Hysteresis Switching Research Articles

Switching Dynamics in Ferroelectric Vinylidene Fluoride–Trifluoroethylene Copolymer Thin Film with α,ω-Dihexylsexithiophene Semiconductor Layer

Ferroelectric switching dynamics in thin vinylidene fluoride–trifluoroethylene copolymer films with an organic semiconductor α,ω-dihexylsexithiophene layer have been investigated on the basis of the measurements of the electrical properties including D–E hysteresis loop, switching characteristics, and capacitance changes. The authors elucidate that the full polarization reversal can be accomplished and the depletion is maintained at zero bias field. The time domain measurement together with capacitance measurements enables the evaluation of the close relationship between polarization reversal and carrier behavior in semiconductor layer. Polarization reversal toward the negative side under negative voltage progresses rapidly owing to the accumulation of majority carriers. Polarization reversal toward the positive side proceeds through two-step reversals. The mechanism of the two-step switching is explained by the depolarization field induced by the uncompensated polarization charge due to the formation of the depletion layer.

Control of magnetization reversal by combining shape and magnetocrystalline anisotropy inepitaxial Fe planar nanowires

This work presents an analysis of the in-plane magnetizationreversal mechanisms of Fe nanowires, with widths from 100 nm to 1 µm, fabricated in epitaxial Au(001)/Fe(001)/MgO(001) thin films by means of focusedion and electron beam lithographies, with either positive or negative resist. Theexperimental results show that the switching mechanisms and hysteresis are almostexclusively functions of the dimensions of the wires and of the Fe intrinsic properties,with minor influence of the specific fabrication route employed upon optimizationof nanostructure parameters in terms of crystallinity and morphology, and welldefined and reproducible geometry. The reversal processes evolve from wall pinningat low angles between the applied field and the axis of the wires to basicallyuniform magnetization rotation at high angles. This behaviour can be described interms of single spin configurations, thus ruling out the formation of multidomainstructures even at high angles. The ability to achieve these high quality and wellcontrolled nanowires allowed us to develop an analytical model, based on uniformmagnetization configurations considering just the intrinsic Fe properties and the shape anddimensions of the wires. This simple approach provides a very good qualitativeand quantitative agreement with the experimental results, thus evidencing therelatively small role of other extrinsic factors in the magnetization processes.

1‐Nanometer‐Sized Active‐Channel Molecular Quantum‐Dot Transistor

The properties of a molecular quantum dot system are investigated using a novel structure of vertical molecular transistor. This C60-based device can be operated in two new modes: voltage-controlled switching and gate-controlled hysteresis. A polaron-based model is used to explain the operation of the transistor and to introduce some general rules for the construction of polaronic molecular transistors.

Hysteresis switching loops in Ag-manganite memristive interfaces

Multilevel resistance states in silver-manganite interfaces are studied both experimentally and through a realistic model that includes as a main ingredient the oxygen vacancies diffusion under applied electric fields. The switching threshold and amplitude studied through hysteresis switching loops are found to depend critically on the initial state. The associated vacancy profiles further unveil the prominent role of the effective electric field acting at the interfaces. While experimental results validate main assumptions of the model, the simulations allow to disentangle the microscopic mechanisms behind the resistive switching in metal-transition metal oxide interfaces.

Adaptive Variable Structure Control for Uncertain Switched Delay Systems

This paper investigates the robust H∞ control problem for a class of uncertain switched delay systems with parameter uncertainties, unknown nonlinear perturbations, and external disturbance. Based on the multiple Lyapunov functions method, a sufficient condition for the solvability of the robust H∞ control problem is derived by employing a hysteresis switching law and variable structure controllers. When the upper bounds of the nonlinear perturbations are unknown, an adaptive variable structure control strategy is developed. The use of the adaptive technique is to adapt the unknown upper bounds of the nonlinear disturbances so that the objective of asymptotic stabilization with an H∞-norm bound is achieved under the hysteresis switching law. A numerical example illustrates the effectiveness of the proposed design methods.

Supermolecular switches based on multiwalled carbon nanotubes

Electrostatically actuated nanoelectromechanical switches based on intershell displacement mechanisms within batch fabricated, bidirectional multiwalled carbon nanotube (MWNT) bearings are reported. Multiple devices with a 220 nm pitch are constructed within individual MWNT supermolecules. Experimental results on performance metrics including low switching voltages (0.8 to 6 V), repeatability, hysteresis, and failure modes are presented.

High performance direct instantaneous power control of PWM rectifiers

Abstract This paper presents a new direct instantaneous power control (DPC) strategy for active rectifiers. In this novel scheme the PWM modulator has been utilized instead of the hysteresis comparators and switching table. The required converter voltage in each sampling period is directly calculated based on the reference and measured values of powers, system parameters, and the measured voltage of the AC source through simple equations which are wisely compensated for variations of the grid voltage during a sampling period. Then, the PWM generator generates the switching pulses for the voltage source converter. It is shown that the proposed DPC–PWM exhibits several features, such as a simple algorithm, constant switching frequency, robust to sampling frequency changes, robust to inductance values mismatch, and particularly it provides low sampling frequency. Extensive simulation and experimental results have proven the excellent performance and verify the validity and effectiveness of the proposed instantaneous power control scheme.

Electric pulse-induced resistive switching in ceramic interfaces

Abstract We show the existence of a reversible, complementary and polarity dependant electric pulse-induced resistance (EPIR) switching effects in Au / YBa 2 Cu 3 O 7 - δ ceramic superconductor interfaces. Non-volatile high and low resistance states and transition regions between them are obtained as a function of the amplitude and polarity of the pulsing voltage. Relaxation processes of the resistivity after applying the pulses, not associated with heating effects, are also observed. We also report on the temperature sensitivity of these resistance hysteresis switching loops, where both the difference between high and low resistance states and the voltage needed to produce the switching decrease with increasing temperature. Our results are consistent with a mechanism for the EPIR effect based on oxygen electromigration.

Polarization switching in single-mode injection semiconductor laser

Based on a previously developed polarization component method, a phenomenological model is constructed for the generation of polarized radiation in single-mode semiconductor lasers and applied to polarization switching. This model gives a good description of the experimentally observed features of the polarization process. At the same time, a number of effects related to the polarization switching rate, hysteresis characteristics, and polarization switching during optical injection are interpreted anew in terms of the formation dynamics of the laser radiation.

Stabilization of Nonnecessarily Inversely Stable First-Order Adaptive Systems under Saturated Input

This paper presents an indirect adaptive stabilization scheme for first-order continuous-time systems under saturated input which is described by a sigmoidal function. The singularities are avoided through a modification scheme for the estimated plant parameter vector so that its associated Sylvester matrix is guaranteed to be non-singular and then the estimated plant model is controllable. The modification mechanism involves the use of a hysteresis switching function. An alternative hybrid scheme, whose estimated parameters are updated at sampling instants is also given to solve a similar adaptive stabilization problem. Such a scheme also uses hysteresis switching for modification of the parameter estimates so as to ensure the controllability of the estimated plant model.

Bistable hysteresis and resistance switching in hydrogen-gold junctions

Current-voltage characteristics of ${\text{H}}_{2}\text{-Au}$ molecular junctions exhibit intriguing steps around a characteristic voltage of ${V}_{s}\ensuremath{\approx}40\text{ }\text{mV}$. Surprisingly, we find that a hysteresis is connected to these steps with a typical time scale $>10\text{ }\text{ms}$. This time constant scales linearly with the power dissipated in the junction beyond an off-set power ${P}_{s}=I{V}_{s}$. We propose that the hysteresis is related to vibrational heating of both the molecule in the junction and a set of surrounding hydrogen molecules. Remarkably, by stretching the junction the hysteresis' characteristic time becomes $>\text{days}$. We demonstrate that reliable switchable devices can be built from such junctions.

Tracking control for switched linear systems with time‐delay: a state‐dependent switching method

AbstractTracking control for switched linear systems with time‐delay is investigated in this paper. Based on the state‐dependent switching method, sufficient conditions for the solvability of the tracking control problem are given. We use single Lyapunov function technique and a typical hysteresis switching law to design a tracking control law such that the H∞ model reference tracking performance is satisfied. The controller design problem can be solved efficiently by using linear matrices inequalities. Since convex combination techniques are used to derive the delay independent criteria, some subsystems are allowed to be unstable. It is highly desirable that a non‐switched time‐delay system can not earn such property. Simulation example shows the feasibility and validity of the switching control law. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Robust H ∞ sliding mode control for a class of uncertain switched delay systems

This article considers the robust H ∞ sliding mode control problem for a class of uncertain switched delay systems. A single sliding surface is constructed such that the reduced-order equivalent sliding motion restricted to the sliding surface is completely invariant to all admissible uncertainties. For cases of known delay and unknown delay, the existence conditions of the sliding surface are proposed, respectively. The corresponding hysteresis switching laws are designed such that the sliding motion is stabilisable with H ∞ disturbance attenuation level γ. Furthermore, variable structure controllers are developed to drive the state of the switched system to reach the single sliding surface in finite time and remain on it thereafter. Finally, two numerical examples are given to illustrate the effectiveness of the proposed design methods.

Quadratic stabilization of a class of switched nonlinear systems via single Lyapunov function

This paper is concerned with the problem of globally quadratic stabilization for a class of switched cascade systems. The system under consideration is composed of two subsystems: a linear switched part and a nonlinear part, which are also switched systems. The feedback control law and the switching law are designed respectively when the first part is stabilized under some switching law and when both parts can be stabilized under some switching laws. We construct the single Lyapunov functions and design the switching laws based on the structure characteristics of the switched system. Also, the designed switching laws are of hysteresis switching form in order to avoid sliding models.

Stability switches, oscillatory multistability, and spatio-temporal patterns of nonlinear oscillations in recurrently delay coupled neural networks

A model of time-delay recurrently coupled spatially segregated neural assemblies is here proposed. We show that it operates like some of the hierarchical architectures of the brain. Each assembly is a neural network with no delay in the local couplings between the units. The delay appears in the long range feedforward and feedback inter-assemblies communications. Bifurcation analysis of a simple four-units system in the autonomous case shows the richness of the dynamical behaviors in a biophysically plausible parameter region. We find oscillatory multistability, hysteresis, and stability switches of the rest state provoked by the time delay. Then we investigate the spatio-temporal patterns of bifurcating periodic solutions by using the symmetric local Hopf bifurcation theory of delay differential equations and derive the equation describing the flow on the center manifold that enables us determining the direction of Hopf bifurcations and stability of the bifurcating periodic orbits. We also discuss computational properties of the system due to the delay when an external drive of the network mimicks external sensory input.

Robust H∞ Control of Uncertain Switched Systems: a Sliding Mode Control Design

This paper develops a new method to the robust H ∞ control problem for a class of uncertain switched systems by constructing a single robust H ∞ sliding surface. The method consists of two phases. One is to construct a single sliding surface such that the reduced-order equivalent sliding motion restricted to the sliding surface is robustly stabilizable with H ∞ disturbance attenuation level γ under a hysteresis switching law; the other phase is to design variable structure controllers of subsystems to drive the state of the switched system to reach the single sliding surface in finite time and remain on it thereafter. A numerical example is given to illustrate the effectiveness of the proposed method.

Origin of hysteresis in resistive switching in magnetite is Joule heating

In many transition-metal oxides the electrical resistance is observed to undergo dramatic changes induced by large biases. In magnetite, ${\text{Fe}}_{3}{\text{O}}_{4}$, below the Verwey temperature, an electric-field-driven transition to a state of lower resistance was recently found, with hysteretic current-voltage response. We report the results of pulsed electrical conduction measurements in epitaxial magnetite thin films. We show that while the high- to low-resistance transition is driven by electric field, the hysteresis observed in $I\text{\ensuremath{-}}V$ curves results from Joule heating in the low-resistance state. The shape of the hysteresis loop depends on pulse parameters and reduces to a hysteresis-free ``jump'' of the current provided thermal relaxation is rapid compared to the time between voltage pulses. A simple relaxation-time thermal model is proposed that captures the essentials of the hysteresis mechanism.

Neural Network and Bandless Hysteresis Approach to Control Switched Capacitor Active Power Filter for Reduction of Harmonics

This paper proposes a combination of neural network and a bandless hysteresis controller, for a switched capacitor active power filter (SCAPF), to improve line power factor and to reduce line current harmonics. The proposed active power filter controller forces the supply current to be sinusoidal, in phase with line voltage, and has low current harmonics. Two main controls are proposed for it: neural network detection of harmonics and bandless digital hysteresis switching algorithm. A mathematical algorithm and a suitable learning rate determine the filter's optimal operation. A digital signal controller (TMS320F2812) verifies the proposed SCAPF, implementing the neural network and bandless hysteresis algorithms. A laboratory SCAPF system is built to test its feasibility. Simulation and experimental results are provided to verify performance of the proposed SCAPF system.

The Effect of Oxygen Annealing on the Resistance Switching Properties of the La<sub>0.7</sub>Ca<sub>0.3</sub>MnO<sub>3</sub> Films

A series of La0.7Ca0.3MnO3 films are fabricated by pulsed laser deposition under controlling the oxygen partial pressure or adding an oxygen post-annealing process. The film after oxygen post-annealing shows an orientation change and has more non-lattice oxygen near the surface than those of the films without annealing. Moreover, only the structure of Ag/La0.7Ca0.3MnO3/Pt with the oxygen annealed film behaves a big current-voltage hysteresis and stable resistance switching properties by applying voltage pulse. Experimental results indicate that the increase of non-lattice oxygen content induced by oxygen annealing in the vicinity of the Ag/La0.7Ca0.3MnO3 interface contributes to the occurrence of resistance switching. And with the accurate controlling of the oxygen annealing parameters, the improvement of resistance switching property of the La0.7Ca0.3MnO3 film can be expected.

Investigation and Improvement of Torque Response of Control System Based on Direct Torque Control in Interior Permanent Magnet Synchronous Motors

In this study, we investigate the torque response of a control system that is based on the direct torque control (DTC) principle for an interior permanent magnet synchronous motor (IPMSM). We also propose a gain-scheduling method for improving the torque response. Reference flux vector calculation (RFVC) DTC is used in this study. In RFVC DTC, a PI controller is used for torque control; this is in contrast to the use of the hysteresis comparator and switching table in basic DTC. In this paper, we present the relationship between the torque response and the gain of the PI controller. This relationship is derived by using the transfer function of the torque control loop. In this study, we also examine the difference between the torque responses of two motors that have different machine parameters. The proposed method can be used to realize a torque response that is independent of the operating torque. The simulation results and experimental results presented in this paper show the validity of the derived relationship as well as the effectiveness of the proposed method.