Juan C. García

Integral system for assisted mobility

Abstract This paper presents the results of a research work carried out in the Electronics Department of the University of Alcala in the field of electronic systems for the guidance of wheelchairs for the disabled and/or the elderly. These electronic systems have been designed to meet a wide range of needs experienced by users of this type of wheelchair. One of their most important features is their modularity, thereby making them adaptable to the particular needs of each user according to the type and degree of handicap involved. The overall system includes a complete user–machine interface, motor control modules and safety and autonomous guidance systems. The project is called: “Sistema Integral de Ayuda a la Movilidad (SIAMO)” (integral system for assisted mobility).

Wheelchair for physically disabled people with voice, ultrasonic and infrared sensor control

This paper describes a wheelchair for physically disabled people developed within the UMIDAM Project. A dependent-user recognition voice system and ultrasonic and infrared sensor systems has been integrated in this wheelchair. In this way we have obtained a wheelchair which can be driven with using voice commands and with the possibility of avoiding obstacles and downstairs or hole detection. The wheelchair has also been developed to allow autonomous driving (for example, following walls). The project, in which two prototypes have been produced, has been carried out totally in the Electronics Department of the University of Alcalá (Spain). It has been financed by the ONCE. Electronic system configuration, a sensor system, a mechanical model, control (low level control, control by voice commands), voice recognition and autonomous control are considered. The results of the experiments carried out on the two prototypes are also given.

Electronic control of a wheelchair guided by voice commands

Abstract This paper describes the control of an electric wheel chair with voice commands. This chair has been developed and built at the U.A.H. Electronic Department and financed by the ONCE Foundation (Spain). The first prototype consists of voice recognition, motor control, user interface and central processor modules. The electronic system allows the chair user a safe, easy ride, and guarantees the concordance between user commands and actual trajectories. Furthermore, the system has been designed to allow the addition of future features, like obstacle and stair detection and the tele-commanding of electrical household appliances from the chair.

Trends in the prevalence and distribution of HTLV-1 and HTLV-2 infections in Spain

BackgroundAlthough most HTLV infections in Spain have been found in native intravenous drug users carrying HTLV-2, the large immigration flows from Latin America and Sub-Saharan Africa in recent years may have changed the prevalence and distribution of HTLV-1 and HTLV-2 infections, and hypothetically open the opportunity for introducing HTLV-3 or HTLV-4 in Spain. To assess the current seroprevalence of HTLV infection in Spain a national multicenter, cross-sectional, study was conducted in June 2009.ResultsA total of 6,460 consecutive outpatients attending 16 hospitals were examined. Overall, 12% were immigrants, and their main origin was Latin America (4.9%), Africa (3.6%) and other European countries (2.8%). Nine individuals were seroreactive for HTLV antibodies (overall prevalence, 0.14%). Evidence of HTLV-1 infection was confirmed by Western blot in 4 subjects (prevalence 0.06%) while HTLV-2 infection was found in 5 (prevalence 0.08%). Infection with HTLV types 1, 2, 3 and 4 was discarded by Western blot and specific PCR assays in another two specimens initially reactive in the enzyme immunoassay. All but one HTLV-1 cases were Latin-Americans while all persons with HTLV-2 infection were native Spaniards.ConclusionsThe overall prevalence of HTLV infections in Spain remains low, with no evidence of HTLV-3 or HTLV-4 infections so far.

Extensive Ultrasonic Local Positioning System for navigating with mobile robots

This paper presents an extensive local ultrasonic positioning system for mobile robots (MRs) based on the fusion of the information from the MR internal odometer sensor and the measurements of position obtained with a set of external ultrasonic beacons that form an Ultrasonic Local Positioning System (ULPS). The extensive ULPS is formed using several single ULPS, each one of them covering a particular area of the total working area. In each single ULPS, five ultrasonic beacons are used that emit simultaneously and are detected by an ultrasonic receiver on board the MR. Direct Sequence Code Division Multiple Access (DS-CDMA) techniques have been used to avoid interferences between them. When the MR navigates on the working area, it continuously obtains its relative position thanks to the internal odometer. The cumulative errors of the odometer are corrected when the robot is on a place where the positioning data obtained with any of the single ULPS are available. The fusion of information (from odometer and ULPS) is made using an H-Infinite filter. The extensive ULPS has been built and tested experimentally.

Guidance of a wheelchair for handicapped people by face tracking

This paper shows a guidance system for an electrical wheelchair for handicapped people by head movements. A color face tracking system has been developed in order to compute head movements of the user and, depending on them, some commands are generated to drive the wheelchair. The system is non-intrusive and it allows visibility and freedom of head movements. It is able to learn the face features of the user in an automatic initial setup, working even for people of different races. It is adaptive and, therefore, robust to light and background changes in inside environments. It has been tested with several users and some results are given.

Improvements of a Brain-Computer Interface Applied to a Robotic Wheelchair

Two distinct signal features suitable to be used as input to a Support-Vector Machine (SVM) classifier in an application involving hands motor imagery and the correspondent EEG signal are evaluated in this paper. Such features are the Power Spectral Density (PSD) components and the Adaptive Autoregressive (AAR) parameters. The best result (an accuracy of 97.1%) is obtained when using PSD components, while the AAR parameters generated an accuracy of 91.4%. The results also demonstrate that it is possible to use only two EEG channels (bipolar configuration around C 3 and C 4), discarding the bipolar configuration around C z . The algorithms were tested with a proprietary EEG data set involving 4 individuals and with a data set provided by the University of Graz (Austria) as well. The resulting classification system is now being implemented in a Brain-Computer Interface (BCI) used to guide a robotic wheelchair.

Optimized design of a back-to-back NPC converter to be used as interface for renewable energies

As the number of wind power with power electronics interfaces in the grid increases, it becomes unacceptable to disconnect the generating units every time a disturbance occurs, as was a common practice in the past. Keeping the converter online during unbalanced voltage and guaranteeing the actual standards of the converter connected to the grid becomes a very critical issue. From these goals, the design of a robust back-to-back NPC (three levels) converter of 100 KVA is researched in this work. The converter is divided into two main parts: the power electronics system and the control electronics system. In both designs, some important contributions are shown. Concerning the first part, the paper presents primarily the converter limitations to compensate unbalanced dips, the grid filter design and the DC-bus capacitor design. Concerning the control electronics system, the chosen electronic structure and the tasks distribution between the chosen processors are shown.

XPFCP: An Extended Particle Filter for Tracking Multiple and Dynamic Objects in Complex Environments

The work presented in this paper explores a new solution for tracking multiple and dynamic objects in complex environments. An extended particle filter (XPF) is used to implement a multimodal distribution that will represent the most probable estimation for each object position. A standard particle filter (PF) cannot be used with a variable number of obstacles, and some other solutions have been tested in different previous works, but most of them are very expensive in time and memory resources at least for a high number of obstacles to be tracked. The solution exposed here includes a clustering procedure that increases the robustness of the probabilistic process to adapt itself on-line to the variable number of clusters. The presented algorithm has been tested with sonar and stereovision measurements and some results included in the paper show the efficiency of the proposed work.

Locally-referenced ultrasonic--LPS for localization and navigation.

This paper presents a flexible deployment of ultrasonic position sensors and a novel positioning algorithm suitable for the navigation of mobile robots (MRs) in extensive indoor environments. Our proposal uses several independently-referenced local positioning systems (LPS), which means that each one of them operates within its own local reference system. In a typical layout, an indoor extensive area can be covered using just a reduced set of globally-referenced LPS (GRLPS), whose beacon positions are known to the global reference system, while the rest of the space can be covered using locally-referenced LPSs (LRLPS) that can be distributed arbitrarily. The number of LRLPS and their position can be also changed at any moment. The algorithm is composed of several Bayesian filters running in parallel, so that when an MR is under the GRLPS coverage area, its position is updated by a global filter, whereas when the MR is inside the LRLPS area, its position is updated using position increments within a local filter. The navigation algorithm has been tested by simulation and with actual data obtained using a real set of ultrasonic LPSs.