Calibration and External Force Sensing for Soft Robots using an RGB-D Camera

International audienceBenefiting from the deformability of soft robots, calibration and force sensing for soft robots are possible using an external vision-based system, instead of embedded mechatronic force sensors. In this paper, we first propose a calibration method to calibrate both the sensor-robot coordinate system and the actuator inputs. This task is addressed through a sequential optimization problem for both variables. We also introduce an external force sensing system based on a real-time Finite Element (FE) model with the assumption of static configurations, and which consists of two steps: force location detection and force intensity computation. The algorithm that estimates force location relies on the segmentation of the point cloud acquired by an RGB-D camera. Then, the force intensities can be computed by solving an inverse quasi-static problem based on matching the FE model with the point cloud of the soft robot. As for validation, the proposed strategies for calibration and force sensing have been tested using a parallel soft robot driven by four cables

Contribution à une approche interdisciplinaire de la conception des systèmes mécaniques commandés : application aux axes de machines

An interdisciplinary approach of controlled mechanical system design is used for the first-project step. We put emphasis on pluridisciplinary character of the design and on structure induction task during the predesign ; a methodology is proposed in order to achieve a global synthesis by identifying predominant phenomena. Their minimum model may lead to a solution structure which verified performance requirements. The study aims to synthesize controlled mechanisms. Based on dynamic interaction between mechanism and feedback-characterized by spillover and (non)colocated sensors- a minimum model is worked out for the interdisciplinary synthesis. Model analysis provides some interaction properties which are useful for the designer, especially for the location choices of position and speed sensor. Some nondimensional laws for the interdisciplinary synthesis of mechanisms are obtained from the algebric resolution of inverse problem. A “versatile” pole placement of servomechanism is established so as to specify the dynamic performances to be performed by the mechanism. These synthesis laws are associated with some classical laws dedicated to the choices of actuator and transmission ratio. Application to drive system of machine leads to a step-by-step approach and a more synthetic approach. Based on stated requirements and manufacturer catalogues a high speed translation drive system with a ball screw system can be design : actuator, kinematic, mechanism setting are chosen owing to presizing of the solutions.Une approche interdisciplinaire de la conception des systèmes mécaniques commandés est adoptée pour la phase d'avant-projet. Soulignant le caractère pluridisciplinaire de la conception et la tâche d'induction de structure lors de la préconception, une méthodologie est proposée afin d'appréhender la synthèse dans sa globalité en identifiant les phénomènes prédominants. Leur modélisation minimum doit permettre de choisir une structure de solution qui vérifiera les spécifications de performances. L’étude concerne plus précisément la synthèse des mécanismes commandes. À partir de l'interaction dynamique entre le mécanisme et sa boucle de régulation -caractérisée par le spillover et la (non)colocalisation des mesures- un modèle minimum est élaboré pour la synthèse interdisciplinaire. L’analyse du modèle fournit des propriétés de l'interaction utiles au concepteur, notamment pour le choix de la localisation des mesures de position et de vitesse. Des lois adimensionnelles de synthèse interdisciplinaire du mécanisme sont obtenues à partir de la résolution algébrique du problème inverse. Les performances dynamiques à atteindre par le mécanisme sont spécifiées grâce a un placement > des pôles du servomécanisme. Ces lois de synthèse sont complétées par les lois classiques pour le choix de l'actionneur et du rapport de transmission. L’application aux axes de machine donne lieu à deux démarches de préconception complémentaires, l'une pas à pas, l'autre plus synthétique. Pour un axe en translation grande vitesse de type vis-a-billes, les choix d'actionneur, de cinématique, de montage de vis sont faits à partir du prédimensionnement des solutions, étant donne un cahier des charges et des catalogues-constructeurs

Dynamics of railway track subjected to distributed and local out-of-round wheels

The dynamic response of a railway track under a moving train in the presence of a defective wheel is studied. The goal of this study is to establish an efficient dynamic model for wheel tread defect analysis. The wheel irregularities which influence the track vibration characteristics are classified in 2 major types: periodic out-of-roundness and local defect. While the periodic irregularities are distributed all around the wheel, the local defects such as wheelflats have more impact on the dynamic response. The influence of each defect depends on its geometrical characteristics and the model parameters. The separate effects of different irregularities have been the subject of many previous researches. However the contribution of each defect to a coupling of irregularities was not as much considered. For a comprehensive analysis of all types of defects, an efficient global model is presented. It includes 3 sub-models for vehicle, contact force and track. The time-domain responses of the model are evaluated in comparison to those of a finite element model. It is shown that the semi-analytical model of the track keeps a good precision while being less time consuming. The results of the global model for different types of wheel irregularities are presented

Reduced-Complexity Affine Representation for Takagi-Sugeno Fuzzy Systems

International audienceThis paper presents a systematic approach to reduce the complexity of sector nonlinearity TS fuzzy models using existing linear dependencies between local linear submodels. The proposed approach results in a decrease of the fuzzy model rules from 2P to p + 1 rules while maintaining equivalence to the TS fuzzy model. An LMI formulation is presented to obtain conditions for stability analysis and stabilizing controllers design with some examples to offer a comparison between the two models. The main purpose of reduced-complexity models is to keep the design and the structure of the nonlinear control and observer schemes as simple as possible for real-time implementation, especially when dealing with highly nonlinear systems with a very large number of premise variables. Two real-world robotics examples are provided to highlight the interests and the curent limitations of the proposed approach

Characteristics of postinflammatory hyper- and hypopigmentation in patients with psoriasis: A survey study

International audienceNo abstract availabl

Agroforestry in the Hauts-de-France -A Research and Demonstration Experimental Site in Ramecourt

AFFInternational audienceAs the current agricultural practices in the Hauts-de-France region result in soil erosion, nitrate leaching and a decline in biodiversity, agroforestry systems (AFs) may be an alternative to conciliate productivity with lower environmental impact (Dupraz and Liagre, 2008). We set up the first AF experimental site to study its agro-economic and environmental performance in local agro-pedoclimatic conditions. The experimental site was established in autumn 2018 on an 18-ha plot in Ramecourt on a deep luvic cambisol with a silt loam texture developed on a flint clay. Due to a high silt content (73% silt) and a low organic matter content (2%), as well as a slope of 8%, the plot is highly affected by channel erosion. Modalities with or without nitrogen-fixing trees in AF treatment are compared with sole-crop (CC) and pure-forest control (FC) plots (Figure 1A) according to a randomised block design with 3 replicates. Tall trees in rows are intercalated with 9 species of shrubs (Figure 1B) and will be intercropped in AFs by sugar beet, potato, wheat, barley and flax. The tree density is 50 and 430 trees ha-1 for AFs and FC respectively, and the average size of the microplots is 0.9 ha. Using this experimental approach, we hypothesised that AFs should limit soil erosion, restore soil fertility and biodiversity, improve natural-resource use efficiency and water quality, reduce inputs and increase farmers’ incomes