Electrical Engineering

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Shiv Nadar University

In this study, an optimal control algorithm based on Hamilton-Jacobi- Bellman (HJB) equation, for the bounded robust controller design for finite-time-horizon nonlinear systems, is proposed. The HJB equation formulated using a suitable nonquadratic term in the performance functional to take care of magnitude constraints on the control input. Utilising the direct method of Lyapunov stability, we have proved the optimality of the controller with respect to a cost functional, that includes penalty on the control effort and the maximum bound on system uncertainty. The bounded controller requires the knowledge of the upper bound of system uncertainty. In the proposed algorithm, neural network is used to approximate the time-varying solution of HJB equation using least squares method. Proposed algorithm has been applied on the nonlinear system with matched and unmatched system uncertainties. Necessary theoretical and simulation results are presented to validate proposed algorithm. © 2009 The Institution of Engineering and Technology.

World University root node

(SoE) School of Engineering

IET Control Theory and Applications

Fixed final time optimal control approach for bounded robust controller design using Hamilton-Jacobi-Bellman solution

In this paper we formulate a least squares version of the recently proposed twin support vector machine (TSVM) for binary classification. This formulation leads to extremely simple and fast algorithm for generating binary classifiers based on two non-parallel hyperplanes. Here we attempt to solve two modified primal problems of TSVM, instead of two dual problems usually solved. We show that the solution of the two modified primal problems reduces to solving just two systems of linear equations as opposed to solving two quadratic programming problems along with two systems of linear equations in TSVM. Classification using nonlinear kernel also leads to systems of linear equations. Our experiments on publicly available datasets indicate that the proposed least squares TSVM has comparable classification accuracy to that of TSVM but with considerably lesser computational time. Since linear least squares TSVM can easily handle large datasets, we further went on to investigate its efficiency for text categorization applications. Computational results demonstrate the effectiveness of the proposed method over linear proximal SVM on all the text corpuses considered. © 2008 Elsevier Ltd. All rights reserved.

Expert Systems with Applications

Least squares twin support vector machines for pattern classification

In this paper we present a novel shape descriptor based on shape context, which in combination with hierarchical distance based hashing is used for word and graphical pattern based document image indexing and retrieval. The shape descriptor represents the relative arrangement of points sampled on the boundary of the shape of object. We also demonstrate the applicability of the novel shape descriptor for classification of characters and symbols. For indexing, we provide a new formulation for distance based hierarchical locality sensitive hashing. Experiments have yielded promising results. © 2009 IEEE.

Proceedings of the International Conference on Document Analysis and Recognition, ICDAR

Shape descriptor based document image indexing and symbol recognition

In this paper, a Hamilton-Jacobi-Bellman (HJB) equation based optimal control algorithm for robust controller design, is proposed for a nonlinear system. Utilizing the Lyapunov direct method, controller is shown to be optimal with respect to a cost functional that includes maximum bound on system uncertainty. Controller is continuous and requires the knowledge of the upper bound of system uncertainty. In the proposed algorithm, Neural Network (NN) is used to find approximate solution of HJB equation. Proposed algorithm has been applied on a nonlinear uncertain system. © 2009 IEEE.

Proceedings of the 7th International Conference on Advances in Pattern Recognition, ICAPR 2009

Optimal control approach to robust control of nonlinear systems using neural network based HJB solution

A power transformer, when energized at no-load, may have transient currents up to 100 times that of the steady state magnetizing current. This inrush current has several detrimental effects on power quality and may damage sensitive equipment connected to the system. In this paper, a power electronic based control circuit is developed, which estimates the last remnant and, utilizing this data, it controls the next re-energization instant to achieve inrush free switching. An equivalent circuit model of a transformer is also presented to simulate the transient dynamic performance of a transformer for any arbitrary switching operation. © 2009 The Berkeley Electronic Press. All rights reserved.

Fulltext

International Journal of Emerging Electric Power Systems

Magnetizing switching inrush: Estimation and a novel circuitry for inrush elimination

Solid-state electronics

Drain current model for nanoscale double-gate MOSFETs

Selected Mapping (SLM) technique is one of the promising PAPR reduction techniques for Orthogonal Frequency Division Multiplexing (OFDM). But this reduction technique results in a huge amount of computation complexity which is costly and time consuming. In this paper, Riemann sequences are used as a phase vectors along with the thresholding of the power amplifier(PA). The default index of the phase sequence is used to reduce the computational complexity of SLM technique. The default index of a phase sequence refers to the starting index for the phase vectors in the SLM scheme. This index is derived from the experimentation results. The Matlab simulations show that the complexity has been reduced by 98 percent if the threshold value of PA is around 3.0dB.

Proceedings of INDICON 2009 - An IEEE India Council Conference

A low complexity SLM technique for PAPR reduction in OFDM using Riemann sequence and thresholding of power amplifier

AlN films were grown on silicon by DC reactive magnetron sputtering and Al/AlN/Si structures were fabricated to study the influence of post metalization annealing (PMA) and UV light. Thereafter, the samples were annealed at 350 oC for 30 minutes in presence of argon gas. Reduction of hysteresis as well as interface state density was observed as a result of PMA. On the other hand, a ledge appeared in C-V curves, which became prominent with light intensity. The leakage current increased significantly as a result of photo generated charge carriers.

Optoelectronics and Advanced Materials, Rapid Communications

Opto-electrical properties of sputtered AlN films

We have studied surface and structural properties of micro/nanoporous silicon, synthesized by electrochemical etching of ptype Si (100) with different etching conditions. SEM studies reveal tunable pore sizes from 200 nm to 1.5 μm for etching time 5 to 30 min, and the thickness of pore walls decreases upto 20 nm for 30 min etching. AFM investigations reveal increase in roughness of the porous structure with increase in etching time and saturate around 250 nm at higher etching time. X-ray diffractogram of porous Si surface for etching time 20 min shows the appearance of two peaks at 2θ = 69.13° and 69.33°. For 30 min etching time a broad peak is observed at 2θ = 69.39°. The broadening may due to the size distributions of pore walls, and up ward shifts may due to relaxation of strain in the porous structure. FTIR investigations show the presence of Si-H bending in Si3-SiH groups at 624 cm-1, Si-O stretching in O-Si-O in between 1056-1160 cm -1. The bands at 2958, 2927, and 2856 cm-lare related to C-H stretching of CH3, CH2, and CH groups, which probably come from residual of HF-dimethylformamide.

Journal of Optoelectronics and Advanced Materials

Fabrication and surface modification of micro/nanoporous silicon

Tungsten oxide films were produced using reactive rf magnetron sputtering. In this work, nitrogen doping was used to modify structural and, optical properties of the material in the presence of two inert gases (argon and helium). Substituting helium gas with argon results in a decrease in the particle sizes and thus affects the band gap values. Bandgap values were obtained over the range of 2.43 to 3.01 eV via incorporating oxygen-nitrogen-argon/helium mixtures in the gas ambient. It was also observed that the atomic mass of the sputtering gas plays a major role for changing the primary crystallite size as well as the surface morphology and texture. © 2009 Elsevier B.V. All rights reserved.