Flux Control Research Articles

Implementation of sensorless indirect vector control of induction motor with closed-loop current control

Abstract The paper focuses on the development and testing of an advanced induction motor control method. This method, known as indirect rotor flux-oriented vector control, allows independent control of motor torque and flux, providing high dynamic performance similar to that of a DC motor. Additionally, the implemented system is sensorless, eliminating physical rotor position sensors, which reduces complexity and cost while increasing system reliability. The proposed system uses a rotor flux estimation algorithm, based on mathematical models, which provides the necessary information for vector orientation in the absence of a sensor. Additionally, closed-loop current control improves stability and accuracy of the control by correcting output current deviations from reference values. Thus, the system provides fast and accurate response in the presence of load variations and external disturbances. Simulations and experimental tests were carried out in the Simulink environment, where the proposed model was evaluated under various operating conditions. The results demonstrate the efficiency of the system and the validity of the method for industrial applications where precise and robust induction motor control is required.

Sensitivities in protein allocation models reveal distribution of metabolic capacity and flux control.

Expanding on constraint-based metabolic models, protein allocation models (PAMs) enhance flux predictions by accounting for protein resource allocation in cellular metabolism. Yet, to this date, there are no dedicated methods for analyzing and understanding the growth-limiting factors in simulated phenotypes in PAMs. Here, we introduce a systematic framework for identifying the most sensitive enzyme concentrations (sEnz) in PAMs. The framework exploits the primal and dual formulations of these models to derive sensitivity coefficients based on relations between variables, constraints, and the objective function. This approach enhances our understanding of the growth-limiting factors of metabolic phenotypes under specific environmental or genetic conditions. Compared to other traditional methods for calculating sensitivities, sEnz requires substantially less computation time and facilitates more intuitive comparison and analysis of sensitivities. The sensitivities calculated by sEnz cover enzymes, reactions and protein sectors, enabling a holistic overview of the factors influencing metabolism. When applied to an Escherichia coli PAM, sEnz revealed major pathways and enzymes driving overflow metabolism. Overall, sEnz offers a computational efficient framework for understanding PAM predictions and unravelling the factors governing a particular metabolic phenotype. sEnz is implemented in the modular toolbox for the generation and analysis of PAMs in Python (PAModelpy; v.0.0.3.3), available on Pypi (https://pypi.org/project/PAModelpy/). The source code together with all other python scripts and notebooks are available on GitHub (https://github.com/iAMB-RWTH-Aachen/PAModelpy). Supplementary data are available at Bioinformatics online.

Effect of Standard versus Advanced Dimmable Lighting Systems on the Circadian Rhythms of Hospital Personnel

ABSTRACT The health of shift workers is seriously compromised due to circadian rhythm disruption. Not only do these shift workers lack sufficient exposure to natural light, the main circadian rhythm synchronizer, but they are also exposed to static electric lighting environments with the same luminous flux intensity throughout the entire night. Advances in lighting design make the accurate control of flux and spectra of electric lighting possible, allowing settings to be optimized for the appropriate regulation of circadian rhythms while also ensuring task performance. This research aims to quantify the effect of advanced lighting systems on the biological clock of nurses working night shifts in intensive care units, by replacing the fluorescent fixtures with dimmable luminaires. Diurnal and nocturnal levels of the main urine metabolite of melatonin, 6-sulfatoximelatonin, were assayed and a perception test of sleep quality and work performance was also carried out. The results show that the use of LED dimmable lighting results in an improvement in melatonin and cortisol levels of night shift workers, as well as improved concentration and sleep quality.

Light-Induced Nanobody-Mediated Targeted Protein Degradation for Metabolic Flux Control.

In metabolic engineering, increasing chemical production usually involves manipulating the expression levels of key enzymes. However, limited synthetic tools exist for modulating enzyme activity beyond the transcription level. Inspired by natural post-translational mechanisms, we present targeted enzyme degradation mediated by optically controlled nanobodies. We applied this method to a branched biosynthetic pathway, deoxyviolacein, and observed enhanced product specificity and yield. We then extend the biosynthesis pathway to violacein and show how simultaneous degradation of two target enzymes can further shift production profiles. Through the redirection of metabolic flux, we demonstrate how targeted enzyme degradation can be used to minimize unwanted intermediates and boost the formation of desired products.

Quality control of eddy covariance fluxes of two ecosystem types with local flux-variance similarity functions in West Africa

Ecosystem capacity studies for carbon sequestration and water extraction are largely conditioned by Eddy Covariance (EC) measurement availability and quality. Our study aims at evaluating several procedures of EC data qualification. Indeed, quality control of EC data is generally ensured by stationarity and well-developed turbulence tests. The latter is based on integral turbulence characteristic (ITC) models. In this study, we revisited the quality control procedure using locally established ITC models for wind speed components and atmospheric scalars (temperature, humidity and carbon dioxide molar densities) in unstable and stable conditions. We also considered the interdependence of flux qualities because of the corrections applied to fluxes during their preprocessing. The analyses were carried out using one year of data collected above a woodland forest and mixed crop sites, both situated in Northern Benin, West Africa. From these analyzes we note that the quality flags vary depending on the use of local or existing ITC models. Also, the test of turbulence development on atmospheric scalars, previously neglected, is of great importance in the quality control of data. Thus, taking into account the ITC models associated with the atmospheric scalars established locally in the well-developed turbulence test as well as taking into account the interdependence of the flux quality have considerably improved the standard quality control procedure used in effectively filtering unrealistic flux data while keeping a considerable percentage of good and medium quality data.

Deciphering Regulatory Role of Melatonin in Foliar Nastic Movements of Portulaca oleracea: Visual Insights from Histology and Anatomy

AbstractPlant nastic movements exhibit unique behavioural patterns that synchronize with external cues. Given that the foliar nastic motions of Portulaca species are solely circadian, it is intriguing to investigate whether and how melatonin governs these movements. Analysis of histological traits concurrent with anatomical traits such as stomatal behaviour provides visual data on the plant species' gnosophysiology, offering clues and validation of the influence of multiple external stimuli on hydraulic forces that in turn alter turgor pressure. The current study aims to elucidate how exogenous melatonin modulates foliar nastic movements in Portulaca oleracea. Our findings indicate that melatonin functions as an intracellular hydraulic flux controller, influencing idioblast and crystal densities, as well as stomatal behaviour. Timepoint studies at specific Zeitgebers reveal that abiotic variables such as light and temperature can influence the endogenous melatonin concentration of P. oleracea. Therefore, this hormone potentially serves as an additional internal regulator of turgor pressure, influenced by both light and temperature. Thus, melatonin plays a crucial role in shaping the characteristic foliar nastic movements observed in P. oleracea, inherently tied to the circadian rhythm. Further investigation into idioblast and crystal torques, along with their angular momentum, is warranted to calculate the hydraulic forces at work in the leaf lamina. Thus the study underscores the multifaceted role of melatonin in navigating nastic movement processes through turgor pressure alterations brought about by intracellular depositions. The study in future could unravel melatonin's pleiotropic actions and the underlying mechanisms of foliar idiosyncratic nastic motions in other plant species as well. Moreover, both histology and anatomy play vital roles in the present study as it has provided visual evidence of the underlying mechanisms of foliar nastic movements in P. oleracea. Graphical Abstract

Comparative study of the two DTC (6S - 12S) approaches applied to PMSM equipped with an IP regulator

Direct torque control was introduced in 1980 for induction machine for torque and flux control and developed for MSAP in 1990. DTC is gaining popularity due to its simple control structure and easy implementation. The principle of direct torque control (DTC) of the asynchronous machine was introduced in 1985 by I. Takahashi as an alternative to flux-directed vector control (FOC). It is thanks to its simple control structure that it gains popularity and its easy implementation that it has opened a new horizon in the field of variable speed control of electric drives. Indeed, direct torque control (DTC) has benefited in recent years from significant methodological advances in operation and technological development following the introduction of power electronics and digital electronics and the implementation of possible and very usable control algorithms. In conjunction with these technological advances, the scientific community has developed several control approaches to control the operation of electrical machines. In this context, this article presents a comparative study of the different direct torque control (DTC) strategies and structures of the permanent magnet synchronous machine (MSAP). We propose the algorithm of this control making it possible to provide solutions to the ripples of the torque and the stator flux in order to reduce them by adopting a method of compensating the effects of progression by passing from the six sector DTC (DTC – 6S: classic and modified) then develop the twelve-sector DTC (DTC-12S) whose purpose is to minimize ripples and control the switching frequency of the inverter. The simulation graphs presented will clearly show the difference between the different controls techniques cited.

Grey wolf optimization for enhanced performance in wind power system with dual-star induction generators

This study investigates strategies for enhancing the performance of dual-star induction generators in wind power systems by optimizing the full control algorithm. The control mechanisms involved include the PID (Proportional-Integral-Derivative) controller for speed regulation and the PI (Proportional-Integral) controller for flux, DC-link voltage, and grid connection control. The primary objective is to optimize the entire system by fine-tuning PID and PI controllers through the application of meta-heuristic algorithms, specifically Grey Wolf Optimization (GWO) and Particle Swarm Optimization (PSO). These algorithms play a crucial role in estimating the optimal values of Kp, Ki, and Kd for the PID speed controller, as well as Kp and Ki for the PI controller used in the flux, DC-link voltage, and grid connection for wind energy conversion system based dual-star induction generator. This comprehensive optimization ensures accurate parameter tuning for optimal system performance. A comparative analysis of the optimization results has been conducted, focusing on the outcomes obtained with the GWO algorithm. The findings reveal a notable reduction in steady-state error, signifying improved stability, and an overall enhancement in the wind power system’s performance. This study contributes valuable insights into the effective application of meta-heuristic algorithms for optimizing dual-star induction generators in wind power systems.

Analysis and optimization of dynamic and static thermal rectification in shell-and-tube phase change thermal rectifiers

Thermal rectification devices based on solid-liquid phase change material (PCM) can realize efficient and reversible control of forward and reverse heat flux. In this study, an analytical solution for a shell-and-tube phase change thermal rectifier is derived based on Fourier's law of heat conduction. The validity of the analytical model is confirmed by the numerical model verified by the exact solution of the single-phase Stefan problem. The influence of thermophysical properties, structural parameters, and initial temperature on the dynamic and static thermal rectification effects of the shell-and-tube heterojunction composed of polydimethylsiloxane (PDMS) and hexadecane (C16) is investigated and optimized. Results indicate that the proposed analytical model for the shell-and-tube phase change thermal rectifier enables rapid and precise prediction of thermal rectification effects. The presence of solid-liquid phases of C16 under forward and reverse heat transfer modes reduced the thermal resistance difference, resulting in poor initial rectification performance (only about 1.17). The optimized thermal rectification effect is significantly increased to 1.56, which is significantly improved by 33.56 %. Moreover, the dynamic rectification effect of the shell-and-tube thermal rectifier is notably higher than the static rectification effect. The average dynamic thermal rectification ratio within the first 50 s before and after optimization is 2.19 and 7.80, respectively, which is several times higher than the static thermal rectification ratio. This paper further analyzes the impact of initial temperature and finds that an increase in initial temperature can further enhance the dynamic thermal rectification effect. Raising the initial temperature to 5 K above the phase change temperature can increase the improvement of the dynamic rectification effect to 256.36 % in the first 50 s. The significance of this study lies in its potential to advance the understanding and practical application of thermal rectification based on PCM.

Topological features of trajectories of virtual photons and their effective interaction under multiple scattering in a system of conductive nanoparticles

It is shown that in conditions of strong light localization in a system of Rayleigh's resonance scatterers, effective photon–photon interaction appears. This interaction is associated with neither nonlinearity of medium nor nonlocal interaction of polarization-entangled photon pairs. It is related to complex topology of photon trajectories due to multiple scattering. Because of this interaction, acts of simultaneous elastic scattering of pair of photons in the considered system cease to be independent processes. The differential cross section of this cooperative process contains only an extra degree of small Rayleigh's factor in comparison with the classical scattering cross section of a single photon. This opens up the possibility of control of light fluxes by means of alternative low-intensity light fluxes without using slow optoelectronic converters. Light localization that provides the effective photon–photon interaction is considered in the framework of a new formalism different from traditional one. Equation of the Bethe–Salpeter for two-photon propagator is resolved directly in coordinate representation without traditional reducing of this equation to some transport equation. This allows in a new light to look on reason of weak light localization and to show that weak localization is one of consequences of strong localization.

Transition metals and oxidation reactions trigger stargate opening during the initial stages of the replicative cycle of the giant Tupanvirus.

Tupanviruses, members of the family Mimiviridae, infect phagocytic cells. Particle uncoating begins inside the phagosome, with capsid opening via the stargate. The mechanism through which this opening takes place is unknown. Once phagocytized, metal ion flux control and ROS are induced to inactivate foreign particles, including viruses. Here, we studied the effect of iron ions, copper ions, and H2O2 on Tupanvirus particles. Such treatments induced stargate opening in vitro, as observed by different microscopy techniques. Metal-treated viruses were found to be non-infectious, leading to the hypothesis that stargate opening likely resulted in the release of the viral seed, which is required for infection initiation. To the best of our knowledge, this is the first description of a giant virus capsid morphological change induced by transition metals and H2O2, which may be important to describe new virulence factors and capsid uncoating mechanisms.

Torque dynamic performance enhancement of five‐phase permanent magnet synchronous motor with open‐circuit fault

AbstractMultiphase permanent magnet synchronous motors (PMSMs) have attracted much more attention for their high efficiency, low torque ripple and good fault tolerance. However, open‐circuit fault results in asymmetrical motor behaviour, and deteriorates torque performance, especially dynamic response. This paper proposes a novel fault‐tolerant direct torque and flux control (DTFC) strategy to restrain fluctuating torque and enhance torque dynamic performance of a five‐phase PMSM with open‐circuit fault. The novelty of the proposed strategy is the development of DTFC based on stator flux orientation under the open‐circuit fault condition and the third harmonic current suppression with carrier‐based pulse width modulation technology. Consequently, the decoupling control of torque and stator flux can be achieved under the open‐circuit fault condition, and the third harmonic current can be restrained without additional control. Combined with deadbeat control, the heavy computation burden can be reduced. Thus, the proposed strategy not only can enhance torque dynamic performance under open‐circuit fault operation, but also keep smooth torque with circular stator flux trajectory before and after open‐circuit fault. The effectiveness of the proposed strategy is verified by the simulation and experimental results.

2D PIC modeling of the helical scrape-off layer current driven by hybrid divertor biased targets in tokamak plasmas

Abstract The heat flux control of the divertor plate via strike-point splitting generated by biased targets was proposed in the HL-2A tokamak (Cui et al 2021 Fusion Eng. Des. 173 112963). To understand the helical scrape-off layer (SOL) currents driven by hybrid biasing, two SOL current models (model A and B) are employed. Model A is a simplified 2D model that focuses on investigating the effect of biasing on the sheath and elucidating the fundamental physical mechanism of bias-driven SOL current paths. The potential, charge density, electric field and current densities are calculated. Model B takes into account the actual tokamak geometry and computes the resonant magnetic perturbations (RMPs) generated by bias-driven linear decay currents. Additionally, strike-point splitting is observed in the HL-2A tokamak, indicating that the SOL currents generated by hybrid biasing are capable of generating strong RMPs and consequently influence the magnetic topology. These results confirm the potential of heat/particle flux control by hybrid divertor biased targets.

Chitosan supported hetero-metallic bio-nanocomposites for paracetamol removal from homogeneous solutions and heterogeneous mixtures with focused antibacterial studies

Biopolymers infused with bimetallic nanoparticles exhibit a wide range of functionalities necessary for efficiently eliminating diverse water contaminants. However, the protracted production process requires further exploration. As such, present study seeks to optimize microwave-assisted technique for the facile synthesis of cross-linked chitosan (CTS) supported bimetallic-oxide nanoparticles, specifically zinc oxide (ZnO) and iron-oxide (Fe3O4), denoted as CTS-TTP/Zn-Fe. The primary objective is to investigate the efficacy of these beads in the removal of Paracetamol (PCM) from single and complex water matrices while also assessing their antibacterial properties. Characterization includes chemical composition, surface structures, thermal stability, and magnetic properties. The experimental results demonstrated that CTS-TPP/Zn-Fe beads achieved a remarkable PCM removal efficiency of ~99 % (qm = 4.98 mg g−1), with a Zn:Fe mole ratio of 1:1. The experimental data showed good applicability with Freundlich isotherm and chemisorption-supported rate models (R2 > 0.9). To evaluate the long-term viability and practicality of these beads, three crucial field applicability tests were conducted. These encompassed competition studies with other pharmaceuticals, desorption investigations for repeated use, and efficiency evaluations in an ionic solution. Collectively, this research provides a comprehensive understanding, spanning from material design to practical applications, with potential relevance for large-scale wastewater treatment when coupled with appropriate flux control measures.

A Simple Online Tuning Flux Weighting Factor in Finite Control Set – Predictive Torque Control for Induction Motor Drive

The Finite Control Set-Predictive Torque Control (FSC-PTC) is a practical and intuitive method to control an Induction Motor (IM). However, the challenge of this technique is the difficulty of tuning the weighting factor so that it performs optimally at all speeds. Hence, this paper proposes a new method for improving the optimization technique by automatically tuning the weighting factor using a flux controller. The flux controller is represented as a DC gain and designed to be proportional to the absolute value of the predicted stator flux error. This method eliminates the need for complex computation to select the suitable weighting factor while also efficiently regulating flux and torque. The proposed method is experimentally validated on a DS1104 controller board and compared to a constant flux weighting factor method that was tested under speed conditions. The results demonstrate that the new method can further decrease the torque ripple compared to the constant weighting factor while maintaining the flux ripple and harmonic distortion limits.

Spontaneous asymmetry effect induced by uniform magnetic fields in capacitively coupled plasmas under perfectly symmetric conditions

Abstract Introducing asymmetry in capacitively coupled plasmas (CCPs) is a common strategy for achieving independent control of ion mean energy and flux. Our 1d3v particle-in-cell/Monte Carlo collision simulations reveal that a uniform magnetic field within a specific range can induce spatial asymmetry in low-pressure CCPs, even under perfectly symmetric conditions. This asymmetry, characterized by a shift in the plasma density distribution and significant differences in electron kinetics between the two sides of the plasma, leads to strong ionization and most electron losses on the low-density side, while the high-density side experiences weak ionization and minimal electron losses. The underlying mechanism triggering this spontaneous asymmetry is the differential influence of the magnetic field on low-energy (local) and high-energy (relatively nonlocal) electrons. Under conditions of low pressure and an appropriate magnetic field, this disparity in electron kinetic behavior leads to a spontaneous amplification of the asymmetry induced by random fluctuations until a steady state is reached, culminating in a spontaneous asymmetric effect.

Improved Performance of the Permanent Magnet Synchronous Motor Sensorless Control System Based on Direct Torque Control Strategy and Sliding Mode Control Using Fractional Order and Fractal Dimension Calculus

This article starts from the premise that one of the global control strategies of the Permanent Magnet Synchronous Motor (PMSM), namely the Direct Torque Control (DTC) control strategy, is characterized by the fact that the internal flux and torque control loop usually uses ON–OFF controllers with hysteresis, which offer easy implementation and very short response times, but the oscillations introduced by them must be cancelled by the external speed loop controller. Typically, this is a PI speed controller, whose performance is good around global operating points and for relatively small variations in external parameters and disturbances, caused in particular by load torque variation. Exploiting the advantages of the DTC strategy, this article presents a way to improve the performance of the sensorless control system (SCS) of the PMSM using the Proportional Integrator (PI), PI Equilibrium Optimizer Algorithm (EOA), Fractional Order (FO) PI, Tilt Integral Derivative (TID) and FO Lead–Lag under constant flux conditions. Sliding Mode Control (SMC) and FOSMC are proposed under conditions where the flux is variable. The performance indicators of the control system are the usual ones: response time, settling time, overshoot, steady-state error and speed ripple, plus another one given by the fractal dimension (FD) of the PMSM rotor speed signal, and the hypothesis that the FD of the controlled signal is higher when the control system performs better is verified. The article also presents the basic equations of the PMSM, based on which the synthesis of integer and fractional controllers, the synthesis of an observer for estimating the PMSM rotor speed, electromagnetic torque and stator flux are presented. The comparison of the performance for the proposed control systems and the demonstration of the parametric robustness are performed by numerical simulations in Matlab/Simulink using Simscape Electrical and Fractional-Order Modelling and Control (FOMCON). Real-time control based on an embedded system using a TMS320F28379D controller demonstrates the good performance of the PMSM-SCS based on the DTC strategy in a complete Hardware-In-the-Loop (HIL) implementation.

Maximizing torque per volume index for SHESM based on two-dimensional method and meta-heuristic optimization algorithms

In this paper, a permanent magnet synchronous machine (PMSM) with an auxiliary winding (AW) on the rotor is analyzed by two-dimensional approach. This PMSM with AW (AWPMSM) can be used in many applications such as propulsion system, aircraft and traction because it includes rotor flux control capability. First, the magnetic field in different parts of AWPMSM is calculated based on Maxwell equations. Then, as a consequence of the magnetic field, the torque components, including cogging, reluctance, electromagnetic and instantaneous torque are computed. Next, torque-speed characteristic has been investigated. This AWPMSM can be located in the flux weakening mode in two ways, first one is to attenuate the rotor field by changing the direction of the AW field and the other one is to adjust the armature current angle, both of them have been investigated. After that, the overload capability and temperature effects have been analyzed. Finally, using the meta-heuristic algorithms such as genetic algorithm, particle swarm optimization, differential evolution and teaching learn base optimization the dimensions of AWPMSM and the initial angle of the rotor are determined in such a way that the torque-to-volume ratio is maximized. The influences of the type of armature winding and the magnetization patterns have also been investigated. The results obtained by the two-dimensional method have been confirmed numerically.

Spatially-resolved spectroscopic investigation of the inhomogeneous magnetic field effects on a low-pressure capacitively-coupled nitrogen plasma

Although magnetized plasmas have been frequently used to enhance the process rate or improve the film quality via the control of ion flux as well as energy and plasma density in semiconductor processes, the inhomogeneous magnetic field—which leads to plasma non-uniformity—remains as a problem to be solved. To address this problem, it is essential to conduct a comprehensive assessment of the magnetic effect throughout the entire discharge. Therefore, in the present study, we investigated the magnetic field effects (B < 100 G) on a capacitively-coupled nitrogen plasma based on spectroscopic analyses. The spatially-resolved emission spectra were measured along the radial direction at various vertical positions under the pressures of 10 mTorr and 250 mTorr both with and without magnetic field. By analyzing emission spectra such as N2 FPS, N2 SPS, N2+ FNS, and N I, we were able to obtain the radial distributions of reactive species density, vibrational temperature, and excitation temperature. In low-pressure plasma, with the application of a magnetic field, maximum increases in vibrational temperature and excitation temperature of 462 K and 491 K, respectively, were observed within the bulk region beneath the magnet. This magnetic effect resulted in a significant increase in reactive species density along the radial direction. It was also found that the local enhancement of ion density by magnetic field was strongly related to the increase in excitation temperature and the density of the N2+(B) state. From this result, it is suggested that introducing an asymmetric magnetic field could modulate the spatial distributions of the physical and chemical properties of the plasma.

Skin Effect of Electromagnetic Flux in Anisotropic Zero‐Index Metamaterials

AbstractSkin effect in electromagnetism describes the tendency of alternating current to predominantly flow near the surface rather than through the center of a conductor. Here, another skin effect of electromagnetic flux is reported to occur in non‐conductive materials, specifically within 3D anisotropic zero‐index metamaterials, as well as its potential application in subwavelength wave manipulation. It is found that when a medium of near‐zero longitudinal permittivity and permeability is embedded with inclusions whose transverse permittivity and/or permeability approach zero, the electromagnetic flux therein is directed and extremely compressed beneath the surfaces of inclusions within a skin depth less than λ0/150. This unusual effect empowers arbitrary control of electromagnetic flux at deep subwavelength scale. Customized subwavelength pathways for electromagnetic flux are demonstrated in full‐wave simulations via practical implementations. The study opens a new avenue for extreme confinement and flexible control of electromagnetic flux at deep‐subwavelength scale.