Showing papers by "Damien Chablat published in 2019"

Kinetostatic analysis and solution classification of a class of planar tensegrity mechanisms

Abstract: Tensegrity mechanisms are composed of rigid and tensile parts that are in equilibrium. They are interesting alternative designs for some applications, such as modelling musculo-skeleton systems. Tensegrity mechanisms are more difficult to analyze than classical mechanisms as the static equilibrium conditions that must be satisfied generally result in complex equations. A class of planar one-degree-of-freedom tensegrity mechanisms with three linear springs is analyzed in detail for the sake of systematic solution classifications. The kinetostatic equations are derived and solved under several loading and geometric conditions. It is shown that these mechanisms exhibit up to six equilibrium configurations, of which one or two are stable, depending on the geometric and loading conditions. Discriminant varieties and cylindrical algebraic decomposition combined with Groebner base elimination are used to classify solutions as a function of the geometric, loading and actuator input parameters.

Dynamic Model of a Bio-Inspired Robot for Piping Inspection

Abstract: Piping inspection robots are of great importance in industries such as nuclear, sewage and chemical where the internal diameters of the pipeline are significantly smaller. Mechanisms having closed loops can be used in such areas as they generate contact forces and deployable structures. With the help of a bio-inspired mechanism, a piping inspection robot is presented which mimics the motion of a caterpillar. The robot is composed of three modules: a central module for elongation and two other modules on the front and rear for clamping. A slot-slider mechanism is chosen for the legs of the robot. Using industrial components such as DC motors, servo-controllers, ball screws and fasteners, the entire robotic system was realized in CATIA software and a prototype was made at the Laboratoire des Sciences du Numerique de Nantes (LS2N). In this article, we present the forces induced on the motors under locomotion using a dynamic analysis. With the help of the recursive Newton-Euler algorithm, the torques generated on the motor under locomotion have been identified which ensures the stability of the system while moving inside pipes.

Advancement of MSA-Technique for Stiffness Modeling of Serial and Parallel Robotic Manipulators

Abstract: The paper presents advancement of the matrix structural analysis technique (MSA) for stiffness modeling of robotic manipulators. In contrast to the classical MSA, it can be applied to both parallel and serial manipulators composed of flexible and rigid links connected by rigid, passive or elastic joints with multiple external loadings. The manipulator stiffness model is presented as a set of basic equations describing the link elasticities that are supplemented by a set of constraints describing connections between links. These equations are aggregated straightforwardly in a common linear system without traditional merging of the matrix rows and columns, which allows avoiding conventional manual transformations at the expense of numerical inversion of the sparse matrix of higher dimension.

A new inspection robot for pipelines with bends and junctions

Abstract: The application of robots for the inspection of pipelines are of greater significance in industries such as nuclear, chemical and sewage. The major problem in the design of these robots lies in the selection of a suitable locomotion principle, selection of an articulation unit that facilitates the robot to pass through pipe bends and management of cables. In this context, the design of a new bio-inspired piping inspection robot that resembles an elephant trunk has been presented. With the help of leg mechanisms and actuators, a caterpillar locomotion is used within this trunk for establishing adaptive contact points with the walls of pipeline. For the passage through bends and junctions, several case studies of existing researches have been taken into account for the design of an articulation unit. Two solutions, (i) a passive tensegrity structure and (ii) an active tensegrity structure have been proposed for the robot to pass through pipe bends and junctions. A detailed design analysis of the passive solution that uses a universal joint has been presented in this article.

Design and Analysis of a Tensegrity Mechanism for a Bio-Inspired Robot

Abstract: Piping inspection robots are of greater interests in industries such as nuclear, chemical and sewage. The design of such robots is highly challenging owing to factors such as locomo-tion inside pipes with varying diameters, cable management,and complex pipe bends (or) junctions. A rigid bio-inspired caterpillar type piping inspection robot was developed at LS2N, France. By introducing tensegrity mechanisms and four-bar wheel mechanisms , the design of this robot is modified into a reconfigurable system. The tensegrity mechanism employs a passive universal joint with three tension springs and three cables for actuation. The positioning of the end effector with respect to the base of the mechanism plays an important role in determining the maximum tilt angle (or) bending limit of the system. By workspace analysis of three case studies, the best solution is chosen which generates the maximum tilt. A static force analysis is then performed on the mechanism to determine its stability under the influences of preload. By the modification of design parameters, stable configurations are determined followed by which cable actuation of mechanism is analyzed for estimating applied forces.

Using Maple to analyse parallel robots

Abstract: We present the SIROPA Maple Library which has been designed to study serial and parallel manipulators at the conception level. We show how modern algorithms in Computer Algebra can be used to study the workspace, the joint space but also the existence of some physical capabilities w.r.t. to some design parameters left as degree of freedom for the designer of the robot.

A Full-Chain OpenSim Model and Its Application on Posture Analysis of an Overhead Drilling Task

Abstract: Biomechanical motion simulation and kinetic analysis of human joints and muscles provide insights into Musculoskeletal disorders. OpenSim is an open-source platform that give easy access to biomechanical analysis, especially of muscles. The biomechanical analysis in OpenSim is based on pre-defined human models. Among the dozens of models available right now, none covers the muscles and joints of all the body parts. In view of the fact that most human motions are systemic, the lack of a comprehensive model prohibits synthesized and systematical biomechanical analysis. The aim of this research is to develop an OpenSim model which enables the full-chain dynamic analysis of tasks involving multi-bodies. The model is developed based on two existing models. It consists of 45 body segments, 424 muscles and 39 degrees of freedom. The model was then used to simulate an overhead drilling task. Six drilling postures are analyzed, and the estimated joint moments and muscle activations are compared .

Prototype of a tensegrity manipulator to mimic bird necks

Abstract: Une structure de tensegrite est un assemblage d'elements en compression (barres) et d'elements en traction (câbles, ressorts) maintenus ensemble en equilibre [1],[2]. La tensegrite est connue en architecture et en art depuis plus d'un siecle [3] et est adaptee a la modelisation des organismes vivants [4]. Les me-canismes de tensegrite ont ete etudies plus recemment pour leurs proprietes prometteuses en robotique telles que la faible inertie, la souplesse naturelle et la capacite de deploiement [5]. Un mecanisme de tensegrite est obtenu lorsqu'un ou plusieurs elements sont actionnes. Ces travaux s'inscrivent dans le cadre du projet AVINECK, auquel participent des biologistes et des roboticiens dans le but principal de modeliser et de concevoir des cous d'oiseaux. En consequence, une classe de manipulateurs de tensegrite planaire composee d'un assemblage en serie de plusieurs mecanismes en X de Snelson [6], c'est-a-dire des mecanismes a quatre barres croisees avec des ressorts sur leurs cotes lateraux, a ete choisie comme candidat approprie pour un modele preliminaire plan d'un cou d'oiseau. Le prototype consiste en un mecanisme en X de Snelson. Les barres sont assemblees selon differents plans pour eviter les collisions internes. Le manipulateur est entraine par des câbles paralleles aux res-sorts et traversant les axes grâce a des percages. Chaque câble est attache a un tambour. Le manipulateur est actionne par deux câbles, ce qui en fait un mecanisme antagoniste, dont on peut controler la raideur. Les pieces structurelles (barres, supports, tambours) sont imprimees en 3D en ABS. Chaque liaison pivot entre les barres et les axes est construite avec deux roulements qui assurent un centrage long, et toutes les pieces sont arretees axialement avec des colliers d'arbre. Nous avons decide d'avoir une lon-gueur de barre transversale de 100 mm et une longueur de barre superieure de 50 mm. Ces dimensions sont adaptees a plusieurs jeux de ressorts disponibles, c'est-a-dire que les ressorts consideres sont tou-jours en tension et ne sont pas trop etendus pour toutes les positions accessibles du manipulateur. Une fois la longueur et la raideur du ressort definies, le modele statique est calcule afin d'obtenir la force d'entree maximale pour les câbles. Cette force doit etre suffisante pour actionner le mecanisme dans un grand espace de travail et pour resister aux chargements externes. La force appliquee par les câbles est directement liee au rayon du tambour et au couple du moteur. Le rayon du tambour influe egalement sur la vitesse de translation du câble. Un compromis est fait pour avoir des efforts et vitesses de câbles suffisants. Deux variateurs interagissent avec un microprocesseur sur lequel est programme la loi de commande. Chaque moteur est equipe d'un codeur pour connaitre la position reelle du mecanisme. Le bon compor-tement du mecanisme est assure par une commande dynamique.

Prototyping a piping inspection robot using a BeagleBone black board

Abstract: As a part of a project with AREVA, an inspection robot for 50-94 mm diameter range pipelines have been developed. By using leg mechanisms, DC motors, spindle drive, and control boards, the robot accomplishes the locomotion of a caterpillar. Two algorithms can be classified for the control of this robot via Displacement control algorithm and Force control algorithm. The former deals with the estimation of the position of a robot inside a known environment and it requires sensors for identifying position as well as for initiation procedures. In the case of force control, the algorithm is highly suitable for a robot that moves inside an unknown or closed environment. Using a BeagleBone (BB) black board, the force control algorithm is developed for the inspection robot under study. As the robot works inside pipelines of unknown diameters, the reconfigurable pins of BB black are employed to apply a voltage in order to achieve the desired clamping force for having contact with pipeline walls. By setting threshold limits, the voltage and current supply to the motors can be cutoff at the end of clamping or retraction operations. With the help of ADC, the output voltage can be displayed to the user on a computer. For smooth functioning of the robot, the parameters of the motor such as the maximum velocity, direction of rotation and nominal current are calibrated prior to the start of experiments. The output voltage and currents of the motors are generated and plotted for a locomotion cycle of the robot inside a 74 mm diameter straight pipeline.

Combining precision and power to maximize performance: a case study of the woodpecker’s neck

Abstract: The neck in birds has been characterized as a highly complex system that positions the head during all kinds of behavior (Zweers et al. 1994; Bohmer et al. 2018). This involves a variety of highly ...

Topology design and analysis of a novel 3-translational parallel mechanism with analytical direct position solutions and partial motion decoupling

Abstract: According to the topological design theory and method of parallel mechanism (PM) based on position and orientation characteristic (POC) equations, this paper design a novel 3-translation (3T) PM that has three advantages, i.e., 1) it consists on three actuated prismatic joints, 2) the PM has analytical direct position solutions, and 3) the PM is of partial motion decoupling property. Firstly, the main topological characteristics such as the POC, degree of freedom and coupling degree are calculated for kinematics modelling. Due to the special constraint feature of the 3-translation, the analytical direct position solutions of the PM can be directly obtained without needing to use one-dimensional search method. Further, the conditions of the singular configuration of the PM, as well as the singularity location inside the workspace are analyzed according to the inverse kinematics.

Key Features of the Coupled Hand-operated Balanced Manipulator (HOBM) and Lightweight Robot (LWR)

Abstract: The paper deals with coupled systems including hand-operated balanced manipulators and lightweight robots. The aim of such a cooperation is to displace heavy payloads with less powerful robots. In other term, in the coupled system for handling of heavy payloads by a hand-operated balanced manipulator (HOBM) an operator is replaced by a lightweight robot (LWR). The advantages of the coupled HOBM and LWR are disclosed and the optimal design of the cooperative workspace is discussed. Behavior of the coupled system in a static mode when the velocities the HOBM are limited does not present any special problems. In this mode, the inertial forces are significantly lower than the gravitational one. The payload is completely balanced by the HOBM and the LWR assumes the prescribed displacements with low load. However, in a dynamic mode, the HOBM with massive links creates additional loads on the LWR, which can be significant. The present study considers a method for determination of inertia effects of the HOBM on the LWR. The given numerical simulations show the significant increasing of the input torques due to the inertia forces of the HOBM. Behavior of the HOBM with cable lift and the LWR is also examined.

NAVARO II, a Novel Scissor-Based Planar Parallel Robot 1

Abstract: This article presents a new variable actuation mechanism based on the 3-RPR parallel robot. This mechanismis an evolution of the NaVARo robot, a 3-RRR parallel robot, for which the second revolute joint of the threelegs is replaced by a scissor to obtain a larger working space and avoid the use of parallelograms to operate thesecond revolute joint. To obtain better spatial rigidity, the leg mechanism is constructed by placing the scissorsin an orthogonal plane to the plane of the manipulator displacement (3-RRR or even the 3-RPR). This geometricproperty brings the significant consequence of allowing the scissors to directly substitute the prismatic chains in the3-RPR and enjoy the same kinematics advantages for the overall robots as only one solution to the inverse kinematicmodel. From the Jacobian expression, surfaces of singularity can be calculated and presented in a compact form.The singularity equations are presented for a robot with a similar base and mobile platform. The properties of thescissors are then determined to have a prescribed regular workspace.

Topology design and analysis of a novel 3-translational parallel mechanism with analytical direct position solutions and partial motion decoupling

Abstract: According to the topological design theory and method of parallel mechanism (PM) based on position and orientation characteristic (POC) equations, this paper design a novel 3-translation (3T) PM that has three advantages, i.e., ① it consists on three actuated prismatic joints, ② the PM has analytical direct position solutions, and ③ the PM is of partial motion decoupling property. Firstly, the main topological characteristics such as the POC, degree of freedom and coupling degree are calculated for kinematics modelling. Due to the special constraint feature of the 3-translation, the analytical direct position solutions of the PM can be directly obtained without needing to use one-dimensional search method. Further, the conditions of the singular configuration of the PM, as well as the singularity location inside the workspace are analyzed according to the inverse kinematics.

Key Features of the Coupled Hand-operated Balanced Manipulator (HOBM) and Lightweight Robot (LWR)

Abstract: The paper deals with coupled systems including hand-operated balanced manipulators and lightweight robots. The aim of such a cooperation is to displace heavy payloads with less powerful robots. In other term, in the coupled system for handling of heavy payloads by a HOBM an operator is replaced by a LWR. The advantages of the coupled HOBM and LWR are disclosed and the optimal design of the cooperative workspace is discussed. Behavior of the coupled system in a static mode when the velocities the HOBM are limited does not present any special problems. In this mode, the inertial forces are significantly lower than the gravitational one. The payload is completely balanced by the HOBM and the LWR assumes the prescribed displacements with low load. However, in a dynamic mode, the HOBM with massive links creates additional loads on the LWR, which can be significant. The present study considers a method for determination of inertia effects of the HOBM on the LWR. The given numerical simulations show the significant increasing of the input torques due to the inertia forces of the HOBM. Behavior of the HOBM with cable lift and the LWR is also examined.

Etat de l'art des syst\`emes robotis\'es en vue d'une application pour la chirurgie otologique

Abstract: This article deals with a patents state-of-the-art linked to our robotic system which holds an endoscope. In a first part, we analyze how the endoscope operates as well as we discover the environment where we wish to use it: the middle ear. In a second step, we establish a state-of-the-art on patents existing in the robotic and surgical fields. The approach is based on a specific search methodology using keywords and classifications. Thanks to all the patents found, we gather them according their country and date of publication, and we are able to analyze the results. This study brings to light technical solutions invented in recent years and allows us to find an innovative research axis.

Etat de l'art des systèmes robotisés en vue d'une application pour la chirurgie otologique

Abstract: L'objectif de cet article est la realisation d'un etat de l'art des brevets en lien avec la robotisation des porte-endoscopes utilises en otologie. Dans une premiere partie, nous presentons les fonctions d'un endoscope ainsi que l'environnement dans lequel nous souhaitons l'utiliser : l'oreille moyenne. Dans un second temps, nous avons realise un etat de l'art des brevets existant dans les domaines de la robotique et de la chirurgie otologique. Cette approche se base sur une methodologie precise de recherche qui utilise soit des mots-cles, soit la classification des brevets. A partir de ce resultat, nous avons classifie les brevets en fonction de leurs pays de depot et de leur date de publication afin d'en faire une synthese. Cette etude permet de connaitre les solutions techniques introduites ces dernieres annees afin de guider notre demarche d'innovation.

Automatic mobility analysis of parallel mechanisms: an algorithm approach based on position and orientation characteristic equations

Abstract: The determination of the mobility of parallel mechanisms (PM) is a fundamental problem. An automatic and intelligent analysis platform will be a significant tool for the design and optimization of mechanical systems. Based on the theory of position and orientation characteristics (POC) equations, a systematic approach to computer-aided mobility analysis of PMs is presented in this paper. First, a digital model for topological structures which has a mapping relationship with position and orientation characteristics of mechanism is proposed. It describes not only the dimension of the motion output, but also gives the mapping relationship between the output characteristic and the axis of the kinematic joints. Secondly, algorithmic rules are established that convert the union and intersection operations of POC into the binary logical operations and the automatic analysis of POC are realized. Then, the algorithm of the automatic mobility analysis of PMs and its implementation with VC++ are written .The mobility and its properties (POC) will also be analyzed and displayed automatically after introducing by users of the data of topological structures representation. Finally, typical examples are provided to show the effectiveness of the software platform.

Modelling, design and control of a bird neck using tensegrity mechanisms

Abstract: In birds, the neck exhibits remarkable performances and serves as a dextrous arm for performing various tasks. Accordingly, it is an interesting bioinspiration for designing new manipulators with enhanced performances. This paper proposes a preliminary bird neck model using several stacked tensegrity crossed bar mechanisms. It addresses several issues regarding kinetostatic and dynamic modelling, design and control.

Analyse du besoin en assistance robotique dans la chirurgie de l'oreille

Abstract: Otologic surgery has some specificities compared to others surgeries. The anatomic working space is small, with various anatomical structures to preserve, like ossicles or facial nerve. This requires the use of microscope or endoscope. The microscope let the surgeon use both hands, but allows only direct vision. The endoscope leaves only one hand to the surgeon to use his tools, but provides a "fish-eye" vision. The rise of endoscopy these past few years has led to the development of numerous devices for the surgeon: the Robotol, first otological robot designed to performed some movements and hold an endoscope, or the Endofix Exo. Both devices need the hand of the surgeon to be moved. No robotic device allows the endoscope to be directed autonomously while the surgeon keeps both hands free to work, just like when he is working with a microscope. The objective of our work is to define the specific needs of the otological assistance surgery.

NAVARO II, a Novel Scissor-Based Planar Parallel Robot 1

Abstract: This article presents a new variable actuation mechanism based on the 3-RPR parallel robot. This mechanismis an evolution of the NaVARo robot, a 3-RRR parallel robot, for which the second revolute joint of the threelegs is replaced by a scissor to obtain a larger working space and avoid the use of parallelograms to operate thesecond revolute joint. To obtain better spatial rigidity, the leg mechanism is constructed by placing the scissorsin an orthogonal plane to the plane of the manipulator displacement (3-RRR or even the 3-RPR). This geometricproperty brings the significant consequence of allowing the scissors to directly substitute the prismatic chains in the3-RPR and enjoy the same kinematics advantages for the overall robots as only one solution to the inverse kinematicmodel. From the Jacobian expression, surfaces of singularity can be calculated and presented in a compact form.The singularity equations are presented for a robot with a similar base and mobile platform. The properties of thescissors are then determined to have a prescribed regular workspace.

Dispositif d’aide à la chirurgie

Abstract: Un dispositif d’aide a la chirurgie (1) comporte des moyens pour deporter une rotation de premier type et une rotation de deuxieme type, un mecanisme de transmission (40a) d’une rotation de troisieme type, un mecanisme de transformation (40b) de la rotation de troisieme type en une translation et un element elastique (41) relie a une extremite au mecanisme de transmission (40a) de la rotation de troisieme type. Le mecanisme de transmission (40a) de la rotation de troisieme type est relie a un moteur rotatif, la rotation du moteur rotatif dans un premier sens provoquant l’abaissement d’un outil (5) et une elongation de l’element elastique, la rotation du moteur rotatif dans un deuxieme sens provoquant l’elevation de l’outil (5) et une contraction de l’element elastique, et lorsque l’outil (5) est dans une position abaissee et que le moteur rotatif n’exerce aucun couple, l’element elastique (41) revient a une forme initiale provoquant l’elevation de l’outil (5). Figure a publier avec l’abrege : Fig. 1

Haptic control of the parallel robot Orthoglide

Abstract: Cet article traite de la conception d'une commande de retroaction haptique du robot parallele Ortho-glide pour effectuer des tâches de co-manipulation. Nous rappelons les differents modeles geometrique, cinematique et dynamique de Orthoglide. A partir de la mesure de la force d'interaction entre l'ope-rateur humain et l'effecteur final du robot, une trajectoire de reference de la plate-forme est calculee dans l'espace Cartesien. Cette trajectoire de reference est projetee dans l'espace articulaire pour ob-tenir la trajectoire de reference des variables actives de l'articulation lineaire. Un modele dynamique simplifie est propose et justifie pour concevoir une loi de commande de couple calculee des articula-tions lineaires actionnees dans l'espace articulaire. L'etude theorique et les resultats experimentaux sur Orthoglide montrent comment les robots industriels rigides classiques avec une bande passante en boucle fermee a vitesse et position elevees peuvent etre adaptes a des tâches de co-manipulation tres efficaces. Cet article offre des perspectives interessantes pour de nombreuses applications fondees sur l'interaction robot/humain dans un environnement industriel.

Automatic Mobility Analysis of Parallel Mechanisms: An Algorithm Approach Based on Position and Orientation Characteristic Equations

Abstract: The determination of the mobility of parallel mechanisms (PM) is a fundamental problem. An automatic and intelligent analysis platform will be a significant tool for the design and optimization of mechanical systems. Based on the theory of position and orientation characteristics (POC) equations, a systematic approach to computer-aided mobility analysis of PMs is presented in this paper. First, a digital model for topological structures which has a mapping relationship with position and orientation characteristics of mechanism is proposed. It describes not only the dimension of the motion output, but also gives the mapping relationship between the output characteristic and the axis of the kinematic joints. Secondly, algorithmic rules are established that convert the union and intersection operations of POC into the binary logical operations and the automatic analysis of POC are realized. Then, the algorithm of the automatic mobility analysis of PMs and its implementation with VC++ are written .The mobility and its properties (POC) will also be analyzed and displayed automatically after introducing by users of the data of topological structures representation. Finally, typical examples are provided to show the effectiveness of the software platform.