Multiple Switching Research Articles

Single-Phase Five-Level Multiswitch Fault-Tolerant Inverter

A novel Fault-tolerant (FT) multilevel inverter (MLI) to deal with both open and short circuit faults on the single and multiple switches is presented in this paper. It is formed by combining the main circuit and a redundant unit. With the help of a redundant unit, the proposed MLI preserves the same output power under any fault conditions as that of healthy mode. In addition, the inverter has equal efficiency under healthy and faulty scenarios for the given operating conditions. The redundant unit of the proposed FTMLI reduces the current stress on the main circuit switches under overload conditions. To validate the capabilities of the proposed MLI in tolerating the different faults, various simulation and experimental studies are carried out, and corresponding results are presented in this paper. The superior features like low device count, higher efficiency, and lower total blocking voltage (TBV) make the proposed MLI a reliable candidate for emergency loads. To showcase the better performance of the proposed topology over other recent topologies, comprehensive evaluation and comparisons in terms of component count and functionality are presented.

Dynamical analysis of a diffusion plant-wrack model with delay

In this paper, in view of the senescence of plant and the decay of wrack, time delays are introduced into the plant-wrack model. The effects of wrack decay and time delay on the dynamical behaviors of the diffusive plant-wrack model are studied analytically and numerically. When the delay is zero, the wrack decay will induce the change of stability of the unique equilibrium point, further lead to the occurrence of the Hopf bifurcation and the Turing instability. When the delay is present, the conditions for the occurrence of the Hopf bifurcation are established. By comparing the results of the model without and with delay, it is found that the increases of delay may induce no stability switches, a single stability switch or multiple stability switches, when the value of wrack decay can stabilize model with zero delay. When the value of wrack decay can destabilize model with zero delay, numerical simulations show that the small delay may cause homogeneous distributions of vegetation, while the larger delay may cause the emergence of periodic oscillation of vegetation. The obtained results provide a basis for understanding the spatiotemporal evolution of such a plant-wrack model with delay.

20-State Molecular Switch in a Li@C60 Complex.

A substantial potential advantage of industrial electric and thermoelectric devices utilizing endohedral metallofullerenes (EMFs) is their ability to accommodate metallic moieties inside their empty cavities. Experimental and theoretical studies have elucidated the merit of this extraordinary feature with respect to developing electrical conductance and thermopower. Published research studies have demonstrated multiple state molecular switches initiated with 4, 6, and 14 distinguished switching states. Through comprehensive theoretical investigations involving electronic structure and electric transport, we report 20 molecular switching states that can be statistically recognized employing the endohedral fullerene Li@C60 complex. We propose a switching technique that counts on the location of the alkali metal that encapsulates inside a fullerene cage. The 20 switching states correspond to the 20 hexagonal rings that the Li cation energetically prefers to reside close to. We demonstrate that the multiswitching feature of such molecular complexes can be controlled by taking advantage of the off-center displacement and charge transfer from the alkali metal to the C60 cage. The most energetically favorable optimization suggests 1.2-1.4 Å off-center displacement, and Mulliken, Hirshfeld, and Voronoi simulations articulate that the charge migrates from the Li cation to C60 fullerene; however, the amount of the charge transferred depends on the nature and location of the cation within the complex. We believe that the proposed work suggests a relevant step toward the practical application of molecular switches in organic materials.

New fluorescent pH indicators for characterizing cement carbonation

Fluorescent indicators of a wider labeling pH range of 7.0–12.5 were prepared to characterize the pH evolution of the accelerated/natural carbonation of cement and the corrosion of steel bar. Compared with conventional indicators (phenolphthalein, pH range of 8.2–8.5), these indicators indicate multiple pH-induced switches of different fluorescence emissions for the fluorescence resonance energy transfer between donor–acceptor. The results showed that the newly-developed indicators are sensitive and applicable for labeling both natural and accelerated carbonation of cement. Investigations by Fourier Transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis demonstrated the reliability of these indicators, that is, in the “uncarbonated area” shown by phenolphthalein, carbonization actually occurs as exhibited by fluorescent indicators. Furthermore, electrochemical impedance spectroscopy, as well as dynamic potential polarization studies showed that rusting/corrosion of reinforcing steel started when the pH dropped to 11.5 in the simulation study. This work promoted the contribution of fluorescent indicators in cement carbonation characterization, with a wide pH response.

Monitoring Chip Branch Failure in Multichip IGBT Modules Based on Gate Charge

The reliability of the multichip insulated gate bipolar transistor (IGBT) modules has been a concern. Condition monitoring is an effective approach to enhance reliability and improve the quality of customer service. This paper proposes a method for monitoring the chip branch failure due to bond wires fatigue in the multichip IGBT modules. The idea is based on the cumulative effect of the gate charge deviation when the chip branch fails. By integrating the turn-on gate current of multiple switching cycles, the health state of multichip IGBT modules is characterized by the capacitor voltage as a health-sensitive parameter that can be extracted in the proposed monitoring circuit integrated into the gate driver. The capacitor voltage decreases significantly when the chip branch occurs due to bond wires fatigue. It is stable during sampling and has a strong immunity to junction temperature, collector current, and collector-emitter voltage. Besides, the method is non-intrusive and has the potential for real-time and online monitoring. These characteristics make the method reliable, easy to implement, and convenient for health status identification. The confirmatory experiment is carried out to verify the feasibility of the method.

Condition for Suppressing Subharmonic Oscillation in Digital Peak Current-Mode Multi-Cycle Controlled Converters

Peak current-mode control is a control algorithm for switched-mode power supplies (SMPSs) that is characterized by high-speed response and high-stability. Currently, a method of implementing peak current-mode control in a digital controller has been proposed however, there is a limit to increasing the switching frequency. Therefore, in a previous study, we proposed a method that enables high-frequency switching by applying a control method called multi-cycle control, which applies the same ON duty ratio over multiple switching cycles to the existing method. Furthermore, in peak current-mode control, an unstable phenomenon called subharmonic oscillation occurs, which is problematic. Generally, this problem is solved by slope compensation however, it cannot be applied to multi-cycle control. Therefore, in previous work, we derived the condition to suppress subharmonic oscillation by designing parameters of multi-cycle control. In this study, we verified the above-mentioned conditions using a real-circuit.

Oversampling Techniques to Improve the Accuracy of Hardware-in-the-Loop Switching Models

Real-time Hardware-In-the-Loop implementations for power converters involve digital sampling of the on-off signals that are applied to the switches. The most basic way of considering it, is to process only one switch state during a simulation step. This usually causes an incorrect input reading because it can change during the step. The negative effects include the appearance of undesirable subharmonics and numerical inaccuracy. In this work, input signal oversampling is proposed. Thus, several switch states can be properly processed within the same simulation step. The question is how to use this additional information. This paper proposes two oversampling approaches: a sequential one, which is based on previous works, and a parallel implementation, which is the main contribution of the paper. The results obtained with these techniques are compared between them and with the model without oversampling, showing a significant increase in accuracy for both oversampling approaches around 98%. Although the accuracy is very similar in both methods, synthesis results for FPGA implementation are clearly better for the parallel method, which can be easily adapted to process multiple switching events. The final experimental results show a great subharmonic decrease up to 99%.

Multiple Open-Circuit Fault Detection and Isolation Using Universal Low-Cost Diagnosis Circuits for Reconfigurable Dual-Active-Bridge Converters

Compared with single-switch open-circuit faults (SOCFs), multiple switches open-circuit faults (MOCFs) of power electronic devices (PEDs) due to high voltage or current stress, false triggering, and manufacturing tolerance have become more challenging. To address this issue, a reconfigurable dual-active-bridge (R-DAB) converter is presented with a fast, accurate, robust, and low-cost fault detection (FD) and fault isolation (FI) scheme to accommodate both SOCFs and MOCFs. Compared with the standard dual active bridge (DAB) topology, the proposed R-DAB will utilize a center-tapped high-frequency transformer and two symmetrical auxiliary inductors, where inherent half-bridge conduction branches are capable of maintaining uninterrupted operations. The proposed FD and FI scheme is straightforward and universal since only the center-tap current in the primary and secondary bridge is monitored as the universal fault signature. Moreover, a simple and low-cost fault diagnostic circuit was designed, which can detect and isolate various open circuit faults (OCFs) of PEDs under varying input and output conditions, without using expensive voltage and current sensors. This sensorless fault diagnosis technique can achieve the fastest fault detection and isolation speed reported so far, which is within a couple of \boldmath <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu s$</tex-math></inline-formula> for various OCFs. Experimental results were acquired from an R-DAB prototype under various OCFs to validate the effectiveness of the proposed technique.

Wireless Battery Chargers Operating at Multiple Switching Frequencies with Improved Performance

The operation of wireless battery chargers at multiple switching frequencies may lead to a noticeable suppression of conducted and radiated electromagnetic interference (EMI) at the cost of decreased efficiency (mainly at lower load resistances) and increased peak and root mean square values of currents of power components of the wireless battery charger. Moreover, the reduction in conducted EMI is only moderate (&lt;8.3 dB). Therefore, a novel approach based on modified resonant circuits and a modified control technique to obtain better reduction in the conducted and radiated EMI without significantly compromising other performance characteristics of the wireless battery charger is proposed and validated by using simulations and experiments. It is shown in this paper that the wireless charger operating at multiple switching frequencies with the proposed approach for the performance improvement has a more effective implementation of the four-switching frequency spread-spectrum technique with better conducted and radiated EMI reduction at all load resistances, lower values of peak and RMS currents at all load resistances, and higher efficiency in constant current mode and in the beginning of constant voltage mode (at lower values of the load resistances) than that of the conventional wireless charger operating at multiple switching frequencies.

A massively parallel screening platform for converting aptamers into molecular switches

Aptamer-based molecular switches that undergo a binding-induced conformational change have proven valuable for a wide range of applications, such as imaging metabolites in cells, targeted drug delivery, and real-time detection of biomolecules. Since conventional aptamer selection methods do not typically produce aptamers with inherent structure-switching functionality, the aptamers must be converted to molecular switches in a post-selection process. Efforts to engineer such aptamer switches often use rational design approaches based on in silico secondary structure predictions. Unfortunately, existing software cannot accurately model three-dimensional oligonucleotide structures or non-canonical base-pairing, limiting the ability to identify appropriate sequence elements for targeted modification. Here, we describe a massively parallel screening-based strategy that enables the conversion of virtually any aptamer into a molecular switch without requiring any prior knowledge of aptamer structure. Using this approach, we generate multiple switches from a previously published ATP aptamer as well as a newly-selected boronic acid base-modified aptamer for glucose, which respectively undergo signal-on and signal-off switching upon binding their molecular targets with second-scale kinetics. Notably, our glucose-responsive switch achieves ~30-fold greater sensitivity than a previously-reported natural DNA-based switch. We believe our approach could offer a generalizable strategy for producing target-specific switches from a wide range of aptamers.

Bulk assemblies of organic antimony chloride with multiple reversible photoluminescence switching for anti-counterfeiting and information encryption

Forgery and leakage of confidential information will bring great social harm and economic loss, so it is necessary to take simple and effective strategies to ensure information security. Here, two different zero-dimensional (0D) organic antimony chlorides of [Ph3S]2SbCl5·2C2H3N (1) and [Ph3S]2SbCl5 (2) were obtained by inserting the organic ligand of Ph3SCl (triphenylsulfonium chloride) into SbCl3 lattice via different chemical synthesis methods. Under photoexcitation, compound 1 shines bright yellow emission with a photoluminescence quantum efficiency (PLQE) of 98.2%, while compound 2 shows efficient red emission with a PLQE of 99.6%. Both of them exhibit dual-emission bands, which stem from the singlet self-trapped excitons (STEs) and triplet STEs, respectively. Particularly, the dynamic transformation processes between compounds 1 and 2 are witnessed via the acetonitrile (C2H3N) stripping/insertion under different external stimuli, which was demonstrated by the results of powder X-ray diffraction and photoluminescence (PL) spectra. In addition, the continuous heating of compound 2 can make the emission color change from red to yellow again, accompanied by the lattice distortion of [SbCl5]2- pyramid. Finally, the multiple anti-counterfeiting and information encryption models were fabricated based on the reversible PL switching of the title compounds under different external stimuli.

Double broadband enhanced absorber based on graphene-coupled metal disk resonator structure

A double broadband terahertz absorber based on nonstructured graphene with a dielectric coupled gold disk structure was investigated in this paper. The results show that one absorption band can be switched from reflection state (“OFF”) to absorption state (“ON”), and the other absorption band can be switched from reflection state (“OFF”) to absorption state (“ON”), with bandwidths of over 90% absorption ranging from 0.46 to 1.4 THz and 2.38 to 3.35 THz, respectively. Furthermore, the double broadband terahertz absorber has polarization and background refractive index insensitivity. The Fabry Perot resonance between the graphene sheet and the bottom gold reflector is primarily responsible for the double broadband absorption in graphene, which can be enhanced by the addition of a gold disk resonator. Because of the aforementioned properties, the proposed absorber has potential applications in multiple optical switches, terahertz photoelectric detectors, modulators, and sensors.

Large-area synthesis of high electrical performance MoS2 by a commercially scalable atomic layer deposition process

This work demonstrates a large area process for atomically thin 2D semiconductors to unlock the technological upscale required for their commercial uptake. The new atomic layer deposition (ALD) and conversion technique yields large area performance uniformity and tunability. Like graphene, 2D Transition Metal Dichalcogenides (TMDCs) are prone to upscaling challenges limiting their commercial uptake. They are challenging to grow uniformly on large substrates and to transfer on alternative substrates while they often lack in large area electrical performance uniformity. The scalable ALD process of this work enables uniform growth of 2D TMDCs on large area with independent control of layer thickness, stoichiometry and crystallinity while allowing chemical free transfers to application substrates. Field effect transistors (FETs) fabricated on flexible substrates using the process present a field effect mobility of up to 55 cm2/Vs, subthreshold slope down to 80 mV/dec and on/off ratios of 107. In addition, non-volatile memory transistors using ferroelectric FETs (FeFETs) operating at ±5 V with on/off ratio of 107 and a memory window of 3.25 V are demonstrated. These FeFETs demonstrate state-of-the-art performance with multiple state switching, suitable for one-transistor non-volatile memory and for synaptic transistors revealing the applicability of the process to flexible neuromorphic applications.

Previous disease-modifying treatments influence T lymphocyte kinetics in people with multiple sclerosis switching to ocrelizumab

BackgroundRecently, concern has been raised about the influence of the previous disease-modifying treatments (DMTs) on the clinical efficacy of ocrelizumab (OCR).We aimed to evaluate whether the previous DMT affects the lymphocyte subset kinetics in people with Multiple Sclerosis (MS) switching to OCR. MethodsThis is a multicenter, retrospective, real-world study on consecutive MS patients who started or switched to OCR. We grouped them by prior DMT in: (i) naïve-to-treatment (NTT), (ii) switching from fingolimod (SF) and (iii) switching from natalizumab (SN). Differences in absolute lymphocyte count and lymphocyte subset count changes, considering the period from baseline to 6 months, over all the three groups were assessed with an inverse-probability-weighted regression adjustment model. ResultsMean T CD4+ cell count reduction from baseline to the six-month follow-up was more pronounced in the SN group compared to the NTT (p = 0,026). Further, patients in the SF group experienced a less pronounced CD4 T cell number decrease than both NTT and SN groups (p = 0,04 and p < 0,001, respectively). Patients in the SF group experienced an increase in CD8 T cell absolute number, whereas those in the NTT and SN groups experienced a significant decrease (p = 0,015 and p < 0,001, respectively). Patients experiencing early inflammatory activity showed a lower CD8+ cell count at baseline than stable patients (p = 0,02). ConclusionsPrevious DMTs influence the lymphocyte kinetics in people with MS switching to OCR. Reassessment of these findings over a larger population may help optimize the switch.

Study on Multi-Mode Switching Control Strategy of Active Suspension Based on Road Estimation

In this paper, the least squares method is used to determine the vertical height of the road space domain. Based on the road estimation method, the active suspension control mode switching model is constructed, and the dynamic characteristics of the vehicle in comfort, safety, and integrated modes are analyzed. The vibration signal is collected by the sensor, and the parameters such as vehicle driving conditions are solved for in reverse. A control strategy for multiple mode switching under different road surfaces and speeds is constructed. At the same time, the particle swarm optimization algorithm (PSO) is used to optimize the weight coefficients of LQR control under different modes, and the dynamic performance of vehicle driving is comprehensively analyzed. The test and simulation results show that the road estimation results under different speeds in the same road section are very close to the results obtained by the detection ruler method, and the overall error is less than 2%. Compared with the active suspension controlled by passive and traditional LQR, the multi-mode switching strategy can achieve a better balance between driving comfort and handling safety and stability, and also improve the driving experience more intelligently and comprehensively.

Dual size/charge-switchable and multi-responsive gelatin-based nanocluster for targeted anti-tumor therapy

Biopolymers with excellent biocompatibility and biodegradability show great potential for designing drug nanocarriers, while it's difficult to fabricate smart vehicles with multiple switching (size, surface, shape) based on biopolymers alone. Here, we report a dual size/charge-switchable and multi-responsive doxorubicin-loaded gelatin-based nanocluster (DOX-icluster) for improved tumor penetration and targeted anti-tumor therapy. The DOX-icluster was electrostatically assembled from folic acid and dimethylmaleic anhydride modified gelatin (FA-GelDMA) and small-sized DOX-loaded NH2 modified hollow mesoporous organosilicon nanoparticles (DOX-HMON-NH2). DOX-icluster had an initial size of about 199 nm at neutral pH. After accumulation in tumor tissue, the DMA bond of FA-GelDMA was cleaved and gelatin was degraded by matrix metalloproteinase (MMP-2), thus 48 nm and positively charged DOX-HMON-NH2 was released to facilitate penetration and cell internalization. DOX-HMON-NH2 was further degraded by intracellular glutathione (GSH) with releasing 48.1 % of DOX. The cellular uptake results indicated that the fabricated icluster promoted the uptake of DOX by 4T1 cells. With enhanced penetration efficacy, the tumor spheroids volume treated with DOX-icluster was reduced to 15.1 % on day 7. This cytocompatible multi-responsive gelatin-based icluster with size-shrinking and charge-reversible characteristics may be used as a significant drug carrier for tumor therapy.

Origin, heterogeneity, and interconversion of noncanonical bistable switches from the positive feedback loops under dual signaling

Designing new functional motifs with unique properties is an important objective in the realm of synthetic biology. We uncover emergent properties of positive feedback loops (PFLs) under dual input signaling using pseudo potential energy-based high-throughput bifurcation analysis. We show that under dual signaling a single PFL generates a variety of noncanonical bistable switches, with one or more bistable regions, due to fusion of multiple canonical bistable switches. Regulatory signs of the dual signaling must be coherent for mutual inhibition loop and incoherent for mutual activation loop of the PFL. Occurrence probabilities show that some of the noncanonical switches, such as isola and mushroom, are highly recurrent under random parameterization. Phase diagrams of the noncanonical switches reveal that feedback strengths of the PFL control the transition from one switch to another. Our calculations decipher the design principles of noncanonical bistable switches that originate from synthetically feasible simple PFL motifs under dual signaling.

Nussbaum‐based robust adaptive control for nonlinear switching systems with switching unknown control coefficients

AbstractThis paper develops a robust adaptive dynamic surface control (DSC) design approach for switching strict feedback nonlinear systems with multiple switching control gains and unknown control directions. To capture the multiple unknown control directions, we design multiple Nussbaum‐type gains for every subsystem. Based on this Nussbaum‐type gain design, we construct a common Lyapunov function for all subsystems via backstepping technique, which can ensure the system stability under the existence of random switches. Meanwhile, the problem of multiple switching control gains is resolved by this means. To obviate repeated differentiation and decrease computation complexity, the dynamic surface control technique is introduced. Finally, two simulation examples are provided to validate the effectiveness of the developed method.

A Faulty Submodule Mathematical Model-Based Localization Strategy for Switch Open-Circuit Fault of Module Multilevel Converter

A faulty submodule (SM) mathematical model-based switch open-circuit fault diagnosis and localization (FDL) method for module multilevel converter (MMC) is investigated in this article, which can diagnosis the faulty switch in time. Initially, the mathematical model is established through the modified switching function of the faulty SM, which can express the real switching state of the faulty SM accurately. Based on the proposed mathematical model, an innovative FDL method for MMC is proposed. The faulty switch is located by comparing the capacitor voltage calculated through the proposed mathematical model with the sampled capacitor voltage value. To enhance the accuracy and anti-interference ability of the model, the capacitance observation method is proposed in the capacitor precharge stage. The proposed FDL method can diagnose and locate faulty switch in any state of the SM, even if the operating state of the faulty SM is the same as that of the normal SM. Single or multiple switch open-circuit faults can be accurately located by this method under either light or heavy load conditions. Finally, the mathematical model and FDL method are verified through simulation and experiment.

A Multi-mode Electronic Load Sensing Control Scheme with Power Limitation and Pressure Cut-off for Mobile Machinery

In mobile machinery, hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level, but diversified control functions (e.g., power limitation and pressure cut-off) are integrated into the electronic controller only from the pump level, leading to the potential instability of the overall system. To solve this problem, a multi-mode electrohydraulic load sensing (MELS) control scheme is proposed especially considering the switching stability from the system level, which includes four working modes of flow control, load sensing, power limitation, and pressure control. Depending on the actual working requirements, the switching rules for the different modes and the switching direction (i.e., the modes can be switched bilaterally or unilaterally) are defined. The priority of different modes is also defined, from high to low: pressure control, power limitation, load sensing, and flow control. When multiple switching rules are satisfied at the same time, the system switches to the control mode with the highest priority. In addition, the switching stability between flow control and pressure control modes is analyzed, and the controller parameters that guarantee the switching stability are obtained. A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator. The results show that the MELS controller can achieve the control functions of proper flow supplement, power limitation, and pressure cut-off, which has good stability performance when switching between different control modes. This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions.