On Capacity of Active Relaying in Magnetic Induction based Wireless Underground Sensor Networks

Wireless underground sensor networks (WUSNs) present a variety of new research challenges. Magnetic induction (MI) based transmission has been proposed to overcome the very harsh propagation conditions in underground communications in recent years. In this approach, induction coils are utilized as antennas in the sensor nodes. This solution achieves longer transmission ranges compared to the traditional electromagnetic (EM) waves based approach. Furthermore, a passive relaying technique has been proposed in the literature where additional resonant circuits are deployed between the nodes. However, this solution is shown to provide only a limited performance improvement under practical system design contraints. In this work, the potential of an active relay device is investigated which may improve the performance of the system by combining the benefits of the traditional wireless relaying and the MI based signal transmission.Comment: This paper has been accepted for presentation at IEEE ICC 2015. It has 6 pages, 5 figures (4 colored), and 17 reference

Wireless adiabatic power transfer

We propose a technique for efficient mid-range wireless power transfer between two coils, by adapting the process of adiabatic passage for a coherently driven two-state quantum system to the realm of wireless energy transfer. The proposed technique is shown to be robust to noise, resonant constraints, and other interferences that exist in the neighborhood of the coils.Comment: 11 pages, 6 figure

A 13.56 MHz bidirectional IPT system with wirelessly synchronised transceivers for ultra-low coupling operation

This paper presents a high-frequency inductive power transfer (HF-IPT) system with bidirectional capability employing a new wireless synchronisation method. Synchronisation is achieved by transmitting a reference ultra high frequency tone (433.92 MHz) that is stepped down to 13.56 MHz in each transceiver. This allows the operating frequency to be locked across the two sides of the system. Afterwards, a phase search is performed looking for maximum power throughput, determining the phase at the point of resonance (i.e., no reflected reactances). The experimental implementation is achieved with two back-to-back Class EF coil-drivers driven by independent synchronisation circuits. In the experimental setup a constant input voltage is set for each of the two coil-drivers by implementing a source-sink configuration, emulating a bidirectional DC-DC conversion stage at each side. Experimental results show successful transceiver synchronisation, and 4 W were transferred from one end to the other and conversely at an ultra-low coupling of 1.6%. This proves that the combination of the load-independent Class EF transceivers and the synchronisation technique introduced herein is suitable for applications that require large tolerance to misalignment and air gaps larger than one coil diameter, such as in micro e-mobility

Micro air vehicles energy transportation for a wireless power transfer system

The aim of this work is to demonstrate the feasibility use of an Micro air vehicles (MAV) in order to power wirelessly an electric system, for example, a sensor network, using low-cost and open-source elements. To achieve this objective, an inductive system has been modelled and validated to power wirelessly a sensor node using a Crazyflie 2.0 as MAV. The design of the inductive system must be small and light enough to fulfil the requirements of the Crazyflie. An inductive model based on two resonant coils is presented. Several coils are defined to be tested using the most suitable resonant configuration. Measurements are performed to validate the model and to select the most suitable coil. While attempting to minimize the weight at transmitter’s side, on the receiver side it is intended to efficiently acquire and manage the power obtained from the transmitter. In order to prove its feasibility, a temperature sensor node is used as demonstrator. The experiment results show successfully energy transportation by MAV, and wireless power transfer for the resonant configuration, being able to completely charge the node battery and to power the temperature sensor.Peer ReviewedPostprint (published version

In situ characterization of two wireless transmission schemes for ingestible capsules

We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications

Fast design space exploration of vibration-based energy harvesting wireless sensors

An energy-harvester-powered wireless sensor node is a complicated system with many design parameters. To investigate the various trade-offs among these parameters, it is desirable to explore the multi-dimensional design space quickly. However, due to the large number of parameters and costly simulation CPU times, it is often difficult or even impossible to explore the design space via simulation. This paper presents a response surface model (RSM) based technique for fast design space exploration of a complete wireless sensor node powered by a tunable energy harvester. As a proof of concept, a software toolkit has been developed which implements the proposed design flow and incorporates either real data or parametrized models of the vibration source, the energy harvester, tuning controller and wireless sensor node. Several test scenarios are considered, which illustrate how the proposed approach permits the designer to adjust a wide range of system parameters and evaluate the effect almost instantly but still with high accuracy. In the developed toolkit, the estimated CPU time of one RSM estimation is 25s and the average RSM estimation error is less than 16.5

A Question of Coherence

open1noElectromagnetic waves were first postulated by James Clerk Maxwell (1831-1879) in 1865. To demonstrate their existence 22 years later, Heinrich Hertz (1857-1894) had to design new instrumentation that he used to carry out an experiment than had never been performed before. To detect the waves produced by his oscillating electric circuit, he used a very crude receiver, subsequently known as the Hertz resonator.openGuarnieri, MassimoGuarnieri, Massim

HVAC SYSTEM REMOTE MONITORING AND DIAGNOSIS

A monitoring system for an HVAC system of a building includes a monitoring server located remotely from the building. The monitoring server receives, from a device installed at the building, (i) time-domain current data based on a measured aggregate current supplied to a plurality of components of the HVAC system, and (ii) data based on frequency-domain current data of the measured aggregate current. Based on the received data, the monitoring server accesses (i) whether a failure has occurred in a first com ponent of the plurality of components and (ii) generates a preliminary advisory in response to determining that the failure has occurred. The monitoring server compares the preliminary advisory to a threshold value based on data stored from prior advisories. If the preliminary advisory is on a first side of the threshold value, the monitoring server provides the preliminary advisory as a first advisory to a technician for review

Design and Development of a Class EF2 Inverter and Rectifier for Multi-megahertz Wireless Power Transfer Systems

This paper presents the design and implementation of a Class EF2 inverter and Class EF2 rectifier for two -W wireless power transfer (WPT) systems, one operating at 6.78 MHz and the other at 27.12 MHz. It will be shown that the Class EF2 circuits can be designed to have beneficial features for WPT applications such as reduced second-harmonic component and lower total harmonic distortion, higher power-output capability, reduction in magnetic core requirements and operation at higher frequencies in rectification compared to other circuit topologies. A model will first be presented to analyze the circuits and to derive values of its components to achieve optimum switching operation. Additional analysis regarding harmonic content, magnetic core requirements and open-circuit protection will also be performed. The design and implementation process of the two Class-EF2-based WPT systems will be discussed and compared to an equivalent Class-E-based WPT system. Experimental results will be provided to confirm validity of the analysis. A dc-dc efficiency of 75% was achieved with Class-EF2-based systems