Department of Electrical Engineering

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IIT Jodhpur

This paper presents an interesting application of magnetic levitation system using discrete sliding mode control. There is a limited literature available for sliding mode control as applied to magnetic levitation system. In this work a model of linearized magnetic levitation system having small magnetic disc and cylinder with light weight is considered. As a part of review PD control and full state feedback with pole placement and Kalman estimator are presented. A discrete sliding mode control with multi-rate output feedback is then investigated for the present application. To mitigate chattering, discrete time power rate reaching based algorithm is applied. Numerical result for nonlinear system is also shown. In all the cases, inherently unstable system is shown to exhibit stability and stable initial condition response compared to the uncompensated system. © 2010 IEEE.

World University root node

Proceedings of the 2010 11th International Workshop on Variable Structure Systems, VSS 2010

Discrete time sliding mode control with application to magnetic levitation system

Sliding mode observer has unique properties, in that the ability to generate a sliding motion on the error between the measure plant output and the output of the observer ensures that a sliding mode observer produces a set of state estimates that are precisely commensurate with the actual output of the plant. Sliding mode observer exists for bounded initial conditions and also observer gain has to be changed adaptively for varying initial conditions. To overcome these problems we have proposed a new methodology by combining Luenberger observer with the Sliding mode observer. Sliding mode observer guarantees the finite time convergence of the output error and also Robust to matched disturbances. ©2010 IEEE.

ICECE 2010 - 6th International Conference on Electrical and Computer Engineering

A new approach for observer design with application to micro aerial vehicle

This paper proposes a discretization behavior of nonlinear sliding surface based algorithms. Recently nonlinear surfaces are proposed by the authors to improve transient performance of continuous and discrete-time uncertain systems. The nonlinear surface changes system's closed loop damping ratio as output approaches the setpoint. In this paper we propose a nonlinear surface for the system represented by delta operator approach which unifies our continuous-time and discrete-time results. © 2010 IEEE.

A nonlinear sliding surface for discrete-time uncertain systems

This paper presents an enhancement method based on human visual characterstics (HVC) for medical images. In medical field images suffer from poor contrast and sometimes information is hidden in dark areas, due to this we are not able to extract information from them. We are presenting a method which takes care of these factors. According to HVC, human eyes are more sensitive towards plenty of details or great changings and less sensitive to smooth regions. So we divide the images in smooth area and detail area by discrete wavelet transform (DWT), and then use different processing methods for these areas according to HVC. Moreover, our experimental results validate that the proposed method performs better than conventional histrogram equalization method. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Proceedings of SPIE - The International Society for Optical Engineering

Wavelet transform based medical image enhancement using human visual characteristics

This paper presents an algorithm for contrast enhancement of medical images since the same is highly desirable for better medical diagnosis. The current methods use local enhancement techniques but suffer with the drawback of high complexity and over enhancement of the input image. Over enhancement essentially adds some information which may lead to a wrong diagnosis and the cost can be human life. In this paper we are making a very careful use of Human Visual Characteristics (HVC) for enhancement of such images. This is done by first studying characteristics of medical images and then segmenting it using HVC into the image into several overlapping blocks. These segmented blocks are enhanced based on the characteristics of the medical images. We also propose an algorithm for enhancement of color medical images. For this we first decompose the color image into Hue, Saturation and Intensity (HSI) component and propose two different algorithms to be applied on S and I components. In order to validate the effectiveness of the proposed method we compared our results with conventional histogram equalization method and found the promising results. Copyright © 2011 ACTA Press.

Proceedings of the 7th IASTED International Conference on Biomedical Engineering, BioMED 2010

Medical image enhancement algorithm based on local contrast enhancement and human visual characteristics

Porous silicon (PS) samples were prepared under different anodization conditions and correspondingly the sensor parameters were studied for organic vapours like methanol, ethanol, propanol, acetone and benzene at low ppm level using capacitive measurements. The surface morphology of the samples was characterized by scanning electron microscopy (SEM), whereas Raman spectroscopic studies were made to identify the surface species formed due to surface passivation. Selective response was observed for either methanol or ethanol depending on the combined effect of the pore morphology of PS, its surface passivation and the concentration dependent molecular kinetics in vapour phase. A probabilistic approach of the concentration dependent vapour molecular kinetics is demonstrated to explain the sensor performance and selectivity studies. © 2010 Elsevier B.V. All rights reserved.

Physica E: Low-Dimensional Systems and Nanostructures

Organic vapour sensing by porous silicon: Influence of molecular kinetics in selectivity studies

The present work explores the temperature dependent transport behavior of n-InN nanodot/p-Si (100) heterojunction diodes. InN nanodot (ND) structures were grown on a 20 nm InN buffer layer on p -Si(100) substrates. These dots were found to be single crystalline and grown along [001] direction. The junction between these two materials exhibits a strong rectifying behavior at low temperatures. The average barrier height (BH) was determined to be 0.7 eV from current-voltage-temperature, capacitance-voltage, and flat band considerations. The band offsets derived from built-in potential were found to be Δ E C =1.8 eV and Δ EV =1.3 eV and are in close agreement with Anderson's model. © 2010 American Institute of Physics.

Fulltext

Applied Physics Letters

Temperature dependent transport behavior of n -InN nanodot/p-Si heterojunction structures

Signal Integrity (SI) and Power Integrity (PI) are the most critical issues for higher operational speeds in semiconductor industry. This work identifies and optimizes the parameters of board, package and termination environment, influencing the signal integrity and power integrity of serial link. System level model has been created for USB HSLINK taking into account the external parameters like board, package, measurement environment which influence the performance of the channel. Parameters variations appearing from manufacturability constraints, material property constraints, design tolerance etc affecting the serial link performance has been optimized using Taguchi method based on statistical co-analysis. Using the Taguchi statistical techniques, sensitivity analysis on parameter variations affecting HSLINK performance is analyzed and optimized for desired performance. ©2010 IEEE.

2010 IEEE International Conference on Networked Embedded Systems for Enterprise Applications, NESEA 2010

Robust optimization of serial link system for signal integrity and power integrity

This paper proposes a protection scheme based on Wavelet Multi Resolution Analysis and Artificial neural network which detects and classifies various possible stator winding fault of a three-phase induction motor such as inter turn faults, line to ground faults and line to line faults. The wavelet decomposition of three-phase stator currents is carried out with Bior5.5. The maximum value of absolute peak dl coefficients of three-phase currents is defined as fault index which is compared with a predefined threshold to detect the fault. The normalized peak dl coefficients of these currents are fed to a Feedforward neural network to classify various faults. The algorithm has been tested for various incidence angles and proved to be simple, reliable and effective in detecting and classifying the various stator winding faults. © 2010 IEEE.

Proceedings of the 2010 5th IEEE Conference on Industrial Electronics and Applications, ICIEA 2010

Wavelet ANN based stator internal faults protection scheme for 3-phase induction motor

A series of highly soluble donor-acceptor (D-A) copolymers containing N-(3,4,5-tri-n-decyloxyphenyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP) or N-(2-decyltetradecyl)-dithieno[3,2-b:2′,3′-d]pyrrole (DTP′) as donor and three different acceptors, 4,7-dithien-2-yl-[2,1,3]- benzothiadiazole, 4,9-dithien-2-yl-6,7-di-n-hexyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline and 4,8-dithien-2-yl-2λ4δ2- benzo[1,2-c;4,5-c′]bis[1,2,5]thiadiazole (BThX, X = BTD, TQHx2, BBT, respectively) were synthesized by Stille coupling polymerizations. The optical and electrochemical properties of these copolymers were investigated, along with their use in field-effect transistors and photovoltaic devices. The band gaps (eV) estimated from UV-vis-NIR spectra and electrochemical measurements of the copolymers varied from ca. 1.5-0.5 eV, and were consistent with quantum-chemical estimates extrapolated using density functional theory. Oxidative and reductive spectroelectrochemistry of the copolymers indicated they can be both p-doped and n-doped, and three to four differently colored redox states of the polymers can be accessed through electrochemical oxidation or reduction. The DTP-BThBTD and DTP-BThTQHx2 copolymers exhibited average field-effect hole mobilities of 1.2 × 10-4 and 2.2 × 10-3 cm2/(Vs), respectively. DTP-BThBBT exhibited ambipolar field-effect characteristics and showed hole and electron mobilities of 1.2 × 10-3 and 5.8 × 10-4 cm 2/(Vs), respectively. Bulk heterojunction photovoltaic devices made from blends of the copolymers with 3′-phenyl-3′H-cyclopropa[1,9] (C60-Ih)[5,6]fullerene-3′-butanoic acid methyl ester (PCBM) (1:3 weight ratio) exhibited average power conversion efficiencies as high as 1.3% under simulated irradiance of 75 mW/cm2. © 2010 The Royal Society of Chemistry.