8 research outputs found
FASTKIT: A Mobile Cable-Driven Parallel Robot for Logistics
International audienceThe subject of this paper is about the design, modeling, control and performance evaluation of a low cost and versatile robotic solution for logistics. The robot under study, named FASTKIT, is obtained from a combination of mobile robots and a Cable-Driven Parallel Robot (CDPR). FASTKIT addresses an industrial need for fast picking and kitting operations in existing storage facilities while being easy to install, keeping existing infrastructures and covering large areas. The FASTKIT prototype consists of two mobile bases that carry the exit points of the CDPR. The system can navigate autonomously to the area of interest. Once the desired position is attained, the system deploys the CDPR in such a way that its workspace corresponds to the current task specification. The system calculates the required mobile base position from the desired workspace and ensures the controllability of the platform during the deployment. Once the system is successfully deployed, the set of stabilizers are used to ensure the prototype structural stability. Then the prototype gripper is moved accurately by the CDPR at high velocity over a large area by controlling the cable tension
Robot parallĂšle Ă cĂąbles simulant des contacts rigides
Le projet de recherche qui est présenté dans ce mémoire a été réalisé dans le cadre d'une maßtrise en génie mécanique. Le but de ces recherches était de réaliser un mécanisme haptique avec un robot à cùbles ayant la capacité de reproduire des contacts brusques et rigides durant une simulation en réalité virtuelle. Un simulateur de combat d'épée élémentaire a donc été construit pour servir de banc d'essai puisque ce genre de simulation nécessite ces genres de contacts. La majeure partie du projet était consacrée à l'élaboration des prototypes d'enrouleurs du mécanisme à cùbles. Ces enrouleurs ont été conçus pour créer des impacts en induisant la collision de deux petites piÚces métalliques. Les vibrations créées ainsi voyagent des enrouleurs vers l'utilisateur par l'entremise des cùbles et l'effecteur et donnent ainsi la sensation de frapper un objet rigide. Les mécanismes ainsi créés sont trÚs innovateurs et démontrent beaucoup de potentiel. Le fonctionnement de ces enrouleurs, ainsi que le processus de conception qui a mené à l'élaboration de ceux-ci est détaillé tout au long de ce mémoire. De plus, la performance de ces mécanismes est évaluée et il y a une liste de recommandations pour créer un prototype plus avancé
Low Mobility Cable Robot with Application to Robotic Warehousing
Cable-based robots consist of a rigid mobile platform connected via flexible links (cables, wires, tendons) to a surrounding static platform. The use of cables simplifies the mechanical structure and reduces the inertia, allowing the mobile platform to reach high motion acceleration in large workspaces. These attributes give, in principle, an advantage over conventional robots used for industrial applications, such as the pick and place of objects inside factories or similar exterior large workspaces. However, unique cable properties involve new theoretical and technical challenges: all cables must be in tension to avoid collapse of the mobile platform. In addition, positive tensions applied to cables may affect the overall stiffness, that is, cable stretch might result in unacceptable oscillations of the mobile platform.
Fully constrained cable-based robots can be distinguished from other types of cable-based robots because the motion and force generation of the mobile platform is accomplished by controlling both the cable lengths and the positive cable tensions. Fully constrained cable-based robots depend on actuator redundancy, that is, the addition of one or more actuated cables than end-effector degrees of freedom. Redundancy has proved to be beneficial to expand the workspace, remove some types of singularities, increase the overall stiffness, and support high payloads in several proposed cable-based robot designs. Nevertheless, this strategy demands the development of efficient controller designs for real-time applications.
This research deals with the design and control of a fully constrained cable-based parallel manipulator for large-scale high-speed warehousing applications. To accomplish the design of the robot, a well-ordered procedure to analyze the cable tensions, stiffness and workspace will be presented to obtain an optimum structure. Then, the control problem will be investigated to deal with the redundancy solution and all-positive cable tension condition. The proposed control method will be evaluated through simulation and experimentation in a prototype manufactured for testing
Ătude dâun systĂšme interactif sĂ©curitaire dĂ©diĂ© Ă lâinteraction humain-robot appliquĂ© Ă des mĂ©canismes parallĂšles entraĂźnĂ©s par des cĂąbles
Depuis l'introduction des premiers robots interactifs en industrie, qui Ă©taient Ă la base des systĂšmes collaboratifs supposĂ©s assister les humains dans les tĂąches pĂ©nibles et Ă©prouvantes physiquement, le domaine de lâinteraction humain-robot a fait des progrĂšs considĂ©rables. Actuellement, les robots et les humains peuvent coexister conjointement dans un espace hybride afin de partager des tĂąches de production ou de partager le temps dans lâexĂ©cution dâune activitĂ©. Cependant, les nouveaux besoins industriels doivent conduire Ă des recherches pour adapter les chaĂźnes de production et les rendre plus flexible et rĂ©active Ă la modification des caractĂ©ristiques des produits. Lâune des solutions consiste Ă adapter le manipulateur industriel prĂ©sent dans les lignes de production Ă des fins dâinteraction et de collaboration. Toutefois, la prĂ©sence de lâhumain dans lâespace de travail dâun manipulateur (cellule de travail hybride) reprĂ©sente un rĂ©el dĂ©fi dans le domaine de lâinteraction humain-robot puisque cela consiste Ă lâintĂ©gration dâune multitude de variĂ©tĂ©s de capteurs dits intelligents, surtout dans le cas de lâutilisation dâun mĂ©canisme parallĂšle entraĂźnĂ© par des cĂąbles. Pour cette raison, plusieurs problĂ©matiques ont Ă©tĂ© soulevĂ©es, pour lesquelles peu ou pas de recherches sont rĂ©alisĂ©es : cette nouvelle technologie est introduite sans entraĂźnement de lâopĂ©rateur, lâĂ©valuation de la sĂ©curitĂ© a Ă©tĂ© trĂšs peu explorĂ©e lors de lâinteraction et la performance de son utilisation demeure peu Ă©valuĂ©e dans un contexte de rĂ©duction des troubles musculosquelettiques (TMS). Le projet de recherche vise lâĂ©tude et la conception dâun systĂšme interactif permettant dâamĂ©liorer la sĂ©curitĂ© et lâintuitivitĂ© des personnes qui interagissent avec des mĂ©canismes parallĂšles entraĂźnĂ©s par des cĂąbles. Deux modes dâinteraction sont Ă©tudiĂ©s dans le systĂšme interactif, Ă savoir le partage des activitĂ©s et lâinteraction physique. En premier lieu, une mĂ©thode de gĂ©nĂ©ration de trajectoires avec Ă©vitement de collisions appliquĂ©e pour le mode de partage des activitĂ©s est proposĂ©e. Lâeffecteur du manipulateur suit un chemin dans lâespace opĂ©rationnel Ă travers des points de passage. Ces derniers sont gĂ©nĂ©rĂ©s par un rĂ©seau de neurones rĂ©tropropagation (Back-propagation), et sont reliĂ©s par un polynĂŽme quintique (de degrĂ© cinq). En outre, la gĂ©omĂ©trie dĂ©formable de lâobstacle et lâenvironnement dynamique sont pris en compte dans la mĂ©thode. En second lieu, une approche est abordĂ©e pour dĂ©terminer la distance minimale entre les cĂąbles et identifier ceux qui sont en interfĂ©rence. Le calcul de distance est exĂ©cutĂ© en temps rĂ©el Ă travers un algorithme. En outre, les contraintes physiques des cĂąbles ont Ă©tĂ© prises en compte dans la modĂ©lisation mathĂ©matique et formulĂ©es en un problĂšme dâoptimisation non linĂ©aire. Ce dernier est rĂ©solu en utilisant lâapproche de Karush-Kuhn-Tucker (KKT). Cette mĂ©thode de calcul de distance est intĂ©grĂ©e Ă une loi de commande interactive permettant de gĂ©rer les cĂąbles en interfĂ©rence pendant lâinteraction physique avec le mĂ©canisme. Une force est calculĂ©e et introduite dans la boucle de la commande afin dâĂ©viter le croisement et le relĂąchement des cĂąbles en interfĂ©rence. Par ce fait, la tĂąche est exĂ©cutĂ©e jusquâaux limites des possibilitĂ©s gĂ©omĂ©triques et cinĂ©matiques du mĂ©canisme. Par ailleurs, cette stratĂ©gie est basĂ©e sur une commande en admittance pour permettre lâinteraction physiquement avec un mĂ©canisme parallĂšle entrainĂ© par des cĂąbles. Un algorithme permettant de sĂ©lectionner entre ces deux modes est proposĂ©. Cette approche inclut un vĂȘtement intelligent pour le changement de mode de maniĂšre intuitive simple et rapide. Lâalgorithme est exĂ©cutĂ© en temps rĂ©el et basĂ© sur une identification de gestes utilisant un polynĂŽme dâinterpolation trigonomĂ©trique. Les signaux analysĂ©s proviennent dâune semelle instrumentĂ©e qui est situĂ©e au niveau du pied. Enfin, les diffĂ©rents algorithmes et stratĂ©gies sont validĂ©s en simulations et Ă travers des expĂ©rimentations sur un mĂ©canisme parallĂšle entrainĂ© par sept cĂąbles. Ce projet de thĂšse apporte plusieurs contributions dans le domaine de lâinteraction humain-robot notamment la capacitĂ© dâadaptation du systĂšme interactif pour des tĂąches industrielles.
Since the introduction of the first interactive robots in industry, which was the collaborative robots (labelled as COBOT), the field of human robot interaction has made considerable progress. In its early version, those robots were used to increase muscle strength of the operator for moving heavy loads. Recently, robots and humans can share the same workspace, production activities or working time. However, new needs in industry require more flexibility and reactivity supporting fast changes in product characteristics. One solution consists in the adaptation of an industrial robot, that is already installed in the production line, for interaction and collaboration purposes such as kinetic learning assembly task, and adaptive third hand. However, the presence of the human in the manipulatorsâ workspace (hybrid work cell) represents a real challenge in the field of human-robot interaction. It consists in the integration of an intelligent sensor varieties, especially when the cables driven parallel mechanisms (CDPM) are used for an interaction task. For these reasons, several issues have been raised, for which few or no research has been done yet. This new technology is introduced without any operators training and the safety assessment has been very little explored during the interaction. Moreover, the performance of its use remains poorly evaluated in a context of reduction of musculoskeletal disorders (MSDs). The research project aims to study and design an interactive system in order to improve the safety and the intuitivity when the humans interact with cables driven parallel mechanisms. Two modes of cooperation are studied in the interactive system, namely the sharing of activities and the physical interaction. First, a trajectory generating method for an industrial manipulator in a shared workspace is proposed. A neural network using a supervised learning is applied to create the waypoints required for dynamic obstacles avoidance. These points are linked with a quintic polynomial function for smooth motion which is optimized using least-square to compute an optimal trajectory. Moreover, the evaluation of human motion forms has been taken into consideration in the proposed strategy. Second, a mathematical approach is presented to determine the minimum distance between cables and to identify which ones are interfering. To execute this approach in real time, an algorithm is also presented for calculating this distance. Furthermore, the physical constraints of the cables have been considered in mathematical modeling and formulated into a nonlinear optimization problem. The latter is solved using the Karush-Kuhn-Tucker (KKT) approach. This method of distance calculation is integrated with a new interactive control that eliminates the computation of the effect of a folding interfered cable. A control strategy is proposed, which allows to manage the cables in interference while the operator physically interacts with the mechanism. A repulsive force is generated and introduced to the controller to avoid the cables crossing and folding. Therefore, the task is executed within the limits of the kinematic possibilities. Moreover, this strategy is based on an admittance control for physically interacting with a CDPM. In order to allow a change of intuitive interaction mode, an algorithm for selecting between these two modes is proposed. This approach includes an instrumented insole placed into a shoe for intuitive mode change quick and easy. The algorithm is executed in real time and based on a gesture identification using a trigonometric interpolation polynomial. Finally, theses different strategies and algorithms are validated in simulations and through experiments on a parallel mechanism driven by seven cables. This thesis project brings several contributions in the field of human-robot interaction including the ability of the interactive system to adapt for industrial tasks
Développement et analyse de mécanismes de tenségrité
Tableau d'honneur de la FacultĂ© des Ă©tudes supĂ©rieures et postdoctorales, 2006-2007Un systĂšme de tensĂ©gritĂ© correspond Ă un assemblage de composants qui sont chargĂ©s de maniĂšre axiale. Ce faisant, des cĂąbles ou des ressorts peuvent ĂȘtre utilisĂ©s pour les composants en tension ce qui rĂ©duit la masse et lâinertie du systĂšme. Par consĂ©quent, des mĂ©canismes de tensĂ©gritĂ© sont introduits dans cette thĂšse comme des alternatives aux mĂ©canismes plus conventionnels pour certains types dâapplication. Les objectifs principaux de la thĂšse sont le dĂ©veloppement et lâanalyse de nouveaux mĂ©canismes. La nĂ©cessitĂ© pour les mĂ©canismes de tensĂ©gritĂ© de toujours se retrouver dans des configurations oĂč leurs cĂąbles et leurs ressorts sont soumis Ă des forces de tension complique passablement leur dĂ©veloppement. Par consĂ©quent, une approche novatrice fondĂ©e sur lâutilisation de ressorts est proposĂ©e pour surmonter cette difficultĂ©. Pour faciliter lâutilisation de cette approche, des rĂšgles qui sâappliquent Ă la quantitĂ© de ressorts utilisĂ©e dans une architecture sont prĂ©sentĂ©es. Ă partir de ces rĂšgles et en sâinspirant de systĂšmes de tensĂ©gritĂ© existants, deux mĂ©canismes plans, trois mĂ©canismes spatiaux et deux mĂ©canismes modulaires sont dĂ©veloppĂ©s. Chaque mĂ©canisme est modĂ©lisĂ© dans le but dâanalyser sa cinĂ©matique, sa statique et sa dynamique. Ătant donnĂ© la prĂ©sence de degrĂ©s de libertĂ© non contraints dans les architectures des mĂ©canismes, les relations entre leurs variables dâentrĂ©e et de sortie dĂ©pendent des chargements externes, gravitationnels et inertiels qui leur sont appliquĂ©s. En supposant un rĂ©gime quasi-statique, de telles relations peuvent ĂȘtre calculĂ©es avec une approche numĂ©rique. Toutefois, pour le cas spĂ©cifique oĂč les mĂ©canismes ne sont pas soumis Ă des chargements, des solutions analytiques sont trouvĂ©es. Ces solutions sont ensuite exploitĂ©es dans le calcul des frontiĂšres des espaces atteignables des mĂ©canismes. Les degrĂ©s de libertĂ© non contraints des mĂ©canismes de tensĂ©gritĂ© leur permettent de se dĂ©former sous lâapplication de chargements externes. Une attention particuliĂšre est alors portĂ©e au calcul de la raideur des mĂ©canismes ainsi que des limites des chargements pouvant ĂȘtre rĂ©sistĂ©s sans perte de stabilitĂ© ou de tension dans les cĂąbles. Des observations sont Ă©galement faites concernant lâamortissement des vibrations des mĂ©canismes dans les directions des degrĂ©s de libertĂ© non contraints.A tensegrity system corresponds to an assembly of components that are subjected only to axial loads. As a consequence, cables or springs can be used for the tensile components thus considerably reducing the mass and inertia of the system. With the goal of benefiting from these interesting properties, this thesis introduces tensegrity mechanisms as alternatives to more conventional type mechanisms for certain types of applications. The main objectives of the thesis are the development and analysis of novel mechanisms. The need for tensegrity mechanisms to remain in configurations where their cables and springs are subjected to tensile loads complicates their development signi- ficantly. Consequently, a new approach based on the use of springs is proposed to overcome this difficulty. In order to facilitate the use of this approach, certain rules pertaining to the quantity of springs used in a given architecture are formulated. Based on these rules, two planar mechanisms, three spatial mechanisms and two modular mechanisms are developed using existing tensegrity systems. Each new mechanism is modeled with the goal of analyzing its kinematics, statics and dynamics. Due to the presence of unconstrained degrees of freedom in the mechanismsâ architectures, relations between their input and output variables are influenced by any external, gravitational or inertial loads that might be acting. By assuming a quasi-static regime, such relations can be computed using a numerical approach. However, for the specific case where the mechanisms are not subjected to any loads, analytical solutions are found. These solutions are then exploited in order to compute the boundaries to the mechanismsâ workspaces. The mechanismsâ unconstrained degrees of freedom allow them to deform under the application of external loads. Special attention is thus given to the stiffness of the mechanisms as well as the limits of the external loads that they may resist without losing their stability or the tension in their cables. Observations are also made regarding the damping of the mechanismsâ vibrations along the unconstrained degrees of freedom