نشریه مهندسی برق
سال چهل و دوم شماره 2 (پیاپی 64، پاییز و زمستان 1391)

Robotic laparoscopic grasper is a surgical tool with minimal invasion. In this robot،achieving the goals like precise tracking، stability and disturbance rejection is very important and this makes selecting a suitable controller to be one of the most important issues in these systems. In this paper، first the stages of modeling and simulating of laparoscopic robot will be discussed and the reasons for selecting the appropriate materials for different parts of it will be explained. Then the problem of nonholonomic trajectory planning and conditions for proposed pfaffian constraint to be holonomic or nonholonomic will be studied. With regard to the nonholonomic structure of explained robot، using the Ritz estimation، a controller for optimal steering of grasper will be designed. This part of the robot، which performs the main part of the surgery، be controlled based on the uncertain properties of the tissues of patients body. Simulation results validate the efficiency of the proposed method for steering and controlling of the robot.

Aerial image interpretation is one of new rising high-tech application fields، and it’s proverbially applied in the military domain. Accordingly an algorithm based on combination of fractal features and morphological operations، for automatic detection of man-made objects such as: aircraft، tanks and war machines in CCD (Chargecoupled device) aerial images is presented. In this paper، the fractal features include D (fractal dimension) and K (Ddimension area) are theoretically studied، Then by applying «the blanket covering method» the fractal features and their images are calculated. The histogram of feature images is used for classifying the images into two parts: artificial objects and natural background. Then، morphological processing is done on segmented images to determine the exact location and number of man-made objects. The results have revealed that the proposed method in comparison with the previous methods has higher accuracy on determining the location and number of man made objects from CCD images.

In bad weather condition، doubly-fed induction generators (DFIG) are injecting harmonic and interharmonic components into the power networks. Since frequency range and resolution needed for harmonic and interharmonic measurements are very different، measurement of these parameters are usually done separately. Therefore in this paper a hybrid method for simultaneous identifying of these components is presented. For this purpose، first the voltage envelope and real fundamental frequency of waveform are obtained by an extended kalman filter and then interharmonic and harmonic components are respectively calculated by a linear kalman filter and adjusted window DFT. The main advantage of this method is simultaneous measurement of harmonic and inter harmonic components by a suitable accuracy and computational burden in compare to separated implementation of each of these methods. Finally، the performance of proposed method is evaluated by synthesized waveforms and the voltage waveforms of DFIG in a 34-bus Italy network. The results show that the proposed method is highly capable in analysis of harmonic and interharmonic pollution of power networks in presence of DFIGs.

In the present time، one of the significant thought-provoking approaches to digital images، which has been adopted because of the existence of the semantic gap، is the automatic image annotation. In this paper، we present a model، which combines regional contexts and visual topics to automatic image annotation. The difference of the regional contexts and visual topics is due to their function and application over an image. Regional contexts represent the associations of different regions with each other while visual topics are responsible for the global distribution of different topics. Regarding the associations of different regions with each other in an image is very useful for image annotation، since these regions form the exact explanation of the image semantics. An important fact، which was not considered in the former image annotation methods. The proposed model extracts regional contexts and visual topics from the image، and incorporates them by MCDM (Multi Criteria Decision Making) approach based on TOPSIS (Technique for Order Preference by Similarity to the Ideal Solution) method. Regional contexts and visual topics are learned by PLSA (Probability Latent Semantic Analysis) approach from the training data. The efficacy and importance of integrating these two kinds of information for the image annotation are apparently demonstrated in the experiments on 5k Corel images.

Recently، multi-perspective target coverage problem، which provides more information about the occurred targets in the monitored area by considering dimensions for them، is taken into account by many researchers. The main goal of this problem is selecting the camera sensor nodes and putting them in active mode so that they maximize multi-perspective target coverage (covering target from multiple viewpoints) and also minimize angle overlap (covering the same angles of target with different nodes). According to literature، existing solutions exploit central methods to solve the multi-perspective target coverage problem. However، delay in central methods is not acceptable for realizing many applications with mobile targets. Therefore، in this paper a decentralized algorithm named Distributed Multi perspective Target Coverage (DMTC) is proposed. Utilizing this algorithm، each camera sensor node decides whether to be active or not، only based on information provided by the neighbor nodes. Simulation results show that proposed algorithm provides maximum multi-perspective target coverage with minimum delay and acceptable angle overlap in comparison with an exact method running centrally in the base station.

Now days using of distributed generation (DG) are growing and regardless of optimum location and size، they can''t be useful. In this paper، the HS (Harmony Search) algorithm is used for optimum placement and sizing of DGs in order to decrease the losses and increase the reliability in a standard grid. The proposed method for sizing and sitting of the DG capacities in the grid is so proper and useful in comparison with the conventional method. In suggested procedure، the DG is used to compensate the lost power of several nodes that are disconnected from the grid، while the conventional method tries to compensate the lost power of the node which DG connected to it and so this subject results in optimum value of objective function. The power losses reduction، reliability improvement and a combination of them are objective functions that considered in this paper. In this paper، the simulation results based on mentioned objective functions are presented and compared together. The presented simulation results show the validity and effectiveness of suggested method in optimum placement and sizing of DGs. Some flexibility has been considered in the provided program in order to solve the optimum placement of DGs under real conditions. Heuristic