Variable Hysteresis Research Articles

Seismic performance assessment of RC bridge piers with variable hysteresis performance dampers

A novel variable hysteresis performance damper (VHD)—multi-stage slip friction damper is developed and applied to implement multi-level seismic resistance of structures. Different from the conventional slip friction dampers, which feature only a single type of slip friction surface, this innovative damper incorporates two types: a flat slip surface and a wedge slip surface. The quasi-static cyclic loading tests of the VHD were carried out to investigate its variable hysteresis performance. The test results revealed that the developed damper presented excellent adaptive performance, and its hysteresis behavior changed from a complete rectangle with efficient energy dissipation to a flag-shaped curve with exceptional self-centering capacity as deformation increases. Subsequently, the developed VHD with unique adaptive performance was applied in RC bridge piers (BP) to improve the seismic performance. Nonlinear time history and fragility analysis methods were employed to assess the seismic performance of the RC bridge piers with VHDs (BP-VHD) in deterministic and probabilistic manners, considering maximum and residual deformations as performance indicators. For comparison, seismic responses of RC bridge piers with traditional buckling restrained braces (BRBs) and self-centering energy dissipation braces (SCEBs) were also presented. The analysis and comparison results demonstrate that the developed VHD is as effective as BRB in reducing maximum deformation at small PGAs, meanwhile, it can effectively reduce the residual deformation of the structure to allowable values when the PGA is large. Furthermore, the failure probability of BP-VHDs is lower compared to piers with BRBs and SCEBs, particularly concerning maximum and residual drift ratios as performance indicators. The application of the VHD can effectively achieve the goal of multi-level seismic resistance for RC bridge piers.

Dual Mode Optoelectronic Devices Based on 2D Single Crystalline VO2 Films with Controlled Metallic Domain Regime Induced Variable Hysteresis

AbstractThe multimode optoelectronic operation in a single component device is an attractive design strategy for future optoelectronics, which demands unique and complex multifunction. Here, a novel dual‐mode optoelectronic device with both memory and switching functionalities by utilizing alternating metallic stripe domain regime‐induced controllable hysteresis of two dimensional (2D)‐crystalline VO2 films is reported. It is found that the formation and disappearance of tensile strain‐induced metallic stripe domain arrays are susceptible to temperature‐induced thermal energy, allowing controllable hysteresis in electric field‐induced metal‐insulator transition (E‐MIT) by tuning the total region of aligned metallic stripe domains within the VO2 films through current flow‐induced thermal energy. Based on the tunable hysteresis in E‐MIT, the 2D‐crystalline VO2 film‐based device exhibits successful multimode optoelectronic memory and switching operations. The device with a large hysteresis width exhibits high‐performance optoelectronic memory behavior with a high on/off ratio of up to ≈55% and a long retention time over 5000 s response to a light pulse optically triggering MIT. On the other hand, the 2D‐crystalline VO2 film device with a narrow hysteresis width exhibits high performance of photodetection with a responsivity of 316 mA W−1 and response times of ≈1.2 and ≈2 µs at rise and fall, respectively.

Improved Edge Detection using Variable Thresholding Technique and Convolution of Gabor with Gaussian Filters

Medical Field, Robotic vision, Pattern recognition, Hurdle detection, and smart city are examples of areas that require image processing to achieve automation. Detecting an edge is an important stage in any computer vision application. The performance of the edge detecting algorithm is largely affected by the noise present in an image. An Image with a low signal-to-noise ratio (SNR), imposes a challenge to locate its edges. To improve the observable image boundaries, an adaptive filtering technique is proposed in this article. The proposed algorithm uses convolution of Gabor filter with Gaussian (GoG) operator to clean the noise before non-Maxima suppression. Furthermore, using variable hysteresis thresholding can further improve edge locating. The implementation of the algorithm was done by Python and Matlab. The obtained results were compared to a number of reviewed algorithms such as the Canny method, Laplacian of Gaussian, The Marr-Hildreth method, Sobel operator, and the Haar wavelet-based method. Three performance factors were used; PNSR, MSE, and processing time. The simulation result shows that the proposed method has higher PNSR, lower MSE, and shorter processing time when compared to the Canny detector, the Marr-Hildreth, Haar wavelet-based, Laplacian of Gaussian, and the Sobel operator methods. The higher PNSR, lower MSE, and shorter processing time mean improved edge details of the processed image.

Investigations on Variable and Constant Switching Frequency Hysteresis Controller for VSI fed IM drive

Investigations on Variable and Constant Switching Frequency Hysteresis Controller for VSI fed IM drive

On-off cycling model featured with pattern recognition of air-to-water heat pumps

The air-to-water heat pump (AWHP) works frequently under partial load and suffers frequent on–off cycles in practical application. The concomitant efficiency degradation can be up to 25%, while the existing simulation work of the AWHP heating system lacks full and accurate consideration of the cycling losses. Based on the field-trial data driving and verification, an artificial neural network (ANN) model featured with pattern recognition is established to simulate the on–off transient response of AWHP, by introducing two time stamps into the source data to distinguish the power consumption and the heating capacity are in whether the start-up stage or the steady state respectively, and then training ANNs severally with different datasets. The system model is further developed in combination with the heat balance among the building heating load, the terminal heat release rate and the AWHP heat supply rate. The Mean Absolute Percentage Error within the start-up stage and the overall period could be controlled no more than 11% and 6% respectively. This study provides a reliable platform for cycling losses analysis and control strategy optimization. A variable hysteresis control algorithm of supply water temperature was conducted. By enlarging the control dead band, the on–off cycles could be reduced by 75.2%, the system coefficient of performance could be raised from 1.82 to 2.09 (increased by 14.6%) and the system power consumption could be reduced from 80.5kWh/d to 60.2kWh/d (decreased by 18.9%).

An improved hysteresis current control scheme during grid voltage zero‐crossing for grid‐connected three‐level inverters

AbstractFor three‐level inverters, hysteresis current control (HCC) has been widely used in applications such as active power filters due to its fast‐dynamic response, and it does not need to control each frequency separately with multiple controllers, which makes it simpler. However, the large fluctuation range of switching frequency is a serious disadvantage of hysteresis current control. Especially, the switching frequency decreases significantly during grid voltage zero‐crossing. This frequency fluctuation will cause low‐frequency harmonics. The purpose of this paper is to propose a sampling compensation scheme, which can solve the problem of switching frequency fluctuation near the zero‐crossing of grid voltage. Based on the variable hysteresis band strategy, the virtual sampling and switching time prediction algorithm is designed, which does not need to increase the sampling frequency or add additional controller. Therefore, nearly fixed switching frequency can be achieved while maintaining the control performance. Both simulation and experimental tests have verified the efficacy of the proposed scheme.

Rock magnetic evidence for a middle Holocene transition in marine sediments from La Paz basin, southern Gulf of California

Results of a rock magnetic study of a marine sediment core from La Paz Basin are used to investigate the Holocene paleoclimate in the Gulf of California. Chronological control based on AMS radiocarbon dating shows that the sequence covers the past ~7650 cal yr BP. The coercivity, magnetization intensity, susceptibility and magnetic hysteresis loops point to dominant fine-grained magnetite and titanomagnetites as main magnetic carriers. In the magnetic hysteresis ratio plot, magnetization and coercivity ratios fall in the pseudo-single domain field. High magnetic susceptibilities and magnetization intensities characterize the upper core section, with lower values downcore on a low amplitude oscillation trend. The late Holocene is marked by low susceptibilities, frequency-dependent, paramagnetic slope factors and variable hysteresis parameters with low Mr/Ms magnetization ratios, low Bc and Bcr coercivities and high Bcr/Bc ratios. The lower core section in the ~7650-5000 cal yr BP interval shows increased susceptibilities as compared to the upper sections with lower values. The magnetic hysteresis logs for the interval around 5000-4000 cal yr BP show some samples with distinct lower magnetization (Mr/Ms) and higher coercivity (Bcr/Bc) ratios, which characterize the interval from the downcore variation trend. The pattern in the magnetic properties is interpreted in terms of a change in precipitation from high to low humidity from the middle to the late Holocene. The sediment section records a middle Holocene climate transition in the southern Gulf ~5000-4000 cal yr BP, supporting a northward migration of climate patterns along the western North America margin, from the southern Gulf of California to Alaska.

Research on Hysteresis Modeling and Compensation Method of Giant Magnetostrictive Force Sensor

Linearity is an important index for evaluating the performance of various sensors. Under the Villari effect, there may be some hysteresis between the input force and the output voltage of a force sensor, meaning that the output will be multivalued and nonlinear. To improve the linearity and eliminate the hysteresis of such sensors, an output compensation method using a variable bias current is proposed based on the bidirectional energy conversion mechanism of giant magnetostrictive material. First, the magnetization relationship between the input force, bias current, and flux density is established. Second, a nonlinear neural network model of the force‐magnetization hysteresis and a neural network model for the compensation control of the force sensor are established. These models are trained using the magnetic flux density‐force curve and the magnetic flux density‐current curve, respectively. Taking the optimal linearity as the objective function, the bias current under different input forces is optimized. Finally, a bias current control system is developed and an experimental test platform is built to verify the proposed method. The results show that the proposed variable bias current hysteresis compensation method enables the linearity under the return of the force sensor to reach 1.6%, which is around 48.3% higher than under previous methods. Thus, the proposed variable bias current method effectively suppresses the hysteresis phenomenon and provides improved linearity for giant magnetostrictive force sensors.

Field experimental investigation on partial-load dynamic performance with variable hysteresis control of air-to-water heat pump (AWHP) system

The air-to-water heat pump (AWHP) is one of the recommended approaches for clean energy heating in the ‘coal-to-electricity’ project among rural areas of northern China. To improve the dynamic performance under its frequent partial load conditions, a variable hysteresis control algorithm of the AWHP supply water temperature was proposed, where the lower dead band (ΔTs,set-) increases piecewise with increasing outdoor air temperature. A field experiment was conducted based on a variable frequency AWHP system of a rural household in Beijing for effect investigation. The system coefficient of performance (COPsys) can be improved on the premise of ensuring the heating effect, and the optimization effect becomes better with higher outdoor air temperature. The increase of ΔTs,set- can decrease the on–off cycling times, reduce the total running time and increase the proportion of the high-load-rate running period. Two control algorithms were proposed for application suggestions. Compared with the default constant hysteresis setting, COPsys could be increased by 12–36% under low load conditions. For the 2019–2020 heating season, the seasonal power consumption could be reduced by 7–15% and the seasonal COPsys could be increased by 8–17%. This paper provides a convenient and low-cost optimization scheme for energy saving.

Efficient Control of Induction Motor Current in a Frequency-Controlled Electric Drive

An analysis of methods for controlling the current of an asynchronous electric motor in a frequency-controlled electric drive is performed. The disadvantages of a control system with relay current controllers that provide system operation in the “current corridor” mode are shown. Such disadvantages as increased thermal losses in the transistors of the frequency converter are caused by the unstable switching frequency of the motor current. The relevance of the principles of current control using the predictive model to form control actions in the frequency converter circuit with relay controllers is noted. A method of current control in an asynchronous electric drive is considered that makes it possible to stabilize the switching period of the inverter power switches when controlling the current in the motor. To obtain this result, it is proposed to influence the width of the hysteresis loop of the relay current controllers and form it depending on the parameters of the load circuit. The required accuracy of the current control is maintained. The structure of the control system is proposed, in which the considered method is implemented. A key element of the system is a computing unit that generates signals that set the required width of the hysteresis loop of the relay controllers. The method of predicting changes in the controlled current after the next switching of transistors in the inverter of the frequency converter of the electric drive is the analytical basis of the calculations. Analytical expressions providing the calculations necessary for the computing unit operation are presented. The effect of applying the relay current controllers with variable hysteresis in the control system of a frequency-controlled electric drive is shown.

Magnetism and Charge Order in Nanocrystalline Orthorhombic SrFeO3-δ

Orthorhombic SrFeO3-δ is synthesized through solid-state reaction in nanocrystalline form with controlled oxygen flow. Neutron diffraction measurement with Rietveld refinement and selected area electron diffraction (SAED) confirms the crystal structure. Magnetization against temperature shows that orthorhombic SrFeO3-δ is an antiferromagnet with Neel temperature (TN) of 230 K. Field-cooled hysteresis (M-H) measurements show exchange bias present in this system. It undergoes charge ordering near the Neel temperature and large change in resistivity around TN is found. Behavior of transport and magnetotransport properties are understood using the three-dimensional variable range hopping (3DVRH) mechanism and hysteresis is observed around TN in transport data. Ferromagnetic resonance (FMR) study shows that the linewidth is minimum around TN. Charge order and magnetic phase transition are coupled to each other around TN in the orthorhombic SrFeO3-δ system.

Optimization of Torque Tracking Performance for Direct-Torque-Controlled PMSM Drives With Composite Torque Regulator

In this article, a composite torque regulator is proposed for optimizing the torque tracking performance in direct torque-controlled permanent-magnet synchronous motor drives. In the proposed composite torque regulator, two new variable hysteresis bands are designed and combined with two constant hysteresis bands. In the conventional direct torque control (DTC) scheme, the torque increasing rate and decreasing rate are changed with different speeds and loads. Thus, the average torque will deviate the reference torque seriously under some operation states. With torque deviation, the reference torque can hardly reflect the actual electromagnetic torque, and the torque tracking becomes more difficult and unsatisfactory in dynamic process. On the other hand, the time delay of one sampling period further deteriorates the precision of torque tracking. By introducing the proposed composite torque regulator, both torque deviation and the impact of time delay on the torque ripple can be eliminated. In addition, the advantages of the conventional DTC scheme, namely low switching frequency, fast dynamic response, simple structure, and independence of motor parameters, can be reserved in the proposed DTC scheme with a composite torque regulator. Experimental results are presented to verify the effectiveness of the proposed scheme and compare its performance with the conventional DTC scheme.

The impact of hydrograph variability and frequency on sediment transport dynamics in a gravel‐bed flume

AbstractA laboratory study was undertaken to investigate how changes in flow regime and hydrograph shape (number of cycled hydrographs and duration of each hydrograph) together impact bedload transport and resulting bed morphology. Three hydrologic conditions (experiments) representing different levels of urbanization, or analogously different flow regimes, were derived from measured hydrometric field data. Each experiment consisted of a series of hydrographs with equal peak discharge and varying frequency, duration and flashiness. Bedload transport was measured throughout each hydrograph and measurements of bed topography and surface texture were recorded after each hydrograph. The results revealed hysteresis loops in both the total and fractional transport, with more pronounced loops for longer duration hydrographs, corresponding to lower rate of unsteadiness until reaching the peak discharge (pre‐urbanization conditions). Shorter duration hydrographs (urban conditions) displayed more time above critical shear stress thresholds leading to higher bedload transport rates and ultimately to more variable hysteresis patterns. Surface textures from photographic methods revealed surface armoring in all experiments, with larger armor ratios for longer duration hydrographs, speculated to be due to vertical sorting and more time for bed rearrangements to occur. The direction of bed surface adjustment was linked to bedload hysteresis, more precisely with clockwise hysteresis (longer hydrographs) typically resulting in bed coarsening. More frequent and shorter duration hydrographs result in greater relative channel adjustments in slope, topographic variability and surface texture. © 2019 John Wiley & Sons, Ltd.

A novel deformable lung phantom with programably variable external and internal correlation.

Lung motion phantoms used to validate radiotherapy motion management strategies have fairly simplistic designs that do not adequately capture complex phenomena observed in human respiration such as external and internal deformation, variable hysteresis and variable correlation between different parts of the thoracic anatomy. These limitations make reliable evaluation of sophisticated motion management techniques quite challenging. In this work, we present the design and implementation of a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers. An in-house-designed lung module, made from natural latex foam was inserted inside the outer shell of a commercially available lung phantom (RSD, Long Beach, CA, USA). Radiopaque markers were placed on the external surface and embedded into the lung module. Two independently programmable high-precision linear motion actuators were used to generate primarily anterior-posterior (AP) and primarily superior-inferior (SI) motion in a reproducible fashion in order to enable (a) variable correlation between the displacement of interior volume and the exterior surface, (b) independent changes in the amplitude of the AP and SI motions, and (c) variable hysteresis. The ability of the phantom to produce complex and variable motion accurately and reproducibly was evaluated by programming the two actuators with mathematical and patient-recorded lung tumor motion traces, and recording the trajectories of various markers using kV fluoroscopy. As an example application, the phantom was used to evaluate the performance of lung motion models constructed from kV fluoroscopy and 4DCT images. The phantom exhibited a high degree of reproducibility and marker motion ranges were reproducible to within 0.5mm. Variable correlation was observed between the displacements of internal-internal and internal-external markers. The SI and AP components of motion of a specific marker had a correlation parameter that varied from -11 to 17. Monitoring a region of interest on the phantom's surface to estimate internal marker motion led to considerably lower uncertainties than when a single point was monitored. We successfully designed and implemented a programmable, externally and internally deformable lung motion phantom that allows for a reproducible change in external-internal and internal-internal correlation of embedded markers.

Prediction and experiment of DC- bias iron loss in radial magnetic bearing for a small scale turbomolecular pump

Iron loss calculation is a crucial part of turbomolecular pump design, since the molecular pump works in vacuum environment and the iron loss eventually transforms into thermal radiation. In this paper, an iron loss prediction model for a radial magnetic bearing of turbomolecular pump considering temperature influence is proposed. A ring specimen test under different dc-bias current, different frequencies, flux densities and temperatures are used to measure iron loss of steel laminations. Then, an iron loss model with variable hysteresis loss coefficients, eddy-current loss coefficients and dc-bias loss coefficients is used for iron loss calculation of the magnetic bearing. Flux densities of different part of magnetic bearing under different working states are obtained by using FEM. Finally, the measurement and subtraction method of iron loss in radial magnetic bearing is proposed, the accuracy the proposed iron loss model is validated by an iron loss test on a prototype of a 300 L/s 36000 r/min turbomolecular pump supported by magnetic bearing.

Voltage Compensation Using Dvr with Modified Switching Band Control

This paper presents mitigation of voltage related Power Quality (PQ) issues by using Dynamic Voltage Restorer (DVR). Three phase four wire DVR with modified switching band controller is proposed. A modified filter circuit band controller is proposed for reducing the switching losses, constant switching frequency maintenance and corresponding simulation studies are carried out. Variable hysteresis band (modified band) controller generates accurate injected voltages by using system parameters and low error value between reference injected voltages, actual injected voltages can be achieved, which helps in smoothening and minimizing ripples in PCC (Point of common coupling) voltages. The obtained simulation results are presented.

Using low‐cost microcontrollers to implement variable hysteresis‐width comparators for switching power converters

Hysteretic comparators are often used to implement sliding-mode controllers or other type of discontinuous regulators for power switching converters. Their design is usually performed analogically yielding robust and fast controllers that can even allow converter operation with high values of duty cycle. A new analogue implementation based on a low-cost microcontroller is described in this study showing the mentioned advantages plus the flexibility of a programmable digital system. The proposed comparator employs some microcontroller peripherals without consuming execution time of the control algorithm and without requiring interruption management. It provides variable hysteresis width to obtain constant switching frequency in sliding-mode strategies and can be used in any type of hard switching converter. The dynamic performance of the method is verified experimentally in a boost converter-based rectifier with power factor correction and output voltage regulation in one single stage. The boost converter operates in sliding mode with constant switching frequency and results in a total harmonic distortion of the input current <1%.

Variable Structure Control in Natural Frame for Three-Phase Grid-Connected Inverters With LCL Filter

This paper presents a variable structure control in natural frame for a three-phase gird-connected voltage-source inverter with LCL filter. The proposed control method is based on modifying the converter model in natural reference frame, preserving the low-frequency state-space variables dynamics. Using this model in a Kalman filter (KF), the system state-space variables are estimated allowing us to design three independent current sliding-mode controllers. The main closed-loop features of the proposed method are: first, robustness against grid inductance variations because the proposed model is independent of the grid inductance; second, the power losses are reduced since physical damping resistors are avoided; third, the control bandwidth can be increased due to the combination of a variable hysteresis comparator with the KF; and fourth, the grid-side current is directly controlled providing high robustness against harmonics in the grid. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.

Improving the Dimming Performance of Low-Power Single-Stage AC–DC HBLED Drivers

The design of efficient single-stage high-brightness light-emitting diodes (HBLEDs) ac–dc drivers with power factor correction (PFC) in low-power applications is addressed in this paper. The PFC is achieved by using a switching converter with both step-up and step-down voltage capability. It is well known that a good tracking of the input reference current close to the zero crossing is challenging, in particular when the LED output current is low, hence jeopardizing the power quality at low power levels. A solution is proposed to improve the power quality in ac–dc LED drivers under inner current loop based on a variable hysteresis modulation scheme. An adaptive hysteresis window modulated by the input voltage and the output LED current reference is used. The double modulation strategy helps to avoid the distortion near the zero crossings of the input current and to improve the dimming performance of the HBLEDs. This results in a low value of total harmonic distortion (THD) under low current/power conditions and therefore in a very good dimming performance in single-stage ac–dc HBLEDs drivers with PFC. The operation principle of the proposed technique is presented and numerical simulations are shown to demonstrate its functionality. A laboratory prototype is designed and tested to verify its feasibility obtaining a significant improvement in terms of power quality. Under universal input voltage operation, good efficiency and low THD can be achieved even for low power levels.

Sampled-Time-Domain Analysis of a Digitally Implemented Current Controlled Inverter

This paper presents a sampled-time-domain analysis to investigate the sampling effect on instantaneous switching frequency of a digitally implemented hysteresis current control (HCC) in a voltage source inverter (VSI). The generalized expression of the instantaneous switching frequency with the consideration of sampling frequency has been derived. The effect of variation in sampling frequency on effective hysteresis band and switching frequency has been analyzed. The difference between maximum to minimum switching frequency of a fixed-band HCC VSI depends on the sampling frequency of the digital controller. The sampling also generates a steady-state tracking error exceeding the fixed-band limit at the fundamental frequency for fixed hysteresis band operation. The analysis has been done to achieve fixed switching frequency with variable hysteresis band and with varying sampling period. The frequency spectrum of the load current is presented to show the effect of a digital controller. The sampling effect on the switching performance has been demonstrated for a single-phase VSI under different loading conditions. To verify the analytical results, the simulation and experimental results are obtained with the current controller implemented on a field programmable gate array-based digital controller.