Tunable Impedance Research Articles

On Multi-Fidelity Impedance Tuning for Human-Robot Cooperative Manipulation

Abstract We examine how a human-robot interaction (HRI) system may be designed when input output data from previous experiments are available. Our objective is to learn an optimal impedance in the assistance design for a cooperative manipulation task with a new operator. Due to the variability between individuals, the design parameters that best suit one operator of the robot may not be the best parameters for another one. However, by incorporating historical data using a linear auto-regressive (AR-1) Gaussian process, the search for a new operator's optimal parameters can be accelerated. We lay out a framework for optimizing the human-robot cooperative manipulation that only requires input-output data. We characterize the learning performance using a notion called regret, establish how the AR-1 model improves the bound on the regret, and numerically illustrate this improvement in the context of a human-robot cooperative manipulation task. Further, we show how our approach's input-output nature provides robustness against modeling error through an additional numerical study.

Ultra-wideband high gain low group delay variation amplifier for phased-array radar system

This paper describes a ultra-wideband (UWB) three-stage cascaded high gain amplifier with low group delay variation for phased-array radar system. The shunt inductor at the input not only provides an electrostatic discharge (ESD) path to ground, but also introduces a new notch for S11, thus extending the matching bandwidth. Staggered tuning of load impedance peaks at each stage facilitates a balance between flat gain and low group delay variation. The output stage further enhances the overall gain while reinforcing bandwidth and stability through resistive feedback, and employs an adaptive bias circuit for linearity improvement. Implemented in SMIC 40-nm CMOS technology, the proposed amplifier achieves good input impedance matching, flat gain and low group delay variation of ±73.5 ps over 4.7–16 GHz. The whole power consumption is 198.3 mW and the output 1 dB compression point (OP1dB) is greater than 9 dBm. After careful design, the chip size is 0.64 mm2.

Compact AFSIW Antenna With Integrated Digitally Controlled Impedance Tuner for Smart Surfaces

Compact AFSIW Antenna With Integrated Digitally Controlled Impedance Tuner for Smart Surfaces

Resonant Impedance Tuners: Theory, Design, Power Handling, and Repeatability

Resonant Impedance Tuners: Theory, Design, Power Handling, and Repeatability

Tunable Impedance of Cobalt Loaded Carbon for Wide-Range Electromagnetic Wave Absorption.

Impedance matching modulation of the electromagnetic wave (EMW) absorbers toward broad effective absorption bandwidth (EAB) is the ultimate aim in EMW attenuation applications. Here, a Joule heating strategy is reported for preparation of the Co-loaded carbon (Co/C) absorber with tunable impedance characteristics. Typically, the size of the Co can be regulated to range from single-atoms to clusters, and to nanocrystals. The varied sizes of the Co combined with different graphitization degrees of carbon can result in different relative input impedances and electromagnetic loss, leading to the tunable EMW absorption properties of the Co/C absorber. By meticulously coalescing the different prepared Co/C, the working frequency can be easily tuned, covering Ku, X, and C bands. Furthermore, the Co/C demonstrates a high EMW attenuation due to its unique dielectric loss capability and magnetic loss characteristics. The abundant interfaces of Co/C can also contribute to the enhanced interfacial polarization for improving EMW attenuation. This work demonstrates the importance of optimizing the metal and carbon interaction to the impedance matching toward wide EAB of the EMW absorbers.

On-Chip Integration of a Plasmonic FET Source and a Nano-Patch Antenna for Efficient Terahertz Wave Radiation.

Graphene-based Field-Effect Transistors (FETs) integrated with microstrip patch antennas offer a promising approach for terahertz signal radiation. In this study, a dual-stage simulation methodology is employed to comprehensively investigate the device's performance. The initial stage, executed in MATLAB, delves into charge transport dynamics within a FET under asymmetric boundary conditions, employing hydrodynamic equations for electron transport in the graphene channel. Electromagnetic field interactions are modeled via Finite-Difference Time-Domain (FDTD) techniques. The second stage, conducted in COMSOL Multiphysics, focuses on the microstrip patch antenna's radiative characteristics. Notably, analysis of the S11 curve reveals minimal reflections at the FET's resonant frequency of 1.34672 THz, indicating efficient impedance matching. Examination of the radiation pattern demonstrates the antenna's favorable directional properties. This research underscores the potential of graphene-based FETs for terahertz applications, offering tunable impedance matching and high radiation efficiency for future terahertz devices.

Tunable Dual-Band High-Impedance Coil for Wireless Power Transfer Applications

Tunable Dual-Band High-Impedance Coil for Wireless Power Transfer Applications

A Parameter Recognition-Based Impedance Tuning Method for SS-Compensated Wireless Power Transfer Systems

A Parameter Recognition-Based Impedance Tuning Method for SS-Compensated Wireless Power Transfer Systems

Fiber metal laminates for high strain rate applications with layerwise shock impedance tuning

Novel materials such as fiber-metal laminates (FMLs) have demonstrated significant potential in a variety of applications. They must contend with problems such fatigue, creep, high-speed projectile impact, and deformation at high strain rates while in use. When employed as structural materials in aircraft, especially when exposed to shock wave impact and high velocity impact, fiber-metal laminates’ high strain rate characteristics become crucial. Shock impedance matching is a revolutionary approach used for shock-tuning the separate layers. The novelty of the current work is in developing custom shielding laminates, with in-depth analysis on the response of the shock impedance tuning of individual layers on the laminate behaviour at high strain rates. In the current study, five stackups of FMLs comprising metallic (AA 6061-T6) and fiber-reinforced polymer (FRP) plies, were formulated, incorporating shock impedance matching. The fiber-polymer plies used in the FMLs include ultra-high molecular weight polyethylene (UHMWPE), p-aramid for supplementing the impact resistance. Transmission loss functions (TL) estimated from the impedance tube experiments were used to indicate the shock tuning of the various laminates. The laminates underwent testing using a Split Hopkinson Pressure Bar (SHPB) apparatus to determine their properties at high strain rates (350, textrm{s}^{-1} to 460, textrm{s}^{-1}). The variation in the Shock Energy (SE) absorbed by the laminates at various strain rates was analyzed as a function of the corresponding Transmission Loss employing regression. The dynamic stress-strain curves showed an increase in shock energy absorption at higher strain rates. The sequence SSP-IV and SSP-II showed the highest values of energy absorption as well as Transmission Loss.

A novel compact and tunable positive and negative impedance simulator and multiplier

SummaryThis paper presents a novel CMOS tunable positive and negative active inductor simulator (AIS), positive capacitance and resistance multiplier, and negative capacitance and resistance simulator. The proposed designs use only one analog building block (ABB), one grounded capacitor, and two resistors. Applications to the proposed designs in different types of tunable filters and parasitic compensation schemes are also presented. The functionality of the designs is confirmed using Tanner Tspice in 0.18 μm TSMC CMOS technology. Simulation results indicate that the proposed designs are superior to previous arts in number of ABB, number of functions, and power consumptions.

A new broadband cross-dipole CP antenna with modified square-cavity reflector

ABSTRACTA new broadband cross-dipole CP antenna with modified square-cavity reflector is proposed in this work. The cross-dipole CP antenna is composed of four rotated L-shaped patches, a pair of vacant-quarter feeding loops as sequential-phase feeding network, two modified trapezoid-microstrip lines as impedance tuner, and a square-cavity reflector with four parasitic strips. Different from the traditional vacant-quarter rings, the modified vacant-quarter loops with trapezoid-microstrip lines are utilized to increase the impedance bandwidth (IBW) and provide 90° phase difference. First, the rotated L-shaped patches are used to obtain wide CP operation. Second, a square-cavity reflector is utilized for enhancing the radiation gains. Moreover, four parasitic strips are inserted into the reflector to increase the CP bandwidth. Therefore, multiple CP resonant points could be stimulated simultaneously by fully utilizing these elements, resulting in a wide CP performance. Finally, the proposed cross-dipole CP antenna has a wider −10 dB IBW of 100% (1.0–3.0, 2.0 GHz), broader 3-dB ARBW of 71.2% (1.25–2.65, 1.95 GHz), and a higher radiation gain, which can cover the WiBro (2.3–2.39 GHz) and GPS (L1 1.575 GHz) bands.

An open-end high-power microwave-induced fracturing system for hard rock

Microwave pre-treatment is considered as a promising technique for alleviating cutter wear. This paper introduces a high-power microwave-induced fracturing system for hard rock. The test system consists of a high-power microwave subsystem (100 kW), a true triaxial testing machine, a dynamic monitoring subsystem, and an electromagnetic shielding subsystem. It can realize rapid microwave-induced fracturing, intelligent tuning of impedance, dynamic feedback under strong microwave fields, and active control of microwave parameters by addressing the following issues: the instability and insecurity of the system, the discharge breakdown between coaxial lines during high-power microwave output, and a lack of feedback of rock-microwave response. In this study, microwave-induced surface and borehole fracturing tests under true triaxial stress were carried out. Experimental comparisons imply that high-power microwave irradiation can reduce the fracturing time of hard rock and that the fracture range (160 mm) of a 915-MHz microwave source is about three times that of 2.45 GHz. After microwave-induced borehole fracturing, many tensile cracks occur on the rock surface and in the borehole: the maximum reduction of the P-wave velocity is 12.8%. The test results show that a high-power microwave source of 915 MHz is more conducive to assisting mechanical rock breaking and destressing. The system can promote the development of microwave-assisted rock breaking equipment.

A Compact Broad Circularly Polarized Cross-Dipole Antenna with Grounded Parasitic Elements

A new wideband cross-dipole antenna (CDA) with a circularly polarized (CP) characteristic is proposed in this article. The antenna consists of four L-shaped patches, two modified trapezoid-microstrip lines as an impedance tuner, a pair of vacant-quarter feeding loops as a continuous-phase feeding network, and four grounded inverted L-shaped strips as parasitic elements. It is noticed that the grounded inverted L-shaped strips are inserted directly below the L-shaped patches to increase the CP bandwidth and enhance the gains of the antenna, which is different from the conventional parasitic elements. First, a pair of vacant-quarter feeding loops is used as a feeding structure to provide a sequential phase characteristic. Second, four L-shaped patches as driven elements are connected to the feeding structure to excite two CP resonant modes. Third, two modified trapezoid-microstrip lines are inserted into the feeding structure to adjust the impedance match. Moreover, four grounded inverted L-shaped strips are introduced into the square reflector to achieve wider CP operation by utilizing a gap capacitive coupling feeding way. Finally, the proposed antenna is simulated, manufactured, and measured to verify the design rationality. The measured results indicate the proposed antenna has a broad 3-dB ARBW of 82.5% (1.38–3.32 GHz, 2.35 GHz) and a wide −10-dB IBW of 81.2% (1.18–3.04 GHz, 2.29 GHz). Furthermore, the measured and simulated CP bandwidths are 75.1% (1.38–3.04 GHz, 2.21 GHz) and 74.7% (1.36–2.98 GHz, 2.17 GHz), which is suitable for CP applications in WiBro (2.3–2.39 GHz) and GPS (L1 1.575 GHz) bands.

Enhanced low-frequency microwave absorption of N-doped biomass derived carbon

Hierarchical porous undoped and N-doped carbon derived from the natural spinach roots was prepared by a facile carbonization process at 600–800 ℃ respectively. The electromagnetic properties were carefully investigated in the range of 1–18 GHz in order to study the effect of the tunable permittivity on the microwave absorbing and shielding performance by modulating the intrinsic polarization of the biomass carbon. Compared with the other samples, the undoped one sintered at 650 ℃ shows the minimum reflection loss (RL) of − 42.93 dB at 16.72 GHz with a thickness of 2.0 mm, while the effective absorbing bandwidth achieves 6.46 GHz at 2.4 mm. With the N-doping, the permittivity is obviously affected by the nitrogen-containing groups and compounds induced dipolar and interfacial polarization. The RLmin of the N-doped carbon sample sintered at 700 ℃ has arrived at − 49.96 dB at 15.88 GHz with a very thin thickness of 1.5 mm. Besides, the impedance matching bandwidth can cover the L-C band in the N-doped carbon with the excellent RL of − 43.195 dB at d= 8.4 mm and f= 2.4 GHz. The competitive and tunable mechanism of the dielectric property are also studied for the tunable impedance and microwave absorption.

Ultra‐wideband frequency selective surface based tightly coupled dipole array with integrated balun

AbstractAn ultra‐wideband and wide‐scan tightly coupled dipoles array based on frequency selective surface (FSS) is proposed, and the traditional wide‐angle scan impedance matching dielectric layer is replaced by FSS with printed metal strips to achieve the tuning of the scanning impedance of the array. Additionally, the metal strip FSS, dipole radiating elements and feeding structure are all printed on the same printed circuit board, and the whole design is highly integrated. Finally, a low‐cost lightweight single‐polarization tightly coupled antenna array with ultra‐wide band and wide scan performance is presented. Subject to the criterion of active Voltage standing Wave ratio(VSWR) < 3, beam scanning coverage of ±45° along E plane, H plane and D plane can be accomplished within the frequency band range across 0.4–2 GHz. An array prototype was produced and tested, and the results showed that the effectiveness of the design was well validated.

Effect of fluorine doping on the performance of multi−heteroatom doped carbons (F,N,B−C or F,N,S−C) for microwave absorption

Heteroatom-doped porous carbon materials offer great promise as microwave absorbers. However, template−free methods for synthesizing porous carbon materials rich in heteroatoms (N,F,B and S), necessary for tuning impedance matching and optimizing attenuation losses, need to be dicovered. In this article, we report the successful preparation of porous fluorine−doped multi−heteroatom carbons (F,N,B−C and F,N,S−C) by the high−temperature pyrolysis of polypyrrole-based precursors. The introduction of the heteroatoms created defective carbon structures with high microwave absorption ability. In particular, the F,N,S−C absorber offered an excellent loss capacity, including the RLmin of − 38.0 dB at 13.2 GHz (2.5 mm thickness) and the EAB of 6.3 GHz from 11.7 − 18 GHz (2.0 mm thickness) using a filler amount of only 9.0 wt%. The outstanding microwave absorption properties are the result of the interactions between incoming microwaves and carbon defects/pores, which together provide a moderate conductive loss, good polarization relaxation (interfacial polarization and defect/dipole polarization) as well as scattering of microwaves via reflection.

Resonant Measurement of Coaxial Probe Based on Tunable Impedance Matching Network

In this work, we first present a tunable impedance matching network (IMN) to produce an outstanding resonance for improving the sensitivity of coaxial probes. A two-port network based on a three-line coupled (TLC) structure along with a tunable phase shifter is designed to realize conjugate matching. The calculated shape factor for characterizing the sharpness of resonance can be up to 1.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{5}$</tex-math> </inline-formula> when deionized (DI) water is loaded. The minimum measurable concentration level of ethanol is 0.005 mole fraction. The conventional probe’s sensitivity is enhanced to be comparable with those achieved by other resonance-based sensing methods. Using calibration liquids, the complex permittivity of a liquid can be extracted.

Data-Driven Variable Impedance Control of a Powered Knee-Ankle Prosthesis for Adaptive Speed and Incline Walking.

Most impedance-based walking controllers for powered knee-ankle prostheses use a finite state machine with dozens of user-specific parameters that require manual tuning by technical experts. These parameters are only appropriate near the task (e.g., walking speed and incline) at which they were tuned, necessitating many different parameter sets for variable-task walking. In contrast, this paper presents a data-driven, phase-based controller for variable-task walking that uses continuously-variable impedance control during stance and kinematic control during swing to enable biomimetic locomotion. After generating a data-driven model of variable joint impedance with convex optimization, we implement a novel task-invariant phase variable and real-time estimates of speed and incline to enable autonomous task adaptation. Experiments with above-knee amputee participants (N=2) show that our data-driven controller 1) features highly-linear phase estimates and accurate task estimates, 2) produces biomimetic kinematic and kinetic trends as task varies, leading to low errors relative to able-bodied references, and 3) produces biomimetic joint work and cadence trends as task varies. We show that the presented controller meets and often exceeds the performance of a benchmark finite state machine controller for our two participants, without requiring manual impedance tuning.

Mitigation of grid parameter uncertainties for the steady-state operation of a model-based voltage controller in distribution systems

This paper deals with the impact of line impedances uncertainties on model-based voltage controllers for distribution networks in the context of secondary to tertiary control levels (i.e., 30 min control horizon). The study proposes two methodologies: (i) centralized and (ii) distributed approaches, to estimate grid impedances by relying on static historical measurement data and adjust the parameters of a model-based voltage controller. Furthermore, an online impedance tuning scheme is proposed to successively fine-tune the impedance estimation over successive control periods (along several days). The simulations results highlight the preciseness of the proposed methodologies, with both centralized and distributed able to estimate the grid impedances within an acceptable accuracy (between 4% and 7% of error). Moreover, the proposed tuning algorithm shows to be very effective, where the estimation error can be lowered under 1%. Finally, robustness studies are performed to test the proposed methodologies in the presence of measurement noises. Through this study, the robustness of the proposed tuning scheme can be validated, in which the algorithm is able to correct massive impedance errors after three months of tuning rounds only.

Hierarchical Optimization for Control of Robotic Knee Prostheses Toward Improved Symmetry of Propulsive Impulse.

Automatically personalizing complex control of robotic prostheses to improve gait performance, such as gait symmetry, is challenging. Recently, human-in-the-loop (HIL) optimization and reinforcement learning (RL) have shown promise in achieving optimized control of wearable robots for each individual user. However, HIL optimization methods lack scalability for high-dimensional space, while RL has mostly focused on optimizing robot kinematic performance. Thus, we propose a novel hierarchical framework to personalize robotic knee prosthesis control and improve overall gait performance. Specifically, in this study the framework was implemented to simultaneously design target knee kinematics and tune 12 impedance control parameters for improved symmetry of propulsive impulse in walking. In our proposed framework, HIL optimization is used to identify an optimal target knee kinematics with respect to symmetry improvement, while RL is leveraged to yield an optimal policy for tuning impedance parameters in high-dimensional space to match the kinematics target. The proposed framework was validated on human subjects, walking with robotic knee prosthesis. The results showed that our design successfully shaped the target knee kinematics as well as configured 12 impedance control parameters to improve propulsive impulse symmetry of the human users. The knee kinematics that yielded best propulsion symmetry did not preserve the normative knee kinematics profile observed in non-disabled individuals, suggesting that restoration of normative joint biomechanics in walking does not necessarily optimize the gait performance of human-prosthesis systems. This new framework for prosthesis control personalization may be extended to other wearable devices or different gait performance optimization goals in the future.