Tactile feedback in textile mannipulation

VON DRIGALSKI FELIX WOLF HANS ERICH (1561010)


ract Tactile information is an attractive sensing modality, as it yields information about the contact that is otherwise inaccessible, depends neither on lighting conditions nor line of sight, and is computationally lighter than camera data. To make use of it during the robotic manipulation of textiles, in this work I investigate the sensing requirements, propose a suitable sensor, a gripper prototype and a method to extract tactile information, and finally showcase it in an application. First, I investigate the deformation of the human fingertip while it is under load using stereo cameras and a 6D force plate. By measuring the force as well as the deformation of the fingertip’s lateral surface, I relate the curvature of the fingertip surface to the force acting on the fingertip. Second, I propose 1) an open-source gripper with a sensor that utilizes the deformation of a rubber half-dome to determine the normal and shear force acting on the fingertip and 2) a rubbing motion implemented on this gripper, which extracts information about the textile that is being grasped. I show that the data obtained by this exploratory motion allows not only the identification of previously trained textiles, but also to distinguish between a single and multiple layers of them, and propose a method to perform this classification. Furthermore, I show that by varying the speed and force of the exploratory motion, different information is obtained, and that this can be used to increase the accuracy of the identification. To show the usefulness of the proposed method, I use the proposed open-source gripper and exploratory motion, as well as computer vision algorithms and human tools, to fold shirts with a humanoid robot. I show that the use of haptic feedback as well as the use of human tools significantly reduce the time required to complete the folding task. In summary, the proposed methods and gripper contribute a novel way to a) identify different textiles and distinguish between a single and multiple layers of them, b) manipulate textiles with a serial manipulator and c) complete the task of laundry folding with a humanoid robot. The code and mechanical designs used in this work are open source and available for download.