Hysteresis Switching Research Articles

Development of a Robust Random Switching Hysteresis PWM Inverter for Linear Positioning Control

Robust random switching control for a three-phase hysteresis current-controlled PWM inverter to promote its ability in servo driving control is studied in this paper. After observing the effect of varying band on the output harmonic distribution characteristic of a hysteresis current-controlled PWM inverter, a random switching hysteresis PWM scheme is developed. A robust spectrum shaping technique is devised such that the randomized inverter output harmonic spectrum is further shaped to the desired pattern. In the resulted frequency spectrum, the magnitudes of lower-frequency harmonics are reduced significantly. This makes the hysteresis PWM inverter suitable to serve as a driving source for position servo motor drives. The effect of AC motor neutral point isolation on the random switching performance is observed. The developed random switching inverter is used to power a linear permanent magnet synchronous motor-driven magnetic suspended positioning stage, and the resulted position control performance is demonstrated by some simulated and measured results.

Electrochemical and Raman studies on the redox switching hysteresis of polyaniline

Cyclic voltammetry (CV), impedance spectroscopy, and Raman spectroscopy were used to characterize the redox switching hysteresis of polyaniline (PANI) in aqueous acid solutions. The polymer was prepared electrochemically. Polyaniline with various counterions: chloride, trichloroacetate, perchlorate, was studied. It was found that the hysteresis of the switching process depends on the electrolyte used for a switching performance. It increases in the order: trichloroacetic acid, perchloric acid, hydrochloric acid. The hysteresis is determined by the counterion used in the switching performance and it seems to be not dependent on a counterion history of the polymer. Effective charge diffusion coefficients follow changes in the basicity of the counterion. Raman spectra of the primary counterion–polyaniline differ for the chloride and perchlorate counterions. Raman spectroscopy reveals a stronger interaction with the secondary counterion in the polyaniline–perchlorate system than in the polyaniline–trichloroacetate system.

X-ray-induced phase transformation in congruent and vapor-transport-equilibrated lithium tantalate and lithium niobate

We have discovered an effect of a partially reversible x-ray-induced increase of diffuse x-ray scattering in both congruent and vapor-transport equilibrated single-crystalline lithium niobate and lithium tantalate. The effect has been attributed to x-ray-induced decay of the ferroelectric phase at room temperature. The x-ray-induced change of the switching current and hysteresis loops observed is in accord with this assumption.

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

This paper presents an indirect adaptive stabilization scheme forfirst-order continuous-time systems under saturated input which isdescribed by a sigmoidal function. The singularities are avoided througha modification scheme for the estimated plant parameter vector so thatits associated Sylvester matrix is guaranteed to be nonsingular andthen the estimated plant model is controllable. The modificationmechanism involves the use of a hysteresis switching function. Analternative hybrid scheme, whose estimated parameters are updated atsampling instants is also given to solve a similar adaptivestabilization problem. Such a scheme also uses hysteresis switching formodification of the parameter estimates so as to ensure thecontrollability of the estimated plant model.

V-shaped switching in binary mixtures of an achiral swallow-tailed material with the antiferroelectric liquid crystal (S)-MHPOBC

An achiral swallow-tailed material, 2-propylpentyl 4-(4′-decyloxybiphenyl-4-carbonyloxy)benzoate, p, showing SmA and SmCalt phases was prepared for mixing (by weight percentage) with an antiferroelectric liquid crystal, (S)-MHPOBC, m, for the study. The binary mixture p/15/m85 using (S)-MHPOBC (85%) as a host doped with achiral material (15%) resulted in a phase sequence SmA-SmC*-SmC*A. The electro-optic response of this mixture in the ferroelectric SmC* phase displayed V-shaped switching, while that in the antiferroelectric SmC*A phase displayed a double hysteresis switching. The mixture p85/m15 possessed SmA* and SmC*A phases; V-shaped switching was found in the antiferroelectric SmC*A phase of this mixture. These optical phenomena implied that a binary mixture containing a larger amount of achiral swallow-tailed material and/or possessing relatively lower polarization favours the occurrence of V-shaped switching in the antiferroelectric phase. The results of this work also suggested that thresholdless V-shaped switching in chiral smectic liquid crystals can be achieved by mixing an achiral swallow-tailed material with an antiferroelectric liquid crystal.

ON SUPERVISORY CONTROL OF LINEAR SYSTEMS WITH INPUT CONSTRAINTS

A supervisory control system which globally regulates to zero the state of a very poorly modeled linear process in the presence of input constraints is proposed in this paper. The model of the process is an unknown member of a family of systems which are open-loop unstable but not exponentially unstable. For the analysis, two switching logics are considered: The hysteresis switching logic and a new type of dwell time switching logic. In both cases, the supervisory control system is shown to regulate to zero all the continuous states of the system.

Electro-Optical Studies on Polymer Dispersed Liquid Crystal Composite Films. II. Composite of PVB/E44 and PMMABA/E44

Aggregation states and electro-optical effects based on light scattering have been investigated for PVB/E44 and PMMABA/E44 composite films. The composite films were prepared by solvent-evaporation technique. Scanning electron microscopy observations showed that E44-phase is continuously embedded in a sponge-like PVB and PMMABA matrix polymers. Electro-optical responses of the composite films under the conditions of an externally applied AC electric field (0-240 Vp-p; 50, 100, 500 and 1 KHz) temperature (28°C) and film thickness (10±2μm) were determined using He-Ne (wavelength 632.8 nm) laser as a light source. The composite films (of both PVB/E44 and PMMABA/E44) with positive dielectric anisotropy exhibited characteristic reversible light scattering-light transmission switching, strongly dependent on the liquid crystal (LC) channel size and shape in the composite films. The electro-optical response of LC molecules in both of the composite systems is influenced by the miscibility of the LC molecules at LC-polymer interface. Thus the distribution of relaxation time for the interfacial polarization corresponds to the miscibility state at the interface between matrix polymer and LC. The miscibility between two phases at interface was investigated by employing Fourier-Transform Infrared Spectroscopy/Attenuated Total Reflectance (FT-IR/ATR) spectrophotometry and differential scanning calorimetry (DSC). The results obtained indicate that under the conditions imposed the output can be controlled and the response time is on the order of several milliseconds or less. A memory effect is observed in PVB/E44 composite films. The transmittance of the memory state is preserved for a longer time after an applied voltage is removed, which can be erased to the scattering OFF state by heating the film to the E44-clearing temperature. In the case of PMMABA/E44 composites, which exhibit electro-optical switching hysteresis, a possible mechanism that the applied electric field-induced phase-mixing of PMMABA and E44 would be a main cause of hysteresis is discussed.

Features of two rate-dependent hysteresis models

Two rate-dependent models of ferromagnetic hysteresis are compared and their features illustrated by examples. An internal dynamic generalization of the classical Preisach model (CPM) replaces the ideal hysteresis switches of the CPM by operators with outputs that change at a finite rate. The external dynamic model uses the CPM as it is, but delays its input with respect to the actual field strength variation. The behavior of the two models in identical conditions are compared and their performance evaluated in terms of complexity of numerical implementation, possibility of parameter identification, ability to reproduce—and, of course, predict—experimental results, computational speed and memory requirement.

KINETICS OF THE TRANSITION BETWEEN FERROELECTRIC AND ANTIFERROELECTRIC STATES IN LIQUID-CRYSTALLINE MIXTURES

Investigations of a mixture with induced antiferroelectric phase are described. This mixture exhibits large thermal hysteresis of the transition between ferroelectric and antiferroelectric phases, which was demonstrated using dielectric and optical methods. The kinetics of the transition from the ferroelectric to the antiferroelectric state was extremely slow — its time constant ranged from few minutes to many hours, depending on temperature. The rate of transition formally obeys the Avrami equation describing the kinetics of phase transitions from a supercooled state. However, the remarkably small exponent suggests, that the Avrami model is not suitable for description of the investigated transition. The coexistence of ferroelectric and antiferroelectric states was noticed in a broad temperature range. In the same range the V-shaped switching was observed. The observed phenomena: hysteresis, slow kinetics and threshold-less switching are probably caused by competition of ferroelectric and antiferroelectric interactions acting between smectic layers.

Phase Stability and Ferroelectric Properties of Lead Strontium Zirconate Titanate Ceramics

The effect of compositional modifications on the field‐induced phase‐transition behavior and dielectric properties of strontium‐doped lead zirconate titanate (PZT) ceramics was studied. PZT compositions with different strontium and titanium contents, within the general formula Pb1–xSrx(Zr1–yTiy)O3 and located in the tetragonal antiferroelectric (AFE) and rhombohedral ferroelectric (FE) phase fields were prepared by tape casting and sintering. X‐ray diffraction and polarization measurements were used to locate compositions suitable for investigation of the field‐induced AFE–FE phase transition. The results indicated that a higher Sr2+ content decreased the polarization and hysteresis and increased the switching field; a lower Ti4+ content decreased the polarization and increased the switching field and hysteresis. A high room‐temperature dielectric constant was obtained for compositions near the phase boundary. These results suggest that a combination of both A‐site and B‐site modifications can be used to tailor ferroelectric properties, such as the switching field and hysteresis, of these strontium‐doped PZTs displaying a field‐induced AFE–FE phase transition.

Wigner Function Methods in Modeling of Switching in Resonant Tunneling Devices

Issues associated with modeling of quantum devices within the framework of the transient Wigner equation are addressed. Of particular importance is the structure of the Wigner function, hysteresis, and device switching time, whose value is determined by the large signal device properties.

Comparison of sputtered SBTN and PLZT thin film capacitors for FRAM applications

Thin films of the solid solution SrBi2Ta2O9-SrBi2Nb2O9 (SBTN) and Ca and Sr doped (Pb, La)(Zr, Ti)O3 (PLZT) were prepared by conventional, single target, rf-magnetron sputtering. The films were deposited onto Pt coated substrates with a diameter of 6 inches. The electrical properties were characterized by hysteresis and pulsed field switching measurements. A ferroelectric performance comparison between two types of capacitors will be presented. The recent improvement in PLZT capacitor processing have greatly extended fatigue resistance beyond what is usually observed and reported for SBTN capacitors.

Robust hysteresis current-controlled PWM scheme with fixed switching frequency

A robust hysteresis current-controlled PWM scheme is presented, having constant switching frequency for a single-phase inverter with a wide frequency range. An intuitive analysis for the harmonic spectrum characteristic of the hysteresis control PWM inverter is made prior to developing the proposed switching control approach. According to the operating frequency and load nature of inverter, the variation range of the hysteresis band for achieving the desired constant switching frequency is determined, and the hysteresis switching mechanism is devised. Next, the filter design, in accordance with the inverter output frequency feature and the load requirement, is described. In addition, a simple robust controller is proposed to improve the constant frequency control performance and thus to reduce the effect of inverter output harmonics on the load operating characteristics. The proposed hysteresis PWM scheme is applied to an inverter-fed electrodynamic shaker, and its effectiveness is verified by simulation and experimental results.

Characterization of metalorganic decomposition-derived SrBi2Ta2O9 thin films with different thicknesses

Ferroelectric capacitors having sputtered Pt bottom and top electrodes and metalorganic decomposition derived ferroelectric thin films of SrBi2Ta2O9 (SBT) were prepared. The thickness effects on the structure, surface morphology, and electrical properties of SBT thin films were studied and discussed. Structure and surface morphology were analyzed by x-ray diffraction and atomic force microscope. The electrical properties were characterized by the measurements of hysteresis, capacitance, and pulse switching. The crystalline structure, grain size, and electrical properties do not depend on film thickness when films are less than 440 nm thick. A larger grain size is observed for films thicker than 440 nm, which results in a larger remnant polarization. The thickness dependence of the coercive voltage and reciprocal capacitance can be explained by an interfacial layer model. The thickness-independent coercive field and dielectric constant, calculated from the interfacial layer model, are around 19 kV/cm and 343, respectively. Nonvolatile polarization (Pnv), obtained from pulse-switching measurements, increases with the applied electric field and finally saturates with a slight thickness effect. The relaxation of the remnant polarization that occurs at zero-voltage intervals between the pulses and the thickness-independent behavior of Pnv are explained based on depolarization fields within the ferroelectric due to nonswitching interfacial layers at the film/electrode interfaces.

Stochastic simulation of processive and oscillatory sliding using a two-headed model for axonemal dynein.

Computer simulations have been used in an attempt to understand experimental observations of processive and oscillatory sliding by one or a few axonemal dyneins. A simple two-headed model has been examined using stochastic simulation methods. To explain the experimental observations, the model must be capable of taking backward steps, as well as forward steps, and there must be hysteresis in switching between forward or backward stepping. When the effects of Brownian movement on motor strain are included, it is not possible to obtain oscillations as regular as the experimental records by using motor strain to regulate switching between forward or backward stepping.

Two-dimensional ferroelectrics

The minimum size for a ferroelectric crystal has not been demonstrated experimentally because of difficulties in making thin films or small particles of sufficient quality. Langmuir-Blodgett deposition of crystalline films of vinylidene fluoride copolymers has produced high quality ferroelectric films as thin as 1 nm. These films permit the ultimate investigation of the finite-size effects on the atomic thickness scale and also reveal the fundamental two-dimensional character of ferroelectricity in these materials. They exhibit the main properties of ferroelectricity: a first-order ferroelectric-paraelectric phase transition; polarization hysteresis (switching); a jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; increase of the transition temperature:with applied field; double hysteresis above the phase transition temperature: and the existence of the ferroelectric critical point. The films also exhibit a new surface-layer phase transition.

Monte-carlo simulation of the P-E hysteresis and domain switching in ferroelectric Potts lattice

A Monte-Carlo approach based on the Q-state Potts model is developed to simulate dynamic hysteresis of ferroelectric Potts lattice against periodic time-varying external field E. The dynamic responses of the hysteresis dependent of frequency ω of applied field and domain size R are studied. The P-E loop exhibits very different patterns in various ranges of frequency. Its area can be scaled with Ω-ω1/3 at low ω The remnant polarization Pr shows a maximal as a function of ω At small domain size, the dynamic hysteresis is significantly compressed, predicting ferroelectricity weakening effect at small domain size.

Effect of cobalt nanoclusters on magnetization processes in CoB amorphous alloys

The magnetization processes in Co 80B 20 and Co 75B 25 amorphous alloys have been studied by means of their hysteresis loops and switching curves at room temperature. This analysis is correlated with the structural characterization made by HRTEM which showed different microstructure in both compositions. In particular, it is proposed that the presence of cobalt nanoclusters in the composition with stoichiometry departing from Co 3B, plays a main role in the magnetic behavior.

Robust adaptive regulation of potentially inversely unstable first-order hybrid systems

This paper presents a robust adaptive stabilization scheme for a class of hybrid time-invariant linear system involving both continuous and discrete signals. The continuous subsystem and the discrete one are both of first-order. The usual assumptions of inverse stability of the plant and knowledge of the high-frequency gain are not required for this first-order hybrid system. The design philosophy used relies on the separation of the continuous and discrete dynamics by generating two additive terms to build the control action. The estimation scheme is unified in the sense that both continuous and discrete estimated parameters are generated from the same adaptation error. The controllability of the nominally estimated plant model is maintained by using an hysteresis switching function under the controllability of the nominal plant. This allows relaxing the usual assumption of stability of the plant inverse. Also, an adaptation dead zone is used for robust stabilization by using a known overbounding function of the contribution of the unmodelled dynamics.

Adaptive stabilization of first-order systems using estimates modification based on a Sylvester determinant test

This note presents an adaptive control scheme for first-order continuous-time systems subject to bounded noise and unmodelled dynamics. The estimated plant model is controllable and then the adaptive scheme is free from singularities. The estimation scheme involves the use of a relative dead zone which freezes the estimation process when the size of the prediction error is small compared to the contribution of the unmodelled dynamics. The singularities are avoided through the use of a modification of the estimated plant parameter vector so that its associated Sylvester matrix is guaranteed to be nonsingular. That property is achieved by ensuring that the absolute value of its determinant does not lie below a prefixed positive threshold. In addition, the use of a hysteresis switching function is not used for a modification of the estimates while the absence of chattering is guaranteed in the eventual case when the Sylvester determinant tends to zero. The global stability of the closed-loop system is also guaranteed.