Controller design for natural and robotic systems with transmission delays

Robust stability and two‐dimensional trajectory following problems are considered for n‐link robotic systems with transmission delays. Such problems appear in telerobotics, where the controller is physically far from the robot, and in neural control of musculo‐skeletal (biological) systems, where muscle actuation and neural sensing are subject to time delays. A typical second‐order nonlinear dynamical model is taken with input and output time delays. In a prior work by the authors, a control strategy was developed for stable movement of the planar linkage system, using the standard Q‐parameterization and solving an H^∞ control problem to determine the free parameter. In this article, a new control scheme is proposed to eliminate the steady‐state errors seen in the tracking performance of the controller derived in the earlier work. Simulation examples are shown to demonstrate the effectiveness of the proposed control methodology. © 2002 Wiley Periodicals, Inc.     

DE+RBFNs based classification: A special attention to removal of inconsistency and irrelevant features

A novel approach for the classification of both balanced and imbalanced dataset is developed in this paper by integrating the best attributes of radial basis function networks and differential evolution. In addition, a special attention is given to handle the problem of inconsistency and removal of irrelevant features. Removing data inconsistency and inputting optimal and relevant set of features to a radial basis function network may greatly enhance the network efficiency (in terms of accuracy), at the same time compact its size. We use Bayesian statistics for making the dataset consistent, information gain theory (a kind of filter approach) for reducing the features, and differential evolution for tuning center, spread and bias of radial basis function networks. The proposed approach is validated with a few benchmarked highly skewed and balanced dataset retrieved from University of California, Irvine (UCI) repository. Our experimental result demonstrates promising classification accuracy, when data inconsistency and feature selection are considered to design this classifier.     

Monitoring coal fires using multi-temporal night-time thermal images in a coalfield in north-west China

China has the largest coal resources in the world but these are seriously endangered by coal fires. Though the problem of coal fires is long standing and not only limited to China, little has been done for regular monitoring of these fires. This Letter proposes the use of multi-temporal night-time thermal images acquired from Landsat Thematic Mapper band 6 for establishing a coal fire monitoring system for a coalfield in north-west China. Other images and map data are fused with the thermal images to provide a comprehensive picture of the fires through the years. Finally the fires are classified into different categories based on multi-temporal changes.     

Surface fires in Jharia coalfield,India-their distribution and estimation of area and temperature from TM data

Surface fires occur at a number of places in the Jharia coalfield and are high-temperature phenomena of relatively local extent. The use of Landsat Thematic Mapper (TM) shortwave infrared (SWIR) bands in estimating temperatures of high-temperature objects is briefly reviewed. Study of data of TM7 and TM5 bands indicate the existence of surface fires in the Jharia coalfield at 59 pixels and this was supported by limited field checks. Pixel-integrated temperatures of surface fire areas are estimated to be in the range of 217 C to 410 C. However, as these fires often do not occupy the whole pixel area, the pixelintegrated temperatures are less than the actual fire temperatures. The relation between spectral radiance and temperature is nonlinear. Therefore, radiant temperature in TM5 and TM7 can be used to estimate the subpixel area and temperature of surface fires (provided there is no band saturation). In the Jharia coalfield, the subpixel area of some of the surface fires has been found to range between 0.2 of a pixel (180m2) to 0.003 of a pixel (27m2). The subpixel temperature corresponding to these instances has been found to range 342 C to 731 C. The limitations and operational aspects of these techniques are indicated.     

Knowledge Compilation Meets Database Theory: Compiling Queries to Decision Diagrams

The goal of Knowledge Compilation is to represent a Boolean expression in a format in which it can answer a range of “online-queries” in PTIME. The online-query of main interest to us is model counting, because of its application to query evaluation on probabilistic databases, but other online-queries can be supported as well such as testing for equivalence, testing for implication, etc. In this paper we study the following problem: given a database query q, decide whether its lineage can be compiled efficiently into a given target language. We consider four target languages, of strictly increasing expressive power (when the size of compilation is restricted to be polynomial in the data size): read-once Boolean formulae, OBDD, FBDD and d-DNNF. For each target, we study the class of database queries that admit polynomial size representation: these queries can also be evaluated in PTIME over probabilistic databases. When queries are restricted to conjunctive queries without self-joins, it was known that these four classes collapse to the class of hierarchical queries, which is also the class of PTIME queries over probabilistic databases. Our main result in this paper is that, in the case of Unions of Conjunctive Queries (UCQ), these classes form a strict hierarchy. Thus, unlike conjunctive queries without self-joins, the expressive power of UCQ differs considerably with respect to these target compilation languages. Moreover, we give a complete characterization of the first two target languages, based on the query’s syntax.     

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.      

Numerical analysis of fluid squeezed between two parallel plates by meshless method

This paper presents the steady-state and transient analysis of the fluid squeezed between two long parallel plates. The governing coupled partial differential equations have been discretized by element free Galerkin method and implemented using variational approach. Penalty and Lagrange multiplier techniques have been utilized to enforce the essential boundary conditions. Four point Gauss quadrature has been used to evaluate the viscous terms in the coefficient matrix whereas reduced integration scheme (i.e. one point Gauss quadrature) has been used to evaluate the penalty terms over two-dimensional domain (Ω). Cubicspline, exponential and rational weight functions have been used in the present work. The results obtained by EFG method are compared with those obtained by finite element and analytical methods. The effect of scaling and penalty parameters on EFG results has been discussed in detail.     

Insider attack mitigation in a smart metering infrastructure using reputation score and blockchain technology

International Journal of Information Security - The increasing use of smart metering infrastructure invites security threats through trusted insiders in spite of the devices’ authentication...     

The photo-electrochemical studies of Eu doped yttrium orthovanadate–zinc oxide–reduced graphene oxide nanohybrid

A new class of nanostructured photo-electrocatalyst Eu³⁺ doped yttrium orthovanadate–zinc oxide–reduced graphene oxide (YVO₄:Eu³⁺–ZnO–RGO) nanohybrid was developed by a simple electrostatic self-assembly at room temperature, using ZnO, YVO₄:Eu³⁺ and RGO as building blocks. Interaction among YVO₄:Eu³⁺, ZnO and RGO is indicated by variation in hydrodynamic diameter (H_D) and zeta potentials of the products as compared to their individual components, thus suggesting that YVO₄:Eu³⁺–ZnO–RGO is a nanohybrid and not a physical mixture. Electrochemical response of this nanohybrid towards the redox couple of Fe(CN)₆^3−/4− was investigated before and after UV irradiation. Apart from quenching of the green emission of ZnO in photoluminescence spectrum, which serves as a probe to monitor the interfacial electron transfer from excited ZnO to RGO, degradation in electrochemical redox process provides an additional path to monitor interfacial electron transfer.     

Large physisorption strain in chemical vapor deposition of graphene on copper substrates

Graphene single layers grown by chemical vapor deposition on single crystal Cu substrates are subject to nonuniform physisorption strains that depend on the orientation of the Cu surface. The strains are revealed in Raman spectra and quantitatively interpreted by molecular dynamics (MD) simulations. An average compressive strain on the order of 0.5% is determined in graphene on Cu(111). In graphene on Cu (100), MD simulations interpret the observed highly nonuniform strains.