Discrete Switching Research Articles

A New Topology for Electric All-Terrain Vehicle Hybrid Battery Systems Using Low-Frequency Discrete Cell Switching

This article presents an investigation into the feasibility of a novel discrete-switched topology for an electric all-terrain vehicle (e-ATV) hybrid battery system (HBS) that avoids expensive and bulky dc–dc converters using a simpler discrete-switched structure together with an intelligent low-frequency switching algorithm. Hardware is simplified at the expense of more complex control. The algorithm switches cells in and out of series strings, based on their state of charge relative to other cells in the pack and the power being drawn from the pack. The principles are demonstrated using a simulated model combining lithium-titanate-oxide (LTO) and lithium-iron-phosphate (LFP) cells together in an e-ATV battery pack. Despite its simplicity, the intelligent switching algorithm successfully allocates power to different elements of the battery and ensures that the state of charge remains broadly balanced throughout discharge, with the pack ending up in good balance: the LFP cells are in balance to within 0.01% of each other and the LTO cells within 0.1% of each other. While the article focuses on the essential feasibility of the concept, it also identifies future research for including thermal effects, uncertainties in state estimation, cell aging and nonuniformly, and consideration of other powertrain components, for example, motor and power electronics.

S-Palmitoylation of Synaptic Proteins in Neuronal Plasticity in Normal and Pathological Brains.

Protein lipidation is a common post-translational modification of proteins that plays an important role in human physiology and pathology. One form of protein lipidation, S-palmitoylation, involves the addition of a 16-carbon fatty acid (palmitate) onto proteins. This reversible modification may affect the regulation of protein trafficking and stability in membranes. From multiple recent experimental studies, a picture emerges whereby protein S-palmitoylation is a ubiquitous yet discrete molecular switch enabling the expansion of protein functions and subcellular localization in minutes to hours. Neural tissue is particularly rich in proteins that are regulated by S-palmitoylation. A surge of novel methods of detection of protein lipidation at high resolution allowed us to get better insights into the roles of protein palmitoylation in brain physiology and pathophysiology. In this review, we specifically discuss experimental work devoted to understanding the impact of protein palmitoylation on functional changes in the excitatory and inhibitory synapses associated with neuronal activity and neuronal plasticity. The accumulated evidence also implies a crucial role of S-palmitoylation in learning and memory, and brain disorders associated with impaired cognitive functions.

Unipolar Potentiation and Depression in Memristive Devices Utilizing the Subthreshold Regime

We present a resistance switching device that exhibits analogue potentiation and depression of conductance under the same voltage polarity. This contrasts with previously studied devices that potentiate and depress under opposite polarities. We refer to this mode of operation as the subthreshold regime due to it occurring at voltage or current biases that are insufficient to produce discrete or non-volatile switching. This behaviour has the potential to reduce the complexity of neuronal and synaptic circuitry in neuromorphic computing by removing the need for voltage pulses of both positive and negative polarities. The characteristically long timescales may also help replicate bio-realistic timings. In this paper, we detail how to induce this unique behaviour, how to tune its properties to a desired response, and finally, we demonstrate one potential application.

Retracted: Accelerated Iterative Learning Control for Linear Discrete Time Invariant Switched Systems

Retracted: Accelerated Iterative Learning Control for Linear Discrete Time Invariant Switched Systems

Characterization and Selection of Probability Density Function in a Discrete Random Switching Period SVPWM Strategy

Aiming at suppressing the switching frequency harmonics in the integrated permanent magnet synchronous motor (PMSM) systems, a discrete random switching period (DRSP) space vector pulse width modulation (SVPWM) technique is proposed in the present study. In the proposed DRSP-SVPWM technique, the switching period is randomized according to a predefined frequency sequence. Accordingly, the narrow-band harmonics of the switching frequency are extended to a wider range. Then, a mathematical correlation between the probability density function and the harmonic distribution is established. Moreover, the effects of discrete uniform and beta distributions on the harmonic spreading are studied. Based on the proposed DRSP-SVPWM technique, the mathematical expression of the harmonic power spectrum is derived, demonstrating the intrinsic dependency between the discrete random factor and the harmonic energy distribution. Finally, a series of simulations and experimental results are compared to evaluate the performance of the proposed technique. The present study is expected to provide a theoretical basis for the design and selection of discrete frequency sequences. Meanwhile, it provides a reference to investigate the random SVPWM and improve noise and electromagnetic interference in power converters.

Domain structure evolution during polarization reversal in calcium orthovanadate single crystals

We have switched polarization in calcium orthovanadate single crystal with as-grown domain structure consisting of isolated domains with charged domain walls (CDWs) located in the bulk using pretreatment by ac field and subsequent switching in dc field at the elevated temperature. The formation of the domain ledges at the CDW in the bulk and their growth in the polar direction has been revealed. The isolated domains with optically well-defined walls appeared when the ledge tops reached the surface, their shape and sizes remaining constant during further switching. Unlike usual continuous domain wall motion, we have observed the discrete switching by arising of the isolated domains without any input of the traditional domain nucleation at the polar surface. The obtained results have been explained under the assumption that at the used experimental conditions, the applied field is above the threshold value for ledge nucleation at CDW in the bulk, but below the threshold for domain wall motion at the surface. Thus, we have obtained the discrete switching by ledge growth without any sideways motion of the domain walls and domain coalescence. The nonuniform evolution of the domain structure at the surface is due to the dependence of the switching rate on the distance from CDW to the polar surface, which is random in the studied domain structure.

A multi‐group SEIRI epidemic model with logistic population growth under discrete Markov switching: Extinction, persistence, and positive recurrence

This paper is concerned with the stochastic dynamics of a multi‐group stochastic SEIRI epidemic model with logistic population growth, standard incidence rate, and Markovian switching. For this purpose, we first show that the solution of the stochastic system is positive and global. Then we obtain sufficient conditions for the extinction of disease. In addition, the persistence in the mean of disease is proved. Specifically, by constructing suitable stochastic Lyapunov functions, we find a domain that is positive recurrence for the solution of stochastic system. Finally, numerical simulations are employed to verify our analytical results.

Zero-voltage and frequency pattern selection for DC-link loss minimization in PWM-VSI drives

The modulation of a voltage source inverter output causes losses and harmonic distortions on the load side and the DC-link capacitor due to the discrete switching of the semiconductors. High-frequent voltage pulses are digitally programmed to control the inverter output and determine the harmonic distortions. This paper presents an optimization in terms of pulse- and frequency-pattern selection for reducing load distortions while keeping DC-link losses minimal. In detail, the fact that pulse and frequency patterns are independent from each other is utilized and a modified three-zone hybrid space vector pulse-width modulation is proposed where optimal frequency patterns are selected for every carrier cycle. Simulations and experimental results validate the optimizations.

A Novel Framework of Extended Active Power and Its Application Into Low Complexity MPC for Enhanced Steady-State Performance

This article proposes a novel low complexity model predictive control (LC-MPC) for the performance improvement of the ac/dc converter under unbalanced grid voltages. Although the finite control set model predictive control (FCS-MPC) is a very effective control method, whose cost function is evaluated for all discrete switching states, presenting a high calculation burden for the efficient control. To obtain a reduced harmonic of the grid current and a low calculation burden under unbalanced grid conditions, a new framework of the extended active power is proposed and a negative conjugate of new complex power is chosen as a control variable. In the proposed LC-MPC method, the best voltage vector is obtained with only one prediction whether it is the proposed single-vector-based LC-MPC (SVLC-MPC) or double-vector-based LC-MPC (DVLC-MPC) method, and the optimal duration time using the framework of the extended active power is derived in detail based on the principle of minimizing the error of the new complex power. The proposed LC-MPC has a similar dynamic performance with the prior model predictive control (MPC) methods and obtains much better steady-state performance, i.e., the reduced harmonics of grid currents, under severely unbalanced grid voltages. The comparative experiments confirm the effectiveness of the proposed LC-MPC method.

Integral input-to-state stability of switched delayed systems with delay-dependent impulses under generalized impulsive and switching scheme

This paper studies integral input-to-state stability (iISS) of a class of hybrid delayed systems with impulse and switching behavior, in which the delay-dependent impulse and switching behavior are allowed for asynchronous occurrence. Relative to admissible edge-dependent average dwell time (AED-ADT) concept of the switching signal, a fresh concept of admissible edge-dependent average impulsive interval (AED-AII) is proposed for the impulse signal. Several sufficient criteria for iISS are achieved by using multiple Lyapunov–Krasovskii functional (MLKF) tool, AED-ADT switching, and AED-AII schemes. An improved inequality that describing the relation among Lyapunov function continuous switching signal and discrete impulse is constructed, where the jump amplitude at discrete switching points and impulsive moments including delay-dependent part and delay-independent part are involved. Compared with existing results, our conclusions have the following novelties: (1) the influence of time delay existing in continuous dynamics and discrete impulse on the function part of L-K functional is dug out, which is less conservative; (2) the AED-AII scheme proposed in this paper is combined with the AED-ADT switching method, which contains a larger set of the impulsive and switching signal. Moreover, the stability criterion is suitable for the arbitrary time delay in situation that all the subsystems are destabilizing. Finally, an example is given to verify the validity of the results.

A New Discrete Analog Circuit Solution for Capacitive Rotary Encoders

In the time of global chip crisis, it is clear that alternative electronic solutions are necessary; particularly for capacitive rotary encoders, or similar capacitive sensors where demodulation techniques are extensively used. In this work, a discrete analog switch based circuit solution is proposed for the capacitive rotary encoders for the first time in the literature to the best of our knowledge. A 3-layer uniquely designed capacitive encoder prototype is used as a capacitive sensor. The analog switch with OPAMP based demodulation configuration designed for this work is both cheaper and it works at higher frequencies than the analog multiplier configuration. Also, unlike ASIC, it does not require high-tech for production. With the established test setup; noise, smallest perceptible capacitance, nonlinearity and temperature analyses of the circuit were made and competing results were achieved. The noise levels in terms of degree and voltage are measured as 0.0063° and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$36.62~\mu \text{V}\sqrt {\text {Hz}}$ </tex-math></inline-formula> ; respectively. Minimum measurable capacitance achieved with the discrete analog circuit is 2.54 aF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sqrt {\text {Hz}}$ </tex-math></inline-formula> . Nonlinearity was found to be 0.29% which is highly correlated with the mechanical misalignments of the capacitive encoder. Although this particular study is carried out on capacitive encoders, the proposed circuit solution can be used for similar types of sensors.

Stability of switched stochastic reaction–diffusion systems

As one of important hybrid dynamical systems, switched system has practical applications in some practical systems. Generally, switched system is made up of a family of continuous-time subsystems and discrete switching signals. Affected by environmental disturbance, stochastic switched system should be considered. This paper deals with a class of switched stochastic reaction-diffusion systems (SSRDSs, in short), where the discrete switching signal is a right continuous and piecewise function. The switching instants are stopping times or deterministic times. Criterions on stability in probability and exponential stability in mean square of the trivial solution for SSRDSs are derived by means of Lyapunov functional methods. We propose two examples to verify the obtained theoretical results.

Finite-time stability analysis of switched stochastic reaction-diffusion systems

In this work, we consider a class of switched stochastic reaction-diffusion systems (SSRDSs, in short), where the discrete switching signal is a right continuous, piecewise function and the switching instants are stopping times or deterministic times. Criteria on finite-time stability in the probability of the trivial solution for SSRDSs are derived by means of Lyapunov functional methods. We propose an example to verify the obtained theoretical results.

Continuous Tracking of Task Parameters Tunes Reaching Control Online.

A hallmark of human reaching movements is that they are appropriately tuned to the task goal and to the environmental context. This was demonstrated by the way humans flexibly respond to mechanical and visual perturbations that happen during movement. Furthermore, it was previously showed that the properties of goal-directed control can change within a movement, following abrupt changes in the goal structure. Such online adjustment was characterized by a modulation of feedback gains following switches in target shape. However, it remains unknown whether the underlying mechanism merely switches between prespecified policies, or whether it results from continuous and potentially dynamic adjustments. Here, we address this question by investigating participants’ feedback control strategies in presence of various changes in target width during reaching. More specifically, we studied whether the feedback responses to mechanical perturbations were sensitive to the rate of change in target width, which would be inconsistent with the hypothesis of a single, discrete switch. Based on movement kinematics and surface EMG data, we observed a modulation of feedback response clearly dependent on dynamical changes in target width. Together, our results demonstrate a continuous and online transformation of task-related parameters into suitable control policies.

Discrete switching in the ion sliced lithium niobate thin films with thick dielectric layer

Domain growth and shape evolution during local switching under the action of biased conductive tip of scanning probe microscope were studied in Z + cut lithium niobate on insulator (LNOI) with 1 µm-thick SiO2 layer between LN film and grounded electrode. Piezoresponse force microscopy and confocal Raman microscopy were used for domain imaging. The domain shape evolution during switching was qualitatively reconstructed. The crucial role of discrete switching on the kinetics of domain growth was revealed. The stability of the switched domains was confirmed. The obtained knowledge will be used for creation of the periodical domain structures by local switching.

Accelerated Iterative Learning Control for Linear Discrete Time Invariant Switched Systems

For a class of linear discrete time invariant stochastic switched systems with repetitive operation characteristics, a novel P-type accelerated iterative learning control algorithm with association correction is proposed. Firstly, the concrete form of accelerated learning law is given, and the generation of correction in the algorithm is explained in detail; secondly, on the premise that the switching sequence does not change along the iteration axis but only along the time axis, the convergence of the algorithm is strictly mathematically proved by using the super vector method, and the sufficient conditions for the convergence of the algorithm are given; finally, the theoretical results show that the convergence speed mainly depends on the controlled object, the proportional gain of the control law, the switching sequence, the correction coefficient, the association factor, and the size of the learning interval. Simulation results show that the proposed algorithm has a faster convergence speed than the traditional open-loop P-type algorithm under the same conditions.

Discrete resistive switching characteristics in metal-free phthalocyanine and Dy-phthalocyanine based devices

The resistive memory devices based on planar metal-free phthalocyanine (H2Pc) and sandwiched Dy-phthalocyanine (DyPc2) have been prepared on an ITO glass substrate with the Al as a top electrode. The current-voltage characteristics of these devices are found to be relevant with the interlayer thickness and the crystalline structure. Both the average values of reset and set voltage increased with the increasing thickness of interlayer. The devices can be cycled more than 150 consecutive cycles when the thickness of H2Pc and DyPc2 are 60 nm and 30 nm, respectively. The resistances of present H2Pc devices are larger than that of DyPc2 devices, which may be related to different orientations of H2Pc and DyPc2 films. Additionally, a high ON/OFF current ratio of about 103 and a long retention ability of over 104 s were achieved for both devices, implying their nonvolatile storage capacity. An analysis of the current-voltage characteristics revealed that the electrical conduction behavior followed the space charge limited conduction mechanism. This study is useful to design advanced resistive memory devices and understand the underlying resistive switching mechanism.

СРАВНИТЕЛЬНАЯ ОЦЕНКА СПОСОБОВ ПИТАНИЯ СДПМ В РЕЖИМЕ ВЕНТИЛЬНОГО ДВИГАТЕЛЯ

The article provides a comparative assessment of various ways of powering a synchronous motor with permanent magnets (PMSM) in the mode of a thyratron motor (TM). Numerically, on analytical and computer models, mechanical ω = f(M), the dependence of speed on electromagnetic torque, and energy ηэ = f(M), the dependence of elec-tromagnetic efficiency are calculated from the moment, the characteristics of the motor with sinusoidal power supply and discrete switching with different values of the relative inductance of the winding. Moment pulsations are investigated. The three most common methods of discrete degree commutation are considered – 120, 180 and 150. It is shown that discrete 120 degree commutation provides the highest value of ηэ in comparison with other methods, and the mechanical character-istics are approximately the same in appearance with different power supply methods. The study of moment pulsations has shown that discrete switching without additional measures cannot compete in this indicator with the case of sinusoidal power supply, which theoretically has zero moment pulsations. However, the use of 150 degree commutation makes it possible to significantly reduce them, bringing them closer to 2…3 %. Curves are given that allow an approximate estimate of the expected moment pulsations for all discrete switching methods. Practical recommendations on the choice of the method of powering the PMSM are given.

Ultra-thin ultra-wideband tunable radar absorber based on hybrid incorporation of active devices

Structural radar absorber has important application in stealth field for its ability to effectively absorb incoming radar wave and to bear the load at the same time. Metasurface absorbers can achieve nearly-perfect absorption of radar wave, and have characteristics of light weight and thin structure, but their bandwidth are usually narrow. To solve this problem, a new method of broadening the bandwidth of metasurface absorber is proposed in this work. With varactor and PIN diode integrated in a hybrid manner, the continuous tunning and discrete switching are combined together to broaden the effective absorption bandwidth of the absorber. Using this method, an ultra-wideband tunable metasurface absorber is designed and the absorbing mechanism is analyzed in depth. By changing the bias voltages of PIN diodes and varactors, the absorbing frequency can be continuously tuned within a wide band from 4.57 GHz to 8.51 GHz. Measured results verify the low radar cross section characteristics of the absorber and the effectiveness of the design method. The proposed method is simple and feasible, and can be extended to other broadband structure design.

An Interpretation of Discrete Switching in Small-Area Semiconductors

An Interpretation of Discrete Switching in Small-Area Semiconductors