On the controllability of systems with a time-varying delay†

This paper is concerned with the controllability of a system with a time-varying delay. The system to be considered here is described by a linear differential-difference equation of a retarded type, where a time-varying delay is a certain class of a time-varying function. First, the concepts of controllability for linear differential-difference systems with a constant delay, introduced by Weiss (1987), are developed to the system with a time-varying delay. Second, necessary and sufficient conditions for controllability are obtained. Finally, the controllability of a stationary system with a constant delay is treated, including the results of Chyung and Lee (1966).     

Robust estimation of continuous nonlinear plants with discrete measurements

In this work the problem of designing a state estimator for completely or partially observable continuous nonlinear plants with discrete measurements is addressed. The combination of a geometric approach with a stability analysis yields an estimator design methodology with a nonlinear detectability condition susceptible of testing, a systematic estimator construction, a robust convergence criterion coupled with a simple tuning scheme, as well as a rationale to explain the interplay between sampling time, estimator gains, and estimator functioning. Comparing with the continuous measurement case where the convergence is attained by tuning the gain above a low limit, in the discrete measurement case the loss of information due to the measurement sampling increases the size of the lower gain limit, and imposes sampling time and high gain limits. The proposed methodology is applied to address the estimation problem of a class of solution homopolymerization reactors, and is tested with a methyl-methacrylate polymerization run taken from a previous extended Kalman filter implementation study with experimental data.     

Computer experience, learning style, and hypermedia navigation

This study focused on the extent to which prior computer-related experiences predicted linear and nonlinear navigation when using a hypermedia learning environment. Those with more years’ experience at working with computers and those with more authoring experience took more linear steps, whereas those with more data base experience and those with more hypermedia experience took fewer linear steps. Those with more years experience at working with computers, those with more programming experience, and those with more authoring experience had a lower percentage of nonlinear steps than those with more experience in those three areas. Those with more word-processing experience, more spreadsheet experience, and more hypermedia experience had a higher percentage of nonlinear steps than those with less experience in those three areas. Also, those with more hypermedia experience took less time than those with less hypermedia experience. A major implication of the study is that we can predict the extent to which a hypermedia user may engage in a hypermedia environment in a nonlinear way by knowing his or her experience in a variety of computer-related uses.     

A Scalable Intelligent Takeoff Controller for a Simulated Running Jointed Leg

Running with jointed legs poses a difficult control problem in robotics. Neural controllers are attractive because they allow the robot to adapt to changing environmental conditions. However, scalability is an issue with many neural controllers. This paper describes the development of a scalable neurofuzzy controller for the takeoff phase of the running stride. Scalability is achieved by selecting a controller whose size does not grow with the dimensionality of the problem. Empirical results show that with proper design the takeoff controller scales from a leg with a single movable link to one with three movable links without a corresponding growth in size and without a loss of accuracy.     

Almost sure stability for uncertain differential equation with jumps

Uncertain differential equation with jumps, as a crucial tool to deal with a discontinuous uncertain system, is a type of differential equation driven by both canonical Liu process and uncertain renewal process. So far, a concept of stability in measure for an uncertain differential equation with jumps has been proposed. As a supplement, this paper proposes a concept of almost sure stability for an uncertain differential equation with jumps. A sufficient condition is derived for an uncertain differential equation with jumps being stable almost surely. As a corollary, a sufficient condition is also given for a linear uncertain differential equation with jumps being stable almost surely.     

Quantitative validation techniques a database. (I). Simple examples

This paper proposes the formulation of a database of validation examples. This initial contribution describes the problem of validation of the simulation of two real systems. These include a mechanical network and a thermal system with a transport delay. Data of the component values and measurements are reported here. The data from testing these systems will be made available at a later stage to enable other workers to compare other validation techniques with those presented here.The responses of a mechanical and a thermal system were measured with a laptop PC and Labview via a DAQCard^TM-700 data acquisition card. Simulations were made with ACSL and ACSL Math.The validation procedures implemented included a parameter variation with integral quadratic weighting and ITAE weighting together with a statistical matching technique using a correlation coefficient.These techniques illustrate the problem of achieving “good” validation to within a few percentage points. Correlation coefficients of over 98% were obtained for the fitting of linear models, with Theil indices of less than 0.075.     

An efficient grayscale image encryption scheme based on variable length row-column swapping operations

Multimedia Tools and Applications - Swapping a row with a row, a column with a column or row with a column are usual operations carried out to scramble the given input plain image. To introduce...     

Robust synchronization of dynamical networks with compensation of disturbances

In this paper, a robust output control scheme is proposed for a linear dynamical network such that every its local subsystem is described by a linear differential equation with a priori unknown parameters. The network is subject to unknown exogenous bounded disturbances. The considerations are based on the introduction of a directed graph with vertices associated with the corresponding nodes of the network. An algorithm is proposed which ensures the synchronization of the network along with the compensation of the unknown disturbances with required accuracy. It is shown that the proposed scheme also remains valid for a network associated with an undirected graph. The theoretical results are illustrated via a numerical example of a network with four nodes.     

一种基于快速闭合的真空断路器短路电流限流器

本文提出一种新型的带串联补偿的短路电流限制器,它主要由可快速闭合的真空断路器、电容和电感元件及无功补偿回路组成,与电容并联的快速开断的真空断路器控制着正常时的串联补偿或短路的限流,通过仿真及样机实验,证明了此系统具有良好限流保护特性。     

Integrated text entry from power wheelchairs

Power wheelchair joysticks have be used to control a mouse cursor on desktop computers, but they offer no integrated text entry solution, confining users to point-and-click or point-and-dwell with on-screen keyboards. On-screen keyboards reduce useful screen real-estate, exacerbating the need for frequent window management, and impose a secondary focus of attention. By contrast, we present two integrated gestural text entry methods designed for use from power wheelchairs: one for use with joysticks and the other for use with touchpads. Both techniques are adaptations of EdgeWrite, originally a stylus-based unistroke method designed for people with tremor. In a preliminary text entry study of 7 power wheelchair users, we found that EdgeWrite with a touchpad was faster than the on-screen keyboard WiViK with a joystick, and EdgeWrite with a joystick was only slightly slower. These results warranted a multi-session comparison of text entry with EdgeWrite and WiViK using joysticks and touchpads, in which we found touchpads faster than joysticks, and EdgeWrite faster than WiViK with both devices after initial learning periods.     

Unity enhances product aesthetics and emotion

Although the aesthetic properties of a product are likely associated with users' emotional responses, empirical evidence does not explain how the aesthetic properties of a product evoke an emotional response. This study presents the hypothesis that users' emotions are evoked when they observe an aesthetically pleasing product with unity. The results implied that a product form with more unity had a greater likelihood of affecting users' positive emotions compared with those with less unity, and that the unity aesthetic may act as a mediator in evoking emotion. In addition, the results confirmed that products composed of curvier elements tended to evoke a stronger pleasure response compared with those defined by straight lines. A systematic approach, namely the decision tree method, acts as a unity design guideline for the enhancement of product aesthetics, which may evoke users’ pleasure responses further.Relevance to industryOur findings imply that a product form with more unity had a greater likelihood of affecting users’ positive emotions compared with those with less unity. In addition, a systematic approach, namely the decision tree method, acts as a unity design guideline for the enhancement of product aesthetics, which may apply for designing products with pleasures.     

A Novel Cascaded PID Controller for Automatic Generation Control Analysis With Renewable Sources

Present day power scenarios demand a high quality uninterrupted power supply and needs environmental issues to be addressed. Both concerns can be dealt with by the introduction of the renewable sources to the existing power system. Thus, automatic generation control (AGC) with diverse renewable sources and a modified-cascaded controller are presented in the paper. Also, a new hybrid scheme of the improved teaching learning based optimization-differential evolution (hITLBO-DE) algorithm is applied for providing optimization of controller parameters. A study of the system with a technique such as TLBO applied to a proportional integral derivative (PID), integral double derivative (IDD) and PIDD is compared to hITLBO-DE tuned cascaded controller with dynamic load change.The suggested methodology has been extensively applied to a 2-area system with a diverse source power system with various operation time non-linearities such as dead-band of, generation rate constraint and reheat thermal units. The multi-area system with reheat thermal plants, hydel plants and a unit of a wind-diesel combination is tested with the cascaded controller scheme with a different controller setting for each area. The variation of the load is taken within 1% to 5% of the connected load and robustness analysis is shown by modifying essential factors simultaneously by ± 30%. Finally, the proposed scheme of controller and optimization technique is also tested with a 5-equal area thermal system with non-linearities. The simulation results demonstrate the superiority of the proposed controller and algorithm under a dynamically changing load.      

Projection operator-based robust adaptive control of an aerial robot with a manipulator

This paper describes a quadcopter manipulator system, an aerial robot with an extended workspace, its controller design, and experimental validation. The aerial robot is based on a quadcopter with a three degree of freedom robotic arm connected to the base of the vehicle. The work aims to create a stable airborne robot with a robotic arm that can work above and below the airframe, regardless of where the arm is attached. Integrating a robotic arm into an underactuated, unstable system like a quadcopter can enhance the vehicle's functionality while increasing instability. To execute a mission with accuracy and reliability during a real-time task, the system must overcome the inter-coupling effects and external disturbances. This work presents a novel design for a robust adaptive feedback linearization controller with a model reference adaptive controller and hardware implementation of the quadcopter manipulator system with plant uncertainties. The closed-loop stability of the aerial robot and the tracking error convergence with the robust controller is analyzed using Lyapunov stability analysis. The quadcopter manipulator system is custom developed in the lab with an off-the-shelf quadcopter and a 3D-printed robotic arm. The robotic system architecture is implemented using a Jetson Nano companion computer for autonomous onboard flight. Experiments were conducted on quadcopter manipulator system to evaluate the autonomous aerial robot's stability and trajectory tracking with the proposed controller.     

Learning experiments with genetic optimization of a generalized regression neural network

This paper reports a study unifying optimization by genetic algorithm with a generalized regression neural network. Experiments compare hill-climbing optimization with that of a genetic algorithm, both in conjunction with a generalized regression neural network. Controlled data with nine independent variables are used in combination with conjunctive and compensatory decision forms, having zero percent and 10 percent noise levels. Results consistently favor the GRNN unified with the genetic algorithm.     

Stabilization of time-delay systems with a Controlled time-varying delay and applications

We study the stability of a linear system with a point-wise, time-varying delay. We assume that the delay varies around a nominal value in a deterministic way and investigate the influence of this variation on stability. More precisely we are interested in characterizing situations where the time-varying delay system is stable, whereas the system with constant delay is unstable. Our approach consists of relating the stability properties of a system with a fast varying point-wise delay with these of a time-invariant system with a distributed delay. Then we can use frequency domain methods to analyze the problem and to derive stability criteria. The results are first illustrated with two theoretical examples. Then, we study a model of a variable speed rotating cutting tool. Based on the developed theory, we thereby provide both a theoretical explanation and a quantitative analysis tool for the beneficial effect of a variation of the machine speed on enhancing stability properties, which was reported in the literature.     

On nonlinear H∞ control under sampled measurements

This paper deals with the nonlinear H_∞ control problem with sampled measurement feedback. This problem has already been studied in Suzuki et al. (1995), where, using a certainty equivalence principle, a control solution involving a state estimator with a linear injection gain is proposed. Using the same general framework, we propose a more refined estimator with a nonlinear injection gain. This gain is shown to be connected to a periodic solution of a Hamilton-Jacobi inequality with jumps     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.     

Abstract representation theorems for demonic refinement algebras

The main result of this article is that every demonic refinement algebra with enabledness and termination is isomorphic to an algebra of ordered pairs of elements of a Kleene algebra with domain and with a divergence operator satisfying a mild condition. Divergence is an operator producing a test interpreted as the set of states from which nontermination may occur. An example of a KAD where a divergence operator cannot be defined is given. In addition, it is shown that every demonic refinement algebra with enabledness is also a demonic refinement algebra with termination.     

Retraction and Generalized Extension of Computing With Words

Fuzzy automata, whose input alphabet is a set of numbers or symbols, are a formal model of computing with values. Motivated by Zadeh's paradigm of computing with words rather than numbers, Ying proposed a kind of fuzzy automata, whose input alphabet consists of all fuzzy subsets of a set of symbols, as a formal model of computing with all words. In this paper, we introduce a somewhat general formal model of computing with (some special) words. The new features of the model are that the input alphabet only comprises some (not necessarily all) fuzzy subsets of a set of symbols and the fuzzy transition function can be specified arbitrarily. By employing the methodology of fuzzy control, we establish a retraction principle from computing with words to computing with values for handling crisp inputs and a generalized extension principle from computing with words to computing with all words for handling fuzzy inputs. These principles show that computing with values and computing with all words can be respectively implemented by computing with words. Some algebraic properties of retractions and generalized extensions are addressed as well.     

Reactive transport of volatile organic compound mixtures in the unsaturated zone: modeling and tuning with lysimeter data

Petroleum products involve mixtures of different volatile organic compounds (VOCs) that may represent a risk for groundwater after a spill to the unsaturated zone. However, the majority of the published approaches and codes for unsaturated zone modeling handle only either a single or a limited number of compounds in order to cope with the complexity of processes involved in VOC attenuation. This work aimed at simulating complex VOC scenarios using a grouping procedure, which results in the definition of a small number of effective pseudospecies with carefully specified effective properties. Grouping criteria are developed for a hypothetical scenario that involves a mixture of seven VOCs with properties covering a wide range of values. These criteria are assessed through a comparison of group-based calculations with rigorous calculations using the individual components. Groups of species with similar solubility resulted in concentration profiles that compared very satisfactorily with the rigorous results. The approach is validated with data from a large-scale lysimeter experiment. The simulation results compare satisfactorily with the experimental data for several days and for the vast majority of the mixture components. The agreement was significantly improved when temporally varying solubility values were used, justified by the difference in the compound volatility and the concomitant alteration of the VOC mixture composition with time.