Tactile manipulation with a TacThumb integrated on the Open-Hand M2 gripper

Tactile manipulation will be essential for automating industrial and service tasks currently done by humans. However, the application of tactile feedback to dexterous manipulation remains a challenging unsolved problem, with robot capabilities lagging far behind those of humans. Here we present the TacThumb (Tactile Thumb): a cheap, robust, 3d-printed optical tactile sensor integrated on the Yale GrabLab model M2 gripper. To test tactile manipulation capabilities, a cylinder is rolled along the TacThumb using the opposing non-tactile finger. The tactile information permits localization of the test cylinder along the TacThumb to sub-millimetre accuracy over most of the movement range. In consequence, the M2 gripper can perform accurate in-hand tactile manipulation, by providing information that can be used to control the location of the test object within the hand. Tactile manipulation is demonstrated by rolling cylinders with a range of diameters up and down the TacThumb along a target trajectory, using only tactile data to update its current position and move it towards a target. This model-free approach gives a demonstration of basic tactile manipulation without the need for a kinematic model of the hand, in a manner that should generalize to other tactile manipulation tasks.