Torque minimization of the Delta parallel robot

International audienceThis paper proposes a new solution to the problem of torque minimization of the Delta robot. The suggested approach involves connecting to the initial structure a secondary mechanical system, which generates a vertical force applied to the platform of the robot. The conditions for optimization are formulated by the minimization of the root-mean-square and maximum values of the input torque due to the static and dynamic loads. The numerical examples show the efficiency of the suggested torque minimization approach

Contribution to the Improvement of the Medical Device SurgiScope

International audienceThis paper proposes a new solution to the problem of torque minimization of the medical device SurgiScope ® by connecting to the initial structure a secondary mechanical system, which generates a vertical constant force on the platform of the robotized device. The conditions for optimization are formulated by the minimization of the root-mean-square values of the input torques of the studied device. The positioning errors of the unbalanced and balanced robots are provided. A significant reduction of these errors is achieved by using the suggested balancing mechanism. The efficiency of the developed approach is illustrated by numerical simulations

Design and Prototyping of a New Balancing Mechanism for Spatial Parallel Manipulators

International audienceThis paper proposes a new solution to the problem of torque minimization of spatial parallel manipulators. The suggested approach involves connecting a secondary mechanical system to the initial structure, which generates a vertical force applied to the manipulator platform. Two versions of the added force are considered: constant and variable. The conditions for optimization are formulated by the minimization of the root-mean-square values of the input torques. The positioning errors of the unbalanced and balanced parallel manipulators are provided. It is shown that the elastic deformations of the manipulator structure which are due to the payload, change the altitude and the inclination of the platform. A significant reduction of these errors is achieved by using the balancing mechanism. The efficiency of the suggested solution is illustrated by numerical simulations and experimental verifications. The prototype of the suggested balancing mechanism for the Delta robot is also presented

AIR2, un robot parallèle à actionnement pneumatique à deux degrés de liberté pour les applications de prise et dépose d'objets

Un prototype de robot parallèle actionné pneumatiquement à deux degrés de liberté a été développé afin de rendre accessible aux petites et moyennes entreprises la robotisation de tâches qui nécessiteraient le déplacement de charges de 5 à 25 kg en utilisant des vérins standards moins onéreux que les moteurs électriques. Après une présentation de la structure mécanique du robot ainsi que ses modèles, la stratégie de commande innovante (commande prédictive avec boucle interne de force H-infini) est brièvement introduite, puis les résultats obtenus expérimentalement sont présentés et analysés

Modèle simplifié de câble pesant élastique : Application aux robots parallèles à câbles

L'étude des robots à câbles de grande dimension nécessite l'utilisation d'un modèle de câble pesant élastique. Un modèle connu de caténaire élastique permet de tenir compte de ces caractéristiques, mais la forte non-linéarité des équations le régissant rend son étude très complexe. Cet article présente un modèle statique simplifié de câble pesant élastique qui s'exprime sous forme linéaire. Sous l'hypothèse d'une faible déflection du câble, il permet de se rapprocher fortement du comportement réel d'un câble. Une étude d'erreurs sur 2 exemples de robots à câbles est également présentée

Kinematic and Dynamic Decoupling Methods of Parallel Manipulators

International audienc

On the Static Workspace of Large Dimension Cable-Suspended Robots with Non Negligible Cable Mass

International audienceIn most studies on parallel cable-driven robots, cables are supposed to be massless and inextensible. However, in the case of large dimension robots, cable mass and elasticity cannot be neglected anymore. Based on a well-known cable static model which takes these characteristics into account, the formulation of the inverse kinematics of n cable/n-DOF cable-driven robots is presented. The consequences of this modeling on the usual static workspace definition is then discussed. Notably, as the tension in a cable is not constant, the maximal tension along the cable has to be found. An example of a planar 3 cable/3-DOF robot is used to highlight that, in some particular poses, the mobile platform can be in static equilibrium while some cables are hanging below the platform. Finally, new limiting factors for the definition of the static workspace are introduced and applied to the same planar robot example which shows the significance of taking into account cable mass and elasticity

A mixed GPC-H∞ robust cascade position-pressure control strategy for electropneumatic cylinders

Abstract-A robust cascade strategy combining an outer position predictive control loop and an inner H∞ pressure control loop is proposed and tested on an electropneumatic testbed for parallel robotic applications. Two types of cylinders are tested, the standard double acting cylinder and the rodless one. A position/pressure difference (or force) strategy is developed and implemented. As the behavior of the nonlinear cylinders is nonlinear, a feedback linearization strategy is adopted. A Generalized Predictive Controller (GPC) is synthesized for the position outer loop and a constrained LMI based H∞ controller is synthesized for the pressure inner loop. Experimental results show the feasibility of the control strategies and good performances in terms of robustness and dynamic tracking