This book is a single-source guide to nonlinearity and nonlinear techniques in energy harvesting, with a focus on vibration energy harvesters for micro and nanoscale applications. The authors demonstrate that whereas nonlinearity was avoided as an undesirable phenomenon in early energy harvesters, now it can be used as an essential part of these systems. Readers will benefit from an overview of nonlinear techniques and applications, as well as deeper insight into methods of analysis and modeling of energy harvesters, employing different nonlinearities. The role of nonlinearity due to different aspects of an energy harvester is discussed, including nonlinearity due to mechanical-to-electrical conversion, nonlinearity due to conditioning electronic circuits, nonlinearity due to novel materials (e.g., graphene), etc. Coverage includes tutorial introductions to MEMS and NEMS technology, as well as a wide range of applications, such as nonlinear oscillators and transducers for energy harvesters and electronic conditioning circuits for effective energy processing.

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 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.

Vibrations are a part of our environment and daily life. Many of them are useful and are needed for many purposes, one of the best example being the hearing system. Nevertheless, vibrations are often undesirable and have to be suppressed or reduced, as they may be harmful to structures by generating damages or compromise the comfort of users through noise generation of mechanical wave transmission to the body. the purpose of this book is to present basic and advanced methods for efficiently controlling the vibrations and limiting their effects. Open-access publishing is an extraordinary opportunity for a wide dissemination of high quality research. This book is not an exception to this, and I am proud to introduce the works performed by experts from all over the world.

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.

Frequency Analysis of Vibration Energy Harvesting Systems aims to present unique frequency response methods for analyzing and improving vibration energy harvesting systems. Vibration energy is usually converted into heat energy, which is transferred to and wasted in the environment. If this vibration energy can be converted into useful electric energy, both the performance and energy efficiency of machines, vehicles, and structures will be improved, and new opportunities will open up for powering electronic devices. To make use of ambient vibration energy, an effective analysis and design method is established and developed in this book. The book covers a wide range of frequency response analysis methods and includes details of a variety of real-life applications. MATLAB programming is introduced in the first two chapters and used in selected methods throughout the book. Using the methods studied, readers will learn how to analyze and optimize the efficiency of vibration energy systems. This book will be ideal for postgraduate students and researchers in mechanical and energy engineering.

This book presents a selection of contributions from the 4th International Conference on Structural Nonlinear Dynamics and Diagnostics, reflecting diverse aspects of nonlinear and complex dynamics. Fifteen chapters discuss the latest findings and applications in active research areas in nonlinear mechanics and physics. These includes the dynamics of ships with liquid sloshing interaction, dynamics of drops and bubbles, nonlinear drying processes, suppression of time-delayed induced vibrations, dynamics of robotic systems, chaos detection in rolling element, dynamics of a planetary gear system with faults, vibro-impact systems, complex fractional moments for nonlinear systems, oscillations under hysteretic conditions, as well as topics in nonlinear energy harvesting and control.