D-PALI: A Low-Cost Open Source Robotic Gripper Platform for Planar In-Hand-Manipulation

Robot grippers are widely used in industrial automation for pick-and-place tasks on a variety of objects. Whilst the majority of commercial grippers are capable of establishing stable grasps, few can perform in-hand-manipulation (IHM). IHM is has the potential to increase robotic motion efficiency, yet most IHM-capable manipulation platforms are anthropomorphic in nature and cost over $10,000, posing a barrier to entry for many. In this work we propose a IHM capable gripper platform that is open-source and may be assembled for £150 ($162) and access to a 3D printer. The gripper consists of two fully actuated 2DOF fingers, each of which is based on a five-bar linkage mechanism with one link extended. The fingers are modular, allowing the gripper to be easily expanded into 3+ finger configurations via simple modification of the central mount. We define the inverse kinematics and effective workspace of the gripper (via the use of Freudenstein equations), providing guidance for translation and rotation of gripped objects. We demonstrate the gripper's ability to manipulate a 1-inch cube's pose within a ±5% error margin and rotate various other YCB objects via open-loop position control.