Electrical Engineering

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Power amplifier is one of the important elements of any attraction type levitation system. Due to the advancement in power electronics and control technology it is now possible to develop power amplifier which will have the properties like fast dynamics, large bandwidth, ability to carry large payload, energy efficient, high reliability and cost effective. Both linear and switching mode power amplifiers have been used in the field of DC electromagnetic suspension system. In this paper different possible switched mode power circuits for both single as well as multi-magnet based electromagnetic levitation system have been discussed and a comparative study has been made of the different topologies of power amplifiers based on their structure, working principle and experimental results. In the actual work design, fabrication and testing of both single and multi-magnet based electromagnetic levitation scheme has been made as a complete project. But in this paper the main focus is on the power amplifier. © 2008 Inderscience Enterprises Ltd.

World University root node

(SoE) School of Engineering

International Journal of Power Electronics

Some aspects of switching power amplifier used in electromagnetic levitation system

Materials Science and Technology: A Comprehensive Treatment

Effect of Multiphase Flow on Corrosion

Using fuzzy-rough hybrids, we have proposed a measure to quantify the functional dependency of decision attribute(s) on condition attribute(s) within fuzzy data. We have shown that the proposed measure of dependency degree is a generalization of the measure proposed by Pawlak for crisp data. In this paper, this new measure of dependency degree has been encapsulated into the decision tree generation mechanism to produce fuzzy-rough classification trees (FRCT); efficient, top-down, multi-class decision tree structures geared to solving classification problems from feature-based learning examples. The developed FRCT generation algorithm has been applied to 16 real-world benchmark datasets. It is experimentally compared with the five fuzzy decision tree generation algorithms reported so far, and the rough decomposition tree algorithm. Comparison has been made in terms of number of rules, average training time, and classification accuracy. Experimental results show that the proposed algorithm to generate FRCT outperforms existing fuzzy decision tree generation techniques and rough decomposition tree induction algorithm. © 2007 Springer-Verlag London Limited.

Pattern Analysis and Applications

FRCT: Fuzzy-rough classification trees

This paper proposes a novel control approach that incorporates a hybrid game strategy in Markov-game-based fuzzy control. Specifically, we aim at designing a "safe and universally consistent"controller that exhibits an ability to maintain performance against large disturbance and environment variations. The proposed hybrid control is a convex combination (based on experiential information) of "a variation of cautious fictitious play" approach and the "minimax" control approach implemented on a fuzzy Markov game platform. We show analytical convergence of Markov-game-based control in the presence of bounded external disturbances, and extend the analysis to show convergence of the proposed Markov-game-based hybrid control approach. Controller simulation and comparison against baseline Markov game fuzzy control and fuzzy Q-learning control on a highly nonlinear two-link robot brings out the superiority of the approach in handling severe environment and disturbance variations over different desired trajectories. This paper illustrates the possibility of obtaining "universal consistency," i.e., reasonable performance against severe environment and disturbance variations, by hybridizing "cautious fictitious play" with "minimax" approaches in Markov-game-based control. © 2008 IEEE.

IEEE Transactions on Fuzzy Systems

Hybrid game strategy in fuzzy Markov-game-based control

This paper describe the design principle of a dc attraction type electromagnetic suspension system where a hollow steel cylinder of 658 g mass is levitated under a fixed I-core (solenoid type) electromagnet with a single degree-of-freedom. Electromagnet exhibits non-linear force against distance characteristics and hence, this controller has been designed by using linear small perturbation model of the magnet at the desired operating point. In all previously reported papers 1-3 the system design has been done by considering a suitable voltage source as the exciting input to the magnet coil. In the present work, over all system order reduction has been tried by taking a controlled current source as the excitation for the magnet coil. The resulting system is simpler and has second order transfer function. The present work also reports a very simple power electronic converter suitable for this scheme of levitation. The proposed circuit uses only one power switch in contrast to commonly used asymmetrical H-bridge type converter4. The present circuit, though less energy efficient compared to the asymmetrical bridge converter will be quite cost effective for low power applications. The prototype has been successfully tested and levitation demonstrated.

Journal of the Institution of Engineers (India): Electrical Engineering Division

Design, implementation and testing of an electromagnetic levitation system

An attempt has been made to correlate the morphological and electrical properties of RF sputtered aluminum nitride (AlN), with target to substrate distance (D ts) in sputter chamber. AlN films, having thickness around 3,000 Å, were deposited on silicon substrates with different D tsvalues varying from 5 to 8 cm. XRD results indicated that the crystallinity of c-axis oriented films increase significantly with decrease in D ts and the FTIR absorption band of the films became prominent at shorter D ts. The surface roughness increased from 1.85 to 2.45 nm with that in D ts. A smooth surface with smaller grains was found at shorter D ts. The capacitance-voltage (C-V) measurements revealed that the insulator charge density (Q in) increased from 3.3 × 10 11 to 7.3 × 10 11 cm -2and the interface state density (D it) from 1.5 × 10 11 to 7.3 × 10 11 eV -1cm -2 with the increase in D ts. © Springer Science+Business Media, LLC 2007.

Journal of Materials Science: Materials in Electronics

Effect of inter-electrode spacing on structural and electrical properties of RF sputtered AlN films

The boiler is a very important component of a thermal power plant, and its efficient operation requires continuous online information of various relevant parameters. Furnace exit gas temperature (FEGT) is one such important design/operating parameter. Knowledge of FEGT is not only useful for design of convective heating surface but also helpful for operating actions and decision making. Its online information ensures improvement in economic benefit of the power plant. Non-availability of FEGT on the operator desk greatly limits efficient operation. In this study, a novel method of estimating FEGT using neural network is presented. The training data are first generated by calculating FEGT using heat balances through various heat exchangers. Prediction accuracy and fast response are major advantages in using neural network for estimating FEGT for operator information. Two types of feed forward neural modeling networks, radial basis function and back-propagation network, were applied and compared based on their network simplicity, model building and prediction accuracy. Results are verified on practical data obtained from a 210 MW boiler of a thermal power plant. © 2008 Elsevier Ltd. All rights reserved.

Energy Conversion and Management

Estimation of furnace exit gas temperature (FEGT) using optimized radial basis and back-propagation neural networks

IEEE transactions on electron devices

Drain current model including velocity saturation for symmetric double-gate MOSFETs

Closed form current and conductance model for symmetric double-gate MOSFETs using field-dependent mobility and body doping

In this paper, a Hamilton-Jacobi-Bellman (HJB) equation based optimal control algorithm is proposed for a bilinear system. Utilizing the Lyapunov direct method, the controller is shown to be optimal with respect to a cost functional, which includes penalty on the control effort and the system states. In the proposed algorithm, Neural Network (NN) is used to And approximate solution of HJB equation using least squares method. Proposed algorithm has been applied on bilinear systems. Necessary theoretical and simulation results are presented to validate proposed algorithm. © 2008 IEEE.