Toward Novel Grasping of Nonrigid Materials Through Robotic End-Effector Reorientation

While manipulation of rigid objects in the context of automated manufacturing has been well studied, there are few examples in the literature on how to handle the manipulation of nonrigid objects. One of the fundamental control challenges in manipulating nonrigid objects (e.g., films and fabrics) centers on the fact that the object inherently deforms during grasping and the object's center of mass also changes during manipulation. While pneumatic grippers are typically used in manufacturing applications for nonrigid objects today, their use remains fundamentally limited to planar manipulation due to the aforementioned challenges. In this article, we introduce a new approach for manipulating nonrigid objects by leveraging the effects of friction, reorientation, and a novel pneumatic gripper. We show that holding force increases with an increase in the orientation angle due to both reduction of depressurization within the suction cup, as well as the ability to leverage friction forces between the object and the gripper. The additional frictional forces present at the 90
$^{\circ }$
case are also determined theoretically and experimentally for various films and fabrics. The paper further demonstrates the effectiveness of using reorientation up to an angle of 90
$^{\circ }$
degrees during manipulation of nonrigid materials in the vertical direction. This article is the first step towards future work in real-time robotic controlled reorientation of nonrigid objects during dexterous manipulation.