Proposed Switching Model Research Articles

Bifurcation dynamics on the sliding vector field of a Filippov ecological system

A Filippov crop-pest-natural enemy ecological system with threshold switching surface related to the pest control is developed, which has been completely analyzed by employing the qualitative techniques of non-smooth dynamical systems. The main results reveal that the proposed switching model can have multiple pseudo-equilibria in the sliding region, which result in rich bifurcations in the sliding region including saddle-node, Hopf, Bogdanov-Takens and Hopf-like boundary equilibrium bifurcations. Moreover, the pseudo-periodic solution (or pseudo-homoclinic loop) can be generated in the sliding region through a Hopf bifurcation (or a homoclinic bifurcation), which can collide with the tangential lines at the cusp singularities and finally disappears as parameter varies. This reveals that although the system can stabilize on the sliding region to achieve the purpose of pest control, there are complex dynamical behaviors and sliding bifurcations within the sliding region. Furthermore, as the threshold level varies, the model exhibits the interesting global sliding bifurcations including grazing bifurcation, buckling bifurcation, crossing bifurcation, homoclinic bifurcation to a pseudo-saddle, period-halving bifurcation and chaotic dynamics. This implies that control outcomes are sensitive to the threshold level, and hence it is crucial to choose the threshold level to initiate control strategy.

Regime-Switched Neural Networks: Flow Stress Modeling Strategy of 310s Stainless Steel During Hot Deformation

This study examines the high temperature deformation and constitutive modeling of flow stress for 310s stainless steel. To this end, hot tensile experiments were conducted under the temperatures of 700° and 800° at the strain rates of 0.0002/s, 0.002/s, and 0.02/s. Flow stress was modeled using the Arrhenius type constitutive equation and neural network approach. Specifically, Regime-Switched Neural Networks (RSNN), a set of neural networks with switching, has been newly proposed as a better predictive model for flow stress. The modeling performance of the RSNN model was evaluated through a comparison with traditional Arrhenius-type constitutive equations and the single neural network model. The results showed that the accuracy of the proposed RSNN was substantially higher than those of the existing Arrhenius-type equations, and the prediction performance was therefore significantly improved. In addition, the accuracy of the proposed RSNN was improved by approximately more than 24% in comparison with the existing global model—a single neural network—thus confirming the superiority of the proposed switching model.

Design of model predictive force control for hydraulic servo system based on cuckoo search and genetic algorithms

This article discusses a system identification based on a black-box state-space model for an experimental electro-hydraulic servo system. Furthermore, it presents force-tracking control for the electro-hydraulic servo system based on model predictive control. The parameters of model predictive controls have been tuned by cuckoo search algorithm as well as genetic algorithm. The realization of model predictive controls depends on using a data acquisition card (NI-6014) and Simulink/MATLAB as the core of the electro-hydraulic servo system control system. In this research, the combination of model predictive control tuned by cuckoo search algorithm and genetic algorithm has been introduced in the form of switching model predictive controls. This combination collects the advantages of two model predictive controls in one model predictive control by switching model predictive controls. The simulation and experimental results display that the suggested switching of model predictive controls introduces a good tracking performance in terms of settling time, rise time, and system overshoots as compared to the two separated model predictive controls. In addition, the experimental evaluation has shown that the proposed switching model predictive controls achieved a stable and robust control system even facing to a different reference command signals (step, multistep, and sinusoidal signals). Moreover, its behavior is more robust for system parameters perturbation and small or large perturbation of disturbances in the working environment. It also achieves the necessitated physical limits of the actuator. As a general conclusion and a deep study of electro-hydraulic servo system, one can conclude that the switching strategy between model predictive control tuned by cuckoo search algorithm and by genetic algorithm has the priority of applying it on the field of electro-hydraulic servo system. The proposed new strategy (switching of model predictive control) is promising in experimental applications.

Filament Growth and Resistive Switching in Hafnium Oxide Memristive Devices.

We report on the resistive switching in TiN/Ti/HfO2/TiN memristive devices. A resistive switching model for the device is proposed, taking into account important experimental and theoretical findings. The proposed switching model is validated using 2D and 3D kinetic Monte Carlo simulation models. The models are consistently coupled to the electric field and different current transport mechanisms such as direct tunneling, trap-assisted tunneling, ohmic transport, and transport through a quantum point contact have been considered. We find that the numerical results are in excellent agreement with experimentally obtained data. Important device parameters, which are difficult or impossible to measure in experiments, are calculated. This includes the shape of the conductive filament, width of filament constriction, current density, and temperature distribution. To obtain insights in the operation of the device, consecutive cycles have been simulated. Furthermore, the switching kinetics for the forming and set process for different applied voltages is investigated. Finally, the influence of an annealing process on the filament growth, especially on the filament growth direction, is discussed.

Observation of Conductive Filament in CBRAM at Switching Moment

We observed a conductive filament in CBRAM (conductive bridging RAM) during switching operations by in-situ TEM (transmission electron microscopy) method. A vertically stacked-type CBRAM is popular for TEM observation, however, we used a lateral-type CBRAM (Cu-WOX-Cu CBRAM) for clearer TEM observations. In a Set operation (resistive switching from the high resistance state (HRS) to the low resistance state (LRS)), a conductive filament grew from a cathode to an anode and increase of Cu in the cathode was observed. After the Set operation, a Reset operation (resistive switching from LRS to HRS) was observed in the opposite voltage polarity to the former Set but big structural changes were not seen. The growth direction of Cu conductive filament and increase of Cu in the cathode after the Set can be explained by a proposed switching model of CBRAM (conductive filament model).

Enhancing the yaw stability and the manoeuvrability of a heavy vehicle in difficult scenarios by an emergency threat avoidance manoeuvre

This study aims to investigate the switching model predictive control strategy for a heavy-vehicle system in order to coordinate the actuator between active rear steering and differential braking control manoeuvres for emergency threat avoidance in difficult environments. We present the controller performances for the lateral dynamic behaviour, the yaw stability and the manoeuvrability of a vehicle when subjected to a sudden threat or disturbance such as a gust of wind, a road bank angle or a split- μ road surface in order to enable a fast safe lane-change trajectory to be followed. The vehicle was driven at a medium forward speed and a high forward speed in order to investigate the effectiveness of the proposed approach in avoiding the threat, maintaining the stability and enablinge a fast safe lane-change trajectory to be followed. We compared two different controllers (a model predictive controller and a switching model predictive controller) for two different control manoeuvres (active rear steering with differential braking control and active rear steering with direct yaw moment control). The simulation results demonstrate that the proposed switching model predictive control method provides an improved fast safe lane-change manoeuvre in a threat avoidance scenario for both control manoeuvres. It also demonstrated that the proposed active rear steering with differential braking control is more useful for maintaining the stability of the vehicle in a threat avoidance scenario with disturbance effects than is active rear steering with direct yaw moment control.

Advanced Information Technology of Slot-Switching Network Schemes for on All-Optical Variable-Length Packet

Problem statement: The purpose of this paper was to investigate all op tical packet switching, because it was the key to the success of the future Internet. It can meet the stringent bandwidth requirement of future Internet applicatio ns, such as real-time video streaming. Due to the lack of optical Random Access Memory (RAM), however, the all-optical schemes studied in the literature were either not flexible enough to accom modate Internet packets, which were variable-length in nature, or fail to schedule packets at switches to achieve low loss rate. Approach: The aim of this paper was thus to tackle the flexibility and utiliz ation issues in all-optical packet switches, even a t the absence of optical RAM. We approached this paper by first studied a new slotted model for all-optical variable-length packet switching, which was called Variable-length-Packet Fixed-Length Slot (VPFS) switching. Results: We proved by mathematical analysis the theoretical maximum utilizations that can be achieved by the model in two variant schemes. Then we proposed a new scheduling algorithm for shared-fiber-delay-line switches in order to achiev e low loss rate when the utilization approaches the maximum. We justified our design by simulation. In our finding, through mathematical analysis and computer simulation, our proposed switching model and scheduling algorithm can be coupled well to achieve good performance for all-optical packet swi tches. We also found that the selection of the slot size in the network was very critical as it determi ned the transmission overhead and hence the utilization of the all-optical network. Our resear ch limitation depended on slot size. Although a sma ll slot size was critical for high utilization with ou r model, it was not always preferable. It was becau se a small slot size increased the switching and schedul ing complexity at the switch. Thus the selection of an optimum slot size for the network was a compromise between utilization and complexity. Conclusion/Recommendations: A fast scheduling algorithm has been studied in ord er to reduce the scheduling complexity so as to increase the utiliza tion without much penalty. In regard to the practic al implications, the VPFS was a promising model to ful ly utilize the huge capacity of all-optical network s and to accommodate variable-length packets for futu re Internet traffic. With VPFS, the selection of th e slot size was critical, and it was a compromise bet ween the network utilization and scheduling complexity.

A temperature-dependent two-step domain-switching model for ferroelectric materials

Piezoelectric stack actuators are promising candidates for use in fuel injection technology. Experimental results for stack actuators have shown that a significant amount of heat is generated when they are driven under high electric-field magnitudes and/or high frequency, both of which occur in fuel injectors. They also exhibit hysteretic nonlinear behavior when driven under high electric-field magnitudes. In this paper, a new domain-switching model for PZT materials is developed. The model is based on changes in potential energy, and accounts for the temperature effect on domain switching. It also accounts for full thermo-electro-mechanical coupling. Additionally, different energy levels are assumed for different domain-switching types. It is assumed that 180° switching is a two-step process caused by two 90° switchings. A finite element implementation of a thermopiezoelectric continuum based on the proposed switching model is presented. The model shows good agreement with experimental results at different temperatures and loading conditions.

Switching characteristics of Cu2O metal-insulator-metal resistive memory

The Cu2O metal-insulator-metal (MIM) resistive switching memory was characterized on a 64kb memory test array. The switching properties are consistent with the proposed switching model of conductivity modulation by a charge trapping process. Retention, programing characteristics, and temperature effects are analyzed based on the switching model. The measured characteristics and the switching model for Cu2O MIM are compared with those of other resistive switching materials. The statistical characteristics provide essential evidence for analysis of the switching mechanism and evaluation of the memory devices.

DISTURBANCE MODELING FOR PROCESS CONTROL VIA HIDDEN MARKOV MODELS

This work proposes a framework for modeling disturbances that exhibit time-varying characteristics typically witnessed in process industries. These include intermittent drifts and abrupt jumps. Through examples, it is shown that the use of existing linear, stationary models is limiting. It is also demonstrated how the proposed switching model may be identified in a computationally tractable way.

Complete and partial flux switching in ferrite cores

A previously proposed switching model of ferrite cores under voltage pulsed excitations was based on the assumption that the flux switching occurs along the static magnetizing curve, independent of pulse amplitude. To define the limit of applicability of this model, the flux switching properties of ferrites under quasi-voltage pulsed excitations are investigated in terms of the switching φ(F) curve. The bounds of the voltage pulsed excitation are determined by two indications, composed of circuit parameters and the pulse amplitude. Domain patterns in the core driven by the quasi-voltage pulses are discussed briefly with regard to the relation between the complete flux switching and the partial switching.