This paper reports on a new approach for the analysis and design of vibration-to-electricity converters vibration energy harvesters (VEHs) operating in the mode of strong electromechanical coupling. ...The underlying concept is that the mechanical impedance is defined for a nonlinear electromechanical transducer on the basis of an equivalence between electrical and mechanical systems. This paper demonstrates how the mechanical impedance of the transducer depends not only on the geometry and the nature of the electromechanical transducer itself but also on the topology and on the operation mode of the conditioning circuit. The analysis is developed for resonant harvesters and is based on the first-harmonic method. It is applied to three electrostatic harvesters using an identical conditioning circuit but employing transducers with different geometries. For each of the three configurations, the mechanical impedance of the transducer is calculated and then used to determine the optimal electrical operation mode of the conditioning circuit, allowing a desired amplitude of the mobile-mass vibration to be obtained. This paper highlights how the parameters of the conditioning circuit and of the transducer impact the transducer's mechanical impedance, directly affecting the impedance matching between the energy source (resonator) and the transducer. This technique permits the design of highly efficient VEHs whatever the means of transduction.
In this paper, we describe an architecture of a distributed ADPLL (All Digital Phase Lock Loop) network based on bang-bang phase detectors that are interconnected asymmetrically. It allows an ...automatic selection between two operating modes (uni- and bidirectional) to avoid mode-locking phenomenon, to accelerate the network convergence and to improve the robustness to possible network failures in comparison to simple unidirectional mode.
This paper deals with the stability of so-called "self-sampled" digital phase-locked-loops (PLLs). These systems are meant to be used as the nodes of autonomous clock distribution networks, where ...clock signals are locally generated in each node and each node is synchronized with its neighbours. Despite the absence of an absolute reference clock, it is possible to use the local irregular clock to trigger the operations of the digital loop filter. In this paper, we show that, in this mode of operation, PLLs can be modeled as autonomous piecewise-linear systems. We investigate what filter coefficients to choose in order to ensure stability and, hence synchronization. Two methods are explored, the first based on transient simulations, the second on linear matrix inequalities. It is shown that the second method yields much more conservative results than the first but that it cannot apply to all design options of self-sampled PLLs.
This paper analyses the stability of the synchronized state in Cartesian networks of identical all-digital phase-locked loops (ADPLLs) for clock distribution applications. Such networks consist in ...Cartesian grids of digitally-controlled oscillator nodes, where each node communicates only with its nearest neighbors. Under certain conditions, we show that the whole network may synchronize both in phase and frequency. A key aspect of this study lies in the fact that, in the absence of an absolute reference clock, the loop-filter in each ADPLL is operated on the irregular rising edges of the local oscillator and consequently, does not use the same operands depending on whether the local clock is leading or lagging. Under simple assumptions, these networks of so-called "self-sampled" all-digital phase-locked-loops (SS-ADPLLs) can be described as piecewise-linear systems, the stability of which is notoriously difficult to establish. The main contribution of this paper is a simple design rule that must be met by the coefficients of each loop-filter in order to achieve synchronization in a Cartesian network of arbitrary size. Transient simulations indicate that this necessary synchronization condition may also be sufficient for a specific (but important) class of SS-ADPLLs. A synthesis of the different approaches that have been conducted in the study of the synchronization of SS-ADPLLs is also done.
This paper deals with a fully batch-processed MEMS electrostatic Vibration Energy Harvster (e-VEH) having a half-power frequency bandwidth of more than 30 % thanks to the combination of electrostatic ...and mechanical non-linearities. The electromechanical transducer is made of bulk-silicon gap-closing interdigited combs with a trapezoidal cross section. Up to 2.2 μW have been harvested at atmospheric pressure for an external acceleration of 1 G at 150 Hz.
This paper presents a simple analytical method to optimize the efficiency of an electrostatic out-of-plane gap-closing (OPGC) Vibration Energy Harvesters (VEH). For the first time the electrical and ...mechanical behaviours of the transducer are addressed simultaneously, while a voltage limitation on the transducer’s terminals is set to prevent any damage in the conditioning electronic. The presented work allows to the designer to determine the best strategy depending on whereas the system is passive or able to be self-adapted to the external vibrations parameters. The optimization is performed for a 1 cm² device made of bulk silicon to be fabricated using a batch MEMS process. Up to 15 μW can be obtained at 200 Hz if the output voltage is limited to 60 V. The calculations are validated by VHDL-AMS/ELDO simulations.
A design method for high-order electro-mechanical filters allowing the synthesis of architectures of electro-mechanical filters from equivalent electrical prototypes is presented. Conditions for ...existence of the equivalent mechanical system for a given electrical network are derived. This method is applied to the problem of the design of band-pass electro-mechanical filters with transmission zeros in the stopband. Electro-statical coupling of micro-mechanical resonators that avoids the use of a mechanical coupling spring is introduced. The application to the simulation and design of a bandpass filter with finite transmission zeros implemented in a thick-layer epi-poly silicon micro-machining technology is shown.
We report a 1-cm2 ultra-wideband MEMS electrostatic vibration energy harvester (e-VEH) that combines a frequency-up conversion system with a vertical electret layer obtained by corona discharge. At ...2.0 grms, the device can harvest more than 1 μW from 59 to 148 Hz, and more than 0.5 μW from 14 to 152 Hz. Thanks to this new device, we demonstrate the self-starting power supply of an energy autonomous temperature sensor node with a data transmission beyond a distance of 10 m at 868 MHz.
This paper reports a novel vibration energy harvester (VEH) design consisting of a double-mass contactless frequency-up converter with buckled clamped-clamped beams. The vibration to electricity ...conversion is performed through a MEMS silicon micro electrostatic vibration energy harvester (e-VEH) based on in-plane gap-closing interdigitated combs. Despite the fact that the converter itself is designed to resonate at 162 Hz, the use of the bistable stage as mechanical exciter allows a gain factor of hundred when converting low-frequency vibrations (20-40 Hz) into electrical energy.
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.
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