TacRot: A Parallel-Jaw Gripper with Rotatable Tactile Sensors for In-Hand Manipulation

Abstract

Finger dexterity and tactile perception are key capabilities for humans to manipulate objects within hand, as well as robots. Inspired by the thumb-forefinger dexterous manipulative movement, we devised a novel robotic finger with an active rotational tactile sensor (i.e. TacRot), and mounted the finger on a parallel-jaw gripper. By processing the high-resolution images of the vision-based tactile sensor, we achieved depth reconstruction of the surface and localization of the contact area. To improve gripping flexibility and stability, we applied a self-adaptive grasping strategy with real-time contact detection feedback, which performed 94% success rate in experiment. Based on the rotational actuator at the fingertip, we proposed two in-hand manipulation primitives: (1) pivot: fingertips co-rotating for object reorientation; (2) twist: fingertips contra-rotating for object spin. The primitives are theoretically analyzed and experimentally verified in two practical tasks: pivoting a paper cup under vertical constraints and twisting a screw with spin angle estimation. Our design and experiments demonstrate a feasible way to enhance the active tactile manipulation ability for common parallel-jaw grippers.