Now showing 1 - 5 of 5
  • Publication
    Investigation and Optimisation of Kinetic Energy Harvesters with Nonlinear Electromechanical Coupling Mechanisms
    (University College Dublin. School of Electrical and Electronic Engineering, 2022) ;
    This thesis applies various nonlinear analysis techniques to reconstruct the qualitative and quantitative characteristics of Kinetic Energy Harvesters (KEHs) and proposes methods to optimize them. Having the optimization of electromagnetic and electrostatic harvesters achieved, a concept of the near-limit KEH is introduced specifically on realistic patterns of motion. Chapter 2 gives a general review of the KEH field with regard to types of energy harvesting devices, the amount of power they can generate and their compatibility with different sensors. Chapter 3 contains a detailed description of modeling approaches for KEHs with various transduction mechanisms. It provides comprehensive information on how to model various interaction forces acting on the proof-mass of an KEH, particularly, dissipative forces and piece-wise stopper interactions. Finally, various techniques to model the dynamics of the system, such as numerical solutions of the motion equations, harmonic balance method and multiple scales method are shown in this chapter. Chapter 4 shows a successful application of the methods described in Chap. 3 to meso-scale KEHs with the electromagnetic transduction mechanism. A fast and reliable method of equivalent coils is used to solve for the magnetic field developed in such a system. Chapter 5 is focused on the problem of frequency up-conversion in KEHs with electrostatic transduction. Employing the technique shown in Chap. 3 on experimental resonance curves, we reproduce the waveforms of the mechanical motion of the proof-mass. By analyzing them in terms of higher harmonic, we discover the reason behind high-power generation at low frequencies in systems with up-conversion. The Concept of kinetic energy harvesting that is forced to move following the optimal trajectory for a given excitation is shown in Chapter 6. The main feature of the near-limit control of KEH is prediction of the next maximum-minimum pair in the external acceleration, and the corresponding control. The acceleration patterns of various human motion waveforms are measured and used as the possible external excitation to test Near-Limit Kinetic Energy Harvester (NLKEH). In addition, techniques to predict the next extremum in generic acceleration pattern are investigated. Finally, Chapter 7 summarizes the thesis and presents main conclusions.
  • Publication
    Method of Equivalent Currents for the Calculation of Magnetic Fields in Inductors and Magnets with Application to Electronics
    Magnetic components are essential in many applications of electronics. Despite a very clear understanding of magnetic phenomena developed from first principles of Electromagnetics and Maxwell’s equations, modelling of the magnetic field, flux and force in a particular system can be a very challenging problem. Often, direct calculations are avoided, and a phenomenological model describing magnetic interactions is used instead. There are a number of methods which can be used for the modelling of the magnetic field due to magnetic materials and inductors and which can provide detailed and predictive information on such systems. Multi-physics scientific packages utilising finite-element methods are among the most common tools as they can solve a wide range of different problems and employ universal numerical algorithms. As a trade-off, they are very resource-intensive and have a low speed of execution. As an alternative, one can develop simulation techniques utilising magnetic dipoles or equivalent currents. These methods are less resource-intensive and very fast; however, they also have their limitations. This paper presents a method of equivalent currents developed for the fast calculation of the magnetic field and flux. We show the application of the method to inductors and permanent magnets that have a particular importance in power electronics and electromagnetic kinetic energy harvesting.
  • Publication
    Modelling of Electromagnetic Coupling in Micro-Scale Electromagnetic Energy Harvesters
    Kinetic energy harvesters as systems which convert kinetic energy of the oscillations to electric power has different transduction mechanisms. One of the most common transduction mechanisms in such systems is electromagnetic generation, when a voltage is generated according to the Faraday law. Despite the clear physical nature of the electromechanical coupling, the development of the close lumped model for electromotive force and electromagnetic force is challenging problem. The algorithm for estimation of these values and criteria of self-consistency for the model is presented in this paper. In addition, suggested algorithm is applied to the real microscopic electromagnetic energy harvester and predicted signal was compared to the experimental data.
  • Publication
    Modelling and Verification of Nonlinear Electromechanical Coupling in Micro-Scale Kinetic Electromagnetic Energy Harvesters
    Electromechanical coupling in kinetic energy harvesters is the key aspect of these devices that ensures an effective energy conversion process. When modelling and designing such devices, it is necessary to incorporate electromechanical coupling correctly since it will determine the amount of energy that will be converted during its operation. As the engineering community prefers compact (lumped) models of such devices, the conventional choice of the lumped model for the electromagnetic type of electromechanical coupling is linear damping, proportional to the velocity of the mechanical resonator in a harvester, leading to the idea of maximizing the velocity in order to improve the energy conversion process. In this paper, we show that electromechanical coupling in electromagnetic kinetic energy harvesters is inherently nonlinear and requires a number of aspects to be taken into account if one wants to optimize a device. We show that the proposed model, which is based on first principles of electromagnetics, can be reduced to a nonlinear lumped model that is particularly convenient for analysis and design. The modelling approach and the resulting lumped model are verified using two MEMS electromagnetic harvesters operating over a range of frequencies from 300 to 500 Hz (Harvester A) and from 50 to 70 Hz (Harvester B) generating from mV (Harvester A) to few volts (Harvester B) of RMS voltage, respectively. The proposed modelling approach is not limited to energy harvesters but can also be applied to magnetic sensors or other MEMS devices that utilise electromagnetic transduction.
      626Scopus© Citations 8
  • Publication
    Semi-Analytical Method for the Extraction of the System Parameters in Application to Kinetic Energy Harvesters
    In this paper, we propose a technique to extract system parameters of nonlinear MEMS devices using a combination of model reduction and nonlinear optimization. The model is tested on a MEMS energy harvesting device employing magnetic actuation and piezoelectric energy conversion.