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This letter examines the contact and constriction resistance phenomena in the context of 3-D-printed electronics, with a focus on exploring the use of constriction resistance for force sensing. We design and manufacture a sensor using carbon-black conductive thermoplastic polyurethan on a fused deposition modeling 3-D printer and test it using a geometry-based resistive model to fit the data to a number of possible force–resistance relations found in the literature. The sensor exhibits low hysteresis between force and resistance, and good sensitivity at low forces, while at high forces, it displays consistent contact and stable resistance. We analyze the design methodology and offer recommendations for future sensor design and fitting options, as well as put forward approaches to maximizing force sensitivity. Although the exact model derived in this letter is not directly transferable to other sensors, the workflow can serve as a useful guide for future research.

Compact power electronic circuits and higher operating temperatures of switching devices call for an analysis and verification on the impact of the parasitic components in these devices. The found drift mechanisms in a gallium-nitride field effect transistors (GaN-FET) are studied by literature and related to measurement results. The measurements in extreme temperature conditions are far beyond the manufacturer-recommended operating range. Influences to parasitic elements in both static and dynamic operation of the GaN-FETs are investigated and related toward device losses in switch-mode power electronic circuits with the example of a half-bridge circuit. In this article, static operation investigation on the effect of temperature toward resistance, leakage currents, and reverse conduction is conducted. Dynamic operation between the two states of GaN-FET is also addressed and related to the potential impact in a switching circuit losses. A thermal chamber was built to precisely measure the effect of temperature toward parasitic elements in the devices using a curve tracer. It was found that the increment in RDSon, IDSS, IGSS, and VSD can be justified by the literature and verified by measurements. Incremental COSS and decreasing VGSth was found when exposing devices to extreme temperatures. These two parameters give real challenge over designing circuits at high temperature where timing is critical. Albeit temperature challenges, it is found that investigated GaN-FETs have potential to be used in extreme temperature-operating conditions.

Today's consumer electronics are made from nonrenewable and toxic components. They are also rigid, bulky, and manufactured in an energy-inefficient manner via CO2-generating routes. Though petroleum-based polymers such as polyethylene terephthalate and polyethylene naphthalate can address the rigidity issue, they have a large carbon footprint and generate harmful waste. Scalable routes for manufacturing electronics that are both flexible and ecofriendly (Fleco) could address the challenges in the field. Ideally, such substrates must incorporate into electronics without compromising device performance. In this work, we demonstrate that a new type of wood-based [nanocellulose (NC)] material made via nanosilicate (NS) reinforcement can yield flexible electronics that can bend and roll without loss of electrical function. Specifically, the NSs interact electrostatically with NC to reinforce thermal and mechanical properties. For instance, films containing 34 wt % of NS displayed an increased young's modulus (1.5 times), thermal stability (290 → 310 °C), and a low coefficient of thermal expansion (40 ppm/K). These films can also easily be separated and renewed into new devices through simple and low-energy processes. Moreover, we used very cheap and environmentally friendly NC from American Value Added Pulping (AVAP) technology, American Process, and therefore, the manufacturing cost of our NS-reinforced NC paper is much cheaper ($0.016 per dm-2) than that of conventional NC-based substrates. Looking forward, the methodology highlighted herein is highly attractive as it can unlock the secrets of Fleco electronics and transform otherwise bulky, rigid, and "difficult-to-process" rigid circuits into more aesthetic and flexible ones while simultaneously bringing relief to an already-overburdened ecosystem.

Splitting and placing interfacing inductance on both sides of the transformer has been proven to be an effective method, which extends the zero-voltage switching (ZVS) region for all the switching devices in the dual active bridge (DAB) converter. With the trend towards operating in higher frequency, achieving higher power density and higher efficiency, the converter model becomes more complex due to the non-negligible parasitic components that brings new challenges to DAB converter design. Traditional analytical methods have become hardly to imitate the proposed converter neither easily or precisely. Thus, artificial intelligence (AI) techniques are able to be utilized to assist the design process. When considering the converter system as a gray-box model, the metaheuristic algorithm can be implemented for the targeted design inside such gray-box. In this paper, a genetic algorithm (GA) is employed in the DAB converter parametric design with an explicit fitness desire and helps in discovering the high frequency oscillation (HFO) problem. Consequently, the splitting inductance tuning method is proposed for eliminating the HFO problem and minimizing inductors' loss. The methodology of implementing GA into converter parametric design and the proposed splitting inductance tuning method are introduced and verified with a 1 MHz GaN based DAB converter prototype.

Additive manufacturing of thermoplastic conductive polymer composites offers interesting opportunities for customizing compliant flexural sensors. The study aimed to show that additive manufacturing could be used to fabricate flexural sensors for evaluating the effect of sensor geometry on the sensor output. Prior literature has primarily focused on material optimization rather than geometrical design. The results of this paper show that the signal amplitude between geometrically different flexural sensors with the same footprint can increase ∼28 times. In addition, the bending force is found proportional to the signal amplitude. Thus, concentrating the bending to a small section increases the signal amplitude but also increases the effect of material relaxation broadening the hysteresis loop. This study highlights the importance of considering the geometrical design when fine-tuning additive manufactured flexural sensors. In future work, it is paramount to improve reproducibility, signal linearity, and investigate the effects of geometry on other sensor parameters.

Power line communication (PLC) is widely used in the well intervention industry to control tools performing maintenance on oil and gas well pipes. This paper compares PLC driver power amplifiers and the impact of temperature towards them. As both a Class AB and Class D amplifier stages form suitable candidates, a comparison is made on performance indicators, such as total harmonic distortion (THD) and intermodulation distortion (IMD), as well as power limitations and efficiency. Measurements are performed both at room temperature and at high temperature of 150 °C. The trade-off between Class AB and Class D based on the mentioned indicators is then further emphasized using plotted responses. These show a clear advantage in the use of a Class D amplifier topology based on efficiency by outperforming the Class AB topology by a factor of two at high temperature. However the THD is found to be approx. 25dB better in the Class AB amplifier. This article discusses and thereby identifies future research trends and topics required for high temperature PLC driving circuits.

There is a growing trend towards operating higher frequency in dual active bridge (DAB) converters to achieve higher power density. At the meantime, the high frequency oscillation (HFO) problem introduced by the parasitic components of the transformer and high dvldt of the ac link excitation voltage becomes detrimental. Matching the oscillation frequency with the zero crossing points (ZCP) of the DAB dvldt excitation has been proven effective to eliminate the HFO problem. In this paper, a splitting inductance tuning method is proposed to adjust the circuit frequency characteristic and place the lowest impedance path at the ZCP frequency, thus eliminating the HFO. Theoretical analysis is given along with the experimental results from a 1 MHz Gallium Nitride (GaN) based DAB converter prototype.

Biomaterials capable of transmitting signals over longer distances than those in rigid electronics can open new opportunities for humanity by mimicking the way tissues propagate information. For seamless mirroring of the human body, they also have to display conformability to its curvilinear architecture, as well as, reproducing native-like mechanical and electrical properties combined with the ability to self-heal on demand like native organs and tissues. Along these lines, a multifunctional composite is developed by mixing silk fibroin and reduced graphene oxide. The material is coined "CareGum" and capitalizes on a phenolic glue to facilitate sacrificial and hierarchical hydrogen bonds. The hierarchal bonding scheme gives rise to high mechanical toughness, record-breaking elongation capacity of approximate to 25 000%, excellent conformability to arbitrary and complex surfaces, 3D printability, a tenfold increase in electrical conductivity, and a fourfold increase in Young's modulus compared to its pristine counterpart. By taking advantage of these unique properties, a durable and self-healing bionic glove is developed for hand gesture sensing and sign translation. Indeed, CareGum is a new advanced material with promising applications in fields like cyborganics, bionics, soft robotics, human-machine interfaces, 3D-printed electronics, and flexible bioelectronics.

Design automation in power electronics has been highlighted in recent years. Design flow, multi-physics co-design, data standardization have been identified as the major gaps for engineers and researchers to fill. As an exploratory effort, this paper presents an automated design for the three-level neutral-point-clamped dc-dc converter. The design firstly uses analytical models to determine the circuit level parameters. The problem size can thereby be reduced. The parameter candidates left are fed to automated FEMM and COMSOL simulations for precise modeling of magnetic components. Database published by ferrite and powder core manufacturers is incorporated in the design. The code of the entire design flow has been published on GitHub.

This paper focuses on the development of a Python dataclass and SWAN notebooks allowing for automatic generation of PSPICE©models of the Large Hydron Collider (LHC) superconducting electromagnets and circuits installed at CERN. The models consist of inductors, resistors and capacitors, as well as RL-loops, modelling the behaviour of the magnets and circuits, including eddy-current effects. The dataclass can accommodate several types of magnets, and allows for custom fitting to measurements. Furthermore, the dataclass produces three different models for each magnet or circuit. The models differ in complexity trading computation time for accuracy. One of the circuit models was validated by experimental data. The dataclass was used to generate models of 37 LHC magnets and 63 circuits, as a part of the STEAM LHC circuit model library. The automatic functionality of the library provides an easy and quick way to both add and maintain the models in the library. Finally, the dataclass’ usability in regards to general inductors is assessed.

A partially parallel three level neutral point clamped (P2TLNPC) converter for applications with high and wide input voltage is presented in this paper. The basic operation of the P2TLNPC converter is introduced. The converter has the following advantages: reduced voltage stress on switches, variable voltage gain, simple modulation, inherent balancing of ac currents in parallelized modules. The operation of the converter is verified by experiments on a P2TLNPC prototype. The prototype uses Silicon Carbide (SiC) devices, and is able to maintain the output voltage stably at 500 V when the input voltage is stepped between 1 kV and 600 V.

Soft and electrically active materials are currently being utilized for intelligent systems, including electronic skin, cybernetics, soft robotics, and wearable devices. However, fabricating materials that fulfill the complex requirements of such advanced applications remains a challenge. These attributes include electronic, adhesive, self-healing, flexible, moldable, printable, and strong mechanical properties. Inspired by the recent interest in transforming monofunctional materials into multifunctional ones through nanoreinforcement and mussel-inspired chemistry, we have designed a simple two-step methodology based on halloysite nanotube (HNT) and polydopamine (PDA) to address the grand challenges in the field. In brief, HNTs were coated with PDA and embedded within a poly(vinyl alcohol) (PVA)-based polymeric matrix in combination with ferric ions (Fe

Parasitic components in eGaN-FETs impact the dynamic performance of switching stages. The capacitances seen, primarily on the output characteristics, of these devices are a main contributor towards switching losses and therefor converter efficiency. Additionally, the threshold voltage of the device has an impact towards the switching speed and therefore the efficiency of a power stage. This study shows the impact of extreme temperatures towards the parasitics that impact the switching behaviour of a power stage. A literature research is conducted exploring the various mechanisms and temperature dependancies, which are then related towards transient operations of eGaN-FETs. A device was chosen to perform measurements on output-, reverse transfer capacitance and threshold voltage while increasing temperature from 100°C op to 225°C. The presented results show a large impact of temperature in these parasisic elements that show that high temperature switch-mode power converters need additional design work to ensure switching performance and lifetime.

There is abundant research about achieving zero-voltage switching (ZVS) of dual active bridge (DAB) converters, among which the splitting of interfacing inductance and placing on both sides of the transformer is an effective method for extending the ZVS region for all the switching devices. However, the traditional analytical model can hardly imitate the proposed converter precisely under the high switching frequency (i.e.>1MHz) due to the complex converter model with the consideration of the parasitic components. Thus, the converter system can be regarded as a gray-box model. Consequently, artificial intelligence (AI) techniques can be utilized for the targeted optimization inside this gray-box. In this case, a genetic algorithm is employed in the DAB converter parametric design with an explicit fitness desire. The methodology of implementing AI techniques into converter parametric design is introduced and verified with a 1 MHz Gallium Nitride (GaN) based DAB converter prototype.

Exposure to an extreme ambient temperature leads to increased losses in a Gallium Nitride Field Effect Transistor (GaN-FET) when operating in a switch-mode power stage. The output capacitance of Gallium Nitride (GaN) devices is decreased at higher voltages but increased at higher temperatures. Thispaper highlights the effect of output capacitance in a half-bridge switching stage and offers analysis towards the switching losses. A power stage was built and tested with two timing optimizations: for room temperature and high temperature, respectively. Trading off dead time and the loss mechanisms involved, a loss reduction of 16.1% was achieved. This loss reduction was further improved to 26.1% after thorough investigation of the switch node transient responses.

Smaller packaging and sizing of power electronics and higher operating temperatures of switching devices call for an analysis and verification on the impact of the parasitic components in these devices. Found drift mechanisms in an eGaN-FET are studied by literature and related to measurements performed in extreme temeprature conditions far beyond the manufacturer recommended operating range. A thermal chamber was build to precisely measure the effect of temperature in these devices using a curve tracer. It is found that the increment in 𝑅𝐷𝑆𝑜𝑛, 𝐼𝐷𝑆𝑆, 𝐼𝐺𝑆𝑆 and 𝑉𝑆𝐷 can be justified by the theory and backed up by measurements. It is also found that the particular eGaN-FET can be suited for extreme temperature operating conditions.

Contains fulltext : 238926.pdf (Publisher’s version ) (Closed access) Soft and electrically active materials are currently being utilized for intelligent systems, including electronic skin, cybernetics, soft robotics, and wearable devices. However, fabricating materials that fulfill the complex requirements of such advanced applications remains a challenge. These attributes include electronic, adhesive, self-healing, flexible, moldable, printable, and strong mechanical properties. Inspired by the recent interest in transforming monofunctional materials into multifunctional ones through nanoreinforcement and mussel-inspired chemistry, we have designed a simple two-step methodology based on halloysite nanotube (HNT) and polydopamine (PDA) to address the grand challenges in the field. In brief, HNTs were coated with PDA and embedded within a poly(vinyl alcohol) (PVA)-based polymeric matrix in combination with ferric ions (Fe(3+)). The final composite displayed a 3-fold increase in electrical conductivity, a 20-fold increase in mechanical stiffness, and a 7-fold increase in energy dissipation in comparison to their nonfunctional counterparts, which arose from a combination of nanotube alignment and mussel-inspired chemistry. Moreover, the developed composite could elongate up to 30000% of its original length, maintain its electrical properties after 600% strain, self-heal within seconds (both electrically and mechanically), and display strain-sensitivity. Finally, it was 3D-printable and thus amenable for engineering of customized wearable electronics.

Minimizing transformer winding loss is a prominent factor to increase efficiency of power electronics converters. This is especially valid for modern switched-mode power supplies, where eddy current effects on windings become dominant due to continuously elevated switching frequency. In this paper, a field shaping technique, dubbed the field-cannon-technique, is proposed to mitigate eddy current effects in high frequency transformers’ foil windings. The basic principle and the implementation of the proposed technique is introduced. A model is derived using finite difference method, in order to calculate the distribution of the magnetic field within the transformers implemented with the field-cannon-technique. Finally, the technique is verified by experiments, where the winding resistance of the transformer is reduced by a factor of three.

A new method is implemented in designing of self-oscillating loop for driving piezoelectric transformers. The implemented method is based on combining both analog and digital control systems. Digitally controlled time delay through the self-oscillating loop results in very precise frequency control and ensures optimum operation of the piezoelectric transformer in terms of gain and efficiency. Time delay is implemented digitally for the first time through a 16 bit digital-to-analog converter in the self-oscillating loop. The new design of the delay circuit provides 45 ps time resolution, enabling fine-grained control of phase in the self-oscillating loop. This allows the control loop to dynamically follow frequency changes of the transformer in each resonant cycle. Ultimately, by selecting the optimum phase shift, maximum efficiency under the load and temperature condition is achievable.

Connectivity in smart devices is increasingly realized by wireless connections. The remaining reason for using connectors at all is for charging the internal battery, for which wireless power transfer is an alternative. Two industry standards, AirFuel and Qi, exist to support compatibility between devices. This work is focusing on the AirFuel standard, as it is operating at a higher frequency (6.78 MHz), than the Qi standard, and therefore allows smaller passive components, including the coupling coils. Whereas gallium-nitride (GaN) devices are being widely used on the transmitter (Tx) side, this work uses low voltage GaN transistors on the receiver (Rx) side to allow synchronous rectification and soft switching, thereby achieving high efficiency. After analyzing adequate Class-DE rectifier topologies, a ClassDE full-bridge 5 W rectifier using 15 V GaN transistors are designed and implemented. The experimental results show an efficiency above 80 % over a wide operating range and a peak efficiency of 89 %, at an arbitrary alignment of Tx and Rx coils with 3 cm distance between them.

In article number 1801241, Alireza Dolatshahi‐Pirouz and co‐workers develop an ultra‐sensitive, but low‐cost electrode with a broad range of exciting properties brought about through a simple “design and mixing procedure.” As examples, a touch panel screen for use in foldable electronics and a human motion sensitive device are manufactured with the electrode.

Contains fulltext : 215371.pdf (Publisher’s version ) (Open Access) Proteins present an ecofriendly alternative to many of the synthetic components currently used in electronics. They can therefore in combination with flexibility and electroactivity uncover a range of new opportunities in the field of flexible and green electronics. In this study, silk-based ionic conductors are turned into stable thin films by embedding them with 2D nanoclay platelets. More specifically, this material is utilized to develop a flexible and ecofriendly motion-sensitive touchscreen device. The display-like sensor can readily transmit light, is easy to recycle and can monitor the motion of almost any part of the human body. It also displays a significantly lower sheet resistance during bending and stretching regimes than the values typically reported for conventional metallic-based conductors, and remains fully operational after mechanical endurance testing. Moreover, it can operate at high frequencies in the kilohertz (kHz) range under both normal and bending modes. Notably, our new technology is available through a simple one-step manufacturing technique and can therefore easily be extended to large-scale fabrication of electronic devices.

This paper describes the implementation of a generator as a source of resistance in a modern kayaking ergometer. This ergometer can function as a platform for emulation of the athlete-kayak-paddle system. The system was considered and described. A possible model for digital regulation has also been described. A synchronous-rectified buck converter has been designed to control the current through the rotor and, by extension, the mechanical resistance felt by the oarsman. The circuit was designed to function with a 12V car battery as a supply. Necessary specifications for efficiency and output stability were set, measured and met. The prototype without regulation was presented at the 2015 Kayaking World Cup, and was met with appreciation and positive feedback.

The Piezoelectric Actuator Drive (PAD) is a new type of electrical motor that employs piezoelectric multilayer actuators coupled with a form-fitted micro-mechanical gearing to generate rotary motion. The PAD is precise, having a positioning error of less than 2 arc-seconds. Its typical output torque is 4N · m, without any additional gearing. The whole motor is fully non-magnetic, enabling its use in applications where magnetic neutrality is of importance. The main challenges of the PAD are the hysteretic behavior of the ceramic actuators used and their highly capacitive nature. After compensating for the hysteretic behavior, the current waveforms of the motor can be used to extract all necessary parameters for sensorless operation. Moreover, these signals provide a qualitative information about the precision in motor centering and show any mismatch between the actuators used.

The Piezoelectric Actuator Drive (PAD) is an accurate, high-torque rotary piezoelectric motor that employs piezoelectric stack actuators and inverse hypocycloidal motion to generate rotation. Important factors that determine motor performance are the proper concentric alignment between the motor ring and shaft and the similarity of the stack actuators used. This paper investigates the electromechanical coupling of these factors into the motor current through experimental means.

The invention relates in a first aspect to a resonant power converter comprising: a first power supply rail for receipt of a positive DC supply voltage and a second power supply rail for receipt of a negative DC supply voltage. The resonant power converter comprises a resonant network with an input terminal for receipt of a resonant input voltage from a driver circuit. The driver circuit is configured for alternatingly pulling the resonant input voltage towards the positive and negative DC supply voltages via first and second semiconductor switches, respectively, separated by intervening dead-time periods in accordance with one or more driver control signals. A dead-time controller is configured to adaptively adjusting the dead-time periods based on the resonant input voltage.

This paper presents a method of reducing load friction in two degrees-of-freedom (2-DOF) transparent electrostatic induction actuator by using vibration-induced squeeze film effect. An experimental set-up was built to prove the concept. An overall 70% reduction in required driving voltage was obtained when the squeeze film is present.

Electrostatic precipitators (ESPs) are important parts of many industrial plants. They require high-voltage power supplies. In this paper, transformer/rectifier sets, a particular type of power supplies for the energization of ESPs, are presented and modeled using Modelica. The models have been validated with measurements from existing plants

The Piezoelectric Actuator Drive (PAD) is a precise piezoelectric motor generating high-torque rotary motion, which employs piezoelectric stack actuators in a wobble-style actuation to generate rotation. The piezoelectric stacked ceramics used as the basis for motion in the motor suffer from hysteretic nonlinearities. In order to model these nonlinearities, the first-order hysteresis reversal curves of the actuators are measured and a discrete Preisach model is derived. This forms a basis that enables the study of different compensation methods. The results show matching between measured and estimated responses within 95.8%.

The Preisach model is a powerful tool for modelling the hysteresis phenomenon on multilayer piezo actuators under large signal excitation. In this paper, measurements at different temperatures are presented, showing the effect on the density of the Preisach matrix. An energy-based approach is presented, aiming at defining a temperature-dependent phenomenological model of hysteresis for a better understanding of the non-linear effects in piezo actuators.

The invention relates in a first aspect to a resonant power converter comprising a synchronous rectifier for supplying a DC output voltage. The synchronous rectifier is configured for alternatingly connecting a resonant output voltage to positive and negative DC output nodes via first and second semiconductor switches, respectively, separated by intervening dead-time periods in accordance with first and second rectification control signals. A dead-time controller is coupled to the resonant output voltage or the resonant input voltage and configured for adaptively adjusting lengths of the dead-time periods via the first and second rectification control signals.