Fast Switching Mechanism Research Articles

Observer-based controller design for switched systems with stable and unstable subsystems

Abstract This paper studies the problems of both state estimation and observer-based control for a class of switched linear systems with stable and unstable subsystems. By combining slow switching and fast switching mechanism, the observer design and observer-based controller are presented. Firstly, a state observer is developed to estimate the states of switched system by designing admissible edge-dependent switching signal, and a multiple discontinuous Lyapunov function is also constructed to obtain the existence condition of observer. Secondly, based on the stability characteristics of subsystem and the estimated state information, an observer-based feedback controller is proposed. The stability of the closed-loop system is also guaranteed by Lyapunov stability theory. Finally, the feasibility of the proposed method is verified by simulation.

Stabilization of non-smooth variable order switched nonlinear systems

The paper discusses the issue of global asymptotic stabilization for non-smooth variable order nonlinear switched systems with partial unstable modes. The existence and uniqueness of solution for the considered system is firstly verified by utilizing Gronwall–Bellman inequality and the inductive method. Then, a slow switching strategy is performed for the stable modes and the unstable modes are handled by a fast switching mechanism. Under the framework of Filippov differential inclusion, sufficient stabilization criteria are derived by applying the mode-dependent average dwell time and dwell time schemes. Finally, some objects in real life are introduced and a numerical simulation is offered to show the validity of the obtained results.

User-friendly deniable storage for mobile devices

Mobile devices are prevalently used to process sensitive data, but traditional encryption may not work when an adversary is able to coerce the device owners to disclose the encryption keys. Plausibly Deniable Encryption (PDE) is thus designed to protect sensitive data against this powerful adversary. In this paper, we present MobiPluto, a user-friendly PDE scheme for denying the existence of sensitive data stored on mobile devices. A salient difference between MobiPluto and the existing PDE systems is that any block-based file systems can be deployed on top of it. To further improve usability and deniability of MobiPluto, we introduce a fast switching mechanism and incorporate the widely-used Near Field Communication (NFC) technology. Users can securely switch from the public mode to the hidden mode within 10 seconds, which is a significant improvement compared to previous solutions. Users can also store strong passwords on NFC cards and tap them to enter the system, which significantly liberates them from the burden of memorizing and typing strong passwords. Most importantly, the users can deny the existence of the hidden data without the skill to camouflage as long as the NFC cards are used properly.

Period fold structure of graphene SPP waveguide

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons (SPPs), i.e. the collective electron oscillations at the interface of a metal/dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we design folds graphene waveguide excited SPPs and full compensation structures with periodic array by graphene material. Theoretically, we analyzed the loss of the way by periodic array gain full compensation is analyzed. By the results of theoretically analysis, we discover period fold structure not only excites SPPs, which also we can control device parameters using SPPs wave relations. In addition, periodic array compensation can significantly increase the propagation distance of SPPs. Simulation results we further find by simulation results: structure of our design has the advantage of strong localized and subwavelength waveguide size; periodic array compensation can significantly improve the electric field strength of nanocavity; structure of graphene waveguide expresses high levels of population inversion and low spontaneous emission noise disturbance. The graphene waveguide devices which we design can be the key device for the micro-nano optics, photonic sensing and measurement.

Surface plasmon resonance demodulation by optical ring-down cavity technology

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we presents a cavity ring-down technique called SPR sensor for conducting demodulated applications. Theoretical derivation indicates the conditions in which the laser frequency and linewidth remain unchanged, the optical field strength that mainly depends on the cavity mirror reflectivity, and the PZT scanning speed. Simulated experiments show that higher ring-down cavity precision, smaller anti-cross linewidth, and less time for increases and ring-downs are observed when the reflection coefficient is large. As a photon leaves the ring-down cavity, the photon quantities decrease again. The relative light intensity in the ring-down cavity is large when the PZT scanning speed is small. The application of a demodulation system shows that the ring-down cavity technology can largely improve the sensitivity of SPR sensors. The demodulation speed can also reach the ms level. A demodulation system is important for biochemical reaction kinetics and remote monitoring applications.

Nematodynamics modelling under extreme mechanical and electric stresses

Nematic liquid crystals confined in asymmetric π-cells and subjected to intense electrical and mechanical stresses undergo strong distortions which can be relaxed by means of the order reconstruction, a fast switching mechanism connecting topologically different textures, assuming bulk and/or surface characteristics depending on both amplitude of the applied electric fields and anchoring angles of the nematic molecules on the confining surfaces. In the frame of the Landau-de Gennes order tensor theory, we provide a numerical model implemented with a moving mesh finite element method appropriate to describe the nematic order dynamics, allowing to map the switching properties of the nematic texture.

Terahertz optoelectronics with surface plasmon polariton diode.

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/semiconductor and a dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we demonstrate a surface plasmon-polariton diode (SPPD) an optoelectronic switch that can operate at exceedingly large signal modulation rates. The SPPD uses heavily doped p-n junction where surface plasmon polaritons propagate at the interface between n and p-type GaAs and can be switched by an external voltage. The devices can operate at transmission modulation higher than 98% and depending on the doping and applied voltage can achieve switching rates of up to 1 THz. The proposed switch is compatible with the current semiconductor fabrication techniques and could lead to nanoscale semiconductor-based optoelectronics.

Magneto-elastic buckling of a soft cellular solid

The results of an experimental investigation into the elastic buckling of a soft cellular solid using magneto-static loading are reported. An electromagnet was used to apply a controlled force to an elastomer with embedded rare earth magnets. The resulting strain was found to induce an elastic buckling above a critical applied field strength. The buckling instability resulted in a rapid rotation of the sample which indicates potential as a fast switching mechanism for soft cellular materials.

39.2: Fast‐Switching Flexoelectric Display Device with High Contrast

AbstractThe flexoelectro‐optic effect provides a fast switching mechanism (τ90‐10 ∼ 10–100 μs) suitable for use in field‐sequential‐color, full motion video displays. An in‐plane field is applied to a short‐pitch chiral nematic liquid crystal aligned in the Uniform Standing Helix (or Grandjean) texture. The display performance is presented as a function of device parameters.

A selective dynamic compiler for embedded Java virtual machines targeting ARM processors

This paper presents a new selective dynamic compilation technique targeting ARM 16/32-bit embedded system processors. This compiler is built inside the J2ME/CLDC (Java 2 Micro Edition for Connected Limited Device Configuration) platform [Sun MicroSystems, Java 2 Platform, Micro Edition, Version 1.0 Connected, Limited Device Configuration, Specification, Technical Report, Sun Microsystems, CA, USA, May 2000]. The primary objective of this work is to elaborate an efficient, lightweight and low-footprint accelerated Java virtual machine ready to be executed on embedded machines. This is achieved by implementing a selective ARM dynamic compiler called Armed E-Bunny into Sun’s Kilobyte Virtual Machine (KVM) [Sun MicroSystems, KVM porting guide, Technical Report, Sun MicroSystems, CA, USA, September 2001]. In this paper we present the motivations, the architecture, the design and the implementation of Armed E-Bunny. The modified KVM is ported on a handheld PDA that is powered with embedded Linux and is tested using standard J2ME benchmarks. The experimental results demonstrate that a speed-up of 360% over the last version of Sun’s KVM is accomplished with a footprint that does not exceed 119 KB. An important result of this paper is also the proposition of an acceleration technique that leverages Armed E-Bunny by establishing a synergy between efficient interpretation and selective dynamic compilation. The main traits of this technique are: a one-pass compilation by code reuse, an efficient threaded interpretation and a fast switching mechanism between the interpreted and compiled modes.

Two recent developments in XMCD

This paper reports on two new technical developments concerning sample environments for X-ray magnetic circular dichroism (XMCD). The first measurements under high pressures of up to 30 GPa are described. The difficulties of combining the techniques of high pressure and XMCD are commented on. The second development involves the use of a fast-switching magnetic field. A new superconducting device is used to perform XMCD measurements on paramagnetic compounds in magnetic fields of up to 6 T. The small amplitude of the XMCD signal imposes, for a given signal-to-noise ratio, a noise less than a few 10(-5). The signal-to-noise ratio is improved by the use of a series of acquisitions, switching the magnetic field between each acquisition. A very fast switching mechanism has been built based on mechanical rotation of a superconducting coil, with the sample kept in place inside the coil. The XMCD signals at the L(II,III)-edges of paramagnetic rare-earth compounds have been measured at 4.5 K in fields of up to 6 T with a switching time of 11 s.

Dynamic Mechanism of Fast Switching in Light Valve Using Liquid Crystal

A light valve using a liquid crystal previously developed by the authors has a fast switching time of less than 1 ms. The fast switching mechanism of the value is studied theoretically in terms of the static characteristics of light transmission and the transient behavior of the cooperative angular variation of molecules submitted to an electric field. The variation in the light transmission is well explained by an analysis using optical anisotropy. The dynamic mechanism of the fast switching time is also interpreted by the principle of energy conservation related to the elastic, dielectric and viscous torque of the liquid crystal. The analytical results of the static and dynamic characteristics agree well with the experimental results.