Etude et conception d’un préhenseur versatile sous-actionné : application dans la préparationde commandes de détail

摘要

The objective of this thesis is to propose a practical solution to the autonomous picking of objects with various geometries. This study takes place in an industrial context defined by the Intelpick project aiming to robotize the process of retail orders preparation, and meets specific constraints such as a short cycle time among others. Thus, this dissertation focuses on the study of grippers whose gripping execution is fast and also whose grasp planning can be achieved by simple and fast algorithms. This dual objective can be fulfilled using underactuated robotic hands. Indeed, the concept of underactuation in grasping can be used as a strategy to reduce the number of actuators and sensors while keeping the ability of the hand to mechanically adapt to the shape of the object. However, this type of gripper is subject to peculiar and unstable behaviours such as the ejection phenomenon. Due to the lack of criteria suitable for the stability analysis of a grasp exerted by an underactuated hand, we extend both properties of form closure and force closure to this particular case. Thus, we present a method for the analysis of 1st order form closure, a method for the analysis of higher order form closure and a necessary condition for force closure. These works allow us to highlight the relevance of unidirectional mechanisms in improving the capability of the hand to produce stable grasps and vanishing the ejection phenomenon. Finally, the results of these works are put into practice in the design of two adaptive robotic hands TWIX and Octopus.