Browsing by Subject "Positioning system"
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Item Open Access Autonomous navigation of robotic units in mobile sensor network(2012) Nazlibilek, S.This work is motivated by the problem of detecting buried anti-tank and anti-personnel mines in roads or some border regions. The problem is tried to be solved by use of small mobile robotic sensors and their some abilities such as measurement of local fields, navigation around a region, communications with each other, and constituting team within a mission area. The aim of this work is to investigate the navigation problem for the team behavior of mobile sensors within a potential field available in a small-scale environment such as an indoor area or an outdoor region. The mobile sensor network here is a collection of robotic units with sensing capability of earth magnetic field anomalies. A new kind of positioning system is needed for their collective behavior. In this work, a new method of navigation is proposed as a local positioning system. It utilizes ultrasound and radio frequency information to determine the coordinates of the points inside the operational area. The method proposed here is compared with the ultra wideband ranging ping-pong method that is used widely in recent applications. A time division multiple access method is used for the communications among the mobile sensors. The results on the positioning methods together with several simulations and experimental works are given. It is shown that the positioning method utilizing ultrasound-radio frequency method can give fairly good results. © 2012 Elsevier Ltd. All rights reserved.Item Open Access Enhanced position estimation via node cooperation(IEEE, 2010) Sahinoglu, Z.; Gezici, SinanTwo-way time-of-arrival (TW-ToA) is a widely used ranging protocol that can provide the distance between two devices without time synchronization. One drawback of the TW-ToA is poor positioning accuracy in the absence of a sufficient number of reference ranging devices. Also, for a self-positioning system with a limited battery life, it might be necessary to limit the number of transmissions while satisfying accuracy constraints. In this paper, a cooperative positioning protocol [1] is studied, which can improve positioning accuracy compared to the conventional TW-ToA based positioning systems and also facilitate positioning with fewer packet transmissions; hence, it can prolong battery life on average. The maximum likelihood estimator is obtained for the cooperative technique and the limits on the positioning accuracy are quantified in terms of the Cramer-Rao lower bound (CRLB). Simulation results are provided in order to show performance improvements. ©2010 IEEE.Item Open Access Learning based cross-coupled control for multi-axis high precision positioning systems(ASME, 2012-10) Geçer-Ulu, Nurcan; Ulu, Erva; Çakmakçı, MelihIn this paper, a controller featuring cross-coupled control and iterative learning control schemes is designed and implemented on a modular two-axis positioning system in order to improve both contour and tracking accuracy. Instead of using the standard contour estimation technique proposed with the variable gain cross-coupled control, a computationally efficient contour estimation technique is incorporated with the presented control design. Moreover, implemented contour estimation technique makes the presented control scheme more suitable for arbitrary nonlinear contours. Effectiveness of the control design is verified with simulations and experiments on a two-axis positioning system. Also, simulations demonstrating the performance of the control method on a three-axis positioning system are provided. The resulting controller is shown to achieve nanometer level contouring and tracking performance. Simulation results also show its applicability to three-axis nano-positioning systems. Copyright © 2012 by ASME.Item Open Access Modeling and cross coupling controller development for a 6DOF laser micro-machining system(IEEE, 2017) Kerimoğlu, Serhat; Çakmakçı, MelihIn recent years, studies on manufacturing systems have proved the importance of cooperation of positioning systems with laser cutting technology. The performance of the manufacturing system can be improved by utilizing both laser and positioning systems together. In this study, modeling and cross coupling controller development of a micromachining system which can perform on non-linear contoured surfaces is presented. Laser micromachining system is designed and assembled including a nanosecond Q-switched pulsed fiber laser, a 6-DOF hexapod manipulator, a granite table in order to absorb vibrations and an external cabin system to isolate the whole system for safety and health issues. The positioning system used here has fast response and precise positioning capabilities with a wide range of workspace. However, its performance of machining non-linear surfaces can be further improved by using a cross coupled control algorithm. On top of the loop based controllers an add-on controller is developed to improve the contouring performance by including the effects of the other feedback loops on the overall controller. Actual laser cutting results also show improvements due to the improvements in the positioning system performance.