Kinematic Design and Description of Industrial Robotic Chains

Generally speaking, the problem of synthesis of mechanism can be broken down into three sub problems: i) the specification of the problem, ii) the topological synthesis of the mechanism and iii) the dimensional synthesis. This chapter relates in particular to the second sub problem. The chapter could be useful for teachers, researchers, engineers and students who are confronted with the various types of problems concerning the choice of kinematic chains in the initial phase of the topological structural design of an industrial robot. The principal goal of the chapter is to present an overview concerning the chronology of the design of the kinematic chain of an industrial robot. It starts with a review of the methods of synthesis of mechanisms provided by the MMT; then it deals with their representation, validation and concludes with the application of these mechanisms in the initial design phase of industrial robots. The chapter begins with the presentation of a new method for structural synthesis of planar link chains in robotics. It is based on the notion of logical equations. After a brief reminder of the theory of Modular Structural Groups (MSG), and of the connectivity and mobility laws of MMT, various levels of abstraction are studied concerning the complexity of the structure. This permits the synthesis of planar chains with various degrees of complexity expressed by the number of links, joints and the degree of mobility. The logical equations allow the association of MSGs of type A and closed chains of type G. The rules for associations of groups are also presented. The aim is to execute all the possible combinations to join or transform the links in order to obtain as many structures as possible by avoiding those, which are isomorphic. The association of two groups allows the elaboration of different closed chains of upper level. However there are some defect structures, which do not respect the connectivity and mobility laws. Therefore great care has been taken to avoid them. The problem of degenerated structures is central in the synthesis of structures. It concerns especially chains with two and more degrees of mobility. The problem of defect, degeneration and isomorphism is then approached. Finally, a method for description of chains by contours and molecules is proposed. It enables the reduction of the number of the topological structures of the robots concerning the position of the frame and the end-effector of the robot by comparing their respective molecules. This method is then applied for the description of the structures thus obtained (logical equations approach) and for the description of the topology of the principal structure of the industrial robots in the initial phase of their design

Une méthode d'aide au choix topologique des actionneurs des mécanismes cinématiques en robotique

Plusieurs méthodes d'aide à la conception et par la suite d'optimisation ont déjà été présentées concernant l'optimisation dimensionnelle en robotique, mais peu sur l'optimisation topologique et par conséquent sur la conception topologique. Dans ce travail nous proposons une nouvelle méthode pour un choix morphologique restreint de mécanismes moteurs plans en robotique. Elle est basée sur la notion de symétrie des structures concernant la position de l'actionneur du robot en fonction de la position du bâtit de celui-ci. Différents cas de combinaisons de couples de mécanismes symétriques sont détectés. Ainsi le nombre de configurations possibles est restreint par élimination de celles qui sont symétriques. Des formulations pour calculer le nombre de possibilités d'ancrer un actionneur sont présentées. Elles permettent de réduire le nombre de structures tout en évitant celles qui sont isomorphes. Différents exemples d'application, pour des structures à différents degrés de liberté, sont présentés permettant de restreindre le champ de recherche parmi les solutions possibles

Contact identification for assembly-disassembly simulation with a haptic device

Assembly/Disassembly (A/D) simulations using haptic devices are facing difficulties while simulating insertion/extraction operations such as removing cylinders from holes. In order to address this configuration as well as others, an approach based on contact identification between components is presented in this paper. This approach can efficiently contribute either to a new A/D simulation preparation process relying on two types of shape representations (mesh and CAD NURBS models), or directly to the real time simulation process when it is performed with 6D haptic devices. The model processing pipeline is described and illustrated to show how information can be propagated and used for contact detection. Then, the contact identification process is introduced and illustrated through an exampl

Modélisation des trajectoires d'assemblage et de désassemblage associées aux liaisons fonctionnelles de produits

La modélisation des opérations de désassemblage fait intervenir de multiples données (géométriques, cinématiques, technologiques, ...) et nécessite de passer par une étape d'analyse des liaisons cinématiques entre composants au cours des différentes étapes de montage/démontage. Dans ce contexte, le but principal abordé ici est le développement d'un nouveau modèle capable de représenter tous les déplacements autorisés pour chaque couple de surfaces d'une liaison mécanique. Les différentes combinaisons possibles des contacts élémentaires sont étudiées afin de proposer un modèle général. Cette modèle est utilisé pour la simulation des opérations cinématiques nécessaires à l'assemblage et au désassemblage des produits lors du processus de production, des opérations de maintenance et en fin de cycle de vie. Un outil informatique, opérationnel sur OPEN CASCADE, est également proposé et présenté permettant de capter le type des contacts entre deux composants d'un ensemble mécanique

Disassembly Task Evaluation in Virtual Reality Environment

International audienceThe influence of virtual reality (VR) on human behavior with using biomechanical analysis methods and its application for assembly/disassembly operations simulation is presented in this paper. A new haptic model for mechanical energy expenditure is proposed where the required mechanical work is used as main parameter. The fatigue levels are evaluated by analyzing the recorded electromyography (EMG) signals on the most involved muscles of operator’s arm. A set of experimental disassembly tests realized in a VR environment are performed thus allowing to validate the proposed method. The comparison of the analytical and experimental results has shown good correlation between them. The proposed method provides the feasibility to integrate human muscle fatigue into disassembly sequence evaluation via mechanical energy expenditure when performing disassembly operation simulations in the initial stage of product design

Disassembly task evaluation by muscle fatigue estimation in a virtual reality environment

International audienceToday, disassembly operations play a very important role during the initial design phase of industrial products considering the role played by these operations throughout the product life cycle. Current simulation platforms do not offer the necessary information and versatility required for a complete disassembly process simulation, including human/operator physiological data management. The paper deals with a new method for disassembly sequence evaluation. It is based on metabolic energy expenditure and muscle fatigue estimation. For this purpose, the analytical model for mechanical energy expenditure is proposed. In this model, the required mechanical work is used as a parameter that allows comparing the relationships among fatigue levels when performing disassembly sequences. Then, the fatigue levels are evaluated by analyzing the recorded electromyography signal on an operator’s arm. The proposed method is validated by a set of experimental disassembly tests performed in a virtual reality environment. The comparison of the analytical and experimental results has shown good correlation between them. The main result of this study is the proposed model for assessing muscle fatigue and its validation by experimental procedure. The proposed method provides the feasibility to integrate human muscle fatigue into disassembly sequence evaluation via mechanical energy expenditure when performing disassembly operation simulations

L'analyse combinatoire pour l'énumération topologique des mécanismes cinématiques en robotique

Une nouvelle méthode d'énumération morphologique restreinte de mécanismes moteurs plans en robotique est présentée. Basée sur la notion de symétrie des graphes cinématiques et inverses, elle concerne la position de l'effecteur et des actionneurs du robot en fonction de la position du bâti de celui-ci. La méthode est associée à la théorie des graphes et analyse combinatoire. Différents cas de combinaisons de couples de mécanismes symétriques sont détectés. Ainsi, le nombre de configurations possibles est restreint par élimination de celles qui sont isomorphes

On Wire-driven Parallel Suspension Systems for Static and Dynamic Derivatives of Aircraft in Low-speed Wind Tunnels

为了用同一套绳牵引并联支撑系统来实现低速风洞静导数和动导数实验,采用理论与实验相结合的方法,总结了在WdPSS-8项目中所做的研究工作。结果表明,传统的杆支撑系统存在如支架对空气流场的影响等不可避免的缺陷;张线支撑系统很适合用于飞行器的静导数实验中,但它不能用在飞行器的动导数实验中;绳牵引并联支撑系统WdPSS-8能成功用于静导数实验中,且它在动导数实验中有潜在用途。WdPSS-8项目中的理论问题都得到解决,但实验方面还有不少问题有待解决。In order to use the same wire-driven parallel suspension system to implement static and dynamic derivative experiments in low-speed wind tunnels,a survey of the research work addressing the wire-driven parallel suspension system with eight wires(WDPSS-8) projects is presented in this article.The research methodology combines both theoretical and experimental aspects.The results show that,there are some unavoidable drawbacks,such as the interference of the streamline flow brought by the strut in the traditional suspension system.Moreover,cable-mounted systems are suitable for experiments of the static derivatives of the aircraft;however,they cannot be used in the experiments of dynamic derivatives;WDPSS-8 can be successfully used in experiments of static derivatives,and it has the potentiality to be used in experiments of dynamic derivatives.The issues in the theoretical aspect have been addressed.However,much work has to be done in the experimental aspects.国家自然科学基金(50475099);福建省青年科技人才创新基金(2006F3083

Analysis of Inverse Kinematics and Dynamics of a Novel 6-Degree-of-freedom Wire-Driven Parallel Gantry Crane Robot

Every type of wire-driven parallel robots can be used in cargo handling as a robot crane. Concerning the 6-degree-of-freedom (DOF) wire-driven parallel robot with three wires, its mechanism configuration belongs to URPMs (Under Restrained Positioning Mechanisms), if one translational or rotational DOF rigid mechanism is added to each of its kinematic chains. In this case the mechanism becomes a new type 6-DOF robot. It has been found, in the research survey that the mechanism configuration of such kind of 6-DOF robot CABLEV is not powerful enough because of its limited workspace. A novel 6-DOF parallel crane robot containing three rigid-and-flexible hybrid sub-chains is proposed which can access to a larger workspace. The differential flatness of its inverse kinematics and dynamics is analyzed by a simulation. The results of this simulation will lay a basis for the future trajectory tracking control of the payload