The conventional car suspension system uses isolated shock absorbers that are only capable of dissipating energy in the form of heat. Each shock absorber in a hydraulic interconnected suspension is connected by hydraulic circuits, allowing the electrified hydraulic fluid to be used to counteract undesirable body motion and enhance dynamic performance as a whole. An established idea with good potential for managing body rolling and separating the warp mode from other dynamic modes is the hydraulic interconnected suspension. While certain active or semi-active suspension technologies enable the shock absorbers to compensate for the effects of the road disturbances using external power input, hydraulic linked suspension is still passive and lacks adaptivity. In order to adjust the suspension's damping properties to rapidly changing road conditions, active suspensions, like electromagnetic shock absorbers, utilize the magnetofluid's variable viscosity. In some circumstances, the energy requirement of an active suspension might amount to kilowatts, which lowers the vehicle's fuel efficiency. This research proposes a novel energy-harvesting hydraulically interconnected shock absorber (EH-HISA) system to find a balanced solution to dynamic performance and energy efficiency by incorporating energy harvesting ability to a passive hydraulically interconnected suspension. Improved energy efficiency and vehicle dynamics performance are provided by the features which combine energy harvesting with hydraulic interconnection. AMESim is used to build a single diagonal hydraulic circuit model, which is then validated in a bench test. The theoretical model's validity was established by the bench test results, and the model was then applied to estimate system performance. To verify the effectiveness of the entire system design, a full car model outfitted with EH-HISA is created. For model simulation, various dynamic input scenarios—including sinusoidal input and double lane change tests—are applied. The EH-HISA achieves average lateral acceleration improvements of 38% over traditional suspensions and 11% compared to a prior design (EHHIS proposed by Chen et al.) and average energy harvesting ability improvements of 133 % while maintaining acceptable anti-rolling dynamics in the double lane change test. The EH-HISA also improves the anti-rolling ability by 30 % as compared to traditional suspensions. The power generated is found to reach maximum of 210 W at 2 Hz and 20 mm sinusoidal input. Bench tests are performed on the EH-HISA prototype to validate the simulation results. Damping force and energy harvesting experimental data is measured and compared with the simulation results to validate the effectiveness of the system. / Master of Science / The vehicle industry has always sought improved road handling dynamics and riding comfort. The vehicle body may move in a variety of ways, including roll, pitch, and bounce; each of these motions can endanger passengers' safety and lead to passenger fatigue. Oil shock absorbers that are isolated from the rest of the vehicle's suspension system can only dissipate energy by forcing oil via dampening valves. A hydraulic interconnected suspension can connect each shock absorber using hydraulic circuits so that the energized hydraulic fluid can be used to reduce unwanted body motion and enhance the overall riding experience. A tried-and-true idea, the hydraulic interconnected suspension (HIS), has shown promising results in stabilizing the vehicle body on unsteady roads. While active suspensions, like electro-magnetic shock absorbers, can employ an external power source to compel them to adjust to rapidly changing road conditions, hydraulic linked suspension is still passive and unadaptive. In some circumstances, the energy requirement of an active suspension might amount to kilowatts, which lowers the vehicle's fuel efficiency. Additionally, there is always a chance that a system that is actively receiving power will malfunction as a result of a power outage. This research offers a new type of energy-harvesting hydraulically interconnected shock absorber (EH-HISA) system to achieve a balanced solution to dynamic performance and energy efficiency. The combined energy-harvesting and HIS system provide improved energy efficiency as well as vehicle dynamics performance. Each system is composed of two distinct diagonal hydraulic circuits which interconnect the shock absorbers of the diagonal wheels in a vehicle. AMESim is used to build a single diagonal hydraulic circuit model, which is then validated in experiments, as a starting point for investigating the effectiveness of the overall system. The theoretical model's validity was established by the outcomes of the bench tests, and the model was then utilized to predict system performance. A full car model is created based on the tested single diagonal hydraulic circuit model to assess the performance of the entire system architecture. Different road condition scenarios are used for model simulation, which includes sinusoidal input and double lane change test. The EH-HISA achieves average lateral acceleration improvements of 38% over traditional suspensions and 11% compared to a prior design (EHHIS proposed by Chen et al.) and average energy harvesting ability improvements of 133 % while maintaining acceptable anti-rolling dynamics in the double lane change test. The EH-HISA also improves the anti-rolling ability by 30 % as compared to traditional suspensions. The power generated is found to reach maximum of 210 W at 2 Hz and 20 mm sinusoidal input. Bench tests are performed on the EH-HISA prototype to validate the simulation results. Damping force and energy harvesting experimental data is measured and compared with the simulation results to validate the effectiveness of the system.

No description available.

Oscillating heat pipes (OHPs) have been actively investigated since their inception due to their ability to manage high heat/heat fluxes. The OHP is a passive, wickless, two-phase heat transfer device that relies on pressure driven fluid oscillations within a hermetically-sealed serpentine channel structure. The cyclic phase-change heat transfer drives additional sensible heat transfer, and this combination causes OHPs to have high effective thermal conductivities. Many strides have been made, through both experimentation and modeling, to refine the design and implementation of OHPs. However, the main objective in OHP research has been to better understand the thermodynamic and fluid mechanic phenomena so as to enhance OHPs' thermal performance. The current work presents methods for using OHP in thermal-to-electric energy harvesting, which would allow for ‘dual-purpose’ OHP applications in which thermal management can be combined with work output. Energy harvesting occurred when a portion of the thermally-driven fluidic motion was used to generate a voltage either by electromagnetic induction or by a piezoelectric transducer imbedded in an OHP tube. For the induction approach, two methods were used to create the time-varying magnetic field required for induction. In the first, a ferrofluid was used as the OHP working fluid. Because the magnetic dipoles of the nanoparticles are randomly aligned naturally, two static, external ‘bias’ magnets were required to create a uniform magnetic field to align the particle dipoles for a non-zero magnetic flux change through a coaxial solenoid. The second method used a small rare-earth magnet confined inside a set length of an OHP channel that had a coaxial solenoid. As the OHP working fluid moved inside the harvesting channel, a portion of the fluid's momentum was transferred to the magnet, causing it to oscillate. For the piezoelectric approach, a narrow piezoelectric transducer was placed in a bow-shaped configuration along the inside of an OHP channel. Passing fluid would deflect the piezo creating a potential difference across its leads, which protruded out of the channel walls. All three of these methods successfully produced a voltage while retaining the excellent thermal performance synonymous with OHPs.

No description available.

<p>    </p> <p>An energy harvesting system (EHS) provides the intriguing possibility of battery-less computing and enables various applications such as wearable, industrial or environmental sensors, and im- plantable medical devices. The biggest challenge of EHS is the instability of energy sources (e.g., Wi-Fi, solar, thermal energy, etc.) which causes unpredictable and frequent power outages. To address the challenge, existing works introduce software-based and hardware-based power failure recovery solutions that ensure program correctness across a power outage. However, they cause a significant performance overhead without providing the high quality of service in reality, and suffer from a reliability issue. In this dissertation, we address the limitations of recovery solutions across the system stack, from the compiler-directed approach and run-time systems to hardware mechanisms, and demonstrate the effectiveness of the approaches using real EHS platforms and simulators. We first present software-based recovery solutions by leveraging compiler support. We develop a compiler-directed solution built upon commodity EHS platform that can achieve 3X speedup compared to the software-based state-of-the-art solution. We also introduce a compiler optimization technique that can cooperate with run-time systems and hardware support, achieving 8X speedup compared to the software-based solution. We then present hardware-based recov- ery solutions by leveraging compiler and hardware support. We develop an architecture/compiler co-design solution that re-purposes existing hardware components in a core for power failure spec- ulative execution, a new speculation paradigm, and leverages a novel compiler analysis for cor- rect power failure recovery. Our result highlights 2 ∼ 3x performance improvement compared to the hardware-based state-of-the-art solution without requiring hardware modification. Next, we present a new cache design for EHS that can achieve cost-effective, high-performance intermit- tent computing. According to experimental results, the new cache design outperforms the state- of-the-art cache scheme by 4X and reduces the hardware cost by 90%. Finally, we present an operating system (OS)-driven solution to address a reliability problem on EHS devices while all existing works are vulnerable, causing the wrong recovery across power failure. Our experiments demonstrate that the solution causes less than 1% run-time overhead and successfully addresses the reliability problem without compromising correct power failure recovery. </p>

Wireless network for connecting the devices and sensors to communicate and sense is quite attractive nowadays for a wide range of applications. The scaling of the wireless network to millions of nodes currently is impractical if the process is supplied by battery energy. The batteries need to be periodically replaced or recharged due to the limited battery size. One solution is harvesting ambient energy to power the network. In this thesis, we consider a battery-limited energy harvesting communication system with online power control. Assuming independent and identically distributed (i.i.d.) energy arrivals and the harvest-store-use architecture, it is shown that the greedy policy achieves the maximum throughput if and only if the battery capacity is below a certain positive threshold that admits a precise characterization. Simple lower and upper bounds on this threshold are established. The asymptotic relationship between the threshold and the mean of the energy arrival process is analyzed for several examples. Furthermore, value iteration method is applied for solving the Bellman equation to obtain the optimal power allocation policy. The optimal policy is analyzed for several examples. / Thesis / Master of Applied Science (MASc)

One of the untapped energy sources is the thermal energy available either from solar irradiance which is still not fully utilized or from the ambient heat temperature. Both resources share the nature of infrared (IR) radiation but with different range of wavelengths. The rectenna (rectifying antenna) concept is presented to harvest these IR radiations. The rectenna is simply an antenna connected to a diode. The diode has to be able to follow and rectify the ultra-fast received AC signal. This condition promotes the use of metal-insulator-metal (MIM) diodes due to their ultra-fast tunneling mechanism. The impedance matching between the diode an antenna is to be considered. The resistance practical ranges of both nano-antenna and MIM diode are generally far. The diode responsivity determines the MIM rectification capability. By building MIM diodes with multiple insulator layers the trade-off between the resistance and responsivity can be resolved. An optimization algorithm to select the qualified materials to build an MIIM diode with high responsivity and low resistance is introduced. A Ti-TiO2/ZnO-Al MIIM diode with ultra-thin oxide layers is fabricated. Also, a global optimization approach is carried out to maximize the impedance matching between the diode and the nano-antenna while improving the capacitance effect on the device’s cut-off frequency. The optimal results reveal a maximum coupling efficiency of 5.5%, a responsivity of 6.4 A/W, and a cut-off frequency of ~34 THz. A symmetric MIM metamaterial perfect absorber is introduced. The design has larger resistance than conventional nano-antennas. The near unity absorptivity is achieved through an optimization approach. A novel Chand-Bali nano-antenna that supports dual polarization and wide angle of reception is presented. The rectenna based on this nano-antenna is expected to achieve more than one magnitude of efficiency higher than ones fabricated in literature. / Thesis / Doctor of Philosophy (PhD)

Vibration-based energy harvesting has been investigated by several researchers over the last decade. The ultimate goal in this research field is to power small electronic components (such as wireless sensors) by using the vibration energy available in their environment. Among the basic transduction mechanisms that can be used for vibration-to-electricity conversion, piezoelectric transduction has received the most attention in the literature. Piezoelectric materials are preferred in energy harvesting due to their large power densities and ease of application. Typically, piezoelectric energy harvesters are cantilevered structures with piezoceramic layers that generate alternating voltage output due to base excitation. This work presents distributed-parameter electromechanical models that can accurately predict the coupled dynamics of piezoelectric energy harvesters. First the issues in the existing models are addressed and the lumped-parameter electromechanical formulation is corrected by introducing a dimensionless correction factor derived from the electromechanically uncoupled distributed-parameter solution. Then the electromechanically coupled closed-form analytical solution is obtained based on the thin-beam theory since piezoelectric energy harvesters are typically thin structures. The multi-mode electromechanical frequency response expressions obtained from the analytical solution are reduced to single-mode expressions for modal vibrations. The analytical solutions for the electromechanically coupled voltage response and vibration response are validated experimentally for various cases. The single-mode analytical equations are then used for deriving closed-form relations for parameter identification and optimization. Asymptotic analyses of the electromechanical frequency response functions are given along with expressions for the short-circuit and the open-circuit resonance frequencies. A simple experimental technique is presented to identify the optimum load resistance using only a single resistor and an open-circuit voltage measurement. A case study is given to compare the power generation performances of commonly used monolithic piezoceramics and novel single crystals with a focus on the effects of plane-stress material constants and mechanical damping. The effects of strain nodes and electrode configuration on piezoelectric energy harvesting are discussed theoretically and demonstrated experimentally. An approximate electromechanical solution using the assumed-modes method is presented and it can be used for modeling of asymmetric and moderately thick energy harvester configurations. Finally, a piezo-magneto-elastic energy harvester is introduced as a non-conventional broadband energy harvester. / Ph. D.

This work focuses on the broadband attenuation of structural vibration and, in the process, employs a new perspective of vibrational energy harvesting devices. The first part of the research studies and develops a continuously distributed vibration control device which combines the benefits of point mass-spring-dampers at low frequencies as well as the resistive or dissipative influence of constraining treatments at high frequencies. This embodiment provides broadband passive vibration attenuation for a minimal cost in added mass, spanning the present divide between the ability to attenuate a single low frequency and the need to attenuate all frequencies. The second part adopts a vibration control perspective to energy harvesting analysis and considers the harvesting devices to be electromechanically stiffened and/or damped vibration absorbers. Rigorous analysis and experiments are carried out which show that vibration control and energy harvesting appear to be mutually beneficial given that maximum harvested energy from structural vibrations is achieved when the harvesters exert a finite dynamic influence on the host system. This suggests that vibration control concerns presently alleviated using tuned-mass-dampers are ideal energy harvesting applications. A generalized analytical model is derived which is applicable to both portions of the work. Continuously distributed vibration control devices are studied in depth and a superposition method is presented which allows for convenient implementation of a realistic device design into the numerical model. Tests carried out with the distributed device validate the model as well as show the device's competitive benefits compared with traditional, and much heavier, vibration control treatments. The inclusion of electromechanical coupling effects into the modeling is straightforward and numerous analyses are carried out to observe how electromagnetic and piezoelectric energy harvesting devices affect the dynamics of the host vibrating structure while the harvesters themselves convert the 'absorbed' energy into electrical power. Altering the device created in the first portion of the research to use a piezoelectric material as the distributed spring yields one such embodiment capable of both surface vibration control and energy harvesting. Tests carried out with the device additionally serve as model validation but also indicate that, for a given harvester, the attenuation of and energy harvesting from structural vibrations are nearly simultaneously maximized as modeling predicted. / Ph. D.

This dissertation investigates the nonlinear wave propagation phenomena in nonlinear metamaterials with nonlinear chains and nonlinear resonators using analytical and spectro-spatial analyses. In the first part of the thesis, the nonlinear metamaterials are modeled as a chain of masses with multiple local resonators attached to each cell. The nonlinearity stems from the chain's stiffness in one case and the local resonator's stiffness in another. Analytical approximates solutions are obtained for each case using perturbation techniques. These results are validated through numerical simulations and the results show good agreement. To further demonstrate the nonlinear wave propagation characteristics, spectro-spatial analyses are conducted on the numerical integration data sets. The wave profiles, short-term Fourier transform spectrograms, and contour plots of 2D Fourier transform show the presence of solitary waves for both sources of nonlinearity. In addition, spectro-spatial features demonstrate the presence of significant frequency shifts at different wavelength limits. indent The second part of the thesis studies a nonlinear electromechanical metamaterial and examines how the electromechanical coupling in the local resonator affects the wave propagation. Numerical examples indicate that the system can be used for simultaneous energy harvesting and vibration attenuation without any degradation in the size of bandgaps. Spectro-spatial analyses conducted on the electromechanical metamaterial also reveal the presence of solitons and frequency shifts. The presence of solitary wave in the electromechanical metamaterial suggests a significant improvement in energy harvesting and sensing techniques. The obtained significant frequency shift is employed to design an electromechanical diode, allowing voltage to be sensed and harvested only in one direction. Design guidelines and the role of different key parameters are presented to help designers to select the type of nonlinearity and the system parameters to improve the performance of acoustic diodes. indent The last part of this thesis studies the passive self-tuning of a metastructure via a beam-sliding mass concept. The governing equations of motions of the holding structure, resonator, and sliding mass are presented and discretized into a system of ODEs using Galerkin's projection. Given that the spatial parameters of the system continuously change over time (i.e., mode shapes and frequencies), instantaneous exact mode shapes and frequencies are determined for all possible slider positions. The numerical integration is conducted by continuously updating the spatial state of the system. The obtained exact mode shapes demonstrate that the resonance frequency of the resonator stretches over a wide frequency band. This observation indicates that the resonator can attenuates vibrations at a wide frequency range. Experiments are also conducted to demonstrate the passive self-tunability of the metastructure and the findings colloborate the analytical results. / Doctor of Philosophy / Metamaterials are artificially engineered structures that can offer incredible dynamical properties, which cannot be found in conventional homogeneous structures. Consequently, the global metamaterials market is expected to display a 23.6$%$ compound annual growth rate through 2027. Some of these exciting properties include, but not limited to, negative stiffness, negative mass, negative Poisson's ratio. The unique dynamic properties show the importance of metamaterials in many engineering applications, such as vibration reduction, noise control, and waveguiding and localization. However, beyond the linear characteristics of metamaterials, nonlinear metamaterials can exhibit more interesting nonlinear wave propagation phenomena, such as solitons, cloaking, tunable bandgaps, and wave non-reciprocity. indent This research work investigates wave propagation characteristics in nonlinear locally resonant metamaterials using analytical, numerical, and signal processing techniques. The nonlinearity stems from the chain in one case and from the local resonator in another. Numerical examples show the presence of solitary waves in both types of nonlinearity and significant frequency shift in certain frequency/wavenumber regions. The obtained significant frequency shift can be utilized to design mechanical diodes, where its operation range can be increased by introducing nonlinearity in the resonator. indent For simultaneous energy harvesting and vibration attenuation, integrating the local resonator with piezoelectric energy harvesters is also investigated in this research work with the presence of both types of nonlinearities. For weak electromechanical coupling, the results demonstrate that the band structure of the system is not affected by the electromechanical coupling. Therefore, the system can also be used for energy harvesting without any degradation in the vibration attenuation performance. This observation is also validated experimentally for the linear limit. Spectro-spatial analyses also reveal the presence of solitary output voltage waves, which can enhance the energy harvesting and sensing. The obtained significant frequency shift can be utilized to design an electromechanical diode where the wave can propagate and be harvested only in one direction. Numerical examples show that the performance of the electromechanical diode can be significantly improved by including nonlinearities in the local resonator. indent Another goal of this research work is the introduction of passive self-tuning mechanism to design self-tuning metastructure. The design of such a metastructure is motivated by the need for broadband devices that can adapt to changing environment. The passive self-tuning concept is achieved by a sliding mass coupled with a resonator. Analytical and experimental results show the ability of this system to tune itself to the excitation frequency, and hence, can control vibrations over a significantly wider frequency band as compared to conventional resonators.