Now showing 1 - 5 of 5
  • Publication
    Bifurcation Scenarios in Electrostatic Vibration Energy Harvesters
    In this paper, we present numerical bifurcation analysis of an electrostatic vibration energy harvester operating in constant-charge mode and using the in-plane gap closing transducer. We show how the system can be represented as a nonlinear oscillator and analysed using methods of nonlinear dynamics. We verify previous analytical theories and explain the behaviour of these energy harvesters, particularly in the regime between the first period doubling bifurcation and chaos.
      305
  • Publication
    Tools for analytical and numerical analysis of electrostatic vibration energy harvesters: application to a continuous mode conditioning circuit
    This paper reports the application of different analytical tools to a basic continuous conditioning (CC) circuit for electrostatic vibration energy harvesters (e-VEHs). We address the fundamental issues of this conditioning circuit and give design advice that enhances the performance of e-VEHs employing this circuit. This circuit is widely used for harvesters with or without an electret layer. Despite its wide use, its fundamental problems have been weakly addressed even for simple configurations of e-VEHs since it is impossible to solve the corresponding equations in closed form. As a consequence, appropriate semi-analytical methods that provide an insight into the physics of the system are required.
      306Scopus© Citations 6
  • Publication
    Capacitive Energy Conversion with Circuits Implementing a Rectangular Charge-Voltage Cycle Part 1: Analysis of the Electrical Domain
    Capacitive kinetic energy harvesters (KEH) employ conditioning circuits which achieve a dynamic biasing of the transducer's variable capacitor. This paper, composed of two articles Part 1 and Part 2, proposes a unified theory describing electrical and electromechanical properties of an important and wide class of conditioning circuits: those implementing a rectangular charge-voltage cycle. The article Part 1 introduces a basic configuration of conditioning circuit implementing an ideal rectangular QV cycle, and discusses its known practical implementations: the Roundy charge pump with different flyback mechanisms, and configurations based on the Bennet's doubler. In Part 1, the analysis is done in the electrical domain, without accounting for electromechanical coupling, while in Part 2, the full electromechanical system is analyzed. An optimization approach common to all configurations is proposed. A comparison is made between different topologies and operation modes, based on the maximal energy converted in one cycle under similar electrical and mechanical conditions. The last section discusses practical implementation of circuits with smart and adaptive behavior, and presents experimental results obtained with state-of-the art MEMS capacitive KEH devices.
      506Scopus© Citations 40
  • Publication
    Capacitive Energy Conversion with Circuits Implementing a Rectangular Charge-Voltage Cycle Part 2: Electromechanical and Nonlinear Analysis
    In this paper, we explore and describe the electromechanical coupling which results in eKEH conditioning circuits implementing a rectangular QV cycle, including but not limited to the charge pump and Bennet’s doubler circuits. We present numerical and semi analytical analyses describing the nonlinear relationship between the oscillating mass and the conditioning circuit. We believe this is a poorly understood facet of the device and, as we will portray, effects the potential harvested energy. An approach to determine the frequency shift due to the electromechanical coupling is presented and compared with novel experimental results. We provide some examples of bifurcation behaviour and show that the only source of nonlinearity is in the coupling between the electrical and mechanical domains. This work continues from the electrical analysis presented in Part 1, providing a full insight into the complex behaviour of the electromechanical coupling.
      495Scopus© Citations 20
  • Publication
    Complete electromechanical analysis of electrostatic kinetic energy harvesters biased with a continuous conditioning circuit
    This paper presents a comprehensive electromechanical study of an electrostatic kinetic energy harvester (eKEH) biased with a continuous voltage. This simple circuit refers to any capacitive transducer with an in-built voltage source, such as an electret, or DC biased transducer connected directly to a resistive load. It is commonly used for the characterisation of experimental transducers. However there is a void of any unified discussion focusing on the circuits influence on the transducer, due to electromechanical coupling in the transducer. The electromechanical coupling causes numerous nonlinear effects, any of which can result in inconsistent results and disjointed conclusions of experimental devices. This article seeks to present analytic tools which can be employed for systems of this type and discusses some of the results obtained from these techniques. Along with analysis and characterisation of the circuit dynamics, the results are compared with an experimental device and presented in terms of design of the system and conclusions drawn relating to the optimum operation point.
      325Scopus© Citations 10