Impedance Range Research Articles

Impedance for Assistance: Upper-Limb Assistive Soft Robotic Suit Using Linked-Layer Jamming Mechanisms.

Wearable robots, especially those composed of soft materials, are increasingly attracting interest due to their comfort, ease of donning and doffing, and their ability to provide assistance across various applications. In wearable robotics, striking a balance between ensuring low impedance for wearer comfort and providing sufficient assistive force is a notable design challenge. In this study, we propose exploiting impedance variation in accordance with the types of muscle contraction in the human body. Particularly in eccentric muscle contraction, the impedance can help reduce the muscular load, since it exerts force in the same direction as the muscles. To utilize the relation, we proposed a linked-layer jamming mechanism, which adjusts its impedance largely in various directions. This mechanism allows not only a broad variable range of impedance in multiple rotation directions but also directional torque design, even when equipped in human multi-degree-of-freedom (DoF) joints. By constructing a wearable robot prototype equipped with the proposed linked-layer jamming mechanisms, the effectiveness of this impedance-based assistance approach was confirmed through experiments. The findings from this study present new possibilities in wearable robot design, showing that suitably amplified impedance can assist human motion, potentially enhancing task efficiency and lowering injury risk. This work thus offers a new perspective for researchers in the field of wearable robots, demonstrating that impedance, often minimized in existing designs, can be utilized beneficially when properly amplified.

High-temperature water vapor sensors based on rare-earth-doped barium cerate

In this novel study, BaCe0.9Y0.1O3–δ, BaCe0.9Eu0.1O3–δ, BaCe0.9Nd0.1O3–δ, and BaCe0.9Dy0.1O3–δ powders were synthesized by the self-combustion method and processed into thick porous films (60–70 % porosity) to investigate the water vapor sensing properties in the 400–700 °C temperature range. All samples showed a stable response value to water vapor in the whole temperature range, expressed as impedance ratio in dry and wet argon (ZdryAr/ZwetAr), and were able to detect 0.03 vol% of water vapor at 550 °C within the impedance range of 103 Ω at 100 Hz. The response values increased with the partial pressure of water and decreased with the temperature, whereas the maximal value of 3.41 reached the BaCe0.9Eu0.1O3–δ sample at 550 °C and p(H2O) = 4.28 kPa. The average response time was several seconds and only slightly changed with the material type and experimental conditions. The recovery time depended on temperature and the ZdryAr/ZwetAr ratio, whereas the increase in the gas flow rate from 100 cm3/min to 200 cm3/min significantly reduced the recovery time for the BaCe0.9Eu0.1O3–δ sample from 230 s to 55 s at 550 °C and p(H2O) = 2.14 kPa. All the samples exhibited stability and a high degree of reversibility after multiple exchanges of wet and dry atmospheres at different temperatures. Yet, their tendency to deteriorate in the presence of CO2 might challenge a potential application in aggressive environments.

Stochastic Inversion in Determining the Distribution of Petroleum Carrying Sandstones in the "JS" Field of the South Sumatra Basin

The "JS" field is a field located in the South Sumatra Basin, where the field has good prospects for the distribution of petroleum-bearing sandstone. The target of this research is the Air Benakat formation. This research uses the stochastic seismic inversion method to determine the probability of finding petroleum in sandstone. Stochastic seismic inversion has the advantage that it can overcome thin layers and can reduce existing data misalignments. So stochastic inversion can overcome the shortcomings of other seismic inversions, especially model-based seismic inversion which is the initial model for stochastic seismic inversion. Stochastic seismic inversion produces several realizations by showing uncertainty so as to get results that are close to the actual situation. Probability map of oil-bearing sandstones located in the north and east of the study area. with the slice results obtained for the acoustic impedance range of 8517-9051(m/s)*(g/cc) and oil sand probability with a value range of 0.61-0.78%.

Engineered substrates for metasurface antennas

This letter explores the advantages of additively manufactured substrates with spatially varying electromagnetic properties. These engineered substrates will be constructed using space filling curves (SFC) of various orders. New advanced manufacturing systems such as the nScrypt 3Dn-300, have enabled the rapid fabrication of these SFC substrates. This letter will apply the engineered SFC substrate to the design and fabrication of metasurface antennas. By utilising a SFC to vary the local substrate permittivity, along with the printed conductive patch dimensions, the range of achievable surface impedances can be greatly expanded. This enlarged design space will be leveraged to yield increased gain for a given metasurface antenna size. Methods to characterise the substrate permittivity and conductive ink are discussed along with a complete description of the metasurface antenna design, fabrication and validation process.

Impedance remodeling control strategy of grid-connected inverter with inertia-damping phase-locked loop under extremely weak grid

The operation of the grid-connected inverter (GCI) in weak grid conditions presents a risk of instability due to the presence of high grid impedance and the negative impedance effect of the phase-locked loop (PLL). In response to this issue, this paper introduces an impedance remodeling control strategy for the GCI utilizing the inertia-damping phase-locked loop (ID-PLL). Firstly, the proposed ID-PLL exhibits certain inertia and damping properties in comparison to the traditional PLL (T-PLL), resulting in an enhanced phase margin of the GCI system's equivalent output impedance. Consequently, the adaptation range of the grid impedance increases from 12mH (SCR = 3.00) to 24mH (SCR = 1.37). Next, from the perspective of impedance analysis, this study remodels the PLL impedance and inverter control loop impedance, further improving the amplitude and phase margin of the system's output impedance. As a result, the adaptation range of the grid impedance extends to 33mH (SCR = 1.00), and the transition of grid-connected currents becomes smooth and free of overshoot. Finally, the effectiveness of the proposed control strategy is validated through theoretical analysis and experimental verification.

Characterizations for eWLB (Embedded Wafer Level Ball Grid Array) Antenna in Molded Package Integrations in 77GHz Automotive Applications

The worldwide IC market has had a significant growth rate in recent years, driving diversified package solutions in the segments of communication, computing, consumer, automotive, industrial, etc. Among these market segments, the automotive market is forecast to have the strongest CAGR (Compound Annual Growth Rate) of any of the end-use segments in the next 5 years, which results in more IC packages and components being designed into automotive vehicle systems such as infotainment, ADAS (Advance Driving Assistance System), instrumentation, body systems, battery control systems and so on. In these applications, the 77GHz short-range radar sensor application that can enable higher EIRP (Effective Isotropic Radiated Power) and adaptive cruise control performance has become more attractive to be commercialized. Due to the benefits of shorter interconnection length, lower conductive loss with smooth Cu surface as well as a lower dielectric constant and dielectric loss of materials in a fan-out wafer level package (FOWLP) technology, the FOWLP is proven as a suitable packaging solution to achieve the high speed and frequency requirements in 5G and mmWave applications. The eWLB Embedded Wafer Level Ball Grid Array) is a versatile FOWLP technology, providing a robust package platform in a space-efficient design with the very dense interconnection and routing of multiple dies as well as a smaller footprint and lower package profile providing a reliable package solution. Meanwhile, since the utilization of an antenna that is integrated into the packages has been studied as a lowcost solution because the packages can be tested in normal FR4 printed circuit board (PCB) instead of the RF function integrated PCB, the eWLB integrated with molded antenna chip packages (called eWLB antenna in molded package) technology is introduced in this paper. The characterizations for assembly process challenges are evaluated and illustrate the process optimizations of equipment handling, antenna molded chip package fabrication, reconstitution process control and warpage characterization of the molded wafer. In addition, the radio frequency (RF) test validation is performed to verify the performance of scattering parameter (S-parameter), radiation pattern, impedance and detection range of the antenna. In order to prove the reliable quality and yield of the evaluated eWLB antenna in molded packages, package-level reliability tests are studied. Through these results, it will show that this eWLB antenna in molded package integration is a robust and costeffective solution for 77GHz automotive applications.

Optimal design of ultrasonic transducer based on multi-layer backing with adjustable impedance

Ultrasonic transducers, especially used in medical imaging, strike a balance between sensitivity and bandwidth to yield high-quality images. This challenge centers on the optimal transmission of acoustic energy across the layers of transducer. The backing layer stands as a critical component of transducers, orchestrating the conversion of acoustic impedance to enhance bandwidth. While traditional designs often utilize metal particle-polymer composites, issues arise from material limitations, complex fabrications, and deviations in sample properties. This study introduces an optimized multilayer backing (MLB) design using a metal-polymer structure. Implementing an equivalent circuit model, an MLB of epoxy-aluminum composite is designed. The ultrasonic transducer has an operating frequency of about 6 MHz, in which the backing layer is a stacking composite of 19.3 μm epoxy resin and 30 μm aluminum foil. Notably, this optimized design increased the -6dB bandwidth from 27.72 % to 33.44 % and verified its superior electro-acoustic performance based on ultrasonic imaging. Furthermore, this innovative design approach provides a wider range of acoustic impedance, improves the efficiency of ultrasonic energy transmission, and provides a streamlined approach to miniaturized transducer design.

Cross-Borehole ERT Monitoring System for CO2 Geological Storage: Laboratory Development and Validation

Cross-borehole electrical resistivity tomography (CHERT) technology has been implemented in field-scale CCS/CCUS (carbon capture and storage/carbon capture, utilization and storage) projects. It is highly desirable to investigate how to optimize the design of the ERT electrode arrays and corresponding working schemes for both laboratory experiments and field applications. A CHERT system was developed for laboratory experiments of CO2 geological storage applications. An optimization method was established for optimizing the structure of electrode arrays and corresponding working schemes. The developed CHERT system was calibrated systematically to determine the measurement range and accuracy of electrical impedance. Laboratory experiments were designed and implemented to validate the performance of the developed CHERT system. It has been illustrated that: (1) It is an essential step to optimize the structure of electrode arrays and corresponding working schemes of CHERT according to the real application background. The optimization method based on finite-element modelling provides an effective means for designing a field-scale CHERT system. (2) The quality of the images inverted from the CHERT data is highly dependent on the working schemes and specific modes, which is closely related to the size of the data sets used for the inversion. The AM-BN scheme is recommended due to the better uniformity of the resultant sensitivity field and application to larger borehole spacing. (3) Based on the calibration, the measurement range of the developed CHERT system can be determined as 100 Ω to 4.5 kΩ with an error limit of 1.5%. The maximum relative errors of the impedance magnitude and phase angle are 5.0% and 7.0%, respectively. Based on the test results the location of the CO2-bearing objects can be identified accurately. The shapes of the tested objects present distortion to some extent, but this can be alleviated by selecting working modes with a larger size of data set.

Dynamic Changes in Body Composition and Protein Intake in Epithelial Ovarian Cancer Patients Undergoing Chemotherapy: A Preliminary Study.

Ovarian cancer patients often face poor nutritional status, with body composition (BC) serving as a significant prognostic indicator. Skeletal muscle mass (SMM) and fat-free mass (FFM) are crucial predictors of both survival and hospitalization duration. Increasing protein intake has been linked to improvements in SMM and FFM. This study aimed to document the alterations in BC parameters among ovarian cancer patients undergoing chemotherapy and correlate these changes with their nutrient intake. Twelve female patients with stage III ovarian cancer who received first-line chemotherapy were categorized based on their body mass indices (BMI). BC parameters were assessed using an 8-point bioelectrical impedance analysis with a frequency of 50 Hz-60 Hz and measurement impedance range of 10 Ω-1000 Ω. Nutrient intake (energy, protein, fat, and carbohydrate) was assessed before (T0), during the 3rd (T3), and 6th cycle of chemotherapy (T6) through 24-hour food recall. Significant increases in body weight (BW)were observed in the underweight group (from 40.9 to 46.8 kg, p=0.001), concomitant with enhancements in all BC parameters. While changes were noted in SMM, they were not statistically significant (p=0.105).Among the underweight group, a protein intake above 1.2 g/kg BW led to an uptrend trend in SMM. Conversely, FFM in overweight/obese patients decreased significantly (from 37.6 to 36.4 kg, p=0.005) due to a a reduction in body water. Throughout chemotherapy, fat mass (FM), visceral fat (VAT), and phase angle (PhA) increased in all patient groups, reflecting heightened fat and carbohydrate intake. Among stage III ovarian cancer patients, BC undergoes dynamic changes dynamically during the course of chemotherapy, with more pronounced enhancements observed in FFM among underweight patients. Notably, improvements in PhA, SMM or FFM were particularly evident among underweight patients with a protein intake above 1.2 g/kg BW.

Relaxing Conservatism for Enhanced Impedance Range and Transparency in Haptic Interaction.

The Time Domain Passivity Approach (TDPA) has been accepted as one of least conservative tools for designing stabilizing controllers in haptics and teleoperation, but it still suffers from conservatism because it is based on passivity. Additionally, high-frequency, immediate control actions lead to a degradation of transparency. In this paper, we propose a method to relax the conservatism of haptic interaction and enhance stable impedance range while maintaining high transparency. Based on the observation of energy exchange behavior in pressing and releasing paths in haptic interaction, we introduce an energy cycle as a completion of a pressing and releasing path. With this new concept, we compare the energies at the end of each energy cycle to estimate the energy generation and inject adaptive damping to regulate it over upcoming cycles. Because we wait a pressing-releasing cycle is completed, we allow energy to be generated, but we regulate the amount of generated energy over upcoming cycles by injecting adaptive damping. In this way, we perform low-frequency control actions on system dynamics. These in turn enable us to achieve high transparency. We show the validity of the proposed approach through several simulations and experiments, and show that it enhances the stable impedance range and transparency compared to the TDPA.

4 MHz Electrosurgical Generator System for Wide Load Impedance Range With SiC-Based Full-Bridge Inverter

A power conversion system to drive a high-frequency electrosurgical generator (ESG) is proposed. The proposed system consists of a 4 MHz full-bridge (FB) inverter capable of ensuring power in a wide load impedance range and implementing energy control functions in accordance with the ESG characteristics. Unlike conventional inverter systems, ESG cannot deliver energy directly to the load, but through an instrument, which makes it difficult to ensure power. Thus, impedance matching is essential to ensure power in ESG. For ensuring power, impedance matching is realized using a resonance filter while considering instrument induced parasitic components that cannot be ignored at high frequencies. The inverter is composed of silicon carbide (SiC) suitable for the MHz switching operation. A prototype is to validate the proposed system. Experimental test of the prototype that it can provide a load power of more than 100 W for a tissue model with impedance range of 5-to-800 Ω.

Acoustic impedance measurement method using spherical waves

The mechanical properties and composition of materials can be better understood through ultrasonic non-destructive testing. Ultrasound is a valuable tool for characterizing elastic moduli, material microstructure, morphological conditions, and correlated acoustical/mechanical properties. Although ultrasound measurement techniques like transmission and pulse-echo are well-established, there is a growing demand for new technologies to facilitate automated inspection and enhance the widespread application of this method. This paper presents a novel approach to evaluate the characteristic acoustic impedance of a sample using measurements of reflected spherical waves. Employing a spherical sound source makes the energy distribution more uniform in all directions, minimizing measurement errors caused by system alignment. Additionally, that configuration aids in determining the experiment's geometry. The impedance was evaluated by analysis of the spherically reflected Gaussian-modulated sinusoidal pulses, which are less susceptible to noise interference. The acquired signal is fitted into a mathematical model to calculate the acoustic impedance, considering the decrease in sound pressure amplitude at the spherical wavefront according to the inverse distance law. Materials with a wide range of impedances (2 MRayl < Z < 46 MRayl) were measured to validate the method. The experimental impedances exhibited statistically significant agreement with values obtained via through-transmission impedance evaluation. The linear regression indicates a bias of 0.02 MRayls and an overall relative error of 1.7 % between the methods. This experimental setup holds promise for accurately assessing submerged structures, offering potential advantages for quantitative inspection.

Substrate‐integrated‐waveguide cavity‐backed circularly polarized antenna with enhanced bandwidth and gain

AbstractWe propose a method for increasing the bandwidth of a substrate‐integrated‐waveguide (SIW) cavity‐backed antenna with taper‐based microstrip SIW transition feeding. For radio transmission, a circular slot is etched on top of the SIW cavity. For optimal antenna design, the slot is etched slightly away from the cavity center to generate circularly polarized waves. Simulations show a wide axial ratio bandwidth of 7.860% between 11.02 GHz and 11.806 GHz. Experimental results confirm a similar wide axial ratio bandwidth of 4.9% between 10.8 GHz and 11.35 GHz. An SIW feed from an inductive window excites the radiating circular slot, resulting in a simulated wide impedance range of 1.548 GHz (10.338 GHz–11.886 GHz) and bandwidth of 13.93%. Experimental results show a wide impedance of 2.08 GHz (10.2 GHz–12.08 GHz) and bandwidth of 18.84%. The SIW cavity‐backed antenna creates a unidirectional pattern, leading to gains of 6.61 dBi and 7.594 dBi in simulations and experiments, respectively. The proposed antenna was fabricated on a Rogers RT/Duroid 5880 substrate, and the reflection coefficient, radiation patterns, and gains were tested and compared using a computer simulator. The developed broadband antenna seems suitable for X‐band applications.

Aveir Leadless Pacemaker implantation in pediatric population: a case series

Abstract Background While the Medtronic Micra pacemaker provided a small device for leadless pacemaker implantation, the Aveir device allows chronic retrievability and mapping prior to fixation. We present the first Aveir leadless pacemaker implantations in a pediatric population. Purpose To describe the first retrievable leadless pacemaker implants in children. Methods Retrospective review of pediatric Aveir implants occurred between November 2022 and December 2022. All patients were implanted via internal jugular vein insertion utilizing the Aveir sheath and catheter deployment system with mid-atrial approach taken prior to insertion of the catheter across the tricuspid valve. All patients had initial mapping of capture threshold, impedance and R-wave noted prior to deployment. Indications for pacing included sinus pauses and intermittent atrioventricular block. Results Three patients underwent Aveir leadless pacemaker implantation with weights of 32.3kg, 44kg, and 51kg. Capture thresholds were all 0.75Volts@0.2 milliseconds with impedance range of 370-1110 ohms, and R-waves of 8-14 millivolts (mV). Follow-up at 3 months ranged from 0.5V@0.2ms to 1V@0.2ms with impedances ranging 400-700 ohms, and R-wave 7-14 mV. At VVI 50-55bpm, with pacing ranged from 5% to 14%, predicted longevities ranged from 20 to 24.5 years at 3 months follow-up. Conclusion(s) Retrievable leadless pacemaker implantation is feasible in children and may offer good longevities for intermittent pacing need.Aveir Leadless Pacemaker in RVAveir Leadless Pacemaker in RV

GaN-Based 4-MHz Full-Bridge Electrosurgical Generator Using Zero-Voltage Switching Over Wide Load Impedance Range.

In this article, a 4-MHz full-bridge inverter system for an electrosurgical generator (ESG) is presented with zero-voltage switching (ZVS) turn-on over a wide load impedance range based on wideband gap material gallium nitride (GaN) technology. The proposed resonant circuit is used for impedance matching and limits the current when the load is short state while performing ZVS over a wide load impedance range. It also ensures high power performance at high frequencies for electric surgery. The implementation methods of the GaN switch at 4 MHz with high output performance are guided by the low inductance from the gate-driver output to the switch gate node and the effective heating management structure of the GaN-based inverter. The proposed generator achieved a maximum output power of 99 W to the load and a maximum overall efficiency of 89% with overcurrent of <3 A at short state of the load. The ESG can generate constant output power of 20, 50, 70 W through mode control of 2, 5, and 7 s. The overcurrent Moreover, the proposed generator is tested on porcine tissue samples to verify its effectiveness as an ESG.

Control of a lithium-ion battery interfacing input-voltage-controlled boost converter with virtual impedance compensation technique

Lithium-ion batteries are becoming increasingly popular for energy storage in various hybrid energy systems, hybrid ac/dc, micro-grid, e-mobility applications. However, due to the wide battery impedance range, the performance of lithium-ion battery interfacing dc-dc converter is affected, results in complicated task for design of this regulation. As the virtual impedance concept is increasingly used for the control of power electronic systems, this letter introduces virtual impedance into the Lithium-ion Battery interfacing boost converter controller, to reduce the impact of variable inner impedance. The proposed virtual-impedance based control structure, is derived with small-signal model of boost converter, and explained in detail in this letter. Finally, the performance of the strategy is verified on a lithium-ion battery pack equipped dc micro-grid.

Model reference adaptive controllers with improved performance for applications in LCL-filtered grid-connected converters

This work presents a control strategy combining a direct Model Reference Adaptive Control (MRAC) with a robust state feedback for current control of grid-connected converters with LCL filters operating under grid impedance variations. The MRAC is based on a gradient law, providing properly current reference tracking and voltage disturbance rejection. The inclusion of a state feedback inner loop provides robust active damping of the filter resonance for an entire range of grid impedances. A systematic control design procedure is proposed, and the combination of both control actions in a multi-loop approach does not add significant computational complexity. The proposal allows to increase the MRAC gains adaptation dynamics, providing suitable responses under grid current reference variations and under typical grid voltage disturbances, including grid faults. Performance indexes as the grid-currents total harmonic distortion and the mean squared error are also improved. In addition, robust stability analysis based on Lyapunov functions are carried out for the inner control loop and for the outer control loop, considering the grid impedance uncertain and with unmodeled dynamics. The strategy is implemented in a commercial digital signal processor, and the compliance of the grid currents with the IEEE 1547 Std. is verified with controller hardware-in-the-loop and experimental results in a 5.4 kW prototype.

Interlaboratory comparison of battery impedance analyzers calibration

The paper reports a results of series of interlaboratory comparisons of low impedance measurements at frequencies relevant for electrochemical impedance spectroscopy (EIS) of commercial lithium-ion cells. Two comparisons are presented. The first, bilateral comparison has focused on low impedance standards calibration in a full complex plane using digital sampling setups. The second comparison has focused on calibration and use of commercial 4-terminal battery EIS meters. Both comparisons have covered the impedance range from 50μ℧ to 100m℧ across the full complex plane in a frequency range from 0.01Hz up to 5kHz. Finally, the paper summarizes practices identified as critical for achieving measurement compatibility among various labs.

Power quality enhancement in islanded microgrids via closed-loop adaptive virtual impedance control

The high proportion of nonlinear and unbalanced loads results in power quality issues in islanded microgrids. This paper presents a novel control strategy for harmonic and unbalanced power allocation among distributed generators (DGs) in microgrids. Different from the existing sharing strategies that allocate the harmonic and unbalanced power according to the rated capacities of DGs, the proposed control strategy intends to shape the lowest output impedances of DGs to optimize the power quality of the microgrid. To achieve this goal, the feasible range of virtual impedance is analyzed in detail by eigenvalue analysis, and the findings suggest a simultaneous adjustment of real and imaginary parts of virtual impedance. Because virtual impedance is an open-loop control that imposes DG to the risk of overload, a new closed-loop structure is designed that uses residual capacity and absorbed power as feedback. Accordingly, virtual impedance can be safely adjusted in the feasible range until the power limit is reached. In addition, a fuzzy integral controller is adopted to improve the dynamics and convergence of the power distribution, and its performance is found to be superior to linear integral controllers. Finally, simulations and control hardware-in-the-loop experiments are conducted to verify the effectiveness and usefulness of the proposed control strategy.

Efficiency Improvement for Wireless Power Transfer System via a Nonlinear Resistance Matching Network

The primary control is widely adopted to obtain a constant voltage output under a wider load range. However, for traditional full-bridge inverters under phase-shift control, due to the loss of soft switching, the system transmission efficiency will decrease rapidly. This problem can be improved by using a half-bridge inverter; however, the power transferred to receiving devices utilizing a half-bridge inverter is inadequate under a small dc load value. To solve these urge issues, a resistance matching network (RMN), constructed by a resonant inductor and capacitor, is added before the full bridge rectifier part of this paper. Owing to the nonlinear resistance conversion characteristics of the proposed RMN structure, the variation range of the equivalent AC impedance before the rectifier end can be compressed into an optimum range to enhance the poor transmission efficiency during the coils part. Simultaneously, when the DC load is small, the power capability of the whole system can be enhanced by increasing the equivalent ac load value; as a result, the insufficient power capability of the half-bridge inverter can be relieved. Finally, a 36 V output WPT system based on the proposed RMN and phase shift control is constructed. Additionally, the experimental results prove the feasibility of the theoretical analysis results.