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

非線形振動を励起させることによる回転するタイヤ内でのエナジーハーべスティング

学位の種別: 課程博士審査委員会委員 : （主査）東京大学准教授 中野 公彦, 東京大学教授 須田 義大, 東京大学准教授 大石 岳史, 東京大学教授 割澤 伸一, 東京大学教授 金 範埈University of Tokyo(東京大学

Analysis of nonlinear suspension power harvest potential

Because the power consumption of a controlled suspension is huge, the power harvest potential of a nonlinear controlled suspension is analyzed. Instead of simplifying the suspension to a linear model or adopting some control strategies to solve the problem, this paper investigates the effect of the nonlinear characteristics on the power harvesting potential. A mathematic model is introduced to calculate the nonlinear vibration, and the amount of harvested power was obtained using the multi-scale method. A numerical validation is carried out at the end of this study. The results show that the investigated mechanical parameters affect both the vibration amplitude and the induced current, while the electric parameters only affect the induced current. The power harvesting potential of the nonlinear suspension is generally greater than the linear suspension because the frequency band of the actual pavement also contains bandwidth surrounding the body resonance point. The only exception occurs if the vehicle travels on a road with a particular profile, e.g. a sine curve. To optimize harvested power, it is better to consider the nonlinear characteristics rather than simplifying the suspension to a linear model

Piezoelectric Energy Harvesting Suspension System for a Half Car Model: Analytical and Experimental Study

One of the essential techniques for energy harvesting is the clean energy collection from ambient vibration. Recently, piezoelectric energy harvesting systems became a hot topic and attracted many researchers. This is due to their simple structure, relatively high output power among the other mechanisms (electromagnetic and electrostatic), compatibility with MEMS, and operation in a wide frequency range. The main objective of the current work is to develop a mathematical model to evaluate the potential of harvesting power from the car suspension system. Quarter and half car models with a built-in piezoelectric stack were modeled mathematically using Laplace transformation and simulated using MATLAB/Simulink. The piezoelectric stack was installed in series with the suspension spring to maintain the performance of the original suspension system in ride quality and comfortability. The harvested voltage and power were tested in both time and frequency domain approaches. The results from a quarter car model showed that, the maximum generated voltage and power under harmonic excitation with an acceleration amplitude of 0.5 g and frequency of 1.46 Hz were 19.11 V and 36.74 mW, respectively. By comparing the quarter car model with a half car model, the results illustrated that the output voltage and power of the half car models were increased to 33.56 V and 56.35 mW (75.6% and 53.4%), respectively. Furthermore, the quarter and half car models were subjected to random excitation and tested under three different road classes (A, C, and H). The findings confirmed that the harvested voltage and power were increased with the road roughness levels and car velocity. From very smooth to very rough road levels, the harvested power was increased by 434 mW for quarter car model and 537 mW for half car model. The influence of the different parameters of the piezoelectric stack (number of stack layers and area to thickness) and car suspension (sprung and unsprung stiffness, damping coefficients, and masses) were examined for half car model subjected to harmonic excitation. Also, the effect of road amplitude unevenness was considered. The analytical results of the quarter car model were verified with the experimental test under harmonic excitation. The results exhibited good agreement with the analytical results at different excitation frequencies (0 – 25 Hz). A significant contribution of this work is developing a half car model with a built-in piezoelectric stack. The findings of this work illustrated that there is a significant potential for harvesting energy from the car suspension system. This energy could be utilized in different ways. The study will encourage automobile manufacturers to develop and produce cars that are equipped with multiple energy harvesters to make the dissipated energy available for utilization. Such utilization of regenerated energy improves the fuel efficiency and the economy significantly

Nonlinear energy harvesting based on a rotating system

Acknowledgement The authors acknowledge the financial supports of the National Natural Science Foundation of China (No.11702111, 11732014,11872201, 12172166) and the State Scholarship Fund of CSCPeer reviewedPostprin

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

Vibration energy harvester for variable speed rotor applications using passively self-tuned beams

A vibration energy harvester is proposed for rotating systems based on transverse vibrations of an assembly of thin beams and electromagnetic interaction of a carried magnet with a coil of wire. The harvester is designed in a way such that centrifugal forces are utilized to tune the system’s natural frequency to the expected frequency of torsional vibrations. In fact, a novel combination of a tuning mass positioned at the beam’s support and an applied preload are introduced to establish a tuning mechanism that is capable of maintaining resonance along a wide frequency range. The device’s tuning can cover relatively high rotor speeds, overcoming previous limitations on the size and the physics of tuning via axial loads. Moreover, exact expressions of the beams’ mode shapes are taken into account to improve the accuracy of the proposed tuning mechanism. Numerical simulations of the device’s response are carried out for case studies corresponding to different frequency orders. It is shown that the system can maintain a flat power output across a wide range of operating speeds, effectively leading to purely broadband energy harvesting

Vibration energy harvester for variable speed rotor applications using passively self-tuned beams

A vibration energy harvester is proposed for rotating systems based on transverse vibrations of an assembly of thin beams and electromagnetic interaction of a carried magnet with a coil of wire. The harvester is designed in a way such that centrifugal forces are utilized to tune the system’s natural frequency to the expected frequency of torsional vibrations. In fact, a novel combination of a tuning mass positioned at the beam’s support and an applied preload are introduced to establish a tuning mechanism that is capable of maintaining resonance along a wide frequency range. The device’s tuning can cover relatively high rotor speeds, overcoming previous limitations on the size and the physics of tuning via axial loads. Moreover, exact expressions of the beams’ mode shapes are taken into account to improve the accuracy of the proposed tuning mechanism. Numerical simulations of the device’s response are carried out for case studies corresponding to different frequency orders. It is shown that the system can maintain a flat power output across a wide range of operating speeds, effectively leading to purely broadband energy harvesting

Structural vibration energy harvesting via bistable nonlinear attachments

A vibration-based bistable electromagnetic energy harvester coupled to a directly excited host structure is theoretically and experimentally examined. The primary goal of the study is to investigate the potential benet of the bistable element for harvesting broadband and low-amplitude vibration energy. The considered system consists of a grounded, weakly damped, linear oscillator (LO) coupled to a lightweight, damped oscillator by means of an element which provides for both cubic nonlinear and negative linear stiness components and electromechanical coupling elements. Single and repeated impulses with varying amplitude applied to the LO are the vibration energy sources considered. A thorough sensitivity analysis of the system's key parameters provides design insights for a bistable nonlinear energy harvesting (BNEH) device able to attain robust harvesting efficiency. Energy localization into the bistable attachment is achieved through the exploitation of three BNEH main dynamical regimes; namely, periodic cross-well, aperiodic (chaotic) cross-well, and in-well oscillations. For the experimental investigation on the performance of the bistable device, nonlinear and negative linear terms in the mechanical coupling are physically realized by exploiting the transverse displacement of a buckled slender steel beam; the electromechanical coupling is accomplished by an electromagnetic transducer

Development of MEMS Piezoelectric Vibration Energy Harvesters with Wafer-Level Integrated Tungsten Proof-Mass for Ultra Low Power Autonomous Wireless Sensors

La génération d’énergie localisée et à petite échelle, par transformation de l’énergie vibratoire disponible dans l’environnement, est une solution attrayante pour améliorer l’autonomie de certains noeuds de capteurs sans-fil pour l’Internet des objets (IoT). Grâce à des microdispositifs inertiels résonants piézoélectriques, il est possible de transformer l’énergie mécanique en électricité. Cette thèse présente une étude exhaustive de cette technologie et propose un procédé pour fabriquer des microgénérateurs MEMS offrant des performances surpassant l’état de l’art. On présente d’abord une revue complète des limites physiques et technologiques pour identifier le meilleur chemin d’amélioration. En évaluant les approches proposées dans la littérature (géométrie, architecture, matériaux, circuits, etc.), nous suggérons des métriques pour comparer l’état de l’art. Ces analyses démontrent que la limite fondamentale est l’énergie absorbée par le dispositif, car plusieurs des solutions existantes répondent déjà aux autres limites. Pour un générateur linéaire résonant, l’absorption d’énergie dépend donc des vibrations disponibles, mais aussi de la masse du dispositif et de son facteur de qualité. Pour orienter la conception de prototypes, nous avons réalisé une étude sur le potentiel des capteurs autonomes dans une automobile. Nous avons évalué une liste des capteurs présents sur un véhicule pour leur compatibilité avec cette technologie. Nos mesures de vibrations sur un véhicule en marche aux emplacements retenus révèlent que l’énergie disponible pour un dispositif linéaire résonant MEMS se situe entre 30 à 150 Hz. Celui-ci pourrait produire autour de 1 à 10 μW par gramme. Pour limiter la taille d’un générateur MEMS pouvant produire 10 μW, il faut une densité supérieure à celle du silicium, ce qui motive l’intégration du tungstène. L’effet du tungstène sur la sensibilité du dispositif est évident, mais nous démontrons également que l’usage de ce matériau permet de réduire l’impact de l’amortissement fluidique sur le facteur de qualité mécanique Qm. En fait, lorsque l’amortissement fluidique domine, ce changement peut améliorer Qm d’un ordre de grandeur, passant de 103 à 104 dans l’air ambiant. Par conséquent, le rendement du dispositif est amélioré sans utiliser un boîtier sous vide. Nous proposons ensuite un procédé de fabrication qui intègre au niveau de la tranche des masses de tungstène de 500 μm d’épais. Ce procédé utilise des approches de collage de tranches et de gravure humide du métal en deux étapes. Nous présentons chaque bloc de fabrication réalisé pour démontrer la faisabilité du procédé, lequel a permis de fabriquer plusieurs prototypes. Ces dispositifs ont été testés en laboratoire, certains démontrant des performances records en terme de densité de puissance normalisée. Notre meilleur design se démarque par une métrique de 2.5 mW-s-1/(mm3(m/s2)2), soit le meilleur résultat répertorié dans l’état de l’art. Avec un volume de 3.5 mm3, il opère à 552.7 Hz et produit 2.7 μW à 1.6 V RMS à partir d’une accélération de 1 m/s2. Ces résultats démontrent que l’intégration du tungstène dans les microgénérateurs MEMS est très avantageuse et permet de s’approcher davantage des requis des applications réelles.Small scale and localized power generation, using vibration energy harvesting, is considered as an attractive solution to enhance the autonomy of some wireless sensor nodes used in the Internet of Things (IoT). Conversion of the ambient mechanical energy into electricity is most often done through inertial resonant piezoelectric microdevices. This thesis presents an extensive study of this technology and proposes a process to fabricate MEMS microgenerators with record performances compared to the state of the art. We first present a complete review of the physical and technological limits of this technology to asses the best path of improvement. Reported approaches (geometries, architectures, materials, circuits) are evaluated and figures of merit are proposed to compare the state of the art. These analyses show that the fundamental limit is the absorbed energy, as most proposals to date partially address the other limits. The absorbed energy depends on the level of vibrations available, but also on the mass of the device and its quality factor for a linear resonant generator. To guide design of prototypes, we conducted a study on the potential of autonomous sensors in vehicles. A survey of sensors present on a car was realized to estimate their compatibility with energy harvesting technologies. Vibration measurements done on a running vehicle at relevant locations showed that the energy available for MEMS devices is mostly located in a frequency range of 30 to 150 Hz and could generate power in the range of 1-10 μW per gram from a linear resonator. To limit the size of a MEMS generator capable of producing 10 μW, a higher mass density compared to silicon is needed, which motivates the development of a process that incorporates tungsten. Although the effect of tungsten on the device sensitivity is well known, we also demonstrate that it reduces the impact of the fluidic damping on the mechanical quality factor Qm. If fluidic damping is dominant, switching to tungsten can improve Qm by an order of magnitude, going from 103 to 104 in ambient air. As a result, the device efficiency is improved despite the lack of a vacuum package. We then propose a fabrication process flow to integrate 500 μm thick tungsten masses at the wafer level. This process combines wafer bonding with a 2-step wet metal etching approach. We present each of the fabrication nodes realized to demonstrate the feasibility of the process, which led to the fabrication of several prototypes. These devices are tested in the lab, with some designs demonstrating record breaking performances in term of normalized power density. Our best design is noteworthy for its figure of merit that is around 2.5 mW-s-1/(mm3(m/s2)2), which is the best reported in the state of the art. With a volume of 3.5 mm3, it operates at 552.7 Hz and produces 2.7 μW at 1.6 V RMS from an acceleration of 1 m/s2. These results therefore show that tungsten integration in MEMS microgenerators is very advantageous, allowing to reduce the gap with needs of current applications