Contactless Transfer Research Articles

Reflective vortex focusing for acoustic contact-free object rotation

The use of acoustic vortex waves with angular momentum is a promising means of transferring mechanical torque to an object without making any physical contact. However, the existing passive-conversion vortex lenses are unable to produce strong acoustic radiation torque. To address this issue, we propose a flat reflector sculpted by spiral grooves. It reflects and converts incident waves into vortex-focusing waves that generate radiation torque. Compared with a transmission-type lens, a reflection-type vortex focusing plate exhibits superior functionality in converging sound waves and creating a stronger circular intensity flow. In this work, we analyze the vortex-focusing sound by Rayleigh-Sommerfeld integral theory and boundary element simulation, confirmed by experiments. The number, depth and direction of spiral grooves determine the topological charge, focusing intensity and torque direction, respectively. We evaluate the local and total acoustic radiation forces and torques, acting on small and large fixed spherical targets in the vortex-focusing beam. As a result, spinning a centimeter-size origami pinwheel several times larger than the wavelength at 40 kHz is realized without direct contact, by utilizing the enhanced acoustic radiation torque converged by the reflector. This technology enables efficient convergence of acoustic waves and simultaneous contactless transfer of mechanical torque to an object, thereby presenting potential applications in sound energy harvesting and wireless power supplies.

Multi-focal transmission acoustic phase holograms in contactless ultrasonic power transfer systems

Using a pre-designed, simple, and cost-effective acoustic hologram alongside a single ultrasonic transducer, as an acoustic source/transmitter, enables new capabilities in multi-focal focusing, acoustic patterning, and contactless ultrasonic power transfer (UPT), to selectively charge sensors/receivers. In this work, different multi-focal holograms are designed that cover single- to four-focus acoustic patterning for UPT purposes. The holograms are numerically designed to create multi-focal pressure patterns in a target plane where an array of receivers are placed. The incident sound wave from a transmitter, after passing through the hologram, is manipulated, hence, the output field is the desired pressure field, which excites the receivers located at the pre-determined focal points more significantly. Proof-of-concept experiments are also performed for a five-element receiver setup, using a two-focus hologram, to selectively power two specific receivers. The experiments indicate a significant electrical average power output enhancement ratio of 23.4 from the targeted receivers, compared to untargeted ones, which proves the functionality of the designed multi-focal holograms in arbitrarily patterning the contactless transfer of ultrasonic power.

Textile-Based Coils for Inductive Wireless Power Transmission

We developed and evaluated different textile-based inductive coils for near-field wireless power transmission. The technology uses electromagnetic induction for the contactless transfer of electrical energy. Therefore, we investigated various methods for the attachment of conductive materials on a textile-based material and the production of textile-based coils based on QI standard. Afterwards, the textile-based coils were examined and evaluated due to their specific quality characteristics. This happens by calculating the transmission quality and the maximum efficiency of the system which enables comparison of different coil systems and indicates the transmission efficiency of the systems.

A study on contactless airborne transfer of textile fibres between different garments in small compact semi-enclosed spaces

Interpretation of fibre evidence at activity level requires extensive knowledge of all the possible transfer mechanisms that may explain the presence of fibres on a recipient surface of interest. Herein, we investigate a transfer method that has been largely understudied in previous literature: contactless transfer between garments through airborne travel. Volunteers were asked to wear UV-luminescent garments composed of different textile materials and situate themselves in a semi-enclosed space (elevator) for a pre-determined period of time with other participants, who wore non-luminescent recipient garments. The latter were then inspected for fibres using UV-luminescent photographic techniques. Results showed that contactless transfer between garments is possible. Indeed, a number of fibres were observed after most of the experiments. As many as 66 and 38 fibres were observed in the experiments involving cotton and polyester donor garments, compared to 2 and 1 fibres in those involving acrylic and wool donor garments, respectively. In this regard, the type of donor garment was found to be a significant factor. Multifactorial ANOVA supported these observations (p<0.001) and further indicated a statistically significant influence of elevator door opening/closing (p<0.001), people entering/exiting (p=0.078) and the recipient garment (p=0.030). Therefore, contactless transfer of fibres between garments can occur and can do so in (ostensibly) high numbers. This should be taken into consideration when interpreting fibre evidence at activity level and may have a major implication for the assignment of evidential values in some specific cases.

Concept of a Bonding Technology for Dies below 150 Micrometers

Due to rising demand for electrically contacted bare dies, bonding rates are to be increased. Technically, however, current bonding processes are almost at their limit. The use of continuous and consistent kinematics of the carrier substrate which allows no mechanical forces during die transfer is made possible by an optically induced, contactless transfer of the dies. The transfer can be triggered with an 8 ns laser impulse at a wavelength of 1064 nm, which detaches dies from a glass wafer and attaches them onto a carrier substrate.

Modeling of a Magnetic Coupler Based on Single- and Double-Layered Rectangular Planar Coils With In-Plane Misalignment for Wireless Power Transfer

This article proposes an analytical model that provides accurate self-inductance and mutual inductance calculations for two mutually coupled rectangular, planar, and spiral coils with an air core, which are equal and parallel, including the possibility of a lateral misalignment. Both single- and double-layered coil geometries were modeled by considering an arbitrary number of turns with a circular cross section per layer. The model equations, which can be readily implemented in software, are the results of a systematic approach that starts from the equations for the self-inductance of a wire and the mutual inductance of two parallel and misaligned wires that lie on the same plane. Accuracy is guaranteed by considering all the magnetic interactions among the individual turns in the two coils, while the simplifications involve only the calculations made at the corners of the coils. The model was validated by taking as reference experimental measurements carried out on a rectangular and a square magnetic coupler. A second analytical model, based on equivalent single-turn coils, was also tested for comparison purposes. The validation was extended with finite-element analysis tools by considering a wide range of coil side lengths, air gaps, number of turns, and lateral misalignments. The proposed model can, therefore, be regarded as a reliable tool to aid in the design of rectangular-shaped air-core magnetic couplers with applications in the contactless transfer power that are not necessarily limited to vehicle electrification.

Contactless Transfer of an Angular Momentum to a Liquid Layer Using a Scanning Laser Beam

The contactless transfer of an angular momentum to a liquid layer using a scanning laser beam has been experimentally investigated. This effect is observed for a glassy carbon target placed in water and irradiated by a pulsed laser beam, scanning the target along a closed trajectory. The target rotates in the same direction as the laser beam if the water layer is thin and in the opposite direction in the case of thick water layer. The possibility of transferring an angular momentum to liquid in the absence of target is demonstrated. The effect observed is interpreted as the result of joint action of convective flows and thermocapillary convection, which are induced in the liquid by laser heating.

Long-lived laser-induced arc discharges for energy channeling applications

Laser filamentation offers a promising way for the remote handling of large electrical power in the form of guided arc discharges. We here report that it is possible to increase by several orders of magnitude the lifetime of straight plasma channels from filamentation-guided sparks in atmospheric air. A 30 ms lifetime can be reached using a low-intensity, 100 mA current pulse. Stability of the plasma shape is maintained over such a timescale through a continuous Joule heating from the current. This paves the way for applications based on the generation of straight, long duration plasma channels, like virtual plasma antennas or contactless transfer of electric energy.

Self-Oscillating Josephson Quantum Heat Engine

The design of a mesoscopic self-oscillating heat engine that works thanks to purely quantum effects is presented. The proposed scheme is amenable to experimental implementation with current state-of-the-art nanotechnology and materials. One of the main features of the structure is its versatility: The engine can deliver work to a generic load without galvanic contact. This makes it a promising building block for low-temperature on-chip energy management applications. The heat engine consists of a circuit featuring a thermoelectric element based on a ferromagnetic insulator-superconductor tunnel junction and a Josephson weak link that realizes a purely quantum DC/AC converter. This enables contactless transfer of work to the load (a generic RL circuit). The performance of the heat engine is investigated as a function of the thermal gradient applied to the thermoelectric junction. Power up to $1$ pW can be delivered to a load $R_L=10\ \Omega$.

A Novel Fully Superconducting Geared Machine

In this paper, topologies for fully superconducting machines are analyzed. Then, a novel fully superconducting machine topology-fully superconducting geared machine is developed. The proposed topology is featured with contactless torque transfer capability and high torque density. Furthermore, the performances, such as back electromotive force and torque waveform, and performance comparisons between proposed machine and typical fully superconducting machine are done. It is found that the proposed topology could obtain much higher torque density than that of the typical fully superconducting machine. Meanwhile, its auxiliary components, such as seals, dewar, become much simpler due to its contactless torque transfer capability.

Holograms for acoustics.

Holographic techniques are fundamental to applications such as volumetric displays, high-density data storage and optical tweezers that require spatial control of intricate optical or acoustic fields within a three-dimensional volume. The basis of holography is spatial storage of the phase and/or amplitude profile of the desired wavefront in a manner that allows that wavefront to be reconstructed by interference when the hologram is illuminated with a suitable coherent source. Modern computer-generated holography skips the process of recording a hologram from a physical scene, and instead calculates the required phase profile before rendering it for reconstruction. In ultrasound applications, the phase profile is typically generated by discrete and independently driven ultrasound sources; however, these can only be used in small numbers, which limits the complexity or degrees of freedom that can be attained in the wavefront. Here we introduce monolithic acoustic holograms, which can reconstruct diffraction-limited acoustic pressure fields and thus arbitrary ultrasound beams. We use rapid fabrication to craft the holograms and achieve reconstruction degrees of freedom two orders of magnitude higher than commercial phased array sources. The technique is inexpensive, appropriate for both transmission and reflection elements, and scales well to higher information content, larger aperture size and higher power. The complex three-dimensional pressure and phase distributions produced by these acoustic holograms allow us to demonstrate new approaches to controlled ultrasonic manipulation of solids in water, and of liquids and solids in air. We expect that acoustic holograms will enable new capabilities in beam-steering and the contactless transfer of power, improve medical imaging, and drive new applications of ultrasound.

Integrating RFID Transponders as Data Loggers in Wireless Sensor Nodes for Outdoor Remote Monitoring Operations

In this paper the integration of an RFID system into a wireless sensor node based on an Arduino board is discussed. The main purpose of the proposed solution is to use the memory of a passive RFID transponder to store the data retrieved by the sensors composing the node. This solution can be employed for remote monitoring operations, when no connection is available and then no remote data collection is possible. The RFID transponder allows the storage of a large number of sensor data sets, that can be then acquired simply removing the transponder from the node and reading it with a common desktop reader. Once collected, the transponder is replaced with a new one allowing a new period of data collection regardless of human intervention. An ad-hoc data structure has been studied to optimize the memory usage and then to increase the life time of a single transponder. The solution is especially thought for outdoor monitoring operations: contactless data transfer allows the sensor node to be sealed and then to be totally protected from atmospheric agents.

Contactless transfer of image via the gas phase in a thermoactivated process

The formation of hafnium oxide (HfO2) layers in slit structures by pulsed metalorganic chemicalvapor deposition (MOCVD) method with discrete dosage of reactants has been studied. The MOCVD process employed hafnium tetrakisdipivaloylmethanate as a precursor and oxygen as a gaseous reactant. The slit structure was formed by a silicon plate and a glass substrate with a chromium-film pattern. The slit width was varied within 0.1–2.0 mm, so that the aspect ratio changed from 150 to 30. The deposited layers were studied by the scanning ellipsometry technique. The phenomenon of image transfer from the glass substrate to the opposite plate in the form of a nanosized HfO2 film relief, which reproduces the chromium-film pattern, is discovered. The in-plane resolution of the obtained image in these experiments reached 0.025 mm. This effect can be used for nonlithographic formation of images of film structures.

Inductive High Power Transfer Technologies for Electric Vehicles

Abstract Problems associated with ”how to charge the battery pack of the electric vehicle” become more important every passing day. Most logical solution currently is the non-contact method of charge, possessing a number of advantages over standard contact methods for charging. This article focuses on methods for Inductive high power contact-less transfer of energy at relatively small distances, their advantages and disadvantages. Described is a developed Inductive Power Transfer (IPT) system for fast charging of electric vehicles with nominal power of 30 kW over 7 to 9 cm air gap.

Study on the principle of contactless electric power transfer via electromagnetic coupling

AbstractIn recent years, contactless transfer of electric power has received worldwide attention. Among many contactless electric power transmission systems, an electromagnetic resonant system showed a remarkable ability to turn on a 60‐watt light bulb located at a distance of 2 meters from a power source. Several papers that explain principles of the system have been published, but no analytical explanation of these principles has been provided. In this paper, the author provides an analytical explanation of the principle underlying the power transfer system. The analysis can facilitate the evaluation of the system characteristics, such as resonant frequencies, transferable power, efficiency, coil voltages, etc., and may be useful in the synthesis of contactless power transfer systems. Electr Eng Jpn, 182(2): 53–60, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21285 2

Computer Model for Railway Inductive Power Supply Using the Valtchev Model

This paper presents contactless power supply systems using the Valtchev model in transportation systems. The major drawback of contactless systems is that the efficiency is lower than that of contact systems. The coupling coefficient of the contactless transformer is the most influential parameter on the system efficiency. Here, a new computer model for the contactless transfer system developed in the Korea Railroad Research Institute is presented. Also, simulations of the old model and the new model are compared with the prototype measurement to assure the model validity.

Contactless transfer of conductive rod using an electrodynamic wheel

A novel electrodynamic wheel is proposed to convey a conductive rod. When rotating the spiral electrodynamic wheel around the conductive rod, a radial force and an axial force are generated, and are used to convey the rod without mechanical contact. However, even though the radial force acting on the rod is a repulsive force, the spatial stability of the rod is not always guaranteed in the uncontrolled mode. The stability depends fully on the operating condition. So, for the proposed conveyance system, the operating conditions for dynamic stability of the rod are clarified on the basis of dynamic analysis and finite element analysis (FEA) with experimental verification, thereby showing the feasibility of the proposed conveyance system. A test setup is designed and used to analyze the effect of the relative position between permanent magnets (PMs) constituting the wheel, and the pole number of PMs.

電磁結合による非接触電力伝送の原理について

In recent years, contactless transfer of electric power has received worldwide attention. Among many contactless electric power transmission systems, an electromagnetic resonant system showed a remarkable ability to turn on a 60 watt light bulb that was at a distances of 2 meters from a power source. Several papers that explain the principle of the system have been published, but an analytical explanation of this principle has not been provided. In this paper, the author provides an analytical explanation of the principle behind the power transfer system. The analysis can facilitate the evaluation of the characteristics of the system, such as resonant frequencies, transferable power, efficiency, coil voltages, etc., and may be useful in the synthesis of contactless power transfer systems.

Increasing the sensitivity and accuracy of an instrument for measuring the torque of a rotating shaft with electromagnetic coupling to a surface acoustic wave sensor

The particular features of the measurement of the torque of a rotating shaft using a surface acoustic wave sensor are considered. An approach to choosing the parameters of a contactless transfer device and a piezoelectric substrate for such a sensor, which enables the measurement accuracy to be increased, is proposed.

An Airborne Radar Power Supply With Contactless Transfer of Energy—Part I: Rotating Transformer

Reliability and precision are key requirements for electronic systems in aerospace applications. Transferring electrical energy from a stationary to a moving device involves wearable parts such as slip rings and brushes. This paper examines the possibility of using a rotating transformer for contactless transfer of energy from the base to the revolving platform of an airborne radar system. The first part of the series focuses on the magnetic interface, investigating its electrical properties and their association with the core and windings geometry. The reader will gain an understanding of the merits and limitations of this technology and will be able to assess its suitability for other applications. The effects of the increased leakage and reduced magnetizing inductances of the transformer are investigated, and two winding layouts are proposed and characterized by measurements and finite-element analysis. Some equations are presented along with practical guidelines on designing a rotating transformer with a 0.25-2-mm air gap. The transformer voltage gain and efficiency plots are introduced as performance-assessment tools. The impact of the air-gap stray flux on the winding conduction losses is shown, and some electromagnetic-compatibility considerations are presented. Finally, a mechanical layout for a 1-kW rotating transformer is proposed.