Department of Electrical Engineering

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IIT Jodhpur

In this paper, a novel discrete-time integral sliding-mode control (DISMC) scheme for connection-oriented communication network is proposed. Network is modeled as an nth order discrete system whose available bandwidth variations at the bottlenecked link act as an exogenous unmatched disturbance. The proposed scheme is characterized by discrete-time integral sliding manifold which inherits the desired properties such as elimination of reaching phase, full order sliding manifold with pole assignment etc. In particular, comparing with the existing discrete flow control scheme, the new scheme ensures more precise tracking with O(T2) steady-state error for state regulation with widely adopted delay-based disturbance estimation. Surface parameters are so chosen to minimise the effect of unmatched uncertainty. Simulation results shows that discrete-time ISMC achieves more effective control performance under the adverse influence of unmatched disturbances, meanwhile eliminating the reaching phase. © 2012 IEEE.

World University root node

2012 12th International Conference on Control, Automation, Robotics and Vision, ICARCV 2012

Discrete-time integral sliding-mode flow control for connection-oriented communication networks

Close-proximity (10-150 m) formation flying using low cost, small satellites is an emerging field. In such missions, control of satellite formations is a challenging problem and requires robust on-board control systems. This paper describes a modified approach to designing Sliding Mode Control (SMC) for satellite formation and reconfiguration missions, in deep space with external disturbances. Based on this dynamic model, a new approach for implementing path planning of satellites using Artificial Potential Field (APF) method is presented in this paper. This paper discusses stability of the sliding surfaces designed using gradient of the potential function for the closed loop system. The stability analysis is demonstrated by presenting a scenario in which six satellites aggregates to form an octahedron formation and subsequently reconfigure to a hexagon formation. This paper thus presents further progress in the state of-the-art of path planning and control for the framework of satellite formation and reconfiguration missions. © 2012 IEEE.

Proceedings of IEEE International Workshop on Variable Structure Systems

Stability analysis of small satellite formation flying and reconfiguration missions in deep space

This paper proposes a new interpolation approach for obtaining high resolution (HR) images from its low resolution (LR) images. We are using the Least Squared based block by block prediction scheme to estimate the predictors using Jacobian iteration method. In spite of Jacobian's Iterative property of convergence for diagonally dominant matrices only, our proposed method uses this property effectively for all types of matrices, and found a set of prediction coefficients using a small number of iterative steps. Due to its lesser computational cost it can be used in real time applications too. Use of iterative methods like Jacobi gives an advantage of its application over images which gives singular matrices during operation. Experimental results indicates that the proposed algorithm gives better quantitative performance as compared to other conventional interpolation techniques. © 2012 IEEE.

2012 19th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2012

An efficient 2-D jacobian iteration modeling for image interpolation

In this paper we propose a new prediction scheme for lossless compression of fingerprint images. The proposed method uses the symmetric/near symmetric property of such images. The scheme first divides the image horizontally into two halves and then the upper half is divided vertically in another two halves; resulting in three parts of the given image. It is observed that the two halves of the upper part are highly correlated. In view of this observation, the pixels of the right half are predicted using those in the left half and also in the present half. On the other hand, pixels of the left half and those of the bottom half are classified as per slope bins of GAP and then LS based predictor is used with respective classes. Prediction performance of the proposed scheme is found to be significantly better than many competitive and popularly used methods. © 2012 IEEE.

International Conference on Signal Processing Proceedings, ICSP

A Novel prediction algorithm for lossless compression of fingerprint images

Predictor based algorithms reported in literature uses only causal pixels and hence a non-symmetrical predictor structure for prediction. We observed that the performance of predictor is highly dependent on the predictor structure used. In view of this, we propose a novel interpolation based prediction scheme that enables us to use symmetrical predictor structure. In this sense, we have also used non causal pixels in our scheme. Also, from various interpolation algorithms available, we selected a simple one to ensure decoder simplicity, without any significant loss in performance. From performance evaluation, we found that our algorithm is significantly better in terms of compression performance as compared to some of the computationally complex methods. © 2012 IEEE.

ISCAS 2012 - 2012 IEEE International Symposium on Circuits and Systems

Interpolation based symmetrical predictor structure for lossless image coding

Recently a lot of interpolation algorithms are proposed, but these interpolation algorithms are highly computationally expensive. Hence these algorithms cannot be implemented and used in real time applications. In view of real time applications we have proposed a computationally simple interpolation algorithm. In our proposed algorithm the unknown pixels are categorized into various bins depending upon the characteristic of the neighboring pixels (activity level) and for each bin fixed prediction parameters are used for prediction. We have presented different set of fixed predictors for both smooth type and edgy type of images. We have also proposed a modified algorithm in which selection of prediction parameter is done on block by block basis instead of image basis. Our proposed algorithm gives much better qualitative and quantitative performance as compared to other computationally simple interpolation algorithms.

A Low Complex Context Adaptive Image Interpolation Algorithm For Real-Time Applications

Studies were carried on the growth behavior of InN nanodots by plasma assisted molecular beam epitaxy on bare Si(100) substrates and their structural, optical, electrical properties. The growth was carried out by two different methods such as, (i) mono-step growth process at a low temperature and a (ii) bi-step growth process with the combination of low and high temperatures for the formation of single crystalline nanodots with well defined crystallographic facets due to cluster migration. Low temperature photoluminescence shows a free excitonic (FE) luminescence at 0.80 eV. The Raman spectroscopy and X-ray diffraction studies reveal that the nanodots as well as the film were of wurtzite structure and strain free. © 2012 SPIE.

Proceedings of SPIE - The International Society for Optical Engineering

Wurtzite InN nanodots on Si(100) by molecular beam epitaxy

We present an extensive study on the structural, electrical and optical properties of InN thin films grown on c-Al 2O 3, GaN(130 nm)/Al 2O 3, GaN(200 nm)/Al 2O 3 and GaN(4 μm)/Al 2O 3 by using plasma-assisted molecular beam epitaxy. The high resolution X-ray diffraction study reveals better crystalline quality for the film grown on GaN(4 μm)/Al 2O 3 as compared to others. The electronic and optical properties seem to be greatly influenced by the structural quality of the films, as can be evidenced from Hall measurement and optical absorption spectroscopy. Kane's k.p model was used to describe the dependence of optical absorption edge of InN films on carrier concentration by considering the non-parabolic dispersion relation for carrier in the conduction band. Room temperature Raman spectra for the InN films grown on GaN show the signature of residual tensile stress in contrast to the compressive stress observed for the films grown directly on c-Al 2O 3. © 2012 Elsevier B.V.

Journal of Crystal Growth

Influence of GaN underlayer thickness on structural, electrical and optical properties of InN films grown by PAMBE

This paper presents the design, analysis and simulation of metal-to metal contact series rf-MEMS switch for its pull-in voltage optimization. Fixed fixed flexure is used as a switching element and the Pull-in voltage is optimized for generating a force to obtain a stable contact resistance. Au is used as the contact material. The simulated value of the pull-in voltage (V pi) is approximately 10.20 V. At the pull-in voltage the area occupied under contact is 8.89 m 2 and the value of contact force is 1.84 N. The switch pull-in voltage value is optimized at a value of 23 V giving contact area of 924 m 2 and contact force of 31.55 N. © 2012 IEEE.

2012 International Conference on Computing, Communication and Applications, ICCCA 2012

Design and pull-in voltage optimization of series metal-to-metal contact RF MEMS switch

Contact resistance has always been an issue for semiconducting carbon nanotubes (CNT). This paper presents a comparative study on open-ended semiconducting carbon nanotube (4, 0) two-probe systems with metal electrodes of platinum, copper and gold. The local density of states and transmission coefficients has been calculated to explain the electronic structure and transmission properties of two-probe systems. Contact resistance for each two-probe system has been derived from their current-voltage characteristics. Calculations are based on first-principle quantum mechanical density functional, matrix Green's function methods and Landauer-Buttiker formula. Contact resistance is calculated to be highest for the Au electrode while it is least for the Pt electrode. © 2012 Springer Science+Business Media New York.