Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 7 Articles
A fuzzy controller for improving Fault Ride-Through (FRT) capability of Variable Speed Wind Turbines (WTs) equipped with\r\nDoubly Fed Induction Generator (DFIG) is presented. The controller is designed in order to compensate the voltage at the Point of\r\nCommon Coupling (PCC) by regulating the reactive and active power generated by WTs. The performances of the controller are\r\nevaluated in some case studies considering a different number of wind farms in different locations. Simulations, carried out on a\r\nreal 37-bus Italian weak distribution system, confirmed that the proposed controller can enhance the FRT capability in many cases....
To decode a long genome sequence, shotgun sequencing is the state-of-the-art technique. It needs to properly sequence a very\nlarge number, sometimes as large as millions, of short partially readable strings (fragments). Arranging those fragments in correct\nsequence is known as fragment assembling, which is an NP-problem. Presently used methods require enormous computational\ncost. In this work, we have shown how our modified genetic algorithm (GA) could solve this problem efficiently. In the proposed\nGA, the length of the chromosome, which represents the volume of the search space, is reduced with advancing generations, and\nthereby improves search efficiency.We also introduced a greedy mutation, by swapping nearby fragments using some heuristics, to\nimprove the fitness of chromosomes.We compared results with Parsons� algorithm which is based on GA too. We used fragments\nwith partial reads on both sides, mimicking fragments in real genome assembling process. In Parsons� work base-pair array of the\nwhole fragment is known. Even then, we could obtain much better results, and we succeeded in restructuring contigs covering\n100% of the genome sequences....
A new asymmetrical gate with application in target tracking is proposed. Proposed gate has asymmetric shape that has large\r\nprobability of target detection in the gate and has more advantages compared with elliptical gate. The gate is defined as the\r\nregion in which the tracked target is expected to exist and just observation vectors in the gate are used as target detection. An\r\nanalytical method to compute optimal size of gate is proposed and recursive estimation of asymmetric parameters of gate are\r\nstudied. Comparison between proposed gate and conventional elliptical gate showed the efficiency of the proposed method in\r\nmaneuvering target tracking applications and simulation results showed the proficiency of the proposed method....
Environmental sound recognition is an important function of robots and intelligent computer systems. In this research, we use\r\na multistage perceptron neural network system for environmental sound recognition. The input data is a combination of timevariance\r\npattern of instantaneous powers and frequency-variance pattern with instantaneous spectrumat the power peak, referred\r\nto as a time-frequency intersection pattern. Spectra of many environmental sounds change more slowly than those of speech or\r\nvoice, so the intersectional time-frequency pattern will preserve the major features of environmental sounds but with drastically\r\nreduced data requirements. Two experiments were conducted using an original database and an open database created by the\r\nRWCP project. The recognition rate for 20 kinds of environmental sounds was 92%. The recognition rate of the new method\r\nwas about 12% higher than methods using only an instantaneous spectrum. The results are also comparable with HMM-based\r\nmethods, although those methods need to treat the time variance of an input vector series with more complicated computations...
Lyapunov theory-based radial basis function neural network (RBFNN) is developed for traffic sign recognition in this paper to\r\nperform multiple inputs multiple outputs (MIMO) classification. Multidimensional input is inserted into RBF nodes and these\r\nnodes are linked with multiple weights. An iterative weight adaptation scheme is hence designed with regards to the Lyapunov\r\nstability theory to obtain a set of optimum weights. In the design, the Lyapunov function has to be well selected to construct an\r\nenergy space with a single global minimum. Weight gain is formed later to obey the Lyapunov stability theory. Detail analysis and\r\ndiscussion on the proposed classifier�s properties are included in the paper. The performance comparisons between the proposed\r\nclassifier and some existing conventional techniques are evaluated using traffic sign patterns. Simulation results reveal that our\r\nproposed system achieved better performance with lower number of training iterations...
The neurological mechanism used for generating rhythmic patterns for functions such as swallowing, walking, and chewing\r\nhas been modeled computationally by the neural oscillator. It has been widely studied by biologists to model various aspects\r\nof organisms and by computer scientists and robotics engineers as a method for controlling and coordinating the gaits of walking\r\nrobots. Although there has been significant study in this area, it is difficult to find basic guidelines for programming neural\r\noscillators. In this paper, the authors approach neural oscillators from a programmer�s point of view, providing background and\r\nexamples for developing neural oscillators to generate rhythmic patterns that can be used in biological modeling and robotics\r\napplications....
This paper treats a tuning of PID controllers method using multiobjective ant colony optimization. The design objective was to\r\napply the ant colony algorithm in the aim of tuning the optimum solution of the PIDcontrollers (Kp, Ki, and Kd) by minimizing the\r\nmultiobjective function. The potential of using multiobjective ant algorithms is to identify the Pareto optimal solution. The other\r\nmethods are applied to make comparisons between a classic approach based on the ââ?¬Å?Ziegler-Nicholsââ?¬Â method and a metaheuristic\r\napproach based on the genetic algorithms. Simulation results demonstrate that the new tuning method using multiobjective ant\r\ncolony optimization has a better control system performance compared with the classic approach and the genetic algorithms...
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