Vibration control is a large branch in control research, because all moving systems may induce desired or undesired vibration. Due to the limitation of passive system's adaptability and changing excitation input, vibration control brings the solution to change system dynamic with desired behavior to fulfill control targets. According to preference, vibration control can be separated into two categories: vibration reduction and vibration amplification. Lots of research papers only examine one aspect in vibration control. The thesis investigates the control development for both control targets with two different control applications: vehicle suspension and ocean wave energy converter. It develops control methods for both systems with simplified modeling setup, then followed by the application of a novel mechanical motion rectifier (MMR) gearbox that uses mechanical one-way clutches in both systems. The flow is from the control for common system to the control design for a specifically designed system. In the thesis, active (model predictive control: MPC), semi-active (Skyhook, skyhook-power driven damper: SH-PDD, hybrid model predictive control: HMPC), and passive control (Latching Control) methods are developed for different applications or control performance comparison on single system. The thesis also studies about new type of system with switching mechanism, in which other papers do not talk too much and possible control research direction to deal with such complicated system in vibration control. The state-space modeling for both systems are provided in the thesis with detailed model of the MMR gearbox. From the simulation, it can be shown that in the vehicle suspension application, the controlled MMR gearbox can be effective in improving vehicle ride comfort by 29.2% compared to that of the traditional hydraulic suspension. In the ocean wave energy converter, the controlled MMR WEC with simple latching control can improve the power generation by 57% compared to the passive MMR WEC. Besides, the passive MMR WEC also shows its advantage on the passive direct drive WEC in power generation improvement. From the control development flow for the MMR system, the limitation of the MMR gearbox is also identified, which introduces the future work in developing active-MMR gearbox by using an electromagnetic clutch. Some possible control development directions on the active-MMR is also mentioned at the end of the thesis to provide reference for future works. / Master of Science / Vibration happens in our daily life in almost all cases. It is a regular or irregular back and forth motion of particles. For example, when we start a vehicle, the engine will do circular motion to drive the wheel, which causes vibration and we feel wave pulses on our body when we sit in the car. However, this kind of vibration is undesirable, since it makes us uncomfortable. The car manufacture designs cushion seats to absorb vibration. This is a way to use hardware to control vibration. However, this is not enough. When vehicle goes through bumps, we do have suspension to absorb vibration transferred from road to our body. The car still experiences a big shock that makes us feel dizzy. On the opposite direction, in some cases when vibration becomes the motion source for energy harvesting, we would like to enhance it. Hardware can be helpful, since by tuning some parameters of an energy harvesting device, it can match with the vibration source to maximize vibration. However, it is still not enough due to low adaptability of a fixed parameter system. To overcome the limitation of hardware, researches begin to think about the way to control vibration, which is the method to change system behavior by using real-time adjustable hardware. By introducing vibration control, the theory behind that started to be investigated. This thesis investigates the vibration control theory application in both cases: vibration reduction and vibration enhancement, which are mentioned above due to opposite application preferences. There are two major applications of vibration control: vehicle suspension control and ocean wave energy converter (WEC) control. The thesis starts from the control development for both fields with general modeling criteria, then followed by control development with specific hardware design-mechanical motion rectifier (MMR) gearbox-applied on both systems. The MMR gearbox is the researcher designed hardware that targets on vibration adjustment with hardware capability, which is similar as the cushion seats mentioned at the beginning of the abstract. However, the MMR cannot have capability to furtherly optimize system vibration, which introduces the necessity of control development based on the existing hardware. In the suspension control application, the control strategy introduced successfully improve the vehicle ride comfort by 29.2%, which means the vehicle body acceleration has been reduced furtherly to let passenger feel less vibration. In the WEC application, the power absorbed from wave has been improved by 57% by applying suitable control strategy. The performance of improvement on vibration control has proved the effect on further vibration optimization beyond hardware limitation.

The proposed circuit intends to harvest kinetic energy from ElectroMagnetic Generators (EMGs). In order to extract maximum power from an EMG, an AC-DC boost rectifier is designed to match the impedance of the EMG. Rather than operate a buck-boost converter in Discontinuous Conduction Mode (DCM) in other impedance matching cases, the proposed method is running the boost topology in Boundary Conduction Mode (BCM). So it would perform resistive input matching, while reducing the converter power loss. The boost rectifier also merges a rectifier and a boost converter to reduce power loss for rectification. It also utilizes the internal inductance of the EMG to eliminate the impedance matching error and reduce the off-chip inductor size. An optional buck converter regulates the output voltage to 5 V to power devices through USB ports. The proposed circuit is designed and fabricated in BiCMOS 0.18 μm technology. Its functionality is shown through simulation results. The measurement of the IC is also performed. However, since the IC only work partially, test result is gathered using some discrete components as substitutes. It indicates the circuit can realize the proposed control method. / Master of Science / The development of energy-efficient semiconductor devices has reduced the power requirements of electronic circuits. As the electronics’ scale decreases, so does the energy consumption. In this sense, batteries were also produced in smaller size providing more energy storage availability. However, due to technical and technological issues, the batteries have not been followed by the same evolutionary trend limiting the operational time and performance of portable devices as it need to be recharged or replaced periodically. On the other hand, portable electronic devices such as cell phones, GPS, cameras, etc. are powered only by batteries. For circumstances that power supplies are not accessible, energy harvesting (EH) from human or environmental sources has proven to be an effective alternative or complement. Light, thermal, mechanical and RF are major sources in EH. Among them, mechanical energy from wind, waves, vibrations, etc. is commonly existed in our daily life. The energy is harvested by using micro generators and the various types include electromagnetic, piezoelectric and electrostatic. In particular, the ElectroMagnetic Generator (EMG) is of great interest for its potentially high energy density and efficiency. Since EMG is an AC voltage generator while portable devices usually require a stable DC supply, an EH circuit as a rectifier ought to be designed. At the same time, for EH application, we would like to harvest as much power as possible from EMGs. This research project addresses the development of a unique EH circuit capable of fulfilling the distinct needs illustrated above.

Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although cannot all be adopted for generating electricity, the amount of the power can be absorbed still can occupy a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a self-reactive two-body wave energy point absorber that is embedded with a novel PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis and testing to improve the energy harvesting efficiency and the reliability of the PTO. The MMR mechanism can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. As a result, this mechanism brings in two advantages towards the PTO. The first advantage it possess is that the alternating stress of the PTO is changed into normal stress, hence the reliability of the components are expected to be improved significantly. The other advantage it brings in is a unique phenomenon of engagement and disengagement during the operation, which lead to a piecewise nonlinear dynamic property of the PTO. This nonlinearity of the PTO can contribute to an expanded frequency domain bandwidth and better efficiency, which are verified through both numerical simulation and in-lab experiment. During the in-lab test, the prototyped PTO achieved energy transfer efficiency as high as 81.2%, and over 40% of efficiency improvement compared with the traditional non-MMR PTO under low-speed condition, proving the previously proposed advantage. Through a more comprehensive study, the MMR PTO is further characterized and a refined dynamic model. The refined model can accurately predict the dynamic response of the PTO. The major factors that can influence the performance of the MMR PTO, which are the inertia of the PTO, the damping coefficient, and the excitation frequency, are explored through analysis and experiment comprehensively. The results show that the increase on the inertia of the PTO and excitation frequency, and decrease on the damping coefficient can lead to a longer disengagement of the PTO and can be expressed analytically. Besides the research on the PTO, the body structure of the point absorber is analyzed. Due to the low-frequency of the ocean wave excitation, usually a very large body dimension for the floating buoy of the point absorber is desired to match with that frequency. To solve this issue, a self-reactive two-body structure is designed where an additional frequency between the two interactive bodies are added to match the ocean wave frequency by adopting an additional reactive submerged body. The self-reactive two-body structure is tested in a wave to compare with the single body design. The results show that the two-body structure can successfully achieve the frequency matching function, and it can improve more than 50% of total power absorption compared with the single body design. / Doctor of Philosophy / Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although impossible to be all transferred into electricity, the amount of the power can be absorbed still can cover a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a novel two body wave energy converter with a PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis, and testing. To improve the energy harvesting efficiency and the reliability of the PTO, the dissertation induced a mechanical PTO that uses MMR mechanism which can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. This mechanism brings in a unique phenomenon of engagement and disengagement and a piecewise nonlinear dynamic property into the PTO. Through a comprehensive study, the MMR PTO is further characterized and a refined dynamic model that can accurately predict the dynamic response of the PTO is established. The major factors that can influence the performance of the MMR PTO are explored and discussed both analytically and experimentally. Moreover, as it has been theoretically hypothesis that using a two-body structure for designing the point absorbers can help it to achieve a frequency tuning effect for it to better match with the excitation frequency of the ocean wave, it lacks experimental verification. In this dissertation, a scaled two-body point absorber prototype is developed and put into a wave tank to compare with the single body structure. The test results show that through the use of two-body structure and by designing the mass ratio between the two bodies properly, the point absorber can successfully match the excitation frequency of the wave. The highest power capture width ratio (CWR) achieved during the test is 58.7%, which exceeds the results of similar prototypes, proving the advantage of the proposed design.

The objective of this thesis is to develop a dual-functional approach to effectively mitigate the earthquake induced vibrations of low- or mid-rise buildings, and at the same time to efficiently harvest utility-scale energy by using an optimally configured multi-resonant electromagnetic shunt in base isolation. In this research, two multi-resonant shunt configurations, parallel and series, were proposed and optimized based on the H2 criteria when the base isolation system is subjected to ground acceleration excitations. The performance of the proposed multi-resonant electromagnetic shunt was compared with traditional multiple tuned mass dampers (TMDs) applied to the base isolation system. It shows that, for multiple TMDs and multi-resonant electromagnetic shunt dampers with 5% total stiffness ratio, the parallel shunt electromagnetic shunt can achieve the best vibration mitigation performance among other types of multi-resonant dampers, including parallel TMDs, series TMDs and the series electromagnetic shunt damper. Case study of a base-isolated structure was analyzed to investigate the effectiveness of the proposed multi-resonant electromagnetic shunt. It shows that both multi-mode shunt circuits outperform single mode shunt circuit by suppressing the primary and the second vibration modes simultaneously. Comparatively, the parallel shunt circuit is more effective in vibration mitigation and energy harvesting, and is also more robust in parameter mistuning than the series shunt circuit. The time history response analysis shows that, under the recorded Northridge earthquake, the instant peak power and total average power capable to be harvested by the multi-resonant shunt can reach up to 1.18 MW and 203.37KW, respectively. This thesis further experimentally validated the effectiveness of the multi-resonant electromagnetic shunt on a scaled-down base-isolated building. The impact hammer test shows that the multi-resonant electromagnetic shunt can achieve enhanced vibration suppression by reducing the first resonant peak by 27.50dB and the second resonant peak by 22.57dB regarding the primary structure acceleration. The shake table test shows that under scaled Kobe and Northridge earthquake signals, the electromagnetic shunt can effectively reduce the vibration resonant peak value by 38.92% and 66.61%, respectively. The voltage simultaneously generated in the multi-mode shunt circuit was also obtained, which demonstrated the dual functions of the multi-resonant electromagnetic shunt in base isolation. / Master of Science / This thesis investigated multi-resonant electromagnetic shunt with application to base isolation for dual-functional vibration damping and energy harvesting. Two multi-mode shunt circuit configurations, namely in parallel and in series, were proposed and optimized based on the <i>H</i>₂ criteria, with physical meaning to minimize the RMS relative displacement for the concern of building safety subjected to broad bandwidth ground acceleration excitations. The performance of the proposed multi-resonant electromagnetic shunt was compared with traditional multiple tuned mass dampers applied to the base isolation system. It shows that, for multiple TMDs and multiresonant electromagnetic shunt dampers with 5% total stiffness ratio, the parallel shunt electromagnetic shunt can achieve the best vibration mitigation performance among other types of multi-resonant dampers, including parallel TMDs, series TMDs and the series electromagnetic shunt damper. Case study of a base-isolated structure is analyzed in both the frequency and the time domain to investigate the effectiveness of the multi-mode electromagnetic shunt resonances. It is found that both multi-mode resonant shunt circuits outperform single mode resonant shunt circuit by suppressing the primary and the second vibration modes simultaneously. In addition, under the same stiffness ratio, parallel shunt circuit is more effective in energy harvesting and vibration suppression. And parallel shunt circuit is also more robust to parameter mistuning than series shunt circuit. This thesis further experimentally validated the effectiveness of the multimode electromagnetic resonances for vibration damping and energy harvesting using recorded earthquake signals on a scaled-down building.

Instead of dissipating vibration energy into heat waste via viscous damping elements, this dissertation proposes an innovative vibration control method which can simultaneously mitigate vibration and harvest the associated vibration energy using electromagnetic energy harvesters. This dissertation shows that the electromagnetic energy harvester can work as a controllable damper as well as an energy harvester. The semi-active control of a linear electromagnetic energy harvester, for improvement of suspension performance, has been experimentally implemented in a scaled-down quarter-car suspension system. While improving performance, power produced by the harvester can be harvested through energy harvesting circuits. This dissertation also proposes a mechanical-motion-rectifier(MMR)-based electromagnetic energy harvester using a ball-screw mechanism and two one-way clutches for the application of replacing the viscous damper in vehicle suspensions. Compared to commercial linear harvesters, the proposed design is able to provide large damping forces and increase power-dissipation density, making it suitable to vehicle suspensions. In addition, the proposed MMR-based harvester can convert reciprocating vibration into unidirectional rotation of the generator. This feature significantly increases energy-harvesting efficiency by enabling the generator to rotate at a relatively steady speed during irregular vibrations and improves the system reliability by reducing impact forces among transmission gears. Extensive theoretical and experimental analysis have been conducted to characterize the proposed MMR-based energy harvester. The coupled dynamics of the suspension system with the MMR-based energy harvester are also explored and optimized. Furthermore, a new control algorithm is proposed to control the MMR-based energy harvester considering its unique dynamics induced by the one-way clutches. The results show that the controlled proposed electromagnetic energy harvester can possibly improve ride comfort of vehicles over conventional oil dampers and simultaneously harvest the associated vibration energy. / Ph. D. / Instead of dissipating vibration energy into heat waste via viscous damping elements, this dissertation proposes an innovative vibration control method which can simultaneously mitigate vibration and harvest the associated vibration energy using electromagnetic energy harvesters. This dissertation shows that the electromagnetic energy harvester can work as a controllable damper as well as an energy harvester. The semi-active control of a linear electromagnetic energy harvester, for improvement of suspension performance, has been experimentally implemented in a scaled-down quarter-car suspension system. While improving performance, power produced by the harvester can be harvested through energy harvesting circuits. This dissertation also proposes a mechanical-motion-rectifier(MMR)-based electromagnetic energy harvester using a ball-screw mechanism and two one-way clutches for the application of replacing the viscous damper in vehicle suspensions. Compared to commercial linear harvesters, the proposed design is able to provide large damping forces and increase powerdissipation density, making it suitable to vehicle suspensions. In addition, the proposed MMRbased harvester can convert reciprocating vibration into unidirectional rotation of the generator. This feature significantly increases energy-harvesting efficiency by enabling the generator to rotate at a relatively steady speed during irregular vibrations and improves the system reliability by reducing impact forces among transmission gears. Extensive theoretical and experimental analysis have been conducted to characterize the proposed MMR-based energy harvester. The coupled dynamics of the suspension system with the MMR-based energy harvester are also explored and optimized. Furthermore, a new control algorithm is proposed to control the MMR-based energy harvester considering its unique dynamics induced by the one-way clutches. The results show that the controlled proposed electromagnetic energy harvester can possibly improve ride comfort of vehicles over conventional oil dampers and simultaneously harvest the associated vibration energy.

This work examines a novel concept and design of simultaneous energy harvesting and vibration control on the same host structure. The motivating application is a multifunctional composite sandwich wing spar for a small Unmanned Aerial Vehicle (UAV) with the goal of providing self-contained gust alleviation. The basic idea is that the wing itself is able to harvest energy from the ambient vibrations along with available sunlight during normal flight. If the wing experiences any strong wind gust, it will sense the increased vibration levels and provide vibration control to maintain its stability. This work holds promise for improving performance of small UAVs in wind gusts. The proposed multifunctional wing spar integrates a flexible solar cell array, flexible piezoelectric wafers, a thin film battery and an electronic module into a composite sandwich structure. The basic design factors are discussed for a beam-like multifunctional wing spar with load-bearing energy harvesting, strain sensing and self-controlling functions. Three-point bending tests are performed on the composite sandwich structure for bending strength analysis and bending stiffness prediction under a given safety factor. Additional design factors such as the configuration, location and actuation type of each piezoelectric transducer are investigated for optimal power generation. The equivalent electromechanical representations of a multifunctional wing spar is derived theoretically, simulated numerically and validated experimentally. Special attention is given to the development of a reduced energy control (REC) law, aiming to minimize the actuation energy and the dissipated heat. The REC law integrates a nonlinear switching algorithm with a positive strain feedback controller, and is represented by a positive feedback operation amplifier (op-amp) and a voltage buffer op-amp for each mode. Experimental results exhibit that the use of nonlinear REC law requires 67.3 % less power than a conventional nonlinear controller to have the same settling time under free vibrations. Nonlinearity in the electromechanical coupling coefficient of the piezoelectric transducer is also observed, arising from the piezoelectric hysteresis in the constitutive equations coupling the strain field and the electric field. If a constant and voltage-independent electromechanical coupling coefficient is assumed, this nonlinearity results in considerable discrepancies between experimental measurements and simulation results. The voltage-dependent coupling coefficient function is identified experimentally, and a real time adaptive control algorithm is developed to account for the nonlinear coupling behavior, allowing for more accurate numerical simulations. Experimental validations build upon recent advances in harvester, sensor and actuator technology that have resulted in thin, light-weight multilayered composite sandwich wing spars. These multifunctional wing spars are designed and validated to able to alleviate wind gust of small UAVs using the harvested energy. Experimental results are presented for cantilever wing spars with micro-fiber composite transducers controlled by reduced energy controllers with a focus on two vibration modes. A reduction of 11dB and 7dB is obtained for the first and the second mode using the harvested ambient energy. This work demonstrates the use of reduced energy control laws for solving gust alleviation problems in small UAVs, provides the experimental verification details, and focuses on applications to autonomous light-weight aerospace systems. / Ph. D.

Energy harvesting technologies are crucial for the future green transition. Research shows the versatility and efficiency of integrated energy harvesting solutions. Economic advantages, enhanced energy efficiency, and reduced reliance on conventional power sources can be achieved with well implemented systems. Furthermore, there are environmental benefits from using more renewable energy sources due to fewer emissions from battery production and replacement. One of the challenges with system implementation is achieving high efficiency for various energy sources and system loads. This study aimed to showcase the design steps for crucial system blocks to aid in designing complete energy harvesting systems. The designs are done in a 180 nm CMOS process. A literature study, including recent research on capacitive and inductive converters, gave insight into the limitations of the different topologies. The study also included other crucial blocks for efficient energy harvesting systems, such as Maximum power point tracking and cold-start. In the study, commercially available energy harvesting chips are discussed, and it is concluded that the market is limited regarding alternatives for a wide range of systems. A microcontroller is needed for an adaptable system. For the study, an additional aim was to provide support for an MSP430L092, a low-power microcontroller from Texas Instruments. The support included level shifters and supply voltage generation. Due to time constraints, not all blocks were designed. The designed blocks are a boost converter, level shifters and a Pulse-width modulation generation network composed of a comparator and oscillator. Other blocks needed in efficient energy harvesting systems are included as short discussions of possible implementations from other research and commercially available components. Simulation of the boost converter showed that the main losses are from the non ideal inductor. These were minimised by using a higher switching frequency of 1 MHz and allowing a larger inductor ripple current, which allowed for a smaller inductor. From a 500 mV input voltage boosting to a 2 V output voltage with a constant output power of 120 μW an efficiencyof 88.36% was achieved. A high efficiency was achieved down to 300 mV of input voltage. In the pulse-width modulation network simulation, the main losses were found to be from the current spikes in the buffering stages. Higher voltage threshold transistors and smaller widths minimised these issues. Simulation at 1 MHz showed a power consumption of 5 μW for the complete network and a duty cycle range of 28% to 91%. The comparators standalone power consumption was simulated to 2.3 μW. Some deviations from calculations were noted in the oscillator circuit, which was concluded to be an issue due to the heavy power optimisation. It was not investigated any further in this work but left as future work to investigate the comparator further. From simulated data and datasheets, an estimation for the total combined system efficiency is calculated to be 71.3%. Future work includes the layout of the designed blocks to evaluate the impact of the parasitic extraction.

This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

O uso de materiais piezelétricos no desenvolvimento de dispositivos para o aproveitamento de energia provinda de vibrações mecânicas, Energy Harvesting, tem sido largamente estudado na última década. Materiais piezelétricos podem ser encontrados na forma de finas camadas ou pastilhas, sendo facilmente integradas a estruturas sem aumento significativo de massa. A conversão de energia mecânica em energia elétrica se dá graças ao acoplamento eletromecânico dos materiais piezelétricos. A maioria das publicações encontradas na literatura exploram o uso de dispositivos eletromecânicos ressonantes, sintonizados na frequência de operação da estrutura, maximizando assim, a energia elétrica de saída dada uma certa condição de operação. O desempenho desses dispositivos ressonantes para coletar e armazenar energia é altamente dependente da adequada sintonização da sua frequência de ressonância com a frequência de operação do sistema/estrutura. Este trabalho apresenta o projeto, otimização e análise de incertezas de um dispositivo coletor/armazenador de energia que consiste em uma placa sob duas condições de contorno, engastada-livre (EL) e deslizante-livre (DL), com massa sísmica e materiais piezelétricos conectados a um circuito shunt. Um modelo em elementos finitos de placa laminada piezelétrica conectada a circuitos R e RL é utilizado combinando as teorias de camada equivalente e deformação de cisalhamento de primeira ordem. A disposição/quantidade de material piezelétrico bem como a massa sísmica acoplados à estrutura foram otimizadas utilizando-se um Algoritmo Genético, levando em conta análises mecânica (modelo mecânico, geometria, peso) e elétrica (modelo elétrico, circuito armazenador). Além disso, o efeito de incertezas dos parâmetros dielétrico e piezelétrico do transdutor, e da indutância elétrica ligada em série ao circuito coletor/armazenador de energia foi estudado. Os resultados indicam que a inclusão de uma indutância sintética ao circuito pode melhorar a coleta de energia em uma banda de frequência e, ainda, que a otimização geométrica pode reduzir a quantidade de material piezelétrico sem no entanto diminuir significativamente a energia gerada. / The use of piezoelectric materials in the development of devices to harvest energy from mechanical vibrations (Energy Harvesting) has been widely studied in the last decade. Piezoelectric materials can be found in the form of thin layers or patches easily integrated into structures without significant mass increase. The conversion of mechanical energy into electric power is provided by the electromechanical coupling of piezoelectric materials. Most publications in the literature explore the use of resonant electromechanical devices, tuned to the operating frequency of the host structure, thus maximizing the power output given a certain operating condition. The performance of these resonant devices to harvest and store energy is highly dependent on the proper tuning of its resonance frequency with the operation frequency of the system/structure. This work presents a design, optimization and uncertainty analysis of energy harvester device consisting of a plate with tip mass and piezoelectric materials connected to shunt circuits. Two boundary conditions are used for the plate, cantilever (EL) and sliding-free (DL). A coupled finite element model with R and RL circuits, combining equivalent single layer and first order shear deformation theories, was used. The distribution and volume of piezoelectric material and the tip mass coupled to the structure were optimized using a Genetic Algorithm, accounting for both mechanical (mechanical model, geometry, weight) and electric (electric model, storer circuit) analyses. Furthermore, the effect of uncertainties of transducer dielectric and piezoelectric constants and electric inductance connected in series with harvesting circuit was studied. The results indicate that the inclusion of a synthetic inductance can improve energy harvesting performance over a frequency range and also that the geometric optimization may reduce the piezoelectric material volume without diminishing significantly the harvested energy.

An abundance of energy in our environment exists in the form of light, thermal, mechanical (e.g., vibration, sonic waves, wind, and hydraulic), magnetic, chemical, and biological. Harvesting these forms of energy is of critical importance for solving long-term energy needs and the sustainable development of the planet. However, conversion cells for harvesting solar energy and mechanical energy are usually independent entities that are designed and built following distinct physical principles. The effective and complementary use of such energy resources whenever and wherever one or all of them are available demands the development of innovative approaches for the conjunctional harvesting of multiple types of energy using an integrated structure/material. By combining solar and mechanical energy-harvesting modules into a single package for higher energy conversion efficiency and a more effective energy recovery process, the research has designed and demonstrated a hybrid cell for harvesting solar and mechanical energy. The results of the research show that we can fully utilize the energy available from our living environment by developing a technology that harvests multiple forms of both solar and mechanical energy 24 hours a day. As the proposed research represents a breakthrough in the innovation of energy harvesting, it should pave the way toward building a new field called "multi-type hybrid" energy harvesting.