Дисертації з теми "Harvester interface"

The research topic is developping a power converting interface for the novel FLEHAP wind energy harvester allowing the produced energy to be used for powering small wireless nodes. The harvester’s electrical characteristics were studied and a strategy was developped to control and mainting a maximum power transfer. The electronic power converter interface was designed, containing an AC/DC Buck-Boost converter and controlled with a low power microcontroller. Different prototypes were developped that evolved by reducing the sources of power loss and rendering the system more efficient. The validation of the system was done through simulations in the COSMIC/DITEN lab using generated signals, and then follow-up experiments were conducted with a controllable wind tunnel in the DIFI department University of Genoa. The experiment results proved the functionality of the control algorithm as well as the efficiency that was ramped up by the hardware solutions that were implemented, and generally met the requirement to provide a power source for low-power sensor nodes.

For many years batteries have been used as the main power sources for portable electronic devices. However, the rate of scaling in integrated circuits and micro-electro-mechanical systems (MEMS) has been much higher than that of the batteries technology. Therefore, a need to replace these temporary energy reservoirs with small sized continuously charged energy supply units has emerged. These units, named as energy harvesters, use several types of ambient energy sources such as heat, light, and vibration to provide energy to intelligent systems such as sensor nodes. Among the available types, vibration based electromagnetic (EM) energy harvesters are particularly interesting because of their simple structure and suitability for operation at low frequency values (<
10 Hz), where most vibrations exits. However, since the generated EM power and voltage is relatively low at low frequencies, high performance interface electronics is required for efficiently transferring the generated power from the harvester to the load to be supplied. The aim of this study is to design low power and efficient interface electronics to convert the low voltage and low power generated signals of the EM energy harvesters to DC to be usable by a real application. The most critical part of such interface electronics is the AC/DC converter, since all the other blocks such as DC/DC converters, power managements units, etc. rely on the rectified voltage generated by this block. Due to this, several state-of-the-art rectifier structures suitable for energy harvesting applications have been studied. Most of the previously proposed rectifiers have low conversion efficiency due to the high voltage drop across the utilized diodes. In this study, two rectifier structures are proposed: one is a new passive rectifier using the Boot Strapping technique for reducing the diode turn-on voltage values
the other structure is a comparator-based ultra low power active rectifier. The proposed structures and some of the previously reported designs have been implemented in X-FAB 0.35 µ
m standard CMOS process. The autonomous energy harvesting systems are then realized by integrating the developed ASICs and the previously proposed EM energy harvester modules developed in our research group, and these systems have been characterized under different electromechanical excitation conditions. In this thesis, five different systems utilizing different circuits and energy harvesting modules have been presented. Among these, the system utilizing the novel Boot Strap Rectifier is implemented within a volume of 21 cm3, and delivers 1.6 V, 80 µ
A (128 µ
W) DC power to a load at a vibration frequency of only 2 Hz and 72 mg peak acceleration. The maximum overall power density of the system operating at 2 Hz is 6.1 µ
W/cm3, which is the highest reported value in the literature at this operation frequency. Also, the operation of a commercially available temperature sensor using the provided power of the energy harvester has been shown. Another system utilizing the comparator-based active rectifier implemented with a volume of 16 cm3, has a dual rail output and is able to drive a 1.46 V, 37 µ
A load with a maximum power density of 6.03 µ
W/cm3, operating at 8 Hz. Furthermore, a signal conditioning system for EM energy harvesting has also been designed and simulated in TSMC 90 nm CMOS process. The proposed ASIC includes a highly efficient AC-DC converter as well as a power processing unit which steps up and regulates the converted DC voltages using an on-chip DC/DC converter and a sub-threshold voltage regulator with an ultra low power management unit. The total power consumption on the totally passive IC is less than 5 µ
W, which makes it suitable for next generation MEMS-based EM energy harvesters. In the frame of this study, high efficiency CMOS rectifier ICs have been designed and tested together with several vibration based EM energy harvester modules. The results show that the best efficiency and power density values have been achieved with the proposed energy harvesting systems, within the low frequency range, to the best of our knowledge. It is also shown that further improvement of the results is possible with the utilization of a more advanced CMOS technology.

Wireless Sensor Networks (WSNets), consisting of a lot of Wireless Sensor Nodes (WSNs), play an important role in structural health and machine condition monitoring. But the WSNs provided by the current market cannot meet the diversity of application requirements because they have limited functions, unreliable node performance, high node cost, high system redundancy, and short node lifespan. The aim of the research is to design the architecture of a WSN with low power consumption and node cost, which can be dynamically configured according to application requirements for structural health and machine condition monitoring. This research investigates the improvement of node performance and reliability through the new design methodologies and the extension of node lifespan by interfacing energy harvesters and implementing node power management. The main contributions of the research are presented from the following aspects:1. Model development of node architecture for application diversityThe merits of model include: (1) The proposed node architecture can be dynamically configured in terms of application requirements for reducing system redundancy, power consumption and cost; (2) It supports multichannel signal measurement with the synchronous and asynchronous signal sampling modules and three interface circuits; (3)The model parameters can be calculated; (4) As the model is based on discrete electronic components, it can be implemented by using Components-Off-The-Shelf (COTS).2. A novel pipeline design of the built-in ADC inside a microprocessorThe merit of proposed pipeline solution lies in that the sampling time of the built-in ADCs is reduced to one third of the original value, when the ADC operates in sequence sampling mode based on multichannel signal measurement.3. Self-adjusting measurement of sampled signal amplitude This work provides a novel method to avoid the distortion of sampled signals even though the environmental signal changes randomly and over the sampling range of the node ADC. The proposed method can be implemented with four different solutions.4. Interface design to support energy harvesting The proposed interface will allow to: (1) collect the paroxysmal ambient energy as more as possible; (2) store energy to a distribution super-capacitor array; (3) harvest electrical energy at high voltage using piezoelectric materials without any transformer; (4) support the diversity of energy transducers; and (5) perform with high conversion efficiency.5. A new network task scheduling model for node wireless transceiver The model allows to: (1) calculate node power consumption according to network task scheduling; (2) obtain the optimal policy for scheduling network task.6. A new work-flow model for a WSN The model provides an easy way to (1) calculate node power consumption according to the work flow inside a WSN; (2) take fully advantage of the power modes of node electronic components rather than outside factors; (3) improve effectively node design.

The fourth industrial revolution is here and with it a tidal wave of challenges for its prosperous implementation. One of the greatest challenges frustrating the development of the internet of things, and hence the next industrial revolution, is the powering of wireless sensors, as these depend on batteries with a limited lifetime. Recent advances have shown that energy harvesting technologies can be employed to extend the lifetime of batteries and ultimately replace them, thus facilitating the deployment of autonomous self-powered sensors, key components of the internet of things. Energy harvesting is the process of capturing ambient energy and convertingit into electric power. For energy harvesting devices it is crucial that the transduction of energy is as efficient as possible, meaning that the methods for capturing, interfacing and converting the ambient energy should be understood and characterized for every application. This thesis investigates the harvesting of the energy found in pressure fluctuations in hydraulic systems, a widely used power transmission system used in the industry and consumer applications; the focus is on the fluid interface and energy focusing methods. In summary, the contributions in this thesis show that the methods for converting pressure fluctuations in hydraulic systems to electrical power depend on the hydraulic system environment, in essence, the static pressure and the frequency of the pressure fluctuations. The results can serve as a starting point in the research, design, and development of hydraulic pressure energy harvesters.
Den fjärde industriella revolutionen är här vilket innebär en rad utmaningar för att dess utveckling ska bli framgångsrik. En av de största utmaningarna som begränsar utvecklingen av sakernas internet för industriella tillämpningar är strömförsörjningen av trådlösa sensorer då dessa är beroende av batterier med begränsad livslängd. Nya framsteg har emellertid gjorts med tekniker för energiskördning som gör att livslängden för batterierna kan förlängas ochi förlängningen helt ersätta batterierna. Det, i sin tur, möjliggör autonoma sensorer som är självförsörjande på energi som är viktiga komponenter i sakernas internet. Energiskördning är den process som omvandlar energi som finns i omgivningen till elektrisk energi. För att kunna få ut så mycket energi som möjligt så är det avgörande att energiskördarna gör energiomvandlingen så effektivt som möjligt. Det gör att inhämtning av omgivande energi samt gränssnitt och energiomvandling måste förstås och karakteriseras för varje tillämpning. Den här avhandlingen undersöker energiskördning för hydrauliskasystem där tryckfluktuationer i dessa system är energikällan. Syftet med den här studien är att ta fram metoder för uppskattning och karakterisering av de nödvändiga gränssnitten för inhämtning, fokusering, och omvandling av fluktuationer i hydraultryck till elektrisk energi. Sammanfattningsvis visar avhandlingen att metoder för att omvandla tryckfluktuationer i hydraulsystem till elektrisk energi beror på den hydrauliska systemmiljön där det statiska trycket och frekvensen av tryckfluktuationerna är de viktigaste parametrarna. Resultaten kan fungera som utgångspunkt för fortsatt forskning och utveckling av energiskördare för hydrauliska system.
SMART (Smarta system och tjänster för ett effektivt och innovativt samhälle)

Motion-driven energy harvesters can replace batteries in low power wireless sensors, however selection of the optimal type of transducer for a given situation is difficult as the performance of the complete system must be taken into account in the optimisation. In this thesis, a complete piezoelectric energy harvester system model including a piezoelectric transducer, a power conditioning circuit, and a battery, is presented allowing for the first time a complete optimisation of such a system to be performed. Combined with previous work on modelling an electrostatic energy harvesting system, a comparison of the two transduction methods was performed. The results at 100 Hz indicate that for small MEMS devices at low accelerations, electrostatic harvesting systems outperform piezoelectric but the opposite is true as the size and acceleration increases. Thus the transducer type which achieves the best power density in an energy harvesting system for a given size, acceleration and operating frequency can be chosen. For resonant vibrational energy harvesting, piezoelectric transducers have received a lot of attention due to their MEMS manufacturing compatibility with research focused on the transduction method but less attention has been paid to the output power electronics. Detailed design considerations for a piezoelectric harvester interface circuit, known as single-supply pre-biasing (SSPB), are developed which experimentally demonstrate the circuit outperforming the next best known interface's theoretical limit. A new mode of operation for the SSPB circuit is developed which improves the power generation performance when the piezoelectric material properties have degraded. A solution for tracking the maximum power point as the excitation changes is also presented.

碩士
國立臺灣大學
應用力學研究所
96
This thesis studies energy harvesting using piezoelectric elements as energy transducer materials. The ambient vibration energy is transmitted into electrical energy via electromechanical coupling. The harvested energy is further stored by choosing suitable energy harvesting circuits. Here we propose an appropriate physical model accounting for the effect of electronic interfaces on the harvested power output. We analyze the behavior of energy harvesting system for two different electronic circuits. One is the standard interface and the other is the relatively new interface called SSHI (synchronized switch harvesting on inductor). In each circuit, two different magnitudes of electromechanical coupling piezoelectric materials are adopted and studied. In the case of standard interface, it is found that there is only a single peak for optimal power when the coupling effect is in the medium range. On the other hand, there is a pair of optimal power for the case of strongly coupled electromechanical system. Further, it is found that there is always a single peak of power in the case of SSHI system. In this case, the output power drops significantly when the applied frequency deviates from the resonance, in particular, in the case of strongly coupled materials. Therefore, the desired output power for the SSHI system is in the case of mid-range of electromechanical coupling. The effect of diode loss is also studied here via experiment. This effect is significant when the applied frequency is close to the short circuit resonance in both cases of standard and SSHI interfaces. One approach to overcome it is to increase the magnitude of applied acceleration. Finally, the piezoelectric elements in series and parallel forms are proposed to enhance the output power.

碩士
國立成功大學
電機工程學系
103
In this thesis, TSMC 0.18-μm 1P6M process is applied to implement the design of the energy harvesting interface circuits. A multi-switched inductor technology is proposed to improve the conversion efficiency of the interface circuit power and the harvesting output power. The loss of the traditional switching inductor can be improved by the multi-switching control technologies to lower the maximal inductor current. Moreover, a self-startup is included to fulfill battery-free piezoelectric systems, so the energy harvesting technologies can be applied more widely. The overall energy harvesting interface circuit consists of a negative voltage conversion (NVC) circuit, a switching inductance circuit, a startup circuit, and a multiple switching control logic circuit. The measured results of the proposed piezoelectric interface circuits show that the energy harvester can scavenge power of 100 μW to 1 mW. The loss of the traditional switching inductor can be improved by the multi-switching control technologies. The peak conversion efficiency can be achieved to 86.3%. The overall chip area is 0.672 mm × 0.563 mm.

In this thesis a piezoelectric energy harvesting system, responsible for regulating the power output of a piezoelectric transducer subjected to ambient vibration, is designed to power an RF receiver with a 6 mW power consump-tion. The electrical characterisation of the chosen piezoelectric transducer is the starting point of the design, which subsequently presents a full-bridge cross-coupled rectifier that rectifies the AC output of the transducer and a low-dropout regulator responsible for delivering a constant voltage system output of 0.6 V, with low voltage ripple, which represents the receiver’s required sup-ply voltage. The circuit is designed using CMOS 130 nm UMC technology, and the system presents an inductorless architecture, with reduced area and cost. The electrical simulations run for the complete circuit lead to the conclusion that the proposed piezoelectric energy harvesting system is a plausible solution to power the RF receiver, provided that the chosen transducer is subjected to moderate levels of vibration.

碩士
國立臺灣大學
應用力學研究所
103
The thesis introduces the Laboratory Virtual Instrumentation Engineering Workbench(LabVIEW) programming to integrate both hardware and software into a single interface for experimental facilitation. It also proposes an improvement on the control circuit of parallel-SSHI (Synchronized Switch Harvesting on Inductor) interface. Both techniques are applied to an array of piezoelectric energy harvesters with purposes on either power boosting or broadband improvement. The thesis consists of LabVIEW programming, experiment and data analysis. With LabVIEW programming applied to an array system, a single interface is introduced for controlling both signal output and data acquisition of oscillators and SSHI switch signals. As a result, it is found that compared to the traditional experimental framework with handwritten records, 50% to 75% of time can be saved and the accuracy of measurement on output signals is increased too. The proposed framework is applied to the case of the three piezoelectric oscillators connected to the standard or parallel-SSHI interfaces. When the resonance of each oscillator is almost identical, harvested power is almost three times higher than that of a single oscillator. On the other hand, bandwidth is improved for slightly differences in the resonance of each oscillator. The result shows 70% increase of bandwidth in the array system. In particular, the parallel connection of array system attached to the parallel-SSHI interface exhibits the best performance in both power boosting and wideband improvement. Finally, it is found that the deviations in piezoelectric and dielectric material constants of each oscillator have little effect on power reduction. In contrast, the electromechanical coupling factor and the deviations in resonance of each oscillator have crucial impact on the drop in peak power. The results show that under 2% deviation in resonance, there is 20% power reduction in an array system with high electromechanical coupling. However, harvested power is reduced to 50% for a weak electromechanical coupling system.