Browsing by Author "Kerestecioğlu, Feza"

Now showing 1 - 14 of 14

Citation - Scopus: 2
Active Reconfigurable Control of a Submarine With Indirect Adaptive Control
(2003) Demirci, Ufuk; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
An indirect adaptive controller is designed for submersibles. The design is developed using a linearized MIMO model of a submarine. Standard recursive least squares estimation method is used to estimate the parameters. Depth and pitch angle of the submarine is controlled by means of the well-known indirect self-tuning method. In case of a system fault estimated parameters of the submarine model have been used to update the controller coefficients.
Citation - Scopus: 1
Connected Navigation of Non-Communicating Mobile Agents
(IEEE, 2012) Kerestecioğlu, Feza; Cezayirli, Ahmet; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
This article discusses the connectivity of autonomous mobile robots that do not have communication capabilities. We show that if the group members follow the proposed Local Steering Strategy which utilizes information only about the relative positions of neighbor robots they can sustain their connectivity even in the case of bounded position measurement errors and the occultation of robots by other robots in the group. To reduce the computational burden in the implementation of the proposed methodology we used sub-optimal solutions. © 2012 IEEE.
Citation - Scopus: 7
Fault Tolerant Control With Re-Configuring Sliding-Mode Schemes
(2005) Demirci, Ufuk; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this paper a controller design method for linear MIMO systems is presented which a sliding mode controller is reconfigured in case of system faults. Faults are detected with the residual vector generated from a standard linear observer. Once a fault has been detected the fault distribution matrix can be obtained and used to update the corrective or equivalent control parts of the sliding mode controller. As a result fault tolerant adaptive controllers keep the system performance within acceptable limits or at least avoids the system to wind-up. © TÜBITAK.
Citation - Scopus: 6
Indoor Positioning Using Federated Kalman Filter
(Institute of Electrical and Electronics Engineers Inc., 2018) Ayabakan, Tarık; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this paper, the performance of a multi-sensor fusion technique, namely Federated Kalman Filter (FKF) is studied in the context of indoor positioning problem. Kalman filters having centralized and decentralized structures are widely used in outdoor positioning and navigation applications. Global Positioning System (GPS) is the most commonly used system for outdoor positionin/navigation, which cannot be used indoors due to the signal loss. In this study, a decentralized structure for FKF is applied in indoor positioning problem by taking its outdoor navigation performance into consideration. Simulations are performed with distance measurements, which are assumed to be calculated by using Received Signal Strength (RSS). Results gathered via different simulations are evaluated as promising for future studies.
Citation - WoS: 5
Citation - Scopus: 6
Multi-Sensor Indoor Positioning
(Institute of Electrical and Electronics Engineers Inc., 2019) Ayabakan, Tarık; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this paper, the performance of three different kinds of Kalman Filter (KF) structure: Single Kalman Filter (SKF)(which filters data of a single sensor), Centralized Kalman Filter (CKF) and Federated Kalman Filter (FKF) are studied considering the indoor positioning problem. Kalman filters are widely used in outdoor positioning and navigation applications providing good results. For multi-sensor applications, KF has centralized and decentralized structures. In this study, multisensor and single-sensor dedicated Kalman filter structures FKF, CKF and SKF are applied in indoor positioning problem by taking its outdoor navigation performance into consideration. Received Signal Strength (RSS) data are generated, from which distance information, a vital part of the simulations, are obtained. Three different noise levels are used to assess performance of filters. Results gathered via different simulations showed that multi-sensor structures provide a better solution than single sensor structures.
Citation - WoS: 2
Citation - Scopus: 8
Navigation of Autonomous Mobile Robots in Connected Groups
(IEEE, 2008) Cezayirli, Ahmet; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
The navigation of autonomous mobile robots as a group is considered in this paper. Definitions adopted from the graph theory are given to characterize the robot group. A local steering strategy is proposed such that when each robot in the group applies this steering scheme the overall result is that the whole group is displaced without losing its connectivity. This is achieved using only limited-range position sensors and without any communication between the robots.
Citation - WoS: 9
Citation - Scopus: 9
Navigation of Non-Communicating Autonomous Mobile Robots With Guaranteed Connectivity
(Cambridge Univ Press, 2013) Cezayirli, Ahmet; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
We consider the connectivity of autonomous mobile robots. The robots navigate using simple local steering rules without requiring explicit communication among themselves. We show that using only position information of neighbors the group connectivity can be sustained even in the case of bounded position measurement errors and the occlusion of robots by other robots in the group. In implementing the proposed scheme sub-optimal solutions are invoked to avoid an excessive computational burden. We also discuss the possibility of deadlock which may bring the group to a standstill and show that the proposed methodology avoids such a scenario in real-life settings.
Citation - Scopus: 1
A Non-Communicating Multi-Robot System With Switchable Formations
(2013) Cezayirli, Ahmet; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
We consider connected navigation of autonomous mobile robots with transitions in the group formation. The robots navigate using simple local steering rules without requiring explicit communication among themselves. The formations are achieved by designing proper cost functions and formation transitions are succeeded by switching among these cost functions. The resulting system is proven to be deadlock-free under certain conditions. © 2013 IEEE.
Citation - WoS: 2
Nonuniform Sampling for Detection of Abrupt Changes
(Birkhauser Boston Inc, 2003) Kerestecioğlu, Feza; Tokat, Sezai; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this work detection of abrupt changes in continuous-time linear stochastic systems and selection of the sampling interval to improve the detection performance are considered. Cost functions are proposed to optimize both uniform and nonuniform sampling intervals for the well-known cumulative sum algorithm. Some iterative techniques are presented to make online optimization computationally feasible. It is shown that considerable improvement in the detection performance can be obtained by using nonuniform sampling intervals.
Citation - WoS: 1
Citation - Scopus: 6
On Preserving Connectivity of Autonomous Mobile Robots
(IEEE, 2009) Cezayirli, Ahmet; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
The connectivity of the autonomous mobile robots is considered in this paper. The group navigation is provided using simple local steering rules and without any explicit communication. Sub-optimal solutions are invoked to avoid computational cost. We show that the connectivity of the group is preserved during the whole motion in spite of bounded measurement errors on angles and distances. Some special cases of group topology are also discussed.
Citation - WoS: 12
Citation - Scopus: 14
Optimal Input Design for the Detection of Changes Towards Unknown Hypotheses
(Taylor & Francis Ltd, 2004) Kerestecioğlu, Feza; Cetin, I; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
The effects of auxiliary input signals on detecting changes in ARMAX processes via statistical tests are discussed. Two extensions to the Cumulative Sum Test are considered. The first is applicable when the direction of the change in the parameter space is known but its magnitude is unknown. The second is applicable when neither is known. The performance criteria for the design of stationary stochastic inputs are based on the asymptotic properties of the tests. It is shown that power-constrained optimal inputs have discrete spectra and a suitably chosen input can greatly improve the detection performance.
Citation - WoS: 15
Citation - Scopus: 17
A Re-Configuring Sliding-Mode Controller With a Ustable Robustness
(Pergamon-Elsevier Science Ltd, 2004) Demirci, Ufuk; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this paper a controller design method for underwater vehicles is presented which is based on re-configuration of a sliding-mode controller in case of disturbances caused by shallow water conditions. The disturbance distribution information can be obtained and used to update the corrective gain vector of the sliding-mode controller. This increases the robustness of the controller and hence keeps the system performance within acceptable limits. Proposed method is validated with simulations on a submarine model. (C) 2003 Published by Elsevier Ltd.
Sliding Mode Controller Solution for the Shallow Submerged Operation Ok a Submarine
(IFAC Secretariat, 2003) Demirci, Ufuk; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
In this paper a submarine controller is presented which can accommodate the sea wave effects on a submarine a(shallow water operation. Sliding mode method is implemented in a way that the robustness of the controller increased with respect to disturbance distribution vector in order to perform the depth control of a shallow submerged submarine under sea wave disturbances. Designed controller kept the submarine performance within acceptable limits. Copyright © 2003 IFAC.
Citation - Scopus: 5
Zero-Crossing Based Demodulation of Minimum Shift Keying
(2003) Kalkan, Mine; Kerestecioğlu, Feza; Computer Engineering; 05. Faculty of Engineering and Natural Sciences; 01. Kadir Has University
Minimum shift keying (MSK) modulation has features such as constant envelope compact spectrum and good error performance which are all desirable in many digital applications including mobile radio. Numerous receiver structures to demodulate MSK have been suggested such as correlation receivers differential detectors and frequency discriminators MSK is a form of biphase keying and can be detected by a zero-crossing based phase demodulator which gives near optimum performance. In this paper the bit error performance of a zero-crossing based coherent MSK demodulator is theoretically investigated and a closed-form expression for the bit error rate is derived. The results indicate that the demodulator performs within 0.8-1 dB of the theoratical optimum for MSK. Towards the goal of deriving probability of bit error it is also shown that under additive white Gaussian noise (AWGN) zero-crossing locations of MSK signals are Gaussian distributed except at very low signal-to-noise ratios.