, an equation was fitted to the experimental data. The damping of the whole system was determined experimentally, and Rayleigh damping coefficients were extracted and used in all models. Next, a finite element model of the whole system was developed to compute the dynamic response of the system under different base excitations. Finally, a test rig was constructed, and the system responses were measured under various base excitations. The dynamic snap-through of the bistable laminate under magnetic forces was also measured and compared with the results obtained from the semi-analytical and finite element model. The analysis shows that adding a magnetic force will reduce the amplitude of base excitation that is needed for dynamic snap-through for %28.6. The analysis shows that the bistable plate with a magnetic force can be a good candidate for energy harvesting because the nonlinear magnetic forces under certain conditions reduce the snap-through force and consequently increase the harvested energy. This is because of the fact that the presence of the magnetic forces allows the system to vibrate between its two stable configurations under lower base excitation amplitudes.

Adaptive damping tuning and circuit implementation for broad bandwidth energy harvesting

This paper presents a circuit to tune the electrical damping for optimal power harvesting at time varying excitation frequencies. Optimization of parameters, such as electrical damping to match the mechanical damping and the resonant frequency to match the excitation frequency have long been known. However, the electrical damping optimized at the resonant frequency is not necessarily the optimum point when the excitation frequency changes. This result is especially important in vibration energy harvesting systems since the vibration source is generally not at a single fixed frequency. The proposed circuit detects the excitation frequency and tunes the electrical damping based on a function, obtained from mechanical system modeling and simulation. A frequency detection circuit and a boost converter operating in critical conduction mode are used. Both modeling and experiment results show that the impedance tuning circuit provides the required optimal damping at different excitation frequencies and achieves a much broader bandwidth compared with the conventional system. When the excitation frequency increases to 1.1–1.4 times the natural frequency, the proposed adaptive damping tuning increases the power output by 30%–100% compared to the traditional one.

IMPACT-BASED PIEZOELECTRIC ENERGY HARVESTING SYSTEM EXCITED FROM DIESEL ENGINE SUSPENSION

Vibration energy harvesting systems are using real ambient sources of vibration excitation. In our paper, we study the dynamical voltage response of the piezoelectric vibrational energy harvesting system (PVEHs) with a mechanical resonator possessing an amplitude limiter. The PVEHs consist of the cantilever beam with a piezoelectric patch. The proposed system was subjected to the inertial excitation from the engine suspension. Impacts of the beam resonator are useful to increase of system’s frequency transition band. The suitable simulations of the resonator and piezoelectric transducer are performed by using measured signal from the engine suspension. Voltage outputs of linear (without amplitude limiter) and nonlinear harvesters were compared indicating better efficiency of the nonlinear design.

A novel up-converting mechanism based on double impact for non-linear piezoelectric energy harvesting

In this paper we show the importance of double impact in an up-converting mechanism by using a resonant low-frequency driving beam across a high-frequency piezoelectric beam, to enhance the electrical output power in a vibration energy harvesting (VEH) system suitable for ambient vibrations. The main advantage of this device is its nearly constant output voltage between impacts compared to other VEH systems using up-converting mechanisms whose output voltages decay abruptly after impact. With the proposed design, the optimum electrical load of the system is substantially lower compared to traditional low-frequency VEH systems. This mechanism improves the energy transfer to some transducers and electronic interfaces with low input impedances, attaining optimal efficiency.

Vibration energy-harvesting using inerter-based two-degrees-of-freedom system

Rotary electromagnetic generators that have high power density, large power output, and large rotational inertia are increasingly used in vibration energy-harvesting systems. When applied to single-degree-of-freedom (SDOF) systems, it is found that the inertance reduces the system frequency bandwidth. Furthermore, the maximum power output of SDOF systems is limited by the mechanical damping and the maximum allowable stroke. Two-degrees-of-freedom (2DOF) energy-harvesting systems have been proposed in recent years and demonstrated to have larger power output and wider bandwidth compared with SDOF systems. However, a considerable additional physical mass has to be added to an SDOF system to create a 2DOF energy-harvesting system, which may increase the total weight and requires more space. By utilizing the rotational inertia of the electromagnetic generator and a line-to-rotation mechanism as inerter, an inerter-based 2DOF system that requires neglectable additional physical mass is proposed, in which a spring and an inerter are connected in series between the primary mass and the vibration base. Parameters including the mass ratio, the frequency tuning ratio, the spring ratio, and the damping ratio, were optimized for the inerter-based 2DOF system. Optimal specific power with stroke limitation was obtained. A benchmark test using an energy harvesting backpack was done to validate the analysis results. Both analyses and experimental tests show that the inerter-based 2DOF can have larger specific power and larger power-to-stroke ratio compared with its SDOF counterpart. The energy conversion efficiency is also improved. Compared with the conventional 2DOF system, the inerter-based 2DOF system is not only lightweight but also less sensitive to parameter changes.

Disturbance observer–based terminal sliding mode control for effective performance of a nonlinear vibration energy harvester

We propose a new scheme to control the coexisting attractors in a bistable piezomagnetoelastic power generator. Coexisting periodic or chaotic attractors frequently occur in nonlinear energy harvesters. For effective performance of the energy harvester, the system is desired to operate on the high-energy periodic orbit. Therefore, a controller may be used to force the system to operate on the high-energy orbit. In the present research, a disturbance observer–based terminal sliding mode control with input saturation is proposed to push the system from low-energy periodic and chaotic attractors to high-energy periodic attractors. Furthermore, to minimize the energy required for the controller, a genetic algorithm optimization is employed to determine the bound of the input saturation and parameters of the controller. A major advantage of the proposed control technique is tracking control while control input limitations, significant concerns for energy harvesting purpose, are present. The Lyapunov stability theorem of the closed-loop system is proven in the presence of control input saturation and external disturbance. In addition to the primary resonance, superharmonic resonance is considered. The numerical results show that the proposed method can successfully control and shift the vibration energy harvesting system between different attractors in the presence of uncertainty and with minimal control energy budget.

System level design of wireless sensor node powered by piezoelectric vibration energy harvesting

This paper proposes a design of wireless sensor node powered by piezoelectric vibration energy harvesting system. A complete system level coupling circuit model is established to predict the performance characteristics. The piezoelectric vibration energy harvester (PVEH) is based on a PZT bimorph cantilever, in which a big proof mass is introduced to decrease resonant frequency and a shell served as a stopper to avoid overload. Lumped parameters of the model are identified by experiments and calculations. Electromechanical analogy model of PVEH is simulated in LTspice software. The power consumption of a temperature WSN is tested and the equivalent load model is simulated. A power management circuit (PMC) with LTC3588-1 is designed for rectifying and regulating output of PVEH. Electrical energy is stored in a capacitor. Finally, a system level coupling model is established. Time domain circuit simulation can provide the detailed parameters about the WSN powered by PVEH such as full charge time and sustainable time of the system. Test curves of capacitor charging and WSN power supply in prototype testification show good consistency with the simulation results in LTspice. An application for temperature WSN powered by PVEH is testified as an example. The method and model proposed in this paper can set up a reference to optimize system parameters for WSN powered by PVEH.

Vibration energy harvesting using magnetic spring based nonlinear oscillators: Design strategies and insights

The rising technologies of wearable electronics resulted in urgent demand for developing eco-friendly power sources that can utilize free energies around us including ambient vibrations. Magnetic springs are amongst the most common techniques used to build vibration energy harvesting systems that convert vibrational energy into useful electric power. Here, we present an experimental and theoretical platform for design guidelines and analysis of magnetic springs encountered in vibration energy harvesting systems. An energy harvester prototype consisting of an oscillating solid magnet levitated between two stationary ring magnets is constructed and used for experimental evaluation. Results show excellent agreement between model and experiment. The use of the analytical force model to represent magnetic force nonlinearities is essential at high accelerations. While the magnetic damping coefficient varies during dynamic operation and is dependent on the position of the levitated magnet, it is shown that approximating this coefficient as a constant provides accurate prediction of the dynamic behavior of the system. Approximate analytical expressions for linear and nonlinear stiffness coefficients are obtained. Results suggest that linear and nonlinear stiffness coefficients are coupled. The outer diameter of the stationary ring magnet can be used to tune the nonlinearity of the energy harvesting system to obtain linear, hardening nonlinear, or softening nonlinear response. This work serves as a tool for designers to understand the behavior of magnetic spring based harvesting systems and evaluate their performance in light of their design parameters. This work also can serve other energy systems that utilize magnetic springs including energy sinks.

Vibration energy harvesting enhancement exploiting magnetically coupled bistable and linear harvesters

Many common environmental vibration sources exhibit low and broad frequency spectra. In order to exploit such excitations, energy harvesting architectures utilizing nonlinearity, especially bistability, have been extensively explored as a promising energy source for self-powered small-scale electric devices. For such devices, the energetic interwell oscillations between their stable equilibria can provide enhanced power harvesting capability over a wider bandwidth compared to the linear counterpart. Yet, one of the limitations of these nonlinear architectures is that the interwell oscillation regime may not be readily activated for low excitation level that is not sufficient to overcome the potential energy barrier, thus resulting in low amplitude intrawell response, which provides poor energy harvesting performance. This research investigates a multi-degree of freedom (MDOF) vibration energy harvesting system that leverages magnetically coupled bistable and linear harvesters. It presents novel in-depth insights into capitalizing on a passive mechanism that not only facilitates the energetic interwell response for relatively low excitation amplitudes and frequencies than that may be required for conventional bistable harvester by passively and adaptively lowering the potential energy barrier level, but also effectively exploits the redistributed dynamic energy and the rich MDOF dynamic characteristics introduced by the magnetically coupled linear harvester. It is found that in addition to the enhanced power harvesting performance of bistable harvester with adaptive potential, the power captured from the redistributed energy and the higher harmonic resonances introduced by the passive mechanism further increase the energy harvesting performance especially at the lower frequency range. Analytical, numerical, and experimental investigations reveal that strategically incorporating a linear harvester magnetically coupled to a conventional bistable harvester provides an effective and easy to implement means for enhancing broadband energy harvesting performance.

Intelligent Control of Vibration Energy Harvesting System

The Intelligent Control of Vibration Energy Harvesting system is presented in this paper. The harvesting systems use a mechanical vibration to generate electrical energy in a suitable form for use. Proportional-Integrated-derivative controller and Fuzzy Logic controller have been suggested; their parameters are optimized using a new heuristic algorithm, the Camel Traveling Algorithm(CTA). The proposed circuit Simulink model was constructed in Matlab facilities, and the model was tested under various operating conditions. The results of the simulation using the CTA was compared with two other methods.

Nonlinear energy harvesting from vibratory disc-shaped piezoelectric laminates

• Performance of a nonlinear disc-shaped piezoelectric laminate in vibrational energy harvesting is evaluated. • A perturbative solution is presented and validated by finite element method simulations. • The power bandwidth is considerably enhanced in comparison to linear harvesters. Implementing resonators with geometrical nonlinearities in vibrational energy harvesting systems leads to considerable enhancement of their operational bandwidths. This advantage of nonlinear devices in comparison to their linear counterparts is much more obvious especially at small-scale where transition to nonlinear regime of vibration occurs at moderately small amplitudes of the base excitation. In this paper the nonlinear behavior of a disc-shaped piezoelectric laminated harvester considering midplane-stretching effect is investigated. Extended Hamilton’s principle is exploited to extract electromechanically coupled governing partial differential equations of the system. The equations are firstly order-reduced and then analytically solved implementing perturbation method of multiple scales. A nonlinear finite element method (FEM) simulation of the system is performed additionally for the purpose of verification which shows agreement with the analytical solution to a large extent. The frequency response of the output power at primary resonance of the harvester is calculated to investigate the effect of nonlinearity on the system performance. Effect of various parameters including mechanical quality factor, external load impedance and base excitation amplitude on the behavior of the system are studied. Findings indicate that in the nonlinear regime both output power and operational bandwidth of the harvester will be enhanced by increasing the mechanical quality factor which can be considered as a significant advantage in comparison to linear harvesters in which these two factors vary in opposite ways as quality factor is changed.