8 research outputs found
The Unicycle in Presence of a Single Disturbance: Observability Properties
International audienceThis paper investigates the observability properties of a mobile robot that moves on a planar surface by satisfying the unicycle dynamics and that is equipped with exteroceptive sensors (visual or range sensors). In accordance with the unicycle dynamics, the motion is powered by two independent controls, which are the linear and the angular speed, respectively. We assume that both these speeds are known. We consider the case when the robot motion is affected by a disturbance (or unknown input) that produces an additional (unknown and time dependent) robot speed along a fixed direction. The goal of the paper is to obtain the observability properties of the state that characterizes the robot configuration. The novelty of this observability analysis is that it takes into account the presence of an unknown and time dependent disturbance. Previous works that analyzed similar localization problems, either did not consider the presence of disturbances, or assumed disturbances constant in time. In order to deal with an unknown and time dependent disturbance , the paper adopts a new analytic tool [18]. This analytic tool is the solution of a fundamental open problem in control theory (the Unknown Input Observability problem in the general nonlinear case). We show that the application of this analytic tool is very simple and can be implemented automatically. Additionally, we simulate the aforementioned system and we show that a simple estimator based on an Extended Kalman Filter provides results that fully agree with what we could expect from the observability analysis
Grasp input optimization taking contact position and object information uncertainties into consideration
This paper presents a novel approach for grasp optimization considering contact position and object information uncertainties. In practice, it is hard to grasp an object at the designated or planned contact positions, as errors in measurement, estimation, and control usually exist. Therefore, we first formulate the influences of contact uncertainties on joint torques, contact wrenches, and frictional condition. We then include external wrench uncertainties in the required external wrenches set. Based on this formulation, we define the linear grasp optimization problem for two kinds of frictional contact modelsfrictional point contact and soft finger contactso that we can successfully grasp an object even if deviations in contact point, object weight, and center of mass occur. The validity of our approach is shown by means of numerical examples and the result of experiments. Ā© 2004-2012 IEEE
Cartographie, localisation et planification simultaneĢes āen ligneā, aĢ long terme et aĢ grande eĢchelle pour robot mobile
Pour eĢtre en mesure de naviguer dans des endroits inconnus et non structureĢs, un robot doit pouvoir cartographier lāenvironnement afin de sāy localiser. Ce probleĢme est connu sous le nom de cartographie et localisation simultaneĢes (ou SLAM pour Simultaneous Localization and Mapping). Une fois la carte de lāenvironnement creĢeĢe, des taĢches requeĢrant un deĢplacement dāun endroit connu aĢ un autre peuvent ainsi eĢtre planifieĢes. La charge de calcul du SLAM est deĢpendante de la grandeur de la carte. Un robot a une puissance de calcul embarqueĢe limiteĢe pour arriver aĢ traiter lāinformation āen ligneā, cāest-aĢ-dire aĢ bord du robot avec un temps de traitement des donneĢes moins long que le temps dāacquisition des donneĢes ou le temps maximal permis de mise aĢ jour de la carte. La navigation du robot tout en faisant le SLAM est donc limiteĢe par la taille de lāenvironnement aĢ cartographier.
Pour reĢsoudre cette probleĢmatique, lāobjectif est de deĢvelopper un algorithme de SPLAM (Simultaneous Planning Localization and Mapping) permettant la navigation peu importe la taille de lāenvironment. Pour geĢrer efficacement la charge de calcul de cet algorithme, la meĢmoire du robot est diviseĢe en une meĢmoire de travail et une meĢmoire aĢ long terme. Lorsque la contrainte de traitement āen ligneā est atteinte, les endroits vus les moins souvent et qui ne sont pas utiles pour la navigation sont transfeĢreĢes de la meĢmoire de travail aĢ la meĢmoire aĢ long terme. Les endroits transfeĢreĢs dans la meĢmoire aĢ long terme ne sont plus utiliseĢs pour la navigation. Cependant, ces endroits transfeĢreĢs peuvent eĢtre reĢcupeĢreĢes de la meĢmoire aĢ long terme aĢ la meĢmoire de travail lorsque le le robot sāapproche dāun endroit voisin encore dans la meĢmoire de travail. Le robot peut ainsi se rappeler increĢmentalement dāune partie de lāenvironment a priori oublieĢe afin de pouvoir sāy localiser pour le suivi de trajectoire.
Lāalgorithme, nommeĢ RTAB-Map, a eĢteĢ testeĢ sur le robot AZIMUT-3 dans une premieĢre expeĢrience de cartographie sur cinq sessions indeĢpendantes, afin dāeĢvaluer la capaciteĢ du systeĢme aĢ fusionner plusieurs cartes āen ligneā. La seconde expeĢrience, avec le meĢme robot utiliseĢ lors de onze sessions totalisant 8 heures de deĢplacement, a permis dāeĢvaluer la capaciteĢ du robot de naviguer de facĢ§on autonome tout en faisant du SLAM et planifier des trajectoires continuellement sur une longue peĢriode en respectant la contrainte de traitement āen ligneā . Enfin, RTAB-Map est compareĢ aĢ dāautres systeĢmes de SLAM sur quatre ensembles de donneĢes populaires pour des applications de voiture autonome (KITTI), balayage aĢ la main avec une cameĢra RGB-D (TUM RGB-D), de drone (EuRoC) et de navigation inteĢrieur avec un robot PR2 (MIT Stata Center).
Les reĢsultats montrent que RTAB-Map peut eĢtre utiliseĢ sur de longue peĢriode de temps en navigation autonome tout en respectant la contrainte de traitement āen ligneā et avec une qualiteĢ de carte comparable aux approches de lāeĢtat de lāart en SLAM visuel et avec teĢleĢmeĢtre laser. ll en reĢsulte dāun logiciel libre deĢployeĢ dans une multitude dāapplications allant des robots mobiles inteĢrieurs peu couĢteux aux voitures autonomes, en passant par les drones et la modeĢlisation 3D de lāinteĢrieur dāune maison
Design and Development of Biofeedback Stick Technology (BfT) to Improve the Quality of Life of Walking Stick Users
Biomedical engineering has seen a rapid growth in recent times, where the aim to facilitate and equip humans with the latest technology has become widespread globally. From high-tech equipment ranging from CT scanners, MRI equipment, and laser treatments, to the design, creation, and implementation of artificial body parts, the field of biomedical engineering has significantly contributed to mankind. Biomedical engineering has facilitated many of the latest developments surrounding human mobility, with advancement in mobility aids improving human movement for people with compromised mobility either caused by an injury or health condition. A review of the literature indicated that mobility aids, especially walking sticks, and appropriate training for their use, are generally prescribed by allied health professionals (AHP) to walking stick users for rehabilitation and activities of daily living (ADL). However, feedback from AHP is limited to the clinical environment, leaving walking stick users vulnerable to falls and injuries due to incorrect usage. Hence, to mitigate the risk of falls and injuries, and to facilitate a routine appraisal of individual patientās usage, a simple, portable, robust, and reliable tool was developed which provides the walking stick users with real-time feedback upon incorrect usage during their activities of daily living (ADL).
This thesis aimed to design and develop a smart walking stick technology: Biofeedback stick technology (BfT). The design incorporates the approach of patient and public involvement (PPI) in the development of BfT to ensure that BfT was developed as per the requirements of walking stick users and AHP recommendations. The newly developed system was tested quantitatively for; validity, reliability, and reproducibility against gold standard equipment such as the 3D motion capture system, force plates, optical measurement system for orientation, weight bearing, and step count. The system was also tested qualitatively for its usability by conducting semi-informal interviews with AHPs and walking stick users. The results of these studies showed that the newly developed system has good accuracy, reported above 95% with a maximum inaccuracy of 1Ā°. The data reported indicates good reproducibility. The angles, weight, and steps recorded by the system during experiments are within the values published in the literature. From these studies, it was concluded that, BfT has the potential to improve the lives of walking stick users and that, with few additional improvements, appropriate approval from relevant regulatory bodies, and robust clinical testing, the technology has a huge potential to carve its way to a commercial market