Linear Segmented Arc-Shaped Piezoelectric Branch Beam Energy Harvester for Ultra-Low Frequency Vibrations

Piezoelectric energy harvesting systems have been drawing the attention of the research community over recent years due to their potential for recharging/replacing batteries embedded in low-power-consuming smart electronic devices and wireless sensor networks. However, conventional linear piezoelectric energy harvesters (PEH) are often not a viable solution in such advanced practices, as they suffer from a narrow operating bandwidth, having a single resonance peak present in the frequency spectrum and very low voltage generation, which limits their ability to function as a standalone energy harvester. Generally, the most common PEH is the conventional cantilever beam harvester (CBH) attached with a piezoelectric patch and a proof mass. This study investigated a novel multimode harvester design named the arc-shaped branch beam harvester (ASBBH), which combined the concepts of the curved beam and branch beam to improve the energy-harvesting capability of PEH in ultra-low-frequency applications, in particular, human motion. The key objectives of the study were to broaden the operating bandwidth and enhance the harvester’s effectiveness in terms of voltage and power generation. The ASBBH was first studied using the finite element method (FEM) to understand the operating bandwidth of the harvester. Then, the ASBBH was experimentally assessed using a mechanical shaker and real-life human motion as excitation sources. It was found that ASBBH achieved six natural frequencies within the ultra-low frequency range (<10 Hz), in comparison with only one natural frequency achieved by CBH within the same frequency range. The proposed design significantly broadened the operating bandwidth, favouring ultra-low-frequency-based human motion applications. In addition, the proposed harvester achieved an average output power of 427 μW at its first resonance frequency under 0.5 g acceleration. The overall results of the study demonstrated that the ASBBH design can achieve a broader operating bandwidth and significantly higher effectiveness, in comparison with CBH

Towards Intelligent Tire and Self-Powered Sensing Systems

Tires are the interface between a vehicle and the ground providing forces and isolation to the vehicle. For vehicle safety, stability, maintenance, and performance, it is vital to estimate or measure tire forces, inflation pressure, and contact friction coefficient. Estimation methods can predict tire forces to some extent however; they fail in harsh maneuvers and are dependent on road surface conditions for which there is no robust estimation method. Measurement devices for tire forces exist for vehicle testing but at the cost of tens of thousands of dollars. Tire pressure-monitoring sensors (TPMS) are the only sensors available in newer and higher end vehicles to provide tire pressure, but there are no sensors to measure road surface condition or tire forces for production vehicles. With the prospect of autonomous driving on roads in near future, it is paramount to make the vehicles safe on any driving and road condition. This is only possible by additional sensors to make up for the driver’s cognitive and sensory system. Measuring road condition and tire forces especially in autonomous vehicles are vital in their safety, reliability, and public confidence in automated driving. Real time measurement of road condition and tire forces in buses and trucks can significantly improve the safety of road transportation system, and in miming/construction and off-road vehicles can improve performance, tire life and reduce operational costs. In this thesis, five different types of sensors are designed, modelled, optimized and fabricated with the objective of developing an intelligent tire. In order to design these sensors,~both electromagnetic generator (EMG) and triboelectric nanogenerators (TENG) are used. In the first two initial designed sensors, with the combination of EMG and TENG into a single package, two hybridized sensors are fabricated with promising potential for self-powered sensing. The potential of developed sensors are investigated for tire-condition monitoring system (TCMS). Considering the impressive properties of TENG units of the developed hybridized devices, three different flexible nanogenerators, only based on this newly developed technology, are developed for TCMS. The design, modelling, working mechanism, fabrication procedure, and experimental results of these TENG sensors are fully presented for applications in TCMS. Among these three fabricated sensors, one of them shows an excellent capability for TCMS because of its high flexibility, stable and high electrical output,and an encapsulated structure. The high flexibility of developed TENG sensor is a very appealing feature for TCMS, which cannot be found in any available commercial sensor. The fabricated TENG sensors are used for developing an intelligent tire module to be eventually used for road testing. Several laboratory and road tests are performed to study the capability of this newly developed TENG-based sensor for tire-condition monitoring system. However the development of this sensor is in its early stage, it shows a promising potential for installation into the hostile environment of tires and measuring tire-road interacting forces. A comparative studies are provided with respect to Michigan Scientific transducer to investigate the potential of this flexible nanogenerator for TCMS. It is worth mentioning that this PhD thesis presents one of the earliest works on the application of TENG-based sensor for a real-life system. Also, the potential of commercially available thermally and mechanically durable Micro Fiber Composite (MFC) sensor is experimentally investigated for TCMS with fabricating another set of intelligent tire. Several testing scenarios are performed to examine the potential of these sensors for TCMS taking into account a simultaneous measurement from Michigan Scientific transducer. Although both flexibility and the cost of this sensor is not comparable with the fabricated TENG device, they have shown a considerable and reliable performance for online measuring of tire dynamical parameters in different testing scenarios, as they can be used for both energy harvesting and sensing application in TCMS. The extensive road testing results based on the MFC sensors provide a valuable set of data for future research in TCMS. It is experimentally shown that MFC sensor can generate up to 1.4 $\mu W$ electrical power at the speed of 28 $[kph]$. This electrical output shows the high capability of this sensor for self-powered sensing application in TCMS. Results of this thesis can be used as a framework by researchers towards self-powered sensing system for real-world applications such as intelligent tires

Shape Optimization of Microfiber Composite Energy Harvesters

A model of energy harvesting beam with a piezoelectric material, microfiber composite (MFC), in a unimorph configuration was setup in Matlab using the governing equations of motions of a coupled electromechanical system. The equations of motion were derived using Hamilton’s variational principles and constitutive relations of a piezoelectric material. The mathematical model developed in Matlab was validated with an experiment and frequency response functions. The validated model was used to perform shape optimization so as to obtain the shape of the beam and the patch that harvests the largest voltage. The shape variables were length of the beam (LB), length of the patch (LP), and width of the beam. Optimization reveals that voltage increases with length of the beam and with an inverse tapering (increasing width) of the beam from the root to the tip. This approach presents a systematic way to design energy harvesters and can serve as the basis for the conceptual design of energy harvester for applications such as morphing wings, smart shoe, MEMS devices, etc

Energy harvesting from knee motion using piezoelectric patch transducers

This paper presents a piezoelectric energy harvesting device that generates electrical power from knee motion during human gait. The device is composed of two MEMS-based piezoelectric patch transducers optimized for placement around knee joints with minimal footprint. Simulations were performed on COMSOL software to reveal maximum performance that can be achieved under normal walking conditions. The internal capacitance of the patch transducers was measured to be 80 nF, while the resistance was on the order of 470 k. The patch transducers were inserted in a knee brace worn by a volunteer subject, and were characterized for voltage and power generation. During walking, the maximum open circuit voltage and rms power were measured to be 14 V and 6.2 uW, respectively. These values were observed to increase up to 14.4 V and 12 uW during a moderate running activity. The level of power achieved in the experiments shows the potential of this device as an independent onboard power component and as a continuous battery charger for wearable electronic devices.Bu çalışmada insanların yürüyüşleri esnasında diz hareketinden enerji elde edebilen bir piezoelektrik enerji hasadı aygıtının geliştirilmesi ve test edilmesi ele alınmıştır. Aygıt diz çevresine yerleştirmek üzere optimize edilmiş ve minimal ölçülere sahip iki adet MEMS tabanlı piezoelektrik yama dönüştürücüden oluşmaktadır. COMSOL programında yapılan simülasyonlar ile normal yürüme sırasında elde edilebilecek maksimum performans incelenmiştir. Piezoelektrik dönüştürücülerin iç kapasitans ve dirençlerinin 80 nF ile 470 kohm mertebesinde olduğu ölçülmüştür. Dönüştürücüler bir gönüllünün taktığı dizliğe yerleştirilerek, üretilen gerilim ve güç değerleri test edilmiştir. Yürüme sırasında maksimum 14 V ve 6.2 uW rms güç elde edilmiştir. Bu değerlerin orta hızlı koşma esnasında 14.4 V ve 12uW’a çıktığı gözlemlenmiştir. Ölçülen gerilim ve güç değerleri, bu aygıtın giyilebilir elektronik aletleri çalıştırabilme ve bu aletlerin pillerini sürekli şarj edebilme potansiyelini ortaya koymaktadır.No sponso

Numerical Analysis of Energy Harvesting Process Using Piezoelectric Transducers in an Oscillating Heat Pipe

Energy harvesting is a powerful process that deals with exploring different possible ways of converting energy dispersed in the environment into useful form of energy, essentially electrical energy. Piezoelectric materials are known for their ability of transferring mechanical energy into electrical energy or vice versa. This work takes an advantage of piezoelectric material\u27s properties to covert thermal energy into electrical energy in an oscillating heat pipe. Specific interest in an oscillating heat pipe has relevance to energy harvesting for low power generation suitable for remote electronics operation as well as low-power heat reclamation for electronic packaging. The aim of this research is to develop a multi-physics numerical analysis model that aids in predicting electrical power generation inherent to an oscillating heat pipe. The experimental design consists of a piezoelectric patch with fixed configuration, attached inside an oscillating heat pipe and its behavior when subjected to the oscillating fluid pressure was observed. Numerical analysis of the model depicting the similar behavior was developed using COMSOL multi physics FEA software. The numerical model consists of a three-way physics interaction that takes into account thermo-hydrodynamic interaction, fluid-structure interaction, and piezoelectric effect. Results obtained from 3D numerical analysis are compared with experimental recordings to validate the numerical model

Vibration Energy Harvesting for Wireless Sensors

Kinetic energy harvesters are a viable means of supplying low-power autonomous electronic systems for the remote sensing of operations. In this Special Issue, through twelve diverse contributions, some of the contemporary challenges, solutions and insights around the outlined issues are captured describing a variety of energy harvesting sources, as well as the need to create numerical and experimental evidence based around them. The breadth and interdisciplinarity of the sector are clearly observed, providing the basis for the development of new sensors, methods of measurement, and importantly, for their potential applications in a wide range of technical sectors

Energy Harvesting & Wing Morphing Design Using Piezoelectric Macro Fiber Composites

Energy harvesting from vibration sources was a very promising field of research throughout the last few decades among the engineers and scientist as considering the necessity of renewable/green energy for the welfare of mankind. Unused vibration energy exists in the surrounding or machineries was always tried to be utilized. Since then, by using piezoelectric transduction, researchers started to harvest the vibration energy. However, after the invention of piezo ceramics Macro Fiber Composites (MFC) by NASA, the research in this field augmented a lot due to its high efficiency to convert mechanical strain or vibration to useful electrical power and vice versa. Apart from energy harvesting researcher concentrated to utilize this harvested energy for daily life and hence application of this harvested energy for structural health monitoring inaugurated. Recent study showed that, the vibration energy harvested from the vehicles or aerospace (UAV) structure is good enough to power its onboard structural health monitoring unit though for feeding this power to any other onboard electrical system is still challenging due to low power generation along with its random production. Moreover, Macro Fiber Composites (MFC) can be used as an actuator to change the shape of aircraft wing to enhance aerodynamic performance and hence, application of MFC for wing morphing design has become popular throughout these years. The purpose of this research work is to depict the recent progress & development that took place in the field of energy harvesting & wing morphing research using macro fiber composites and combining the existing knowledge continue the work further, the future of this harvested energy, new design concept & upcoming challenges along with its possible solution. This work investigates the different configuration of macro fiber composites (MFC) for piezoelectric energy harvesting and its contribution for wing morphing design with enhanced aerodynamics. For the first part of this work, uniform MFC configuration was modeled and built up based on the Euler-Bernoulli beam theory. When the governing differential equations of the systems were derived, by applying the harmonic base excitation, coupled vibration response and the voltage response were obtained. The prediction of the mathematical model was at first verified by unimorph MFC with a brass substrate obtained from the state of art and then validation was justified by MFC unimorph along with three different substrate materials (copper, zinc alloy & galvanized steel) and thickness for the first time in this type of research. Computational & analytical solution revealed that, among these three substrates and for same thickness, maximum peak power at resonance excitation was obtained for the copper substrate. For the second part of the study (i) computational analysis was performed and the output was compared with the real time data obtained from the wind tunnel experiment and the conclusion stood that, with the increment of the incoming flow velocity, the power output from the MFC increases with a thin aerofoil made of copper substrates and two MFC on its upper surface (ii) wing morphing design was performed for a NACA 0012 aerofoil for the first time where macro fiber composite actuators were used to change the top and bottom surfaces of the aerofoil with a view to recording the enhanced aerodynamics performance the designed morphing wing. CFD simulation results were compared with the wind tunnel testing data from the state of art for NACA 0014 for all identical parameters. The enhanced aerodynamics performance observed for designed wing morphing can be used for future concepts like maneuvering of the aircraft without the help of ailerons or for the purpose of active flow control over the aircraft wing

Functional modelling and prototyping of electronic integrated kinetic energy harvesters

The aim of developing infinite-life autonomous wireless electronics, powered by the energy of the surrounding environment, drives the research efforts in the field of Energy Harvesting. Electromagnetic and piezoelectric techniques are deemed to be the most attractive technologies for vibrational devices. In the thesis, both these technologies are investigated taking into account the entire energy conversion chain. In the context of the collaboration with the STMicroelectronics, the project of a self-powered Bluetooth step counter embedded in a training shoe has been carried out. A cylindrical device 27 × 16mm including the transducer, the interface circuit, the step-counter electronics and the protective shell, has been developed. Environmental energy extraction occurs exploiting the vibration of a permanent magnet in response to the impact of the shoe on the ground. A self-powered electrical interface performs maximum power transfer through optimal resistive load emulation and load decoupling. The device provides 360 μJ to the load, the 90% of the maximum recoverable energy. The energy requirement is four time less than the provided and the effectiveness of the proposed device is demonstrated also considering the foot-steps variability and the performance spread due to prototypes manufacturing. In the context of the collaboration with the G2Elab of Grenoble and STMicroelectronics, the project of a piezoelectric energy arvester has been carried out. With the aim of exploiting environmental vibrations, an uni-morph piezoelectric cantilever beam 60×25×0.5mm with a proof mass at the free-end has been designed. Numerical results show that electrical interfaces based on SECE and sSSHI techniques allows increasing performance up to the 125% and the 115% of that in case of STD interface. Due to the better performance in terms of harvested power and in terms of electric load decoupling, a self-powered SECE interface has been prototyped. In response to 2 m/s2 56,2 Hz sinusoidal input, experimental power recovery of 0.56mW is achieved demonstrating that the device is compliant with standard low-power electronics requirements

Parametric Instabilities for Vibratory Energy Harvesting under Harmonic, Time-Varying Frequency, and Random Excitations

This effort investigates and evaluates the prospect of using parametric instabilities for vibratory energy harvesting. To that end, we consider a parametrically-excited piezoelectric cantilever beam and study its performance as an energy harvester under i) fixed-frequency harmonic excitations, ii) time-varying frequency excitations, and iii) band-limited Gaussian noise. In the case of fixed-frequency excitations, we use the Method of Multiple Scales to obtain approximate analytical expressions for the steady-state response amplitude and instantaneous output power in the vicinity of the first principle parametric resonance. We show that the electromechanical coupling and load resistance play an important role in determining the output power and characterizing the bandwidth of the harvester. Specifically, we demonstrate that the region of parametric instability wherein energy can be harvested shrinks as the coupling coefficient increases, and that there exists a coupling coefficient beyond which the peak power decreases. We also show that there is a critical excitation level below which no energy can be harvested. The magnitude of this critical excitation increases with the coupling coefficient and is maximized for a given electric load resistance. Theoretical findings were compared to experimental data showing good agreement and reflecting the general physical trends. In the case of time-varying frequency excitations, we consider two beams of different nonlinear behaviors: one exhibiting a softening response while the other exhibiting hardening characteristics. We show that, for both beams, the bandwidth of the harvester decreases with increasing frequency sweep rate and that the instantaneous peak power during a sweep cycle decreases and shifts in the direction of the sweep. Furthermore, experimental findings illustrate that the average output power of the iii harvester is significantly higher when the sweep is in the direction in which the steady-state principle parametric resonance curves of the beams bend. Also, as the frequency sweep rate increases, the average output power decreases until beyond a threshold sweep rate where no power can be harvested. Based on the preceding conclusions, we introduce the new concept of a Softening- Hardening Hysteretic Harvester (SHHH), which is designed to scavenge energy effi- ciently from an excitation source whose frequency varies with time around a center frequency. Introductory experimental investigation on the SHHH illustrated that this concept produces more power than either a softening or a hardening beam alone. Finally, in an effort to duplicate real-world scenarios under which energy harvesting occurs, both the hardening and the softening beam were subjected to parametric, band-limited, random Gaussian excitations and their performance in scavenging energy under different excitation bandwidths was evaluated. We observed that, under narrow bandwidth excitations (on the order of the harvester\u27s steady-state bandwidth) and regardless of the beam\u27s nonlinear characteristics, the parametric instability was activated for the length of the experiment. However, the average output power was very low (on the order of micro-Watts under excitations having a variance of 1.5 g). The power decreased even further as the bandwidth of the excitation was increased

Optimisation and Management of Energy Generated by a Multifunctional MFC-Integrated Composite Chassis for Rail Vehicles

With the advancing trend towards lighter and faster rail transport, there is an increasing interest in integrating composite and advanced multifunctional materials in order to infuse smart sensing and monitoring, energy harvesting and wireless capabilities within the otherwise purely mechanical rail structures and the infrastructure. This paper presents a holistic multiphysics numerical study, across both mechanical and electrical domains, that describes an innovative technique of harvesting energy from a piezoelectric micro fiber composites (MFC) built-in composite rail chassis structure. Representative environmental vibration data measured from a rail cabin have been critically leveraged here to help predict the actual vibratory and power output behaviour under service. Time domain mean stress distribution data from the Finite Element simulation were used to predict the raw AC voltage output of the MFCs. Conditioned power output was then calculated using circuit simulation of several state-of-the-art power conditioning circuits. A peak instantaneous rectified power of 181.9 mW was obtained when eight-stage Synchronised Switch Harvesting Capacitors (SSHC) from eight embedded MFCs were located. The results showed that the harvested energy could be sufficient to sustain a self-powered structural health monitoring system with wireless communication capabilities. This study serves as a theoretical foundation of scavenging for vibrational power from the ambient state in a rail environment as well as to pointing to design principles to develop regenerative and power neutral smart vehicles