Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Numerical Investigations of Resistive Wall Wake Potentials(Institution of Engineering and Technology, 2020) Yaman, FatihThe aim of this Letter is to examine and identify longitudinal resistive wall wake potential behaviours of medium-beta long bunches and ultra-relativistic short bunches using different beam and pipe properties for particle accelerator applications. The lack of detailed analysis in current literature for the chosen set of parameters ignites this work. Since computations of wake potentials for the considered beam parameters by particle-in-cell codes are extremely difficult the author uses an analytical approach. Numerical integrations are evaluated for large domains with fine discretisations. The author observes that conductivity of beam pipe has a larger impact on medium-beta long bunches, variation of beam velocity effects wakes of short bunches more significantly, beam radii changes may have a contribution to instability for low energy short bunches. Interesting numerical results are presented and their physical explanations are discussed in this Letter.Article Citation - WoS: 1Citation - Scopus: 1Spatial Signature for Secure Miso-Ofdm Systems(Institution of Engineering and Technology, 2018) Özbek, Berna; Karabulut Kurt, GüneşPhysical layer security is a promising approach to establish secure communications based on the characteristics of wireless channels. A spatial signature based secure multiple-input single-output (MISO) orthogonal frequency division multiplexing (OFDM) system is proposed to disrupt the reception of a passive eavesdropper by holding two practically relevant assumptions: a limited feedback link for legitimate node and the unavailability of channel state information of eavesdropper. The proposed algorithm achieves a higher average secrecy rate than the conventional secure MISO-OFDM systems in presence of a limited feedback link.Article Reduced Feedback Link Design for Devicerelaying Enhanced Multiple-Input Singleoutput Orthogonal Frequency-Division Multiple Access Wireless Systems(Institution of Engineering and Technology, 2016) Özbek, BernaDevice-relaying enhanced multiple-input single-output (MISO) orthogonal frequency-division multiple access (OFDMA) systems are one of the promising and cost-effective methods to satisfy data rate requirements of future wireless networks. To implement device relaying in MISO-OFDMA systems efficiently, the channel state information belonging to all links is required at the base station. However, the feedback load increases with the number of users, device-relay candidates, antennas and subcarriers. A novel scheduling and a joint feedback link design and relay selection algorithm in device-relaying enhanced downlink MISO-OFDMA systems are proposed, while reducing the feedback load significantly without sacrificing the system performance.Article Citation - WoS: 5Citation - Scopus: 5Robust Output Tracking Control of an Unmanned Aerial Vehicle Subject To Additive State Dependent Disturbance(Institution of Engineering and Technology, 2016) Tanyer, İlker; Tatlıcıoglu, Enver; Zergeroglu, Erkan; Deniz, Meryem; Bayrak, Alper; Özdemirel, BarbarosIn this study, an asymptotic tracking controller is developed for an aircraft model subject to additive, state-dependent, non-linear disturbance-like terms. Dynamic inversion technique in conjunction with robust integral of the sign of the error term is utilised in the controller design. Compared to the previous studies, the need of acceleration measurements of the aircraft have been removed. In addition, the proposed controller design utilises only the output of aircraft dynamics. Lyapunov based analysis is applied to prove global asymptotic convergence of the tracking error signal. Numerical simulation results are presented to illustrate the performance of the proposed robust controller.Article Citation - WoS: 2Citation - Scopus: 2Enhancing Stereo Matching Performance by Colour Normalisation and Specularity Removal(Institution of Engineering and Technology, 2011) Ozan, Şükrü; Gümüştekin, ŞevketA method to enhance the performance of stereo matching is presented. The position of the specular light reflection on an object surface varies due to the change in the position of the camera, light source, object or all combined. Additionally, there may be situations exhibiting a colour shift owing to a change in the light source chromaticity or camera white balance settings. These variations cause misleading results when stereo matching algorithms are applied. In this reported work, a single-image-based statistical method is used to normalise source images. This process effectively eliminates non-saturated specularities regardless of their positions on the object. The effect of specularity removal is tested on stereo image pairs. © 2011 The Institution of Engineering and Technology.Article Citation - WoS: 14Citation - Scopus: 16Charge Feedback-Based Robust Position Tracking Control for Piezoelectric Actuators(Institution of Engineering and Technology, 2012) Salah, M. H.; McIntyre, M. L.; Dawson, Darren M.; Wagner, John R.; Tatlıcıoğlu, Envern this study, the Coleman-hysteresis model is utilised in the piezoelectric actuator (PZTA) dynamic model and a non-linear robust control strategy is then developed to actively control the displacement of the PZTA effective tip. The proposed control technique is designed based on the partial knowledge of the hysteresis model while the mass of the PZTA is assumed to be uncertain. The piezoelectric charge measurement is utilised in the controller design to reduce the effects of the hysteresis. Lyapunov-based stability analysis techniques are utilised to ensure that a desired displacement trajectory is accurately tracked. Representative numerical results are presented and discussed to demonstrate the tracking performance of several desired displacement trajectories with different frequencies and amplitudes. Finally, comparisons with a standard PID controller and a sliding mode controller were performed to examine the effectiveness of the proposed control design. © 2012 The Institution of Engineering and Technology.Article Citation - WoS: 36Citation - Scopus: 38Optimum Seeking-Based Non-Linear Controller To Maximise Energy Capture in a Variable Speed Wind Turbine(Institution of Engineering and Technology, 2012) Iyasere, Erhun; Salah, Mohammed; Dawson, Darren M.; Wagner, John R.; Tatlıcıoğlu, EnverIn this study, an optimum seeking-based robust non-linear controller is proposed to maximise wind energy captured by variable speed wind turbines at low-to-medium wind speeds. The proposed strategy simultaneously controls the blade pitch angle and tip-speed ratio, through the turbine rotor angular speed, to an optimal point at which the power coefficient, and hence the wind turbine efficiency, is maximum. The optimal points are given to the controller by an optimisation algorithm that seeks the unknown optimal blade pitch angle and rotor speed. The control method allows for aerodynamic rotor power maximisation without exact knowledge of the wind turbine model. A representative numerical simulation is presented to show that the wind turbine can be accurately controlled to achieve maximum energy capture. © 2012 The Institution of Engineering and Technology.Article Citation - WoS: 33Citation - Scopus: 38Stable non-Gaussian noise parameter modulation in digital communication(Institution of Engineering and Technology, 2009) Çek, Mehmet Emre; Savacı, Ferit AcarThe parameter of the stable non-Gaussian noise sequence is modulated by the binary message sequence to achieve a secure communication system. The characteristic exponent 'alpha' of a stable non-Gaussian noise sequence carries the binary information. The receiver of the proposed random communication system demodulates the received signal by estimating the parameters of the transmitted noise sequence to recover the binary message sequence.Article Citation - WoS: 2Citation - Scopus: 3Low Complexity Zf Receiver for Orthogonal Sfbc-Ofdm in Broadband Wireless Channels(Institution of Engineering and Technology, 2006) Özbek, Berna; Le Ruyet, DidierOrthogonal space-frequency block coded (SFBC) orthogonal frequency division multiplexing (OFDM) systems are analysed in broadband wireless channels where adjacent subcarriers do not have the same channel coefficients and the matched filter receiver causes an error floor in bit error rate performance. To avoid this, a low complexity zero forcing (ZF) receiver for the orthogonal schemes with two and three transmit and one receive antennas are proposed.