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.