Die Professur Technische Informatik der TU Chemnitz erforscht neuartige, innovative Anwendungsgebiete auf Basis der RFID Technologie. Durch die Installation von RFID-Toren an gebäudespezifischen Schlüsselpositionen und die Verwendung handelsüblicher RFID-Tags gelingt nicht nur eine Objektidentifikation sondern auch eine kostengünstige Lokalisierung auf Basis spezieller Algorithmen. In Kombination mit berührungsempfindlichen Displays konnte ein intelligentes und interaktives Gebäudeleitsystem umgesetzt werden. Durch eine zentrale Managementeinheit ist es nun möglich, zielgerichtet einzelne Displays anzusteuern und somit Richtungsangaben für den gewählten Bestimmungsort zu visualisieren. Zusatzinformationen sowie personalisierte Hinweise stehen bei Bedarf ebenfalls zur Verfügung. Mit Hilfe der Displays kann mit dem System interagiert werden. Änderungen des Bestimmungsortes durch den Nutzer sind somit jederzeit möglich. Zusätzlichen Komfort genießen Nutzer mit einem PDA oder Smartphone. Mobile Endgeräte können auf Basis einer entsprechenden Software auch ohne dedizierte Lokalisierungs-Hardware in den gewünschten Gebäudeabschnitt geleitet werden.

Dissertation--Salzburg, 1999. / Bibliogr. p. 298-302.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains iv, 260 p. Vita. Includes abstract. Includes bibliographical references (p. 232-257).

Thesis (M.S. in Electrical Engineering and Computer Science)--Massachusetts Institute of Technology. / Includes bibliographical references (p. [127]-132). Also available online.

Mobile robots are gaining increased autonomy due to advances in sensor and computing technology. In their current form however, robots still lack algorithms for rapid perception of objects in a cluttered environment and can benefit from the assistance of a human operator. Further, fully autonomous systems will continue to be computationally expensive and costly for quite some time. Humans can visually assess objects and determine whether a certain path is traversable, but need not be involved in the low-level steering around any detected obstacles as is necessary in remote-controlled systems. If only used for rapid perception tasks, the operator could potentially assist several mobile robots performing various tasks such as exploration, surveillance, industrial work and search and rescue operations. There is a need to develop better human-robot interaction paradigms that would allow the human operator to effectively control and manage one or more mobile robots. This paper proposes a method of enhancing user effectiveness in controlling multiple mobile robots through real-time map manipulation. An interface is created that would allow a human operator to add virtual obstacles to the map that represents areas that the robot should avoid. A video camera is connected to the robot that would allow a human user to view the robot's environment. The combination of real-time map editing and live video streaming enables the robot to take advantage of human vision, which is still more effective at general object identification than current computer vision technology. Experimental results show that the robot is able to plan a faster path around an obstacle when the user marks the obstacle on the map, as opposed to allowing the robot to navigate on its own around an unmapped obstacle. Tests conducted on multiple users suggest that the accuracy in placing obstacles on the map decreases with increasing distance of the viewing apparatus from the obstacle. Despite this, the user can take advantage of landmarks found in the video and in the map in order to determine an obstacle's position on the map.

This thesis presents the research carried out to investigate and achieve highly reliable and accurate navigation system of guidance for visually impaired pedestrians. The main aim with this PhD project has been to identify the limits and insufficiencies in utilising Network Real-Time Kinematic Global Navigation Satellite Systems (NRTK GNSS) and its augmentation techniques within the frame of pedestrian applications in a variety of environments and circumstances. Moreover, the system can be used in many other applications, including unmanned vehicles, military applications, police, etc. NRTK GNSS positioning is considered to be a superior solution in comparison to the conventional standalone Global Positioning System (GPS) technique whose accuracy is highly affected by the distance dependent errors such as satellite orbital and atmospheric biases. Nevertheless, NRTK GNSS positioning is particularly constrained by wireless data link coverage, delays of correction and transmission and completeness, GPS and GLONASS signal availability, etc., which could downgrade the positioning quality of the NRTK results. This research is based on the dual frequency NRTK GNSS (GPS and GLONASS). Additionally, it is incorporated into several positioning and communication methods responsible for data correction while providing the position solutions, in which all identified contextual factors and application requirements are accounted. The positioning model operates through client-server based architecture consisted of a Navigation Service Centre (NSC) and a Mobile Navigation Unit (MNU). Hybrid functional approaches were consisting of several processing procedures allowing the positioning model to operate in position determination modes. NRTK GNSS and augmentation service is used if enough navigation information was available at the MNU using its local positioning device (GPS/GLONASS receiver).The positioning model at MNU was experimentally evaluated and centimetric accuracy was generally attained during both static and kinematic tests in various environments (urban, suburban and rural). This high accuracy was merely affected by some level of unavailability mainly caused by GPS and GLONASS signal blockage. Additionally, the influence of the number of satellites in view, dilution of precision (DOP) and age corrections (AoC) over the accuracy and stability of the NRTK GNSS solution was also investigated during this research and presented in the thesis. This positioning performance has outperformed the existing GPS service. In addition, utilising a simulation evaluation facility the positioning model at MNU performance was quantified with reference to a hybrid positioning service that will be offered by future Galileo Open Service (OS) along with GPS. However, a significant difference in terms of the service availability for the advantage of the hybrid system was experienced in all remaining scenarios and environments more especially the urban areas due to surrounding obstacles and conditions. As an outcome of this research a new and precise positioning model was proposed. The adaptive framework is understood as approaching an integration of the available positioning technology into the context of surrounding wireless communication for a maintainable performance. The positioning model has the capability of delivering indeed accurate, precise and consistent position solutions, and thus is fulfilling the requirements of visually impaired people navigation application, as identified in the adaptive framework.

A navigation system for precision lunar descent and landing is presented and analyzed. The navigation algorithm is based upon the extended Kalman Filter and employs measurements from an inertial measurement unit to propagate the vehicle position, velocity, and attitude forward in time. External measurements from an altimeter, star camera, terrain camera, and velocimeter are utilized in state estimate updates. The navigation algorithm also attempts to estimate the values of uncertain parameters associated with the sensors. The navigation algorithm also estimates the map-tie angle of the landing site which is a measure of the misalignment of the actual landing site location on the surface of the Moon versus the estimated position of the landing site. The navigation algorithm is subject to a sensitivity analysis which investigates the contribution of each error source to the total estimation performance of the navigation system. Per the results of the sensitivity analysis, it is found that certain error sources need not be actively estimated to achieve similar estimation performance at a reduced computational burden. A new, reduced-order system is presented and tested through covariance analysis and a monte carlo analysis. The new system is shown to have comparable estimation performance at a fraction of the computer run-time, making it more suitable for a real-time implementation. / text

Researchers have learned much about how sighted individuals seek information on Web sites - for example, users follow "information scent" as they move from page to page, and individual differences may impact successful information seeking on the Web. While it is possible that individuals with disabilities, especially those with severe visual impairments, perform information-seeking activities in a similar manner, little is known about how individuals who use screen readers to navigate actually seek information on the Web. In this study, we used both qualitative and quantitative measures to investigate the Web navigation techniques of four screen-reader users and how a user’s experience affects these navigation techniques and his or her ability to successfully complete an information-finding task. We compared metrics for between-page and within-page navigation to studies of sighted users. We also considered how a Web site’s compliance with Section 508 guidelines affects the overall information-finding experience of a visually-impaired individual. We discovered that among the four individuals in this study, user experience was not necessarily indicative of a successful information-finding experience. As individuals, the participants' navigation techniques varied widely; as a group, they generally searched more frequently and used the back button less frequently than has been reported for sighted individuals. Screen-reader users in this study followed a more flimsy, linear navigation style and generally used scrolling actions rather than searching actions. When using a Web site that has a Section 508 compliant home page, we found that the screen-reader users in this study completed information-finding tasks significantly more quickly, used significantly fewer actions, and reported a more satisfying information-finding experience. They were also more successful at finding the information goal and encountered fewer impasses. Using both quantitative and qualitative measures was critical in this study. The quantitative metrics allowed us to compare values and the qualitative data provided additional insight into individual differences as well as allowing a deeper understanding of the quantitative data. The information from this study contributes to the growing body of research knowledge about screen-reader users. It also contributes a new understanding of screen-reader users that can be used by the worldwide community of Web developers, designers, and users. / text

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Real-time navigation during the final approach phase of an interplanetary mission can significantly increase the accuracy of aerocapture and pin-point landing. The Mars Network is a versatile telecommunications network that is ideally situated to provide spacecraft-to-spacecraft radiometric navigation during Mars final approach and entry, descent, and landing via the Electra UHF transceiver, which is capable of providing autonomous, on-orbit, real-time trajectory determination using two-way Doppler measurements between a Mars approach vehicle and a Mars Network orbiter. A detailed dynamic analysis and link analysis of the final approach problem is presented, which seeks to determine the expected operating conditions of the Electra transceiver. In particular, the maximum Doppler shift and Doppler rate, which determine the transceiver tracking loop requirements, and the total received signal power and signal-to-noise ratio, which determine the range at which the communications link can be closed, are investigated for a range of Mars Network orbital geometries. A model of the Electra signal is developed on the basis of the results of the dynamic analysis and link analysis and is used as input to a high-fidelity simulation of the Electra transceiver. A Monte Carlo analysis is performed to determine the performance of the Electra transceiver for a range of signal and tracking loop parameters. In particular, the performance analysis focuses on the maximum range at which the link can be closed and on the acquisition and tracking performance of the second-order tracking loop. The analysis of the tracking performance is used to characterize and model the error in the Doppler measurement of the Electra transceiver. The error model is incorporated into the design of an extended Kalman filter, in order to improve the fidelity of the navigation filter design. The information content in the Doppler measurement and the observability of the estimated states are investigated for various orbital geometries and the accuracy of the navigation solution is analyzed.