Semi-autonomous Navigation of a Robotic Wheelchair

The present work considers the development of a wheelchair for people with special needs, which is capable of navigating semi-autonomously within its workspace. This system is expected to prove useful to people with impaired mobility and limited fine motor control of the upper extremities. Among the implemented behaviors of this robotic system are the avoidance of obstacles, the motion in the middle of the free space and the following of a moving target specified by the user (e.g., a person walking in front of the wheelchair). The wheelchair is equipped with sonars, which are used for distance measurement in preselected critical directions, and with a panoramic camera with a 360 degree field of view, which is used for following a moving target. After suitably processing the color sequence of the panoramic images using the color histogram of the desired target, the orientation of the target with respect to the wheelchair is determined, while its distance is determined by the sonars. The motion control laws developed for the system use the sensory data and take into account the non-holonomic kinematic constraints of the wheelchair, in order to guarantee certain desired features of the closed-loop system, such as stability. Moreover, they are as simplified as possible to minimize implementation requirements. An experimental prototype has been developed at ICS–FORTH, based on a commercially-available wheelchair. The sensors, the computing power and the electronics needed for the implementation of the navigation behaviors and of the user interfaces (touch screen, voice commands) were developed as add-on modules and integrated with the wheelchair.     

Fusion of laser and visual data for robot motion planning and collision avoidance

In this paper, a method for inferring scene structure information based on both laser and visual data is proposed. Common laser scanners employed in contemporary robotic systems provide accurate range measurements, but only in 2D slices of the environment. On the other hand, vision is capable of providing dense 3D information of the environment. The proposed fusion scheme combines the accuracy of laser sensors with the broad visual fields of cameras toward extracting accurate scene structure information. Data fusion is achieved by validating 3D structure assumptions formed according to 2D range scans of the environment, through the exploitation of visual information. The proposed methodology is applied to robot motion planning and collision avoidance tasks by using a suitably modified version of the vector field histogram algorithm. Experimental results confirm the effectiveness of the proposed methodology.Received: 10 May 2002, Accepted: 18 December 2002, Published online: 7 October 2003     

Tele-Presence in Populated Exhibitions Through Web-Operated Mobile Robots

This paper presents techniques that facilitate mobile robots to be deployed as interactive agents in populated environments such as museum exhibitions or trade shows. The mobile robots can be tele-operated over the Internet and, this way, provide remote access to distant users. Throughout this paper we describe several key techniques that have been developed in this context. To support safe and reliable robot navigation, techniques for environment mapping, robot localization, obstacle detection and people-tracking have been developed. To support the interaction of both web and on-site visitors with the robot and its environment, appropriate software and hardware interfaces have been employed. By using advanced navigation capabilities and appropriate authoring tools, the time required for installing a robotic tour-guide in a museum or a trade fair has been drastically reduced. The developed robotic systems have been thoroughly tested and validated in the real-world conditions offered in the premises of various sites. Such demonstrations ascertain the functionality of the employed techniques, establish the reliability of the complete systems, and provide useful evidence regarding the acceptance of tele-operated robotic tour-guides by the broader public.     

A novel spectral microscope system: application in quantitative pathology

In this paper, a novel spectral microscope system is presented together with a method for the quantitative assessment of the uptake by histologic samples of stains used in pathology to label tissue features of diagnostic importance. The critical component of the microscope is a variable interference filter-based monochromator. The system is capable of performing real-time spectral imaging in a plurality of spectral bands and micro-spectroscopy in any image pixel, in the spectral range 400-1000 nm. The wavelength-tuning step is 2.4-2.6 nm, while the full-width at half maximum in each step is about 1.5% of the operating central wavelength. The developed system integrates algorithms and calibration procedures for the calculation of the stain-uptake by the tissue. The acquired spectra from both stained tissue and calibration stain solutions enable the calculation of the concentration maps of the stains, even if the latter are multiple and overlap spatially and spectrally. The system was used for the quantitative mapping of the expression of estrogen and progesterone receptors in breast cancer cells. In this particular case, model validation shows that although two stains are employed, capturing of their transmittance at more than ten wavelengths is required in order to obtain an acceptable accuracy. These findings highlight the need for the development and implementation of spectral microscopy in pathology and its potential to introduce novel more reliable diagnostic criteria.     

Vehicle Velocity Estimation Based on RSS Measurements

This paper presents a technique which is based on pattern recognition techniques, in order to estimate Mobile Terminal (MT) velocity. The proposed technique applies on received signal strength (RSS) measurements and more precisely on information extracted from Iub air interface, in wIDeband code-division multiple access (WCDMA) systems for transmission control purposes. Pattern recognition is performed by HIDden Markov Model (HMM), which is trained with downlink signal strength measurements for specific areas, employing Clustering LARge Applications (CLARA) like a clustering method. Accurate results from a single probe vehicle show the potential of the method, when applied to large scale of MTs. Theodore S. Stamoulakatos is a Senior Research Associate with the Department of Electrical and Computer Engineering at National Technical University of Athens (NTUA). He received his B.Sc. in Mathematics from University of the Aegean, Greece, in 1997, and the M.Sc. in Computer Applications from Dublin City University, Ireland, in 1999 with scholarship from the Irish Ministry of Education. On April ’05 he received his Ph.D. degree from the Department of Electrical Engineering and Computer Science of the National Technical University of Athens. He has been lecturing in DCU various courses including Algorithms & Data Structures, Computer Systems, and Advanced Network Management to both undergraduate and postgraduate students. During his research in NTUA, he has been actively involved in many European and National projects that match his research interests. Both his academic as well as his industrial experience (four years in OTEnet S.A.) allow him to publish several papers in journals and international conferences, which are in the fields of Mobile and Personal Communication Networks, Active Networks, Location Based Services as well as Network and Service Management. Dr. Stamoulakatos is a member of the IEEE. Antonis E. Markopoulos obtained his degree in Informatics and Telecommunications Engineering from University of Athens, Greece in 2000. During his studies he participated in various research projects dealing with the management of fixed and wireless networks. He has also industrial experience for 2 years in INTRASOFT International S.A participating in several projects, national and European. He received his PhD in the field of Cellular and Wireless Communication from the National Technical University of Athens in 2005, where he is working as a Senior Research Engineer in the Telecommunication Laboratory. He has published several papers in journals, international conferences and book chapters. His research interests are in the fields of cellular and wireless networks of present and future generation (4G, WLAN/WPAN, WiMAX) and more specific in the areas of radio resource management and security. He has been mainly involved in many European (IST-CELLO, IST-PACWOMAN, IST-MAGNET, a.o) and National (Greek IST, GGRT) projects. Dr Markopoulos is a member of the IEEE and of the Greek Association of Mechanical and Electrical Engineers. Miltiades E. Anagnostou was born in Athens, Greece, in 1958. He received the Electrical Engineer’s Diploma from the National Technical University of Athens (NTUA) in 1981. In 1987 he received his PhD in the area of computer networks. Since 1989 he has been teaching at the Electrical and Computer Engineering School of NTUA, where he is currently a Full Professor. He teaches courses on modern telecommunications, computer networks, formal specification, stochastic processes, and network algorithms. His research spans several fields, including broadband networks, mobile and personal communications, service engineering, mobile agents, pervasive computing, network algorithms and queuing systems. He is a member of the IEEE and the ACM. Michael E. Theologou received the degree in Electrical Engineering from Patras University and his Ph.D. degree from the Department of Electrical Engineering and Computer Science of the National Technical University of Athens. Currently he is a Professor at National Technical University of Athens, Department of Electrical and Computer Engineering conducting teaching and research in the wider area of Telecommunication Networks and Systems. His research interests are in the fields of Mobile and Personal Communication Networks, Computer Networks, Quality of Service. He has many publications in the above areas.     

Oscillatory band gap behavior in small diameter Si-clathrate nanowires

Electronic structure analysis of small cagelike silicon nanowires is carried out and reveals many surprising features. The band gap values for all the nanowires are found to be smaller than their bulk counterparts. The most intriguing aspect appears to be the alternating sequence of direct and indirect band gaps as the diameter changes. This is attributed to the type of surface geometry. We illustrate this with two well-known clathrate forms as well as a new hexagonal clathrate structure with a direct band gap in the optical region.     

Road safety performance indicators for the interurban road network

Various road safety performance indicators (SPIs) have been proposed for different road safety research areas, mainly as regards driver behaviour (e.g. seat belt use, alcohol, drugs, etc.) and vehicles (e.g. passive safety); however, no SPIs for the road network and design have been developed. The objective of this research is the development of an SPI for the road network, to be used as a benchmark for cross-region comparisons. The developed SPI essentially makes a comparison of the existing road network to the theoretically required one, defined as one which meets some minimum requirements with respect to road safety. This paper presents a theoretical concept for the determination of this SPI as well as a translation of this theory into a practical method. Also, the method is applied in a number of pilot countries namely the Netherlands, Portugal, Greece and Israel. The results show that the SPI could be efficiently calculated in all countries, despite some differences in the data sources. In general, the calculated overall SPI scores were realistic and ranged from 81 to 94%, with the exception of Greece where the SPI was relatively lower (67%). However, the SPI should be considered as a first attempt to determine the safety level of the road network. The proposed method has some limitations and could be further improved. The paper presents directions for further research to further develop the SPI.     

“To be able to change,you have to take risks #fitspo”: Exploring correlates of fitspirational social media use among young women

Posting and viewing fitspiration-related content is a new social media trend. Although some say that fitspiration inspires women towards an empowered body image, others argue that fitspirational social media use may negatively influence women’s body image. To address these concerns, the current study (359 women; ages 18–28?years) investigated how exposure to four types of fitspirational social media messages related to three indicators of body image: body dissatisfaction, compulsive exercise, and situated optimism related to body goals. Moreover, we investigated the role of two individual difference variables in predicting women’s exposure to fitspirational messages and moderating the relationships between exposure and indicators of body image: thin-ideal internalization and fit-ideal internalization. Overall, the study provides support for both positive and negative correlates of fitspirational social media use. In addition, the findings provide initial evidence that individual difference variables differentially predict exposure to certain types of fitspirational content and moderate the relationship between fitspirational social media and body image related variables. Thus, this study emphasizes that the relationship between fitspirational social media and body image involves a complex interaction between characteristics of consumers and the exact content that is being consumed.