Mukhtiar Ali Unar

Automatic steering of ships using neural networks

Ship steering control system design presents challenges because the dynamic properties of the vessel itself vary significantly. The use of an artificial neural network as a controller which incorporates the properties of a series of conventional controllers designed for different operating conditions could provide an alternative to adaptive control or gain scheduling in this application. Local model network methods could also provide a basis for efficient modelling of the vessel over a range of operating conditions. The paper describes an investigation of radial basis function networks for ship steering control and of local model networks for representation of ship dynamics. Performance is demonstrated by a series of simulation studies. Copyright

Privacy Preserving Dynamic Pseudonym-Based Multiple Mix-Zones Authentication Protocol over Road Networks

In this paper, we propose an efficient dynamic pseudonymous based multiple mix-zones authentication protocol for privacy preservation to enhance security over road networks. Most of the existing protocols either utilize pseudonym based approaches with certificate revocation list that cause significant communicational and storage overhead or they use group signature based approaches, which are computationally expensive. In this paper, we present a dynamic pseudonymous based multiple mix-zones authentication protocol that only requires mobile vehicles to communicate with reported server for registration and dynamic pseudonym change. Furthermore, we formulate a mechanism to provide users with dynamic pseudonyms named as; base pseudonyms and short time pseudonyms, to achieve users’ privacy. Finally, we analyze our protocol by determining the communication cost as well as various attack scenarios to prove that our approach is most efficient and robust as compared to existing techniques.

A Novel Approach for the Control of Dual-Active Bridge DC-DC Converter

During these days high frequency dc-dc converters are frequently used in high Power Electronic applications. It is well known fact that the size of the passive components, such as inductors, capacitors and power transformers decreases as the frequency increases. It is well known that high-voltage converters in the power range of 1-10MW have excessive switching losses at the switching frequencies higher than 4 kHz. The favorable DC-DC converter is realized to be the Dual-Active Bridge when a bi-directional power flow is demanded; however the most important problem is to design an appropriate controller for this type of converter. Switch-mode power supplies represent a particular class of variable structure systems (VSS) and have advantage of non-linear control techniques developed for this class of systems. The sliding mode control can handle large power supply and load variations and provides good dynamic response and simple implementation. The sliding mode controller design has become famous choice for non-linear dynamic systems having class of uncertainties. Moreover, it is maximally robust to all unmatched uncertainties. In this paper the sliding mode control is reviewed and its applications to dc-dc converters are discussed.

Speech and Image Compression Using Discrete Wavelet Transform

Efficient speech and image compression solutions are becoming critical with the recent growth of data intensive, multimedia based applications. In this paper, we describe the application of the discrete wavelet transform (DWT) for analysis, processing and compression of multimedia signals like speech and image. More specifically we explore the major issues concerning the wavelet based speech and image compression which include choosing the optimal wavelet, decomposition levels and thresholding criteria. The simulation results prove the effectiveness of DWT based techniques in attaining an efficient compression ratio of 2.31 for speech and 2.67 for images, achieving higher signal to noise ratio (SNR), better peak signal to noise ratio (PSNR), while the retained signal energy is 99.9885% and the resulting signals are generally much smoother

APPLICATION OF ARTIFICIAL NEURAL NETWORKS FOR PREDICTING pH IN SEAWATER ALONG GAZA BEACH

Coastal water issues are gaining worldwide attention because of their impact on health and other environmental problems. This article is concerned with the comparison between artificial neural networks and statistical methods to predict the degree of acidity (pH) in the coastal waters along the Gaza beach. Multilayer perceptron (MLP) and radial basis function (RBF) neural networks are trained and developed with reference to three parameters (water temperature, wind velocity, and turbidity) to predict the level of pH in the seawater. Both networks were developed using the combination of the data collected from nine sites over a period of 4 years, including 294 samples for training and 90 samples for testing the performance of models. The results show that the MLP and RBF models have good ability to predict the pH level. Each networks performance was tested with different sets of data, and the results show satisfactory performance. Results of the developed networks were compared with the statistical regression method and found that the predictions of neural networks are better than the conventional methods. Predictions result show that artificial neural networks approach have good ability for the modeling of pH level in the coastal waters along Gaza beach. It is hoped that neural networks will prove to be a promising alternative to traditional methods used and can contribute in the improvement of the quality of seawater.

Estimation of Compensation Current Reference using Fuzzy Logic Controller for Three-Phase Hybrid Active Power Filter

ABSTRACT This research deals with design of three-phase hybrid active power filter to reduce the current distortions caused by non-linear loads. The Instantaneous Active and Reactive Power Method (p-q) is used to perform the identification of disturbing currents. The p-q algorithm generates the reference compensation current signal, while this generated reference compensation current signal is exactly followed by the output current of the voltage source converter. Fuzzy logic controller for three-phase hybrid active power filter is used to generate the switching signals in order to control the output currents of voltage source converter. Simulation results showed that the hybrid active power filter can compensate the harmonic currents effectively and improve power quality. Keywords Hybrid Active Filter, p-q theorem, Total Harmonic Distortion, Fuzzy Logic Controller. 1. INTRODUCTION Nowadays industries prefer to use power electronics based devices due to their effectiveness. Though these power electronics based devices are advantageous to the electronics and electrical industry, these devices generate and inject the harmonics in the power industry. These harmonic are known as electrical disturbance which is the main cause of the power quality associated harms. The industrial process is affected by the power quality problems. Therefore for improving the quality of the power supply this harmonic distortion should be decreased with the help of the filters. In the literature, various topologies of active power filters (APFs) have been presented for mitigation of harmonics [1-3]. The APF topologies are not cost-effective for the application of high power because of their high rating and very high switching frequency of pulse width modulator (PWM) converter. Thus LC passive filters (PFs) are used for harmonic filtration of such large nonlinear loads. Low cost and high reliability is the main advantage of PFs. However, PFs suffer from some shortcomings for example, the performance of these filters is affected due to the varying impedance of the system and with the utility system the series and parallel resonances may be created, which cause current harmonics increase in the supply [4-5]. As discussed above both APFs and PFs suffer from a number of disadvantages. Therefore another solution of harmonic mitigation, called hybrid active power filter (HAPF), has been introduced. Hybrid active power filters (HAPF) provide the combined advantages of APF and PPF and eliminate their disadvantages. These topologies are cost effective solutions of the high-power power quality problems with well filtering performance. This research paper is restricted to the (HAPF). The (HAPF) is specially designed to compensate the reactive power and decrease the harmonic currents occurred on the side of load from the grid, by injecting the current having same magnitude but opposite in the phase direction of the harmonic current [6]. In the literature a number of methods have been emphasized for identification of reference current [7-12]. For identification of disturbing current the instantaneous reactive power method has been used in this paper. For controlling the output currents of the converter, to follow the reference currents, hysteresis current controller have been used in [13-15].The implementation of hysteresis current controller is simple and its performance is also excellent. However, this controller suffers from drawbacks. Its main drawback is to generate the variable switching frequency. Therefore reliability and efficiency of hybrid active power filter is affected [16]. To avoid these drawbacks, this paper present the fuzzy logic based current controller to control the output currents of the voltage source converter. Although to control the output current of converter based on fuzzy based is not new [17-18], this approach with 15 rules has not yet being applied to proposed filter.