Broadband energy harvesting from parametric vibrations of a class of nonlinear Mathieu systems

The nonlinear dynamics of Mathieu equation with the inclusion of a cubic stiffness component is considered for broadband vibration energy harvesting. Results of numerical integration are compared with the corresponding solution of a regular Duffing oscillator, which is widely used to model nonlinear energy harvesting. Use of Duffing oscillators has shown direct correspondence between the effective frequency range of the associated hysteretic phenomenon and the value of the nonlinearity coefficient. Due to that, a broadband energy harvester requires strong nonlinearity, especially for high frequencies of interest. This letter demonstrates that the effectiveness of parametrically-excited systems is not constrained by the same requirement. Based on this, it is suggested that parametrically-excited systems can be a robust means of broadband vibration harvesting

On the dynamics of a nonlinear energy harvester with multiple resonant zones

The dynamics of a nonlinear vibration energy harvester for rotating systems is investigated analytically through harmonic balance, as well as by numerical analysis. The electromagnetic harvester is attached to a spinning shaft at constant speed. Magnetic levitation is used as the system nonlinear restoring force for broadening the resonant range of the oscillator. The system is modelled as a Duffing oscillator with linear frequency variation under static, as well as harmonic excitation. Behaviour charts and backbone curves are extracted for the fundamental harmonic response and validated against frequency response curves for selected cases, using direct numerical integration. It is found that variation in stiffness, together with asymmetric forcing, gives rise to a novel structure of multiple resonant zones, incorporating mono-stable and bi-stable dynamics. Contrary to previously considered bi-stable energy harvesters, cross-well oscillations are realized through a transition from single-well potential energy to double-well with forward frequency sweep. Furthermore, in-well_oscillations present a hardening behaviour, unlike the well-known softening in-well response of bi-stable Duffing oscillators. The analysis shows that the proposed system has multiple resonant responses to a frequency sweep, influenced by consecutive interacting backbone curves similar to a multi-modal system. This combined effect of the transition to bi-stable dynamics and the hardening in-well oscillations induces resonant response of the harvester over multiple distinct frequency ranges. Thus, the system exhibits a broadened frequency response, enhancing its energy harvesting potential

Design, analysis, and feedback control of a nonlinear micro-piezoelectric–electrostatic energy harvester

A nonlinear micro-piezoelectric–electrostatic energy harvester is designed and studied using mathematical and computational methods. The system consists of a cantilever beam substrate, a bimorph piezoelectric transducer, a pair of tuning parallel-plate capacitors, and a tip–mass. The governing nonlinear mathematical model of the electro-mechanical system including nonlinear material and quadratic air-damping is derived for the series connection of the piezoelectric layers. The static and modal frequency curves are computed to optimize the operating point, and a parametric study is performed using numerical methods. A bias DC voltage is used to adapt the system to resonate with respect to the frequency of external vibration. Furthermore, to improve the bandwidth and performance of the harvester (and achieve a high level of harvested power without sacrificing the bandwidth), a nonlinear feedback loop is integrated into the design

Campus Inc.

Grounded on the design premise of the monastery type, by which circulatory elements aggregate different programmatic spaces into one autonomous collegial complex, the corporate campus is proposed as an urban generator for the residential suburbia. We live in suburbs that were designed to escape the predicament of cities and go to work in the comfortable confines of corporate space. Today, as the public man gradually falls, we as urban planners and architects are restricted to only reproducing that; either suburbia or corporate space, with no tangential moments between the two. Silicon Valley, although known for its corporate activity, is a grand example of the parallel existence of both these types of space. The mundane suburban condition is a well known one; private plots belonging to private people, on top of which repetitive prefabricated homes keep them inside. Corporate space is by default private, as it serves only the numbers of the corporation’s family. Corporate campuses have been celebrating their Edenic hortus conclusus type since their moment of their conception in the 50s; However today, inasmuch as isolation is still considered a strong stimulus for the mind of the employee, equally or more so does the communication with and input from different people. The original idea of the campus advocated for this ambivalence. Found in medieval colleges and monastic complexes, the campus utilized a different set of design tools, such as that of the cloister, the corridor and the courtyard, to clearly define the boundaries of each space, but as a part of a whole. The project rethinks the well circulated corporate model, so as to reestablish the present relationship between traditionally introvert privately owned space and the public. In the same way a city acts and reacts, a figure-ground reading of the proposal reveals the clash of an ordinary, closed suburban system of repetition with the complex geometry and receptive character of the campus. The proposed model benefits all; the company merits from leasing its space to smaller local businesses of diverse character that populate its center, and the surrounding suburbia enjoy the amenities of a city. For this to happen successfully, spaces are generic enough so as to target a wider range of possible renters, but specific enough to indicate an urban program. The position and concurrency of adjacent programs creates different topical dynamics that vary with time and are expressed and generated via the communal spaces. The urban is the only landscape complex, diverse and rich enough to spawn communication between dissimilar types of people. Ultimately, the project aims to a certain kind of eugenicism: designing the ethics of the corporate world towards its proximate environment, and by extension, the morals of the contemporary worker.Architecture and The Built EnvironmentArchitectureThe Berlage Centre for Advanced Studies in Architecture and Urban Desig

Современные образовательные технологии в высшей школе : учебно-методическое пособие

Recent developments in propulsion systems to improve energy efficiency and reduce hazardous emissions often lead to severe torsional oscillations and aggravated noise. Vibration absorbers are typically employed to palliate the untoward effects of powertrain oscillations, with nonetheless an adverse impact on cost and constrained efficacy over a limited frequency range. Recently, the authors proposed the use of nonlinear vibration absorbers to achieve more broadband drivetrain vibration attenuation with low complexity and cost. These lightweight attachments follow the concept of targeted energy transfer, whereby vibration energy is taken off from a primary system without tuning requirements. In this paper, the design and experimental investigation of a prototype absorber is presented. The absorber is installed on a drivetrain experimental rig driven by an electric motor through a universal joint connection placed at an angle, thus inducing second order torsional oscillations. Vibration time histories with and without the absorber acting are recorded and compared. Frequency-energy plots are superimposed to the system nonlinear normal modes to verify the previously developed design methodology, whereas the achieved vibration reduction is quantified by comparing the acceleration amplitudes of the primary system and monitoring the distribution of energy damped in the primary system and the absorber. The absorber prototype was found to lead to significant vibration reduction away from resonance and near resonance with the additional feature of activation over a relatively broad frequency range.</div