With an explosion of the internet of things, energy harvesting provides an environmentally friendly solution to replace consumable batteries in powering wireless sensors. The goal of the research is to bridge a fundamental disconnection in the state-of-the-art understanding of dynamic, multiphysics interplay in vibration energy harvesting systems. In this spirit, vibration energy harvesting systems that integrate structural and electrical nonlinearities are examined to create knowledge on intricate dynamics when subjected to complex vibration environments. The revealed principles may build foundations for techniques to capitalize on synergistic dynamic responses and deliver sustainable robust DC power. In the dissertation, theoretical frameworks that synthesize the mechanical and electrical nonlinearities have been established to examine the intricate dynamics of the integrated nonlinear energy harvesting system. The proposed analytical formulations have been validated by experiments and present particular efficacy to probe the nonlinear dynamics and regulated electrical power, which may help guide the design and deployment of nonlinear energy harvesting systems under complex vibration environments. Moreover, the principles of impedance have been employed to scrutinize the energy transfer in the complex and nonlinear multiphysics network to shed light on strategies for maximizing the energy conversion efficiency of the integrated nonlinear energy harvesting system. The uncovered dynamical characteristics and optimal strategies facilitate insights on the suitable integration of sub-systems and assist in the development and deployment of high-efficiency and sustainable energy harvesting systems. The new knowledge on the system-level harvester implementation may also guide the advancements of other fields, where wireless sensor networks are possibly deployed, such as medical implantation, civil infrastructure health monitoring, and wildlife tracking.

This research also advances the understanding of how magnetic force interactions in vibration energy harvesting systems may convert impulsive environmental energies into DC power, and closes additional knowledge gaps on the effective integration of such system characteristics. A model is constructed of a multi degree-of-freedom energy harvesting systems and rectification circuitry that converts impulsive inputs into rectified voltage. By studying the roles of the magnetic coupling and dynamic response, the advantages of asymmetries are revealed and quantified with respect to conventional nonlinear energy harvesting structures and symmetric system compositions. All together, the results of this research may be used to advance continued efforts that investigate the interaction between structural and electrical nonlinearities of energy harvesting systems operated in practical, complex excitation environments. The practical knowledge created from this research may also guide the transfer of the fundamental design and dynamics principles studied here into concepts for future energy harvesting technologies.

The transformation of vibrations into electric energy through the use of piezoelectric devices is an exciting and rapidly developing area of research with a widening range of applications constantly materialising. With Piezoelectric Energy Harvesting, world-leading researchers provide a timely and comprehensive coverage of the electromechanical modelling and applications of piezoelectric energy harvesters. They present principal modelling approaches, synthesizing fundamental material related to mechanical, aerospace, civil, electrical and materials engineering disciplines for vibration-based energy harvesting using piezoelectric transduction. Piezoelectric Energy Harvesting provides the first comprehensive treatment of distributed-parameter electromechanical modelling for piezoelectric energy harvesting with extensive case studies including experimental validations, and is the first book to address modelling of various forms of excitation in piezoelectric energy harvesting, ranging from airflow excitation to moving loads, thus ensuring its relevance to engineers in fields as disparate as aerospace engineering and civil engineering. Coverage includes: Analytical and approximate analytical distributed-parameter electromechanical models with illustrative theoretical case studies as well as extensive experimental validations Several problems of piezoelectric energy harvesting ranging from simple harmonic excitation to random vibrations Details of introducing and modelling piezoelectric coupling for various problems Modelling and exploiting nonlinear dynamics for performance enhancement, supported with experimental verifications Applications ranging from moving load excitation of slender bridges to airflow excitation of aeroelastic sections A review of standard nonlinear energy harvesting circuits with modelling aspects.

The problem of a scalable energy supply is one of the biggest issues in miniaturizing electronic devices. Advances in technology have reduced the power consumption of electronic devices such as wireless sensors, data transmitters, and medical implants to the point where harvesting ambient vibration, a universal and widely available source of energy, has become a viable alternative to costly and bulky traditional batteries. However, implementation of vibratory energy harvesters is currently impeded by three main challenges: broadband harvesting, low-frequency harvesting at small (micro) scales, and robust energy harvesting at presence of parametric uncertainties. This thesis investigates two main directions for effective vibration energy harvesting: (i) fundamental limits to nonlinear energy harvesting and techniques to approach them, and (ii) robust energy harvesting under uncertainties. As well as being of fundamental scientific interest, understanding maximal power limits is essential for assessment of the technology potential and it also provides a broader perspective on the current harvesting mechanisms and guidance in their improvement. We begin by developing a general framework and model hierarchy for the derivation of fundamental limits of the nonlinear energy harvesting rate based on Euler-Lagrangian variational approach. The framework allows for an easy incorporation of almost any constraints and arbitrary forcing statistics and represents the maximal harvesting rate as a solution of either a set of DAEs or a standard nonlinear optimization problem. Closed-form expressions are derived for two cases of damping-dominated and displacement-constrained motion. Stemming from the study of fundamental limits, we present an almost-universal strategy termed buy-low-sell-high (BLSH) to maximize the harvested energy for a wide range of set-ups and excitation statistics. We further propose two techniques to realize the non-resonant BLSH strategy, namely latch-assisted harvester and adaptive bistable harvester. To validate the efficacy of the proposed strategy and practical techniques, we perform a simulation experiment by exposing the said harvesters to harmonic and experimental, random walking-motion excitations; it is shown that they outperform their linear and conventional bistable counterparts in a wide range of harmonic excitation and random vibration. Furthermore, we propose to harvest energy by exploiting surface instability or in general instability in layered composites which is, in part, motivated by the BLSH strategy. Instabilities in soft matter and composite structures e.g. wrinkling allow large local strains to take place throughout the entire structure and at regular patterns. Unlike conventional harvesting techniques, this allows to harvest energy from the entire volume of the structure e.g. by attaching piezoelectric patches at large-strain locations throughout the structure. We show that this significantly improves the power to volume ratios of the harvesting devices. In addition, these structural instabilities are non-resonant that consequently enhances robustness of such harvesters with respect to excitation characteristics. The high efficacy of energy harvesting via structural instabilities, in part, is attributed to its ability to approximately follow the BLSH logic. Additionally, we put forth the idea of extending this idea to control the instability; and hence, extend the application of the aforementioned idea from energy harvesting to a whole new level of tunable material/structures with a myriad of applications from electromechanical sensors and amplifiers to fast-motion actuators in soft robotics. And last but not least, to more specifically address the robustness issues of passive harvesters, we propose a new modeling philosophy for optimization under uncertainty; optimization for the worst-case scenario (minimum power) rather than for the ensemble expectation of the power. The proposed optimization philosophy is practically very useful when there is a minimum requirement on the harvested power. We formulate the problems of uncertainty propagation and optimization under uncertainty in a generic and architecture-independent fashion. Furthermore, to resolve the ubiquitous problem of coexisting attractors in nonlinear energy harvesters, we propose a novel robust and adaptive sliding mode controller for active harvesters to move the harvester to any desired attractor by a short entrainment on the desired attractor. The proposed controller is robust to disturbances and unmodeled dynamics and adaptive to the system parameters.

The vast reduction in size and power consumption of CMOS circuitry has led to a large research effort based around the vision of wireless sensor networks. The proposed networks will be comprised of thousands of small wireless nodes that operate in a multi-hop fashion, replacing long transmission distances with many low power, low cost wireless devices. The result will be the creation of an intelligent environment responding to its inhabitants and ambient conditions. Wireless devices currently being designed and built for use in such environments typically run on batteries. However, as the networks increase in number and the devices decrease in size, the replacement of depleted batteries will not be practical. The cost of replacing batteries in a few devices that make up a small network about once per year is modest. However, the cost of replacing thousands of devices in a single building annually, some of which are in areas difficult to access, is simply not practical. Another approach would be to use a battery that is large enough to last the entire lifetime of the wireless sensor device. However, a battery large enough to last the lifetime of the device would dominate the overall system size and cost, and thus is not very attractive. Alternative methods of powering the devices that will make up the wireless networks are desperately needed.

This book presents basic and advanced concepts for energy harvesting and energy efficiency, as well as related technologies, methods, and their applications. The book provides up-to-date knowledge and discusses the state-of-the-art equipment and methods used for energy harvesting and energy efficiency, combining theory and practical applications. Containing over 200 illustrations and problems and solutions, the book begins with overview chapters on the status quo in this field. Subsequent chapters introduce readers to advanced concepts and methods. In turn, the final part of the book is dedicated to technical strategies, efficient methods and applications in the field of energy efficiency, which also makes it of interest to technicians in industry. The book tackles problems commonly encountered using basic methods of energy harvesting and energy efficiency, and proposes advanced methods to resolve these issues. All the methods proposed have been validated through simulation and experimental results. These “hot topics” will continue to be of interest to scientists and engineers in future decades and will provide challenges to researchers around the globe as issues of climate change and changing energy policies become more pressing. Here, readers will find all the basic and advanced concepts they need. As such, it offers a valuable, comprehensive guide for all students and practicing engineers who wishing to learn about and work in these fields.

This book introduces an innovative and high-efficiency technology for mechanical energy harvesting. The book covers the history and development of triboelectric nanogenerators, basic structures, working principles, performance characterization, and potential applications. It is divided into three parts: Part A illustrates the fundamental working modes of triboelectric nanogenerators with their prototype structures and theoretical analysis; Part B and Part C introduce two categories of applications, namely self-powered systems and self-powered active sensors. The book will be an ideal guide to scientists and engineers beginning to study triboelectric nanogenerators or wishing to deepen their knowledge of the field. Readers will be able to place the technical details about this technology in context, and acquire the necessary skills to reproduce the experimental setups for fabrication and measurement.

The essential introduction to the principles and applications of feedback systems—now fully revised and expanded This textbook covers the mathematics needed to model, analyze, and design feedback systems. Now more user-friendly than ever, this revised and expanded edition of Feedback Systems is a one-volume resource for students and researchers in mathematics and engineering. It has applications across a range of disciplines that utilize feedback in physical, biological, information, and economic systems. Karl Åström and Richard Murray use techniques from physics, computer science, and operations research to introduce control-oriented modeling. They begin with state space tools for analysis and design, including stability of solutions, Lyapunov functions, reachability, state feedback observability, and estimators. The matrix exponential plays a central role in the analysis of linear control systems, allowing a concise development of many of the key concepts for this class of models. Åström and Murray then develop and explain tools in the frequency domain, including transfer functions, Nyquist analysis, PID control, frequency domain design, and robustness. Features a new chapter on design principles and tools, illustrating the types of problems that can be solved using feedback Includes a new chapter on fundamental limits and new material on the Routh-Hurwitz criterion and root locus plots Provides exercises at the end of every chapter Comes with an electronic solutions manual An ideal textbook for undergraduate and graduate students Indispensable for researchers seeking a self-contained resource on control theory

The Duffing Equation: Nonlinear Oscillators and their Behaviour brings together the results of a wealth of disseminated research literature on the Duffing equation, a key engineering model with a vast number of applications in science and engineering, summarizing the findings of this research. Each chapter is written by an expert contributor in the field of nonlinear dynamics and addresses a different form of the equation, relating it to various oscillatory problems and clearly linking the problem with the mathematics that describe it. The editors and the contributors explain the mathematical techniques required to study nonlinear dynamics, helping the reader with little mathematical background to understand the text. The Duffing Equation provides a reference text for postgraduate and students and researchers of mechanical engineering and vibration / nonlinear dynamics as well as a useful tool for practising mechanical engineers. Includes a chapter devoted to historical background on Georg Duffing and the equation that was named after him. Includes a chapter solely devoted to practical examples of systems whose dynamic behaviour is described by the Duffing equation. Contains a comprehensive treatment of the various forms of the Duffing equation. Uses experimental, analytical and numerical methods as well as concepts of nonlinear dynamics to treat the physical systems in a unified way.

The electromechanical coupling effect introduced by piezoelectric vibration energy harvesting (PVEH) presents serious modeling challenges. This book provides close-form accurate mathematical modeling and experimental techniques to design and validate dual function PVEH vibration absorbing devices as a solution to mitigate vibration and maximize operational efficiency. It includes in-depth experimental validation of a PVEH beam model based on the analytical modal analysis method (AMAM), precisely identifying electrical loads that harvest maximum power and induce maximum electrical damping. The author's detailed analysis will be useful for researchers working in the rapidly emerging field of vibration based energy harvesting, as well as for students investigating electromechanical devices, piezoelectric sensors and actuators, and vibration control engineering.