Current Noise Measurements Research Articles

Augmented nonsmooth observer for sensorless permanent magnet synchronous motor drives with harmonic suppression

To enhance the performance of the permanent magnet synchronous motor (PMSM) sensorless drive, an augmented nonsmooth observer (ANSO) combined with the modified quadrature phase-locked loop (Q-PLL) is constructed in this article. Different from the extensively utilized sliding mode observer with discontinuous switching terms in sensorless control, the proposed ANSO with continuous nonsmooth terms possesses the ability to eliminate the chattering phenomenon. In addition, the novel ANSO can acquire desirable current measurement noise suppression characteristic by exploiting augmented observer technique. After acquiring the estimated back electromotive force (EMF) signal from the ANSO, a concise and effective adaptive notch filter (ANF) is adopted to improve the conventional Q-PLL to suppress the undesirable speed fluctuation caused by inverter nonlinearities and flux spatial harmonics. Comparative experimental results validate the advantageous behavior of the presented sensorless control scheme.

Current-driven mechanical motion of double stranded DNA results in structural instabilities and chiral-induced-spin-selectivity of electron transport.

Chiral-induced-spin-selectivity of electron transport and its interplay with DNA's mechanical motion are explored in a double stranded DNA helix with spin-orbit-coupling. The mechanical degree of freedom is treated as a stochastic classical variable experiencing fluctuations and dissipation induced by the environment as well as force exerted by nonequilibrium, current-carrying electrons. Electronic degrees of freedom are described quantum mechanically using nonequilibrium Green's functions. Nonequilibrium Green's functions are computed along the trajectory for the classical variable taking into account dynamical, velocity dependent corrections. This mixed quantum-classical approach enables calculations of time-dependent spin-resolved currents. We showed that the electronic force may significantly modify the classical potential, which, at sufficient voltage, creates a bistable potential with a considerable effect on electronic transport. The DNA's mechanical motion has a profound effect on spin transport; it results in chiral-induced spin selectivity, increasing spin polarization of the current by 9% and also resulting in temperature-dependent current voltage characteristics. We demonstrate that the current noise measurement provides an accessible experimental means to monitor the emergence of mechanical instability in DNA motion. The spin resolved current noise also provides important dynamical information about the interplay between vibrational and spin degrees of freedom in DNA.

Kalman filtering based on dynamic perception of measurement noise

In this work, we focus on the online state estimation problem for linear systems in non-Gaussian measurement noise. Specifically, the measurement noise is modeled as a Gaussian mixture model (GMM). Then, Kalman innovation is used to approximate the current measurement noise, and dynamically perceive its responsiveness to each sub-model of the GMM. The responsiveness from different Gaussian scales is mapped to a new cost function, while the corresponding Kalman filter algorithm is derived. The theoretical steady-state error and computational complexity analysis of the algorithm are also given. The simulation and real experimental results agree with the theoretical predictions and demonstrate the superior performance of the proposed algorithm.

Analysis of the Effect of Switching Frequency on Acoustic Noise in External Rotor Brushless DC Motors

Electric motors are actively used in various industries. Acoustic noise is crucial in electric motors, and specific standards are depending on their application areas. Despite better performance, including acoustic noise, than brushed motors, brushless motors still generate acoustic noise due to their mechanical, electrical, and electronic components. This study investigated the impact of varying the switching frequency through the driver on the acoustic noise of an external rotor brushless DC motor. Tests were conducted on a surface-mounted magnet brushless motor with different switching frequencies, and detailed information about the sections of the control board governing the brushless motor was provided. The study includes measurements of motor speed, current, switching frequency, phase signal, and acoustic noise measured at two different locations in decibels. It was observed that the acoustic noise increased at specific switching frequencies. Furthermore, the variation in switching frequency also affected the heating due to losses in the switching elements. Increasing the switching frequency in the 12-28 kHz range reduced motor speed and the measured acoustic noise, while temperature increases were observed in various frequency ranges.

Switching Techniques for Minimizing Current Measurement Noise in Integrated Single Shunt Power Conversion System With Common DC Link

Switching Techniques for Minimizing Current Measurement Noise in Integrated Single Shunt Power Conversion System With Common DC Link

Parameter Identification of Permanent Magnet Synchronous Motor with Dynamic Forgetting Factor Based on H∞ Filtering Algorithm

To address system parameter changes during permanent magnet synchronous motor (PMSM) operation, an H∞ filtering algorithm with a dynamic forgetting factor is proposed for online identification of motor resistance and inductance. First, a standard linear discrete PMSM parameter identification model is established; then, the discrete H∞ filtering algorithm is derived using game theory reducing state and measurement noise influence. A cost function is defined, solving extremes values of different terms. A dynamic forgetting factor is introduced to the weighted combination of initial and current measurement noise covariance matrices, eliminating identification issues from different initial values. On this basis, a dynamic forgetting factor is added to weigh the combination of the initial measurement noise covariance matrix and the current measurement noise covariance matrix, which eliminates the influence of the discrimination error caused by the different initial values. Finally, the identification model is built in MATLAB/Simulink for simulation analysis to verify the feasibility of the proposed algorithm. The simulation results show the proposed H∞ filtering algorithm rapidly and accurately identifies resistance and inductance values with significantly improved robustness. The forgetting factor enables quick stable recognition even with poor initial values, enhancing PMSM control performance.

An improved initial rotor position estimation method using high-frequency pulsating voltage injection for PMSM

High frequency pulsating voltage injection method is a good candidate for detecting the initial rotor position of permanent magnet synchronous motor. However, traditional methods require a large number of filters, which leads to the deterioration of system stability and dynamic performance. In order to solve these problems, a new signal demodulation method is proposed in this paper. The proposed new method can directly obtain the amplitude of high-frequency current, thus eliminating the use of filters, improving system stability and dynamic performance and saving the work of adjusting filter parameters. In addition, a new magnetic polarity detection method is proposed, which is robust to current measurement noise. Finally, experiments verify the effectiveness of the method.

State of health estimation of the LiFePO4 power battery based on the forgetting factor recursive Total Least Squares and the temperature correction

The decline of the lithium-ion power battery's State of Health (SOH) with usage significantly impacts other state estimation results, such as State of Charge (SOC). Hence, accurate estimation of the lithium-ion power battery's SOH holds vital importance in the battery management system. This paper proposes a SOH estimation method for the lithium-ion power battery, utilizing the Forgetting Factor Recursive Total Least Squares (FFRTLS) and incorporating the temperature correction. The FFRTLS effectively addresses the SOC estimation errors and the terminal current measurement noise simultaneously. The temperature correction method, based on the Arrhenius equation, corrects the influence of the ambient temperature during the SOH estimation process, ensuring that the ambient temperature does not affect the accuracy of the SOH estimation results. Additionally, the capacity convergence coefficient enhances the reliability of the SOH estimation results by preventing abrupt changes of the maximum available capacity. Experimental results on a LiFePO4 power battery under diverse working conditions and varying ambient temperatures, validate the effectiveness of the proposed method. The evaluation indexes, including Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Maximum Absolute Error (Max-AE), demonstrate the high accuracy of the SOH estimation results, with all indexes below 0.21%, 0.25% and 0.35% respectively.

Chloroquine-analogues block anthrax protective antigen channels in steady-state and kinetic studies

The tripartite anthrax toxin from Bacillus anthracis represents the prototype of A-B type of toxins, where the effector A (an enzymatic subunit) is transported with the help of a binding component B into a target cell. Anthrax toxin consists of three different molecules, two effectors, lethal factor (LF) and edema factor (EF) and the binding component also known as protective antigen (PA). PA forms heptamers or octamers following binding to host cell’s receptors and mediates the translocation of the effectors into the cytosol via the endosomal pathway. The cation-selective PA63-channel is able to reconstitute in lipid membranes and can be blocked by chloroquine and other heterocyclic compounds. This suggests that the PA63-channel contains a binding site for quinolines. In this study, we investigated the structure-function relationship of different quinolines for the block of the PA63-channel. The affinity of the different chloroquine analogues to the PA63-channel as provided by the equilibrium dissociation constant was measured using titrations. Some quinolines had a much higher affinity to the PA63-channel than chloroquine itself. We also performed ligand-induced current noise measurements using fast Fourier transformation to get insight in the kinetics of the binding of some quinolines to the PA63-channel. The on-rate constants of ligand binding were around 108 M−1·s−1 at 150 mM KCl and were only little dependent on the individual quinoline. The off-rates varied between 4 s−1 and 160 s−1 and depended much more on the structure of the molecules than the on-rate constants. The possible use of the 4-aminoquinolines as a therapy is discussed.

Encoderless Control of PMa-SynRG Based-Stator Current Vector for Wind Generation Systems

In this paper, a novel encoderless control of permanent magnet assisted synchronous reluctance generator (PMa-SynRG) based-stator current vector for renewable energy systems is presented. For the encoderless control, the PMa-SynRG rotor position angle along with rotor angular speed are estimated ultimately from the generator's stator currents, as the stator inductance is only requisite nevertheless the stator resistance. Indeed, this encoderless control technique employs one current control loop for regulating the magnitude of the stator current instead of employing two current control loops. For eliminating the current measurement noise and enhancing the phase angle tracking performance, a modified second-order generalized integrator frequency-locked loop (MSOGI-FLL) technique is employed and compared with the standard SOGI-FLL under different voltage/frequency conditions. The proposed technique has a simple computational implementation while accomplishing a rapid along with precise estimation performance of the PMa-SynRG rotor position angle and speed. The performance is validated using simulations and real-time hardware-in-the-loop Typhoon HIL implementation.

Analysis of Position Estimation Error in Signal-Injection Sensorless Control Induced by Inverter dv/dt-Based Current Measurement Noise

This article discusses position estimation error in signal-injection sensorless control (SISC) induced by the current measurement noise of closed-loop Hall effect current sensor, when it is installed in an inverter system. For the first step, an equivalent circuit modeling of the current sensor in the inverter system is proposed, which includes the parasitic capacitances between the inverter and sensor. The presented modeling can explain how the high dv/dt of the inverter switching generates the leakage current through the parasitic capacitances, resulting in the measurement noise. The noise is sampled with analog to digital conversion, and it affects the rotor position estimation signal with the SISC algorithm. As a result, it is revealed that considerable position estimation error occurs from the noise. The experimental results are provided to verify the proposed theory and confirm the noise effects on the SISC performance.

Entanglement of Nambu Spinors and Bell Inequality Test without Beam Splitters.

The identification of electronic entanglement in solids remains elusive so far, which is owed to the difficulty of implementing spinor-selective beam splitters with tunable polarization direction. Here, we propose to overcome this obstacle by producing and detecting a particular type of entanglement encoded in the Nambu spinor or electron-hole components of quasiparticles excited in quantum Hall edge states. Because of the opposite charge of electrons and holes, the detection of the Nambu spinor translates into a charge-current measurement, which eliminates the need for beam splitters and assures a high detection rate. Conveniently, the spinor correlation function at fixed effective polarizations derives from a single current-noise measurement, with the polarization directions of the detector easily adjusted by coupling the edge states to a voltage gate and a superconductor, both having been realized in experiments. We show that the violation of Bell inequality occurs in a large parameter region. Our Letter opens a new route for probing quasiparticle entanglement in solid-state physics exempt from traditional beam splitters.

DC and low-frequency noise characteristics of GaN-based HEMTs under cryogenic temperatures

In this work, the device characteristics of GaN-based high-electron-mobility transistors (HEMTs) were systematically investigated by the direct current (DC) and low-frequency noise (LFN) measurements within the temperature ranging from 300 K to 4.2 K. The temperature-dependent behavior of the on- and off-state electrical properties was statistically analyzed, highlighting an overall improved device performance under cryogenic temperatures. In addition, the LFN of the device exhibited an evident behavior of 1/f noise from 10 Hz to 10 kHz in the measured temperature range and can be well described by the carrier number fluctuations with correlated mobility fluctuations (CNF/CMF) model down to 4.2 K. Based on this model, we further extracted and discussed the defect-related behavior in the devices under low-temperature environments. These experimental results provide insights into the device characteristics of GaN-based HEMTs under cryogenic environments, motivating further studies into the GaN-based cryo-devices and systems.

The Noise Level in Residential Areas Bordering Jagorawi Highway

Noise pollution has not become a priority in environmental issues, but the potential negative impact on society based on studies can be in the form of physical and psychological disturbances, the main cause of noise in the urban area is transportation. Identification of noise sources needs should be done to ensure that the sound produced accordance with environmental characteristics. The Jagorawi toll road is the 3rd density toll road in the Jabodetabek area, compared to several other toll roads. Jagorawi toll road is bordered by residential areas. In the Cibubur-Cimanggis sector, this toll road is directly adjacent to residential areas with a distance of < 20 meters and some points do not have barriers to reduce noise. The Cibubur-Cimanggis sector is currently developing with the addition of the LRT, which will operate in 2022 so that current noise measurements can be used as baseline data at the study site. This noise monitoring is intended to conclude whether or not there is an effect of noise felt by the surrounding community from activities on the Jagorawi toll road and to obtain a reduction in noise levels using a single barrier with a height of 0.5, 1, 1.5 and 2 m. Noise monitoring is carried out using SNI 8421:2017 for 24 hours at 2 measurement points in residential areas. Point one and point two each have a noise value (Lsm) of 68.87 and 61.29 dBA with a correlation value of 0.605 (medium). The noise value has exceeded the quality standard for residential designation based on the Minister of Environment Decree No. 48 of 1996 (55 dBA), so a barrier is needed to reduce the noise received by the community. The analysis of the use of the barrier studied is a single barrier with G = 1. As the result of adding a barrier at point 1 with high 2 m, the noise value can be reduced by 16.7 dBA with a p-value of 0.00, so the addition of a barrier has a significant impact on the noise value. This study found the effect of noise from the Jagorawi toll road up to a distance of 114 m at a point that does not use a barrier, so the role of the barrier along the toll road is very important. With the use of a barrier, the distance required to reduce single noise originating from the toll road to < 55 dBA is 20 m.

An improved test methodology for detecting one-case latent damage in inverter circuit under ESD pulses

Latent damage in IC chips with packaging is becoming one of the major concerns for industry nowadays. In this work, a transmission line pulse (TLP) method is used to analyze the lower ESD pulses that can cause one-case latent damage rather than hard failure in the chip. A new voltage distribution strategy for one of the pins of a packaged IC is proposed to reflect the latent damage caused by ESD stress. The impact of the latent damage can be evaluated through leakage current and low frequency noise (LFN) measurements. It is observed that LFN is more sensitive for detecting the latent damage than leakage current when the IC pin is subjected to a lower TLP voltage. Experimental results show that LFN density changes dramatically when the number of ESD pulses and TLP voltage increases. Therefore, using TLP plus LFN measurement provides a more sensitive test methodology for detecting latent damage of IC chip under ESD pulses. For future ICs design, it is possible to predict the latent damage of ICs and screen out low quality and poor reliability ICs based on this improved test methodology.

Homemade-HEMT-based transimpedance amplifier for high-resolution shot-noise measurements.

We report a cryogenic transimpedance amplifier (TA) suitable for cross-correlation current-noise measurements. The TA comprises homemade high-electron-mobility transistors with high transconductance and low noise characteristics, fabricated in an AlGaAs/GaAs heterostructure. The low input-referred noise and wide frequency band of the TA lead to a high resolution in current-noise measurements. The TA's low input impedance suppresses unwanted crosstalk between two distinct currents from a sample, justifying the advantage of the TA for cross-correlation measurements. We demonstrate the high resolution of a TA-based experimental setup by measuring the shot noise generated at a quantum pointcontact in a quantum Hall system.

Different glutamate sources and endogenous co-agonists activate extrasynaptic NMDA receptors on amacrine cells of the rod pathway microcircuit.

The NMDA receptors (NMDARs) expressed by AII and A17 amacrine cells, the two main inhibitory interneurons of the rod pathway microcircuit in the mammalian retina, are exclusively extrasynaptic, activated by ambient levels of glutamate, and molecularly distinct, with AII and A17 amacrines expressing GluN2B- and GluN2A-containing receptors, respectively. This important sensory microcircuit thus provides a unique model to study the activation and function of extrasynaptic NMDARs. Here, we investigated the sources of glutamate and the endogenous co-agonists (d-serine or glycine) that activate these distinct populations of NMDARs. With acute slices from rat retina, we used whole-cell voltage-clamp recording and measurement of current noise to monitor levels of NMDAR activity. Pre-incubation of retina with bafilomycin A1 (an inhibitor of neurotransmitter uptake into synaptic vesicles) abolished NMDAR-mediated noise in AII, but not A17 amacrines, suggesting a vesicular source of glutamate activates AII NMDARs, whereas a non-vesicular source activates A17 NMDARs. Pre-incubation of retina with l-methionine sulfoximine (an inhibitor of glutamine synthetase) also abolished NMDAR-mediated noise in AII, but not A17 amacrines, suggesting a neuronal source of glutamate activates AII NMDARs, whereas a glial source activates A17 NMDARs. Enzymatic breakdown of d-serine reduced NMDAR-mediated noise in AII, but not A17 amacrines, suggesting d-serine is the endogenous co-agonist at AII, but not A17 NMDARs. Our results reveal unique characteristics of these two populations of extrasynaptic NMDARs. The differential and independent activation of these receptors is likely to provide specific contributions to the signal processing and plasticity of the cellular components of the rod pathway microcircuit.

A millikelvin scanning tunneling microscope in ultra-high vacuum with adiabatic demagnetization refrigeration.

We present the design and performance of an ultra-high vacuum scanning tunneling microscope (STM) that uses adiabatic demagnetization of electron magnetic moments for controlling its operating temperature ranging between 30 mK and 1K with an accuracy of up to 7 μK rms. At the same time, high magnetic fields of up to 8T can be applied perpendicular to the sample surface. The time available for STM experiments at 50 mK is longer than 20 h, at 100 mK about 40 h. The single-shot adiabatic demagnetization refrigerator can be regenerated automatically within 7 h while keeping the STM temperature below 5K. The whole setup is located in a vibrationally isolated, electromagnetically shielded laboratory with no mechanical pumping lines penetrating its isolation walls. The 1K pot of the adiabatic demagnetization refrigeration cryostat can be operated silently for more than 20 days in a single-shot mode using a custom-built high-capacity cryopump. A high degree of vibrational decoupling together with the use of a specially designed minimalistic STM head provides outstanding mechanical stability, demonstrated by the tunneling current noise, STM imaging, and scanning tunneling spectroscopy measurements, all performed on an atomically clean Al(100) surface.

Noise Analysis of the Leakage Current in Time-Dependent Dielectric Breakdown in a GaN SLCFET

We report a novel noise analysis for the leakage current during time-dependent dielectric degradation under bias stress, illustrated using AlGaN/GaN superlattice castellated field-effect transistors (SLCFETs). Gate step stress is a standard approach to test the robustness of the gate dielectric in OFF-state conditions. Here, by removing the background step transients measured using a standard parameter analyzer, the algorithm gives a quantitative value for the nonstationary superimposed noise in the dielectric leakage current during the test. Extraction of the power spectrum using windowing and a direct fit to the noise statistical distribution gives the noise magnitude. Although the technique allows the monitoring of noise increase during stress, it is shown that this is insufficient to clearly identify irreversible degradation in these devices. An additional low bias noise test between each step-stress bias has been used to detect the onset of permanent localized breakdown. This is manifested as both a change in noise magnitude and frequency dependence, occurring before it can be seen in leakage current or direct noise measurements.

Cryogenic GaAs high-electron-mobility-transistor amplifier for current noise measurements.

We show that a cryogenic amplifier composed of a homemade GaAs high-electron-mobility transistor (HEMT) is suitable for current-noise measurements in a mesoscopic device at dilution-refrigerator temperatures. The lower noise characteristics of our homemade HEMT lead to a lower noise floor in the experimental setup and enable more efficient current-noise measurement than is available with a commercial HEMT. We present the dc transport properties of the HEMT and the gain and noise characteristics of the amplifier. With the amplifier employed for current-noise measurements in a quantum point contact, we demonstrate the high resolution of the measurement setup by comparing it with that of the conventional one using a commercial HEMT.