Active Impedance Research Articles

An Active Virtual Impedance Control Algorithm for Collision Free Navigation of a Mobile a Robot

<span style="color: black; font-family: 'Times New Roman','serif'; font-size: 9pt; mso-fareast-font-family: '맑은 고딕'; mso-bidi-font-style: italic; mso-fareast-theme-font: minor-fareast; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">An modified active virtual impedance control has been proposed for collision free navigation of a mobile robot to avoid front obstacles dynamically while a mobile robot is following a sound source. A mobile robot is controlled to follow a sound source with a velocity which is determined by virtual repulsive and attraction forces to avoid obstacles and to follow the sound source, respectively. To generate the virtual repulsive and attraction forces, a new modified virtual impedance is defined as a function of the distances and relative velocities to the sound source and obstacles from the mobile robot. In the conventional virtual impedance method, fixed coefficients have been used for the virtual impedance control. In this research, the coefficients are dynamically adjusted to elaborate the obstacle avoidance performance in various situations such as the multiple moving obstacles environment. A microphone array consisting of three microphones in a row has been attached on the mobile robot to detect the relative distance and velocity to the obstacles. The relative position and orientation of the sound source against the mobile robot has been estimated using the geometrical relationship of the microphones. As an application, the mobile robot can be used as a pet robot following the master with a sound source. The effectiveness of the proposed algorithm has been demonstrated through real experiments.</span>

Design of a Phased Array in Triangular Grid With an Efficient Matching Network and Reduced Mutual Coupling for Wide-Angle Scanning

In this paper, a wide-scan angle planar patch phased array is proposed. The proposed array is composed of wideband probe-fed microstrip patches placed $0.087\lambda _{h} (\lambda _{h}$ is the wavelength of highest frequency) above individual ground planes and interlaced with parasitic decoupling walls. In order to cancel the feed probe inductance, the array elements comprise additional degrees of freedom to introduce controllable capacitance. Concurrently, individual ground planes and parasitic decoupling walls are proposed as an effective structure to considerably increase the E-plane scanning angle of the phased array by reducing the magnitude of near-field mutual coupling. A 544-element phased array prototype of the proposed element was designed, manufactured, and validated experimentally. The experimental results agree well with the numerical simulation ones and indicate effectiveness of the proposed design for mutual coupling reduction and wide-angle scanning. Because of the modifications, the measured mutual coupling between adjacent elements is reduced to lower than −32 dB at the center frequency. The proposed phased array has almost a constant active input impedance (active VSWR less than 2 over 20% bandwidth) up to scan angle of 65° in E-plane and 60° in H-plane, with a realized gain reduction of about 3.5 dB.

Equivalent Transmission Line Models for the Analysis of Edge Effects in Finite Connected and Tightly Coupled Arrays

In this paper, we present an analysis of the edge effects in wideband connected arrays of slots and dipoles. Due to the strong mutual coupling between the elements, these arrays can support the propagation of guided waves along their surface. Such waves arise from the edges of the finite array and can be especially detrimental to the performance, since they can travel within the array without geometrical spreading. In this paper, we introduce Green’s function-based equivalent transmission line models to describe the propagation of the guided waves. The elements’ active impedances are represented as periodic loads on these transmission lines. The equivalent models can be used as a simple and convenient tool to control and minimize the edge effects. Finite array simulations of relevant array structures are discussed. The evidence is that the active impedance and the interelement capacitance can be tuned to attenuate and reflect the edge-born waves.

High performance and durability of order-structured cathode catalyst layer based on TiO2@PANI core-shell nanowire arrays

In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO2@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO2@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54mWcm−2) than conventional PEMFC (699.30mWcm−2). Electrochemically active surface area (ECSA) and charge transfer impedance (Rct) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO2@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order-structured membrane electrode with lower Pt loading for PEMFC in the future.

Electrically Small, Broadside Radiating Huygens Source Antenna Augmented With Internal Non-Foster Elements to Increase Its Bandwidth

A broadside radiating, linearly polarized, electrically small Huygens source antenna system that has a large impedance bandwidth is reported. The bandwidth performance is facilitated by embedding non-Foster components into the near-field resonant parasitic elements of this metamaterial-inspired antenna. High-quality and stable radiation performance characteristics are achieved over the entire operational bandwidth. When the ideal non-Foster components are introduced, the simulated impedance bandwidth witnesses approximately a 17-fold enhancement over the passive case. Within this –10-dB bandwidth, its maximum realized gain, radiation efficiency, and front-to-back ratio (FTBR) are, respectively, 4.00 dB, 88%, and 26.95 dB. When the anticipated actual negative impedance convertor circuits are incorporated, the impedance bandwidth still sustains more than a 10-fold enhancement. The peak realized gain, radiation efficiency, and FTBR values are, respectively, 3.74 dB, 80%, and 28.01 dB, which are very comparable to the ideal values.

Ag–Ni core–shell nanowires with superior electrocatalytic activity for alkaline hydrogen evolution reaction

Ag–Ni nanowires with high electrochemically active surface area and small impedances were synthesized to show enhanced alkaline HER activity.

A comprehensive review of on-board State-of-Available-Power prediction techniques for lithium-ion batteries in electric vehicles

Abstract This study provides an overview of available techniques for on-board State-of-Available-Power (SoAP) prediction of lithium-ion batteries (LIBs) in electric vehicles. Different approaches dealing with the on-board estimation of battery State-of-Charge (SoC) or State-of-Health (SoH) have been extensively discussed in various researches in the past. However, the topic of SoAP prediction has not been explored comprehensively yet. The prediction of the maximum power that can be applied to the battery by discharging or charging it during acceleration, regenerative braking and gradient climbing is definitely one of the most challenging tasks of battery management systems. In large lithium-ion battery packs because of many factors, such as temperature distribution, cell-to-cell deviations regarding the actual battery impedance or capacity either in initial or aged state, the use of efficient and reliable methods for battery state estimation is required. The available battery power is limited by the safe operating area (SOA), where SOA is defined by battery temperature, current, voltage and SoC. Accurate SoAP prediction allows the energy management system to regulate the power flow of the vehicle more precisely and optimize battery performance and improve its lifetime accordingly. To this end, scientific and technical literature sources are studied and available approaches are reviewed.

The Fault Level Reduction in Distribution System Using an Active Type SFCL

The electricity generation from many small resources is becoming one of the major systems in distribution generation systems to feed electrical loads. The effect of fault current and induced over voltages under abnormal conditions must be taken into account seriously. The effect of fault current can be limited by applying an active type superconducting fault current limiter (SFCL), the active SFCL is composed of an air-core superconducting transformer and a PWM converter. The magnetic field in the air-core can be controlled by adjusting the converters output current, and then the active SFCLs equivalent impedance can be regulated for current limitation and possible overvoltage suppression. During the study process, in view of the changes in the locations of the DG units connected to the system, the DG units injection capacities and the fault positions, the active SFCLs current-limiting and overvoltage suppressing characteristics are both simulated in MATLAB. The simulation results show that the active SFCL can play an important role in restraining the fault current and overvoltage, and it can contribute to avoiding damage on the relevant distribution equipment and improve the systems safety and reliability. Index Terms- Distribution Generation, power quality (PQ), Active type SFCL.

Transverse beam feedback systems in the U-70 synchrotron

A method for analyzing the transverse beam feedback circuit in a ring accelerator and selecting its parameters using the concept of the active beam coupling impedance, which is externally imposed and controlled, is described. This approach is used for the physical substantiation of approaches to upgrading two operational transverse feedback systems that are available in the U-70 synchrotron of the Institute for High Energy Physics, National Research Centre Kurchatov Institute: narrow-band analog and broadband digital systems. Both systems were subjected to deep upgrading, which is based on this method, and were successfully commissioned in 2007 and 2011, respectively. A brief description of their updated engineering implementation is given. The presented experimental results confirm the adequacy of the impedance approach to designing and adjusting the transverse beam feedback circuits in the U-70 synchrotron.

Electrochemical analysis of template-free DNA synthesis: Lowering pH and the active component of the impedance spectrum

The process of template-free DNA synthesis was detected in two ways: by measuring the pH of the solution by a semiconductor sensor and by measuring the conductivity in the recording of impedance spectra. Synthesis was carried out without using template DNA, with only two enzymes being involved in the reaction: DNA polymerase and nicking endonuclease (nickase) in the presence of deoxynucleotide triphosphates. Previously, Purushothaman et al., by applying the recording of the results of template-directed synthesis with a pH-sensitive field-effect transistor, showed that protons are released into solution in the incorporation of nucleotides [4]. Regarding this, it was important to establish that the same release of protons into solution occurred in the template-free synthesis as in the template-directed synthesis and to identify the changes by measuring the conductivity of the solution using impedance spectra. It was found that the template-free synthesis was accompanied by the generation of protons (ΔpH is ~1.5 pH at an initial concentration of deoxynucleotide triphosphates of 150 µM) and a decrease in the value of active impedance component by ~25% of the initial value. The effect of a decrease in the active impedance component was explained as being due to an increasing conductivity of medium due to a growth in the concentration of protons.

An efficient power harvesting mobile phone-based electrochemical biosensor for point-of-care health monitoring

Cellular phone penetration has grown continually over the past two decades with the number of connected devices rapidly approaching the total world population. Leveraging the worldwide ubiquity and connectivity of these devices, we developed a mobile phone-based electrochemical biosensor platform for point-of-care (POC) diagnostics and wellness tracking. The platform consists of an inexpensive electronic module (<$20) containing a low-power potentiostat that interfaces with and efficiently harvests power from a wide variety of phones through the audio jack. Active impedance matching improves the harvesting efficiency to 79%. Excluding loses from supply rectification and regulation, the module consumes 6.9mW peak power and can measure <1nA bidirectional current. The prototype was shown to operate within the available power budget set by mobile devices and produce data that matches well with that of an expensive laboratory grade instrument. We demonstrate that the platform can be used to track the concentration of secretory leukocyte protease inhibitor (SLPI), a biomarker for monitoring lung infections in cystic fibrosis patients, in its physiological range via an electrochemical sandwich assay on disposable screen-printed electrodes with a 1nM limit of detection.

An efficient multipaction suppression method in microwave components for space application**Project supported by the National Natural Science Foundation of China (Grant No. U1537211), the National Key Laboratory Key Foundation, China (Grant No. 9140C530101150C53011), and China Postdoctoral Science Foundation (Grant No. 2015M572661XB).

Multipaction, caused by the secondary electron emission phenomenon, has been a challenge in space applications due to the resulting degradation of system performance as well as the reduction in the service life of high power components. In this paper we report a novel approach to realize an effective increase in the multipaction threshold by employing micro-porous surfaces. Two micro-porous structures, i.e., a regular micro-porous array fabricated by photolithography pattern processing and an irregular micro-porous array fabricated by a direct chemical etching technique, are proposed for suppressing the secondary electron yield (SEY) and multipaction in components, and the benefits are validated both theoretically and experimentally. These surface processing technologies are compatible with the metal plating process, and offer substantial flexibility and accuracy in topology design. The suppression effect is quantified for the first time through the proper fitting of the surface morphology and the corresponding secondary emission properties. Insertion losses when using these structures decrease dramatically compared with regular millimeter-scale structures on high power dielectric windows. SEY tests on samples show that the maximum yield of Ag-plated samples is reduced from 2.17 to 1.58 for directly chemical etched samples. Multipaction testing of actual C-band impedance transformers shows that the discharge thresholds of the processed components increase from 2100 W to 5500 W for photolithography pattern processing and 7200 W for direct chemical etching, respectively. Insertion losses increase from 0.13 dB to only 0.15 dB for both surface treatments in the transmission band. The experimental results agree well with the simulation results, which offers great potential in the quantitative anti-multipaction design of high power microwave components for space applications.

Simulation of an interturn fault in a stator winding of a synchronous condenser

A method of simulation of interturn faults in a stator winding in steady state operating conditions of synchronous condenser is proposed. The method is based on a mathematical model with the equations of the mesh current method for phase-to-phase voltages. Expressions for active and reactive impedances of the windings are presented. The initial data for calculation of resistance and reactance of stator and rotor windings are obtained experimentally. Experiments proved that the proposed method simulates interturn faults in a stator winding with a maximum error of 5–10%.

COMPARATIVE STUDY BETWEEN DIFFERENT METHODS USED IN PROTECTION BY DISTANCE OF ELECTRICAL NETWORKS

Distance relays (D.R) are used in protection of electrical networks to measure the apparent impedance of the fault and shall compare it with its D.R setting impedance, but the apparent impedance may be differ from the actual impedance due to the network challenges appeared such as effect of branched networks, series capacitor for compensation, power swing, parallel transmission lines and fault resistance. All of these challenges will result to overreach or underreach errors, accordingly false trip. Some of approach methods shall be introduced in this paper to overcome these errors. In the recent transmission line (T.L) systems, more than one of these challenges can appear simultaneously. It shall be difficult to adjust the D.R with value suitable for all challenges. In this paper, the study how D.R will overcome each challenge alone and how it will be adjusted with value suitable for all of these challenges together shall be considered.

A Compact, Modular Series Elastic Actuator

This paper presents the development of a compact, modular rotary series elastic actuator (SEA) design that can be customized to meet the requirements of a wide range of applications. The concept incorporates flat brushless motors and planetary gearheads instead of expensive harmonic drives and a flat torsional spring design to create a lightweight, low-volume, easily reconfigurable, and relatively high-performance modular SEA for use in active impedance controlled devices. The key innovations include a Hall effect sensor for direct spring displacement measurements that mitigate the negative impact of backlash on SEA control performance. Both torque and impedance controllers are developed and evaluated using a 1-degree-of-freedom (DoF) prototype of the proposed actuator package. The results demonstrate the performance of a stable first-order impedance controller tested over a range of target impedances. Finally, the flexibility of the modular SEA is demonstrated by configuring it for use in five different actuator specifications designed for use in the uBot-7 mobile manipulator requiring spring stiffnesses from 3 N · m/deg to 11.25 N · m/deg and peak torque outputs from 12 N · m to 45 N · m.

Design and Implementation of a New PWM Based Active Impedance Power Factor Correction (AIPFC)

Design and Implementation of a New PWM Based Active Impedance Power Factor Correction (AIPFC)

Impact Analysis of DSSC on Distance Relay Performance under Fault Conditions

This paper demonstrates the impact analysis of the Distributed Static Series Compensator (DSSC), on the performance of distance relay protection of high voltage transmission lines. The concept of DSSC model with its control circuit and distance relay are described. A five bus test system with DSSC and distance relay is designed with the help of MATLAB/SIMULINK software. The impact of DSSC on distance protection relay for different fault conditions and various fault locations is analyzed. The results of simulation show that the connection of DSSC in the transmission system changes the transmission line impedance greatly as estimated by the distance relay to be less or greater than the actual impedance in fault conditions. Hence, the distance relay performance changes, either over reaches or under reaches.

Impedance Threshold Device Combined With High-Quality Cardiopulmonary Resuscitation Improves Survival With Favorable Neurological Function After Witnessed Out-of-Hospital Cardiac Arrest

The quality of cardiopulmonary resuscitation (CPR) has been recently shown to affect clinical outcome. The Resuscitation Outcomes Consortium (ROC) Prehospital Resuscitation Impedance Valve and Early Versus Delayed Analysis (PRIMED) trial showed no differences in outcomes with an active vs. sham impedance threshold device (ITD), a CPR adjunct that enhances circulation. It was hypothesized the active ITD would improve survival with favorable neurological outcomes in witnessed out-of-hospital cardiac arrest patients when used with high-quality CPR. Using the publicly accessible ROC PRIMED database, a post-hoc analysis was performed on all witnessed subjects with both compression rate and depth data (n=1,808) who received CPR within the study protocol definition of adequate CPR quality (compression rate 80-120/min and depth 4-6 cm; n=929). Demographics were similar between sham and active ITD groups. In witnessed subjects who received quality CPR, survival with favorable neurological function was 11.9% for the active ITD subjects (56/470) vs. 7.4% for the sham (34/459) (odds ratio 1.69 [95% confidence interval 1.08, 2.64]). There were no statistically significant differences for this primary outcome when CPR was performed outside the boundaries of the definition of adequate CPR quality. Multivariable models did not change these associations. An active ITD combined with adequate-quality conventional CPR has the potential to significantly improve survival after witnessed cardiac arrest. (Circ J 2016; 80: 2124-2132).

Wide-Angle Scanning Phased Array Using an Efficient Decoupling Network

The active impedance of each element in a phased array changes substantially with scan angle due to mutual coupling. Therefore, a key challenge in the design of wide-angle scanning phased array is to achieve wide-angle impedance matching (WAIM). In this communication, an efficient decoupling network is developed to reduce the mutual coupling between adjacent elements for this purpose. A complete scattering matrix analysis of the decoupling network is given and the design procedure is summarized. A ${1} \times {16}$ linear microstrip phased array has been designed and fabricated for experimental verification. Good agreement is obtained between measured and simulated results. The measured mutual coupling between adjacent elements is reduced to lower than $- {35}\; \text{dB}$ at the center frequency. Due to the reduced mutual coupling, the array can experimentally scan to 66° with a gain reduction of only 3.04 dB.

Active inductor-based tunable impedance matching network for RF power amplifier application

This paper presents the use of a new structure of active inductor named cascoded flipped-active inductor (CASFAI) in a T-type high-pass tunable output matching network of a class-E RF power amplifier (RFPA) to control the output power and enhance the efficiency. The designed CASFAI behaves as an inductor in the frequency range of 0–6.9GHz, and has reached to a maximum quality factor of 4406, inductance value of 7.56nH, 3rd order harmonic distortion better than −30dB for 0dBm input power, while consumes only 2mW power. In order to consider the performance of the proposed active inductor-based tunable output matching network on the output power level and power added efficiency (PAE) of RFPA, the CASFAI is applied as a variable inductor to the output matching network of RFPA. The overall circuit is designed and validated in ADS in a 0.18µm CMOS process and 1.5V supply voltage. The results indicate that by increasing the inductance value of the matching network in constant operating frequency, the PAE peak moves from high power to low power levels without any degradation. Therefore, it is possible to maintain the power efficiency at the same maximum level for lower input drive levels.