Andrii Dudka

A batch-fabricated and electret-free silicon electrostatic vibration energy harvester

This paper presents a novel silicon-based and batch-processed MEMS electrostatic transducer for harvesting and converting the energy of vibrations into electrical energy without using an electret layer. Effective conversion from the mechanical-to-electric domains of 61 nW on a 60 MΩ resistive load, under a vibration level of 0.25 g at 250 Hz, has been demonstrated. Rigorous analysis of the efficiency of the harvester is presented, covering issues related with mechanical and electrical operation. Various schemes for the conditioning electronics are discussed and the harvested power measurements using a dc/dc converter are explained in detail. The paper concludes with a comparison with previous electrostatic transducers based on a new simple factor of merit.

Design of Controller IC for Asynchronous Conditioning Circuit of an Electrostatic Vibration Energy Harvester

This paper presents a transistor-level design of a power management electrical circuit for asynchronous electrostatic energy harvester. The conditioning circuit of the harvester is based on a charge pump and a fly back circuits. The designed power management block implements the concept of adaptive behaviour of energy harvester, allowing it to operate in an optimal mode in environment where the magnitude of the vibrations may change in time. For the first time, such a system is designed to operate at high voltage (up to 30 V). However, this paper does not concern the design of electromechanical transducer. The IC design has been carried out in 0.35um high-voltage CMOS technology, and has been validated by a coupled VHDL-AMS/SPICE simulation. The control system average power consumption is less then 0.9uW, whereas the average harvested power is approximately 1.1uW for 14V operation voltage.

Comprehensive dynamic and stability analysis of electrostatic Vibration Energy Harvester (E-VEH)

This paper reports on an investigation of dynamic behavior of an electrostatic Vibration Energy Harvester (e-VEH) which uses gap-closing capacitive transducers and operates in a constant-charge mode. This work provides a deep insight into stability issues of a e-VEH investigating four dynamic modes, among which only one corresponds to a regular, stable and desirable operation mode needed for the energy conversion. The three other modes represent instable behavior. Each one corresponds to a particular range of external acceleration, and in none of these modes the e-VEH behaves similarly to an ideal constant-voltage biased transducer associated with a resonator. This paper describes a modeling experiment allowing a demonstration of the four operation modes, and proposes theoretical considerations for their quantitative description.

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 from eKEH conditioning circuits implementing a rectangular QV cycle, including but not limited to the charge pump and Bennets 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, affects 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 behavior 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 behavior of the electromechanical coupling.

VHDL-AMS modeling of adaptive electrostatic harvester of vibration energy with dual-output DC-DC converter

This paper presents a functional design and modeling of smart conditioning circuit of a vibrational energy harvester based on electrostatic transducer. Two original features are added to the basic configuration previously published (whose model we presented on BMAS2007 conference). Firstly, we developed an auto-calibration block which allows the new harvester to adapt dynamically to the varying environment parameters (e.g., amplitude of external vibrations). Secondly, we propose an original schematic configuration based on dual output DC-DC converter, which implements a smart power interface with the load, allowing the harvester to manage a possibly variable load and adapt to different situations (e.g. unsufficient generated power level, load too large, etc.). The scheme of the power interface re-uses the coil existing in the basic harvester configuration. The new harvester architecture contains “software” blocks which can be programmed to implement different power-management and auto-calibration strategies. We describe one possible algorithm of the whole architecture operation, and present the corresponding modeling results. The system is implemented as a mixed VHDL-AMS/ELDO model.

Smart integrated conditioning electronics for electrostatic vibration energy harvesters

This paper presents an overview of problems related to electronic conditioning of capacitive transducers used for the kinetic energy conversion. It proposes a methodology for the system-level and circuit-level design of conditioning electronics for electrostatic energy harvesters so to comply with the requirements of realistic applications: long-lasting operation, self-calibration, low consumed power and the implementation using the integrated circuit CMOS technology. An original architecture of a self-calibrating conditioning circuit is proposed. The paper gives a review of main design challenges related to this architecture, explains the motivation of the technology choice, provides insight into critical blocks and presents intermediate results of design.

MEMS DC/DC converter for 1D and 2D vibration-to-electricity power conversion

This paper presents a working silicon-based MEMS electrostatic transducer for harvesting and converting the energy of vibrations into electrical energy. The transducer is fabricated in a batch silicon-on-glass process. Two designs, for 1D and 2D vibrations, are addressed. The 1D harvester demonstrates between 60 and 100 nW of mechanical-to-electrical power conversion at 250 Hz when implemented in a classical DC/DC converter circuit. We also propose a new simple approach for the calculation of the maximum power that can be generated from a spring-mass system excited with a sinusoidal force, based on an electrical impedance network analogy. This paper ends with a comparison between several working electrostatic harvesters based on a novel figure of merit.

Capacitive kinetic energy harvesting: System-level engineering challenges

This review paper presents a short overview of the energy harvesting technologies at microscale, and focus on challenges related to vibration energy harveters (VEHs) which use electrostatic (capacitive) transducers. These devices are the best candidates for microscale integration, since the electrostatic transducers are natively implemented in silicon microtechnologies (MEMS). The main challenges associated with electrostatic VEHs are related to the passive nature of the capacitive transducer. The latter can be seen as a variable capacitor, needed to be dynamically biased/pre-charged in order to convert vibrations into electricity. For this, a complex management of the charging/discharging electrical flow on the transducer is required: this is achieved with a conditioning circuit, studied in numerous works. Electrostatic kinetic energy harvester a multidomain complex system, containing several blocks, whose optimal design still a subject of advanced research. This paper reviews the challenges related to design of capacitive vibration energy harvesters at the system level, explains fundamental limitation of the capacitive vibration energy harvesters at micro scale, and overview the existing system-level solutions of capacitive VEHs.

The limiting effect of electromechanical coupling in self-biased electrostatic Vibration Energy Harvester

This paper reports on the drastic impact of the electromechanical coupling on the operating mode of a MEMS electrostatic Vibration Energy Harvester (e-VEH). A similar behavioral pattern was observed for two different conditioning circuits, which biased the e-VEH: one based on a classical charge pump circuit and one based on the Bennet doubler. The result of this study mitigates the commonplace opinion about the need of maximization of the bias voltage of electromechanical transducer for optimization of the converted power. When the circuits operated in self-biasing mode, in which the reservoir capacitor voltage increases exponentially for weak voltages, a slow down and saturation were consequently observed at average and high voltages. It is due to several phenomena, among which the nonlinear dynamics of the system, increase of the electromechanical damping with bias voltage, and basically by the fundamental limitation of the power that can be extracted from external vibrations.

Complexity in heterogeneous systems on chips: Dsign and analysis challenges

In this review paper, we define and discuss the concept of complexity for heterogeneous systems. Due to the current progress in fabrication technology, modern micro-scale integrated systems may have a large number of interacting elements. Each of those elements not only displays its own dynamical properties, but also, in the most general case, can be nonlinear or can belong to different physical domains. We consider two different examples of systems that are complex in the terms we use in this paper. The first example is a network of oscillators and is heterogeneous since it is a mixed-signal system. The second example is an electrostatic vibration energy harvester, a micro scale system combining elements from the mechanical and electrical domains. In both cases we discuss the challenges that arise at the stage of the system design.