Faculty Publications
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Item Parameter estimation of PMSM using adaptive backstepping technique(IEEE Computer Society, 2014) Prashanth, K.V.; Girisha Navada, H.Estimation of unknown parameters in non-linear systems is a very crucial part in the adaptive control. In this paper an adaptive backstepping procedure is discussed for the estimation of parameters of Permanent Magnet Synchronous Motor drive(PMSM) viz. variation of d-q axis inductances and load torque. Also, a non-linear control scheme using adaptive backstepping technique for speed control of PMSM drive is presented. Stability of the system is ensured by Lyapunov stability theory. Simulation of speed controlled PMSM drive along with the control technique is carried out using MATLAB/Simulink software. The system is simulated for different operating conditions like variation in load and reference speed. © 2014 IEEE.Item Predictions of two popular closed-form models for unsaturated hydraulic conductivity (K) are compared with in situ measurements made in a sandy loam field soil. Whereas the Van Genuchten model estimates were very close to field measured values, the Brooks-Corey model predictions were higher by about one order of magnitude in the wetter range. Estimation of parameters of the Van Genuchten soil moisture characteristic (SMC) equation, however, involves the use of non-linear regression techniques. The Brooks-Corey SMC equation has the advantage of being amenable to application of linear regression techniques for estimation of its parameters from retention data. A conversion technique, whereby known Brooks-Corey model parameters may be converted into Van Genuchten model parameters, is formulated. The proposed conversion algorithm may be used to obtain the parameters of the preferred Van Genuchten model from in situ retention data, without the use of non-linear regression techniques.(Elsevier, Field evaluation of unsaturated hydraulic conductivity models and parameter estimation from retention data) Nandagiri, L.; Prasad, R.1996Item In the present study, various ocean wave parameters are estimated from theoretical Pierson-Moskowitz spectra as well as measured ocean wave spectra using backpropagation neural networks (BNN). Ocean wave parameters estimation by BNN shows that the correlations are very close to one. This substantiates the use of neural networks (NN). For Indian coast, Scott spectra are used as it reasonably represents the measured spectra. The correlations of NN and Scott spectra are also compared. Once the network is trained, the ocean wave parameters can be estimated for unknown measured spectra, whereas significant wave height and spectral peak period are required to first generate the Scott spectra and then estimate other ocean wave parameters. © 2005 Elsevier Ltd. All rights reserved.(Ocean wave parameters estimation using backpropagation neural networks) Mandal, S.; Rao, S.; Raju, D.H.2005Item A new approach for channel blind identification based on second order cyclostationary statistics and the group delay has been proposed. In this, two methods are proposed. In both the methods, the correction is applied to the basic phase estimate for both the poles and zeros, in the group delay domain. The basic phase estimate is derived from the spectral correlation density (SCD) of the system output. In the first method, the phase correction is based on magnitude group delay. In the second method, not only the phase correction but also an improved system magnitude estimate of better variance and frequency resolution is derived based on modified magnitude group delay. The results indicate a significant improvement in performance for both the methods. For the first method in the absence of noise, the percentage normalized mean square error is reduced by about 85% over that of the existing non-parametric method. The second method in the presence of noise (SNR=5 dB), provides a reduction of 74% over the existing non-parametric method and 57% over the existing combined parametric and non-parametric methods. © 2005 Elsevier B.V. All rights reserved.(Channel blind identification based on cyclostationarity and group delay) Narasimhan, S.V.; Hazarathaiah, M.; Giridhar, P.V.S.2005Item Wind tunnel experiments were conducted on a series of two-dimensional perforated plates normal to an air stream to study the characteristics of unsteady wake pressures and to ascertain the parameters amongst which a certain level of correlation can be established. The velocity ranged from 5 m/s to 15 m/s in the present study. The pressure field gets significantly modified as the perforation level increases. The present study is concerned with three plates with perforation level of 0%, 25% and 35%. There appears to be a correlation between the maximum normalized value of the RMS pressure fluctuation levels, base pressure and the perforation level of the normal plate.(Experimental investigation of the 2-D flow field associated with bleed flows) Yaragal, S.C.; Govinda Ram, H.S.; Tamura, Y.2005Item Polymer-based composite materials possess superior properties such as high strength-to-weight ratio, stiffness-to-weight ratio, and good corrosive resistance and therefore, are preferred for high-performance applications such as in the aerospace, defense, and sport goods industries. Drilling is one of the indispensable methods for building products with composite panels. Drilling tests have been conducted on glass fiber-reinforced plastic composite GFRP laminates using an instrumented CNC milling center. Machining parameters such as drill size, feed rate, and cutting speed have been observed for damage-free drilling of GFRP materials. A series of drilling experiments have been conducted on glass fiber-reinforced polyester laminates and the responses experienced such as thrust force and torque as functions of feed rate and drill size have been characterized to develop a semiempirical relationship which correlated well with an established model in terms of cutting parameters. Results indicated that experimental values correlated better with the model of thrust for 6mm drill size than for 10mm and torque correlated better for lower feed ranges than for the higher feed ranges. © 2005 Sage Publications.(Machining of fiber-reinforced thermoplastics: Influence of feed and drill size on thrust force and torque during drilling) Mohan, N.S.; Ramachandra, A.; Kulkarni, S.M.2005Item The objective of the present study is to predict analytically the material perforation under hyper velocity impact. Hyper velocity impact is a complex phenomenon involving wave propagation, penetration and responses exceeding elastic limits, leading to hydrodynamic behaviour. A general-purpose program (GPP) that permits a combination of non-linear finite element technique and explicit integration scheme, is employed for the simulations. The geometry of perforation is computed for various projectiles with different incident angles, impact velocities and materials. The computed values are compared with test results available in the literature. The results indicate excellent agreement with the measurements and give good insight into the effect of various parameters on the perforation size and geometry.(Perforation under hyper velocity impact - A prediction using finite element technique) Suhas, M.; Samgeeth, R.; Veenaranjini, S.M.; Singh, G.2005Item Symmetric multistep methods with zero phase-lag for periodic initial value problems of second order differential equations(2006) Saldanha, G.; Achar, S.D.We present in this paper two-step and four-step symmetric multistep methods involving a parameter p to solve a special class of initial value problems associated with second order ordinary differential equations in which the first derivative does not appear explicitly. It is shown that the methods have zero phase-lag when p is chosen as 2? times the frequency of the given initial value problem. The periodicity intervals are given in terms of expressions involving the parameter p. As p increases, the periodicity intervals increase and for large p, the methods are almost P-stable. © 2005 Elsevier Inc. All rights reserved.