The Modares Journal of Electrical Engineering
Volume:11 Issue: 2, 2011

In this paper torque ripple in switched reluctance motor is studied. The presented method in this paper for minimization of torque ripple is based on suitable machine structure obtained from the genetic algorithm (GA) and suitable machine driver. In the presented paper، the parameters of one machine are chosen as the reference machine parameters. Then some parameters of machine are chosen، which have no effects on the characteristics of mechanical، power and volume of reference machine. The desirable machine is simulated by finite element software، and then the torque characteristics are obtained for different machine structure with various machine parameters. Finally، with GA the best parameters for the design of machine with minimum torque ripple are chosen. So this paper presented for the first time an accurate method by finite element method in the process of machine design by GA. The finite element method used in the previously studies in the design of machine only for machine analysis، but in this paper finite element method is used in the process of machine design. So this method of machine design can be replaced to a conventional method. In this paper، the design of SRM driver is presented based on the best machine structure which is chosen from GA. So، the profile of machine torque for this structure has minimum deviation from the ideal torque without the ripple.

Main problem for airborne radars in detecting of ground targets is clutter. Space-Time Adaptive Processing is newest method to confront of this signal. A two-dimensional filter puts zeros in Doppler and spatial frequencies related to spectrum of clutter. In calculating of weight vector، covariance matrix of interference signal plays an important role. In practice this matrix is unknown and must be estimated. In this paper adaptive angle-doppler compensation method (AADC) in Bistatic airborne radar is extended to achieve higher SNR in output. In this method compensation in spatial and temporal frequencies is repeated in several stages to increase homogeneity of secondary data used in estimation of covariance matrix. In this new approach subspaces related to clutter covariance matrix decomposition for secondary data are aligned with subspaces of covariance matrix in test range-gate. Simulations in MATLAB shows 3 dB improvement for new approach in comparison to conventional AADC for a spacial scenario

In power systems، distance relays are utilized widely as main protection of the high voltage transmission lines، and their safe operation has significant effects on health of the components and stability of the system. Power swing is a phenomenon that can cause mal-operation of the distance relays while there is no fault in the system. In this paper، a protection scheme based on Support Vector Machine (SVM) classifier is proposed for the digital distance relays to distinguish between power swings and faults. In this work، simulations are done on a study system and related train and test patterns are generated to analyze performance of the proposed method. Also، the proper structure of the SVM classifier is investigated using the train and test patterns. The train and test patterns contain information of the different power swing conditions and symmetrical and asymmetrical types of faults. The results of the tests and simulations confirm the efficiency of the proposed protection algorithm.

Fuild models as one of the precise techniques for gas discharge modelling require swarm parameters. In this paper the continuty equations for electron transport and energy transport to calculate these parameters via electron energy distribution funaction (EEDF) resulted from two-terms approximation of boltzmann equation، are developed. The simualtion and calculation results containing mobility and diffusion cefficient، mobility and energy diffusion coefficient، Townsend coefficient، rate coefficient، consumed power (including elastic and inelastic power loss، the requied power for growth of electrons) for different types of gases (including argon، nitrogen، oxygen، SF6 and air) are presented and evaluated. Also accuracy of some common approximations e. g. assupmtion a Maxwellian EEDF are studied.

In this paper، we propose a novel method for tracking multiple objects in video sequences. this approach can track objects in crowded scenes with occlusions and random change directions of object movements، efficiently. this method is an extension to particle filter tracking approach that we named it 3-D particle filter. in the proposed method، the features of objects that cannot be used in the process of posterior probability estimation in particle filter، are used for as third dimension and improve the estimation of 2-d particle filter in each frame. we test our method and compare it with 3 other particle filter methods on the famous data sets such as PETS09. The results show the improvement of accuracy and a reduction of error in tracking، about 12%

In this paper، the effect of window weighting functions، such as Hamming، Hanning and Nuttulwin، on the Oppermman code is investigated. These codes are used in the poly phase pulse compression technique in radar applications. The results indicate that weightings reduce sidelobes and false alarm extremely. In addition، the target detection ability is increased in this code.