Abstracts of Journal Articles - Accepted for Publication

High-energy Orbit Harvesting with Torsionally Coupled Mistuned Pendulums

PV Malaji (V P Dr. P G Halakatti College of Engineering & Technology, India), MI Friswell (Swansea University), S Adhikari (University of Glasgow) & G Litak (Lublin University of Technology, Poland)

Journal of Vibration Engineering Technologies

This article demonstrates the possibility of energy harvesting by mistuned pendulums with torsional coupling. Two pendulums of different lengths with coils and magnets at the pivots are used as electromagnetic harvesters. The ambient energy source to the system is considered in the form of harmonic base excitations. Torsional coupling is achieved by connecting the pendulums with a torsional spring. The non-linearity of the underlying dynamics arises due to mechanical coupling and forcing amplitude. Numerical results are presented to analyze the performance of the pendulum energy harvester under different torsional coupling values. Three different zones were identified based on coupling value, power output and frequency bandwidth. Based on the requirement of power magnitude and bandwidth, one can select a suitable zone. The dynamic behaviour of the pendulums in each zone is shown by bifurcation and phase diagrams. The results indicate periodic and quasi-periodic oscillations for different values of torsional coupling. The effect of load resistance on the energy harvesting and dynamics of the pendulums is presented. The harmonic balance method results are presented to verify the existence of high energy orbit solutions in respective zones. A good agreement between numerical and harmonic balance results is observed. The optimal choice of torsional coupling, load resistance along with optimal initial conditions enables the harvesting of more power over a broader frequency band. Cross recurrence plots are also presented to show synchronisation state of pendulums.

Integrating PZT Layer with Tuned Mass Damper for Simultaneous Vibration Suppression and Energy Harvesting Considering Exciter Dynamics: An Analytical and Experimental Study

M Rezaei, R Talebitooti (Iran University of Science and Technology, Iran), W-H Liao (The Chinese University of Hong Kong, Hong Kong, China) & MI Friswell (Swansea University)

Journal of Sound and Vibration

This paper analytically and experimentally investigates the potential of a tuned mass damper (TMD) with an integrated piezoelectric layer for simultaneous energy harvesting and vibration suppression. The system investigated is composed of a main beam that is excited by a shaker. A TMD comprising a unimorph piezoelectric beam is attached to the main beam. The shaker force drops at the system resonance frequencies means that a constant force sine sweep is difficult in practice, and does not allow model validation and empirical assessment of the TMD. Also, the force drop off phenomenon and an accurate validated shaker model are vital for the modelling, analysis and validation of nonlinear dynamic systems. This paper validates and analyses a linear model, in preparation for future studies of a nonlinear vibration absorber and energy harvester. Therefore, the force drop off phenomenon is examined comprehensively, and a constant shaker input voltage sweep is proposed instead of a constant force sweep. The continuous electromechanical equations governing the coupled system of the main beam-TMD-shaker are developed. The proposed model is then utilized to examine the shaker force drop off, TMD efficiency, and shaker electrical characteristics. The results show that the constant voltage sweep works well to investigate the performance of the TMD and capture the shaker force drop off phenomenon. The TMD suppresses the host structure vibration and harvests energy efficiently, and is demonstrated by extensive experimental investigations. The model is validated by the experiments, including the force drop off. The system parameters have significant effects on the dynamical response of the coupled system and the energy harvested; the effects on the harvested power, reduced vibration, applied force, and force drop off frequencies are demonstrated. Overall, the TMD is shown to be efficient and applicable in reducing vibration and harvesting energy.

A Feasibility Study on Piezoelectric Energy Harvesting from the Operational Vibration of a Highway Bridge

M Infantes (Universidad de Granada, Spain), R Castro-Triguero, RR Sola-Guirado, D Bullejos (Universidad de Cordoba, Spain) & MI Friswell (Swansea University)

Advances in Structural Engineering

Vibration-based energy harvesting represents a clean power technology that can be of interest for application in civil engineering structures. This study focuses on energy harvesting using cantilever piezoelectric devices excited by operational and ambient bridge vibration. The optimal design and analysis of energy harvesters is usually performed using the mean and standard deviation of a response quantity of interest (i.e. voltage) under broadband Gaussian white noise excitation. In this paper, a novel holistic approach to the problem is proposed through the statistics of the voltage of piezoelectric energy harvesters under real measured bridge vibration base excitation. A new semi-analytic expression of the expected power is developed. The solution is based on the closed-form of the frequency response function between the harvester output voltage and the base excitation, and the experimentally measured spectral density of the latter. A study on the influence of the electromechanical coupling of the problem equations is first conducted. Then, a sensitivity analysis of the piezoelectric energy harvester parameters is performed. The critical analysis is developed through a case study of the measured long-term vibrations of a bowstring-arch highway bridge. Both operational and ambient vibration records are considered in the feasibility study. The results show the potential of the semi-analytic expression to evaluate the harvested power of piezoelectric harvesters under operational structural vibration. This is a promising approach to confidently develop future analyses on the power requirements of wireless sensor networks for SHM.

Nonlinear Modal Interactions during Rub-Impact of a Rotating Flexible Shaft

A Kartheek, K Vijayan (Indian Institute of Technology Kharagpur, India) & MI Friswell (Swansea University)

Journal of Vibration and Control

An understating on interaction between a rotating flexible member and a stationary element has wide range of industrial application. The focus of this study was to understand the modal interactions using a conceptual model. The conceptual model of the system consists of multiple disc rotor with a localised conduit. A theoretical model of the system was developed using finite element analysis. An eigenvalue analysis was carried out on the system and a Campbell diagram of the system was developed. The Campbell diagram provided information about the rotor speed wherein synchronization with the whirling modes occur. Further a reduced order non-linear contact model was developed. A numerical bifurcation analysis with rotor speed as parameter was carried out on the reduced model. Analysis was carried out using randomized initial condition for each rotation speed. During the bifurcation study certain rotation speed produced high whirling response at speeds different from the critical speed. The increase in response was associated with the internal resonance of whirling modes and rotor speed. The participating modes were identified using the Campbell diagram and full spectrum. The results from the theoretical model was validated using an experimental test rig. The identification of these internal resonance rotor speed can be useful in identifying the rotor speed exclusion zone and thereby improve the rotor life.