F. Díaz del Río

A generalization of path following for mobile robots

Several authors have proposed some methods for applying path following in specific cases to mobile robots. When we try to extend the path following approach to the general problem several difficulties arise. We present a generalized technique to apply path following to a mobile robot with nonholonomic constraints. As an application example, we expose the case of mobile robots with a higher degree of manoeuvrability than the typical car-like robots. In particular we consider a robot that can turn around itself making a zero-radius turn; a case still not resolved as far as we know. Finally we propose a suitable control law for this example that ensures asymptotical convergence.

TetraNauta: a intelligent wheelchair for users with very severe mobility restrictions

The TetraNauta project is a low cost, fully open steering system to allow people with heavy motor impairments to move in a known environments (hospitals, schools, home, etc.). It minimizes the steering effort, especially in long paths, while caring for user safety. Every TetraNauta wheelchair has a general map of the environment wherein it navigates in automatic mode. It also knows its actual position in the map using on-board sensors that detect absolute positioning marks. The system consists of a traffic management subsystem and wheelchair motion control subsystem. Virtual potential fields as a tool for implementing automatic guidance in the intelligent electric wheelchair are considered.The TetraNauta project is a low cost, fully open steering system to allow people with heavy motor impairments to move in a known environments (hospitals, schools, home, etc.). It minimizes the steering effort, especially in long paths, while caring for user safety. Every TetraNauta wheelchair has a general map of the environment wherein it navigates in automatic mode. It also knows its actual position in the map using on-board sensors that detect absolute positioning marks. The system consists of a traffic management subsystem and wheelchair motion control subsystem. Virtual potential fields as a tool for implementing automatic guidance in the intelligent electric wheelchair are considered.

A real-time wireless sensor network for wheelchair navigation

Today, the availability of inexpensive, low power hardware including CMOS cameras and wireless devices make it possible to deploy a wireless sensor network (WSN) with nodes equipped with cameras for a variety of applications. In this paper, we discuss the use of one of these WSNs as a navigation aid for wheelchairs. Instead of having complicated wheelchairs with lots of on-board sensors, we argue that a viable alternative is to have simpler wheelchairs that are able to interact with an intelligent environment so that the wheelchair bases its navigation on its software intelligence, supported by the information sent by external sensors. Many questions have to be investigated, for instance how sensors should be deployed or whether the wireless links would be able to meet our temporal requirements. We describe some of the solutions we adopted, particularly how to implement with Zigbee devices a polling mechanism that allows us to guarantee a real-time secure navigation.

SIRIUS: improving the maneuverability of powered wheelchairs

The indoor maneuverability of powered wheelchairs may be difficult or bothersome in several circumstances. In this paper, we describe an experimental powered wheelchair named SIRIUS, developed at the University of Seville, which introduces some simple but effective navigation aids. Special emphasis is placed on the implementation of recorded trajectory playback and in the shared control modes, i.e., the chairs guiding where both the user and the computer collaborate. Furthermore, SIRIUS is an open platform to essay another kinds of functional or navigational aids, because its hardware architecture is based on a commercial PC. This would permit many devices that are frequently needed by the chair driver to be integrated smoothly into the chair controller.

eDiab: a system for monitoring, assisting and educating people with diabetes

In this paper, a system developed for monitoring, assisting and educating people with diabetes, named eDiab, is described. A central node (PDA or mobile phone) is used at the patients side for the transmission of medical information, health advices, alarms, reminders, etc. The software is adapted to blind users by using a screen reader called Mobile Speak Pocket/Phone. The glucose sensor is connected to the central node through wireless links (Zigbee/Bluetooth) and the communication between the central node and the server is established with a GPRS/GSM connection. Finally, a subsystem for health education (which sends medical information and advice like treatment reminder), still under development, is briefly described

Soft real-time communications over Bluetooth under interferences from ISM devices

Bluetooth is a suitable technology to support soft real-time applications like multimedia streams at the personal area network level. In this paper, we analytically evaluate the worst-case deadline failure probability of Bluetooth packets under co-channel interference as a way to provide statistical guarantees when transmitting soft real-time traffic using ACL links. We consider the interference from independent Bluetooth devices, as well as from other devices operating in the ISM band like 802.11b/g and Zigbee. Finally, we show as an example how to use our model to obtain some results for the transmission of a voice stream. Copyright

An analytical model of inter-channel interference in Bluetooth-based systems

One of the main advantages of the Bluetooth standard is that it provides a way to support ad-hoc connectivity between a variable number of devices at low cost. However, in situations with many Bluetooth devices that coexist in the same area the problem of channel interference may become of high importance. In this paper, we present an analysis that provides some expressions for the channel throughput and the delay that packets suffer due to possible collisions with other Bluetooth devices. The model includes the different effects of new and retransmitted packets. Both synchronized and unsynchronized systems are considered. Furthermore, although the effect of propagation losses are not explicitly considered, we show how they could be included in our model.

Function generator to study the dielectric breakdown in thin film structures

Characterization of breakdown in thin films requires testing experimental samples with different voltage patterns in order to obtain dielectric parameters, e.g. breakdown voltage and charge to breakdown. The most common voltage patterns used are voltage ramp and step. This paper describes design and implementation of a function generator especially suited for thin films testing. The generator can be controlled using a computer, performing many different voltage patterns. This feature makes it a very versatile instrument, useful in a wide range of experiments. The system is based on a switching DC power supply (flyback converter), controlled by a computer (on-board microcontroller). The control system is a PD with a feedforward loop.

A parametric formulation of tracking methods: application to chained systems

When following a path, there are several possibilities attending to the way in which the actual robot state can be related with the whole path. In this work, we formulate different tracking methods on the base that a memorized path can be described by a single descriptor parameter (the objective point is readily given by this parameter). We classify path tracking according to the way in which we impose or design the progress of descriptor parameter. Benefits and disadvantages of each method are identified. We also summarize how to construct each method. Despite that this classification is generic, application to mobile robots and chained systems is very valuable due to the importance of tracking problem in them and because their desired path is usually memorized