Discrete Switching Research Articles

DTC Based Induction Motor Speed Control Using 10-Sector Methodology for Torque Ripple Reduction

A direct torque control (DTC) drive allows direct and independent control of flux linkage and electromagnetic torque by the selection of optimum inverter switching modes. It is a simple method of signal processing which gives excellent dynamic performance. Also transformation of coordinates and voltage decoupling are not required. However, the possible discrete inverter switching vectors cannot always generate exact stator voltage required, to obtain the demanded electromagnetic torque and flux linkages. This results in the production of ripples in the torque as well as flux waveforms. In the present paper a torque ripple reduction methodology is proposed. In this method the circular locus of flux phasor is divided into 10 sector as compared to six sector divisions in conventional DTC method. The basic DTC scheme and the 10-sector method are simulated and compared for their performance. An analysis is done with sector increment so that finally the torque ripple varies slightly as the sector is increased.

Wavelet Kernel Based on Identification for Nonlinear Hybrid Systems

This paper presents a new method based on wavelet for a class of nonlinear hybrid systems identification. Hybrid systems identification is composed of two problems; estimate the discrete modes or switch among the system modes and estimate continues submodels. In this paper, we assumed that haven’t any prior knowledge about data classification and submodels identification. Also the combining of feature vector selection algorithm and wavelet are used in subspace learning and support vector machine as a classifier. The results indicate that the error of using the wavelet in subspace learning process becomes low. In addition, the proposed method is convergent and has an acceptable response in presence of high-power noise.

Optimal control of partitioned hybrid systems via discrete-time Hamilton–Jacobi theory

Computational framework for optimal control of hybrid systems with a partitioned state space is presented. It is shown that necessary conditions for optimality for a discrete-time dynamic system can be solved concurrently for various boundary conditions, according to the recent development of discrete-time Hamilton–Jacobi theory. This unique property is utilized to construct computationally efficient numerical optimization of hybrid systems where discrete switching dynamics occurs at the boundary between partitions of the configuration space. A benchmark example shows that the proposed approach has substantial computational advantages compared with the existing ones.

A Modeling Method of Switched Systems Based on AP Clustering

The behavior of hybrid systems is determined by combining continuous variables with discrete switching logic. The identification of a hybrid systems aims to find an accurate model of the system's dynamics based on its past inputs and outputs. For a class of hybrid systems in the switched form, a model identification method based on affinity propagation clustering is presented in this paper. In this method, the model identification issue is equivalent to the problems of classification of the cluster data of the system and regression of the classification data. The clustering algorithm is successively applied to group the sampled data into clusters, and the sub-models are trained by least squares support vector machines according to corresponding sub-class samples. The last model of switched systems is obtained by combining each sub-model. Simulation results show the effectiveness and feasibility of the proposed method.

Input design for guaranteed fault diagnosis using zonotopes

An input design method is presented for guaranteeing the diagnosability of faults from the outputs of a system. Faults are modeled by discrete switches between linear models with bounded disturbances and measurement errors. Zonotopes are used to efficiently characterize the set of inputs that are guaranteed to lead to outputs that are consistent with at most one fault scenario. Provided that this set is nonempty, an element is then chosen that is minimally harmful with respect to other control objectives. This approach leads to a nonconvex optimization problem, but is shown to be equivalent to a mixed-integer quadratic program that can be solved efficiently. Methods are given for reducing the complexity of this program, including an observer-based method that drastically reduces the number of binary variables when many sampling times are required for diagnosis.

A method for the assessment of the optimal parameter of discrete-time switch model

This paper proposes a novel method for the optimal parameter selection of the discrete-time switch model used in circuit solvers that adopt the fixed admittance matrix nodal method (FAMNM) approach. As known, FAMNM-based circuit solvers allow to reach efficient computation times, in particular for real-time simulation applications, since they do not need the inversion of the circuit nodal admittance matrix. However, these solvers need to optimally tune the so-called discrete switch conductance, since this parameter might largely affect the simulations accuracy. Within this context, we propose a method for the determination of the discrete-time switch conductance which is obtained by minimizing the distance between the eigenvalues of the original circuit's nodal admittance matrix with those associated with the circuit including the discrete-time switches. The method is proven to provide values of the discrete-time switch conductance that maximize the simulation accuracy and minimize the losses on this artificially introduced parameter. Additionally, the proposed method avoids the use of trial-and-error process typically required when discrete-time switch conductances need to be addressed in FAMNM approach. The performances of the proposed method are demonstrated for circuits with single and multiple switches in which passive RLC elements and transmission lines are both considered.

The Fluorescence Intermittency for Quantum Dots Is Not Power-Law Distributed: A Luminescence Intensity Resolved Approach

The photoluminescence (PL) of single emitters like semiconductor quantum dots (QDs) shows PL intermittency, often called blinking. We explore the PL intensities of single CdSe/ZnS QDs in polystyrene (PS), on polyvenylalcohol (PVA), and on silicon oxide (SiOx) by the change-point analysis (CPA). By this, we relate results from the macrotime (sub-ms to 1000 s) and the microtime (0.1-100 ns) range to discrete PL intensities. We conclude that the intensity selected "on"-times in the ms range correspond to only a few (discrete) switching times, while the PL decays in the ns range are multiexponential even with respect to the same selected PL intensity. Both types of relaxation processes depend systematically on the PL intensity in course of a blinking time trace. The overall distribution of on-times does not follow a power law contrary to what has often been reported but can be compiled into 3-4 characteristic on-times. The results can be explained by the recently suggested multiple recombination centers model. Additionally, we can identify a well-defined QD state with a very low PL intensity above the noise level, which we assign to the strongly quenched exciton state. We describe our findings by a model of a hierarchical sequence of hole and electron trapping. Blinking events are the consequence of slow switching processes among these states and depend on the physicochemical properties of the heterogeneous nanointerface of the QDs.

Multiple Timescales and Modeling of Dynamic Bounce Phenomena in RF MEMS Switches

Electrostatically operated RF-MEMS switches are known to suffer from discrete switch bounce events during switch closure that increase wear and tear and lead to increased switching times. Here, we use laser Doppler vibrometer to analyze the switch response of three types of cantilevered dc-contact switches at a 200 ns time resolution. We find that bounce events are multiple time scale events with distinct motion occurring at 10-1 and 101 s timescales in effect high frequency bounces within a bounce. To understand the origin of this effect, we develop a multiple eigenmode model of a cantilever switch with electrostatics, repulsive and adhesive contact forces, and rarefied gas damping and find that the high frequency bounce arises from the transient excitation of the 2nd eigenmode of the cantilever structure of the RF-MEMS switch. This phenomenon not only describes the multiple time scales involved in bounce events, but also shows that the transient excitation of the second mode leads to complex drum roll like dynamics, leading to a series of closely spaced impacts in each actuation cycle. A careful study of the dependence of the phenomenon on contact stiffness and adhesion shows how the landing pad stiffness, adhesion, and actuation voltage in dc contact switches can increase or diminish repeated impacts during actuation.

Formation of self-assembled nanodomain structures in single crystals of uniaxial ferroelectrics lithium niobate, lithium tantalate and strontium–barium niobate

The formation and evolution of the self-assembled nanodomain structures during polarization reversal have been comparatively analyzed in single crystals of various uniaxial ferroelectrics: LiNbO 3 (LN), LiTaO 3 (LT) and Sr x Ba 1-x Nb 2 O 6 (SBN). Several experimental methods have been used for visualization of the micro- and nanodomain patterns. The static domain images have been obtained by optical microscopy and piezoresponse force microscopy. The Raman confocal microscopy allowed us to obtain the domain images in the bulk. The equilibrium slow switching with effective screening resulted in growth of polygon-shaped micro-domains: hexagons in LN, triangles in LT and squares in SBN, which corresponds to crystal symmetry. Switching in nonequilibrium conditions (noneffective screening of depolarization field) brings to appearance of similar nanodomain structures in all studied crystals as a result of different processes: (1) formation of nanodomain ensembles, (2) discrete switching, (3) incomplete merging and (4) spontaneous backswitching.

Exploitation of renewable resources with differentiated technologies: An evolutionary analysis

In this paper, we propose a dynamical model of technology adoption for the exploitation of a renewable natural resource. Each technology has a different efficiency and environmental impact. The process of technology adoption over time is modeled through an evolutionary game employed by profit maximizing exploiters. The loss in profits due to lower efficiency levels of environmentally-friendly technologies can be counterbalanced by the higher consumers’ propensity to pay for greener goods. The dynamics of the resource take place in continuous time, whereas the technology choice can be revised either in continuous-time or in discrete-time. In the latter case, the model assumes the form of a hybrid system, whose dynamics is mainly explored numerically. We shows that: (1) overexploitation of the resource arises whenever the reduction in harvesting due to a lower efficiency of clean technology is more than compensated by a higher propensity to pay for greener goods; (2) the difference between the fixed costs of these technologies can be exogenously fixed to provide an incentive for adopting clean technology without affecting the long-run level of the resource; and (3) in some cases, discrete switching of the technology causes overshooting in the dynamics whereas in others it enhances the stability of the system.

Output Feedback H ∞ Stabilization of 2D Discrete Switched Systems in FM LSS Model

This paper investigates the dynamic output feedback H∞ stabilization problem for a class of discrete-time 2D (two-dimensional) switched systems represented by a model of FM LSS (Fornasini–Marchesini local state space) model. First, sufficient conditions for the exponential stability and weighted H∞ disturbance attenuation performance of the underlying system are derived via the average dwell time approach. Then, based on the obtained results, dynamic output feedback controller is proposed to guarantee that the resulting closed-loop system is exponentially stable and has a prescribed disturbance attenuation level γ. Finally, two examples are provided to verify the effectiveness of the proposed method.

A Branch and Bound algorithm for minimizing the energy consumption of an electrical vehicle

The problem we address in this paper, is the minimization of the energy consumption of an electrical vehicle achievable on a given driving cycle. This can be formulated as an optimal control problem with a discrete switch control. In this paper, we present a new formulation of this problem by taking into account the electrical and mechanical parts of the vehicle. By using prototype optimal control shooting techniques, we did not provide efficient solutions. Consequently, we focused on an operational method based on a Branch and Bound algorithm to solve this optimal switching control problem. Some numerical experiments validate our methodology.

Role of local curvature in grain boundary sliding in a deformed polycrystal

The paper considers experimental and theoretical principles of accounting for curvature in multiscale computer simulation of the behavior of interfaces as independent planar subsystems in a loaded polycrystal. Dynamics of matter and energy flows along grain boundaries is studied using a hybrid discrete-continuous method of excitable cellular automata, which combines synergetic principles of discrete switching and laws of continuum mechanics. It is shown that these flows have a rotational-wave nature and depend on the loading conditions of a grain boundary.

Investigations of 2.9-GHz Resonant Microwave-Sensitive Ag/MgO/Ge/Ag Tunneling Diodes

In this work, a resonant microwave-sensitive tunneling diode has been designed and investigated. The device, which is composed of a magnesium oxide (MgO) layer on an amorphous germanium (Ge) thin film, was characterized by means of temperature-dependent current (I)–voltage (V), room-temperature differential resistance (R)–voltage, and capacitance (C)–voltage characteristics. The device resonating signal was also tested and evaluated at 2.9 GHz. The I–V curves reflected weak temperature dependence and a wide tunneling region with peak-to-valley current ratio of ∼1.1. The negative differential resistance region shifts toward lower biasing voltages as temperature increases. The true operational limit of the device was determined as 350 K. A novel response of the measured R–V and C–V to the incident alternating-current (ac) signal was observed at 300 K. Particularly, the response to a 100-MHz signal power ranging from the standard Bluetooth limit to the maximum output power of third-generation mobile phones reflects a wide range of tunability with discrete switching property at particular power limits. In addition, when the tunnel device was implanted as an amplifier for a 2.90-GHz resonating signal of the power of wireless local-area network (LAN) levels, signal gain of 80% with signal quality factor of 4.6 × 104 was registered. These remarkable properties make devices based on MgO-Ge interfaces suitable as electronic circuit elements for microwave applications, bias- and time-dependent electronic switches, and central processing unit (CPU) clocks.

Stability and Stabilization of Discrete Switched Systems Based on Parameter-Dependent Lyapunov Functions

This paper addresses the stability and stabilization of discrete switched systems which can be used to describe manufacturing systems. A new sufficient and necessary condition in the use of parameter-dependent Lyapunov functions is proposed to guarantee the switched system stability under arbitrary switching. The control synthesis approach presented in this work reduces the conservatism by slack variables while investigating the static output feedback control issue. A cone complementarity linearization algorithm is applied to make the condition a minimization problem in the form of LMIs. By numerical evaluation, the new control design technique is illustrated to be more efficient.

Constrained Interaction and Coordination in Proximity-Limited Multiagent Systems

In this paper, we consider the problem of controlling the interactions of a group of mobile agents, subject to a set of topological constraints. Assuming proximity-limited interagent communication, we leverage mobility, unlike prior work, to enable adjacent agents to interact discriminatively, i.e., to actively retain or reject communication links on the basis of constraint satisfaction. Specifically, we propose a distributed scheme that consists of hybrid controllers with discrete switching for link discrimination, coupled with attractive and repulsive potentials fields for mobility control, where constraint violation predicates form the basis for discernment. We analyze the application of constrained interaction to two canonical coordination objectives, i.e., aggregation and dispersion, with maximum and minimum node degree constraints, respectively. For each task, we propose predicates and control potentials, and examine the dynamical properties of the resulting hybrid systems. Simulation results demonstrate the correctness of our proposed methods and the ability of our framework to generate topology-aware coordinated behavior.

Output Feedback Control of NCS with Communication Constraints

Considering the influence of communication constraints and uncertain short delay, this paper models NCS with communication sequence as a discrete periodical switching system with uncertainty, which integrates information scheduling and control. Using the method of piecewise Lyapunov function and the switching system theory, the asymptotic stability condition of the system with periodical information scheduling is derived in the form of matrix inequalities, and a output feedback controller design method is derived.

Exactly solvable chaos in an electromechanical oscillator

A novel electromechanical chaotic oscillator is described that admits an exact analytic solution. The oscillator is a hybrid dynamical system with governing equations that include a linear second order ordinary differential equation with negative damping and a discrete switching condition that controls the oscillatory fixed point. The system produces provably chaotic oscillations with a topological structure similar to either the Lorenz butterfly or Rössler's folded-band oscillator depending on the configuration. Exact solutions are written as a linear convolution of a fixed basis pulse and a sequence of discrete symbols. We find close agreement between the exact analytical solutions and the physical oscillations. Waveform return maps for both configurations show equivalence to either a shift map or tent map, proving the chaotic nature of the oscillations.

Thermally tunable quadruple Vernier racetrack resonators

The spectral responses of series-coupled racetrack resonators exhibiting the Vernier effect have many attractive features as compared to the spectral responses of identical series-coupled racetrack resonators, such as free spectral range (FSR) extension and enhanced wavelength tunability. Here we present experimental results of a thermally tunable quadruple series-coupled silicon racetrack resonator exhibiting the Vernier effect. We thermally tune two of the four racetrack resonators to enable discrete switching of the major peak by 15.54 nm. Also, our device has an interstitial peak suppression of 35.4 dB, a 3 dB bandwidth of 0.45 nm, and an extended FSR of 37.66 nm.

Synthesis of Reactive Switching Protocols From Temporal Logic Specifications

We propose formal means for synthesizing switching protocols that determine the sequence in which the modes of a switched system are activated to satisfy certain high-level specifications in linear temporal logic (LTL). The synthesized protocols are robust against exogenous disturbances on the continuous dynamics and can react to possibly adversarial events (both external and internal). Finite-state approximations that abstract the behavior of the underlying continuous dynamics are defined using finite transition systems. Such approximations allow us to transform the continuous switching synthesis problem into a discrete synthesis problem in the form of a two-player game between the system and the environment, where the winning conditions represent the high-level temporal logic specifications. Restricting to an expressive subclass of LTL formulas, these temporal logic games are amenable to solutions with polynomial-time complexity. By construction, existence of a discrete switching strategy for the discrete synthesis problem guarantees the existence of a switching protocol that can be implemented at the continuous level to ensure the correctness of the nonlinear switched system and to react to the environment at run time.