Ana C. Lopes

Wheelchair navigation assisted by Human-Machine shared-control and a P300-based Brain Computer Interface

This paper presents a new shared-control approach for assistive mobile robots, using Brain Computer Interface (BCI) as the Human-Machine Interface (HMI). A P300-based paradigm that allows the selection of brain-actuated commands to steer a Robotic Wheelchair (RW), is proposed. At least one specific motor skill, such as the control of arms, legs, head or voice, is required to operate a conventional HMI. Due to this reason, they are not suited for people suffering from severe motor disorders. BCI may open a new communication channel to these users, since it does not require any muscular activity. The number of decoded symbols per minute (SPM) in a BCI is still very low, which means that users can only provide sparse, and discrete commands. The RW must rely on the navigation system to validate user commands effectively. A two-layer shared-control approach is proposed. The first, a virtual-constraint layer, is responsible for enabling/disabling the user commands, based on certain context restrictions. The second layer is an user-intent matching responsible for determining the suitable steering command, that better fits the user command, taking the user competence on steering the wheelchair into account. Experimental results using Robchair, the RW platform developed at ISR-UC [1], [2] are presented, showing the effectiveness of the proposed methodologies.

An outdoor guidepath navigation system for AMRs based on robust detection of magnetic markers

This paper presents an outdoor guidepath navigation system for autonomous mobile robots (AMR) that use permanent magnetic markers embedded in the ground. The odometric data provided by the wheel encoders is fused with the data from magnetic markers. The extended Kalman filter (EKF) was chosen for the fusion process. The AMR is equipped with a magnetic sensing ruler (MSR) developed at ISR-UC that is able to perform a robust detection of magnetic markers. The detection is based on a 3-D algorithm that includes longitudinal-fitting detection (LFD), and cross-fitting detection (CFD). Both, the LFD and the CFD are based on the least squares fitting (LSF) of the measurement data with the 3-D model of the vertical magnetic field. The experimental results with Robchair (intelligent wheelchair being developed at ISR-UC) primarily show that the detection system is robust, since it is able to detect true magnetic markers, and to eliminate noisy magnetic distortions and false markers. The design, and implementation of the navigation algorithm in the Robchair were carried out, and results are presented.

RobChair: Experiments evaluating Brain-Computer Interface to steer a semi-autonomous wheelchair

Experiments with a semi-autonomous wheelchair controlled by means of a Brain-Computer Interface (BCI) are presented. The navigation system, having at its core a collaborative controller, performs smooth and safe manoeuvres following sparse steering commands provided by the user. The user intents are decoded from electroencephalographic signals evoked by a visual P300-based paradigm. Experiments have been performed by several able-bodied users and motor disabled participants, showing the effectiveness of the approach.

A Fast Firing Binaural System for Ultrasonic Pattern Recognition

A binaural sonar configuration with capability to detect and identify walls, edges and corners on real-time is presented in this work. A new multi-echo ultra-fast firing method increases the sonar acquisition rate, and provides crossed measurements without interference. A feature map is built on-line using Bayesian updating and classification rules. Three classifiers are implemented and analyzed: minimum risk (MR), maximum a posteriori (MAP), and minimum distance (MD). Experimental results of ultrasonic reflector recognition, using data collected in a specular indoor environment are presented in the paper.

A New Hybrid Motion Planner: Applied in a Brain-Actuated Robotic Wheelchair

This article presents a new hybrid motion (HM) planner, designed to allow robust indoor navigation in constrained environments of nonholonomic differential robots, such as RobChair, the brain-actuated robotic wheelchair from the Institute of Systems and Robotics, University of Coimbra, Portugal. Relying on this new planning algorithm, RobChair is now able to operate in real dynamic environments and perform challenging maneuvers in narrow spaces. The HM planner integrates deliberative and reactive modules in a three-layer structure: a fast three-dimensional (3-D)-global path planner, smoothing, and a new reactive local planner designated the double-dynamic window approach (D-DWA). The 3-D-global path planner consists in the A* algorithm, which defines a path composed by a sequence of (x, y) points, with an interpolation module that has the purpose of assigning an orientation to each (x, y) point. The smoothing algorithm adjusts the (x, y) points to reduce accelerations and jerk associated with the trajectory. The D-DWA is in charge of dynamically adapting the robot motion, taking into account the robot geometry (noncircular robot) and local static/dynamic obstacles, unknown from the global planner perspective. Real-time navigation is achieved because both the smoothing and the D-DWA algorithms are iteratively executed during navigation. The use of multiresolution local grid maps also contributes to the increase of computation performance. To show the effectiveness of the proposed planning algorithm, results of real navigation experiments are reported in this article. The experiments consist in steering RobChair in a real office-like scenario by different participants, using a self-paced P300-based brain-computer interface (BCI).

Improving discrimination in the grading of rat mammary tumors using two-dimensional mapping of histopathological observations

This work aims at characterizing rat mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) and the respective malignancy potential, commonly graded with histopathology features grouped by intensity levels. Tumors were described over fourteen multiple ranged microscopic parameters and a comprehensive characterization of the histological patterns and their relation with tumor grade was carried out by principal component analysis (PCA). The number of histological patterns present on a tumor tends to correlate with malignant features. High grade tumors are characterized by the presence of several structural patterns, with cribriform prevalence and necrosis. The cribriform pattern correlates with grading, i.e., tumors having a higher predominance of the cribriform pattern are likely to be more malignant. The findings may represent a benchmark for similar characterization studies in other models.

Study of the influence of the matrix characteristics over the photocatalytic ozonation of parabens using Ag-TiO2

Parabens are widely used as antimicrobial and preservative in pharmaceutical and personal products. Their presence has been detected in rivers and wastewater treatment plants. Photocatalytic ozonation process using a low amount of 0.1 wt% Ag-TiO2 proved to be efficient on the degradation of a mixture of five parabens using a low transferred ozone dose (TOD). The pH effect was analyzed under acidic and neutral conditions. Also, the effect of hydroxyl radical scavenger on parabens degradation and on by-products formation was discussed. Hydroxyl radical present a significant role over parabens degradation and also on by-products formation. The reaction mechanism was analyzed using municipal wastewater as a matrix to infer about the behavior of the process at actual conditions. Municipal wastewater as a matrix clearly enhanced the parabens degradation when compared with the case where ultrapure water was used. In fact, the TOD required for total parabens degradation is lowered 10-20 mg/L of TOD. Therefore, to understand the main responsible species for this improvement, the effects of several ions naturally present in wastewater (HCO3-, Cl- and SO42-) were tested. According to the results it seems that sulfate radical improves the process, while chloride and bicarbonate radicals decrease the process efficiency. In terms of toxicity the luminescence inhibition for Vibrio fischeri was analyzed. The inhibition significantly decreased for treated spiked municipal wastewater.

Contributos para uma análise semântico-pragmática das causais de enunciação no português europeu contemporâneo

O objetivo deste trabalho e caracterizar as oracoes causais de enunciacao num quadro teorico que postula a existencia, no discurso, de distintos dominios da significacao - dominio do conteudo, dominio epistemico e dominio ilocutorio-, na conviccao de que uma analise semântica destas construcoes podera contribuir para iluminar o seu comportamento sintatico peculiar, que tanta controversia tem gerado. Defende-se, neste estudo, que as oracoes causais de enunciacao expressam a relacao discursiva de Justificacao, que envolve sempre a articulacao de dois atos ilocutorios, um deles com o estatuto de ato principal, o outro com o estatuto de ato subordinado. Num primeiro momento, analisa-se a articulacao entre causais de enunciacao e assercoes e argumenta-se a favor da inseparabilidade entre os dominios epistemico e ilocutorio neste tipo de construcoes, contrariamente ao que defende Sweetser (1999). Num segundo momento, analisa-se a articulacao entre causais de enunciacao e outras classes de atos ilocutorios, nomeadamente atos diretivos, compromissivos e expressivos.

Real-time architecture for mobile assistant robots

Mobile robotics is a challenging research area, with produced results that were unthinkable several years ago. There exist algorithms and methods capable of performing difficult tasks such as detect/classify objects, skill learning and SLAM. From the initial design steps, the real-time software architecture of a robotic platform requires great attention. The problem is difficult, because various components, such as sensing, perception, localization, and motor control, are required to operate and interact in real-time. This makes the system a very complex one. This paper presents a real-time control architecture designed for mobile robots and intelligent vehicles. Moreover, an example of application of the control structure consisting on a system for learning to classify places, using laser range data, is reported.

Mobility, Accessibility and Safety of People with Cerebral Palsy

This research characterizes mobility, accessibility and safety of individuals with severe motor impairment such as users suffering from Cerebral Palsy (CP). Through the analysis of enabling factors, constraints associated and the search of possible improvements, it is possible to identify the needs in these fields and subsequently develop strategies accordingly. The sample was collected in Coimbra Cerebral Palsy Association (APCC) and it included 16 individuals with CP. To these individuals we gave an evaluation protocol with a form with clinical and sociodemographic data and a questionnaire. The main limiting factors include building/vehicle access, difficulty in reverse drive and lack of safety. The most valued features of a powered wheelchair are comfort and structure, easy navigation and wheelchair control and safety. The lack of safety in the outdoors was a relevant limiting factor. Almost all individuals requested improvements of the powered wheelchair. The most requested improvements were safety related or related with navigation problems. An assistive navigation solution based on a shared control algorithm is presented, where a powered wheelchair is equipped with the Kinect sensor, in order to help the user maneuvering the wheelchair safely.